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Fluid Pressure

http://www.grc.nasa.gov/WWW/K-12/airplane/pressure.html

An important property of any gas is its pressure. We have some experience with gas pressure that we don't have with properties like viscosity and compressibility. Every day we hear the TV meteorologist give value of the barometric pressure of the atmosphere (29.8 inches of mercury, for example). And most of us have blown up a balloon or used a pump to inflate a bicycle tire or a basketball.

Because understanding what pressure is and how it works is so fundamental to the understanding of aerodynamics, we are including several slides on gas pressure in the Beginner's Guide. An interactive atmosphere simulator allows you to study how static air pressure changes with altitude. The FoilSim program shows you how the pressure varies around a lifting wing, and the EngineSim program shows how the pressure changes through a turbine engine. Another simulator helps you study how pressure changes across shock waves that occur at high speeds. There are two ways to look at pressure: (1) the small scale action of individual air molecules or (2) the large scale action of a large number of molecules.

Molecular Definition of Pressure

From the kinetic theory of gases, a gas is composed of a large number of molecules that are very small relative to the distance between molecules. The molecules of a gas are in constant, random motion and frequently collide with each other and with the walls of any container. The molecules possess the physical properties of mass, momentum, and energy. The momentum of a single molecule is the product of its mass and velocity, while the kinetic energy is one half the mass times the square of the velocity. As the gas molecules collide with the walls of a container, as shown on the left of the figure, the molecules impart momentum to the walls, producing a force perpendicular to the wall. The sum of the forces of all the molecules striking the wall divided by the area of the wall is defined to be the pressure. The pressure of a gas is then a measure of the average linear momentum of the moving molecules of a gas. The pressure acts perpendicular (normal) to the wall; the tangential (shear) component of the force is related to the viscosity of the gas.

Scalar Quantity

Let us look at a static gas; one that does not appear to move or flow. While the gas as a whole does not appear to move, the individual molecules of the gas, which we cannot see, are in constant random motion. Because we are dealing with a nearly infinite number of molecules and because the motion of the individual molecules is random in every direction, we do not detect any motion. If we enclose the gas within a container, we detect a pressure in the gas from the molecules colliding with the walls of our container. We can put the walls of our container anywhere inside the gas, and the force per area (the pressure) is the same. We can shrink the size of our "container" down to an infinitely small point, and the pressure has a single value at that point. Therefore, pressure is a scalar quantity, not a vector quantity. It has a magnitude but no direction associated with it. Pressure acts in all directions at a point inside a gas. At the surface of a gas, the pressure force acts perpendicular to the surface.

If the gas as a whole is moving, the measured pressure is different in the direction of the motion. The ordered motion of the gas produces an ordered component of the momentum in the direction of the motion. We associate an additional pressure component, called dynamic pressure, with this fluid momentum. The pressure measured in the direction of the motion is called the total pressure and is equal to the sum of the static and dynamic pressureas described by Bernoulli's equation.

Macro Scale Definition of Pressure

Turning to the larger scale, the pressure is a state variable of a gas, like the temperature and the density. The change in pressure during any process is governed by the laws of thermodynamics. You can explore the effects of pressure on other gas variables at the animated gas lab. Although pressure itself is a scalar, we can define a pressure force to be equal to the pressure (force/area) times the surface area in a direction perpendicular to the surface. The pressure force is a vector quantity.

Pressure forces have some unique qualities as compared to gravitational or mechanical forces. In the figure shown above on the right, we have a red gas that is confined in a box. A mechanical force is applied to the top of the box. The pressure force within the box opposes the applied force according to Newton's third law of motion. The scalar pressure equals the external force divided by the area of the top of the box. Inside the gas, the pressure acts in all directions. So the pressure pushes on the bottom of the box and on the sides. This is different from simple solid mechanics. If the red gas were a solid, there would be no forces applied to the sides of the box; the applied force would be simply transmitted to the bottom. But in a gas, because the molecules are free to move about and collide with one another, a force applied in the vertical direction causes forces in the horizontal direction.


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Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
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Pressure forces have some unique qualities as compared to gravitational or mechanical forces. In the figure shown above on the right, we have a red gas that is confined in a box. A mechanical force is applied to the top of the box. The pressure force within the box opposes the applied force according to Newton's third law of motion. The scalar pressure equals the external force divided by the area of the top of the box. Inside the gas, the pressure acts in all directions. So the pressure pushes on the bottom of the box and on the sides. This is different from simple solid mechanics. If the red gas were a solid, there would be no forces applied to the sides of the box; the applied force would be simply transmitted to the bottom. But in a gas, because the molecules are free to move about and collide with one another, a force applied in the vertical direction causes forces in the horizontal direction.

The upper chamber of hhop gen 3 is defined as a hollow piston reservoir. As such it has rigid walls that are able to withstand internal hydrostatic operating pressure, without elastic deformation. (Pascal's Barrel)

https://en.wikipedia.org/wiki/Pascal's_barrel

If your piston bulges it will interfere with the housing wall clearance and cause friction drag on the piston. The piston being a solid will have a weight force vector quantity only.

The liquid water inside the hollow piston reservoir has both a weight vector and an internal pressure scalar. If the hydrostatic pressure equalisation valve sleeved through the hollow piston is closed, the scalar pressure fields in both chambers are prevented from equalising thus forming two separate fields.

The upper chamber has gravitational potential energy and acts as a weight force only, compressing the liquid chamber below it, energising the scalar field of the lower chamber.

The piston at bottom of travel has zero gravitational potential energy remaining, but it does have the scalar pressure in the secondary field.

The working fluid is pumped vertically and emerges at the turbine exhaust to atmospheric pressure, having done work on the water wheel alternator. It falls under gravity into the hollow piston reservoir and does work on the chamber below.

The piston itself can be buoyant, enough to overcome breakout friction of the piston seal, as the upper chamber is defined in the gravitational field only as a vector force. This means that a steadily increasing force (such as water pouring in) can overcome the negative buoyancy force and the piston will become heavy.

Opening the equalisation valve will allow hydrostatic equilibrium to occur and the piston will ascend as there is only one field of reference now.. the specific gravity field.


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Everyman Standing Order 01: In the Face of Tyranny; Everybody Stands, Nobody Runs.
Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
Everyman Standing Order 03: Everyman knows Timing is Critical in any Movement.
   

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hhop gen 4

No hho cell, the piston itself is set naturally buoyant, enough force to reliably raise it during the reset cycle.

The COP=1 ratio is now set to PMA output vs Power required to operate valve.

Gravity is the prime mover in both parts of the cycle, the valve switches between one gravitational frame of reference and another.
« Last Edit: 2015-11-19, 18:49:52 by evolvingape »


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hhop gen 2 Hybrid

Exploiting the buoyancy force differential between the two fluids, gas and liquid, to operate the valve.


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I came across this article today by Simon Derricutt, and I think it's conceptual approach is an excellent teaching tool.

I have reproduced it below (please see link for conceptual images referred to) and will comment in following posts:

Some energy basics

by Simon Derricutt | Nov 20, 2015

http://revolution-green.com/some-energy-basics/

In a lot of the FE blogs and claims you’ll see some “interesting” ideas about “where the energy comes from”. Some people of course avoid that little theoretical bit and purely say “this works” and “give me some money and I’ll show you a video of it”. Alternatively, they may say it worked when they did it before and if you give them some money they’ll build a bigger one that will solve all the world’s problems.

Of course, human languages tend to be circular in their definitions, since each word is defined in terms of others, and it’s only when we’re describing something solid, like a tree, that we can point at it and say “that’s what this word means”. There is thus some question of what we actually mean (or maybe what is understood) when we talk of mass, energy or suchlike where there isn’t something to actually point at. This is maybe worse when we talk about mass and energy, since they are the same thing in a different state.

We can start with the point that energy is the capacity to do work, but that means we also have to define work and also misses the point that when we do work we have the same amount of total energy at the end as when we started – that work is actually done in the course of movement of energy from one place to another and energy itself is neither created or destroyed in any process we know of. All too quickly the conversation gets tied into little knots and the original idea of pinning down where the energy comes from is diverted into needing to also say where it goes to.

I’ll assume that you can look up the terms in the wiki or elsewhere and get a grounding in the ideas of what mass and energy are, therefore. We know what mass is. In a gravitational field a mass has weight and if you use a certain force on it it will accelerate in the direction of the force. Convert that mass into energy (using the formula E=mc²) and instead of a small amount of mass you have a whole lot of energy. That conversion of a small amount of mass into energy powers everything we do. When we burn oil we convert a small amount of mass into the kinetic energy of heat, and so there is a small loss of our initial mass – almost too small a difference to actually measure but we can calculate it. Kinetic energy is energy of movement, and it thus is always moving. It makes sense that any potential energy of any type is actually stored as mass, too, so the spring under tension is just that little bit more mass than the relaxed spring and the weight you’ve just lifted above your head (thus adding gravitational potential energy) has thus also just a bit more mass than when it was on the floor.

We’ve thus reached the point where I can say kinetic energy is stored in movement and potential energy is stored in mass. I’ve also stated that work can only be done when energy moves from one place to another, so the only thing that can do work is kinetic energy.

If we place some kinetic energy into a box (see the starting state in the first picture), then it will move from where we put it. When we’re talking about heat in a gas, then the direction it moves in will be random. Sometimes it will go towards the centre, sometimes it will move away, but since there are far more directions that are away from the centre than directly towards it, after a bit of time t we’ll see this second picture, where although there is a bit more density around the centre area  the energy density is less and more diffuse. Pretty-well whatever type of energy we put into an open space, it will spread away from where it’s put in all directions open to it. In these pictures I haven’t put in any constraints except for the outer bounding box, but similar pictures could be produced for any actual situation by applying a bit of maths. Of course, if it’s actually photons we put in to the box instead of some hot air, the diffusion outwards would be a lot quicker.

A bit later on, the initial denser patch has almost gone away. I don’t think there’s much point in adding the final state of just a bit grey all over – if you haven’t seen where this heads by now there’s not much point in reading further.

Basically, when we’re dealing with particles such as air molecules, and the random distribution of collisions and energy transactions, the heat will spread out until there is no measurable difference between any two small sections of the entire space available to that energy. The heat will move from hotter to cooler, and that will always happen. This is the basis of the Second Law of Thermodynamics. Once we have reached the end-state and the energy-density is even, we will no longer be able to measure any differences in temperature and, if we need a temperature difference to get work done, we’re stuffed and no work is possible.

What’s really happening, though, when we’ve reached that point? Those air-molecules are bouncing around just as much as they did before. There is the same distribution of actual kinetic energy across the range whatever volume you care to look at. There is the same pressure, and we know that for a gas, pressure is the sum over a fairly-small (but not infinitesimal) time of the momentum-transfers of the colliding gas molecules. In short, not really a large difference from the way it was at the start with a nice concentrated lump of energy in the middle. If you took a very short time-slice over a small volume (say somewhere around 100ps and a cubic micron with air at STP) you actually wouldn’t be able to say what the temperature or pressure actually was. You might be able to make a rough stab at what it was, but you couldn’t actually be at all sure.

There is still energy moving around in this gas, but there is no longer any net energy movement when you use a reasonably-human scale of time and space. There’s a basic rule in that kinetic energy will tend to spread out so that the space available to it will be evenly filled at the same density, and this can be seen for any situation when the scale is such that it masks the statistical variations over time and space. There’s also the observation that potential energy in a system will tend to drop to the lowest level available. Water finds its own level, and atoms naturally exist in their ground states. These are things we see so often that we don’t really think about it that deeply, except as here where we’re asking that perennial question of “WHY?”.

The question is whether you can still get work out of this body of gas at a single uniform temperature. If you stick to human-scale pistons or fan-blades, no way. For human-scale mechanisms, the 2LoT is going to be right every time. The numbers of molecules we’re dealing with are so gigantic that statistical variations just won’t be useful. If you can get down to scales of mean-free-path in distance and the collision frequency in time, yes there is movement at these scales and so you should be able to harness the obvious movement (kinetic energy) to perform work. If that work comes out as real work, which means that it is either stored as potential energy or goes into kinetic energy, then that volume of gas will be seen to cool, but if it’s virtual work (moving something from one place to another) then no cooling will be seen. For this reason Brownian motion, where the dust or Lycopodium powder is bouncing around all over the place, is just displacement work, averages out to zero, and doesn’t take energy from the gas. Energy is conserved, but work isn’t.

Back to the start again and where the energy comes from in various Free Energy ideas, then.  The real answer so far is that it doesn’t because they don’t actually work. That applies to all the designs I’ve seen except for Dan Sheehan’s work and the Lovell device as replicated by RMS. The actual work output from those so far is minute, though. It’s enough to tell me that 2LoT is not exactly correct, and that if we can beat it by a small amount we can maybe push that up to a useful amount of power.

For one that does work, though, there is a large store of energy in the ambient that, if we’re clever enough, we could use. If it’s a real device, then unless it’s harnessing an obvious energy flow in the way that a solar panel harnesses the Sun’s rays, then using the energy flows within the ambient will mean that the device will cool down in the course of putting out power. If you can’t see an obvious energy flow, and it doesn’t cool down, then it probably doesn’t work.

The natural energy flows you need to know about to help you decide are:
Sunlight – about 1.4kW/m² at the top of the atmosphere, and around 1kW/m² at ground level.
RF – in the region of 1W/m² legally allowed. If it’s a lot more than this then maybe you’d want to move somewhere else.
IR from room-temperature – around 1W/m² at 300K.


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Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
Everyman Standing Order 03: Everyman knows Timing is Critical in any Movement.
   
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I thought I might add my twopennyworth to EG's last post.  Have you ever worked on your car out in sunlight with tools laying on the ground and noted that your shiny tools get hot?  You will find that Ni plated tools get much hotter than Cr plated tools.  This is not because they are less shiny and reflect less sunlight.  The temperature reached depends on the ratio of their spectral absorption over the Sun's light spectrum (which is a narrow band centered on 0.9um wavelength) to their spectral emittance over the spectrum of radiated heat at 300K (which is a band centered on 30um wavelength).   Clearly Ni has a different ratio to Cr, yet they both look highly reflective to our eyes.  And the Ni tools get considerably hotter than the black handle of the screwdriver simply because that black has a ratio nearer to that of Cr.  Our eyes cannot assess the IR spectral characteristics.  Something that looks white (which could be taken as a poor emitter) can actually be a good emitter at IR wavelengths. Snow, for example, would look black if viewed with IR eyes under IR light.  Same goes for titanium dioxide, so if you want your tools to stay cool paint them white or black ;).  My point here is that there are subtle characteristics that can affect how things absorb energy from the environment.

Smudge
   

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My point here is that there are subtle characteristics that can affect how things absorb energy from the environment.

Smudge

Good point.. the equivalence principle needs modifying:

Equivalence principle

https://en.wikipedia.org/wiki/Equivalence_principle

In the physics of general relativity, the equivalence principle is any of several related concepts dealing with the equivalence of gravitational and inertial mass, and to Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is actually the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.

http://hyperphysics.phy-astr.gsu.edu/hbase/grav.html

The gravity force has the same form as Coulomb's law for the forces between electric charges, i.e., it is an inverse square law force which depends upon the product of the two interacting sources. This led Einstein to start with the electromagnetic force and gravity as the first attempt to demonstrate the unification of the fundamental forces. It turns out that this was the wrong place to start, and that gravity will be the last of the forces to unify with the other three forces. Electroweak unification (unification of the electromagnetic and weak forces) was demonstrated in 1983, a result which could not be anticipated in the time of Einstein's search. It now appears that the common form of the gravity and electromagnetic forces arises from the fact that each of them involves an exchange particle of zero mass, not because of an inherent symmetry which would make them easy to unify.

Water - Density and Specific Weight

http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html

Pure water has its highest density 1000 kg/m3 (1.940 slugs/ft3) at temperature 4oC (39.2oF).


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Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
Everyman Standing Order 03: Everyman knows Timing is Critical in any Movement.
   

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Richard Feynman explains the feeling of confusion

https://www.youtube.com/watch?v=lytxafTXg6c

Feynman: Take the world from another point of view (1/4)

https://www.youtube.com/watch?v=PsgBtOVzHKI

 :)


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Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
Everyman Standing Order 03: Everyman knows Timing is Critical in any Movement.
   

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hhop gen 3 and 4 may be used in space travel to generate electricity and different gas products like oxygen and hydrogen. (Different working fluid means different gas products via electrolysis)

By creating a rotational moment in space a specific gravity field can be formed where different states of matter organise themselves depending on their densities.

Artificial gravity


https://en.wikipedia.org/wiki/Artificial_gravity

Artificial gravity / Pseudo-gravity is the theoretical increase or decrease of apparent gravity (g-force) by artificial means, particularly in space, but also on Earth. It can be practically achieved by the use of different forces, particularly the centripetal force and linear acceleration.

The creation of artificial gravity is considered desirable for long-term space travel or habitation, for ease of mobility, for in-space fluid management, and to avoid the adverse long-term health effects of weightlessness.

A number of methods for generating artificial gravity have been proposed, as well as an even larger number of science fiction approaches using both real and fictitious forces. Practical outer space applications of artificial gravity for humans have not yet been built and flown, principally due to the large size of the spacecraft required to produce centripetal acceleration.

Rotation

https://en.wikipedia.org/wiki/Rotating_wheel_space_station

A rotating spacecraft will produce the feeling of gravity on its inside hull. The rotation drives any object inside the spacecraft toward the hull, thereby giving the appearance of a gravitational pull directed outward. Often referred to as a centrifugal force, the "pull" is actually a manifestation of the objects inside the spacecraft attempting to travel in a straight line due to inertia. The spacecraft's hull provides the centripetal force required for the objects to travel in a circle (if they continued in a straight line, they would leave the spacecraft's confines). Thus, the "gravity" felt by the objects is simply the reaction force of the object on the hull reacting to the centripetal force of the hull on the object, in accordance with Newton's Third Law.

Rotating wheel space station


A rotating wheel space station is a hypothetical wheel-shaped space station that rotates about its axis, thus creating an environment of artificial gravity. Occupants of the station would experience centripetal acceleration according to the following equation,

a = \omega^2 r

where \omega is the angular velocity of the station, r is its radius, and a is linear acceleration at any point along its perimeter.

In principle, the station could be configured to simulate the gravitational acceleration of Earth (9.81 m/s²).


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Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
Everyman Standing Order 03: Everyman knows Timing is Critical in any Movement.
   

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Cassini Solstice Mission

On its journey to Saturn, Cassini carried the European-built Huygens probe. On Jan. 14, 2005, Huygens achieved humankind's first landing on a body in the Outer Solar System when it parachuted through Titan's murky skies. Huygens took measurements of atmospheric composition and wind speeds during its descent, along with an incredible series of images showing telltale patterns of erosion by flowing liquid. The probe came to rest on what appeared to be a floodplain, surrounded by rounded cobbles of water ice.

http://saturn.jpl.nasa.gov/science/index.cfm?SciencepageID=73

Colonization of Titan


https://en.wikipedia.org/wiki/Colonization_of_Titan

Saturn’s largest moon Titan is one of several candidates for possible future colonization of the outer Solar System.

Surface and atmospheric composition

According to Cassini data from 2008, Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth. These hydrocarbons rain from the sky and collect in vast deposits that form lakes and dunes.[1] "Titan is just covered in carbon-bearing material—it's a giant factory of organic chemicals", said Ralph Lorenz, who leads the study of Titan based on radar data from Cassini. “This vast carbon inventory is an important window into the geology and climate history of Titan.” Several hundred lakes and seas have been observed, with several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.[2]
Titan 'sea' (left) compared at scale to Lake Superior (right)

Radar images obtained on July 21, 2006 appear to show lakes of liquid hydrocarbon (such as methane and ethane) in Titan's northern latitudes. This is the first discovery of currently existing lakes beyond Earth.[3] The lakes range in size from about a kilometer in width to one hundred kilometers across.

On March 13, 2007, Jet Propulsion Laboratory announced that it found strong evidence of seas of methane and ethane in the northern hemisphere. At least one of these is larger than any of the Great Lakes in North America.[4]

Suitability

The American aerospace engineer and author Robert Zubrin identified Saturn as the most important and valuable of the four gas giants in the Solar System, because of its relative proximity, low radiation, and excellent system of moons. He also named Titan as the most important moon on which to establish a base to develop the resources of the Saturn system.[5]

Habitability

Dr. Robert Zubrin has pointed out that Titan possesses an abundance of all the elements necessary to support life, saying "In certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization." [6] The atmosphere contains plentiful nitrogen and methane, and strong evidence indicates that liquid methane exists on the surface. Evidence also indicates the presence of liquid water and ammonia under the surface, which are delivered to the surface by volcanic activity. Water can easily be used to generate breathable oxygen and nitrogen is ideal to add buffer gas partial pressure to breathable air (it forms about 78% of Earth's atmosphere).[7] Nitrogen, methane and ammonia can all be used to produce fertilizer for growing food.

Atmosphere


Titan has an atmospheric pressure one and a half times that of Earth. This means that the interior air pressure of landing craft and habitats could be set equal or close to the exterior pressure,[citation needed] reducing the difficulty and complexity of structural engineering for landing craft and habitats compared with low or zero pressure environments such as on the Moon, Mars, or the asteroids. The thick atmosphere would also make radiation a non-issue, unlike on the Moon, Mars, or the asteroids. While Titan's atmosphere does contain trace amounts of hydrogen cyanide, in the event that an astronaut's respiration system is breached, the concentration would not inflict more than a slight headache.[citation needed] A greater danger is that the gases of the atmosphere can generate an explosive mixture with oxygen,[citation needed] which requires special measures in the event that a leak occurs in a habitable module or a spacesuit.

Gravity


Titan has a surface gravity of 0.138 g, slightly less than that of the Moon
. Managing long-term effects of low gravity on human health would therefore be a significant issue for long-term occupation of Titan, more so than on Mars. These effects are still an active field of study. They can include symptoms such as loss of bone density, loss of muscle density, and a weakened immune system. Astronauts in Earth orbit have remained in microgravity for up to a year or more at a time. Effective countermeasures for the negative effects of low gravity are well-established, particularly an aggressive regime of daily physical exercise or weighted clothing. The variation in the negative effects of low gravity as a function of different levels of low gravity are not known, since all research in this area is restricted to humans in zero gravity. The same goes for the potential effects of low gravity on fetal and pediatric development. It has been hypothesized that children born and raised in low gravity such as on Titan would not be well adapted for life under the higher gravity of Earth.[8]

Temperature


The temperature on Titan is about 94 K (−179 °C, or −290.2 °F), so insulation and heat generation and management would be significant concerns. Although the air pressure at Titan's surface is about 1.5 times that of Earth at sea level, because of the colder temperature the density of the air is closer to 4.5 times that of Earth sea level. At this density, temperature shifts over time and between one locale and another would be far smaller than comparable types of temperature changes present on Earth. The corresponding narrow range of temperature variation reduces the difficulties in structural engineering.

Relative thickness of the atmosphere combined with extreme cold makes additional troubles for human habitation. Unlike in a vacuum, the high atmospheric density makes thermoinsulation a significant engineering problem.

Flight

The very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for an aircraft to maintain lift, so much so that a human would be able to strap on wings and easily fly through the atmosphere.[6] However, due to Titan's extremely low temperatures, heating of a flight-bound vehicle becomes a key obstacle.[9]

Living on the Moon: Inflatable Habitat Research

https://www.nasa.gov/centers/johnson/pdf/208744main_fs-2007-11-01-jsc.pdf

Shall we send a hhop habitation complex to the moon ? Practice run for Titan..


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Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
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Saturn's Titan Reveals Strange Gravity Phenomenon

http://www.dailygalaxy.com/my_weblog/2013/08/saturns-titan-reveals-strange-gravity-phenomenon.html

An analysis of gravity and topography data from Saturn's largest moon, Titan, has revealed that Titan's ice shell is rigid and that relatively small topographic features on the surface are associated with large roots extending into the underlying ocean. Led by planetary scientists Douglas Hemingway and Francis Nimmo at the University of California, Santa Cruz, the study used new data from NASA's Cassini spacecraft. The researchers were surprised to find a negative correlation between the gravity and topography signals on Titan.
"Normally, if you fly over a mountain, you expect to see an increase in gravity due to the extra mass of the mountain. On Titan, when you fly over a mountain the gravity gets lower. That's a very odd observation," said Nimmo, a professor of Earth and planetary sciences at UC Santa Cruz.

To explain that observation, the researchers developed a model in which each bump in the topography on the surface of Titan is offset by a deeper "root" big enough to overwhelm the gravitational effect of the bump on the surface. The root is like an iceberg extending below the ice shell into the ocean underneath it. "Because ice is lower density than water, you get less gravity when you have a big chunk of ice there than when you have water," Nimmo explained.

An iceberg floating in water is in equilibrium, its buoyancy balancing out its weight. In this model of Titan, however, the roots extending below the ice sheet are so much bigger than the bumps on the surface that their buoyancy is pushing them up against the ice sheet.

"It's like a big beach ball under the ice sheet pushing up on it, and the only way to keep it submerged is if the ice sheet is strong," said Hemingway, a doctoral candidate in planetary geophysics at UCSC and lead author of the paper. "If large roots are the reason for the negative correlation, it means that Titan's ice shell must have a very thick rigid layer."

The researchers calculated that, in this model, Titan's ice shell would have to have a rigid layer at least 40 kilometers thick. They also found that hundreds of meters of surface erosion and deposition are needed to account for the observed imbalance between the large roots and small surface topography. The results from their model are similar to estimates obtained by geomorphologists studying the erosion of impact craters and other features on Titan.

These findings have several implications. For example, a thick rigid ice shell makes it very difficult to produce ice volcanoes, which some have proposed to explain certain features seen on the surface.

Unlike Earth's geologically active crust, Titan's ice shell isn't getting recycled by convection or plate tectonics. "It's just sitting there, and weather and erosion are acting on it, moving stuff around and redepositing sediments," Nimmo said. "It may be like the surface of Earth would be if you turned plate tectonics off."

The researchers are not sure what could have given rise to Titan's topographical features with their deep roots. Titan's eccentric orbit around Saturn generates tides that flex the moon's surface and create tidal heating, which could cause variations to develop in the thickness of the ice shell, Hemingway said.

The Daily Galaxy via University of California, Santa Cruz


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http://www.russianspaceweb.com/los.html

Way station on the road to the Moon

To establish a permanent foothold on the Moon, earthlings would need more than a single manned spacecraft. As in past conquests of remote and inhospitable lands, it might be necessary to pre-position supplies and accommodations along the way. The most convenient location for a way station on the road to the Moon, would be the lunar orbit. Here, landers returning from the surface of the Moon would link up with transport ships coming from Earth. Crews and cargo could be exchanged and large quantities of propellant could be accumulated for specific “high-power” missions, such as the delivery of heavy lunar base modules on the surface of the Moon. (138)

The concept of a lunar orbital station, or LOS, appeared in early American and Soviet studies of lunar exploration. As early as 1959, Wernher von Braun envisioned the refueling of transport ships in the lunar orbit, in order to facilitate the construction of a lunar base within the project Horizon. In 1962, Sergei Korolev, the founder of the Soviet space program, considered the possibility of establishing long-duration "satellite-stations" in lunar orbit with the goal of supporting deep-space expeditions. (137) The idea was further evaluated around 1963 within the L4 project.

Still, for most of the 20th century, a lunar orbital station had remained a “luxury” item on the list of priorities of contemporary space programs. It was impossible to justify within the limited scope of lunar exploration at the time. However, the first decade of the 21st century saw a renaissance in lunar exploration, with rocket scientists on both sides of the Atlantic dusting off their ideas for establishing a permanent presence on the surface of the Moon. In the post-Soviet Russia, planners at the country’s leading manned space flight centers – RKK Energia and Khrunichev enterprise – saw a lunar orbital station as an essential element in the Earth-Moon transport chain.

Khrunichev’s LOS concept

On November 14-15, 2007, the Gagarin Cosmonaut Training Center in Star City hosted the 7th scientific conference on manned space flight. Sergei Pugachenko, a representative of KB Salyut, the development arm at Khrunichev enterprise, revealed ambitious long-term plans for exploration of the Moon and Mars.

The lunar infrastructure proposed by Khrunichev included two major elements – a base on the surface of the Moon and a lunar orbital station. Pugachenko’s presentation included a slide, which was perhaps the first depiction of a possible configuration of the lunar orbital station, LOS.

The spacecraft clearly traced its roots to the generations of Soviet space stations, such as Salyut, Almaz, Mir's core module and the service module of the International Space Station. Not coincidently, all these vehicles were built at Khrunichev. LOS sported six docking ports, high-power antenna for communications, maneuvering and attitude control engines, solar panels and a robotic arm, similar to the one developed by the European Space Agency, ESA, for the Russian segment of the ISS.

In an accompanying statement to the media, Pugachenko explained that the lunar orbital station would be used for the transfer and storage of cargo and propellants, as well as serve as temporary or emergency quarters for crews and a platform for scientific studies of the Moon, such as remote-sensing and cartography. LOS could also help relay signals between Earth and the lunar surface.

Both the lunar surface base and the lunar orbital station would be delivered into space by a super-heavy version of the Angara rocket with a cargo capacity of 100 tons to the low-Earth orbit. To top it off, Khrunichev drafted a family of giant rockets, with a cargo capacity to low-earth orbit ranging from 45 tons to an incredible 175 tons!

Nautilus-X

https://en.wikipedia.org/wiki/Nautilus-X

Nautilus-X (Non-Atmospheric Universal Transport Intended for Lengthy United States Exploration) is a multi-mission space exploration vehicle concept developed by engineers Mark Holderman and Edward Henderson of the Technology Applications Assessment Team of NASA.

The concept was first proposed in January, 2011 for long duration (one to twenty-four months) exo-atmospheric space journeys for a six-person crew. In order to limit the effects of microgravity on human health, the spacecraft would be equipped with a centrifuge.

The design was intended to be relatively inexpensive by manned spaceflight standards[2] as it was projected to only cost US$3.7 billion. In addition, it was suggested that it might only need 64 months of work.[3][4]


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Stanford torus

https://en.wikipedia.org/wiki/Stanford_torus

The Stanford torus is a proposed design[1] for a space habitat capable of housing 10,000 to 140,000 permanent residents.[2]

The Stanford torus was proposed during the 1975 NASA Summer Study, conducted at Stanford University, with the purpose of speculating on designs for future space colonies[3] (Gerard O'Neill later proposed his Island One or Bernal sphere as an alternative to the torus[4]). "Stanford torus" refers only to this particular version of the design, as the concept of a ring-shaped rotating space station was previously proposed by Wernher von Braun[5] and Herman Potočnik.[6]

It consists of a torus, or doughnut-shaped ring, that is 1.8 km in diameter (for the proposed 10,000 person habitat described in the 1975 Summer Study) and rotates once per minute to provide between 0.9g and 1.0g of artificial gravity on the inside of the outer ring via centrifugal force.[7]

Sunlight is provided to the interior of the torus by a system of mirrors. The ring is connected to a hub via a number of "spokes", which serve as conduits for people and materials travelling to and from the hub. Since the hub is at the rotational axis of the station, it experiences the least artificial gravity and is the easiest location for spacecraft to dock. Zero-gravity industry is performed in a non-rotating module attached to the hub's axis.[8]

The interior space of the torus itself is used as living space, and is large enough that a "natural" environment can be simulated; the torus appears similar to a long, narrow, straight glacial valley whose ends curve upward and eventually meet overhead to form a complete circle. The population density is similar to a dense suburb, with part of the ring dedicated to agriculture and part to housing.[9]

Construction

The torus would require nearly 10 million tons of mass. Construction would use materials extracted from the Moon and sent to space using a mass driver. A mass catcher at L2 would collect the materials, transporting them to L5 where they could be processed in an industrial facility to construct the torus. Only materials that could not be obtained from the Moon would have to be imported from Earth. Asteroid mining was an alternative source of materials.[10]


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Centrifuge

https://en.wikipedia.org/wiki/Centrifuge

A centrifuge is a piece of equipment that puts an object in rotation around a fixed axis (spins it in a circle), applying a potentially strong force perpendicular to the axis of spin (outward). The centrifuge works using the sedimentation principle, where the centripetal acceleration causes denser substances and particles to move outward in the radial direction. At the same time, objects that are less dense are displaced and move to the center. In a laboratory centrifuge that uses sample tubes, the radial acceleration causes denser particles to settle to the bottom of the tube, while low-density substances rise to the top.[1]

There are 3 types of centrifuge designed for different applications. Industrial scale centrifuges are commonly used in manufacturing and waste processing to sediment suspended solids, or to separate immiscible liquids. An example is the cream separator found in dairies. Very high speed centrifuges and ultracentrifuges able to provide very high accelerations can separate fine particles down to the nano-scale, and molecules of different masses.

Large centrifuges are used to simulate high gravity or acceleration environments (for example, high-G training for test pilots). Medium-sized centrifuges are used in washing machines and at some swimming pools to wring water out of fabrics.

Gas centrifuges are used for isotope separation, such as to enrich nuclear fuel for fissile isotopes.

Sedimentation

https://en.wikipedia.org/wiki/Sedimentation

Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration, or electromagnetism. In geology, sedimentation is often used as the opposite of erosion, i.e., the terminal end of sediment transport. In that sense, it includes the termination of transport by saltation or true bedload transport. Settling is the falling of suspended particles through the liquid, whereas sedimentation is the termination of the settling process.

Sedimentation may pertain to objects of various sizes, ranging from large rocks in flowing water to suspensions of dust and pollen particles to cellular suspensions to solutions of single molecules such as proteins and peptides. Even small molecules supply a sufficiently strong force to produce significant sedimentation.

The term is typically used in geology to describe the deposition of sediment which results in the formation of sedimentary rock, but it is also used in various chemical and environmental fields to describe the motion of often-smaller particles and molecules. This process is also used in the biotech industry to separate cells from the culture media.


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Newton’s Electric Clockwork Solar System

Posted on April 21, 2009 by Wal Thornhill   

http://www.holoscience.com/wp/newtons-electric-clockwork-solar-system/

We are told that gravity rules the cosmos. The story of the big bang, the origin of galaxies and stars, and our ultimate fate are founded on this belief. But the March 2009 Astronomy magazine carries the surprising headline, “Is there something we don’t know about gravity?” The question should be, “why do we think that physicists know anything about gravity beyond mathematical descriptions of its observed effects?” All that modern physics has done is to obscure the need for serious investigation of an unsolved problem. Even some effects attributed to the action of gravity, like the bending of light, need not have anything to do with gravity. Indeed, we are so far from understanding gravity that we don’t know the right questions to ask.

-

However, G is measured at the Earth’s surface and used in this equation for the Sun and every other planet. It is simply assumed that G is universal and has the same value for all celestial bodies.

G has the peculiar dimensions of length cubed, divided by mass and by time squared ([L]3/[M][T]2)
. A. K. T. Assis argues that dimensional constants like G should not appear in the laws of physics. They “must depend on cosmological or microscopic properties of the universe.” [1] Garcia-Berro et al state, “Questioning the constancy of fundamental parameters is essentially trying to understand a more fundamental theory behind.” [2]


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g-force

g-force (with g from gravitational) is a measurement of the type of acceleration that causes weight. Despite the name, it is incorrect to consider g-force a fundamental force, as "g-force" (lower case character) is a type of acceleration that can be measured with an accelerometer. Since g-force accelerations indirectly produce weight, any g-force can be described as a "weight per unit mass" (see the synonym specific weight). When the g-force acceleration is produced by the surface of one object being pushed by the surface of another object, the reaction-force to this push produces an equal and opposite weight for every unit of an object's mass. The types of forces involved are transmitted through objects by interior mechanical stresses. The g-force acceleration (save for certain electromagnetic force influences) is the cause of an object's acceleration in relation to free-fall.[1][2]

The g-force acceleration experienced by an object is due to the vector sum of all non-gravitational and non-electromagnetic forces acting on an object's freedom to move. In practice, as noted, these are surface-contact forces between objects. Such forces cause stresses and strains on objects, since they must be transmitted from an object surface. Because of these strains, large g-forces may be destructive.

Gravitation acting alone does not produce a g-force, even though g-forces are expressed in multiples of the acceleration of a standard gravity. Thus, the standard gravitational acceleration at the Earth's surface produces g-force only indirectly, as a result of resistance to it by mechanical forces. These mechanical forces actually produce the g-force acceleration on a mass. For example, the 1 g force on an object sitting on the Earth's surface is caused by mechanical force exerted in the upward direction by the ground, keeping the object from going into free-fall. The upward contact-force from the ground ensures that an object at rest on the Earth's surface is accelerating relative to the free-fall condition (Free fall is the path that the object would follow when falling freely toward the Earth's center). Stress inside the object is ensured from the fact that the ground contact forces are transmitted only from the point of contact with the ground.

Objects allowed to free-fall in an inertial trajectory under the influence of gravitation-only, feel no g-force acceleration, a condition known as zero-g (which means zero g-force). This is demonstrated by the "zero-g" conditions inside a freely falling elevator falling toward the Earth's center (in vacuum), or (to good approximation) conditions inside a spacecraft in Earth orbit. These are examples of coordinate acceleration (a change in velocity) without a sensation of weight. The experience of no g-force (zero-g), however it is produced, is synonymous with weightlessness.

In the absence of gravitational fields, or in directions at right angles to them, proper and coordinate accelerations are the same, and any coordinate acceleration must be produced by a corresponding g-force acceleration. An example here is a rocket in free space, in which simple changes in velocity are produced by the engines, and produce g-forces on the rocket and passengers.

Acceleration and forces

The term g-force is technically incorrect as it is a measure of acceleration, not force. While acceleration is a vector quantity, g-force accelerations ("g-forces" for short) are often expressed as a scalar, with positive g-forces pointing downward (indicating upward acceleration), and negative g-forces pointing upward. Thus, a g-force is a vector acceleration. It is an acceleration that must be produced by a mechanical force, and cannot be produced by simple gravitation. Objects acted upon only by gravitation, experience (or "feel") no g-force, and are weightless.

G-forces, when multiplied by a mass upon which they act, are associated with a certain type of mechanical force in the correct sense of the term force, and this force produces compressive stress and tensile stress. Such forces result in the operational sensation of weight, but the equation carries a sign change due to the definition of positive weight in the direction downward, so the direction of weight-force is opposite to the direction of g-force acceleration:

Weight = mass ∗ ( - g-force)

The reason for the minus sign is that the actual force (i.e., measured weight) on an object produced by a g-force is in the opposite direction to the sign of the g-force, since in physics, weight is not the force that produces the acceleration, but rather the equal-and-opposite reaction force to it. If the direction upward is taken as positive (the normal cartesian convention) then positive g-force (an acceleration vector that points upward) produces a force/weight on any mass, that acts downward (an example is positive-g acceleration of a rocket launch, producing downward weight). In the same way, a negative-g force is an acceleration vector downward (the negative direction on the y axis), and this acceleration downward produces a weight-force in a direction upward (thus pulling a pilot upward out of the seat, and forcing blood toward the head of a normally oriented pilot).

If a g-force (acceleration) is vertically upward and is applied by the ground (which is accelerating through space-time) or applied by the floor of an elevator to a standing person, most of the body experiences compressive stress which at any height, if multiplied by the area, is the related mechanical force, which is the product of the g-force and the supported mass (the mass above the level of support, including arms hanging down from above that level). At the same time, the arms themselves experience a tensile stress, which at any height, if multiplied by the area, is again the related mechanical force, which is the product of the g-force and the mass hanging below the point of mechanical support. The mechanical resistive force spreads from points of contact with the floor or supporting structure, and gradually decreases toward zero at the unsupported ends (the top in the case of support from below, such as a seat or the floor, the bottom for a hanging part of the body or object). With compressive force counted as negative tensile force, the rate of change of the tensile force in the direction of the g-force, per unit mass (the change between parts of the object such that the slice of the object between them has unit mass), is equal to the g-force plus the non-gravitational external forces on the slice, if any (counted positive in the direction opposite to the g-force).

For a given g-force the stresses are the same, regardless of whether this g-force is caused by mechanical resistance to gravity, or by a coordinate-acceleration (change in velocity) caused by a mechanical force, or by a combination of these. Hence, for people all mechanical forces feels exactly the same whether they cause coordinate acceleration or not. For objects likewise, the question of whether they can withstand the mechanical g-force without damage is the same for any type of g-force. For example, upward acceleration (e.g., increase of speed when going up or decrease of speed when going down) on Earth feels the same as being stationary on a celestial body with a higher surface gravity. Again, one should note that gravitation acting alone does not produce any g-force; g-force is only produced from mechanical pushes and pulls. For a free body (one that is free to move in space) such g-forces only arise as the "inertial" path that is the natural effect of gravitation, or the natural effect of the inertia of mass, is modified. Such modification may only arise from influences other than gravitation.


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Apparent weight

https://en.wikipedia.org/wiki/Apparent_weight#Comparison_with_g-force

In physics, apparent weight is a property of objects that corresponds to how heavy an object is. The apparent weight of an object will differ from the weight of an object whenever the force of gravity acting on the object is not balanced by an equal but opposite normal force. By definition, the weight of an object is equal to the magnitude of the force of gravity acting on it. This means that even a "weightless" astronaut in low Earth orbit has almost the same weight as he would have while standing on the ground.

An object that rests on the ground is subject to a normal force exerted by the ground. The normal force acts only on the boundary of the object that is in contact with the ground. This force is transferred into the body; the force of gravity on every part of the body is balanced by stress forces acting on that part. A "weightless" astronaut feels weightless due to the absence of these stress forces. By defining the apparent weight of an object in terms of normal forces, one can capture this effect of the stress forces. A common definition is "the force the body exerts on whatever it rests on."[1]

The apparent weight can also differ from weight when an object is "partially or completely immersed in a fluid", where there is an "upthrust" from the liquid that is working against the force of gravity.[2] Another example is the weight of an object or person riding in an elevator. When the elevator begins rising, the object begins exerting a force in the downward direction. If a scale was used, it would be seen that the weight of the object is becoming heavier because of the downward force, changing the apparent weight.[3]

The role of apparent weight is also important in fluidization, when dealing with a number of particles, as it is the amount of force that the "upward drag force" needs to overcome in order for the particles to rise and for fluidization to occur.[4]

Fluidization

https://en.wikipedia.org/wiki/Fluidization

Fluidization (or fluidisation) is a process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state. This process occurs when a fluid (liquid or gas) is passed up through the granular material.

When a gas flow is introduced through the bottom of a bed of solid particles, it will move upwards through the bed via the empty spaces between the particles. At low gas velocities, aerodynamic drag on each particle is also low, and thus the bed remains in a fixed state. Increasing the velocity, the aerodynamic drag forces will begin to counteract the gravitational forces, causing the bed to expand in volume as the particles move away from each other. Further increasing the velocity, it will reach a critical value at which the upward drag forces will exactly equal the downward gravitational forces, causing the particles to become suspended within the fluid. At this critical value, the bed is said to be fluidized and will exhibit fluidic behavior. By further increasing gas velocity, the bulk density of the bed will continue to decrease, and its fluidization becomes more violent, until the particles no longer form a bed and are "conveyed" upwards by the gas flow.

When fluidized, a bed of solid particles will behave as a fluid, like a liquid or gas. Like water in a bucket: the bed will conform to the volume of the chamber, its surface remaining perpendicular to gravity; objects with a lower density than the bed density will float on its surface, bobbing up and down if pushed downwards, while objects with a higher density sink to the bottom of the bed. The fluidic behavior allows the particles to be transported like a fluid, channeled through pipes, not requiring mechanical transport (e.g. conveyor belt).

A simplified every-day-life example of a gas-solid fluidized bed would be a hot-air popcorn popper. The popcorn kernels, all being fairly uniform in size and shape, are suspended in the hot air rising from the bottom chamber. Because of the intense mixing of the particles, akin to that of a boiling liquid, this allows for a uniform temperature of the kernels throughout the chamber, minimizing the amount of burnt popcorn. After popping, the now larger popcorn particles encounter increased aerodynamic drag which pushes them out of the chamber and into a bowl.

The process is also key in the formation of a sand volcano and fluid escape structures in sediments and sedimentary rocks.


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Mechanically isolated system

https://en.wikipedia.org/wiki/Mechanically_isolated_system

In thermodynamics, a mechanically isolated system is a system that is mechanically constraint to disallow deformations, so that it cannot perform any work on its environment. It also does not permit any mass flows in or out of the system. It may however, exchange heat across the system boundary.

For a simple system, mechanical isolation is equivalent to a state of constant volume and any process which occurs in such a simple system is said to be isochoric. [1]

The opposite of a mechanically isolated system is a mechanically open system,[citation needed] which allows the transfer of mechanical energy. For a simple system, a mechanically open boundary is one that is allowed to move under pressure differences between the two sides of the boundary. At mechanical equilibrium, the pressures on both sides of a mechanically open boundary are equal, but only a mechanically isolating boundary can support pressure differences.


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Whirlpool in a bottle DIY Science Experiment

https://www.youtube.com/watch?v=bvibfya_PQ4

Creating whirlpool or tornado in a bottle is super easy..  O0

Cyclone Tube Tornado in a Bottle ~ Incredible Science


https://www.youtube.com/watch?v=0LfZFGcGc_I

Easy Water Stacking Sugar Density Experiment ~ DIY Incredible Science

https://www.youtube.com/watch?v=H78Xd3ToxP4


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Evidence found that spinning black holes drag spacetime

http://news.mit.edu/1997/blackholes

Just as Einstein's general theory of relativity predicts

November 6, 1997

CAMBRIDGE, Mass.--Avid Star Trek fans--and physicists--have known that spacetime gets distorted near certain galactic objects, but now they have more precise information about the way that distortion works near spinning black holes. Researchers led by an MIT scientist recently obtained the first observational evidence that massive, rotating black holes in our galaxy drag space and time around with them as they gather matter into their spiral, much as a twister picks up objects in its path.

This phenomenon, known as frame-dragging, was first predicted in 1918 as a natural consequence of Einstein's general theory of relativity, which describes the effects of gravity on space and time. But it had been unproved by experiments or observation until recently, when Italian researchers suggested the effect might be present near spinning neutron stars. The MIT team then applied a similar idea to several black holes in our galaxy.

"If our interpretation is correct, it could be said to prove the presence of frame-dragging near spinning black holes," said Dr. Wei Cui, a research scientist at MIT's Center for Space Research who is lead author on a paper to be presented at a meeting of the High Energy Astrophysics Division of the American Astronomical Society on November 6. His collaborators are research scientists Shuang N. Zhang, of NASA's Marshall Space Flight Center, and Wan Chen, of NASA's Goddard Space Flight Center.

Black holes are exceptionally compact objects with a gravitational pull so strong that no light can escape them. Since black holes cannot be seen directly, their existence can only be deduced from observations of the behavior of sister-stars thought to cohabit with black holes. The gravitational pull of the black hole forces the sister star to revolve around it.

The black hole then acquires material from the star by pulling the matter into the orbit of an accretion disk, a ring-like disk of gas that moves around the black hole. As the matter in that disk moves closer and closer to the black hole, the matter heats up and begins to emit X-rays. These X-ray emissions are critical to the measurement of the frame-dragging effect.

Dr. Cui's team took the results of their own recent study that measured how fast black holes spin by using the inferred temperature and location of the matter rotating around them. That study, which came out earlier this year, gave the first published measurement of a black hole's spin. Using that measurement and the mass of the black hole, his team then determined how frame-dragging would affect the material in the accretion disk as it orbits the black hole.

They showed that the matter's orbit in the accretion disk would wobble, much as a child's top wobbles when it slows down. The frequency at which it would wobble, based on their calculations, turned out to be the same frequency as the actual oscillations in intensity of the x-ray emissions previously measured by other researchers. They theorized that this wobble is evidence of frame-dragging, because the matter's orbit can only wobble if the space and time in which it exists are being dragged.

Dr. Cui points out that they cannot claim with absolute certainty that they have proven the presence of frame-dragging. However, he notes that while there are other interpretations that work for two of the five black holes studied, none of them can be satisfactorily applied to all five.

Actually, the general theory of relativity predicts that frame-dragging should occur around any spinning body, even the Earth. But the effect would be much more significant around a body with both tremendous mass and small size, like a black hole, and therefore somewhat easier to detect. Even so, its detection took nearly 80 years from the time it was first predicted.

"Although theorists predicted the frame-dragging effect, they didn't have any observational evidence to prove it before the Rossi X-ray Timing Explorer," said Dr. Cui, whose research was funded by NASA.

The Rossi X-ray Timing Explorer, or RXTE, is a 6,700-pound observatory placed into orbit by NASA in December 1995 to gather information on black holes and neutron stars--objects akin to black holes only less massive. It is named after Bruno B. Rossi, an MIT professor who was a pioneer in the field of X-ray astronomy.

Two of the instruments on board RXTE were designed by Professor Hale Bradt and colleagues at MIT's Center for Space Research. The first, the All Sky Monitor (ASM), sweeps over 80 percent of the sky every 90 minutes, and monitors the intensities and spectra of the brightest X-ray sources. The second is the Experiment Data System (EDS), a powerful computer that crunches numbers before transmitting data back to Earth.

At the meeting in Estes Park, Colo., where Dr. Cui's findings are being presented, the Italian researchers also plan to present their proof of frame-dragging by spinning neutron stars. Most of the data used by both teams was obtained by RXTE.

The very existence of black holes is itself the subject of considerable scientific debate. They are thought to be created when a very large star near the end of its life collapses under its own gravitational pull. Such stars are exceptionally dense because they become as small as 60 kilometers--or 40 miles--in diameter, while still retaining a mass many times that of our Sun. Once a star reaches this stage, its gravity is so powerful that absolutely nothing, not even light, can escape, leaving what appears to us as a black hole in space.

"Of course there are still many unanswered questions about the X-ray emission processes in these black hole systems. But the observations in this case seem to suggest the presence of the frame-dragging effect--that spinning black holes do drag space and time around with them," said Dr. Cui. Something Trekkies have known for years.


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NASA Announces Results of Epic Space-Time Experiment

http://science.nasa.gov/science-news/science-at-nasa/2011/04may_epic/

May 4, 2011: Einstein was right again. There is a space-time vortex around Earth, and its shape precisely matches the predictions of Einstein's theory of gravity.

Researchers confirmed these points at a press conference today at NASA headquarters where they announced the long-awaited results of Gravity Probe B (GP-B).

"The space-time around Earth appears to be distorted just as general relativity predicts," says Stanford University physicist Francis Everitt, principal investigator of the Gravity Probe B mission.


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Spinning Earth twists space

http://www.nature.com/news/2004/041018/full/news041018-11.html

Laser measurements confirm Einstein's general theory of relativity.

Mark Peplow

One of the last untested predictions of general relativity has been confirmed by the first reasonably accurate measurement of how the rotating Earth warps the fabric of space.

The experiment, carried out for virtually no cost with Earth-based laser range-finders, scoops Gravity Probe B, the US$700 million orbiting craft launched in April to test exactly the same effect. However, the Gravity Probe B team has questioned whether the result is really quite as accurate as it seems.

The space warp is a consequence of Einstein's general theory of relativity, which describes gravity as a curvature in space produced by objects sitting in it. It also implies that a rotating mass will drag space around it like a spinning top placed in treacle - an effect known as the Lense-Thirring effect, or more commonly as 'frame-dragging'. The effect becomes important in understanding extreme situations like spinning quasars, and the rotation of jets of gas around black holes.

The effect was first predicted by Austrian physicists Joseph Lense and Hans Thirring in 1918, but until now scientists haven't had sufficiently accurate instruments to measure its tiny perturbations in the fabric of our Universe.

Ignazio Ciufolini at the University of Lecce, Italy and Erricos Pavlis at the University of Maryland in Baltimore charted the path of two NASA satellites, LAGEOS and LAGEOS 2, over 11 years with laser range-finders with the precision of a few millimetres. The effect dragged the satellite's orbits out of position by about 2 metres each year, the researchers report in this week's Nature1.

The researchers say that their result is 99% of the value predicted by relativity, with an error of up to 10%. "Their result is the first reasonably accurate measurement of frame-dragging," comments Neil Ashby, a physicist from the University of Colorado, Boulder.
Doubts

But some scientists remain unconvinced that the measurements are as accurate as the Italian researchers claim. "One of the difficulties is extracting the frame-dragging effect from the huge gravitational effect of the Earth," says Clifford Will, a physicist at Washington University in St. Louis, Missouri, who chairs NASA's Science Advisory Committee for Gravity Probe B.

If the Earth were perfectly symmetrical, frame-dragging would be easy to measure. But the lumpy Earth generates an uneven gravity field, Will points out, which moves the satellites about far more than frame-dragging.

To tease the two effects apart, Ciufolini and Pavlis used a map of the Earth's gravity field provided by a NASA mission called GRACE, launched in March 2002. This relies on two satellites orbiting Earth about 220 kilometres apart, measuring the tiny changes in that distance as they pass through different parts of the Earth's gravity field. Ciufolini's previous attempt2 at measuring frame-dragging was less than 20% accurate, because it did not have the benefit of the GRACE gravity model.

"The laser-ranging method can deliver the accuracy, but it is still uncertain if the GRACE gravity models are good enough," says John Ries, a physicist at the University of Texas, Austin. Will adds that the Gravity Probe B team is also sceptical, and thinks that Ciufolini may have drastically underestimated his errors.
Scooped?

Either way, the Gravity Probe B experiment is expected to deliver a measurement of frame-dragging with 1% accuracy very soon. "I admire the people that have worked for 40 years on this experiment. It's certainly worthwhile," says Ciufolini.

Physicists did not expect either of these experiments to overturn relativity, but insist that confirmation was still essential. "There could be an effect," says Will. "It hasn't been measured, so we have to measure it." But he concedes: "It gets tricky when it costs so much."

The last major prediction of general relativity requiring confirmation is the existence of gravity waves. The LIGO experiment, run by the California Institute of Technology and the Massachusetts Institute of Technology, is already searching for these on Earth, while NASA's LISA probes are expected to launch in 2010.


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Gravity

https://en.wikipedia.org/wiki/Gravity

Gravity or gravitation is a natural phenomenon by which all things with energy are brought towards (or 'gravitate' towards) one another, including stars, planets, galaxies and even light and sub-atomic particles. Gravity is responsible for the complexity in the universe, by creating spheres of hydrogen — where hydrogen fuses under pressure to form stars — and grouping them into galaxies. Without gravity, the universe would be an uncomplicated one, existing without thermal energy and composed only of equally spaced particles[citation needed]. On Earth, gravity gives weight to physical objects and causes the tides. Gravity has an infinite range, although its effects become increasingly weaker on farther objects.

Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915) which describes gravity, not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass/energy; and resulting in time dilation, where time lapses more slowly in strong gravitation. However, for most applications, gravity is well approximated by Newton's law of universal gravitation, which postulates that gravity is a force where two bodies of mass are directly drawn (or 'attracted') to each other according to a mathematical relationship, where the attractive force is proportional to the product of their masses and inversely proportional to the square of the distance between them. This is considered to occur over an infinite range, such that all bodies (with mass) in the universe are drawn to each other no matter how far they are apart.

Gravity is the weakest of the four fundamental interactions of nature. The gravitational attraction is approximately 10−38 times the strength of the strong force (i.e. gravity is 38 orders of magnitude weaker), 10−36 times the strength of the electromagnetic force, and 10−29 times the strength of the weak force. As a consequence, gravity has a negligible influence on the behavior of sub-atomic particles, and plays no role in determining the internal properties of everyday matter (but see quantum gravity). On the other hand, gravity is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape, and trajectory (orbit) of astronomical bodies. It is responsible for various phenomena observed on Earth and throughout the universe; for example, it causes the Earth and the other planets to orbit the Sun, the Moon to orbit the Earth, the formation of tides, and the formation and evolution of galaxies, stars and the Solar System.

In pursuit of a theory of everything, the merging of general relativity and quantum mechanics (or quantum field theory) into a more general theory of quantum gravity has become an area of research.

History of gravitational theory

https://en.wikipedia.org/wiki/History_of_gravitational_theory

Scientific revolution

Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries. In his famous (though possibly apocryphal[1]) experiment dropping balls from the Tower of Pisa, and later with careful measurements of balls rolling down inclines, Galileo showed that gravity accelerates all objects at the same rate. This was a major departure from Aristotle's belief that heavier objects accelerate faster.[2] Galileo postulated air resistance as the reason that lighter objects may fall more slowly in an atmosphere. Galileo's work set the stage for the formulation of Newton's theory of gravity.

Newton's theory of gravitation


https://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. In his own words, "I deduced that the forces which keep the planets in their orbs must [be] reciprocally as the squares of their distances from the centers about which they revolve: and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly."[3] The equation is the following:

F = G \frac{m_1 m_2}{r^2}\

Where F is the force, m1 and m2 are the masses of the objects interacting, r is the distance between the centers of the masses and G is the gravitational constant.

Newton's theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the general position of the planet, and Le Verrier's calculations are what led Johann Gottfried Galle to the discovery of Neptune.

A discrepancy in Mercury's orbit pointed out flaws in Newton's theory. By the end of the 19th century, it was known that its orbit showed slight perturbations that could not be accounted for entirely under Newton's theory, but all searches for another perturbing body (such as a planet orbiting the Sun even closer than Mercury) had been fruitless. The issue was resolved in 1915 by Albert Einstein's new theory of general relativity, which accounted for the small discrepancy in Mercury's orbit.

Although Newton's theory has been superseded by the Einstein's general relativity, most modern non-relativistic gravitational calculations are still made using the Newton's theory because it is simpler to work with and it gives sufficiently accurate results for most applications involving sufficiently small masses, speeds and energies.

Equivalence principle

https://en.wikipedia.org/wiki/Equivalence_principle

The equivalence principle, explored by a succession of researchers including Galileo, Loránd Eötvös, and Einstein, expresses the idea that all objects fall in the same way. The simplest way to test the weak equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the same rate when other forces (such as air resistance and electromagnetic effects) are negligible. More sophisticated tests use a torsion balance of a type invented by Eötvös. Satellite experiments, for example STEP, are planned for more accurate experiments in space.[4]

Formulations of the equivalence principle include:

    The weak equivalence principle: The trajectory of a point mass in a gravitational field depends only on its initial position and velocity, and is independent of its composition.[5]
    The Einsteinian equivalence principle: The outcome of any local non-gravitational experiment in a freely falling laboratory is independent of the velocity of the laboratory and its location in spacetime.[6]
    The strong equivalence principle requiring both of the above.

General relativity

https://en.wikipedia.org/wiki/Introduction_to_general_relativity

In general relativity, the effects of gravitation are ascribed to spacetime curvature instead of a force. The starting point for general relativity is the equivalence principle, which equates free fall with inertial motion and describes free-falling inertial objects as being accelerated relative to non-inertial observers on the ground.[7][8] In Newtonian physics, however, no such acceleration can occur unless at least one of the objects is being operated on by a force.

Einstein proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths in curved spacetime. These straight paths are called geodesics. Like Newton's first law of motion, Einstein's theory states that if a force is applied on an object, it would deviate from a geodesic. For instance, we are no longer following geodesics while standing because the mechanical resistance of the Earth exerts an upward force on us, and we are non-inertial on the ground as a result. This explains why moving along the geodesics in spacetime is considered inertial.

Einstein discovered the field equations of general relativity, which relate the presence of matter and the curvature of spacetime and are named after him. The Einstein field equations are a set of 10 simultaneous, non-linear, differential equations. The solutions of the field equations are the components of the metric tensor of spacetime. A metric tensor describes a geometry of spacetime. The geodesic paths for a spacetime are calculated from the metric tensor.

Solutions

Notable solutions of the Einstein field equations include:

    The Schwarzschild solution, which describes spacetime surrounding a spherically symmetric non-rotating uncharged massive object. For compact enough objects, this solution generated a black hole with a central singularity. For radial distances from the center which are much greater than the Schwarzschild radius, the accelerations predicted by the Schwarzschild solution are practically identical to those predicted by Newton's theory of gravity.

    The Reissner-Nordström solution, in which the central object has an electrical charge. For charges with a geometrized length which are less than the geometrized length of the mass of the object, this solution produces black holes with two event horizons.

    The Kerr solution for rotating massive objects. This solution also produces black holes with multiple event horizons.

    The Kerr-Newman solution for charged, rotating massive objects. This solution also produces black holes with multiple event horizons.

    The cosmological Friedmann-Lemaître-Robertson-Walker solution, which predicts the expansion of the universe.

Tests

The tests of general relativity included the following:[9]

    General relativity accounts for the anomalous perihelion precession of Mercury.[10]

    The prediction that time runs slower at lower potentials (gravitational time dilation) has been confirmed by the Pound–Rebka experiment (1959), the Hafele–Keating experiment, and the GPS.

    The prediction of the deflection of light was first confirmed by Arthur Stanley Eddington from his observations during the Solar eclipse of May 29, 1919.[11][12] Eddington measured starlight deflections twice those predicted by Newtonian corpuscular theory, in accordance with the predictions of general relativity. However, his interpretation of the results was later disputed.[13]
More recent tests using radio interferometric measurements of quasars passing behind the Sun have more accurately and consistently confirmed the deflection of light to the degree predicted by general relativity.[14]
See also gravitational lens.

    The time delay of light passing close to a massive object was first identified by Irwin I. Shapiro in 1964 in interplanetary spacecraft signals.

    Gravitational radiation has been indirectly confirmed through studies of binary pulsars.

    Alexander Friedmann in 1922 found that Einstein equations have non-stationary solutions (even in the presence of the cosmological constant). In 1927 Georges Lemaître showed that static solutions of the Einstein equations, which are possible in the presence of the cosmological constant, are unstable, and therefore the static universe envisioned by Einstein could not exist. Later, in 1931, Einstein himself agreed with the results of Friedmann and Lemaître. Thus general relativity predicted that the Universe had to be non-static—it had to either expand or contract. The expansion of the universe discovered by Edwin Hubble in 1929 confirmed this prediction.[15]

    The theory's prediction of frame dragging was consistent with the recent Gravity Probe B results.[16]

    General relativity predicts that light should lose its energy when traveling away from massive bodies through gravitational redshift. This was verified on earth and in the solar system around 1960.

Gravity and quantum mechanics

https://en.wikipedia.org/wiki/Graviton

https://en.wikipedia.org/wiki/Quantum_gravity

In the decades after the discovery of general relativity, it was realized that general relativity is incompatible with quantum mechanics.[17] It is possible to describe gravity in the framework of quantum field theory like the other fundamental forces, such that the attractive force of gravity arises due to exchange of virtual gravitons, in the same way as the electromagnetic force arises from exchange of virtual photons.[18][19] This reproduces general relativity in the classical limit. However, this approach fails at short distances of the order of the Planck length,[17] where a more complete theory of quantum gravity (or a new approach to quantum mechanics) is required.

Specifics

https://en.wikipedia.org/wiki/Gravity_of_Earth

Earth's gravity

Every planetary body (including the Earth) is surrounded by its own gravitational field, which can be conceptualized with Newtonian physics as exerting an attractive force on all objects. Assuming a spherically symmetrical planet, the strength of this field at any given point above the surface is proportional to the planetary body's mass and inversely proportional to the square of the distance from the center of the body.

The strength of the gravitational field is numerically equal to the acceleration of objects under its influence.[citation needed] The rate of acceleration of falling objects near the Earth's surface varies very slightly depending on latitude, surface features such as mountains and ridges, and perhaps unusually high or low sub-surface densities.[20] For purposes of weights and measures, a standard gravity value is defined by the International Bureau of Weights and Measures, under the International System of Units (SI).

That value, denoted g, is g = 9.80665 m/s2 (32.1740 ft/s2).[21][22]

The standard value of 9.80665 m/s2 is the one originally adopted by the International Committee on Weights and Measures in 1901 for 45° latitude, even though it has been shown to be too high by about five parts in ten thousand.[23] This value has persisted in meteorology and in some standard atmospheres as the value for 45° latitude even though it applies more precisely to latitude of 45°32'33".[24]

Assuming the standardized value for g and ignoring air resistance, this means that an object falling freely near the Earth's surface increases its velocity by 9.80665 m/s (32.1740 ft/s or 22 mph) for each second of its descent. Thus, an object starting from rest will attain a velocity of 9.80665 m/s (32.1740 ft/s) after one second, approximately 19.62 m/s (64.4 ft/s) after two seconds, and so on, adding 9.80665 m/s (32.1740 ft/s) to each resulting velocity. Also, again ignoring air resistance, any and all objects, when dropped from the same height, will hit the ground at the same time.
If an object with comparable mass to that of the Earth were to fall towards it, then the corresponding acceleration of the Earth would be observable.

According to Newton's 3rd Law, the Earth itself experiences a force equal in magnitude and opposite in direction to that which it exerts on a falling object. This means that the Earth also accelerates towards the object until they collide. Because the mass of the Earth is huge, however, the acceleration imparted to the Earth by this opposite force is negligible in comparison to the object's. If the object doesn't bounce after it has collided with the Earth, each of them then exerts a repulsive contact force on the other which effectively balances the attractive force of gravity and prevents further acceleration.

The force of gravity on Earth is the resultant (vector sum) of two forces:[dubious – discuss][citation needed] (a) The gravitational attraction in accordance with Newton's universal law of gravitation, and (b) the centrifugal force[dubious – discuss][citation needed], which results from the choice of an earthbound, rotating frame of reference. At the equator, the force of gravity is the weakest due to the centrifugal force caused by the Earth's rotation. The force of gravity varies with latitude and increases from about 9.780 m/s2 at the Equator to about 9.832 m/s2 at the poles.

Equations for a falling body near the surface of the Earth

https://en.wikipedia.org/wiki/Equations_for_a_falling_body

Under an assumption of constant gravitational attraction, Newton's law of universal gravitation simplifies to F = mg, where m is the mass of the body and g is a constant vector with an average magnitude of 9.81 m/s2 on Earth. This resulting force is the object's weight. The acceleration due to gravity is equal to this g. An initially stationary object which is allowed to fall freely under gravity drops a distance which is proportional to the square of the elapsed time. The image on the right, spanning half a second, was captured with a stroboscopic flash at 20 flashes per second. During the first 1⁄20 of a second the ball drops one unit of distance (here, a unit is about 12 mm); by 2⁄20 it has dropped at total of 4 units; by 3⁄20, 9 units and so on.

Under the same constant gravity assumptions, the potential energy, Ep, of a body at height h is given by Ep = mgh (or Ep = Wh, with W meaning weight). This expression is valid only over small distances h from the surface of the Earth. Similarly, the expression h = \tfrac{v^2}{2g} for the maximum height reached by a vertically projected body with initial velocity v is useful for small heights and small initial velocities only.

Gravity and astronomy

The application of Newton's law of gravity has enabled the acquisition of much of the detailed information we have about the planets in the Solar System, the mass of the Sun, and details of quasars; even the existence of dark matter is inferred using Newton's law of gravity. Although we have not traveled to all the planets nor to the Sun, we know their masses. These masses are obtained by applying the laws of gravity to the measured characteristics of the orbit. In space an object maintains its orbit because of the force of gravity acting upon it. Planets orbit stars, stars orbit galactic centers, galaxies orbit a center of mass in clusters, and clusters orbit in superclusters. The force of gravity exerted on one object by another is directly proportional to the product of those objects' masses and inversely proportional to the square of the distance between them.

Gravitational radiation

https://en.wikipedia.org/wiki/Gravitational_wave

In general relativity, gravitational radiation is generated in situations where the curvature of spacetime is oscillating, such as is the case with co-orbiting objects. The gravitational radiation emitted by the Solar System is far too small to measure. However, gravitational radiation has been indirectly observed as an energy loss over time in binary pulsar systems such as PSR B1913+16. It is believed that neutron star mergers and black hole formation may create detectable amounts of gravitational radiation. Gravitational radiation observatories such as the Laser Interferometer Gravitational Wave Observatory (LIGO) have been created to study the problem. No confirmed detections have been made of this hypothetical radiation.

Speed of gravity

https://en.wikipedia.org/wiki/Speed_of_gravity

In December 2012, a research team in China announced that it had produced measurements of the phase lag of Earth tides during full and new moons which seem to prove that the speed of gravity is equal to the speed of light.[26] This means that if the Sun suddenly disappeared, the Earth would keep orbiting it normally for 8 minutes, which is the time light takes to travel that distance. The team's findings were released in the Chinese Science Bulletin in February 2013.[27]

Anomalies and discrepancies

There are some observations that are not adequately accounted for, which may point to the need for better theories of gravity or perhaps be explained in other ways.


    Extra-fast stars: Stars in galaxies follow a distribution of velocities where stars on the outskirts are moving faster than they should according to the observed distributions of normal matter. Galaxies within galaxy clusters show a similar pattern. Dark matter, which would interact gravitationally but not electromagnetically, would account for the discrepancy. Various modifications to Newtonian dynamics have also been proposed.

    Flyby anomaly: Various spacecraft have experienced greater acceleration than expected during gravity assist maneuvers.

    Accelerating expansion: The metric expansion of space seems to be speeding up. Dark energy has been proposed to explain this. A recent alternative explanation is that the geometry of space is not homogeneous (due to clusters of galaxies) and that when the data are reinterpreted to take this into account, the expansion is not speeding up after all,[28] however this conclusion is disputed.[29]

    Anomalous increase of the astronomical unit: Recent measurements indicate that planetary orbits are widening faster than if this were solely through the Sun losing mass by radiating energy.

    Extra energetic photons: Photons travelling through galaxy clusters should gain energy and then lose it again on the way out. The accelerating expansion of the universe should stop the photons returning all the energy, but even taking this into account photons from the cosmic microwave background radiation gain twice as much energy as expected. This may indicate that gravity falls off faster than inverse-squared at certain distance scales.[30]

    Extra massive hydrogen clouds: The spectral lines of the Lyman-alpha forest suggest that hydrogen clouds are more clumped together at certain scales than expected and, like dark flow, may indicate that gravity falls off slower than inverse-squared at certain distance scales.[30]

    Power: Proposed extra dimensions could explain why the gravity force is so weak.[31]

Alternative theories


https://en.wikipedia.org/wiki/Alternatives_to_general_relativity


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There are two 'types' of gravity forces..

Newton's law of universal gravitation

https://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

Newton's law of universal gravitation states that any two bodies in the Universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.[note 1] This is a general physical law derived from empirical observations by what Isaac Newton called induction.[1] It is a part of classical mechanics and was formulated in Newton's work Philosophiæ Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him; see the History section below.)

In modern language, the law states: Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them.[2] The first test of Newton's theory of gravitation between masses in the laboratory was the Cavendish experiment conducted by the British scientist Henry Cavendish in 1798.[3] It took place 111 years after the publication of Newton's Principia and 71 years after his death.

Newton's law of gravitation resembles Coulomb's law of electrical forces, which is used to calculate the magnitude of electrical force arising between two charged bodies. Both are inverse-square laws, where force is inversely proportional to the square of the distance between the bodies. Coulomb's law has the product of two charges in place of the product of the masses, and the electrostatic constant in place of the gravitational constant.

Newton's law has since been superseded by Einstein's theory of general relativity, but it continues to be used as an excellent approximation of the effects of gravity in most applications. Relativity is required only when there is a need for extreme precision, or when dealing with very strong gravitational fields, such as those found near extremely massive and dense objects, or at very close distances (such as Mercury's orbit around the sun).

Standard gravity

https://en.wikipedia.org/wiki/Standard_gravity

The standard acceleration due to gravity (or standard acceleration of free fall), sometimes abbreviated as standard gravity, usually denoted by ɡ0 or ɡn, is the nominal gravitational acceleration of an object in a vacuum near the surface of the Earth. It is defined by standard as 9.80665 m/s2, which is exactly 35.30394 km/(h·s) (about 32.174 ft/s2, or 21.937 mph/s). This value was established by the 3rd CGPM (1901, CR 70) and used to define the standard weight of an object as the product of its mass and this nominal acceleration.[1][2] The acceleration of a body near the surface of the Earth is due to the combined effects of gravity and centrifugal acceleration from rotation of the Earth (but which is small enough to be neglected for most purposes); the total (the apparent gravity) is about 0.5 percent greater at the poles than at the equator.

Although the symbol ɡ is sometimes used for standard gravity, ɡ (without a suffix) can also mean the local acceleration due to local gravity and centrifugal acceleration, which varies depending on one's position on Earth (see Earth's gravity). The symbol ɡ should not be confused with G, the gravitational constant, or g, the symbol for gram. The ɡ is also used as a unit for any form of acceleration, with the value defined as above; see g-force.

The value of ɡ0 defined above is a nominal midrange value on Earth, originally based on the acceleration of a body in free fall at sea level at a geodetic latitude of 45°. Although the actual acceleration of free fall on Earth varies according to location, the above standard figure is always used for metrological purposes. In particular, it gives the conversion factor between newton and kilogram-force, two units of force.


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Relative density

https://en.wikipedia.org/wiki/Relative_density

Relative density, or specific gravity,[1][2] is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water. The term "relative density" is often preferred in modern scientific usage. It is defined as a ratio of density of particular substance with that of water.

If a substance's relative density is less than one then it is less dense than the reference; if greater than 1 then it is denser than the reference. If the relative density is exactly 1 then the densities are equal; that is, equal volumes of the two substances have the same mass. If the reference material is water then a substance with a relative density (or specific gravity) less than 1 will float in water. For example, an ice cube, with a relative density of about 0.91, will float. A substance with a relative density greater than 1 will sink.

Temperature and pressure must be specified for both the sample and the reference. Pressure is nearly always 1 atm (101.325 kPa). Where it is not, it is more usual to specify the density directly. Temperatures for both sample and reference vary from industry to industry. In British brewing practice the specific gravity as specified above is multiplied by 1000.[3] Specific gravity is commonly used in industry as a simple means of obtaining information about the concentration of solutions of various materials such as brines, sugar solutions (syrups, juices, honeys, brewers wort, must, etc.) and acids.

Hydrostatic weighing


https://en.wikipedia.org/wiki/Hydrostatic_weighing

Hydrostatic weighing, also referred to as "underwater weighing," "hydrostatic body composition analysis," and "hydrodensitometry," is a technique for measuring the mass per unit volume of a living person's body. It is a direct application of Archimedes' principle, that an object displaces its own volume of water.

Method

The procedure is based on Archimedes' principle, which states that: The buoyant force which water exerts on an immersed object is equal to the weight of water that the object displaces.

Hydrometer

https://en.wikipedia.org/wiki/Hydrometer

A hydrometer is an instrument that measures the specific gravity (relative density) of liquids—the ratio of the density of the liquid to the density of water.

A hydrometer is usually made of glass, and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright. The liquid to test is poured into a tall container, often a graduated cylinder, and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer correlates to specific gravity. Hydrometers usually contain a scale inside the stem, so that the person using it can read specific gravity . A variety of scales exist for different contexts.

Hydrometers are calibrated for different uses, such as a lactometer for measuring the density (creaminess) of milk, a saccharometer for measuring the density of sugar in a liquid, or an alcoholometer for measuring higher levels of alcohol in spirits.


---------------------------
Everyman Standing Order 01: In the Face of Tyranny; Everybody Stands, Nobody Runs.
Everyman Standing Order 02: Everyman is Responsible for Energy and Security.
Everyman Standing Order 03: Everyman knows Timing is Critical in any Movement.
   
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