# Gravitoreceptors? **URL:** \ **Category:** Factual Questions\ **Created:** [October 19, 2006, 4:44pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109 "2006-10-19T16:44:09Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [October 19, 2006, 4:44pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/1 "2006-10-19T16:44:09Z")
The carrier of the Electromagnetic Force is the Photon The carrier of the Gravitational Force is the ( theoretical ) Graviton. Photoreceptors…solar panels, photovoltaics and the like…absorb light and convert it into useable energy. Theoretically, can the same be said a panel to interact with radiant gravity? ---
**Author:** ![bouv](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@bouv](https://boards.straightdope.com/u/bouv)\ **Post date:** [October 19, 2006, 5:06pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/2 "2006-10-19T17:06:51Z")
Well, seeing as we have no idea if gravitons actually exist, it’d be pretty darn hard to make something that can create energy out of them. However, we certianly can use gravity to make energy, just drop something. ---
**Author:** ![Crescend](https://avatars.discourse-cdn.com/v4/letter/c/b9bd4f/32.png) [@Crescend](https://boards.straightdope.com/u/Crescend)\ **Post date:** [October 19, 2006, 5:12pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/3 "2006-10-19T17:12:52Z")
[QUOTE=bouv] However, we certianly can use gravity to make energy, just drop something. [/QUOTE] And any tidal-power station gets its energy, in the end, from gravity. (Hydroelectric doesn’t count - the ultimate source of energy for hydro is the solar heat-driven evaporation/condensation cycle.) ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 19, 2006, 5:13pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/4 "2006-10-19T17:13:37Z")
[LIGO](http://en.wikipedia.org/wiki/LIGO) > [@](#): > > Based on current models of astronomical events, and the predictions of the general theory of relativity, gravitational waves that originate tens of millions of light years from Earth are expected to distort the 4 kilometer mirror spacing by about 10-18 m, less than one-thousandth the “diameter” of a proton. Equivalently, this is a relative change in distance of approximately one part in 10^21. [LIGO Site](http://www.ligo.caltech.edu/LIGO_web/about/) ---
**Author:** ![Crescend](https://avatars.discourse-cdn.com/v4/letter/c/b9bd4f/32.png) [@Crescend](https://boards.straightdope.com/u/Crescend)\ **Post date:** [October 19, 2006, 5:24pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/5 "2006-10-19T17:24:40Z")
[QUOTE=Squink] [LIGO](http://en.wikipedia.org/wiki/LIGO) [LIGO Site](http://www.ligo.caltech.edu/LIGO_web/about/) [/QUOTE] Not much energy in distantly emitted gravity waves, that is. Which is reasonable, since the strength of gravity does fall off as the inverse square of the distance. Even a black hole isn’t much when it’s that far away. On the other hand, the sun and moon are quite close, and their local contribution outshines the others by far. I heard some rumors that LIGO needed to be tuned to avoid being overwhelmed by local gravity effects (Earth’s mantle shifting, etc) and neighborhood effects, like the Jovian system, the Sun, the tides, etc. Can’t substantiate these, of course. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 19, 2006, 5:36pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/6 "2006-10-19T17:36:58Z")
It’s very difficult to even detect gravitons at all. We may never detect an individual graviton; the task is of such a difficulty that it might be the type of thing a Type III civilization does to show off (and we probably won’t ever reach a Type III civilization). Streams of a great many gravitons (otherwise known as gravitational waves) aren’t quite so bad; we currently have several projects in the works to detect them. None of them have worked yet, but within the decade, the [LIGO](http://www.ligo.caltech.edu/) detector should be improved enough that it’ll be able to detect something, and (supposedly) in the same timeframe, [LISA](http://lisa.jpl.nasa.gov/) should be launched and also detect something. Both of these detectors work by having widely-separated and highly isolated masses, with lasers precisely measuring the distances between them. If a gravitational wave passes through, it’ll move the masses slightly, causing the distances to change in a particular pattern. In principle, this moving of the masses is extracting some energy from the gravitational wave, but the distances by which they’d be moved is a tiny fraction of the size of an atom, so the amount of energy is inconceivably miniscule. You might be able to extract some meaningful amount of energy if you were, say, within a few radii of a pair of colliding black holes, but even there, there would be far, far easier ways to transmit and receive energy. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [October 19, 2006, 5:38pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/7 "2006-10-19T17:38:35Z")
[QUOTE=Crescend] And any tidal-power station gets its energy, in the end, from gravity. (Hydroelectric doesn’t count - the ultimate source of energy for hydro is the solar heat-driven evaporation/condensation cycle.) [/QUOTE] I don’t quite understand the distinction. All water is involved in the solar evaporation/condensation cycle. A hydroelectric power plant certainly does work on gravity. Water runs downhill into streams and rivers. We build a dam to make a very deep tank to develop gravitational pressure which, squirted through turbines, makes electricity. It was gravity that pulled the water downhill into the lake. Similarly, gravity powers the tides, and we can build things to force the tidal water through turbines. Perhaps I have misunderstood your statements. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 19, 2006, 5:46pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/8 "2006-10-19T17:46:26Z")
> [@](#): > > On the other hand, the sun and moon are quite close, and their local contribution outshines the others by far. I heard some rumors that LIGO needed to be tuned to avoid being overwhelmed by local gravity effects (Earth’s mantle shifting, etc) and neighborhood effects, like the Jovian system, the Sun, the tides, etc. Can’t substantiate these, of course. This wasn’t here when I started typing. Yes, LIGO (or the programs used to analyze the data) needs to be calibrated to take into account gravitational effects from objects in the Solar System. There are a lot more such objects than you’d think: Even a tumbleweed blowing past the detector can produce a non-negligible amount of gravitational noise. But these aren’t gravitational **wave** effects. Although gravity falls off as 1/r[sup]2[/sup], the waves (at least, the way we detect them) fall off as only 1/r, so a large, distant source can be much more significant than a small, nearby source. If I recall correctly, the first sources expected to be detected by LIGO are supermassive black hole mergers, which could be clear across the Universe. ---
**Author:** ![Crescend](https://avatars.discourse-cdn.com/v4/letter/c/b9bd4f/32.png) [@Crescend](https://boards.straightdope.com/u/Crescend)\ **Post date:** [October 19, 2006, 5:48pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/9 "2006-10-19T17:48:05Z")
[QUOTE=AskNott] I don’t quite understand the distinction. All water is involved in the solar evaporation/condensation cycle. A hydroelectric power plant certainly does work on gravity. Water runs downhill into streams and rivers. We build a dam to make a very deep tank to develop gravitational pressure which, squirted through turbines, makes electricity. It was gravity that pulled the water downhill into the lake. Similarly, gravity powers the tides, and we can build things to force the tidal water through turbines. Perhaps I have misunderstood your statements. [/QUOTE] I made that distinction because if there was no evaporation/condensation cycle, once all the water came downhill, no more energy would be generated by the turbine. On the other hand, given a sufficiently large reservoir and a tidal generator, energy can be produced as long as tides push and pull on the water. No evaporation/condensation cycle needed. Gravity is used in both systems, but in the case of the hydroelectric plant, gravity doesn’t lift the water above the turbine - the evaporation/condensation cycle does. And that cycle is powered by the sun’s heat. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 19, 2006, 5:49pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/10 "2006-10-19T17:49:23Z")
[QUOTE=AskNott] I don’t quite understand the distinction. All water is involved in the solar evaporation/condensation cycle. A hydroelectric power plant certainly does work on gravity. [/QUOTE] Gravity is not a source of energy. One could argue, in fact, that tidal power gets its energy, not from gravity, but from the rotational energy of the Earth. In hydro power, the energy comes from the Sun; gravity is only the mechanism by which the potential energy of the water is converted to kinetic energy. ---
**Author:** ![Crescend](https://avatars.discourse-cdn.com/v4/letter/c/b9bd4f/32.png) [@Crescend](https://boards.straightdope.com/u/Crescend)\ **Post date:** [October 19, 2006, 5:49pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/11 "2006-10-19T17:49:42Z")
[QUOTE=Chronos] This wasn’t here when I started typing. Yes, LIGO (or the programs used to analyze the data) needs to be calibrated to take into account gravitational effects from objects in the Solar System. There are a lot more such objects than you’d think: Even a tumbleweed blowing past the detector can produce a non-negligible amount of gravitational noise. But these aren’t gravitational **wave** effects. Although gravity falls off as 1/r[sup]2[/sup], the waves (at least, the way we detect them) fall off as only 1/r, so a large, distant source can be much more significant than a small, nearby source. If I recall correctly, the first sources expected to be detected by LIGO are supermassive black hole mergers, which could be clear across the Universe. [/QUOTE] Ah, I see. My ignorance has been fought. ---
**Author:** ![Crescend](https://avatars.discourse-cdn.com/v4/letter/c/b9bd4f/32.png) [@Crescend](https://boards.straightdope.com/u/Crescend)\ **Post date:** [October 19, 2006, 5:52pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/12 "2006-10-19T17:52:50Z")
[QUOTE=Q.E.D.] Gravity is not a source of energy. One could argue, in fact, that tidal power gets its energy, not from gravity, but from the rotational energy of the Earth. [/QUOTE] What induced that rotation in the first place? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 19, 2006, 5:57pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/13 "2006-10-19T17:57:37Z")
[QUOTE=Crescend] What induced that rotation in the first place? [/QUOTE] Good question. I can see a good case being made for that energy originating in the Big Bang itself, in the form of residual angular momentum. It’s why nearly everything in the Universe spins. ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [October 19, 2006, 6:25pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/14 "2006-10-19T18:25:42Z")
[QUOTE=bouv] However, we certianly can use gravity to make energy, just drop something. [/QUOTE] Something heavy on your toes and see how much energy you generate! ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [October 19, 2006, 6:44pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/15 "2006-10-19T18:44:43Z")
[QUOTE=Q.E.D.] Gravity is not a source of energy. One could argue, in fact, that tidal power gets its energy, not from gravity, but from the rotational energy of the Earth. In hydro power, the energy comes from the Sun; gravity is only the mechanism by which the potential energy of the water is converted to kinetic energy. [/QUOTE] I think a lot of confusion comes in from the terminology. When I read that originally [QUOTE=Crescend] And any tidal-power station gets its energy, in the end, from gravity. [/QUOTE] I wanted to post that gravity is not a form of energy, but a force. Aside from the matter of the sun actually providing the energy (potential to kinetic) of falling/sloping water, gravity provides the force. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 19, 2006, 6:53pm UTC](https://boards.straightdope.com/t/gravitoreceptors/377109/16 "2006-10-19T18:53:03Z")
[QUOTE=CC] I think a lot of confusion comes in from the terminology. When I read that originally I wanted to post that gravity is not a form of energy, but a force. Aside from the matter of the sun actually providing the energy (potential to kinetic) of falling/sloping water, gravity provides the force. [/QUOTE] Quite right. 🙂