# Can someone explain me gravity? **URL:** \ **Category:** Factual Questions\ **Created:** [August 15, 2010, 6:53am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314 "2010-08-15T06:53:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 15, 2010, 6:53am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/1 "2010-08-15T06:53:41Z")
Another question: Would Meissner’s frog experience G-forces if rapidly accelerated? ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [August 15, 2010, 7:38am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/2 "2010-08-15T07:38:13Z")
Unless there’s something special about Meissner’s frog (is there another thread this is referencing?) then yes the frog experiences G-forces. The frog, and anything else, experiences G-forces if accelerated at all, it doesn’t have to be rapid but the greater the acceleration the greater the G-forces. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 15, 2010, 8:32am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/3 "2010-08-15T08:32:42Z")
I think the OP is talking about experiments where a live frog is levitated by magnetic fields employing - there’s a bit about it on the Wiki page about magnetic levitation: > **[Magnetic levitation](https://en.wikipedia.org/wiki/Magnetic_levitation)** > > Magnetic levitation (maglev) or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational force and any other forces. > The two primary issues involved in magnetic levitation are lifting forces: providing an upward force sufficient to counteract gravity, and stability: ensuring that the system does not spontaneously slide or flip into a configuration where the lift is neutralized... The magnetic levitation isn’t making gravity go away, it’s just adding forces that happen to balance it out - add some more forces and the frog will feel it. ---
**Author:** ![qpw3141](https://avatars.discourse-cdn.com/v4/letter/q/6bbea6/32.png) [@qpw3141](https://boards.straightdope.com/u/qpw3141)\ **Post date:** [August 15, 2010, 8:36am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/4 "2010-08-15T08:36:47Z")
**Can someone explain me gravity?** No such thing as gravity - the Earth sucks. ---
**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\ **Post date:** [August 15, 2010, 11:47am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/5 "2010-08-15T11:47:18Z")
Jeffy from _the Family Circus_ has pretty much [explained gravity](http://a.imageshack.us/img707/5700/familycircus1610.jpg) ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 15, 2010, 12:08pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/6 "2010-08-15T12:08:38Z")
The magnetically levitating frog (or anything else) would experience G-forces in the direction of travel, barring the device isn’t compensating for the acceleration. It would then disrupt the fine balance the magnetism is performing, and the frog wouldn’t levitate anymore. Gravity is a property of mass. The more mass you have, the greater the gravity. The greater the gravity, the more it warps space-time around it, thereby curving anything else with mass in its field toward, around or into it. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [August 15, 2010, 3:20pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/7 "2010-08-15T15:20:05Z")
The levitated frog experiences gravity, just like you do when you’re standing on the floor. If the frog is fat, his belly still sags. You are held up by the electromagnetic force of the floor on your feet. The frog is held up by the magnetic field. Both of you will experience g-forces when accelerated. Newton explained gravity as a universal force between all objects, whose strength is proportional to the product of the objects masses and inversely proportional to the their separation distance. Einstein’s theory of general relativity refined Newton’s theory and explained gravity as the result of curvature in the four dimensions of space and time. A fundamental tenet of Einstein’s theory is the “equivalence principal,” which holds that gravitational force is equivalent to acceleration, thus if the frog accelerates, it experiences g-forces. To explain all of this in detail would take far more words than practical for this column, but there are many good resources on the Internet. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 15, 2010, 3:32pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/8 "2010-08-15T15:32:17Z")
I believe I made an error, gravity effects massless particles too, like photons. ---
**Author:** ![Yodalicious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yodalicious/32/8195_2.png) [@Yodalicious](https://boards.straightdope.com/u/Yodalicious)\ **Post date:** [August 15, 2010, 3:50pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/9 "2010-08-15T15:50:15Z")
No such thing as gravity. Its [Intelligent Falling](http://www.theonion.com/articles/evangelical-scientists-refute-gravity-with-new-int,1778/). ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 15, 2010, 6:09pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/10 "2010-08-15T18:09:00Z")
I really could not read the whole article. The laws of Physics happen - period. Written laws may change, though. Einstein predicted the speed of gravity to be what is now measured, that is the speed of light. Can you tell me why not slower/faster? ---
**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:** [August 15, 2010, 6:41pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/11 "2010-08-15T18:41:26Z")
> [@](#): > > The levitated frog experiences gravity, just like you do when you’re standing on the floor. If the frog is fat, his belly still sags. I’m not so sure about the sagging belly. Magnetic levitation is different from most methods of support, in that it acts on water molecules throughout the body of the frog. Since frogs, like all living things, are mostly water, this provides a very uniformly-distributed force. The net effect is that, if the frog were accelerated, provided that the magnetic field were adjusted to compensate, it should have much less effect on the frog than most accelerations. Consider a typical case where high acceleration _does_ cause damage, like when the ground accelerates you at the end of a long fall. The reason that causes damage is that the bits of you that hit the ground stop moving immediately, but the internal bits of you, and the external parts on the other side, keep on moving for a little while. It’s the fact that different parts of you have different accelerations that causes problems, not the acceleration per se. But with the levitating frog, all parts of it do have close to the same acceleration. Quoth **komolono** : > [@](#): > > Einstein predicted the speed of gravity to be what is now measured, that is the speed of light. Can you tell me why not slower/faster? The simplest answer is that that’s the only speed that exists in the Universe. All other speeds depend on your reference frame, but gravity, as described by Einstein, doesn’t have any particular reference frame, so whenever a speed shows up, there’s only one speed it could be. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [August 15, 2010, 7:33pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/12 "2010-08-15T19:33:00Z")
> [@Chronos](#): > > I’m not so sure about the sagging belly. Magnetic levitation is different from most methods of support, in that it acts on water molecules throughout the body of the frog. Good point, my bad. ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 16, 2010, 9:06am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/13 "2010-08-16T09:06:22Z")
[quote=“Chronos, post:11, topic:550314”] > [@](#): > > net effect is that, if the frog were accelerated, provided that the magnetic field were adjusted to compensate, it should have much less effect on the frog than most accelerations. Now, if you move the magnet the frog moves - yes? This should be easily tested. Could this be another form of transportation in the future? Let the sorry Maglex-frog earn it’s name in history! ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [August 16, 2010, 10:08am UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/14 "2010-08-16T10:08:05Z")
> [@komolono](#): > > Einstein predicted the speed of gravity to be what is now measured, that is the speed of light. Can you tell me why not slower/faster? Has it really been measured? I thought that was still a huge technical challenge? ---
**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:** [August 16, 2010, 4:56pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/15 "2010-08-16T16:56:30Z")
It sounds like the OP just read some article on gravity, which might have mentioned a measurement of the speed of gravity, and which prompted this thread… But he forgot to include a link to the article he read. Hopefully he’ll be back to tell us. ---
**Author:** ![Bad\_Astronaut](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bad\_Astronaut](https://boards.straightdope.com/u/Bad_Astronaut)\ **Post date:** [August 16, 2010, 11:27pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/16 "2010-08-16T23:27:20Z")
[quote=“komolono, post:13, topic:550314”] > [@Chronos](#): > > Now, if you move the magnet the frog moves - yes? This should be easily tested. Could this be another form of transportation in the future? Let the sorry Maglex-frog earn it’s name in history! I’m pretty sure the magnetic force on the frog only acts in the direction pointing from the magnet to the frog. So if you move the magnet forward, the frog will fall as soon as the magnet is not directly beneath it (and the frog will even be pushed backward a little). ---
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [August 16, 2010, 11:28pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/17 "2010-08-16T23:28:44Z")
> [@Mangetout](#): > > The magnetic levitation isn’t making gravity go away, it’s just adding forces that happen to balance it out Interesting, my chair is doing the exact same thing at this moment. ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 18, 2010, 5:48pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/18 "2010-08-18T17:48:27Z")
Why aren’t there any tides of moon dust? ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 20, 2010, 2:36pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/19 "2010-08-20T14:36:20Z")
> [@Chronos](#): > > It sounds like the OP just read some article on gravity, which might have mentioned a measurement of the speed of gravity, and which prompted this thread… But he forgot to include a link to the article he read. Hopefully he’ll be back to tell us. I thank you for now - I’m sorry I couldn’t find the document about the speed of gravity. It was late last year or early this year on a printed media. Propably one of those popular science magazines with great graphics. There was something about a space probe and Einstein being right. I didn’t find anything similar on the Net. Neither Moondust nor moonshine make tidal waves on the Moon. The locked orbit sort of makes the Moon a tidal wave of the Earth - says JeffJo. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [August 20, 2010, 2:44pm UTC](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314/20 "2010-08-20T14:44:56Z")
The only one I can think of recently (aside from a Jupiter/star transit from a few years back) would be [Gravity Probe B](http://en.wikipedia.org/wiki/Gravity_Probe_B). The Jupiter/star experiment had a thread in GQ though I can’t find it now. [Next page](https://boards.straightdope.com/t/can-someone-explain-me-gravity/550314.md?page=2)