# Question about gravity **URL:** \ **Category:** Factual Questions\ **Created:** [March 28, 2003, 12:09am UTC](https://boards.straightdope.com/t/question-about-gravity/164656 "2003-03-28T00:09:35Z")\ **Posts on this page:** 11\ **Page:** 2
**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:** [March 28, 2003, 9:47pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/21 "2003-03-28T21:47:29Z")
It would indeed. Then a lot of experiments could be done right here on Earth without the expense of a space launch. Maybe someday. No one has yet said such a thing is impossible. But we have no idea how to do it, currently, if it _is_ possible, ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [March 28, 2003, 9:56pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/22 "2003-03-28T21:56:02Z")
If you were to hollow out the Earth’s core you would have pretty much zero G as gravity would exactly cancel out (assuming the Earth is a perfect sphere which it blatantly is not) wherever you were in the hollow region (assuming the hollow region was spherical and centred around the Earth’s centre of gravity). ---
**Author:** ![Sock\_Munkey](https://avatars.discourse-cdn.com/v4/letter/s/aeb1de/32.png) [@Sock\_Munkey](https://boards.straightdope.com/u/Sock_Munkey)\ **Post date:** [March 29, 2003, 12:15pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/23 "2003-03-29T12:15:58Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*It would indeed. Then a lot of experiments could be done right here on Earth without the expense of a space launch. Maybe someday. No one has yet said such a thing is impossible. But we have no idea how to do it, currently, if it _is_ possible, \*\* That’s one of the reasons why people are working on the magnetic field device they levitated the frog with, it’s really expensive since it uses enough power to light a city but that’s still much cheaper than a space launch. ---
**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:** [March 29, 2003, 4:33pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/24 "2003-03-29T16:33:46Z")
I think that HighSoci is misunderstanding a fundamental concept about gravity. From the OP, it appears he/she thinks that no atmosphere = zero-G. Which, of course, is untrue. IANA Physicist, but to oversimplify, gravity lends it’s ‘sucking’ attributes to MASS, not atmosphere. Therefore, we?re stuck to this planet, because the mass of the planet earth is enormous, not because the earth has an atmosphere (which, of course adds itself to the total mass of the earth, but that?s not entirely the point). Likewise, just because we are outside the atmosphere of the earth, THIS is not what causes zero-G. It is actually because the astronauts and everything around them are essentially free falling around the planet. Which in turn, cancels out the effects of the earth’s gravity (just as if you jumped off a cliff). If they were to slow down, gravity would then take hold, and pull them toward the surface. If you can understand those key points, you should then be able to see why constructing a zero-G room within such a strong gravity well as the earth would be a very difficult task. Hope this helps… -kev ---
**Author:** ![HighSoci](https://avatars.discourse-cdn.com/v4/letter/h/ba8739/32.png) [@HighSoci](https://boards.straightdope.com/u/HighSoci)\ **Post date:** [March 29, 2003, 5:14pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/25 "2003-03-29T17:14:55Z")
Thanks, that helps a lot, but what about vacuum? Couldn’t it be possible to create a zero gravity enviroment by creating a vacuum in it? ---
**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:** [March 29, 2003, 5:30pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/26 "2003-03-29T17:30:05Z")
No, just look at the old Moon landing videos. There’s clearly gravity there, although it’s 1/6 that of Earth’s surface gravity; yet there is a pretty darn good vacuum. Again, it’s the _mass_, or the amount of material in an object that creates gravity. The Earth’s atmosphere exists and has pressure _because_ the Earth has gravity, not the other way around. ---
**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:** [March 29, 2003, 6:08pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/27 "2003-03-29T18:08:46Z")
To suck all the air out of a room (essentially a vacuum), will not produce a zero-G environ. As Q.E.D said, the reason we have the atmosphere (and pressure) we do at all is BECAUSE of the earth’s gravity. Gravity is pulling down on the atoms & molecules in the air just like it’s pulling down on you, and keeping in a blanket around the earth. Where does this gravity come from? It is the net effect of all the mass and matter of the earth itself. Matter attracts matter, and if you get enough of it together in one lump, you get a substantial amount of gravity, that makes it harder and harder to escape from. The Moon (which has gravity itself… although less than the earth because it’s smaller) is tethered to the earth because of earth’s gravity, just like you, me and the air around us. Plenty of people have produced the vacuums you are imagining, but it does not produce any type of anti-gravity effect. In fact, it would allow gravity to display its FULL effect, by eliminating air resistance. For example, if you could drop a feather and a brick in a vacuum, from any height, you would find that they would hit the ground at the exact same time. The feather would fall just as fast as the brick do to no friction on the feather from the air. So you see, a vacuum is not a requirement for zero-G, and that is how astronauts can breath in orbit (or even in the deep of sapce). ---
**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:** [March 29, 2003, 6:13pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/28 "2003-03-29T18:13:25Z")
maybe this would make more sense if i didn’t spell like a two-year old. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [March 29, 2003, 9:46pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/29 "2003-03-29T21:46:35Z")
> [@](#): > > \*Originally posted by HighSoci \* > **Doesn’t NASA have an actual room that has zero gravity?** Yes, for short periods of time. > [@](#): > > \*Originally posted by Achernar \* > **NASA has no such room.** You may have missed [this one](http://microgravity.grc.nasa.gov/zero-g/zero_descript.html), it’s fairly recent. 🙂 > [@](#): > > \*Originally posted by Q.E.D. \* > **No, the only zero-G environments NASA has are the so-called “Vomit Comet” and vehicles in Earth orbit.** The zero-g ground based facility has many of the features of the Vomit Comet. ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [March 29, 2003, 10:27pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/30 "2003-03-29T22:27:21Z")
You’re right, I didn’t know about that, and that is pretty cool. But it was clear that that’s not the kind of thing that **HighSoci** was asking about. 🙂 ---
**Author:** ![HighSoci](https://avatars.discourse-cdn.com/v4/letter/h/ba8739/32.png) [@HighSoci](https://boards.straightdope.com/u/HighSoci)\ **Post date:** [March 29, 2003, 10:33pm UTC](https://boards.straightdope.com/t/question-about-gravity/164656/31 "2003-03-29T22:33:29Z")
Great reading. Thanks for all the info. [Previous page](https://boards.straightdope.com/t/question-about-gravity/164656.md?page=1)