# Artificially created gravity **URL:** \ **Category:** Factual Questions\ **Created:** [May 9, 2017, 9:59pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227 "2017-05-09T21:59:20Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [May 11, 2017, 2:23am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/21 "2017-05-11T02:23:43Z")
> [@Derleth](#): > > As **Chronos** said, this isn’t as absolute as you seem to imagine, but it does touch on points I made: Even though gravity has all the advantages here—it’s always attractive, it works equally well on everything, and everything contributes to it—it still loses to electromagnetism. You still have not mentioned the effects on a living organism though To a point, gravity would appear benign. Until we reach a point or course where the organisms structure simply can not physically withstand it, like say plopping a guy down near Jupiter’s core But we kind of wont kill anyone until we crush them to death. We could have the gravity a little light, we could go a little heavier etc We do know though, that constant exposure to high magnetic fields is not good for things like human beings. And if we got a starship, and everyone is walking around, even if only at say 60% of earth’s gravitational force, that is one very big and very strong field yes? At least strong in regards to what a human is normally exposed to? Exposure to the magnetic fields use in medicine can make you feel dizzy and nauseous and make your mouth taste funny, and that is very brief exposure, and yet not a strong enough field to keep a persons feet on any surface. > [@](#): > > If you move from Newtonian gravity to General Relativity, you find that energy contributes to gravity as well, not just mass. But in everyday circumstances, you can handwave that away and pretend that gravity is purely proportional to the amount of mass. Gravity is energy, of some form, is it not? I mean nothing exists without energy, not even mass. Not sure i quite see what you mean here? ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [May 11, 2017, 2:55am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/22 "2017-05-11T02:55:57Z")
> [@Weisshund](#): > > I would not myself call gravity weak, even the small moon distorts and bulges the earth, the gravity of jupiter has an effect on other planets far from it. > The gravity of the sun itself has long reaching effects. The moon is small? Really. In this solar system, it is the second largest moon relative to its primary. I would say it is huge. The scale of bodies in space is almost incomprehensible. Try this comparison: build an electric generator about the size of that cottage on the lake. Wind it up and go find out what woodland creatures you can vaporize with its electrical output – I venture you could do bigger than elk. Now try to measure its gravity field. I challenge you to get a real measurement. Put two of these generators 100’ apart in space and see if you can wait long enough to see the effects of their gravitational attraction on each other. Pound for pound, gravity is comparatively weak. ---
**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:** [May 11, 2017, 9:55am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/23 "2017-05-11T09:55:45Z")
> [@eschereal](#): > > The moon is small? Really. In this solar system, it is the second largest moon relative to its primary. I would say it is huge. The scale of bodies in space is almost incomprehensible. > > Try this comparison: build an electric generator about the size of that cottage on the lake. Wind it up and go find out what woodland creatures you can vaporize with its electrical output – I venture you could do bigger than elk. Now try to measure its gravity field. I challenge you to get a real measurement. Put two of these generators 100’ apart in space and see if you can wait long enough to see the effects of their gravitational attraction on each other. > > Pound for pound, gravity is comparatively weak. Or, put another way… lifting your foot off the ground, you are overcoming the gravity of a whole planet. Try to push your foot down into the floor, and you are prevented from doing so by the electromagnetic field of a few particles of matter. ---
**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:** [May 11, 2017, 11:12am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/24 "2017-05-11T11:12:44Z")
I’m not sure what point you’re trying to make about the health effects on living organisms. Yes, we can kill things using electromagnetism, but can’t (short of a black hole, which we don’t have) kill things with gravity. That’s just another piece of evidence that electromagnetism is stronger than gravity. Now, what are the health effects of long-term exposure to a strong static magnetic field, like the one that levitated the frog? I don’t think anyone has studied it yet. Might be good, bad, or neutral; we don’t know. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [May 11, 2017, 11:42am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/25 "2017-05-11T11:42:19Z")
> [@Chronos](#): > > Yes, we can kill things using electromagnetism, but can’t (short of a black hole, which we don’t have) kill things with gravity. That’s just another piece of evidence that electromagnetism is stronger than gravity. Maybe gravity is just so secure in its strength that it doesn’t feel the need to lash out by killing things. Unlike electromagnetism, it’s got nothing to prove. 🙂 ---
**Author:** ![coremelt](https://avatars.discourse-cdn.com/v4/letter/c/4491bb/32.png) [@coremelt](https://boards.straightdope.com/u/coremelt)\ **Post date:** [May 11, 2017, 12:02pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/26 "2017-05-11T12:02:19Z")
Well e = mc squared and you can create matter from electromagnetic energy in sufficiently energetic particle accelerators. So sure we can create gravity from electromagnetic energy. You’ll just need to provide enough energy to create a sufficient mass of baryonic matter. We only need the mass of a largish asteroid to be able to feel the effects of the created gravity, lets say the mass of ceres? Thats 2.3 x 10^21 kg of matter we need to create. Someone else can do the math on how many Terra-Peta etc etc joules that works out to be. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [May 11, 2017, 2:00pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/28 "2017-05-11T14:00:13Z")
> [@coremelt](#): > > Well e = mc squared and you can create matter from electromagnetic energy in sufficiently energetic particle accelerators. So sure we can create gravity from electromagnetic energy. You’ll just need to provide enough energy to create a sufficient mass of baryonic matter. We only need the mass of a largish asteroid to be able to feel the effects of the created gravity, lets say the mass of ceres? Thats 2.3 x 10^21 kg of matter we need to create. > > Someone else can do the math on how many Terra-Peta etc etc joules that works out to be. Just multiply it by 2\*c^2. And add whatever energy we need to shoot that half of the mass created that’s anti-matter somewhere where it won’t do harm, but that’s insignificant compared to the energy required to create the mass. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [May 11, 2017, 3:06pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/29 "2017-05-11T15:06:52Z")
There is no need to mess about converting electrical energy to baryonic matter somehow. If you have a source of electrical energy it is already heavier by the amount of energy present. If you shunt a few megawatt hours of energy from one city to another and say charge a battery with it on reception, the battery will be heavier. Easy. You have just modified the gravitational field around the battery using electrical power. ---
**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:** [May 11, 2017, 9:07pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/30 "2017-05-11T21:07:48Z")
My favorite example of “energy has mass” is that in some neutron stars, the magnetic field alone is about a billion times denser than lead. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [May 11, 2017, 9:58pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/31 "2017-05-11T21:58:34Z")
> [@Francis\_Vaughan](#): > > There is no need to mess about converting electrical energy to baryonic matter somehow. If you have a source of electrical energy it is already heavier by the amount of energy present. If you shunt a few megawatt hours of energy from one city to another and say charge a battery with it on reception, the battery will be heavier. Easy. You have just modified the gravitational field around the battery using electrical power. I think you could do this at home? Take a lead acid battery at full discharge, measure specific gravity with hydrometer Full charge battery and measure specific gravity again. Battery is now heavier. Hmm, Chronos is that what you mean that energy contributes to gravity? stored energy increases mass? Also @Chronos, not to nitpick but sans black hole, couldn’t we gravity smash a person to jelly just by letting them try to visit jupiter or saturn? Assuming they survive the descent of course ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [May 11, 2017, 10:08pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/32 "2017-05-11T22:08:33Z")
Back to my original question Would it not be cheaper, easier, safer, and require less energy, to simply spin at least some part of the ship. Centrifugal gravity? ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [May 11, 2017, 10:35pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/33 "2017-05-11T22:35:36Z")
> [@Weisshund](#): > > Back to my original question > > Would it not be cheaper, easier, safer, and require less energy, to simply spin at least some part of the ship. > Centrifugal gravity? There are some issues there. If you spin part of the ship, you probably need countertorque to balance the non-spinning part, not to mention the bearings, which are the main reason you need countertorque. Seems like it would be simpler, overall, to spin the entire ship, which calls for sequencing of the control jets (not particularly difficult, really). The second issue is spin radius. Over the axis-to-circumference radius, the effective gravity will vary from zero to max. If your habitat is twenty feet across, the effective gravity at your head will be quite a bit lower than the effective gravity at your feet while standing. A long spin radius is not a really big problem, except that it calls for more material, which means more mass too accelerate and brake. A counterweight system might make sense, except that, again, the counterweight increases your ship’s mass. Or you could just rely on acceleration for your gravity. Accelerate at three-quarter G, you have three-quarter earth gravity, then, halfway there, you flip around and brake at the same rate. Quite a bit simpler, if you carry the fuel to support that much acceleration. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [May 11, 2017, 10:47pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/34 "2017-05-11T22:47:08Z")
> [@Weisshund](#): > > Also @Chronos, not to nitpick but sans black hole, couldn’t we gravity smash a person to jelly just by letting them try to visit jupiter or saturn? Cloud-top gravity at Jupiter is just 2.5g (roughly, from the top of my head.) Not fun, but survivable (if you have no health problems.) ---
**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:** [May 12, 2017, 2:32am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/35 "2017-05-12T02:32:09Z")
A spinning ship is easy. It doesn’t take much weight of cable to hang a space station-sized habitat module under a decent fraction of a g. So you just split your ship into two parts (maybe put the habitat in the opposite part from the reactor, which is a good idea anyway), string a steel cable between them, and hang them from each other. And you won’t kill someone with Jupiter’s gravity, nor with the Sun’s (about 20 gees), nor with a white dwarf’s (350,000 gees). If you’re standing on the surface of any object, it’s because something is holding you there, and it’s the thing that’s holding you there (which will be electromagnetic) that’s doing the damage, not the gravity itself. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [May 12, 2017, 3:51am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/36 "2017-05-12T03:51:01Z")
The problem with the long cable design is that space is full of a lot of crap. Yes, there is a lot of space between the crap, but one golfball size rock could mess up your whole trip. Waiting for someone from the SAU to come get you out of trouble is not much fun. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [May 12, 2017, 7:56am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/37 "2017-05-12T07:56:41Z")
> [@Weisshund](#): > > I think you could do this at home? > Take a lead acid battery at full discharge, measure specific gravity with hydrometer > Full charge battery and measure specific gravity again. > Battery is now heavier. No, you measure the specific gravity of the electrolyte which changes with the ions dissolved in it. The battery does not change sufficiently in total mass for you to measure it. According to wikipedia a high density lead acid battery has an energy density of 42 Wh/kg, which means charging the battery increases the weight by 0.000000000504 ---
**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:** [May 12, 2017, 11:20am UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/38 "2017-05-12T11:20:18Z")
**eschereal** , do you have any idea just how astonishingly rare golf-ball-sized rocks are in space? While that is a possible failure mode of a cable, it’s way down in the noise. And you can solve even that problem by using multiple smaller cables with just enough redundancy that any n-1 of them are strong enough. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [May 12, 2017, 5:41pm UTC](https://boards.straightdope.com/t/artificially-created-gravity/786227/39 "2017-05-12T17:41:56Z")
> [@Chronos](#): > > A spinning ship is easy. It doesn’t take much weight of cable to hang a space station-sized habitat module under a decent fraction of a g. So you just split your ship into two parts (maybe put the habitat in the opposite part from the reactor, which is a good idea anyway), string a steel cable between them, and hang them from each other. > > And you won’t kill someone with Jupiter’s gravity, nor with the Sun’s (about 20 gees), nor with a white dwarf’s (350,000 gees). If you’re standing on the surface of any object, it’s because something is holding you there, and it’s the thing that’s holding you there (which will be electromagnetic) that’s doing the damage, not the gravity itself. It’s not the fall, it’s the sudden stop at the end. 😃 [Previous page](https://boards.straightdope.com/t/artificially-created-gravity/786227.md?page=1)