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A scientist has recently invented a gravity machine. This machine pulls all mass within a certain radius (say 50 feet?) towards it at an adjustable rate.

The machine can...

  • create as strong a gravitational field as wanted.
  • not be effected by its environment.

The idea is that using gravitational time dilation this scientist can travel to the future!

My questions are...

  • Does stronger gravity equal faster passage of time?
  • How much stronger can gravity get before it kills humans?
  • Would you even be able to travel in time fast enough to actually be effective (speeds like 10 days per perceived second)?

This is inspired by artificial gravity and inertia negation.

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Aarthew III
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  • Little things like oxygen, nitrogen and argon have mass. Your machine would pull toward itself all the surrounding air. Not to mention the surface the machine is located on. Both of those could create slight problems. Is the machine itself somehow (because science-based: how?) immune to its effects? Also, are there any limits on how much stronger gravity you are willing to deal with? Keep in mind that once the machine has collected a sufficient amount of mass in a sufficiently small volume, you get a black hole. – user May 31 '16 at 16:37
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    Bottom line: I think we need to know a bit more about how this machine works and its effects, before we can provide reasonable answers. – user May 31 '16 at 16:38
  • @Michael Lets say that this machine is not effected by any external forces (should I remove the science-based tag?) and the gravity can be set to as strong as you want without being dangerous to humans. – Aarthew III May 31 '16 at 16:46
  • "should I remove the science-based tag?" You may want to consider the reality-check tag instead, which imposes lower requirements on answers. – user May 31 '16 at 17:01
  • BTW, as far as I understand it, stronger gravity means slower passage of time for the person affected by that gravity. So everything else passes at normal time, but his time is slowed so much that by the time he exits the gravitational field, the outside world has passed a lot of time. – Aify May 31 '16 at 20:03
  • @Aify of course! That means that the question isn't would you be able to travel fast enough, but would you be able to travel slow enough! – Aarthew III May 31 '16 at 20:09
  • More importantly, (and I apologize but I did vote to close this question), this question doesn't make sense. How can you have a machine that produces essentially infinite gravitational pull and yet doesn't crush itself under the weight of the things it does pull? As it pulls more things close to it the radius of the gravitational waves also increases, and eventually you get a black hole, which will most definitely kill a human. – Aify May 31 '16 at 20:11
  • @Aify the idea is that it is programmed to maintain the given gravitational force. If it absorbs enough to increase the gravitational force then it automatically compensates. IE if I tell it to maintain 2Gs and it gathers enough mass to make it 2.001Gs it will set itself to 1.999Gs making the overall force constant. Though I will agree with you that the machines abilities are impossible with modern day technology. – Aarthew III May 31 '16 at 20:39
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    "50 feet" doesn't work. The force falls off with the square of the distance. – JDługosz May 31 '16 at 21:25
  • @JDlugosz what would you suggest? – Aarthew III May 31 '16 at 22:01
  • Joining in on this, @AarthewIII note that gravity is a 100% attractive force. You can't 'average' out the gravity like that, it will only add on to the force. Now, if you had something external pulling on it so the machine wouldn't collapse, i.e. pulling from two directions, you get spaghettification. Also, if you want if to survive, I'd probably aim for removing the Higgs Boson from your machine. That way you can neglect gravity. Anything is possible in the far far far future, right? – Simply Beautiful Art May 31 '16 at 23:56
  • Suggest: either phrase the question (second sentence) in a way that shows you understand that gravity rolls off with distance, or make it clear that you're looking for something which doesn't follow the normal rules (e.g. constant field inside the container, sudden cutoff outside). Note that the latter will not be well received either, with a reality-check tag. – JDługosz Jun 01 '16 at 06:46
  • @JDługosz Applying the Shell Theorem, the force would be zero within a symmetric massive shell. Within a sufficiently massive shell, the gravitational potential would be sufficiently (s)low. The only matter with this would be that that shell would likely collapse into blackhole. To prevent that, you could surround that shell with another shell of strange matter...Of course it is estimated that this would require more energy than exists in the entire universe. https://en.wikipedia.org/wiki/Shell_theorem#Inside_a_shell – Aron Jun 01 '16 at 14:31

2 Answers2

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  1. Stronger gravitational force does in fact allow you to travel through time "faster" due to gravitational time dilation, as your link explains.

  2. In order to have noticeable affects due to time dilation, it would basically kill you first. Mainly spaghettification and the maximum amount of force a human body can have for a duration of time and survive. Something on the order of 300 Newtons for a short time span if I can recall.

  3. So... no. You probably won't even perceive the time dilation. I imagine you don't understand too much of the jargon from your gravitational link, but the basic point is that you'd have to be near a black hole to really get the effects. If you stood on top of the sun for a year (neglecting special relativity), you would probably miss only a few days at most. That's how much gravity you're dealing with.

Also note:

$$F_G\approx G\frac{M_1M_2}{r^2}$$

This formula describes approximately how much force there is. From this, it is obvious you cannot 'contain' the effects in 50 feet, gravitational force will simply stretch out and become weaker, but still noticeable.

SAFETY HAZARD: Do not try this experiment within the solar system for general safety.

Tim B
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Simply Beautiful Art
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  • Sorry but your science is wrong. Very very wrong. Gravity does not cause time dilation, gravity does not cause spaghettification. What does cause time dilation is being at a lower gravitational potential (the integrand of gravity). What does cause spaghettification is tidal forces (which is the differential of gravity). In both cases you could (in theory) shape a gravitational field to serve your purpose. In practice, if you could shape space time that easily, you will have of course invented a device that could produce an Alcubierre metric (warp drive). – Aron Jun 01 '16 at 05:20
  • @Aron I was just making this answer for the purpose of the OP. – Simply Beautiful Art Jun 01 '16 at 11:32
  • Don't take this the wrong way. It's good that you tried to answer. It's just not based on correct physics, not everyone understands GR after all. – Aron Jun 01 '16 at 11:46
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    After thinking about it a bit more, applying the Shell Theorem, it is possible to do this with only semi-classical mechanics. A sufficiently massive symmetric shell would do exactly what the OP needs. https://en.wikipedia.org/wiki/Shell_theorem#Inside_a_shell – Aron Jun 01 '16 at 14:27
  • @Aron Robert L Forward has described how to arrange compensating masses to produce flat spacetime in a small region near a superdense mass where you'd be torn apart through tides normally. – JDługosz Jun 01 '16 at 18:32
  • @Aron I'm not sure I understand when you say "Gravity does not cause time dilation, gravity does not cause spaghettification." Gravitational potential and tidal forces arise through the gravitational field, which is how gravity propagates, correct? – HDE 226868 Jun 02 '16 at 23:38
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    @HDE226868 My point is that what most people consider to be "gravity" is the force field of gravity. Gravitational Potential and the Tidal Forces are the integrand and the Divergence respectively. Therefore it is possible to have an area which is locally without a gravity force field, but is at a potential that is different from the ground state. Also, it is possible to have a massive gravitation field, with only a small tidal force. – Aron Jun 03 '16 at 03:20
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Actually, in your own link it says that: "The weaker the gravitational potential (the farther the clock is from the source of gravitation), the faster time passes." So the higher gravitational density would probably actually SLOW time down for him. To speed time up, it sounds like you would want a "negative" gravitational source, which is something we don't know for sure exists.

Redbud201
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  • Also, speeding time up for him inside the bubble would make the outside world seem to slow down by comparison. I don't know that actual time "travel" would happen either. perhaps the only way for him to actually seem to travel (from his perspective) is by being in stasis while the world changes around him. – Redbud201 Jun 02 '16 at 23:30
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    If time slows down for him, and the rest of the universe doesn't slow down, you would "travel forward in time" relative to the rest of the world. That's how time dilation works. Its like driving slow and having all the cars pass by you. Each car could represent 1 minute, 1 hour, 1 year, so this would be traveling forward through time. – Simply Beautiful Art Jun 03 '16 at 00:24