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I saw this and the related Veritasium video, but am still scratching my head about something. Does this mean that away from all gravity a body does not experie

I saw this and the related Veritasium video, but am still scratching my head about something. Does this mean that away from all gravity a body does not experience any time? ie a person on a spacecraft stopped in intergalactic space would not age relative to persons on planets?

chrisseaton 6y ago
How do you get away from all gravity? Aren't you subject to gravity from all other matter in the universe at all times?
- nobody9999 6y ago
  >How do you get away from all gravity? Aren't you subject to gravity from all other matter in the universe at all times? Yes. But the effect of the distortion of space-time that we call "gravity" is subject to the inverse square law[0]. This means that, as Newton described: "The gravitational attraction force between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation distance. The force is always attractive and acts along the line joining them" As such, while objects are affected by the distortion of space-time, the effect is diminished (but not eliminated) by increased distance from the mass that's distorting space-time. Or at least that's how I understand it. [0] https://en.wikipedia.org/wiki/Inverse-square_law https://en.wikipedia.org/wiki/Inverse-square_law
  - chrisseaton 6y ago
    > but not eliminated So... you can't get away from it. That's what I said isn't it?
    - nobody9999 6y ago
      Yes, you did. However, it depends on how you define "getting away" from it. At some point, the effect is so small that it either can't be measured or even if it can, the effect is so small that any impact is irrelevant in practical terms. If that's the case, you're effectively "getting away" from it. I guess it's a matter of perspective.
montagg 6y ago
I believe (from my limited knowledge from Interstellar) that it’s the opposite: higher gravity environments move slower relative to lower gravity environments, which enabled the “go down to high gravity planet for a couple hours and come back and it’s ten years later” plot point in the movie. So if you’re in intergalactic space, time is actually passing very quickly in the higher gravity environment of a galaxy. But a person’s experience should always be the same, no matter what reference they are in. They will perceive time as passing at the same rate in all environments, but it will be different from people in other environments. Caveat: IANA physicist, and this is not physics advice.
- umvi 6y ago
  I don't think that is quite right. If you travelled near the speed of light and then slowed down again it would look (from your perspective) like you jumped 10 years into the future. So high gravity environments "moving slower" shouldn't result in a jump to the future upon exit. Instead I think what is happening is that massive objects actually stretch the fabric of spacetime somehow so that the closer you are to the object, the slower you travel through both space and time. And the more massive the object, the more stretched space and time become as you get closer to it. Hence if you go near a very massive object, from an outside observer it looks like you are frozen in time because time is so stretched it takes forever for you to move through it. As you mentioned though, from any given frame of reference time will always feel the same. 1 second will always feel like 1 second.
  - vecter 6y ago
    > the slower you travel through both space and time No. You are always traveling at a constant velocity through spacetime. [0] Spacetime: https://en.wikipedia.org/wiki/Spacetime https://en.wikipedia.org/wiki/Spacetime
    - umvi 6y ago
      Ok then in that case I think of it as massive objects tend to compress space the closer you get to them. So though your velocity is constant, you are travelling through more space the closer you get to a massive object (since the space is now compressed) which means you are travelling through less time (in order to maintain same velocity).
willis936 6y ago
It's not that the absence of gravitational fields slows time up relative to observers in more massive reference frames, it's that the presence of gravitational fields speeds up time relative to observers in other reference frames. You would age about the same as you would in microgravity. You could get closer and closer approximations by going into Earth orbit, solar orbit, and galactic orbit. Each approximation has less gravity, so time would pass slightly slower relative to an Earthly observer at each step, but the effect diminishes.
- shireboy 6y ago
  I understand, but the corollary of time appearing to speed up close to gravity well (article explains this is not a field per se) is that it would appear to slow down further away. Is there a minimum speed of time relative to earth?

chrisseaton 6y ago

How do you get away from all gravity? Aren't you subject to gravity from all other matter in the universe at all times?

nobody9999 6y ago
>How do you get away from all gravity? Aren't you subject to gravity from all other matter in the universe at all times? Yes. But the effect of the distortion of space-time that we call "gravity" is subject to the inverse square law[0]. This means that, as Newton described: "The gravitational attraction force between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation distance. The force is always attractive and acts along the line joining them" As such, while objects are affected by the distortion of space-time, the effect is diminished (but not eliminated) by increased distance from the mass that's distorting space-time. Or at least that's how I understand it. [0] https://en.wikipedia.org/wiki/Inverse-square_law https://en.wikipedia.org/wiki/Inverse-square_law
- chrisseaton 6y ago
  > but not eliminated So... you can't get away from it. That's what I said isn't it?
  - nobody9999 6y ago
    Yes, you did. However, it depends on how you define "getting away" from it. At some point, the effect is so small that it either can't be measured or even if it can, the effect is so small that any impact is irrelevant in practical terms. If that's the case, you're effectively "getting away" from it. I guess it's a matter of perspective.

montagg 6y ago

I believe (from my limited knowledge from Interstellar) that it’s the opposite: higher gravity environments move slower relative to lower gravity environments, which enabled the “go down to high gravity planet for a couple hours and come back and it’s ten years later” plot point in the movie. So if you’re in intergalactic space, time is actually passing very quickly in the higher gravity environment of a galaxy. But a person’s experience should always be the same, no matter what reference they are in. They will perceive time as passing at the same rate in all environments, but it will be different from people in other environments. Caveat: IANA physicist, and this is not physics advice.

umvi 6y ago
I don't think that is quite right. If you travelled near the speed of light and then slowed down again it would look (from your perspective) like you jumped 10 years into the future. So high gravity environments "moving slower" shouldn't result in a jump to the future upon exit. Instead I think what is happening is that massive objects actually stretch the fabric of spacetime somehow so that the closer you are to the object, the slower you travel through both space and time. And the more massive the object, the more stretched space and time become as you get closer to it. Hence if you go near a very massive object, from an outside observer it looks like you are frozen in time because time is so stretched it takes forever for you to move through it. As you mentioned though, from any given frame of reference time will always feel the same. 1 second will always feel like 1 second.
- vecter 6y ago
  > the slower you travel through both space and time No. You are always traveling at a constant velocity through spacetime. [0] Spacetime: https://en.wikipedia.org/wiki/Spacetime https://en.wikipedia.org/wiki/Spacetime
  - umvi 6y ago
    Ok then in that case I think of it as massive objects tend to compress space the closer you get to them. So though your velocity is constant, you are travelling through more space the closer you get to a massive object (since the space is now compressed) which means you are travelling through less time (in order to maintain same velocity).

willis936 6y ago

It's not that the absence of gravitational fields slows time up relative to observers in more massive reference frames, it's that the presence of gravitational fields speeds up time relative to observers in other reference frames. You would age about the same as you would in microgravity. You could get closer and closer approximations by going into Earth orbit, solar orbit, and galactic orbit. Each approximation has less gravity, so time would pass slightly slower relative to an Earthly observer at each step, but the effect diminishes.

shireboy 6y ago
I understand, but the corollary of time appearing to speed up close to gravity well (article explains this is not a field per se) is that it would appear to slow down further away. Is there a minimum speed of time relative to earth?