What is the fastest time can go?

  • #1
If I understand spacetime correctly, if you max out the "space" component (travel as fast as possible), you will travel at the speed of light (speed of causality) and time will stop (or nearly stop) advancing for you.. but what if stopped completely? so you stayed stationary in the exact x y z location in relation to the center of the universe.. how fast would time go for you? Thanks!
 

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  • #2
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If I understand spacetime correctly, if you max out the "space" component (travel as fast as possible), you will travel at the speed of light (speed of causality) and time will stop (or nearly stop) advancing for you.. but what if stopped completely? so you stayed stationary in the exact x y z location in relation to the center of the universe.. how fast would time go for you? Thanks!
You understand incorrectly. For you, time will pass exactly the same as it did before you sped up.
 
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  • #3
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Time always proceeds locally at one second per second from the point of view (reference frame) of any observer.
The time dilation effect you refer to is observed not by the traveller, but by another observer that they are moving in relation to.
This other observer will see that a clock carried by the traveler appears to have slowed down,
For the traveler themself their clock is running at the same rate as usual.
 
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  • #4
ok, let me try to state it another way.
If you travel at .95 of the speed of light for 1 year, people on earth would have aged 3.2 years.
If you travelled at 0 of the speed of light for 1 year, (occupied the same XYZ coordinate in the universe for 1 year) people on earth would have aged what? something less than a year, obviously but could it be a dramatic difference like they only aged 1 minute?
 
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  • #5
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There is no absolute reference frame (XYZ) in relativity.
Objects are either moving or not moving in relation to other objects.
If objects are moving relative to each other then the time dilation effect occurs,
though it is insignificant* until the relative speed gets close to light speed

* 'insignificant' from a human perspective.
GPS satellites which travel nowhere near light speed in relation to Earth need to take tiny amounts of time dilation into account.
If they didn't they would be inaccurate to the extent of several Km.

I'm not sure how much of the time dilation experienced by GPS is due to the fact they are moving and how much is due to their being distant from Earth and so they are subject to less gravity. but in relativity this amounts to the same thing. However experiments have been done with flying clocks around the world in high speed planes. A small but measurable time dilation was observed, consistent with what relativity predicts.
 
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  • #6
ok, I figured it out myself.. basically we are travelling at 800 mi/sec or .004301 c so an object was stationary for 1 year, earth would have only aged 22 seconds
 
  • #7
berkeman
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  • #8
PeterDonis
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Thread reopened.

If you travel at .95 of the speed of light for 1 year, people on earth would have aged 3.2 years.
More precisely: if you start on Earth, travel relative to Earth at 0.95c for 1 year, and then return to Earth, people on Earth would have aged 3.2 years.

Note the key phrases in italics; you don't appear to be taking those key qualifiers properly into account.

If you travelled at 0 of the speed of light for 1 year, (occupied the same XYZ coordinate in the universe for 1 year) people on earth would have aged what?
If you travel at speed 0 relative to Earth for 1 year, then you are just staying on Earth. So people on Earth would have aged...1 year, the same as you.

I have a feeling you intended to ask a different question, but you have not thought it through properly.
 
  • #9
PeterDonis
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I figured it out myself.. basically we are travelling at 800 mi/sec or .004301 c so an object was stationary for 1 year, earth would have only aged 22 seconds
Traveling 800 mi/sec relative to what? Not to Earth; we are on Earth.
 
  • #10
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Traveling 800 mi/sec relative to what? Not to Earth; we are on Earth.
Interesting question. Earth r.t. sun is about 30 km/s; IBEX said 3 km/s r.t. Sagittarius A; and for Andromeda (radial velocity component) it's est. 770 kpc / 3.5 Gyr., which is about 0.28 km/s if I made no mistake. Nothing anywhere close to 800 mi/s.
 
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  • #11
Dale
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368 km/s is our speed with respect to the CMB. That is still off quite a bit, but at least it is on the right order.
 
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  • #12
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I'm not sure how much of the time dilation experienced by GPS is due to the fact they are moving and how much is due to their being distant from Earth and so they are subject to less gravity. but in relativity this amounts to the same thing.
The two effects are opposite, with the reduced gravity effect being significantly greater.
Without corrections for relativity, GPS locations would be wrong by over 6 miles per day. GPS satelite clocks would run faster by 38 ms/day.
They would run 45ms faster due to GR space curvature and 7ms slower due to SR velocity. (see http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html )
 
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The two effects are opposite, with the reduced gravity effect being significantly greater.
For GPS it is. The effects balance out in a circular orbit at an altitude 50% of the radius of the central body relative to someone on the surface (assuming the special relativity effect of the surface rotation is negligible, as it is for Earth).

Without corrections for relativity, GPS locations would be wrong by over 6 miles per day.
That's kind of not true... I mean it would be true if we just pretended time dilation didn't exist altogether and our devices were ignorant of it. However, we could make GPS work without having the clocks on the satellites tick slower. As long as our ephemeris data for the satellites were given in satellite time, everything would work just fine. It just turns out it's useful to have a satellite source of Earth-based time, and it makes it easier for the whole system to work.
 
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  • #14
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ok, let me try to state it another way.
If you travel at .95 of the speed of light for 1 year, people on earth would have aged 3.2 years.
If you travelled at 0 of the speed of light for 1 year, (occupied the same XYZ coordinate in the universe for 1 year) people on earth would have aged what? something less than a year, obviously but could it be a dramatic difference like they only aged 1 minute?
If you travel at 0.95c relative to Earth for 1 year (by your clock) in a straight line, Earth clocks will be at about 0.31 years (assuming the Einstein synchronisation convention). If you go out for half a year and return, they will be at about 3.2 years, yes. Which scenario did you mean?
ok, I figured it out myself.. basically we are travelling at 800 mi/sec or .004301 c so an object was stationary for 1 year, earth would have only aged 22 seconds
800 miles per second relative to what? Stationary relative to what? And I have no idea where 22 seconds comes from. To get that level of differential aging you'd need to be travelling at about 0.9999999c out-and-back relative to the Earth, if my mental arithmetic is reliable.
 
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  • #15
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The two effects are opposite, with the reduced gravity effect being significantly greater.
Without corrections for relativity, GPS locations would be wrong by over 6 miles per day. GPS satelite clocks would run faster by 38 ms/day.
They would run 45ms faster due to GR space curvature and 7ms slower due to SR velocity. (see http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html )
It's a not a "reduced gravity" effect, it is a "higher gravitational potential" effect.

At the surface of the Earth (in the ECI frame), time dilation is

## T= \frac{t}{\sqrt{1- \frac{2GM_e}{R_e c^2}}} ##

Where Me and Re are the mass and radius of the Earth.

Now imagine a planet with 4 times the mass and 2 times the radius of the Earth. This will give it the same surface gravity as the Earth. Time dilation at the surface will be
## T= \frac{t}{\sqrt{1- \frac{2G(4M_e)}{2R_e c^2}}} ##

## T= \frac{t}{\sqrt{1- \frac{4GM_e}{R_e c^2}}} ##

Greater than that at the surface of the Earth, even though the local gravity strength is the same as on the surface of the Earth.
 
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  • #16
Mister T
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If I understand spacetime correctly, if you max out the "space" component (travel as fast as possible), you will travel at the speed of light
That is not a correct understanding. There is no such fastest speed that you can travel relative to me. There is an upper limit (speed of light) on that speed, but you can't reach it. You can come arbitrarily close. As you approach that speed time dilation increases beyond all bounds (approaches infinity).

When most people hear about this they can't help but wonder what would happen if the speed did reach that maximum value. But if such a thing were possible the explanation I provided above would have to be modified, it cannot be used to provide that answer. There is no indication though, that the explanation needs to be modified as it agrees with all observations and experiments made thus far.
 
  • #17
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Maybe the question was if object A is traveling at the speed of light relative to object B, what is the rate of object B's time from A's perspective? I'm not sure if that's what you meant but it seems to be that that would be the fastest time can go. I would think the answer would be infinitely fast but please correct me if I'm wrong.
 
  • #18
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Maybe the question was if object A is traveling at the speed of light relative to object B, what is the rate of object B's time from A's perspective? I'm not sure if that's what you meant but it seems to be that that would be the fastest time can go. I would think the answer would be infinitely fast but please correct me if I'm wrong.
This is all completely wrong. First, you can't GO at the speed of light, only massless objects can do that. So, slow it down to just a fraction less than the speed of light and B's time from A's perspective is practically standing still, not going fast.
 
  • #19
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Maybe the question was if object A is traveling at the speed of light relative to object B, what is the rate of object B's time from A's perspective?
That's a question that cannot be answered because it turns out not to make any sense. One of the postulates of relativity is that the speed of light is the same in all inertial reference frames. An inertial frame moving at the speed of light is therefore a contradiction: light would have to be both stationary and travelling at 3×108m/s. And you can't deduce anything from thinking about a contradiction.

To be honest the original question is based on a bunch of misunderstandings that the OP apparently hasn't stuck around to learn about. We can guess about what he meant, but what he actually wrote doesn't make sense.
 
  • #20
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  • #21
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Thread re-opened after some cleanup.
 
  • #22
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If I understand spacetime correctly, if you max out the "space" component (travel as fast as possible), you will travel at the speed of light (speed of causality) and time will stop (or nearly stop) advancing for you.. but what if stopped completely? so you stayed stationary in the exact x y z location in relation to the center of the universe.. how fast would time go for you? Thanks!
Mentioning the speed of causality just adds confusion to your already confused post. Also there is no center of the universe. Speed is relative, not absolute.
 

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