# The Speed of Time.

1. Sep 13, 2011

### conner.ubert

How fast does time travel when it is not interrupted by curves in space-time? In other words what is the fastest time can travel? By how fast does it travel, to elaborate, I mean what is the fastest possible transition from one moment in the past to another moment in the future? Is it the speed of light or maybe faster? Or is time the fastest thing in the universe and light can only travel as fast as time will allow?

I hope this makes sense.

2. Sep 13, 2011

### Bloodthunder

Time always travels at a very slow rate of 1 second per second.

3. Sep 13, 2011

### conner.ubert

how is that defined as a slow rate? since time is directly proportional to itself wouldnt it travel .00000000001 seconds every .00000000001 seconds. To define time as slow something would have to travel faster than time to demean its speed.

4. Sep 13, 2011

### Oldfart

I'm confused. Can one measure the speed of time in terms of feet per second, like light? It does sound better to me to say seconds per second, but is that really a speed (velocity)?

We do use speed-like descriptions for time, like time slows down near a black hole, or speeds up as we carry an atomic clock up the stairs. But does "speed of time" really have meaning?

Duhh...

5. Sep 14, 2011

### rbj

Steve Miller: "Time keeps on slippin', slippin', slippin', into the future..."

(i like quoting that song every time someone asks about time travel. while i doubt that time travel to the past can ever be possible, any of us can time travel to the future.)

and i would not characterize that rate as slow or fast. it is what it is.

6. Sep 14, 2011

### easyrider

I think bloodthunder was joking, this is a strange question. I think 10E-43 seconds is the shortest possible time if thats what youre wondering. OTOH, v=d/t, substitue d for t and you always end up with 1. Its like how much faster could something be, and the answer is none, none more fast. Lol, pretty much nonsense.

7. Sep 14, 2011

### Travis_King

Time is relative.

8. Sep 14, 2011

### Hootenanny

Staff Emeritus
I think that your question probably boils down to this: "What is the smallest chunk of time we can have?" or in the jargon: "Is time quantized?". The short answer is maybe. The is no experimental evidence supporting the idea of quantized time, but at the same time, there are no theories prohibiting it, yet again, there are no well developed theories that propose it.

Last edited: Sep 14, 2011
9. Sep 14, 2011

### Ryan_m_b

Staff Emeritus
Time does not travel, things travel through time. Everything travels through time at the same rate in their own reference frame but different frames will disagree.

10. Sep 14, 2011

### Polyrhythmic

The question makes no sense, that's like asking "how long is length?".

11. Sep 14, 2011

### Naty1

Time is not "interrupted" by curves in space time.

It passes at it's regulalarly observed rate in local reference frames.

But according to Einstein, the observed passage of time depends on the reference frame of the observer and is different for observers in relative motion. Einstein showed that people travelling at different speeds will measure different time separations. The effects usually become noticeable for objects moving at speeds approaching the speed of light.

12. Sep 14, 2011

### SamuelRiv

The question is legitimate. We often say "The faster you go, the slower time goes" or "Time slows down when you get close to a black hole".

Special relativity: see the Twin Paradox for the basic idea. If I travel very fast away from you to a distant star and back, the time I experience relative to you is multiplied by a factor of gamma = sqrt(1-v2/c2). So if I travel at 0.87c (nearly 90% of the speed of light) relative to you, gamma = 0.5, so my "time" went half as fast during that journey.

One could then perhaps say that time for me goes at a speed of 1 second-of-me per 2 seconds-of-you?

There's no absolute time frame, however, as all positions and speeds are relative, so the best one can say is that all time is fixed to the speed of light.

People more versed in relativity could probably give you more.

13. Sep 14, 2011

### ZapperZ

Staff Emeritus
People more versed in relativity would NOT consider this as "speed of time". For example, have you ever seen such a phrase being used in a paper?

Zz.

14. Sep 14, 2011

### DaveC426913

Time is a dimension, like length.

15. Sep 14, 2011

### WannabeNewton

Both statements are incorrect in the context you are speaking of. One measures time in his/her reference frame and in that frame time goes neither faster nor slower due to "increased speed" because in your own locally inertial frame you are at rest. Frames that are non - inertial with respect to yours will experience time dilation. Similarly, proper time, which is the frame - invariant measure of time, does not slow down to zero at the event horizon of a black hole.

16. Sep 14, 2011

### bobc2

Conner.ubert,

Hopefully this does not add confusion to the discussion. But, you may be interested in considering the motion of an observer in his own "rest" frame. His velocity is zero along any of our 3-D world directions (X1, X2, X3). But every observer is moving at the speed of light, c, along his own 4th dimension, X4. dX4/dt = c.

Some people like to say that all observers are moving straight into time at the speed of light. I prefer to focus on the 4th dimension as a spatial dimension with motion along the 4th spatial dimension described by dX4/dt = c. So, you might think of yourself as you sit still in a chair, observing the motion of the second hand on your clock, as moving into the 4th dimension at the speed of light, observing a continuous sequence of 3-D cross-section views of your 4-dimensional clock. You are not watching time go by, rather you are experiencing new 3-D cross-sections of 4-dimensional space. Your clock may extend for billions (or trillions) of miles into the 4th dimension. Each second you have moved another 186,000 miles along that direction--every 186,000 miles the second hand is found to be in another position. The marks and labels on the face of the clock could just as easily be displayed as distance traveled along the 4th dimension from some established starting point.

I thought you might be confusing the speed of time with the speed of an observer along the 4th dimension.

Last edited: Sep 14, 2011
17. Sep 14, 2011

### bobc2

I know what you are saying, WannabeNewton. I would be careful not to imply that the frame moving with respect to my rest frame experiences time dilation. Rather, I would observe his clock running slow compared to mine. His time is only dilated from my point of view. His frame is not really experiencing the dilation. And of course this is because the 3-D cross-section of his 4-dimensional clock is part of my 3-D world, which is a different instantaneous 3-D world than the one he is living in at that instant.

Our two different instantaneous 3-D worlds occupy different 3-D cross-section views of his 4-dimensional clock.

I know you are fully aware of this, because in previous posts you have pointed out the error of thinking someone's clock is running slow in his own inertial frame just because he is in motion with respect to someone else. Please don't think I was being argumentative (admittedly a little picky--perhaps unecessarily).

18. Jun 24, 2012

### samm dickens

Hi, conner. We say that someone moving away from us at near light speed appears to move slower through time than we do. In this sense we say that time has a relative speed. Furthermore, we say that a clock in orbit around the Earth moves faster than a clock on the earth, so again we are saying that time has a relative speed. I believe you are talking about these relative speeds of time and asking how fast time can travel in the absense of (1) all relative motion and (2) all gravitational slowing.

Would an answer based on Earth time as a stationary speed of time (that's all relative anyway), and corrected for the effect of Earth's gravity (and maybe the gravitational effects of the Sun and Moon, etc.?) give you the answer you need? I don't know how much time dilation is caused by one gee of gravity so I can't even give you the simple answer, but I think someone can.

Samm

19. Jun 25, 2012

### manojr

Some members have correctly mentioned that time does not travel.

Does following make sense, can some expert comment please?
Clocks run more slowly in deeper gravitational wells (gravitational time dilation), and moving clocks tick more slowly than an observer's stationary clock. In both cases, we see the effect of time ticking slowly. Never do we see clocks ticking faster. So, answer to your question is, time can travel (tick) only as fast as it travels in your reference frame. It may tick slower, but never faster.

20. Jun 25, 2012

### DaveC426913

Perfect.

21. Jan 22, 2013

### marcus

The speed of time (in the sense of a ratio between two rates of time-passage) was the topic of a technical paper recently, and a talk by Matteo Smerlak, a postdoc at Perimeter Institute in Canada. I think it's still an area of active research interest---not everything is resolved about it. Just my non-expert opinion.

Around 1930 Tolman (a relativist at Oxford) discovered that the gravitational field has a temperature---this is called the Tolman effect, or the Tolman-Ehrenfest effect.

In 2011 Smerlak and Rovelli published a paper in Classical and Quantum Gravity showing that this Tolman temperature was the ratio of two rates of time-passage i.e. the speed of one time compared with the other.

http://arxiv.org/abs/1005.2985
Thermal time and the Tolman-Ehrenfest effect: temperature as the "speed of time"
Carlo Rovelli, Matteo Smerlak
The notion of thermal time has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we study this notion in the restricted context of stationary spacetimes. We show that the Tolman-Ehrenfest effect (in a stationary gravitational field, temperature is not constant in space at thermal equilibrium) can be derived very simply by applying the equivalence principle to a key property of thermal time: at equilibrium, temperature is the rate of thermal time with respect to proper time - the 'speed of (thermal) time'. Unlike other published derivations of the Tolman-Ehrenfest relation, this one is free from any further dynamical assumption, thereby illustrating the physical import of the notion of thermal time.
4 pages Class.Quant.Grav.28,2011

Here is a Vimeo (online video) of a portion of Smerlak's talk about this in March 2011:
http://vimeo.com/33363491

Last edited: Jan 22, 2013
22. Jan 22, 2013

### Low-Q

Time and speed of light are related. Both are slowing down in a gravity field at the same rate. GPS satelites are compensated for the less gravity in space. Their clock are tuned slightly slower than the clock on earth. When the satelite is orbiting, its clock speeds up due to less gravity and finally syncs correctly with the clock on the ground. If not, the GPS in your car would display an error of several meters over a relative short distance of travel.

23. Jan 22, 2013

### Naty1

Time passes one second locally when local light has traveled 299,792,458 meters locally.

24. Jan 22, 2013

### cosmik debris

Suppose you are in a deep gravitational well, doesn't a clock higher up appear to tick faster?

25. Jan 22, 2013

### Oldfart

This question seems to beg another: What is the MAXIMUM possible speed-up of a clock, assuming it is a vast distance from the gravity well (Earth) and assuming it has no relative velocity relative to Earth? I suppose that the mass if the clock itself needs to be considered, lets say it's one Kg.