speed of time?

**monty37** · Jun20-09, 01:18 PM

what is the speed of time?

**Hootenanny** · Jun20-09, 01:20 PM

Originally Posted by monty37

what is the speed of time?

Perhaps you could elaborate on your question?

**Naty1** · Jun20-09, 02:37 PM

Time appears to pass at a constant rate and that was a cornerstone of Newton's theories. But Einstein showed that space and time are NOT fixed and immutable; they vary according to one's relative motion....space contracts and time slows as relative speed between observers increases. Identical events are observed to occur at different times in different frames. Time also slows down near massive gravitational bodies where gravitational potential is greater.

Check Wikipedia at http://en.wikipedia.org/wiki/Time#Modern_physics

for some additional description and further references.

**DaleSpam** · Jun20-09, 02:49 PM

Time is the thing measured by an ideal clock, and an ideal clock ticks at a rate of 1 second/light-second.

**Max™** · Jun20-09, 04:32 PM

What is the speed of Left?

**negitron** · Jun20-09, 04:47 PM

Originally Posted by Max™

What is the speed of Left?

More accurately reflecting the OP: what is the speed of height? If you consider time as a dimension, it doesn't move at all; instead, objects move through the time dimension in the same way that they can move through the spatial dimensions.

**fluidistic** · Jun20-09, 04:51 PM

According to wikipedia

Speed is the rate of motion, or equivalently the rate of change of distance.

. I think we all agree on any similar definitions.
Hence the question

what is the speed of time?

has no sense.

**HallsofIvy** · Jun20-09, 04:57 PM

Originally Posted by monty37

what is the speed of time?

One second per second!

**Naty1** · Jun20-09, 05:51 PM

Another related interpretation has been discussed in physics forums: our speed through spacetime...in that analogy we pass thru time at "c" when stationary and our passage slows as our speed through space increases....at speed "c" thru space, our passage thru time would slow to zero....

Here is one such excerpt: (Brian Greene, THE ELEGANT UNIVERSE) :

"...Einstein found that precisely this idea - the sharing of motion between different dimensions - underlies all of the remarkable physics of special relativity...
...Einstein proclaimed that all objects in the universe are always traveling through space-time at one fixed speed - that of light...
...If an object dose not move through space all of the objects motion is used to travel through time...
...Something traveling at light speed through space will have no speed left for motion through time. Thus light does not get old; a photon that emerged from the big bang is the same age today as it was then. There is no passage of time at the speed of light."

(quoted from another thread which I just lost....)
Some pooh pooh this concept; I find it at least a very useful analogy; others are unable to conceptualize speed through time.

**MeJennifer** · Jun20-09, 06:25 PM

Originally Posted by Naty1

Another related interpretation has been discussed in physics forums: our speed through spacetime...

Point objects are lines in spacetime and spatially extended objects are like tubes. Nothing passes through spacetime with any speed as spacetime is frozen.

**DaleSpam** · Jun20-09, 07:11 PM

True, but you can still talk of speed in a geometric sense. Geometrically coordinate speed is the slope of the worldline, and geometrically Naty1's speed (the four-velocity) is a tangent to the worldline.

**Max™** · Jun21-09, 09:09 AM

Originally Posted by negitron

More accurately reflecting the OP: what is the speed of height? If you consider time as a dimension, it doesn't move at all; instead, objects move through the time dimension in the same way that they can move through the spatial dimensions.

Left is not a direction/dimension?

It is not part of Width?

**matheinste** · Jun21-09, 09:54 AM

Hello all.

Speed in the directions or dimensions x,y and z is distance paramaterized by time and so we can, if we wish have speed measured in meters per second, one meter being the unit basis vector in each of the spatial directions. I suppose that in spacetime, taking time as a dimension on an equal footing with the other three dimensions, and taking one second as the unit basis vector in the time direction, we should, for consistency, also paramatrerize it by time and so this would give the speed of time, as much as it can "mean" anything, in units of seconds per second. Thus we could give, for a clock at rest in an inertial frame a rate of 1 second per second as measured by itself, or by an observer at rest in the same reference frame.

So as has been said many times before that as much as any meaning can be attached to the question "what is the speed of time?", one second per second seems, to me, to be the most appropriate.

My apologies to any mathematicians for lack of rigor.

Matheinste

**DaveC426913** · Jun21-09, 10:00 AM

Originally Posted by Max™

Left is not a direction/dimension?
It is not part of Width?

Left is a direction in a dimension. If negatron were going to be perfectly literal in correcting you, he would have said "More accurately, what is the speed of width?"

**Naty1** · Jun21-09, 11:14 AM

"Point objects are lines in spacetime and spatially extended objects are like tubes."

Isn't this like plotting the course progress of a plane on a map and proclaiming "A plane is line on a map?"

Any attempts to visualize physical phenomena, interpret and record our visualizations and represent them as mathematical formulations are designed more to represent the physical world in ways our limited senses can comprehend than they are objective descriptions. It's only we humans that seem to have trouble understanding natures rules; an atom,for example, always seems to know how its supposed to respond to forces of all types.

Nothing passes through spacetime with any speed as spacetime is frozen.

What does "spacetime is frozen" mean? Is this akin to "all history is fixed"?

And while some on this forum object to this concept of speed thru spacetime, it seems good enough for Brian Greene to utilize. Of course, he might be entirely wrong!

**Fredrik** · Jun21-09, 11:15 AM

Originally Posted by Naty1

Another related interpretation has been discussed in physics forums: our speed through spacetime...in that analogy we pass thru time at "c" when stationary and our passage slows as our speed through space increases....at speed "c" thru space, our passage thru time would slow to zero....

Here is one such excerpt: (Brian Greene, THE ELEGANT UNIVERSE) :

(quoted from another thread which I just lost....)
Some pooh pooh this concept; I find it at least a very useful analogy; others are unable to conceptualize speed through time.

I think this is the other thread. Greene's explanation is pretty misleading in my opinion, for the reasons I stated there.