# Time dilation in plain english

1. Jun 6, 2007

### phyti

This is a response to the those asking for a non technical explanation,
and those who claim there isn't one.

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2. Jun 6, 2007

### Wallace

Hmmm, that doesn't seem any simpler than typical textbook explanations and I'm not sure that it's correct in any case. For instance

Is not true. The speed is constant relative to all observers!?

:surprised

I should hope not!

3. Jun 6, 2007

### Chris Hillman

Ditto Wallace.

4. Jun 7, 2007

### pervect

Staff Emeritus
The paper seems to invinte one to conclude that the speed of light is not constant with respect to the destination.

This is both untrue, and ruled out by actual experiment (given the additional observation that the Earth is not viewed as the stationary, unmoving, center of the universe but rather as an orbiting planet that is constantly changing its velocity).

The speed of light is constant both with respect to the source and the destination according to relativity.

An really good explanation of the twin paradox (or of relativity) does require one to understand that simultaneity is relative - that in order to specify what "at the same time" means for distant objects, one must specify the means or frame that is used to compare them.

5. Jun 7, 2007

### phyti

It's not claimed to be simpler, just without all the math and abstract concepts.
It might be more precise if it included "independent of the source".

You are just stating the consequences of the constant speed.
Because time for the moving observer is altered, his calculations for spatial intervals (c*t) are altered by the same scale. When he calculates speed,
the dilation factors drop out and of course the speed c is constant for him.

Where in the expression for time dilation do you see a factor for another
frame of reference? It's only v and c!

6. Jun 7, 2007

### G01

$$t = \frac{t_p}{\sqrt{1-\frac{v^2}{c^2}}}$$

What about t and t_p???? One is a factor from one reference frame, the other from a different reference frame, so, no, it isn't only v & c there are the times. Plus v is the speed of a reference frame, so that is another factor relating to reference frames. Sorry, but you can't really get rid of the concept of reference frames moving relative to each other here.

7. Jun 7, 2007

### rbj

maybe they can put this in Wikipedia. after all it is cited and referenced and meets the criteria for inclusion.

BTW, Chris H, they are now (at this very time) giving me the boot (or showing me the exit, whatever metaphor). you were smart to leave before they did that to you.

mob rules.

L8r,

8. Jun 8, 2007

### phyti

There must be a vision problem going around.
In the attachment there is no t_p. The t and v are for the observer moving
with the clock relative to the light signals. The only other reference frame besides the observer is the event (the emission of light).

9. Jun 9, 2007

### Staff: Mentor

Huh? You refer to "the speed v of Al's frame", but don't talk about the other frame. "v" is certainly not the speed of the frame with respect to the light signals, whatever that might mean. (Why v and not 2v or 3.5v? Where does the v come from?)

You state: "It should be emphasized that the time dilation is a result of the frame moving with respect to light, not motion relative to another frame." If this can be said to have any meaning at all, it's exactly wrong.

An "event" is not a reference frame. The space-time coordinates of an event can be measured from any reference frame.

I think we've seen enough.