Time Dilation As You Approach The Speed Of Light

[Hymie]

TTT recently posted a thread (based on a youtube video) which besides explaining the above, covered why you cannot exceed the speed of light.

 

In that youtube video, the time dilation effect was described using what I call the ‘classical explanation’ using a ‘light-clock’ in which time is determined by the time it takes for a light beam to traverse between two perpendicular mirrors.  As your speed increases, the hypotenuse of the light path triangle increases – resulting in your light-clock slowing down, despite the speed of light remaining constant.

 

But there is a problem with this ‘classical explanation’ which few give the full picture – let me explain.

 

Let’s say you have a light-clock and are travelling at half the speed of light.  The hypotenuse of the light triangle C will be the square root of (A squared + B squared), which for a right angle triangle of sides 1 and ½ will be 1.12.  But the light in the time-clock has to traverse two of these hypotenuses, so rather than taking 2 units of time to traverse back and forth between the mirrors (as when you are stationary), due to travelling at ½ light speed, it now takes 2.24 units of time.  This is basically the explanation in the youtube video (classical explanation).

 

But what happens if you turn your light-clock through 90 degrees, such that the mirrors are at right angles to the direction of travel?

 

When the light beam is heading towards the mirror that is moving away at ½ light speed, it will take the light 1.5 units of time to reach the mirror, and when the light is heading back towards the mirror that is moving towards it at ½ light speed it will take 0.67 units of time to reach the mirror.  A total time to traverse back and forth between the mirrors of 2.17 units of time.

 

So according to the ‘classical explanation’ when travelling at ½ light speed, with your light-clock positioned with the mirrors parallel to the direction of travel, rather than taking 2 units of time to travel back and forth between the mirrors, it will take 2.24 units of time; but with the light-clock mirrors at right angles to your direction of travel it will take only 2.17 units of time.

 

Since the time dilation at ½ light speed cannot be dependent on the orientation of your light-clock (with reference to the direction of travel) can anyone explain this apparent anomaly?

[ToraToraTora]

You are missing the fact that the light clock is just an illustrative device. In reality it's the bosons in all the atoms that cause the dilation. Only one hypotenuse is needed.

The video here is correct

https://www.theanswerbank.co.uk/Science/Question1882063.html

it's one of many attempts to explain in a way that laymen can comprehend. A very good version of the explanation.

[Atheist]

11:42:

"In reality it's the bosons in all the atoms that cause the dilation."

I don't think Einstein or any modern physicist would agree with that.

[THECORBYLOON]

If the mirrors are at right-angles, the photons would be travelling in the direction of travel.

The link below explains what speed an observer would see, treat the photon as being the car in the example and whatever is carrying the clock as the train.

https://www.quora.com/If-an-object-is-travelling-at-half-the-speed-of-light-inside-an-object-which-itself-is-travelling-half-the-speed-of-light-in-the-same-direction-could-the-object-inside-travel-at-the-speed-of-light

 

[Hymie]

No answer so far has explained why, when travelling at half light speed, the light-clock is slowed more when the mirrors are parallel to the direction of travel versus at right angles – after all, the light-clock is used as an explanation for time dilation when approaching the speed of light.

[CrapatCryptics2]

It is unlikely that our current level of understanding is completely able to interpret this quandary.

[ToraToraTora]

You are not getting it. The concept of the light clock is only a device to extract the equation.

[Hymie]

If the light-clock gives differing results depending on its orientation to the direction of travel – how can we be sure that the equation is valid?

[ToraToraTora]

....because it's a device to explain a principle, not an actual thing. It's all about the view from outside the ship.

[Hymie]

If it is a device to explain a principle (and nothing to do with the speed of light), then it would be equally valid to use the speed of sound, which would result in not being able to exceed 330m/s.

[ToraToraTora]

15:48 no it would not, c is constant regardless of the observer.

[Hymie]

But therein lies the problem, knowing that the speed of light is constant for any observer.

 

Imagine that I have two identical light-clocks on my spaceship travelling at half light speed – both send a light pulse to a mirror and measure the time it takes to travel to the mirror and back.

 

I place one of the light-clocks such that the mirror is parallel to the direction of travel and the other such that the mirror is at right angles to the direction of travel.  Since the speed of light is constant the two light-clocks should agree; but they won’t with the one at right angles reading faster (for the reasons in my OP).

[ToraToraTora]

I tried.

[douglas9401]

Would all things still apply if a heavy clock was used?

[Bazile]

^^in heavy water ?

[beso]

This thread is a great illustration of why analogies can be so misleading. This one is also pointless when the real story is so simple.

The speed of light is not just the fastest speed in the Universe. It is the ONLY speed.

Something that is "stationary" is travelling through Time at the speed of light. Any movement through Space takes away some of the speed through Time as seen by an outside observer.

The hypotenuse of the triangle is the real speed which is always the speed of light.