Time dilation flashlight problem

[dmarbell]

I have a copy of "Relativity and Early Quantum Theory" by Robert Resnick. On page 78 there is a problem from chapter 2:

A, on earth, signals with a flashlight every six minutes. B is on a space station that is stationary with respect to the earth. C is on a rocket traveling from A to B with a constant velocity of 0.6c relative to A. (a) At what intervals does B receive the signals from A? (b) At what intervals does C receive signals from A? (c) If C flashes a light using intervals equal to those he received from A, at what intervals does B receive C's flashes?

Answers given are (a) 6 minutes, (b) 12 minutes, and (c) 6 minutes.

I have no questions about answers (a) and (c). The time dilation calculation for (b) seems to be 1.25, instead of 2. 1/((1-(v^2/c^2))^.5) = 1.25.

Yet here is a link that states the time dilation for 0.6c is 2. What am I missing?

http://science.howstuffworks.com/science-vs-myth/everyday-myths/relativity15.htm

Danny

 

[Doc Al]

I have no questions about answers (a) and (c). The time dilation calculation for (b) seems to be 1.25, instead of 2. 1/((1-(v^2/c^2))^.5) = 1.25.

Yet here is a link that states the time dilation for 0.6c is 2. What am I missing?

Don't confuse the time dilation factor (gamma) with the Doppler shift factor. Look up the relativistic Doppler effect; that's what you need for part b.

 

[dmarbell]

It appears the correct formula for the time dilation is t(1) = t/((c-v)/(c+v))^.5, where t=6 minutes. t(1) would be 12 minutes. Does that look right?

Danny

 

[Doc Al]

It appears the correct formula for the time dilation is t(1) = t/((c-v)/(c+v))^.5, where t=6 minutes. t(1) would be 12 minutes. Does that look right?

Yes, but don't refer to that as 'time dilation'. It's the relativistic Doppler shift. (Time dilation is just a part of it.) See: http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/reldop2.html"

 

[dmarbell]

Here is a part of what's causing my confusion. On page 48 of the book, Resnick says "A clock is measured to go at its fastest rate when it is at rest relative to the observer. When it moves with a velocity of v relative to the observer, its rate is measured to have slowed down by a factor of (1-(v^2/c^2))^.5.

Does this mean that if I am on earth, as in the above example, and flash a light at six minutes intervals, I would see them arrive at the ship C at 7.5 minute intervals? But the observer on the ship would see them arrive at 12 minute intervals?

I see that two observers, one at rest and the other moving very fast, would read their own clocks differently. But does that mean also that one observer reading a moving clock would read a time that did not agree with his own clock, and also did not agree with the change in time the second observer was seeing?

Danny

 

[Doc Al]

Here is a part of what's causing my confusion. On page 48 of the book, Resnick says "A clock is measured to go at its fastest rate when it is at rest relative to the observer. When it moves with a velocity of v relative to the observer, its rate is measured to have slowed down by a factor of (1-(v^2/c^2))^.5.

Right. This effect of moving clocks running slow is called time dilation. The factor by which time slows down is called the Lorentz factor, gamma, which is defined as 1/[(1-(v^2/c^2))^.5] (the inverse of what you wrote). In your example, gamma = 1.25.

Does this mean that if I am on earth, as in the above example, and flash a light at six minutes intervals, I would see them arrive at the ship C at 7.5 minute intervals?

No. The person on the ship, after making his observations, would conclude that you flashed your light every 7.5 minutes according to his clocks. (After all, your clocks run slow according to him.)

But the observer on the ship would see them arrive at 12 minute intervals?

Right. Note that there's more to the Doppler effect than just time dilation. There's also the fact that the ship is moving away from the source, which adds more time between the arrival of the flashes. While the ship would see the flashes arrive every 12 minutes, you back on Earth would conclude that the flashes arrived at the ship every 15 minutes according to your Earth clocks (due to time dilation).

I see that two observers, one at rest and the other moving very fast, would read their own clocks differently.

They each consider the other's clocks as running slow compared to their own.

But does that mean also that one observer reading a moving clock would read a time that did not agree with his own clock, and also did not agree with the change in time the second observer was seeing?

I'm not sure what you mean here. See if you can rephrase the question, or give an example of what you mean.

 

[dmarbell]

Right. Note that there's more to the Doppler effect than just time dilation. There's also the fact that the ship is moving away from the source, which adds more time between the arrival of the flashes. While the ship would see the flashes arrive every 12 minutes, you back on Earth would conclude that the flashes arrived at the ship every 15 minutes according to your Earth clocks (due to time dilation).

Can you show me how the calculation works to arrive at the 12 minutes? It appears, upon further reading, on page 66 of my book: The third of our four equations above [...] gives us directly the one remaining phenomenon we promised to discuss; the relativistic equation for the Doppler effect...

which he boils down for an angle theta = 180 degrees to be

v = v' (((c-v)/(c+v))^.5) which directly yields 2, or 12 minutes observed between flashes as seen by C.

Danny

 

[Doc Al]

Can you show me how the calculation works to arrive at the 12 minutes?

Are you asking about the calculation, or about the derivation of the Doppler shift equation? I'll address the calculation.

v = v' (((c-v)/(c+v))^.5) which directly yields 2, or 12 minutes observed between flashes as seen by C.

That equation relates the source frequency (v') to the observed frequency (v). The symbol for frequency is the Greek letter nu, but better to use f for frequency so we don't confuse it with the velocity v. In any case, plugging in the numbers gives you f = f'/2. The source frequency is (1 flash)/(6 minutes), so the observed frequency is half of that or (1 flash)/(12 minutes).

Realize that period (T) is the inverse of frequency (f): T = 1/f. So if the observed frequency is half the source frequency, the observed period (12 min) will be twice the source period (6 min).

Let me know if that's making sense.

 

[Physicist1231]

I know that I am new to the Forum but i suggest a different answer for B).

This goes against most of what we know of the time dilation formula using reletivistic physics but this does hold water.

If you use Newtonian Physics you can see that C would percieve the 6 minute intervals at a rate of 15 minutes given A does not move and C is traveling at .6c directly away from A.

I say this by breaking down the event using a modified version of the Galilean Transformation.

Development:
Since we are calculating time we will start off with the basic equation:
T = D/V
If we draw the four points in time we can see how each relates to the other in time

***I do have a chart with the breakdown but it does not paste well***

The chart showed 4 different times.

Beginning of an event
End of an event
When the beginning of an event is percieved
When the end of the event is percieved

This created some timeframes that needed to be calculated

T = actual time it took for an event to take place
Ti = the time it takes from the begginning of the event to when it is perceived by reference
Te = the time it takes from the end of the event to the when it is perceived by reference
Tp = total amount of time for the event to be precieved by the reference.


Our end goal is to determine how much time an event was perceived to take place by a reference. We will to this with the following equation:
Tp = (Tt-Ti)+Te
For this experiment we will assume that we know Tt. With that said we need to find Ti and Te. We need to calculate these separately.

Ti will be easiest to start with. We will use the starting formula for this.
Ti = D/V
Where D will be the entire amount of distance the photon covered to intercept with the reference. This can be calculated by:
D = (Initial Distance between object and reference)+(Distance traveled by reference to Sop)
And V will be the rate of closure for the photon to the reference point. We can get this by subtracting the velocity of the photon and the velocity of the reference.
V = (C)
After we plug in the new values we get:
Ti = (Di+Dr)/(C)
Since we are assuming we know the initial distance and the velocities we need to break down the Distance the reference traveled until it started to perceive the event. This can be done by:
Dr = (Vr*Ti)
This gives us a slight dilemma though as if we plug this in we have Ti on both sides of the equation.
Ti = (Di+(Vr*Ti))/(C)
We now need to solve for Ti. After doing the math you come out with:
Ti = (Di)/(C-Vr)


Te will be calculated in a similar manner. However, the distance that needs to be covered is different. The base formula for Te will look like this.
Te = D/V
Where D is now the following
D = Di+Dr+(Distance traveled by reference from Eoe to Eop)-(Distance traveled by object to Eoe)
Again we need to break this down because we don’t know how far everything traveled. When we do we get this
D = Di+(Vr*Tt)+(Vr*Te)-(Vo*Tt)
The closing velocity remains the same (since it is uniform motion).
V = (C)
When we put this together we have the following:
Te = (Di+(Vr*Tt)+(Vr*Te)-(Vo*Tt))/(C)
We need to solve for Te since it is on both sides of the equation
Te = (Di+Tt(Vr-Vo))/(C-Vr)


With Ti and Te broken down into usable components we can now solve for TP
Tp = (Tt-((Di)/(C-Vr))) + ((Di+Tt(Vr-Vo))/(C-Vr))


When we plug in the numbers we have from the example we can determine that C will receive the first flash and the second flash in an interval of 15 minutes rather than 12.

This keeps the photon of light traveling (from the point of origin) at the speed of light.

This keeps the Doppler Effect in the equasion.

This also keeps Newtonian Physics working even at High speeds such as large fractions of the speed of light. (as well as much slower objects).

 

[Doc Al]

I know that I am new to the Forum but i suggest a different answer for B).

This goes against most of what we know of the time dilation formula using reletivistic physics but this does hold water.

If you use Newtonian Physics you can see that C would percieve the 6 minute intervals at a rate of 15 minutes given A does not move and C is traveling at .6c directly away from A.

Sorry, but you just ignored time dilation. That doesn't 'hold water', as it gives the wrong answer.

When we plug in the numbers we have from the example we can determine that C will receive the first flash and the second flash in an interval of 15 minutes rather than 12.

Sure, but you ignored the important factor of time dilation.

This keeps the photon of light traveling (from the point of origin) at the speed of light.

This keeps the Doppler Effect in the equasion.

This also keeps Newtonian Physics working even at High speeds such as large fractions of the speed of light. (as well as much slower objects).

No it doesn't. It just gives you the wrong answer. (Kind of silly to ignore relativistic effects, especially in this forum, don't you think?)

 

[Physicist1231]

Thank you for pointing out that I am wrong. Where in fact am I wrong though? Following the logic of the math where is it incorrect? I have been working on this for a couple years so I may be fresh to the field but. I see no area where this does not explain what we have observed in previous experiments. Rather it comes to the concusion based on Newtonian Physics (which are laws) instead of Relativistic Physics (which are theory).

Laws are laws and theories are theories. If theories do not fit your Laws then we need to rewrite the theories till we get them right.

Please help

 

[Physicist1231]

Doc Al,

This may go off on its own tangent so I created a new topic so as to not convolute this one.

https://www.physicsforums.com/showthread.php?t=494417

 

[Doc Al]

Thank you for pointing out that I am wrong. Where in fact am I wrong though? Following the logic of the math where is it incorrect? I have been working on this for a couple years so I may be fresh to the field but. I see no area where this does not explain what we have observed in previous experiments. Rather it comes to the concusion based on Newtonian Physics (which are laws) instead of Relativistic Physics (which are theory).

Laws are laws and theories are theories. If theories do not fit your Laws then we need to rewrite the theories till we get them right.

Please help

You ignore time dilation! (Among other things, but that's enough to get the wrong answer.)

And your view that Newtonian Physics is somehow more correct than Relativistic Physics is out of date by over a century. Experiments (not just 'theory') have demonstrated that special relativity is correct where Newtonian physics is inadequate. This is hardly controversial--special relativity has been thoroughly confirmed and is a standard tool used daily.

 

[Doc Al]

Doc Al,

This may go off on its own tangent so I created a new topic so as to not convolute this one.

https://www.physicsforums.com/showthread.php?t=494417

No thanks. There's not much more to say. I'll delete that new thread.

I suggest you review the sticky at the top of this forum: https://www.physicsforums.com/showthread.php?t=17355"

 

[JesseM]

I know that I am new to the Forum but i suggest a different answer for B).

This goes against most of what we know of the time dilation formula using reletivistic physics but this does hold water.

If you use Newtonian Physics you can see that C would percieve the 6 minute intervals at a rate of 15 minutes given A does not move and C is traveling at .6c directly away from A.

Your comment is ambiguous in Newtonian physics, incorrect in relativity. It's easier to just use the specific numbers you gave above, rather than figure it out with abstract symbols as you did in the rest of your post. Say we are using the frame where A is at rest, and A is at fixed position coordinate x=0 in this frame. Suppose C is at position x=20 light-minutes (a "light-minute" is the distance light travels in a minute, akin to a light year) at t=0 minutes in this frame, and at that moment emits one signal traveling at 1c towards A, which reaches A at t=20 minutes in this frame. Then if we ignore time dilation, then C will emit a second signal at t=6 minutes, and moving at 0.6c, C should then be at position x=20+6*0.6=23.6 minutes. So, this signal will take 23.6 minutes to reach A, getting to A at t=6+23.6=29.6 minutes. So here we find that A sees a 9.6 minute gap between signals, not 15 minutes as you suggested.

But maybe your intent was that in Newtonian physics the light would move at 1c relative to C, not relative to A. In this case, in A's frame the light moves at 0.4c. Then if the first signal is emitted at t=0 minutes at x=20 light-minutes, it will reach A at 20/0.4 = 50 minutes. And if the second signal is emitted at t=6 minutes from position x=23.6 light-minutes, it should take a time of 23.6/0.4= 59 minutes to reach A, so it will reach A at t=6+59=65 minutes. So in this case you are correct that the delay between signals is 15 minutes for A.

In relativity though it would be wrong to assume that since the light moved at 1c relative to C, then it would move at 0.4c relative to A; in relativity light moves at 1c in all inertial frames. And in relativity you also have to take time dilation into account, so if 6 minutes is the time between signals as measured by C's clock, then the time between signals in A's frame would have to be 6/sqrt(1 - 0.6c^2/c^2) = 6/sqrt(0.64) = 6/0.8 = 7.5 minutes. So if C sent the first signal at t=0 minutes from position x=20 light-minutes, A would receive this at t=20 minutes, then C would send the second signal at t=7.5 minutes from position x=20+(7.5*0.6)=24.5 light-minutes, and this would take an additional 24.5 minutes to reach A, so A would get it at t=7.5+24.5=32 minutes. So in this case, A does in fact see a 12 minute gap between successive signals.

 

[Physicist1231]

Say we are using the frame where A is at rest, and A is at fixed position coordinate x=0 in this frame. Suppose C is at position x=20 light-minutes (a "light-minute" is the distance light travels in a minute, akin to a light year) at t=0 minutes in this frame, and at that moment emits one signal traveling at 1c towards A, which reaches A at t=20 minutes in this frame. Then if we ignore time dilation, then C will emit a second signal at t=6 minutes, and moving at 0.6c, C should then be at position x=20+6*0.6=23.6 minutes. So, this signal will take 23.6 minutes to reach A, getting to A at t=6+23.6=29.6 minutes. So here we find that A sees a 9.6 minute gap between signals, not 15 minutes as you suggested.

You have a good setup but you are kind of pointing out the wrong thing. I was not mentioning the time it takes to percieve the first setup rather the interval between the flashes. With that sad using your scenario:

At T=0:
Object is at POS (0,0,0)
Reference point is (20lm,0,0) (light minutes)
Ref starts moving directly away at (.6C,0,0) (moving only on the XAxis directly away from object
Light has been triggered but has had no time to travel

Start the timer and as the photon of light travels to the ref the ref is moving away. The photon is traveling at C (away from point of origin). Using Newtonian physics the rate of approach between the Photon of light and the ref would be:

V = C-Vr

V = C-.6C

V = .4C

Now that we know the rate of approach we need to find out how far the reference point travels till the photon intercepts it. That is where the math gets tricky. You know the velocity of the photon and the velocity of the ref and the time it takes to initialy percieve the light with be at Ti. This marks the beginning of perception.

Ti = Dr/Vr (For the reference)

Ti = Dl/C (for the light)

At this point we have two unknowns Ti and Dl (total distance the light traveled to reach the ref)

But we know that the Dl = Di +Dr (initial distance plus the gained distance by the ref)

We also know that the distance the ref made (Dr) is equal to the Vr * Ti.

you can then say that

Ti = (Di + (Vr * Ti))/C

Now we have just the one unknown. BUT it is on both sides of the equation. We need to fix that with simple math principles we learned in middle school (or sooner). We then get

Ti = (Di)/(C-Vr)

Now let's plug those numbers at T=0 to find out when the ref "sees the light"

Ti = 20lm/(C - .6c)

Converted to m/s (so long as you keep your units straight you can do it without converting)

Ti = 3.6 x 10^11/ (1.2 x 10^8)

Ti = 3000s = 50 minutes

This is a little over twice the initial time if the ref would have sat still. This result is to be expected since it would EXACTLY double if the ref was going at .5C.

So do thank you for pointing that out but the math was just a little off.

What i was originally reporting was how long between the first light hitting him and the one triggered 6 min later. Since the ref was moving directly away at .6c then the beginning wave and end wave would be perceived to be 15 minutes apart. Again a little over double but that is to be expected since it is over .5c.

This explains why the ref would percieve an event taking longer than it really did and using simple known math that does NOT break down at larger speeds.

It is true that previous attemts to do this were a fail. The Galilean Transformation was the breaking point and is faulty. Since this was faulty Science strayed away from it and substituted Relativity and the Lorentz Transformation assuming that space and time are flexible whereas Newtonian physics assumes they are not flexible however can be perceived differently by different observers.

 

[JesseM]

You have a good setup but you are kind of pointing out the wrong thing. I was not mentioning the time it takes to percieve the first setup rather the interval between the flashes.

I was calculating the "interval between the flashes" too, for example in the first paragraph using Newtonian assumptions and light traveling at 1c relative to A, I showed that if C sent out flashes at t=0 and t=6 in A's frame, A would receive them at t=20 and t=29.6, so the interval between flashes for A is 9.6 minutes. Similarly in the second paragraph with Newtonian assumptions but light moving at 1c relative to C rather than A, I showed the interval between A receiving two signals from C is 15 minutes. Finally in the third paragraph using relativity's assumptions (that light moves at 1c in A's frame, and C's clock is dilated in A's frame so 6 minutes for him is 7.5 minutes for A), the interval between A receiving signals from C is 12 minutes.

Do you disagree with any of the numbers in my analysis?

 

[Physicist1231]

JesseM,

I did miss that sorry... Actually looking at your math it is a little off. You have the Ti calculated as X=20+6*.6c. This is not quite it as this will calculate where teh photon of light will be after that amount of time. That is NOT where the moving reference will be at that point in time. You need to find the point in space and time where both meet.

Using the old T=D/V

We know the Photon is traveling at the speed of light. So V=C

Now we need to find out how far that photon has to travel to reach the moving object.

You have the initial distance Di =20 and then you need to add the distance covered by the object (this is the point of error). You should have the following

Ti= (Di + (Vo*Ti))/C

You will notice that the object travels much longer than what you predicted by the previous post.

Yes you do have Ti on both sides of the equation so you need to solve for Ti (good old middle school math)

You will get the following

Ti = (Di)/(C-Vr)

Plug in the numbers since we know all but Ti (point in time that Object is perceived by reference)

Ti = 20lm/(C - .6c)

Converted to m/s (so long as you keep your units straight you can do it without converting)

Ti = 3.6 x 10^11/ (1.2 x 10^8)

Ti = 3000s = 50 minutes

If you do this again for the second wave (released at T=6) then we need to do the following

Te = (Di + (Vr*T) + (Vr*Te))/C

You need the extra part (Vr*T) because the object was moving for 6 min before the wave was let out so it was not at X=20lm.

Again you have Te on both sides. Solve for Te again.

Te = (Di+Tt(Vr))/(C-Vr)

Then you find out how long it took for the second wave of light released at T=6 to be pervcieved from release:

Te = (20lm + 6m(.6C))/(.4C)

Te = (3.6 x 10^11 + 6.48 x 10^10)/(1.2 x 10^8)

Te = 3540s = 59min

Since there was a 6 min delay between the waves you can calculate the inteval this way

Interval = (Te+T) -Ti

Interval = (59m +6min) - 50 = 15 minutes

(ps sorry did not see this post for a while...)

 

[JesseM]

JesseM,

I did miss that sorry... Actually looking at your math it is a little off. You have the Ti calculated as X=20+6*.6c. This is not quite it as this will calculate where teh photon of light will be after that amount of time. That is NOT where the moving reference will be at that point in time.

Huh? By "moving reference" do you mean C, and are you assuming as I do that we are calculating things from the perspective of the inertial frame where A is at rest at position x=0, while C starts at position x=20 at time t=0, and is moving in the +x direction at 0.6c? If you are not using these assumptions you need to clarify your own assumptions about what frame we are using and what you assume about initial positions and times in this frame. But if you are using these assumptions, of course it must be true that at t=6, C must be at position x=20+6*0.6c, if you don't agree with that then you must be misunderstanding something basic about how kinematics works.

 

[Physicist1231]

Huh? By "moving reference" do you mean C, and are you assuming as I do that we are calculating things from the perspective of the inertial frame where A is at rest at position x=0, while C starts at position x=20 at time t=0, and is moving in the +x direction at 0.6c? If you are not using these assumptions you need to clarify your own assumptions about what frame we are using and what you assume about initial positions and times in this frame. But if you are using these assumptions, of course it must be true that at t=6, C must be at position x=20+6*0.6c, if you don't agree with that then you must be misunderstanding something basic about how kinematics works.

I am making those assumptions. the moving reference is the body moving at .6C away from the object. At T=6 then X for the Reference is 20+6*0.6c however X for the photon of light at T=6 is 6*C. You will notice that these two measurements are not the same (yet) so in this moment T=6 the light has NOT reached the reference.

 

[JesseM]

I am making those assumptions. the moving reference is the body moving at .6C away from the object. At T=6 then X for the Reference is 20+6*0.6c however X for the photon of light at T=6 is 6*C.

Which photon of light? I mentioned two, the first emitted at T=0 and the second emitted at T=6 (if we ignore time dilation), and I assumed they were emitted by C towards A, are you instead assuming the photons were emitted by A towards C? (and if you don't mind too much, please use the terminology of A and C, not "the reference" which is confusing because it sounds like the term "reference frame", but here we are using a reference frame where A is at rest, not C)

If you want to talk about light emitted by A towards C, then here are some altered calculations. If we assume the light moves at 1c in A's frame, then the first photon has position as a function of time given by x(t) = 1c*t, while the second has position as a function of time given by x(t)=1c*(t-6) = 1c*t - 6. Meanwhile C itself has position as a function of time given by x(t) = 0.6c*t + 20. So the first photon catches up with C when 1c*t = 0.6c*t + 20, at t=20/0.4c=50 minutes, when both C and the first photon are at position x=50 light-minutes. Then the second photon catches up with C when 1c*t - 6 = 0.6c*t + 20, or t=26/0.4=65 minutes, when both C and the second photon are at position x=59 light-minutes.

Since the first photon reaches C at t=50 minutes while the second reaches C at t=65 minutes, then the two photons hit C 15 minutes apart in this frame. If we assume no time dilation as in Newtonian physics, that means they also hit C 15 minutes apart according to C's own clock. But if we do take into account time dilation, then in 15 minutes of time in this frame, C's own clock only ticks forward by 15*sqrt(1 - 0.6c^2/c^2) = 15*sqrt(1-0.36) = 15*sqrt(0.64) = 15*0.8 = 12 minutes. So in relativity, C should receive the two signals 12 minutes apart according to his own clock. Agreed?

Finally, if we are using Newtonian physics, there is actually no reason to assume that light moves at 1c relative to the emitter A, we could also assume that light moves at 1c relative to the receiver C (perhaps C is the one who's at rest relative to the luminiferous aether). Since in A's frame the photon is moving in the same direction as C, and C is moving at 0.6c in A's frame, this would mean that in A's frame the photons actually move at 1.6c. So in this case the first photon would have position as a function of time given by x(t) = 1.6c*t, the second would have position as a function of time given by x(t) = 1.6c*(t - 6) = 16.c*t - 9.6. So the first would catch up with C when 1.6c*t = 0.6c*t + 20, at t=20 minutes, while the second would catch up with C when 1.6c*t - 9.6 = 0.6c*t + 20, at t=29.6 minutes. So in A's frame we now calculate that the light signals reach C 9.6 minutes apart, and since this is a Newtonian scenario (it must be, if light did not move at 1c in A's frame) then there is no time dilation equation, so C also receives them 9.6 minutes apart according to his own clock.

To sum up, if we have two signals which were sent out by A, 6 minutes apart according to A's clock, we get the following conclusions about the time C observes between two signals:

--Newtonian scenario with no time dilation, light moves at 1c relative to C: 9.6 minutes apart on C's clock

--Newtonian scenario with no time dilation, light moves at 1c relative to A: 15 minutes apart on C's clock

--Relativistic scenario with time dilation and light moving at 1c in A's frame (as it must in every inertial frame in relativity): 12 minutes apart on C's clock

Do you disagree with any of these?

 

[Physicist1231]

You are correct we need to keep things standardized. I was avoiding using C as an object since C can also represent the Speed of light. But we will continue using A and C where A is at complete rest and photons are emitted from A towards C and C is in motion .6c directly away from A.

You should not mix Newtonian physics and Relativistic Physics. They are built on two separate ideas. NP assumes that Space and Time are rigid structures and remain the same even though can be percieve differently. Relativity though assumes that space and time are flexible and can be bent thus leading to different perceptions.

The second scenario if the corret on (as far as Newtonian physics go). The math is not really from the point of view of A or C.

A photon of light is emitted from its source in space and time at the speed of light. That source (no matter the reference point) will always have the same corrdinates for that photon of light. If the object emitting light (in this case A) were in motion then the second photon of light would have a different 3d coord source and be receeding away from that point instead of teh same 3d coord of the first point. This shows that it does not matter the reference point light is traveling at the speed of light always away from its 3d source point in space. Should A be in motion and emit two photons of light at T=0 and T=6 then you will notice a doppler shift effect. In our setup A remained in the same 3d point in space so we did not have to calculate his movement.

in short:

If you are using NP then the first scenario is incorrect but the second is correct.

If you are using RP then the third is correct.

 

[JesseM]

You should not mix Newtonian physics and Relativistic Physics.

I didn't, I gave separate calculations for relativity and Newtonian physics. However it is true in both relativity and Newtonian physics that if in some inertial frame a signal has position as a function of time given by x(t) = 1c*t, and an object has position as a function of time given by x(t) = 0.6c*t + 20, then we can find the time coordinate where the signal reaches the object by setting the two equations equal and solving for t, i.e. solving for t in 1c*t = 0.6c*t + 20. This is just some basic kinematics which holds in both Newtonian physics and relativity, do you disagree?

The second scenario if the corret on (as far as Newtonian physics go). The math is not really from the point of view of A or C.

In Newtonian physics, if you say the speed of light is 1c, you have to define what frame you're defining speed in reference to, since a signal that moves at 1c in one frame will not move at 1c in other frames according to the Newtonian rule for velocity addition. Again, tell me if you disagree with this.

The traditional assumption before relativity was that light was a vibration in the lumineferous aether just like sound waves in air are vibrations in the atmosphere, and just as sound waves always travel at the same speed relative to the rest frame of the atmosphere regardless of the velocity of the emitter, it was similarly assumed that all light waves would travel at the speed of 1c in the rest frame of the aether, regardless of the speed of the emitter. So that's why I did two Newtonian analyses, one assuming that light moved at 1c in the frame of A (assuming A was at rest relative to the aether), and another assuming the light moved at 1c in the frame of C (assuming C was at rest relative to the aether). Both assumptions are consistent with Newtonian physics.

A photon of light is emitted from its source in space and time at the speed of light.

"Speed of light" in what frame? Again, in Newtonian physics if it moved at the speed of light in one frame, it would not move at the speed of light in others. Perhaps you are imagining a ballistic theory where light always travels at c relative to the emitter? The advantage of the aether theory over the ballistic theory is that in the aether theory Maxwell's laws of electromagnetism can hold in the aether frame even if they don't hold in other frames, while a ballistic theory would violate Maxwell's laws in every frame (since Maxwell's laws always predict that electromagnetic waves move at c, regardless of the speed of the emitter).

That source (no matter the reference point) will always have the same corrdinates for that photon of light.

What does "reference point" mean? Are you talking about a reference frame, which is a coordinate system covering all of space and time, not something located at a single "point"? If not you need to define your terms. And I don't understand what you mean when you say the source will "always have the same coordinates", coordinates in what coordinate system? Does "for that photon of light" mean you are imagining the light has its "own" coordinate system in which the source is at rest? This is definitely not a standard idea in either relativity or Newtonian physics, so again you need to explain in more detail if you're suggesting something like this.

If the object emitting light (in this case A) were in motion then the second photon of light would have a different 3d coord source and be receeding away from that point instead of teh same 3d coord of the first point. This shows that it does not matter the reference point light is traveling at the speed of light always away from its 3d source point in space.

Are you using "reference point" to mean the position coordinate where the light was originally emitted, regardless of whether the emitter remains at that position or not? And if so are you talking about relativity or Newtonian physics? In relativity it doesn't matter if you use a coordinate system where the emitter remains at the position of emission or whether you use a coordinate system where the emitter moves away from the position of emission, in both cases the light will have a coordinate speed of 1c, so the distance between the photon and the position of emission is always growing at a rate of 1 light-second per second.

in short:

If you are using NP then the first scenario is incorrect but the second is correct.

Can you be specific about what number you are referring to? Are you saying the first Newtonian scenario where C waits 15 minutes between receiving photons is incorrect, while the second Newtonian scenario where C waits 9.6 minutes is correct? Or vice versa? Either way, both scenarios are correct given the assumptions I listed about which observer's frame the light was moving at 1c relative to.

 

[Physicist1231]

Wow i guess things got a little jumbled. I will try better:

First point you made:I didn't, I gave separate calculations for relativity and Newtonian physics. However it is true in both relativity and Newtonian physics that if in some inertial frame a signal has position as a function of time given by x(t) = 1c*t, and an object has position as a function of time given by x(t) = 0.6c*t + 20, then we can find the time coordinate where the signal reaches the object by setting the two equations equal and solving for t, i.e. solving for t in 1c*t = 0.6c*t + 20. This is just some basic kinematics which holds in both Newtonian physics and relativity, do you disagree?

You are correct in the formula for Newtonian Physics. This does not really work for Relativity (if it did we would have the same results as the distance). In Reletivity Distance or space is also flexible). I believe you had the correct formula for relativity when you came to the results of 12 min.

Second Point: In Newtonian physics, if you say the speed of light is 1c, you have to define what frame you're defining speed in reference to, since a signal that moves at 1c in one frame will not move at 1c in other frames according to the Newtonian rule for velocity addition. Again, tell me if you disagree with this.

The speed 1C for the photon is always from its point of origin. This may be perceived differently by an outside source or even the emitting object (if it were in motion and no longer shares the same 3d Point of Origin as the photon itself). but no matter where you stand. If you know the 3d point of origin you can calculate the 3d point in space where that photon will be at T=X. You can put 0,0,0 anywhere as your reference point and so long as you keep it there and calculate velocities according to just that one point you will always get the same results. That point 0,0,0 needs to remain motionless during all calculations. This also covers the thrid point regarding "reference point".

As far as the scenarios i was referring to the order in which you listed the results before:

--Newtonian scenario with no time dilation, light moves at 1c relative to C: 9.6 minutes apart on C's clock

--Newtonian scenario with no time dilation, light moves at 1c relative to A: 15 minutes apart on C's clock

--Relativistic scenario with time dilation and light moving at 1c in A's frame (as it must in every inertial frame in relativity): 12 minutes apart on C's clock

Hope that helps to straighten it out!

 

[JesseM]

Wow i guess things got a little jumbled. I will try better:

First point you made:I didn't, I gave separate calculations for relativity and Newtonian physics. However it is true in both relativity and Newtonian physics that if in some inertial frame a signal has position as a function of time given by x(t) = 1c*t, and an object has position as a function of time given by x(t) = 0.6c*t + 20, then we can find the time coordinate where the signal reaches the object by setting the two equations equal and solving for t, i.e. solving for t in 1c*t = 0.6c*t + 20. This is just some basic kinematics which holds in both Newtonian physics and relativity, do you disagree?

You are correct in the formula for Newtonian Physics. This does not really work for Relativity (if it did we would have the same results as the distance). In Reletivity Distance or space is also flexible). I believe you had the correct formula for relativity when you came to the results of 12 min.

You misunderstand relativity here, contraction of distance/length only comes into play when you want to compare distances/lengths in different frames, but here I am just talking about coordinate position as a function of coordinate time in a single frame. And you say my 12 minute result was correct, but I derived that simply by solving for t in 1c*t = 0.6c*t + 20 for the first pulse and 1c*t - 6 = 0.6c*t + 20 for the second, concluding that in this frame the coordinate time the pulses reached C was t=50 and t=65, so the coordinate time between C receiving them was 15 minutes. Then I just applied the time dilation equation, which says that in 15 minutes of coordinate time, C's own clock time will only advance by 15*sqrt(1 - 0.6c^2/c^2) = 15*0.8 = 12 minutes.

The speed 1C for the photon is always from its point of origin. This may be perceived differently by an outside source or even the emitting object (if it were in motion and no longer shares the same 3d Point of Origin as the photon itself).

I don't understand what "point of origin" means. Do you understand that even in Newtonian physics, different inertial frames disagree about what point in space now is at the "same position" as some event in the past? Are you assuming some notion of absolute space in which there would be some objective frame-independent truth about whether a given object is "at rest" in absolute space (so remaining at the same "point" in absolute space) or "moving" in absolute space? Even if you are assuming that, and also assuming that light always moves at 1c relative to absolute space, then your thought-experiment doesn't seem to specify whether A or C is the one at rest relative to absolute space (if either are). And hopefully you understand that in relativity there is no notion of absolute space, and it would also be good to understand that even in Newtonian physics, as long as the laws of physics were the same in different inertial frames (respecting the "Galilean principle of relativity"), there would be absolutely no way to determine experimentally which object was at rest in absolute space and which wasn't (see the discussion here).

As far as the scenarios i was referring to the order in which you listed the results before:

OK, but when I listed them originally I was talking about a situation where C sent the signal towards A, I didn't realize you wanted a situation where A sent a signal to C, which is why I gave revised calculations in post #21.

--Newtonian scenario with no time dilation, light moves at 1c relative to C: 9.6 minutes apart on C's clock

--Newtonian scenario with no time dilation, light moves at 1c relative to A: 15 minutes apart on C's clock

--Relativistic scenario with time dilation and light moving at 1c in A's frame (as it must in every inertial frame in relativity): 12 minutes apart on C's clock

So you disagree with the first answer, even if we assume light moves at 1c relative to C? (or if you prefer, that C is the one at rest in absolute space, remaining at the "same point" in space at all times, while A is moving relative to absolute space) If you do disagree even with those conditions in place, can you tell me which part of my calculation you think was in error?

 

[Physicist1231]

I don't understand what "point of origin" means. Do you understand that even in Newtonian physics, different inertial frames disagree about what point in space now is at the "same position" as some event in the past? Are you assuming some notion of absolute space in which there would be some objective frame-independent truth about whether a given object is "at rest" in absolute space (so remaining at the same "point" in absolute space) or "moving" in absolute space? Even if you are assuming that, and also assuming that light always moves at 1c relative to absolute space, then your thought-experiment doesn't seem to specify whether A or C is the one at rest relative to absolute space (if either are). And hopefully you understand that in relativity there is no notion of absolute space, and it would also be good to understand that even in Newtonian physics, as long as the laws of physics were the same in different inertial frames (respecting the "Galilean principle of relativity"), there would be absolutely no way to determine experimentally which object was at rest in absolute space and which wasn't (see the discussion here).

Actually, using the properties we KNOW of light we can determine if something is at absolute rest.

Imaging an apparatus that is perfectly spherical. In the exact center of this sphere there is a much smaller sphere. For our scenario we will call them Sphere A (large) and Sphere B (smaller). Sphere B is an emitter of light across its entire surface in all directions (like a very advanced lightbulb). Sphere A has an is lined with numerous light receptors. Since we know that the emittion of light is in a doppler effect pattern if the entire apperatus is at rest then an emission of light will reach ALL points on Sphere A at the same time. However, if the entire apparatus is in motion (Sphere A and B are relatively motionless to each other) in ANY 3D direction there will be a time delay in the reception of light. The very LAST point on Sphere A to receive light will point out the Direction of travel. Also if you calculate the difference in time from that point to the very Opposite side of the sphere you can then calculate the Speed. Now that you have the Speed and Direction you now have Velocity.

Just because objects are motionless relative to each other does not mean they have no motion.

So you disagree with the first answer, even if we assume light moves at 1c relative to C? (or if you prefer, that C is the one at rest in absolute space, remaining at the "same point" in space at all times, while A is moving relative to absolute space) If you do disagree even with those conditions in place, can you tell me which part of my calculation you think was in error?

If we did assume that the photon was approaching C at 1C then that would be the case. I do not think that the math would be worth doing though because using that thought process would put the individual photon of light in different actual coordinates depending on the reference point. IE if light is approaching everything at the speed of light then it would not matter if an object (originally standing at 20lm away) was moving or not, It would still reach him in 20lm. With that same assumption put two people at 20lm distance and shoot off a single photon of light. If one person is receeding at .Xc but the approaching speed of the photon is still 1c then it will hit both people at T=20min even though they are in physicaly different places. so yes the math for that point is correct... but the logic behind it may result in way too many questions and downfalls.

 

[JesseM]

Actually, using the properties we KNOW of light we can determine if something is at absolute rest.

Not in relativity you can't! And in Newtonian physics it would depend if light always had a speed of 1c in absolute space, or if you used some other theory where it didn't necessarily, like a ballistic theory of light emission. And if light always has a speed of 1c relative to absolute space this means the laws of physics don't respect the principle of Galilean relativity, so this doesn't contradict my earlier statement that there is no way to determine absolute motion if the laws of physics all obey Galilean relativity.

Imaging an apparatus that is perfectly spherical. In the exact center of this sphere there is a much smaller sphere. For our scenario we will call them Sphere A (large) and Sphere B (smaller). Sphere B is an emitter of light across its entire surface in all directions (like a very advanced lightbulb). Sphere A has an is lined with numerous light receptors. Since we know that the emittion of light is in a doppler effect pattern if the entire apperatus is at rest then an emission of light will reach ALL points on Sphere A at the same time. However, if the entire apparatus is in motion (Sphere A and B are relatively motionless to each other) in ANY 3D direction there will be a time delay in the reception of light.

Not true in relativity! In relativity the light moves at 1c in all frames including the rest frame of the sphere, so it will always be true that the light hits every point on the larger sphere simultaneously in the sphere's own rest frame. To understand this you need to be familiar with the relativity of simultaneity which says that different frames define "simultaneity" differently, so if there are clocks at the front and back of the sphere which are "synchronized" in the sphere's rest frame, and the light hits each one when they show the same reading, then in the frame of an observer who sees the sphere in motion, the two clocks are out-of-sync so the fact that both showed the same reading when the light hit them is consistent with the fact that the light actually hit them at different times in this observer's frame. Analyzing a full sphere would be difficult but if you like I can show how, if light is emitted from the center of a + sign that has clocks at all four ends that are synchronized in its own frame, then although the light will hit different ends at different times in the frame of an observer who sees the plus sign in motion, the clocks at each end will all show the same time and thus the light hits each end simultaneously in the rest frame of the plus sign.

Just because objects are motionless relative to each other does not mean they have no motion.

If the laws of physics are all Lorentz-symmetric as required by relativity, then no possible experiment can determine absolute motion, and thus I think it makes sense to do away with this concept altogether.

If we did assume that the photon was approaching C at 1C then that would be the case.

OK, so you do agree with all three of my calculations then, given the assumptions I made in each one?

I do not think that the math would be worth doing though because using that thought process would put the individual photon of light in different actual coordinates depending on the reference point. IE if light is approaching everything at the speed of light then it would not matter if an object (originally standing at 20lm away) was moving or not, It would still reach him in 20lm.

That would only be true if you were calculating things in a frame where the light has a coordinate speed of 1c and C has a coordinate velocity of zero! Even if absolute space exists, you are still free to calculate things from the perspective of a frame that is in motion relative to absolute space, like the rest frame of A. In this frame, C is moving while the light has a coordinate velocity of 1.6c. You may think it's weird to use a frame where coordinate velocities are totally different from "true" absolute velocities, but Newton was fine with doing so even though he believed in absolute space, and you'll still get the correct answer to any question about local events like what time C's clock read at the moment he was struck be each photon.

Anyway, if you calculate things from the perspective of the frame at rest relative to absolute space, then assuming light has a coordinate velocity of 1c in this frame and that C is at rest in this frame, you're right that if C is 20 light-minutes away from A when the first signal is emitted by A, it will take 20 minutes for the signal to reach C. But since we're talking about the Doppler effect we need to consider two different signals from A, so A's motion is important because it means that C will no longer be 20 light-minutes from A at the time the second signal is emitted.

 

[SMRN]

Hi JesseM (Hi to others as well :) )

I have been a silent reader of physics forum for quite some time now and I have read many of your posts. I really appreciate the way you look at things.

Lately I have been reading about time dilation, and one thing, invariably, is boggling me - the reason for time dilation or the mechanism of time dilation

I know it is something more than just an illusion (as some people say it is just the delay caused by the light waves to reach the observer ... but it's false for the simple reason that time dilation is something real)

Would also like to ask an extension of the same question - Why does a mechanical clock has to tick slower when it is moving at a high speed, say 0.9c ... or for that matter why does a biological clock has to get slow (the twin paradox) ?

Is there any established reason/mechanism for time dilation to happen ?

Thanks


** This is my fisrt post on PF, expecting a positive reply **

 

[JesseM]

Hi JesseM (Hi to others as well :) )

I have been a silent reader of physics forum for quite some time now and I have read many of your posts. I really appreciate the way you look at things.

Lately I have been reading about time dilation, and one thing, invariably, is boggling me - the reason for time dilation or the mechanism of time dilation

I know it is something more than just an illusion (as some people say it is just the delay caused by the light waves to reach the observer ... but it's false for the simple reason that time dilation is something real)

Would also like to ask an extension of the same question - Why does a mechanical clock has to tick slower when it is moving at a high speed, say 0.9c ... or for that matter why does a biological clock has to get slow (the twin paradox) ?

Is there any established reason/mechanism for time dilation to happen ?

Thanks


** This is my fisrt post on PF, expecting a positive reply **

Hi SMRN, welcome to the exciting world of physicsforums posting ;) Ultimately I think physics can't really give answers to questions about "why" the laws of physics work the way they do, the only real answer I can give is that all the fundamental laws of physics are invariant under the Lorentz transformation (which relates the coordinates of events in one inertial frame to the events' coordinates in other inertial frames in relativity). This means that if you write down the equations that correctly describe the dynamics of particles and fields in the coordinates of one frame, and then apply the Lorentz transformation to find the correct equations in the coordinates of a different frame, you end up with exactly the same equations. So this means for example that if you build a clock at rest in one frame whose ticking keeps pace with coordinate time in that frame, then as long as the laws governing the constituents of this clock are Lorentz-symmetric, if you built exactly the same type of clock at rest in a different frame, its ticking would keep pace with coordinate time in that frame. And it's not hard to show from the Lorentz transformation that this implies the time dilation equation, since two events which occur at the same position but separated by a time interval of T in one frame (like different ticks of a clock at rest in that frame) will have a dilated time interval of $$T * \sqrt{1 - v^2/c^2}$$ in a different frame moving at v relative to the first, according to the Lorentz transformation.

This answer is probably a little abstract, but I also find it helpful to think in terms of an analogy to ordinary 2D Euclidean geometry. If you have two points on a 2D plane, then a straight-line path will always have a shorter distance than a non-straight path between the same two points. Similarly in spacetime, a "straight" worldline between two points in space and time (the worldline of an inertial observer) always has a greater proper time (time as measured by a clock which has that worldline) than a non-straight worldline (the worldline of an observer who accelerates). And if you draw a Cartesian x-y coordinate system on the plane, and have cars driving along different paths with their odometers running, then paths with different angles relative to the x-axis will have different values for the rate that the odometer reading is increasing relative to increases in the x-coordinate of the car as it traverses different points on the path. This is analogous to how in an inertial frame in spacetime, clocks with different velocities will have different values for the rate that the clock reading is increasing relative to increase in t-coordinate in that frame. Note that in both cases, these rates depend on how you choose your coordinate axes--at any given point on one clock's worldline, there is no objective answer to whether its rate of ticking is faster or slower than some other clock at that moment, this depends on what frame's t-coordinate you use, just like the rate of odometer increase relative to x-coordinate depends on how the x-axis is oriented in the plane. But there is an objective answer to which of two clocks elapses more time in total between two meetings, ust like there is an objective answer to the length of two paths (as measured by an odometer) between the points where they cross. If you're interested, I developed this geometric analogy at greater length in [post=2972720]this post[/post].

 

[SMRN]

Hi SMRN, welcome to the exciting world of physicsforums posting ;) Ultimately I think physics can't really give answers to questions about "why" the laws of physics work the way they do, the only real answer I can give is that all the fundamental laws of physics are invariant under the Lorentz transformation (which relates the coordinates of events in one inertial frame to the events' coordinates in other inertial frames in relativity). This means that if you write down the equations that correctly describe the dynamics of particles and fields in the coordinates of one frame, and then apply the Lorentz transformation to find the correct equations in the coordinates of a different frame, you end up with exactly the same equations. So this means for example that if you build a clock at rest in one frame whose ticking keeps pace with coordinate time in that frame, then as long as the laws governing the constituents of this clock are Lorentz-symmetric, if you built exactly the same type of clock at rest in a different frame, its ticking would keep pace with coordinate time in that frame. And it's not hard to show from the Lorentz transformation that this implies the time dilation equation, since two events which occur at the same position but separated by a time interval of T in one frame (like different ticks of a clock at rest in that frame) will have a dilated time interval of $$T * \sqrt{1 - v^2/c^2}$$ in a different frame moving at v relative to the first, according to the Lorentz transformation.

This answer is probably a little abstract, but I also find it helpful to think in terms of an analogy to ordinary 2D Euclidean geometry. If you have two points on a 2D plane, then a straight-line path will always have a shorter distance than a non-straight path between the same two points. Similarly in spacetime, a "straight" worldline between two points in space and time (the worldline of an inertial observer) always has a greater proper time (time as measured by a clock which has that worldline) than a non-straight worldline (the worldline of an observer who accelerates). And if you draw a Cartesian x-y coordinate system on the plane, and have cars driving along different paths with their odometers running, then paths with different angles relative to the x-axis will have different values for the rate that the odometer reading is increasing relative to increases in the x-coordinate of the car as it traverses different points on the path. This is analogous to how in an inertial frame in spacetime, clocks with different velocities will have different values for the rate that the clock reading is increasing relative to increase in t-coordinate in that frame. Note that in both cases, these rates depend on how you choose your coordinate axes--at any given point on one clock's worldline, there is no objective answer to whether its rate of ticking is faster or slower than some other clock at that moment, this depends on what frame's t-coordinate you use, just like the rate of odometer increase relative to x-coordinate depends on how the x-axis is oriented in the plane. But there is an objective answer to which of two clocks elapses more time in total between two meetings, ust like there is an objective answer to the length of two paths (as measured by an odometer) between the points where they cross. If you're interested, I developed this geometric analogy at greater length in [post=2972720]this post[/post].

Firstly thanks for the reply :)

So you mean to say that nothing happens inside the mechanical clock (probably at atomic level) that makes it to tick slower ?
or nothing happens inside the atoms that makes the biological clock move slow ?

Einstein told us about Relativity and he also told us that if you can't explain a theory to a child then probably it's of no use.

The answer has too much physics in it.

How do you explain a layman the same thing ?

 

[A.T.]

I have been a silent reader of physics forum for quite some time now and I have read many of your posts. I really appreciate the way you look at things.

Lately I have been reading about time dilation, and one thing, invariably, is boggling me - the reason for time dilation or the mechanism of time dilation

If you have been lurking for while, you should already know the non-answer from physics to questions about reasons: The job physics is to tell you "how much" not "why".

To tell you "how much" physics can employ a mathematical model, that answers the "why" question within that model. But that is a reason made up by humans and based on other assumptions that have no known reasons.

Within relativity time dilation and length contraction are related in a way that can be interpreted geometrically, which is sort of a more "intuitive mechanism" shown in this animation:

http://www.adamtoons.de/physics/relativity.swf

 

[SMRN]

If you have been lurking for while, you should already know the non-answer from physics to questions about reasons: The job physics is to tell you "how much" not "why".

To tell you "how much" physics can employ a mathematical model, that answers the "why" question within that model. But that is a reason made up by humans and based on other assumptions that have no known reasons.

Within relativity time dilation and length contraction are related in a way that can be interpreted geometrically, which is sort of a more "intuitive mechanism" shown in this animation:

http://www.adamtoons.de/physics/relativity.swf

Thanks for the link :)

I guess it's not wrong to be curious, physics does not hold you back from asking questions irrespective of the ability of physics to answer the questions.

The whole idea was to understand the rationale behind time dilation to understand it in a better way ...

I would still appreciate some insights into the mechanism of time dilation (if physics has it)

 

[JesseM]

Firstly thanks for the reply :)

So you mean to say that nothing happens inside the mechanical clock (probably at atomic level) that makes it to tick slower ?
or nothing happens inside the atoms that makes the biological clock move slow ?

They don't move slowly in any objective sense. In the frame where that clock is at rest, it ticks at a normal rate while your clock and your biological processes move slow. It just depends on what coordinate system you use, how position and time coordinates are assigned by that system. From the perspective of your frame, the fact that a clock moving slow relative to you slows down can in some sense be "explained" by the fact that the interactions between atoms are electromagnetic, so all interactions slow down for the same reason a light clock seems to run slower when moving relative to you. But again, in the other frame they will say the same thing about you and your clock!

Einstein told us about Relativity and he also told us that if you can't explain a theory to a child then probably it's of no use.

Well, according to the "misattributed" section of the Einstein wikiquote page, his colleague de Broglie once remembered that Einstein had said "that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description 'that even a child could understand them.' " The part about "their mathematical expressions apart" is important, I think Einstein was saying there should be some basic concepts of a theory that could be explainable to anyone, but a real understanding would still require some mathematical detail.

The answer has too much physics in it.

The geometric analogy has no physics in it, you just have to be able to visualize paths in space and how they are described in Cartesian coordinate systems, which only requires some knowledge of algebra. If you don't remember how to graph functions in algebra just say so and I can point you to some basic introductions, but if you do remember it I think you could follow the analogy if you made the effort...

 

[SMRN]

They don't move slowly in any objective sense. In the frame where that clock is at rest, it ticks at a normal rate while your clock and your biological processes move slow. It just depends on what coordinate system you use, how position and time coordinates are assigned by that system. From the perspective of your frame, the fact that a clock moving slow relative to you can in some sense be "explained" by the fact that the interactions between atoms are electromagnetic, so all interactions slow down for the same reason a light clock seems to run slower when moving relative to you. But again, in the other frame they will say the same thing about you and your clock!

Well, according to the "misattributed" section of the Einstein wikiquote page, his colleague de Broglie once remembered that Einstein had said "that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description 'that even a child could understand them.' " The part about "their mathematical expressions apart is important, I think Einstein was saying there should be some basic concepts of a theory that could be explainable to anyone, but a real understanding would still require some mathematical detail.

The geometric analogy has no physics in it, you just have to be able to visualize paths in space and how they are described in Cartesian coordinate systems, which only requires some knowledge of algebra. If you don't remember how to graph functions in algebra just say so and I can point you to some basic introductions, but if you do remember it I think you could follow the analogy if you made the effort...

Thanks a lot for the reply Jesse. I will definitely ponder over what you said and will try to learn these things, if I stumble I'll get back to you.

I actually loved physics since the childhood but I somehow got stuck into the field of management, trying to again pursue my love in the free time.

 

[A.T.]

http://www.adamtoons.de/physics/relativity.swf

Thanks for the link :)
I would still appreciate some insights into the mechanism of time dilation (if physics has it)

Play around with the speed slider in the animation. You will get the idea of how relative movement affects the moving clock and the length along the movement direction.

The idea is that everything advances at a constant rate in spacetime, only the direction and orientation in spacetime changes. The direction affects the rate of the moving clock, as you move more in space or more in time. The orientation affects the length in space as the projection of the object onto the spatial dimensions changes.

Thats the "mechanism".