High School Questions about the Speed of Light, Time, etc.

[phinds]

I remember when I was right, my boss was wrong and it blew up in his face. He claimed it was my fault for being "insufficiently convincing".

Oddly, I had exactly the same thing happen many years ago. You and I must sound basically untrustworthy.

 

[John Mcrain]

Does direction of train matters?
I am at rest at railroad and train moves directly at me, then there is no time dilatation, because I will see train light beam inside light clock goes verticaly up and down,so tick at same rate as my clock.
Is this correct?

 

[Ibix]

Does direction of train matters?

No. The front clock of the train will always be behind the rear clock assuming that they are synchronised in the train rest frame. The tick rate depends only on speed.

I am at rest ar railroad and train moves directly at me, then there is no time dilatation, because I will see train light clock tick at same rate as my.
Is this correct?

Where are you getting this from?

 

[John Mcrain]

Where are you getting this from?

If some one hold light clock and walk toward me,I see light beam inside clock moves verticaly up and down just as when clock is at rest.

I am compare my clock and train clock, not train rear and back clock..

 

[Ibix]

If some one hold light clock and walk toward me,I see light beam inside clock moves verticaly up and down just as when clock is at rest.

So you have no concept of depth? How do you not walk into walls in your every day life?

 

[John Mcrain]

So you have no concept of depth? How do you not walk into walls in your every day life?

I will see light clock bigger and bigger as train approching me..

 

[Ibix]

I will see light clock bigger and bigger as train approching me..

So you have the light following a diagonal trajectory, with components both vertically and coming towards you. Just as the usual depiction has a diagonal trajectory, with components both vertically and left-to-right. The direction doesn't matter.

 

[John Mcrain]

So you have the light following a diagonal trajectory, with components both vertically and coming towards you. Just as the usual depiction has a diagonal trajectory, with components both vertically and left-to-right. The direction doesn't matter.

I know that light beam has diagonal trajectory, but I cant see it from this position/case..

 

[Ibix]

I know that light beam has diagonal trajectory, but I cant see it from this position/case..

I'm staggered that you are struggling with this notion. If an open-topped car is moving laterally with respect to you its occupants feel wind on their faces. Do you think they would not feel wind on their faces if they were coming directly towards you, just because you find it harder to judge their motion in that direction? If yes, why would physics care where you personally are standing? If no, why would you expect a clock to care about your location when you understand that other physics doesn't care?

 

[Dale]

Does direction of train matters?

The best way to answer this question is to look directly at the math of the Lorentz transform. See this section of the Wikipedia entry on Lorentz Transformations.

For time the transformation is $$t'=\gamma\left( t- \frac{\vec r_{\parallel}\cdot \vec v}{c^2} \right)$$ so there are two terms in the transformation. The term $\gamma t$ does not depend on the direction. This term is what we call time dilation so time dilation does not depend on the direction. The term $\gamma \vec r_{\parallel} \cdot \vec v / c^2$ does depend on the direction. This term is what we call the relativity of simultaneity so the relativity of simultaneity does depend on the direction. The relativity of simultaneity occurs in the direction parallel to the direction of motion.

 

[jbriggs444]

I know that light beam has diagonal trajectory, but I cant see it from this position/case..

This is a bit like a batter saying that he cannot measure distance when watching an approaching baseball with one eye closed. Then complaining when the ball hits him in the face. "Hey Ump, that ball could not have been moving because I could not see it moving!"

Say that the train is moving at 0.6 c and the light clock is 4 feet in height. If the light pulse has a 5 foot diagonal trajectory, it will take 5 nanoseconds to follow that trajectory, not 4. Even if we look from in front rather than from the side. The train and light pulse will have moved 3 feet forward in this time.

 

[vanhees71]

So you have no concept of depth? How do you not walk into walls in your every day life?

No problem, in everyday-life only Newtonian spacetime is correct, and there are no such troubles as time dilation, length contraction, and all this...

 

[Ibix]

No problem, in everyday-life only Newtonian spacetime is correct, and there are no such troubles as time dilation, length contraction, and all this...

Yeah, but either @John Mcrain's visual function works different from every other person's on the planet and he's unable to conceive of perspective, or he's not thinking about what he's saying.

 

[phinds]

... he's not thinking about what he's saying.

Forum decorum prohits a response

 

[gmax137]

Forum decorum

I like that. Poetic, even.