Physics 1 problem

[NOnga]

You are flying a rocketship at 0.9c from star A toward star B. The distance between the stars is 1.0 ly. Both stars happen to explode simultaneously (which probably spoiled your trip!) in your reference frame at the instant you are exactly halfway between them. Do you see the flashes simultaneously? If not, which do you see first and what is the time difference between them?
Anyone know the best way to pass physics 1?

[CossieG]

I'm not sure of the answer but I just came in here to say that I'm hating physics 1 and wish I never chose it. I've decided not to take physics 2 and I'm just hoping I pass physics 1.

[Captain Rascal]

I don't know anything about physics/relativity or what not but this is my guess: You see the flash from B first, the time it takes would be 1t=0.5-0.9t t~=0.26 years. Time for A to reach you, assuming you stop at B, 1-0.26=0.74, so difference would be 0.48 years.
But i guess there'd be something about time going slower/faster because you're travelling well fast, so don't listen to me

[lzxnl]

You are flying a rocketship at 0.9c from star A toward star B. The distance between the stars is 1.0 ly. Both stars happen to explode simultaneously (which probably spoiled your trip!) in your reference frame at the instant you are exactly halfway between them. Do you see the flashes simultaneously? If not, which do you see first and what is the time difference between them?
Anyone know the best way to pass physics 1?

Well, your spaceship is currently moving towards star B, so although you start the same distance away from both stars, as the stars explode at the same time and the light travels at the same rate, the light from the star you’re headed towards will reach you first.

Now for the second question. Let the Lorentz factor be L. This means that in your reference, your distance to either star will be shrunk to 0.5 ly/L. The light from star B is coming at you at c and you’re moving towards it at 0.9 c, so the distance between you and the light is shrinking at a rate of 1.9c. This is NOT a Galilean velocity transformation. The time it takes the light from star B to hit you is 0.5 ly/L / 1.9c = 0.5/1.9L years
What about for star A? Similar reasoning shows that the distance between the light from star A and the spaceship only shrinks at a rate of 0.1 c. Therefore, the time it takes the light from star B to hit you is 0.5 ly /L /0.1 c = 5/L years. The time difference should thus be 2.0647 years by this calculation.
Let’s try using Lorentz transformations. Define S to be the star’s frame, and define S’ to be the frame of the spaceship. Define the positive x direction to be in the direction from the spaceship to star B, let t=t’=0 correspond to when the spaceship is halfway between the two stars which is when the stars exploded in frame S, and let x=x’=0 for both reference frames at the halfway point between both stars. This means frame S’, the spaceship, is moving at velocity +0.9c, which is v. Then, t’ = L*(t-vx/c^2) for the event ‘A exploding’ in frame S’. Note that x here is the position of A relative to the origin, which is -0.5 light years by our sign definition above. t=0 as we’ve defined the exploding of A (and B) to be at t=0 in frame S. Thus, t’ = -L(vx/c^2) = -L*0.9c*-0.5 ly/c^2 =L*0.45 years. For the event ‘B exploding’ in frame S’, we have t’ = L(t – vx/c^2), where once again t=0. Thus t’=-L*vx/c^2=-L*0.9c*0.5 ly/c^2 = -0.45 L. The time difference is thus 0.9*L = 2.0647 years. Both approaches work; make sure you remember to use length contraction for the first method.

As for passing Physics 1, I would suggest understanding where every formula comes from and how to use each formula. That in itself would get you a long way.