The universe as we know it.
- Thread starter thelorax
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So for 1.) Does this mean that a laser beam particles inside an airplane cabin flying at 600mph would be travelling the same speed as laser beam particles on the ground?
In that case, assuming the ships are 1 light year apart, flying 99% the speed of light, then it would take 99 or 100 years for the first laser to reach the ship in front.
And for 2, it would only take 6 months? (180.675 days)
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1.) Yes, light cant be accelerated. Theres a simple reason for that, because mass is the proportionality factor between Force and acceleration. Since Photons (light) have no mass, they cant be accelerated. Consider
F=m*a where F is force, m is mass and a is acceleration. Try to change that around to a=F/m, you arrive at a problematic expression, because division by 0 is not an allowed operation mathematically. Physically, it leads to what Ive just explained.
You say "on the ground" as if its some kind of "at rest" situation. Relative to a plane, you dont travel on earth, but considering the bigger picture, you might be traveling at high velocities through space. The airplane velocity is not some absolute velocity, its just relative to you. You could be travelling way faster, depending on which direction you go and therein lies the answer to the original question.
2.) The answers you give are still fundamentally incorrect.
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wasnt that hard? Contains a slight mistake though. The speed of light is not relative. Everything else is relative. The speed of light is a constant.
A good read for those interested
[ame=http://www.amazon.com/Why-Does-mc2-Should-Care/dp/0306817586]Amazon.com: Why Does E=mc2?: (And Why Should We Care?) (9780306817588): Brian Cox, Jeff Forshaw: Books[/ame] (I'm in Illinois, and can't even be an affiliate of Amazon)
[ame=http://www.amazon.com/Why-Does-mc2-Should-Care/dp/0306817586]Amazon.com: Why Does E=mc2?: (And Why Should We Care?) (9780306817588): Brian Cox, Jeff Forshaw: Books[/ame] (I'm in Illinois, and can't even be an affiliate of Amazon)
Fuck, I was literally about to type 1 year and then I refreshed the thread and saw it was answered.
I had actually been thinking about it for an hour, and once I drew it on paper the answer came within seconds. I drew 2 ships and marked the line between them as 1 light year. Since they're moving the same speed, light has to travel 1 year to clear the space. Durr.
I had actually been thinking about it for an hour, and once I drew it on paper the answer came within seconds. I drew 2 ships and marked the line between them as 1 light year. Since they're moving the same speed, light has to travel 1 year to clear the space. Durr.
Except it's not exactly that simple
What Happens If You're Traveling At The Speed Of Light And Turn On Your Headlights?
[ame="http://www.youtube.com/watch?v=luAteAz3WQ0"]Carl Sagan "Pale Blue Dot" (New Version) Spread This! - YouTube[/ame]
I watched 2 things in my life 15+ times - the above video and the movie From Dusk Till Dawn.
I watched 2 things in my life 15+ times - the above video and the movie From Dusk Till Dawn.
Thats a bit simplistic. A way to illustrate the problems with the question is this:
In physics, we can place the origin of our system whereever we want. We can especially give it a constant velocity, or even a function of velocity. That "system" im talking about is pretty much the coordinate system you began drawing all the time in math in high school.
By placing that system right in between the two space ships, they are both half a light year apart and at rest, relative to the origin. Now you can just measure the distance, divide it by velocity of the photon and you get the answer. That ONLY works because the speed of light is absolute. ITs not some relative kind of thing.
Take a look at the same situation, but with runners. Assume you have two fat guys who do nordic walking. They are a 3 miles apart and travel at the same velocity (v=3 miles per hour). At a given time, a marathon runner passes the first one at twice his velocity. How much time passes til he passes the second walker?
We switch into the system which is positioned half way between the walkers again. Now they appear at rest. The velocity at which the runner runs, relative to that system, is obviously 3 miles per hour. Since the walkers are 3 miles apart, it takes him an hour to pass the second walker.
The velocity of the runner depends on the system you choose to observe. The speed of light doesnt depend on the system. ITs absolute
Does a "laser" beam stay a "laser" beam for ever or does it disperse?
If it does, I would also imagine the ship would shoot itself in the foot essentially traveling at the same speed as the laser, 1 bump into it and it would blow up the ship, I would assume.
Is there an additional propelling force in a laser beam beyond the speed of light? If it has no mass it cannot be propelled, so it would end up hitting the ship that shot it.
Several questions:
1.) Does a laser beam disperse?
Yea, obviously. Laser is just tightly bundled light. Over time, it disperses. For the question, I just chose laser because its a common sci-fi weapon. Nothing special about it, comparing it to normal light.
2.) The ship cant travel at the speed of light. And the light doesnt get reflected back if thats what you mean. The laser widens, but it doesnt magically get reserved back into the ship.
Imagine light being radiated in a cone. In a laser, the opening angle of that cone is just really small.
3.) I take propel as an expression for some force being at work. That is not the case. Light travels at the speed of light because it does. Force is bound to mass, and light is massless, so theres no easyway to describe the mechanisms in terms of everyday stuff.
4.) If light cant be propelled, it would slow down.
Nope. A fundamental law of physics is the fact that you keep your velocity, UNLESS some force acts upon you. Since light is massless, and force depends on mass, lights direction and velocity can not be changed.
100 light years.
The laser fired by 'behind craft' is 1 light year away. But the other craft is traveling at 99% the speed of light. So in 1 light year when the laser reaches the place where the 'ahead spacecraft' was, the ahead spacecraft will have already traveled another .99 light years. 1 light year latter; it will be .98, another light year latter .97 and so forth.
Of course, this is assuming you could 'point' a beam of light under the mentioned conditions.
Warning: I'm ignorant on the topic and this is just my best guess.
The laser fired by 'behind craft' is 1 light year away. But the other craft is traveling at 99% the speed of light. So in 1 light year when the laser reaches the place where the 'ahead spacecraft' was, the ahead spacecraft will have already traveled another .99 light years. 1 light year latter; it will be .98, another light year latter .97 and so forth.
Of course, this is assuming you could 'point' a beam of light under the mentioned conditions.
Warning: I'm ignorant on the topic and this is just my best guess.
In a mirror, the following happens:
The photon arrives at the mirror, gives its energy to an electron, the electron gets excited (the photon ceases to exist here. Since it has no mass, the only reason it exists is because it contains kinetic energy). Couple nanoseconds later, the electron is done being excited and radiates a new photon in the opposite direction.
That way, you see the image somewhere else, but its not the original light.
Heres a new one:
You have a stick that reaches the sun. Assume the sun to be a rigid body, not some burning gas thing. The only physical aspect we are interested in is the relativistic length. The stick does especially not bend under gravitational forces or something.
Now you try to poke the sun with your stick. Does the sun get poked? If yes, how long does it take for the poke to arrive at the sun?
You have a stick that reaches the sun. Assume the sun to be a rigid body, not some burning gas thing. The only physical aspect we are interested in is the relativistic length. The stick does especially not bend under gravitational forces or something.
Now you try to poke the sun with your stick. Does the sun get poked? If yes, how long does it take for the poke to arrive at the sun?
A stick that reaches the sun from the Earth?
Ignoring all physical limitations, it would arrive instantly? Or, the time it takes you to push enough for the stick to touch the Sun depending on how far it was initially.
