Quote:
Originally posted by MageB420666
Sorry I'm asking this so late after the thread was started, but...
If time slows as you approach the speed of light, wouldn't that imply that you are traveling slower the faster you go?
Velocity= Distance/time
So for a ship to travel at .99C for one year(according to the ships clocks) to return to earth seven years later mean that the ship was actually travelling slower than .99C since the distance travelled would be the same, but the time the ship was gone would have increased causing the resulting velocity to be lower?
|
Well, remember it is all relative. Time doesn't speed up as such. Your second hand on your watch would not appear to be spinning faster! However the clock on your spaceship would appear to have counted fewer seconds then the one on Earth.
You don't define a point of reference? Space ship travelling at .99c relative to the Earth? Then the ship is travelling at the speed of .99c. On the spaceship you are also travelling at the same speed. You have time contraction and length contraction by the same factor (lorentz transform I think? I can't remember totally). So luckily they cancel out!
If I'm travelling at almost the speed of light relative to elswhere and turn on my torch the photons coming out of it will still move at c relative to me.
Quote:
Originally posted by MageB420666
As for not being able to accelerate something beyond the light, What would happen if you got a ship up just below the speed of light and fired a gun foward? Would the bullet accelerate to lightspeed and then just stop accelerating?
|
Again it's relative! If I'm on this ship (in an inertial frame i.e. not accelerating) then my world is not moving. I then fire a gun and it will travel at a bullet speed! Now if I'm on the Earth where the ship is already moving with a speed of approximately c the bullet will accelerate as much as allowed without reaching c (as it can not have infinite energy to reach it). However due to relativistic effects the bullet will still appear to move as you would expect. It's a huge concept to get to grips to but it's true.
Quote:
Originally posted by MageB420666
What about light speed itself, light travels slower when it's going through something,i.e. the atmoshpere. So does that mean it speeds back up after leaving the atmoshpere, and if it does what accelerates it?
|
The short answer is that it doesn't slow down as such. The 'speed' you are referring to is the speed it can propogate through a medium. This is for the photons to be absorbed by electrons and then readmitted. So in effect nothing accelerates it. The photons travel at c through all mediums it's just that the medium gets in the way and appears to slow it down. WHen their are no electrons in the way it will travel naturally at c.
Quote:
Originally posted by MageB420666
If light itself doesn't have any mass, then why is it affected by gravity, which is the force of attraction between masses?
|
Although they don't have mass they do have momentum and so interact with other objects. General relativity suggests that gravity is actually the warping of space-time by a massive body. Imagine if you stretch a piece of cling-film over a bowl. Place a heavy item such as a large marble in the middle and it will stretch the plastic and make a well shape. This warping of space-time is what light actually follows. This explains the Newtonian concept of gravity involving two-masses.
Well I think that's it but ask again about any points I haven't made well. I'm sure that it won't make a lot of sense! I tried!