Difficulties with interstellar travel

1. Jul 27, 2006

vincentm

According to Relativity, if a ship traveling at nearly the speed of light through interstellar space diffuse atoms (mostly Hydrogen, becase simply that is the most abundant atom in the universe, right?) would strike the front of the ship with increased mass, causing radiation. My question is how is this mass increased on the part of the atom?

Last edited: Jul 27, 2006
2. Jul 27, 2006

Staff Emeritus

If the ship is travelling fast relative to the atom, measured in the atom's frame, then the atom is travelling at the same speed in the opposite direction, measured in the ship's frame. That's just good old Galilean relativity as when you're driving along and you see the telephone poles moving backwards relative to you. What special relativity adds is that each of the two, ship and atom, experiences the other as Lorentz transformed.

BTW, I'm moving this thread to the relativity forum, where it belongs.

3. Jul 27, 2006

pmb_phy

The change in mass is due, not to the stucture of the atom (or any particle for that matter) but is due strictly due to a combination of Lorentz contraction and time dilation. Recall that there is a frame in which the atom is at rest and in that frame the particle has a given structure which will not change when your frame of reference changes.

Pete

4. Jul 27, 2006

pervect

Staff Emeritus
You should note that there are two sorts of mass in relativity. There is "relativistic mass", which is rather outdated, which increases with velocity. There is also rest mass, which does not increase with velocity.

See for instance:

http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html

"Does mass increase with velocity"