Register to reply

Can you move fast enough towards light so that it has a period of 0?

by stu dent
Tags: light, period
Share this thread:
stu dent
#1
Nov20-12, 11:14 PM
P: 20
at what speed must i be moving towards a beam of light in order for the wavelength to have a period of 0?

would it be the speed of light? would it need to be greater than the speed of light? if so, what period would it be at if i were movign at the speed of light?

i mean, maybe the question is dumb, and the answer is obvious that it would be the speed of light, but with relativity, the answer seldom turns out to be obvious i find.
Phys.Org News Partner Science news on Phys.org
'Office life' of bacteria may be their weak spot
Lunar explorers will walk at higher speeds than thought
Philips introduces BlueTouch, PulseRelief control for pain relief
bcrowell
#2
Nov21-12, 12:15 AM
Emeritus
Sci Advisor
PF Gold
bcrowell's Avatar
P: 5,598
Quote Quote by stu dent View Post
would it be the speed of light?
Yes. The Doppler shift factor is [(1-v/c)/(1+v/c)]1/2, which only equals zero for v=c. Since you can't move at v=c, this never happens.
stu dent
#3
Nov21-12, 09:50 PM
P: 20
ya.. but light does.

it's almost kind of predictable that would be the case, and yet, an interesting thought.

and predictably i guess again, as v→-c it goes to infinity.


here's a related question. how do we know whether or not there's a bunch of stuff in outer space that's moving away, or towards us, by rates of speed that would yield a period, as of yet, undetected by us? or detected by us, and yet, unrecognized.


Register to reply

Related Discussions
How fast is a character that can move at the Speed of Thought? General Physics 5
The kinetic energy of particles increase and they move fast. Classical Physics 0
How to move fast and not get smooshed General Engineering 2
Calculating how fast a motor can move something in horizontal motion Engineering, Comp Sci, & Technology Homework 2
How fast does the planets move away from the Sun ? Astronomy & Astrophysics 0