Q:

Theoretically speaking, If you had a super powered light bulb Initially located 1 light year away from an observer, but the observer moved at a constant 99% the speed of light away from the light source, how long would the observer observe the light if the light was turned on for a brief moment of like 4 minutes? would the observer observe only 4 minutes of an illuminated bulb or because of the speed of the observer moving away from the light source would it take longer for all of the light to reach be observed thus making it seem like the light would be illuminated for much longer?

- chase Lewis (age 19)

chandler, AZ, USA

- chase Lewis (age 19)

chandler, AZ, USA

A:

There are two effects involved here. One is that as the bulb moves away from the observer (in the observer's frame) the last light emitted takes longer to get to the observer. The other is that the bulb's clock appear slow to the observer. The net effect is that the light is seen for a time of 4 min*sqrt(1.99/0.01) or about 4 min*14 = 56 min. If the light blinks on and off, the apparent blinking rate is reduced by that factor of sqrt(199), the relativistic Doppler shift factor.

Mike W.

*(published on 03/28/2015)*