# Archived Question on light waves

#### matthewfullhart

ok, so I'm sitting in class one day, and my physics teacher is talking about light... and since we had just finished up a section on sound, I was wondering whether there is such an effect as a "light-boom"

that is to say, if we were to have a spaceship that could go exactly at the speed of light, and we attached a flashlight to the front of the ship, could we not cause the buildup of light rays much the same as we can with sound and airplanes? if so, couldn't we make a gigantic weapon with this? let's say that there's life on a planet near alpha centauri, and we go to war with them... couldn't we just send out a ship with a big flashlight on the front, cause the buildup of light particles over the span of 4.3 years, and then decelerate just before hitting the planet? 4.3 years of light would definitely do some amount of damage to their planet, even if it's just blinding everyone on the surface...

I asked my teacher this, and he said something to the effect of "no, because of time dialation." I realize his point, but that makes me wonder how the red shift works, if this doesn't...

sorry if I confused anyone, and if anyone knows why this can/can't occur, could you please do so? it's been bugging me.

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#### Flyx

ok, so I'm sitting in class one day, and my physics teacher is talking about light... and since we had just finished up a section on sound, I was wondering whether there is such an effect as a "light-boom"

that is to say, if we were to have a spaceship that could go exactly at the speed of light, and we attached a flashlight to the front of the ship, could we not cause the buildup of light rays much the same as we can with sound and airplanes? if so, couldn't we make a gigantic weapon with this? let's say that there's life on a planet near alpha centauri, and we go to war with them... couldn't we just send out a ship with a big flashlight on the front, cause the buildup of light particles over the span of 4.3 years, and then decelerate just before hitting the planet? 4.3 years of light would definitely do some amount of damage to their planet, even if it's just blinding everyone on the surface...

I asked my teacher this, and he said something to the effect of "no, because of time dialation." I realize his point, but that makes me wonder how the red shift works, if this doesn't...

sorry if I confused anyone, and if anyone knows why this can/can't occur, could you please do so? it's been bugging me.
The teacher is correct, this cannot happen. The speed of light is the same for all observers, so there is no possibility of a 'light-boom'.

This concept is explained here: http://newt.phys.unsw.edu.au/einsteinlight/jw/module3_weird_logic.htm

It also mentions time dilation, since that is how both observers measure the speed to be the same.

#### Tallus Bryne

What about cerenkov radiation? Isn't that somewhat comparable to a "light boom" ?

"Question on light waves"

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