Space Wars

One space battle cruiser after another shoots powerful laser beams that destroy the enemy’s space battle cruiser. We see the powerful red laser beams strike the opponent, and we hear the explosion as the object blows apart. What wonderful physics can be learned here?

Answer

Don’t try to learn your physics from space battles. Practically everything is incorrect, except the ability to cause something to explode if your weapon can dump enough total energy into the target in a short time! The laser beams, no matter how powerful they are, would not be seen en route. Seeing them requires that a reasonable amount of light be scattered back to you along their paths. But there is practically nothing in the vacuum of space to scatter off. A few hydrogen atoms per cubic meter are all there is out there.

The explosion would not be heard at all. Sound requires a medium for its transport, and the vacuum of space is not a material medium able to conduct sound waves. You will feel something, the impact of the bits of the exploding debris from the enemy battle cruiser because they travel unimpeded from the explosion volume to your spaceship. Their speeds may be enormous, so they could do significant damage if your shields are not in place.