The other day I was talking to my friend/apprentice about star wars when we got on to the subject of the battle of Yavin.

"why didn't they just blow the planet up? Instead of going around it" my friend asked.

Poodoo, I thought I don't know. Think, jedi_iain, think
"well it was a gas giant, so the superlaser probably wouldn't have worked. It probably needs to hit something solid. The laser would just go through."
(Best I could think of at the time, but it actually sounds pretty good)

Pretty good that is, until my friend asks "why then, didn't they just shoot through the planet to destroy the base?"
Once again I had to think quickly to defend my beloved Star Wars.
"well the gas would probably deflect the laser beam and it would miss"
"why didn't they shoot from an angle so the beam hit the planet after it was deflected?"
O.k, I thought I need to come up with something really good this time that he can't possibly question.
"if they fired through the planet, it would reduce the power of the laser beam enough so that it wouldn't destroy the planet, maybe just make a crater in the ground" sensing his next question I quickly added "the rebel base wouldn't be caught in the blast though because it was on the other side of the moon."

This explanation kept him quiet for a bit.

So does anyone else have a better explanation for any of this? I pretty much came up with it all on the spot so I don't know if there is something I missed or an official reason for it or anything.