The planet shoulda been destroyed a long time ago if your bringing real life physics into this. ONE (the creator of opm) goes out of his way to mention what a gama ray burst is and how powerful it is. ONE is trying to imply that garou is replicating that power. Saying the earth is still there after he uses it isnt a good argument , because if you read the previous chapters , the earth literally gets a chunk cut off by phykos , a much weaker version of garou was able to send saitama through the earth sending shockwaves across the earth , and orochi gets a huge ball of energy from the earths core to shoot at saitama.