Answer:
I'm a god. I'm a planet. I measure heat.
It is weightless, you can see it. If you put it in a barrel it will make it lighter?
It is a sound of empty, speak and it'll talk back plenty. But all the more you yack, you'll get the same words back.
What do you use to hoe a row, slay a foe, and wring with woe?
Alive without breath, As cold as death, Clad in mail never clinking, Never thirsty, ever drinking
What sphinxes employ and players enjoy.