[America_Right]

so.... if the moon formed from ejecta of a collision then does that mean what hit the baby Earth was bigger than the moon or maybe the same size?

Bigger than the moon. Mars-sized. Mars is roughly twice the size of the moon. It stands to reason, seeing as that a good bit of the "stuff" from the impactor would have been left behind on Earth, while the ejecta turned into the moon.

[canuck_conservative]

Mars is roughly twice the size of the moon.

Note that that's diameters. For the Moon - Mars - Earth, the ratios are roughly: 1 - 2 - 4

Volumes would be the cubes of those: 1 - 8 - 64

So the Moon, at only 1/64th Earth's volume, is actually a small chunk.