>>714564286That's not what I am talking about., the vacuum only applies a force on Chell that pulls her vertically towards the portal, it's irrelevant to my point.
The Moon is moving relative to the Earth at a kilometer per second, since it's orbiting around it. If I teleported from the surface of the Earth to the surface of the Moon with all my momentum relative to the Earth conserved, I'd be flung out away from the surface of the moon at 1km/s or splattered on the surface. Chell doesn't, she exits at a very modest velocity because of that vacuum you talked about, which means all her momentum relative to the Earth (and the moon) is gone, only her momentum relative to the entrance portal was conserved and copy-pasted to the exit portal.