Cirrus Light 
"[@Scrounge":](/1012990#comment_4908960
)
If the portals were to some random point in deep space, then she could've drained Earth's atmosphere :p
Which brings me to the realization that Equus and Earth must have the same atmospheric pressure.
Arg! Noooooo! I reject this! This is terrible and drives me mad. Sure, lower gravity could explain Pegasus flight, but only a thicker atmosphere could explain how airships work as they do in Equestria! But no pressure differential in the portals creating wind...
Maybe the portals went somewhere super hot in Equestria, like, 120°F, and it was a really cold evening in human world, like, 30°F, so they had different weather-dependent densities but equal pressure thus no wind...
Sciencepone of Science!
If the portals were to some random point in deep space, then she could've drained Earth's atmosphere :p
Which brings me to the realization that Equus and Earth must have the same atmospheric pressure.
Arg! Noooooo! I reject this! This is terrible and drives me mad. Sure, lower gravity could explain Pegasus flight, but only a thicker atmosphere could explain how airships work as they do in Equestria! But no pressure differential in the portals creating wind...
Maybe the portals went somewhere super hot in Equestria, like, 120°F, and it was a really cold evening in human world, like, 30°F, so they had different weather-dependent densities but equal pressure thus no wind...