system
Given the following post, respond as if you're commenting on Reddit:
human
Regarding interstellar colonization: Is it possible to find a nebula with an earth-like atmosphere?

I was thinking about this the other day and wondered that if we can find planets with our technology why haven't we tried finding a nebula like our atmosphere?
gpt
Firstly, nebulae are really, really low density - more than 10^(14) times less dense than our atmosphere. That is considered an excellent laboratory vacuum here on Earth! As you can imagine, you wouldn't do very well when put into a lab vacuum chamber...

The Earth's atmosphere has also been heavily affected due to it being a rocky planet - we've collected lots of heavier elements (notably Nitrogen and Oxygen), but are relatively devoid of Hydrogen and Helium, because they just float off into space. This means that we've sifted out the heavier elements over a long period of time - this doesn't occur in a gas cloud, meaning that they are still mainly composed of Hydrogen and Helium.