system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: With the new finding of the seven earth sized planets, how will humans determine whether there is life on them and how long would it take to do?
gpt
The planets are 39 light years away, so getting a probe or something over there would take quite hundreds of years or more with our current tech at it's best. Fortunately, we don't have to do that.

The best thing we can do is to look for signs of the kinds of gases life makes: oxygen, carbon dioxide, methane. When Trappist-1's light shines through the atmosphere of one of the planets, we can watch for which spectrums of light are and aren't filtered out by the atmosphere, which tell us what types of gases are in it. 

This is of course not SUPER conclusive, but we'll be able to get proper answers on it within the decade. And there's plenty of other exoplanets out there to try the same tricks on. We've been discovering exoplanets at an enormous rate lately, which is amazing since it took until 1992 to fundamentally find and prove the existence of planets around other stars, and now we've got bucketfuls of data about 'em to sort through and start oogling.