system
Given the following post, respond as if you're commenting on Reddit:
human
If an alien civilisation at the same level of technological advancement as our own was to discover earth in the same way as we are now discovering exoplanets, would  they be able to tell there was life here? If so, how?
gpt
If an alien civilization was looking at the sun, measuring its brightness and its spectrum over a very long time, they'd notice that it oscillates every 12 years or so. They could then conclude that Jupiter exists. If they measure the spectrum as Jupiter passes in front of the sun, they might be able to figure out what gasses are in Jupiter and how hot it is.

If they made even more precise measurements they might be able to make similar conclusions about the other planets, including Earth. But using the technology that we use, they could not detect us.