Could aliens be watching Earth right now?

Yes, it’s physically possible—but there is no good public scientific evidence that aliens are watching Earth right now.

The most realistic version is not “aliens looking at us live,” but distant observers detecting signs of Earth from far away: our atmosphere, city lights in principle, radio leakage, or the fact that Earth has biology. Because light and radio signals take time to travel, anyone many light-years away would be seeing Earth’s past, not today. For example, a civilization 100 light-years away observing Earth optically would see Earth as it was about 100 years ago.

A closer alien probe in our solar system could, in theory, observe Earth in near-real time, but we have no confirmed evidence of such a probe. So the best answer is: possible in principle, unknown in practice, and currently unsupported by confirmed evidence.