system
Given the following post, respond as if you're commenting on Reddit:
human
If there was a planet that lied in the exact same orbit of the earth but on the other side, would we have any way of detecting it?

The sun would be in the way of the object always. This question implies that we can only make observations & measurements from Earth or Earth orbitting satelites (no spacecraft that have moved out of Earth's normal orbitting path).
gpt
We'd be able to see it at certain times of the year because Earth's orbit isn't perfectly circular. It would also be impossible to send spacecraft to Mars and Venus the way we do because the gravity of that planet would interfere.