Would it be possible to build a sensor that detects the blackest blacks from the noise background?

Tau.Neutrino said:

Would it be possible to build a sensor that detects the blackest blacks from the noise background?

Ooh. There is a size problem. Stellar mass black holes are only tiny, much smaller than planets. Galactic mass black holes tend to be further away, except for the one in the Milky Way.

If background is cosmic microwave background then it doesn’t look possible with current technology. For the centre of the Milky Way the cosmic microwave background is blocked by dust. But I shouldn’t rule it out because the James Webb may just be able to see black holes by the amount of infrared radiation they block. This IR is not as ubiquitous as cosmic microwave radiation, but there’s a lot more of it around that visible light. You’d have to know exactly where to look, because the James Webb is not a survey instrument.

If the black hole passes in front of a star then that gets much more interesting. It would be possible to see the star’s change in brightness even with current telescopes.