Why doesn’t any monochromatic light not on the natural spectrum of an element do it? Or rather, any cluster of nearby frequencies to accommodate redshift.
Just needs to be bright enough to see. I think I’m convinced that at ~1x galaxy you can do it easily, owing to the 1000x factor from using the mass of the stars rather than letting them burn. But not as clear for 1/1000.
If there were a single point source with weird spectrum, halfway across the universe and outside of any galaxy, about as bright as a galaxy, would we reliably notice it?
Sure, you could try to cover the sky with lasers whose frequencies encode some mathematical fact. I think we might notice such a thing in the course of doing regular redshift measurements.
Why doesn’t any monochromatic light not on the natural spectrum of an element do it? Or rather, any cluster of nearby frequencies to accommodate redshift.
Just needs to be bright enough to see. I think I’m convinced that at ~1x galaxy you can do it easily, owing to the 1000x factor from using the mass of the stars rather than letting them burn. But not as clear for 1/1000.
If there were a single point source with weird spectrum, halfway across the universe and outside of any galaxy, about as bright as a galaxy, would we reliably notice it?
Sure, you could try to cover the sky with lasers whose frequencies encode some mathematical fact. I think we might notice such a thing in the course of doing regular redshift measurements.