> wouldn't observers on earth just end up wrongly believing they are seeing a different type of an element? It would be very very very unlikely. The spectrum

> wouldn't observers on earth just end up wrongly believing they are seeing a different type of an element? It would be very very very unlikely. The spectrum of an ionized atom is not just a single line that you could easily mistake for another: there is a sequence of lines for each electronic level. There's also a lot more structure when you have molecules: in this case you also have lines associated to changes in the rotational and vibrational state of the molecule, and these also combine with electronic transitions to produce even more lines with characteristic spacings. For example, the simplest molecule, H2, has such a rich spectrum some people spent decades in the 50s to fully characterize it. > is it possible for gravity or other forces to produce spectral lights of similar elements than the original one or is it a very unique fingerprint not similar to close by elements? Yes, there's the gravitational redshift: it affects light emitted near a massive object such a black hole and it has been observed. The effect is very small, but I guess it could potentially shift the frequency of a line of element X to near the nominal frequency of a line of element Y. However, the redshift applies to all lines, so it's very easy to recognize you're looking at a shifted spectrum if you see more that a single line. > Also, if gravity can bend light (blackholes), how come it cannot attenuate it? To attenuate light you necessarily need some kind of dissipative process, so light has to be at least partially absorbed by something and its energy converted to something else. In a vacuum this is really not possible. Maybe with the inclusion of some very high energy process like γγ → e⁺e⁻ or the gravitational equivalent of pair production, but these are really way out of the energy ranges of molecular and atomic spectra.