[jasonlfunk]

I’m always a bit skeptical about these sorts of things. Perhaps I’m just ignorant about the methods used.. but the amount of data we can get from the most distant known galaxy can’t be very much. How confident can we be that the shift in observed light or whatever is actually from the presence of Oxygen and not one of probably countless other causes, both known and unknown.

[itishappy]

Pretty confident. Emission spectra are very specific. The relationship between specific emission lines are invariant to changes in wavelength (redshift/blueshift), and they're complicated enough that it's not too big a deal to weed out false positives.

Here's a textbook example:

https://images.nagwa.com/figures/explainers/469167813067/17....

[floxy]

https://en.wikipedia.org/wiki/Spectroscopy#Atoms

[interludead]

Skepticism is fair, but the confidence comes from how well we understand atomic spectra

[piker]

Is that about as well as we understand the formation of the universe? /s

[astroH]

a lot better...we can excite these atoms in a lab and simply measure what comes out. often times don't even need a model because spectroscopy can be fully empirical for many transitions

[setopt]

Spectroscopy is a very straight-forward and mature technique. Saying that “we see these spectral lines in this picture so there must be oxygen” is not considered any more controversial than “we see a bright dot in this picture so there must be a star”.

[acdha]

There are a lot of very smart people working in astronomy, they review each other’s work, and they compete for jobs and funding. Does it really seem likely that none of them have thought to validate basic assumptions?

Having family members who do that for a living, I can tell you that’s a huge chunk of the job. Astronomers all know that they have significant limitations in the data that they can collect and spend a lot of time thinking about ways they can test different theories. It would be a career-making move if some grad student could come up with a new explanation which changes the previous understanding and given the ratio of degrees granted to jobs the incentives really wouldn’t favor covering anything up.