i know its measured in lightyears but im watching a video on the james webb telescope and the discovery of huge galaxies and how we have to rethink the beginning but how do they know how old the galaxies are by just pictures? i imagine they have a lot of other things that tell them more information but still. it seems damn near impossible to even tell what anything is especially with how small and warped it is too. thank you i appreciate any info on this. im just throwing the math flair since theres no space
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There are a number of ways to measure long astronomical distances but one you may be interested in comes from the discovery of something called [cepheid variables](https://en.wikipedia.org/wiki/Cepheid_variable).
This is a type of star that pulses in brightness. There is a constant relationship between how bright it is and how fast it’s brightness pulses. So by measuring the frequency of its pulsing and it’s apparent brightness from earth, you can calculate how far away it is. So when we spot a Cepheid in some distant Galaxy, we immediately have a way of approximating the distance to that galaxy.
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