Comment on How can we see other galaxies, and how do we know how many galaxies there are?
LastYearsIrritant@sopuli.xyz 1 week agoThis is a great comment, but just for completeness, the Type Ia Supernovae is only one part of the Cosmic Distance Ladder.
en.wikipedia.org/wiki/Cosmic_distance_ladder
We can start with small, easier to measure things, and work our way outwards to more and more complicated measurement techniques. Most of these techniques overlap each other and can be used to confirm our measurements.
One of the big unsolved questions in cosmology is that many of our measurements disagree, this isn’t a “problem” just an unsolved question, and as a result, we don’t know how far away things are to the accuracy we would like. That being said, we still know how far away they are to a pretty damn close approximation.
The interesting thing is, the better we get at measuring how far away things are, the more our measurements differ from each other. There’s a lot of reasons why this might be, but one of them is that a Type Ia Supernovae might not be as standard as we think it is.
crapwittyname@feddit.uk 1 week ago
I chose a simple standard candle for a quick explanation, but yes, these are all independently verified by other methods, which in turn verify each other etc. Parallax is a good one: at one side of the earth’s orbit and the other, you measure the relative position of the thing you want to know the distance to, which is just like closing one eye then the other. Distant objects move less in your vision than close objects do.