Just been on a space video kick lately and am pretty ignorant about most of it.
One thing I see a lot of these videos saying is that the expansion of the universe seemed to be slowing down until around 5 billion years ago.
How can we tell that it was slowing down 5 billion years ago if it started speeding up afterwords? Like how do they map out the universe and say “yeah it was slowing down until this time.”
Is it just a theory or is this something commonly accepted as fact? Appreciate any info and thanks! 🙂
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We plot stars, their type and luminosity to develop a cosmic yard stick which we can use to measure things like galaxies and how far other galaxies are. We plot those and notice the emission spectrum red shifts in these same stars in other galaxies the further away they are. Also the shape, type and luminosity of galaxy changes the further in time you go. We can measure the expansion of the universe also by measuring the total radiation emitted in space of a certain radio frequency or compare the emissions of distance stars like I mentioned early. Amalgamating this helps us form a model to make logical inferences such as certain formations of subatomic particles several years of the Big Bang which alters the expansion of the Universe.
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