eli5: if everything in the universe is constantly revolving at insane speeds, why are the constellations and star patterns the same all the time?
In: Physics
They do but even moving at high speed it takes a huge amount of time to get anywhere new in space. The constellations will change over time, but over tens of thousands of years, far far longer than we have recorded history.
Consider driving on a straight road at night with the moon off to your side. You and the moon are moving quite fast relative to each other, but it still doesn’t seem like the moon’s position is changing quickly because it is so far away from you, it changes over hours not minutes from your perspective.
The Moon is 400,000 km away, the closest star (Proxima Centauri) is 40,000,000,000,000 km away and its just 4.24 light years away.
If you look at a constellation like Orion, the outside two stars on the belt are both about 1200 light years away from Earth and are about 2.75 degrees apart in the sky and around 57.6 light years apart. If you want to wait for them to move to be even 3 degrees apart they’ll need to spread apart by at least 5.2 light years.
The fastest star in the galaxy moves at 8% of the speed of light and it’d take it 65 years to pull that off. Most stars move around 0.03% of the speed of light so expanding their gap by 5.2 light years would take over 17,000 years. Humans have only been around for 10,000 years so the stars have remained relatively constant over our existence.
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