The Andromeda and Milky Way galaxies are moving toward each other due to mutual gravitational attraction. This mutual gravity…
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Do We See Multiple Versions of a Star When Looking Back Through Spacetime?
No. When we look at an object in the universe we see that object as it existed when the…

How Do Astronomers Know That The Universe is Currently Expanding?
Astronomers observe a regular progression of galaxies which are expanding at progressively higher velocities as they measure galaxies at…

Can One Measure the Expansion of the Universe Within Our Solar System?
The universe is currently expanding at a rate of about 75 kilometers per second per mega-parsec. If we consider…

What are the Average Distances Between Stars and Between Galaxies?
Your estimate for the average distance between stars is reasonable. Your estimate for the average distance between galaxies is…
Visualizing the Expansion of the Universe
The list of visualizations that you provide are some of the best descriptions of the expansion of the universe. …