Eli5: Why does light travel so fast?
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Light travels extremely slowly, relative to the scale of the universe. It only seems fast to us because we’re a tiny ant colony living on a speck of dust floating in space.
It takes over 4 years, at the fastest possible speed that anything can travel in our universe, to get to the nearest star to our solar system, Proxima Centauri. A round trip, assuming you had infinite energy to spend and could survive infinite g forces, could never be accomplished in less than about 8.5 years. By anything, not only spaceships but also light and information. And that’s just to get to the nearest star, in a galaxy full of hundreds of billions of stars.
If humanity is never able to figure out a way to travel faster than light, then it’s unlikely that humanity will ever spread to any significant distance, and almost certainly will never leave the milky way galaxy, even assuming that we avoid killing ourselves and manage to survive for millions of years into the future. It takes light over 100,000 years to cross the milky way galaxy from end to end. And that’s just our dinky little galaxy. There are trillions of other galaxies in the universe that we can see, and on average it takes about a million years for light to travel from one galaxy to the next nearest galaxy.
Light seems fast to us, but on the scale of the universe, it is stupidly slow. Whoever designed the simulation we’re in really didn’t want us to travel too far away from home.
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