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How far the human eye can see is directly dependent on how many particles of light, or photons, a distant object emits. The reason we can see something like the Andromeda Galaxy 2.5 million light years away is because the galaxy's one trillion stars collectively emit enough light for a few thousand photons to hit each square inch of Earth every second; on a dark night, that's plenty to excite our retina. However, since those photons left the Andromeda Galaxy 2.5 million years ago, we are seeing the galaxy as it was 2.5 million years ago. More distant objects need something more sensitive than our eyes are capable of seeing. Which is why we invented telescopes.
Some really basic science is involved, not magic, nothing mystical, nothing supernatural about it, and yes the universe is old enough, not as many believe only a few thousand years old.
How far the human eye can see is directly dependent on how many particles of light, or photons, a distant object emits. The reason we can see something like the Andromeda Galaxy 2.5 million light years away is because the galaxy's one trillion stars collectively emit enough light for a few thousand photons to hit each square inch of Earth every second; on a dark night, that's plenty to excite our retina. However, since those photons left the Andromeda Galaxy 2.5 million years ago, we are seeing the galaxy as it was 2.5 million years ago. More distant objects need something more sensitive than our eyes are capable of seeing. Which is why we invented telescopes.
Some really basic science is involved, not magic, nothing mystical, nothing supernatural about it, and yes the universe is old enough, not as many believe only a few thousand years old.
Light travels at a speed of 186,000 miles per second or 700 million miles per hour.
700 million times 24 = 16,800 (sixteen billion eight hundred million) twenty four being the number of hours in a day.
So the light from the sun to the earth is 8.3 minutes. You see the light from the sun is it what the sun was doing 8.3 minutes before.
The distance between the sun and earth is an astronomical unit. This is an easier number to compute, being 93 million amounts to the number being really big and hard to calulate. So in 24 hours the astronomical units equals 173 or au.
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