Ever wonder how far the human eye can see? Binoculars and telescopes help us see more clearly, but what about with the naked eye? You may be surprised to learn just how far our amazingly intricate eyes can see.
First, A Quick Lesson In Sight
When we see an object, we are really seeing light reflected off the object and beaming into our eyes (specifically the retinas). We can only see a coffee mug on the table because the lamp in the corner is lighting it up for us.
The light from the lamp bounces off the mug and into our eyes, “showing” us the mug. This is true for everything we can see, from dust on the shelf to the cars down the street.
Seeing Nearby Objects
Let’s start small. Here are relatively close objects that humans can see:
1/2 mile: The Burj Khalifa building in Dubai is a half-mile straight up. Standing near the base, you can easily see the top.
1 mile: The bottom of the Grand Canyon is over 1 mile down. If you were standing on a sheer-faced edge of it, you could see campers at the bottom.
3 miles: The edge of the Earth (as it curves) is about 3 miles from viewing point to the edge. Ever stare out at the ocean? The farthest point you can see is about 3 miles out.
6 miles: The average 747 passenger plane flies at about 6.6 miles up in the air.
50 miles: On clear days, city buildings can be seen from 50 miles away (if you’re standing on the ground).
Seeing Very Distant Objects
Ready to see a little farther? All you have to do is look up:
22,000 miles: Communication satellites orbiting the Earth are about 22,000 miles up. On a clear, dark night, you can see these satellites as moving specs of light.
239,000 miles: The moon is almost 239,000 miles away, yet it’s large enough (and reflects enough sunlight) that we can see the details in its surface.
93 million miles: Earth’s orbit is 93 million miles from the sun.
746 million miles: Saturn is the most distant planet we can see with the naked eye. Squint hard enough and you can even make out its rings.
The Farthest We Can See
2.5 million light-years: The Andromeda Galaxy is a rotating cluster of 1 trillion stars. This is the farthest object humans can see with the naked eye, thanks to the vast amount of light coming from its burning stars.
With today’s technology, to would take 94.5 billion Earth years for humans to travel to its edge. That’s pretty far for being the farthest object we can spot.
In reality, humans have infinite visibility—it just depends on how large and how bright an object is. We could technically see far beyond the Andromeda Galaxy if there was another bigger and brighter source of light.
But it still doesn’t hurt to eat your carrots.
Originally posted 2018-07-03 16:31:35.