Placeholder Image

Subtitles section Play video

  • this video was made possible by simple contacts.

  • Get $20 off your contacts by clicking the link in the description or by entering the code real life floor at check out The limits of human vision is an interesting thing.

  • If you're fortunate enough to have 2020 eyesight, it means that you can clearly read a small Rove text from 20 ft away.

  • But the best recorded vision in humans is 2010 eyesight, which means that these extremely lucky people can see things clearly at 20 ft away, as if they were only 10 ft away.

  • For the normal person, everybody sees the world a little bit differently than everybody else does.

  • And I mean that literally not only in terms of clarity or blurriness, but also in terms of just how much can be viewed.

  • If we took you right now and placed you in the middle of the ocean on a clear day with nothing to obstruct your view, you'd probably be able to see in every direction for around five kilometers.

  • But that can change depending on your height.

  • The limit to your own personal visibility of the world is determined by two things the curvature of the earth's surface, and how high up your eyes are that are doing the viewing.

  • That's because the higher up your eyes are the more of the earth's surface you can see before it curves away from you.

  • The average American male is 5 ft 9.5 inches tall, which allows a visible range of about three miles in every direction from sea level.

  • The average American woman is 5 ft four inches tall, though, which puts a slight negative modifier on their viewing range, so it becomes about 2.8 miles.

  • That's not a huge variation, but radical height differences can cause that at 7 ft one shack has a higher visible range of 3.3 miles and burn.

  • Taylor had only 2 ft eight inches, had a visible range limited toe only two miles.

  • However, Robert Pershing Wadlow, the tallest human to have ever existed at 8 ft 11 inches tall, had a massive visual range of 3.7 miles, probably the furthest of any human who has ever lived.

  • If all of these people were standing on a flatboat in the middle of the ocean, Robert would be able to see another boat emerging from the horizon 1.7 miles further out than Verne Taylor could possibly see it.

  • But of course you can actually see things further away than just a few miles.

  • You only need to get your eyes further up into the sky.

  • One of the tallest observation decks anywhere in the world is inside the Burj Khalifa in Dubai.

  • At 555 m up from all the way up here, your line of sight extends out to 84 kilometers.

  • In addition to whatever you could see based on your personal height, this is so high up that it becomes possible to see the coast of Iran all the way across the Persian Gulf under optimal conditions.

  • It's also so high up that it causes some other weird situations up on the higher levels.

  • It becomes possible to see the sun setting several minutes after it's already set on the surface once again because of the earth's curvature, and your viewing perception from so high up allows you to see further around that curvature.

  • This has led some local Islamic clerics in Dubai to rule that those living above the 80th floor in the building should wait two additional minutes before breaking their Ramadan fast.

  • And those living above the 150th floor should wait three additional minutes to give the sun Mawr timeto actually set for them.

  • In fact, being near the Burj Khalifa actually allows you to witness the sunset twice in the same day.

  • I don't know what that means for Ramadan, so let me know in the comments.

  • But essentially you could watch the sunset happened on the surface and then take the elevator up to the observation deck, which is fast enough that you could get all the way up to the top and witnessed the sunset happen all over again.

  • Similarly, to buildings being high upon mountains or hills can also increase how far away you can actually see something on the earth's surface.

  • In theory, standing atop the summit of Mount Everest should give the largest field of view anywhere in the world out up to 340 kilometers in every direction.

  • If Mount Everest was in the middle of Germany, that would give you the ability to see over roughly the entire country.

  • But Everest is kind of surrounded by other mountains, which spoils the view.

  • The longest line of sight that anybody can achieve on Earth is by standing atop the summit of Don Cova in Kyrgyzstan and gazing a ludicrous 538 kilometers away to the Hindu Tog Mountain Pass in China.

  • This is only possible to see under the right weather circumstances, but nowhere else on the planet.

  • Is it possible to see something else with your naked eyes that's over 500 kilometers away for reference.

  • That would be like standing in New York City and being able to see Toronto or standing in Los Angeles and being able to see Sacramento, or for a European comparison standing in London and being able to see either Edinburgh or cologne in Germany.

  • But so far we've only been talking about how far away you can see something on earth surface.

  • Your eyes can see things that are much, much further away when you turn them upwards towards space.

  • Most of the stars in the night sky that you can see are located within a few 1000 light years away from you, a light year, meaning the the distance that light travels within one year, the furthest single object that your naked eye can see while on earth is V 76 to cast in the Cassiopeia Constellation at 16,308 light years away.

  • But much further away than that is the Andromeda Galaxy, a collection of objects which represents the furthest possible limit of your own naked eye sight into the cosmos.

  • Andromeda is faintly visible without the need for a telescope at a massive distance of approximately 2.5 million light years away.

  • For most of human history, this served as the furthest limit for our vision and perception of the universe until the advancement of telescopes.

  • Now we can see things that our ancestors never could have, like the Galaxy GNC 11 at 32 billion light years away from us.

  • Somewhat confusingly, you may remember from previous videos that I've made that the universe itself is only about 13.8 billion years old.

  • The reason that GNC 11 is 32 billion light years away is that it probably doesn't exist anymore.

  • It's so far away from us that we're witnessing what it looked like 13.4 billion years ago because that's how long it's taken the light to reach us for us to observe it here on Earth.

  • But this galaxy probably isn't at the edge of the universe.

  • It's just impossible for us right now to see anything that's probably beyond it.

  • The universe is expanding quicker than the speed of light can move to catch up with it, which means that the light of objects more distant than GNC 11 will never reach us here on Earth, which means that will never be able to see what lies beyond.

  • This problem will become worse and worse as time goes on, though, as the universe continues to expand eventually, sometime between four and six billion years from now, the only objects in the night sky that will remain visible on Earth, if it still exists by then, will be our own small local cluster of Galaxies.

  • The universe as we know it today that's filled with trillions of Galaxies, will be totally invisible and unknowable to civilisations of the future, which means that they may mistakenly think that the universe is much smaller than it actually is.

  • But we may think that ourselves.

  • A few billion years ago, it was probably possible to see even more Galaxies than we can currently see today, since the universe hadn't expanded quite a much.

  • There's no telling what lies beyond the limit of what we can see in the universe and will probably never know.

  • It's a serious and unsolvable problem that will per permanently affect humanity's collective vision.

  • But back on Earth, your own personal vision problems can actually be solved and solved easily.

  • My normal eyesight is naturally 2080 which means that without any correction, I see things that are only 20 ft away, as if they were actually 80 ft away for a normal person's eyesight.

  • And so I've been wearing contact since I was 12 years old in order to see clearly if you wear contact lenses, too.

  • But you find yourself dreading your annual appointment to renew your prescription, just like I always have.

  • You should know that simple contacts can really help you out.

  • Simple contacts lets you renew your expired contact lens prescription and reorder your brand of lenses online.

  • Within minutes, they bring the doctor's office to wherever you currently are.

  • You could take the simple contacts vision test online in five minutes.

  • A real doctor will review it and if your vision hasn't changed, renews your prescription to.

  • And if you have an unexpired prescription, you just upload a photo of it or your doctor's info and then order your lenses within minutes.

  • Simple Contacts offers every brand of lenses with extremely reasonable prices.

  • The prescription is only $20 compared to an annual appointment, which can be up to $200 without insurance.

  • They have some of the best prices on contacts, and the shipping is free.

  • But best of all, you can get $20 off your first order right now by clicking the link in the description at simple contacts dot com slash real life floor or by entering the code real life floor at check out.

  • It's important to mention, though, that this isn't a replacement for your periodic full eye health exam.

  • You still need those, but this is the most convenient way that I've seen to renew a prescription and reorder your contacts.

  • If your vision hasn't changed so once again, help support real life floor by checking out simple contacts and get $20 off by following the link in the description or by using the code real life floor at check out.

this video was made possible by simple contacts.

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 universe earth prescription vision eyesight visible

What’s the Farthest Away Thing You Can See?

  • 4 2
    林宜悉 posted on 2020/10/24
Video vocabulary