Hey, Vsauce. Michael here.
And Jake. And Kevin. And we are in Santa Monica, which of course means that the “V” in “Vsauce”
will stand for the Roman numeral five, as in five questions from you guys. Our first question comes from “@notch”. He didn’t ask this of me in particular,
but I love how non-intuitive the answer is.
Assume an Earth that’s perfectly spherical and a rope, stretched around the equator snugly. What would happen if that rope was just,
say, six meters longer? Six meters isn’t very much, but because of the relationship
between a circumference and a radius, six meters of extra rope would allow the
entire rope to not fit snugly around the earth, but one meter above it, all the way around. That’s cool, but what if instead of a rope we used something more rigid, like a structure, a bridge and we built the bridge all the way around the Earth. And then, all at once, destroyed its supports. Would it float?
Clearly the earth’s gravity would pull the structure down, but down is in the opposite direction
for the other side of the bridge. Well, it turns out such a scenario would be incredibly
unstable. Earth’s gravity isn’t equal everywhere, and if you follow @tweetsauce
you saw some great graphs showing just how much gravity changes, simply based on the density of rock below. When you factor in the Sun and the Moon,
you wind up with a bridge structure that is not gonna stay where it is.
If the bridge itself was indestructible, it would start violently hula hooping around the
earth, crushing things. But there’s no known material strong enough to do that.
Instead, you would wind up with bridge pieces flying everywhere. A sphere around the earth would be a bit
more stable, but a ring? Not so much. The ring, even if spinning, would rapidly
break apart into smaller pieces. Last week you guys asked me a question
that I have always wondered. Let’s say I was stranded in the
mountains, waiting for rescuers to arrive, but it was going to take a while.
I had plenty of snow and plenty of water, but I was hungry – dying of starvation – would it make sense to amputate one of my legs and eat it?
I mean, it kinda makes sense, right?! I’d have my entire leg to eat as food,
which would probably fill me up and I would have one less limb that I would need to keep alive. The only problem is that the trauma your
body would endure from the loss of a limb would greatly exceed the benefit you would get
by eating the food. You’re better off keeping that limb on your body, because your body’s process of using
reserves of energy is more efficient than the process of digestion.
So keep the leg on and let it wither away, keeping you alive.
Don’t cut it off and eat it and digest it. How does hair know when to stop growing? It’s a good question, because the hair on my arm, which there’s a lot of, never grows any longer than this. And if I were shave my arm off,
it would grow back and stop right where it is right now. But head hair is different. For instance, my hair – what’s left of it –
would keep growing if I didn’t cut it. But no other animal has that situation.
You don’t see wolves out in the forest saying, wow, look how long my hair is
getting, I better get to the barber shop. So, why do humans have head hair that grows so long, but body hair elsewhere that stops
seemingly right when it’s supposed to. Well, first things first. The hair on your head will not keep growing for ever. Typically around six years of growth is the limit. When hair grows, it is in what is known as its
anagen phase. And for hair on your head that phase can last up to six years. But the anagen phase of hair elsewhere
on your body – eyebrows, eyelashes – is much shorter. Except in cases like this guy, whose
eyebrows grove like head hair and have allowed him to set the world record
for longest eyebrows. Humans probably lost their fur coats,
their thick body hair, because it didn’t really help us hunting
and running around sweating on the savannah. And unlike other animals,
us humans had discovered fire and could make clothing to keep ourselves warm
without needing a built-in fur coat. To be sure, long hair that falls over
your ears and neck can keep you warmer. But leading theories also argue
that long head hair may be our fault. A result of the fact that early humans picked mates that could grow longer hair on their heads. Mates that could do that were probably healthier and in colder climates literally had a built-in hat to keep their body warm. One of the questions I get the most
is about eye floaters. Those little dots or squiggles that you see
in your vision, especially when looking at a bland scene, like the clear blue sky. Eye floaters are made out of little fibrals
that occur in your eye as you age. And you can’t look directly
at them because they’re inside the fluid of your eye. Turning your eye to look
at them simply causes the fluid to move and the floater as well.
But the thing about eye floaters that I love the most is that they are almost always microscopic. You can’t see them with the naked eye, except when they are inside your eye. If you were to pull an eye floater out,
you wouldn’t be able to see it. But in your eye, it’s close enough to the retina to leave a shadow on the retina and
that’s what you see when you see eye floaters. Finally, how much would Wikipedia weight if i printed all the text out and bound it into books?
Well luckily, there’s a Wikipedia article about this very topic. The English-language Wikipedia contains
about two billion three hundred and forty five million words, which, if printed at the density of the
Encyclopedia Britannica, would equal about 1,759 volumes. Which would look like this. Altogether they would weigh about 7,000 pounds. If you’re between the ages of 13 and 18, you may want to check out the Google Science Fair. It’s an amazing competition.
These guys are great. They actually helped make that Earth bridge animation for me. So be sure to check out GoogleScienceFair.com. And I’ll keep checking out Los Angeles.
I’m here with Kevin and Jake from Vsauce2 and 3 for the first time ever. The three of us have never been in one
location simultaneously until now, so be sure you’re subscribed to us, because amazing videos will come soon. And as always, thanks for watching.