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.