same time? Could it cause an earthquake, or would we not even be able to tell?

Well, first things first, let's talk about the Earth's rotation.

The Earth spins, that's why we have night and day, and it spins quickly. At the equator,

the Earth is spinning at more than 1,000 MPH.

Now, a spinning ice skater can speed up by moving mass closer to the center, and the

Earth is no different; In fact, if you get down on the ground right now and move your

mass closer to Earth's center, technically, you will speed up Earth's rotation, making

this day shorter.

Now, the change that you would make to the Earth's rotation is way smaller than we could

even measure, but it is calculable, and the impact can be quite impressive when you talk

about redistributing more mass than just one person.

For instance, last year, the earthquake in Japan redistributed so much of Earth's mass

towards the center, that every day since then has been 1.8 microseconds shorter.

But, that was a giant geological event. What can us humans do to the Earth all on our own?

I mean, there are more than 7 billion of us now- what if we all got together in one place

and jumped?

Well, what would that even look like?

Interestingly, if you took the entire human population of Earth and had them all live

in one place with the same density that people live in in New York City, you could fit everyone-

all of us- into the state of Texas.

But that's living, not standing around in a crowd, which is how we would probably want

to do the jump.

If every single person alive right now on Earth stood shoulder to shoulder, you could

fit all of us into the city of Los Angeles. It would be an incredible sight to behold-

a mere 500 square miles containing every single person on Earth.

Ok, so, then we jump. What happens?

Unfortunately, not much. I mean, we're all awesome people here on Earth, but our collective

mass compared to the mass of the entire Earth? It's like, nothing.

In fact, Dot Physics calculated that if all of us were to get together in one location

and all jump 30 cm into the air at the exact same time, we would push Earth away from us

a tiny amount.

Earth would only move away from us about 1/100th of the width of a single Hydrogen Atom. And

here's another thing: because we're all jumping and the going back to where we started, Earth

is just going to move back to where it started.

So, our big jump won't be able to change Earth's position in space, but, c'mon, 7 billion people

all jumping together? That's gotta be able to cause some sort of seismic activity, right?

So, let's say you have a lot of people all together in one place, and you have them all

jump on: 1-2-3!

Did you feel that? Well, the BBC did this with 50,000 people, and discovered that a

kilometer and a half away, it only registered a .6 on the Richter scale. You would need

7 million times more people than even live on Earth right now to jump at once to recreate

the earthquake that recently happened in Japan.

So, even though we're all awesome, compared to the size of the Earth, we're not much.

But don't get too discouraged. Our collective jump would contain a lot of energy. The Straight

Dope calculated that even if only the people who lived in China got together and jumped,

their jump would be the equivalent of 500 tons of TNT. Of course, 500 tons of TNT doesn't

do much to an Earth that weighs 6 sextillion, 588 quintillion tons.

To make yourself feel more powerful, pick a card. I've got 10 of them here, let's say,

hmmm, you choose this one. Boom, congratulations, we have just decimated this deck of cards.

Why? Well because, technically, decimate does not mean "obliterate completely."

Deci=10. It means to take away 1/10th of something. So, the next time you take a quiz and don't

do so well on it- you only get 10%, well sure that's an "F", but, by getting 10% of them

right, you DECIMATED that quiz.

And since we've been talking about crowds, let's talk about YouTube crowds. YouTube audiences,

that view count that you see at the bottom of every video, and get some perspective on

it.

We'll being with Dunbar's Number.

It's an estimation of the maximum number of people we can have stable, social relationships

with at a given moment, and it's based on the size of our neo-cortex.

These aren't just acquaintances, these are people you have social contact with; a network

where you know how everyone relates to everyone else. And the number is usually given to be

somewhere between 100-230, which means that when a YouTube video receives more than 230 views

from different people, more people have seen that video than you could ever realistically

hope to know well, at a given moment.

If a video has more than 100,000 views from different people, more people have seen that

video than you will ever meet in your life. And by meet, I mean shakes hands with, learn

their name, talk with them for a bit.

I mean, think of it this way: you and me, we're only statistically expected to live

around 28,470 days. So, even if you were to meet someone, 2-3 people every day of your life

(including when you were a baby), you still wouldn't meet as many people as have seen

that YouTube video with 100,000 views.

But, keep this in mind: even though you, or even a large group of us, can't do much to

change Earth's location or rotation, we can affect it a little bit. Newton's Third Law

guarantees this. If you weigh 150 pounds, the Earth is pulling you down with a force

of 150 pounds. But, you are also pulling up on the Earth with a force of 150 pounds.

If you fall 3 meters, the Earth has pulled you down 3 meters. But, you have also exerted

an equal and opposite force on the Earth. Of course, it's a lot bigger. So, if you fall

3 meters, you pull the Earth up about one-billionth of the width of a Proton...which ain't bad?

So, the next time you move your body-the next time you jump, Felicia- think about this:

you just affected the Earth as much as it affected you. You've got that kind of power.

Speaking of power, you all should go check out "Geek & Sundry", Felicia's new channel.

It's one of my new favorite things...And, as always, thanks for watching.