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This is a video about nothing.

No, it's actually about nothing.

Well, what is nothing?

Let let's think about it.

Let's think about nothing.

Are you picturing a black void, an empty room, opens space, actual space?

Or are you trying as hard as you can to not think about anything at all?

The thing is no matter how hard you try, you can't think about nothing.

But I can think about this.

This is something that means nothing.

But is zero nothing, if it's something?

Are there other nothings besides this?

Or is nothing just an idea that we came up with, so we could better understand all the somethings in the universe.

And if nothing is just the opposite of everything, does it actually exist?

(dramatic music) Hey, smart people, Joe here.

I was just sitting here doing nothing.

Well, actually that's a lie, I was doing a lot.

I mean, sitting is something.

But I wasn't exactly trying to sit, I just let gravity take care of that.

But I was also doing a lot of things that I wasn't even aware of.

I was breathing, pumping blood through my body.

I was digesting the food that I ate earlier, and transforming the energy in that food into heat.

I mean, it takes a lot of doing something just to be alive.

But nothing is a word we use a lot.

And what's so funny?

Nothing.

What are you up to tonight?

Nothing.

What's wrong?

Nothing.

What did you learn?

Nothing.

Most of the time when we say, nothing, we don't actually mean, nothing.

The absence of all magnitude or quantity, not anything, non-existence.

The idea of complete and total nothingness, a true empty void, has bothered many great minds throughout history.

And depending on where in history we look, the idea of nothing has existed, and not existed.

And existed again, and then not existed.

Here are five pieces of candy, I'm gonna share them with, okay.

Wow, thanks, I gave away five pieces of candy.

Well, how many do I have now?

Well, zero, this feels like the easiest math problem ever.

But for much of human history, we didn't have any way to explain what's left.

Because even this most obvious kind of nothing, is not an idea that we've had forever.

We had to invent it, so that we could better describe reality.

People have been counting stuff for longer than we know, and organized systems of tallying numbers have been around for thousands and thousands of years.

Exactly who invented zero, and when?

Well, we don't know for sure, but what we do know is that the first zero wasn't a number meant to be used in calculations like 5 minus 5 equals 0.

It was just a place holding symbol, like this.

The numbering system we use today is a positional system, it's based on powers of 10.

And the value a digit represents, depends on where in the number that it sits.

I mean, we don't even really think about this when we look at numbers.

But this zero isn't just a number, it represents none of something.

Here's what I mean.

When you read 2021, you know that that's and 2000, 20 and 1 years.

That zero isn't the zero that's halfway between one and minus one, it's just a symbol to hold that place that means no 100.

So if we saw this number, now the zero means nothing in the tenths place.

You probably learned all of this before you could even add and subtract.

But this way of using zero was a major innovation in how humans think about numbers.

One that was separately developed by many cultures from the Mayans to the Babylonians.

But zero as a placeholder is not the same as mathematical nothing, as in what's left of my candy.

Indian astronomers may have been the first to consider nothing as something, a number with no value.

It started with a strange question.

What happens when you subtract a large quantity from a small one?

This was another big shift in how people thought about numbers because if I have five pieces of candy, you can't take seven of them, there's not two pieces of uncandy here.

It doesn't work, unless you think of numbers like this.

This is a number line, negative on one side positive on the other.

And a very important point in the middle, they called it Sunya, the nothingness.

And they developed a symbol for it, a squashed, egg-shape that looks pretty familiar.

This Sanskrit, manuscript is dated to the 3rd or 4th century.

You see that dot on the bottom row?

It's the oldest known use of zero as we think of it today.

Now, other mathematically advanced cultures like the Greeks, didn't use nothing or zero as part of their math because their way of looking at the universe simply didn't allow zero to exist.

The Greeks tended to think of numbers using geometric shapes.

To them pi wasn't 3.1415, yada yada, yada.

To them pie is the ratio of a circle circumference to its diameter.

Explaining zero with geometry or shapes?

I mean, describing a shape with no sides would mean trying to explain something that isn't there, a void.

Zero is an important part of modern geometry, but the idea of a void, of nothingness that went against the prominent philosophy of ancient Greece.

There's this old saying, "Nature abhors of vacuum."

And you can tell it's old because no one uses the word abhors anymore.

The saying means, nature despises empty space or nothingness.

And it's what ancient Greeks like Aristotle and his friends believed.

Aristotle came up with this thought experiment, drop a marble in honey, and it'll sink pretty slowly.

Drop a marble in water or some medium thinner than honey, and it'll move faster.

The less stuff there is to move through, the faster something moves.

Well by Aristotle's logic, something moving through a void, true nothingness, would move infinitely fast, and that just didn't make sense.

So to Aristotle and his friends, the void was impossible.

Instead, they believed that what we think of as empty space was actually filled with a mysterious, a fifth element beyond earth, water, air, and fire, the ether.

This later came to be known as quintessence, which literally means the fifth essence, an invisible something, everywhere that there seemed to be nothing.

But another group of ancient Greeks, smarty pantses or smarty togas began to think that nothing was real.

They developed an idea called atomism, that everything is made of lots and lots of tiny indivisible things.

Not quite the same as atoms as we think of them today, but lots and lots of small somethings moving in nothing, in a void.

Where there's no atoms, there's just emptiness.

But what is empty?

This box is empty, right?

Of course, technically, scientifically speaking we know this box isn't empty.

I mean, obviously there's air in the box, a cubic meter of air down near the ground has something like 10 trillion, trillion air molecules That's definitely something.

And that's not all that's in here, there's dead skin, other dust particles, germs.

But what if we sucked all that stuff out, would we be left with a true nothing?

Well, totally empty space might be impossible.

We think of the vacuum of space as nothing, but there is stuff even in the emptiest places in the universe.

One cubic meter of the interstellar space between galaxy contains maybe as few as a 100 particles, but still something.

And beyond particles, electromagnetic radiation from X-rays to radio waves exists everywhere.

And just consider this, that no matter where we look in any direction, we see electromagnetic radiation dating from the earliest days of the universe traveling everywhere as the universe itself expands.

There are some particles we can't detect and particles that seem to blink in and out of existence.

Even the particles we do see are thought to be just visible blips of energy fields that permeate the entire universe like waves cresting above an invisible.

Beyond all this, we think dark energy is a property of space itself, a something that's everywhere space is, even if we can't observe it.

Space isn't nothingness, it's somethingness.

But what about at the very beginning of our universe, maybe there was some nothing that our universe expanded into.

Well, according to most models of physics there can't be anything outside the universe because the universe is by definition, everything.

The universe didn't expand into empty space, space and everything in it expanded.

When ancient Greek thinkers said that a truly empty void couldn't exist, we're realizing they were right, just for the wrong reasons.

(dramatic percussion) Unless dark energies, quintessence.

(dramatic percussion) No, that's not how that works.

That's not how any of that works.

There are other ideas of nothing, like absolute zero.

The molecules and atoms that make up matter are always moving around.

And temperature is a measure of those atoms' kinetic energy.

The faster atoms move around, the higher the temperature.

If we reduce temperature enough that atoms themselves are totally still, that's absolute zero.

But while we've managed to get within a fraction of a billionth of a degree, no one has ever actually cooled anything to absolute zero.

And here too, modern physics tells us, getting to absolute zero is probably impossible anywhere in the universe because of quantum effects, it scales even smaller than atoms.

It's taken us 3000 years of trying to understand the universe.

Do you realize that outside of math, nothing can't exist.

That's a lot to think about.

Let's go back to thinking about nothing for a minute.

Oh, except that we can't.

So what is your brain doing when you try to do nothing?

Well, a few pounds of mushy think-meat in your skull accounts for just 2% of your body mass, but it uses 20% of your energy every day.

Back in 1953, one scientist wanted to find out how much oxygen the brain consumes during vigorous thought.

So we had some people do math problems, and monitored how much energy their brain was using.

Oddly enough, the resting brain appeared to be just as active as the calculating brain.

That experiment didn't get much attention but new technology has let us see even clearer that the brain is up to something when we are doing nothing.

When your mind is wandering, when you're not consciously focusing on the outside world, well, certain parts of the brain spring into action.

Kind of a neural nothing network.

And gram for gram, these brain regions use 30% more energy than regions involved in conscious thought.

And these same regions become less active when we focus on something specific.

The scientists think these brain regions may be where daydreaming happens.

Why spend all this energy letting our minds wander?

Well, it seems to be when our brain analyzes past experiences, so that we can adjust our future behavior.

And some scientists think that when our minds wander or even meditate, it helps us process and store memories.

Thinking about nothing or at least trying to, may help us write the inner story of our lives.

So we can't make nothing.

We can't find nothing.

We can't think nothing, we can't do nothing.

And we can't become nothing either.

Even when we die, the atoms and elements that make up our bodies, the molecules in the brains that held all of our conscious existence.

All of this will eventually become something else.

Not us, but not nothing.

And even when you or I are one day, not here we will leave memories behind in other people's consciousness.

All of us can still be something even when one day we are not here.

Nothing is a lot.

And as always, I hope you learned something.

Stay curious.