Placeholder Image

字幕列表 影片播放

  • Hey, Vsauce Michael here coming to you from my hotel room in London

  • with a little camera that I taped to a bunch of furniture I stacked up.

  • Which is better than nothing, and as you can tell from the title of this video,

  • it's also what we're going to discuss.

  • Nothing.

  • Can there ever be nothing? I mean, we're surrounded by matter all the time.

  • Even this glass is not empty.

  • I know you might think there's nothing in it, but it's full of air.

  • And air is packed.

  • One cubic centimeter of air contains almost

  • 30 quintillion molecules.

  • But if I remove the air from this glass,

  • I can create what is known as a vacuum,

  • an awesome word that uses a double u, but not a w.

  • The challenge, however, is removing all of the air.

  • To this day, the best scientists have been able to do

  • is to create what they call an ultra-high vacuum.

  • At this point, one cubic centimeter

  • of space contains not 30 quintillion molecules,

  • but a mere and amazing 100.

  • To put that in perspective, a vacuum cleaner

  • like you use at home hardly changes the thinness of the air at all.

  • In fact, if you use a vacuum cleaner at sea level,

  • the vacuum created inside the operational part of the machine

  • only has the thinness of air found in Denver, Colorado.

  • If you want thinner air, if you want even fewer particles per cubic centimeter,

  • you're going to have to leave earth.

  • But before we go too far, let's talk about high altitude flying.

  • When you're in an airplane 30,000 feet high,

  • the outside air is very thin and dangerous.

  • So by law, the airplane must keep the inside of that commercial aircraft pressurized

  • so that it only feels like you're no more than 8,000 feet high.

  • The reason it's dangerous is that when air gets that thin,

  • there's not enough oxygen for your brain.

  • This man is about to remove his mask temporarily and with supervision

  • in the actual thinness of the air around him.

  • Within less than a minute, he suffers from hypoxia,

  • a lack of oxygen.

  • Even though he appears to be awake and alert,

  • when told to put his mask back on or else he will die,

  • he does nothing.

  • But a lack of oxygen, a lack of air, a lack of matter

  • can get even more dangerous when you go above 60,000 feet,

  • about 19,000 meters above the surface of the earth.

  • This limit is known as Armstrong's Limit.

  • We all know that the boiling point of water

  • decreases as your altitude increases,

  • and at Armstrong's limit, the boiling point for your own blood

  • drops all the way down to the temperature of your own body.

  • If you reach that altitude without wearing a special suit,

  • bubbles will form inside your blood, and your body

  • will inflate to twice its normal size.

  • But because your internal organs and your skin are flexible, you won't explode.

  • So let's talk about out gassing.

  • Out gassing is why it's so difficult for us to reach an ultra high vacuum.

  • If you remove so much air from this glass,

  • there's fewer than 100 particles per cubic centimeter.

  • The glass itself or whatever material your chamber is made out of

  • will start to lose its own trapped gasses.

  • But materials don't need to be inside partial vacuums to out gas.

  • It happens all the time, and is especially noticeable in confined spaces.

  • For instance, a car.

  • All of the adhesives and chemicals used to make that car

  • will out gas and collect inside,

  • creating what we know as the new car smell.

  • All right, time to leave earth for good.

  • Let's go into the space between planets.

  • Now remember that in a laboratory, the best vacuum we've been able to create

  • is about 100 particles per cubic centimeter.

  • Well, between the planets and our solar system,

  • there is space that only contains ten particles per cubic centimeter.

  • And if you leave our solar system in the innerstellar space,

  • you're only going to find about one particle per cubic centimeter.

  • The real winner though is intergalactic space.

  • Leave the Milky Way altogether and you can find regions

  • where there's only one or two particles per cubic meter.

  • Okay, that's cool and all, but would it be possible

  • to find a region of space where there is absolutely

  • and literally nothing, no matter at all?

  • Well, according to quantum mechanics, no.

  • First of all, you've got gravitational and electromagnetic fields

  • that extend forever, because the particles that cause

  • those fields to happen have no mass whatsoever.

  • And this is what's really mind blowing:

  • there's a thing known as virtual particles that's happening all the time,

  • even around us right now where there's no vacuum.

  • These virtual particles come into existence and then disappear.

  • And we believe they exist for a couple of reasons.

  • One big reason is the fact that our universe

  • continues to expand, even though that shouldn't necessarily happen.

  • Where are we getting that extra force that pushes it, that causes it to keep expanding?

  • Well, these particles that pop into existence and disappear may be the answer.

  • Even crazier is an effect we've observed known as the Casimir Force.

  • If you put two pieces of metal nanometers apart inside a vacuum,

  • they will be pushed together.

  • One of the most popular theories for why this happens

  • is that these virtual particles popping into space and then disappearing

  • are actually reflecting off of the metal.

  • But because the plates are so close together,

  • particles with wavelengths longer than that gap

  • don't get reflected, so there's more virtual particles pushing on the outside than the inside,

  • and the metal plates contact.

  • I know these concepts have gotten pretty crazy,

  • but rest assured that really all it means is that whenever you feel down and feel like nothing matters,

  • you're scientifically incorrect.

  • Nothing matters, there can't be nothing.

  • There's always matter, there's always something.

  • And as always, thanks for watching.

Hey, Vsauce Michael here coming to you from my hotel room in London

字幕與單字

單字即點即查 點擊單字可以查詢單字解釋

B1 中級

‌‌ (‌‌)

  • 6 0
    林宜悉 發佈於 2021 年 01 月 14 日
影片單字