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  • Hey, Vsauce, Michael here, and what do you say we get outta here...to space, and into

  • an orbit, that way we could just float around and be free from the influence of gravity.

  • Except not really...

  • Astronauts orbiting around the Earth experience pretty much the same gravitational pull that

  • you and I are feeling right now. The major difference is that those astronauts are falling,

  • constantly, towards Earth; but, their angular velocity is so large that they're falling just

  • as fast as Earth curves away from them. Now, of course, this is nothing New...ton's Cannon

  • hasn't already taught us.

  • Gravity makes stuff fall, and, in particular, Newton realized that it makes objects accelerate

  • towards the Earth the same amount, independently of how fast they're moving horizontally. That's

  • called relativity. And, of course, orbiting is just falling, but falling where you move

  • horizontally fast enough that the earth falls away faster. In order to successfully fall

  • and miss the Earth, unless you dug a tunnel, you need to be travelling at over 17,000 MPH,

  • or, 8 KM every second. So, you'd probably incinerate from friction with the air, well

  • before you had a chance to enjoy the trip.

  • Of course, Newton's thought experiment involved the Earth, but on something smaller, like

  • the Moon, the cannon wouldn't have to throw it's projectile nearly as fast for it to complete

  • an orbit. In fact, if you had a powerful enough gun, on the moon, and you fired that gun at

  • the horizon and then waited a little bit, you could get hit in the back of the head

  • by the same bullet.

  • Henry calculated that the bullet would have to travel about 1,600 m/s, which is exactly

  • how fast the Paris gun fires.

  • Now, that's a powerful gun- it's no squirt gun- but, if you had a squirt gun, out there

  • in space, and you fired a stream of water at the sun, how much water would it take to

  • put out the sun? I mean, in general, putting water on something hot would cause that something

  • hot to lose some heat, especially since the water will be frozen because it's out there

  • in space. But, here's the issue: the Sun is not a big ball of hydrogen on fire; instead,

  • the Sun is powered by fusion.

  • Fusion of Hydrogen nuclei, which is kind of like the chemical bonds between the Hydrogen

  • and Oxygen that make up water, except on a much smaller, and much more powerful scale.

  • Now, before I get tackled by nuclear physicists from one side, and chemists from the other,

  • let me explain...

  • A bond of any sort, whether between planets, molecules, atoms, nuclei, or quarks, is just

  • a happenstance where two or more particles together have a lower total energy than when

  • they were apart. Like, if you get married and your taxes go down. So, when you form

  • a bond, that extra energy that the two solitary particles had is released, and because of

  • a little relation we called "E=mc2," this actually means that the mass of the pair goes

  • down a little bit too.

  • For example, every fusion reactions turns a little bit of Hydrogenous mass into light.

  • Sunlight, for example, amounts to a loss of 100 quadrillion kg each year. That's the equivalent

  • of a medium sized asteroid. But stars have a lot of mass, and the more massive a star

  • is, the hotter it burns. And adding a bunch of water to the sun would only cause it to

  • be more massive, so it would burn brighter, not go out. Of course, it would also burn

  • faster, which means that its life would be shorter.

  • For instance, if you were to add 20 solar masses of water to the Sun, you would decrease

  • its life expectancy from the current 5 billion years to only a few hundred million more years.

  • But there's a faster way to put out the sun. Take that water, or whatever material you

  • want, and shoot it into the sun in a way that causes everything to get spread out and scattered

  • so that there's no longer the critical density needed for fusion to occur. Now, no matter

  • which avenue of putting out the sun you pick, both would be a disaster...literally, disaster.

  • From "Dis," meaning "against," and "aster" meaning star, you would have literally turned

  • our own star against us.

  • If you were somehow able to avoid that disaster by magically appearing in inter-galactic space,

  • here's a fun experiment to try: take out your gun, and fire a bullet. That bullet will be

  • forever alone.

  • That's because the universe is expanding, and if you were a few megaparsec's away from

  • the Earth's galactic cluster, on average those galaxies would be 200 km father away from

  • you every passing second. In space terms, 200 km per second is pretty slow- it's barely

  • as fast as the solar system orbits the center of the Milky Way. And, stars closer to the

  • center of the galaxy can orbit 10 times faster. But, a measly bullet travels only a few km

  • every second and would have no chance of reaching the receding galaxies, ever.

  • It makes you realize how tiny we are compared to the scale of the universe. But, it also

  • makes you realize how close together we all are here on Earth. Of course, to get from

  • one side of the Earth to the other, you have to fly over half the sphere...

  • So, what if instead there was a tunnel through the Earth? Let's jump over to my channel,

  • Minute Physics, to see what happens. Click here, and I'll see you on the other side.

  • Oh, and, as always, thanks for watching.

Hey, Vsauce, Michael here, and what do you say we get outta here...to space, and into

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宇宙での銃 (Guns in Space)

  • 89 5
    watt chen に公開 2021 年 01 月 14 日
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