Name: 14 分鐘內講解所有物理知識 (ALL OF PHYSICS explained in 14 Minutes)
Uploaded: 2024-09-15T16:13:56.000Z
Duration: 14 min 20 s

分詞構句

You're on a rock, floating in space, surrounded by more rocks, and gas, and a bunch of nothing, mainly.

你在一塊石頭上，漂浮在太空中，周圍是更多的石頭、氣體和一堆什麼都沒有的東西。

To understand, let's look at a little bit of physics.

要理解這一點，我們先來看一點物理學知識。

To find out what kind of magic this is, we'll have to go back in time.

要想知道這是什麼魔法，我們必須回到過去。

This is Gravity Guy, but most people call him Isaac Newton.

這是萬有引力傢伙，但大多數人都叫他艾薩克-牛頓。

One important thing he said is that force equals mass times acceleration.

他說的重要一點是，力等於品質乘以加速度。

Force is a push or pull on something in a certain direction.

力是對某一方向的推力或拉力。

Mass tells you how much of something there is, and it's also a measure of inertia, but we'll get to that later.

品質告訴你某種東西有多少，它也是慣性的量度，但我們稍後再談。

And acceleration is the derivative of velocity with respect to time, but that's too many big words for my taste, so let's just say it's how fast your velocity is changing.

加速度是速度相對於時間的導數，但我不喜歡用太多大詞，所以就說它是速度變化的快慢吧。

The key takeaway is that if you apply force to a fixed mass, you get a predictable amount of acceleration.

主要啟示是，如果對固定品質施力，就會獲得可預測的加速度。

If you know all the forces acting on a basketball midair, you can predict with 100% certainty if the ball will go in the hoop or your neighbor's windshield.

如果你知道作用在半空中的籃球上的所有力，你就能百分之百地預測球會飛進籃圈還是鄰居家的擋風玻璃。

Yep, that must have happened for a reason, said Newton, as he discovered that two masses attract one another, making the apple fall.

牛頓說："是的，這一定是有原因的，因為他發現兩個品質相互吸引，使蘋果掉了下來。

Yes, even you, no matter how ugly you think you are, attract pretty much the whole universe, at least a little bit.

是的，即使是你，無論你認為自己有多醜陋，也會吸引整個宇宙，至少是一點點。

Yep, said Newton, who gave us the law of universal gravitation.

是的，牛頓說，他給了我們萬有引力定律。

In other words, how much do bodies pull on each other given their mass and distance times a constant?

換句話說，在品質和距離乘以常數的情況下，物體之間的拉力有多大？

You see, as the distance increases, the force gets smaller by the square.

你看，隨著距離的增加，力會以平方的形式變小。

That, my friends, is the inverse square law.

朋友們，這就是平方反比定律。

Gravity is also the reason why planets in our solar system orbit the sun.

引力也是太陽系中行星繞太陽運行的原因。

They got their initial velocity when the solar system formed out of spinning gas, and since there's nothing in space to stop them from moving, they'll keep moving.

當太陽系從旋轉氣體中形成時，它們就獲得了初始速度，由於太空中沒有任何東西能阻止它們運動，所以它們會一直運動下去。

The sun is so massive that the force of gravity keeps pulling the planets towards the sun, but the planets are fast enough to essentially fall towards the sun but miss it, and this goes on forever, creating a round orbit.

太陽的品質非常大，萬有引力不斷將行星拉向太陽，但行星的速度足夠快，基本上是落向太陽，但卻錯過了太陽，這種情況永遠持續下去，形成了一個圓形軌道。

Most orbits are not perfectly round, but more egg-shaped, and Pluto's orbit is just a complete mess, but you get the idea.

大多數軌道都不是完美的圓形，而更像是蛋形，冥王星的軌道更是一團糟，但你應該明白這一點。

In this case, the gravity is what we call a centripetal force.

在這種情況下，重力就是我們所說的向心力。

One thing many people confuse is mass and weight, and no, they're not the same.

很多人都會混淆品質和重量，不，它們是不一樣的。

Mass tells you how much of this blob there is, and weight is the force of gravity the blob would feel.

品質告訴你這個圓球有多大，重量則是這個圓球感受到的重力。

To make things clear, your mass would be the same on the Earth and on the Moon, but the weight you would perceive is different because the Moon has a weaker gravitational pull, meaning a weaker force acting on your mass.

為了說明問題，你在地球和月球上的品質是一樣的，但你感受到的重量是不同的，因為月球的引力較弱，這意味著作用在你的品質上的力較弱。

So, really, you're not overweight, you're just on the wrong planet.

所以，說真的，你並沒有超重，你只是來錯了星球。

All right, enough about Newton, let's break some stuff.

好了，不說牛頓了，我們來分析一下。

If you ever dropped your phone, it might look like this.

如果你的手機掉在地上，可能會是這個樣子。

The answer is energy, you know, the thing kids have after eating gummy bears.

答案就是能量，你知道的，就是孩子們吃完小熊軟糖後的那種感覺。

Energy has the unit joule, and it's not like force, it doesn't have a direction, it's just a number that's kinda chill in there, as a property of a thing.

能量的組織、部門是焦耳，它不像力，沒有方向，它只是一個有點冷冰冰的數字，是事物的一種屬性。

You see, there's two main kinds of energy, kinetic energy and potential energy.

你看，能量主要有兩種，動能和勢能。

In plain English, energy of movement and stored energy due to some circumstance.

通俗地說，就是由於某種情況而產生的運動能量和儲存能量。

For example, when you held your phone, it stored gravitational potential energy due to being held above the ground at a certain height.

例如，當您拿著手機時，由於手機在一定高度上離地，它儲存了重力勢能。

Once you dropped it, that potential energy was converted into kinetic energy as the phone fell.

一旦手機掉落，勢能就會轉化為動能。

Then it smashed into the ground, and the phone absorbed some of the energy, making the screen go BOOM.

然後它砸到了地上，手機吸收了一些能量，螢幕 "嘭 "的一聲碎了。

Work is defined as force applied over distance.

功的定義是施加在距離上的力。

For example, if you lift an apple by 1 meter, you would have done about 1 joule of work.

例如，如果你把一個蘋果舉起 1 米，你就做了大約 1 焦耳的功。

This happened by converting chemical energy stored in your body to gravitational potential energy stored in the apple.

這是通過將儲存在你體內的化學能轉換成儲存在蘋果中的重力勢能而實現的。

As you may have noticed, energy and work have the same unit joule.

您可能已經注意到，能量和功的組織、部門相同，都是焦耳。

Uh, no, energy is the total amount of work that a thing could possibly do, and work is just the stuff that actually happened and required energy.

呃，不，能量是一件事物可能做的功的總量，而功只是實際發生的、需要能量的東西。

If you try to lift a weight that's too heavy for you, you'd feel like that took a bunch of work, right?

如果你想舉起一個對你來說太重的重量，你會覺得費了很大力氣，對嗎？

Well, yes, but your feelings are invalid in the face of physics.

嗯，是的，但在物理學面前，你的感覺是無效的。

Mathematically, no work has been done, because work is force applied over distance, and since you didn't move the weight at all, no distance means no work.

從數學上講，沒有做功，因為功是施加在距離上的力，由於你根本沒有移動重物，所以沒有距離就意味著沒有功。

The key thing to remember about energy is that it cannot be created or destroyed, only converted.

關於能量，最重要的一點是它不能被創造或毀滅，只能被轉換。

Okay, but a car that's moving has kinetic energy.

好吧，但行駛中的汽車是有動能的。

When the car stops, assuming the car doesn't smash into a wall, where does that energy go?

當汽車停下時，假設汽車沒有撞牆，那麼能量去了哪裡？

When you apply the brakes, there's friction between the brakes and the wheels, causing the car to slow down, and creating heat as a byproduct.

當您踩下剎車時，剎車和車輪之間會產生摩擦，導致汽車減速，併產生熱量作為副產品。

That heat is then dissipated into the surrounding air, and that makes the molecules in the air move faster.

這些熱量會散發到周圍的空氣中，從而使空氣中的分子運動得更快。

Things that move have kinetic energy, so ultimately, the kinetic energy is transferred from the car to the air.

運動的物體都具有動能，是以動能最終會從汽車轉移到空氣中。

With this knowledge, we can define that temperature is just the average kinetic energy of atoms in a system.

有了這些知識，我們就可以定義溫度只是系統中原子的平均動能。

You see, all atoms, not just molecules in the air, wiggle.

你看，不只是空氣中的分子，所有原子都會擺動。

The faster they move, the hotter things get.

它們移動得越快，溫度就越高。

All that talk about hot stuff, I think it's time we talk about thermodynamics.

說了這麼多熱門話題，我覺得是時候談談熱力學了。

It tells us that jumping in lava is probably a bad idea, but more importantly, the absolute mess that is entropy.

它告訴我們，在熔岩中跳躍可能是個壞主意，但更重要的是，熵絕對是一團糟。

Literally, it tells you how much disorder there is in a system, indicating the number of possible states a system could be in.

從字面上看，它告訴你一個系統中存在多少無序狀態，表示一個系統可能處於的狀態數量。

The sun will obliterate the ice cube and turn it into water.

太陽會抹去冰塊，把它變成水。

Looking at the structure of ice and water, we can see that ice is more neatly organized than water, which just kind of goes all over the place.

觀察冰和水的結構，我們可以發現，冰比水更整齊有序，而水則到處亂竄。

Also, the water could look like this, or this, or even this, but the ice will always look a little something like this.

此外，水可以是這樣的，也可以是這樣的，甚至可以是這樣的，但冰看起來總是有點像這樣。

In total, the system went from low entropy to high entropy, meaning more disorder and more possible microstates.

總之，系統從低熵變為高熵，意味著更多的無序和更多可能的微觀狀態。

The whole universe is on an unstoppable path to higher entropy.

整個宇宙正不可阻擋地走向更高的熵。

It's also the reason why time seems to only go forwards.

這也是時間似乎只能向前的原因。

Practically, entropy tells us that some forms of energy are more useful for doing work than others.

實際上，熵告訴我們，某些形式的能量比其他能量更有助於做功。

Burn some gasoline and your car will move, spitting out heat and gas.

燃燒一些汽油，你的汽車就會動起來，噴出熱量和氣體。

That heat and gas is pretty much gasoline, just in the form of higher entropy.

這些熱量和氣體幾乎就是汽油，只是以更高的熵的形式存在。

And as you can imagine, this stuff won't really make your car move, and the gas won't spontaneously turn back into liquid gasoline, meaning the form of gasoline with lower entropy is more useful for doing work.

可想而知，這東西並不能讓你的汽車真正動起來，汽油也不會自發地變回液態汽油，這意味著熵值較低的汽油形式更有助於做功。

Okay, but if you put some water in the freezer, will it not decrease in entropy?

好吧，但如果你把一些水放進冰箱，它的熵不會減少嗎？

Yes, but the fridge is not an isolated system and will heat up the room more than it will cool down the water, increasing the total entropy.

是的，但冰箱並不是一個孤立的系統，它對房間的加熱作用大於對水的冷卻作用，從而增加了總熵。

Some electrons apparently moved through some wires and let there be light.

一些電子顯然穿過了一些導線，從而產生了光。