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。

Oh hey, look at that!

哦，嘿，看看這個！

The rocks are going around the gas!

石塊正繞著煤氣走！

Hold on.

等一下

What the heck is going on here?

這到底是怎麼回事？

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。

Wait, did I say a little bit?

等等，我說的是一點點嗎？

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。

Okay, not that far.

好吧，沒那麼遠

Stop!

停下！

Yeah, that's perfect.

是啊，太完美了。

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。

Now, what do all these words even mean?

這些詞到底是什麼意思？

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。

Whoa!

哇哦

Did an apple just fall on my head?

是蘋果掉到我頭上了嗎？

Yes, Newton, it did.

是的，牛頓，的確如此。

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。

Hey, can you put that on paper?

嘿，你能寫在紙上嗎？

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？

Bigger mass, bigger pull.

品質越大，拉力越大。

Bigger distance, smaller pull.

距離大，拉力小。

Actually, a lot smaller pull.

實際上，拉力要小得多。

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。

Hey, that's Newton's first law.

嘿，這就是牛頓第一定律。

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。

Actually, that's kind of a lie.

事實上，這有點像謊言。

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。

What the hell, ground?

搞什麼鬼，地面？

Why'd you do that?

你為什麼這麼做？

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。

So, they must be the same thing?

那麼，它們一定是一回事嗎？

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。

AKA, the conservation of energy.

又名能量守恆。

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。

Like this.

就像這樣

The faster they move, the hotter things get.

它們移動得越快，溫度就越高。

That is temperature.

這就是溫度。

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。

For example, get an ice cube.

例如，拿一塊冰塊。

No, not that one.

不，不是那個。

Yeah, that's perfect.

是啊，太完美了。

And put it in the sun.

然後把它放在陽光下暴晒。

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。

This trend applies to everything.

這種趨勢適用於一切事物。

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。

Wanna see some magic?

想看看魔術嗎？

Whoa, what just happened?

哇，剛才發生了什麼？

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。

What is going on here?

這是怎麼回事？

Objects have a fancy something called a charge.

物體有一種叫做 "電荷 "的東西。

It can be positive or negative, or if you have the same amount of both, an object is neutral.

它可以是正的，也可以是負的，如果兩者的數量相同，物體就是中性的。

Electrons have a single negative charge.

電子帶有單個負電荷。

The flow of electrons is called electric current.

電子的流動稱為電流。

To describe it, we use three parameters.

為了描述它，我們使用了三個參數。

Current, voltage, and resistance.

電流、電壓和電阻。

Current is the amount of electrons passing through a wire in a given amount of time.

電流是在一定時間內通過導線的電子量。

Voltage is what pushes the electrons to move, but simply put, it's a difference in electric potential, so you can imagine it as a slope that goes from high potential to low potential, where the flow of current goes downhill.

電壓是推動電子移動的動力，簡單地說，它是電勢差，所以你可以把它想象成一個從高電位到低電位的斜坡，在這個斜坡上，電流向下流動。

And resistance is pretty self-explanatory.

而阻力是不言自明的。

This is Coulomb's law.

這就是庫侖定律。

Wait a minute, this is just Newton's law of gravitation in disguise!

等等，這只是變相的牛頓萬有引力定律！

This tells us that electric charges attract each other in a similar way masses do.

這告訴我們，電荷之間的相互吸引與品質之間的相互吸引類似。

Opposites want to cuddle, while like charges literally couldn't think of a more disgusting thing than to be with one another.

對立的人想要擁抱，而像收費一樣的人簡直想不出比和對方在一起更噁心的事情了。

These four equations explain pretty much all of electromagnetism, but don't be scared just because they look scary.

這四個方程幾乎解釋了電磁學的全部內容，但不要因為它們看起來嚇人就害怕。

I mean, yeah, they do, but it's simpler than it seems at first.

我的意思是，是的，他們是這樣做的，但比一開始看起來要簡單得多。

The first one states that if there is an electric charge, there will be an electric field, or this big E, emerging from it.

第一種說法是，如果存在電荷，就會產生電場，即這個大 E。

Add another, and you have an electrostatic field.

再加一個，就是靜電場了。

These lines tell us in which direction a charged particle would feel a force at any given point.

這些線條告訴我們，帶電粒子在任何給定點都會感受到哪個方向的力。

The second one tells us the same for magnetic fields, and even though electric charges are cool and can be alone, magnetic poles are not.

第二個問題告訴我們，磁場也是如此，儘管電荷很酷，可以單獨存在，但磁極卻不是。

They're very lonely, and there will always be a north pole together with a south pole, and a single pole can never be alone.

它們非常孤獨，南極和北極永遠在一起，單極永遠不會孤獨。

Okay, now here's where things get kinda freaky.

好了，現在事情變得有點怪異了。

You know how electric charges only act on other charges, and magnets only affect other magnets?

你知道電荷只能作用於其他電荷，而磁鐵只能影響其他磁鐵嗎？

Well, that's only true if they're not moving.

嗯，只有他們不動的時候才是這樣。

The third and fourth Maxwell equations tell us that a moving magnet creates an electric field, and a moving charge or electric field creates a magnetic field.

麥克斯韋第三和第四方程告訴我們，移動的磁鐵會產生電場，移動的電荷或電場會產生磁場。

One consequence of this is that current can seemingly come out of nowhere, by moving a magnet next to a conductor.

這樣做的一個後果是，只要將磁鐵移到導體旁邊，電流似乎就會憑空出現。

The moving magnet creates an electric field, which makes the electrons inside the conductor go crazy.

移動的磁鐵會產生電場，使導體內的電子瘋狂運轉。

That is called induction.

這就是所謂的歸納法。

In other words, electric and magnetic fields are so tightly linked that they are two parts of the same bigger thing.

換句話說，電場和磁場是緊密相連的，它們是同一個大事物的兩個部分。

Let's say we have a charge.

比方說，我們有一個電荷。

Since it doesn't move, it has a static electric field.

因為它不會移動，所以它有一個靜態電場。

If we accelerate the charge, there will be a magnetic field around it.

如果我們加速電荷，它周圍就會產生磁場。

That magnetic field interacts with the electric field, which again changes the magnetic field, and this is a sort of chain reaction that makes the electromagnetic field radiate outwards into space as an electromagnetic wave.

磁場與電場相互作用，再次改變磁場，這是一種連鎖反應，使電磁場以電磁波的形式向外輻射。

Depending on the frequency, the human eye can actually see this.

根據頻率的不同，人眼實際上可以看到這一點。

It's called light, but most of the spectrum is invisible to the human eye, and is used for things such as Bluetooth, wireless charging, and confusing human apes into thinking magic is real.

它被稱作光，但大部分光譜是人眼看不見的，用於藍牙、無線充電和迷惑人猿，讓它們以為魔法是真的。

Hey, can we go back to the water and look at those molecules?

嘿，我們能回到水裡看看那些分子嗎？

Yeah, those.

是啊，那些。

What are they made of?

它們是由什麼製成的？

The molecules are made of atoms.

分子由原子構成。

Atoms are made of a core and some electrons.

原子由原子核和一些電子組成。

The core is made of protons and neutrons, both of which are made of quarks.

核心由質子和中子組成，而質子和中子都由夸克組成。

They're strange yet charming from up top down to the bottom.

從上到下，它們奇特而迷人。

Oh yeah, there's some more stuff, like for example the overweight brothers of the electron.

對了，還有其他一些東西，比如電子超重兄弟。

All of this together makes up the standard model, which we believe to be the smallest things in the universe.

所有這些共同構成了標準模型，我們認為它是宇宙中最小的東西。

At least that's the excuse we have for not knowing what quarks are made of.

至少這是我們不知道夸克由什麼組成的藉口。

Fun fact!

有趣的事實

Depending on the number of protons in the core, you get different elements.

根據內核中質子的數量，可以得到不同的元素。

Depending on the number of neutrons in the core, you get different isotopes of the same element, most of which are a little overweight and very unstable, so they fall apart into smaller atoms.

根據內核中中子的數量，你會得到同一種元素的不同同位素，其中大多數都有點超重，而且非常不穩定，所以它們會分裂成更小的原子。

That releases ionizing radiation.

這會釋放電離輻射。

Not so fun fact, that stuff will kill you.

不那麼有趣的事實是，那東西會要了你的命。

If you have a large group of atoms, you can predict when half of those will have fallen apart.

如果你有一大群原子，你可以預測其中一半原子何時會解體。

That's the half-life.

這就是半衰期。

Depending on how unstable an isotope is, it will survive a certain amount of time.

根據同位素的不穩定程度，它可以存活一定的時間。

Some don't want to live, some really don't want to live, but some will live far longer than you probably will.

有些人不想活，有些人真的不想活，但有些人會比你活得更長。

Oh yeah, did I mention that light is like the fastest thing in the universe?

對了，我提到過光是宇宙中最快的東西嗎？

To be exact, 299,792,458 meters per second in a vacuum.

確切地說，是在真空中每秒 299,792,458 米。

That is pretty fast, said everyone.

大家都說，速度真快。

Also, light is a wave, said everyone.

大家還說，光是一種波。

Why?

為什麼？

If you shoot it through two teeny tiny slits, it creates a fancy pattern due to interference, which is just a wave thing.

如果把它射入兩個很小的縫隙，它就會因干涉而產生一種奇特的圖案，這只是一種波。

You see, when two waves cross, they can add up or cancel each other out.

你看，當兩個波交叉時，它們可以相加，也可以相互抵消。

These gaps are the spots where they cancel each other out.

這些間隙就是它們相互抵消的地方。

So in this case, light behaves like a wave.

是以，在這種情況下，光的行為就像波一樣。

Nah, screw that!

不，去他媽的！

Everything you know is wrong, said Albert Einstein, probably smoking crack after hearing about the photoelectric effect and discovering that light comes in tiny packets called photons.

愛因斯坦說："你所知道的一切都是錯的。"他可能是在聽到光電效應並發現光是由被稱為光子的小包組成後，吸食了快克。

I sure hope that doesn't unravel a whole new area of physics!

我當然希望這不會揭開物理學的一個全新領域！

Anyway, he said, as he continued to casually drop an absolute bomb on the entire field of physics with his theory of relativity.

總之，他一邊說，一邊繼續隨意地用他的相對論向整個物理學領域投下一枚絕對的炸彈。

He assumed the speed of light is constant because it arises from two other constants.

他假定光速是恆定的，因為它源於另外兩個常數。

He also assumed the laws of physics are the same for everyone, regardless if moving or at rest.

他還假定，無論運動還是靜止，物理定律對每個人都是一樣的。

Now think about it, if two people turn on a flashlight, but one person is standing still while the other person is on a moving train, wouldn't the person standing still see the other person's light as going faster than the speed of light?

現在想一想，如果兩個人打開手電筒，但其中一個人站在原地不動，而另一個人在行駛的火車上，那麼站在原地不動的人看到的另一個人的光速不是比光速還快嗎？

The reality is, no, it would be the same as their own flashlight.

實際情況是，不，這和他們自己的手電筒是一樣的。

That's impossible, except if time passes slower for that person from the perspective of this person.

這是不可能的，除非從這個人的角度來看，那個人的時間過得更慢。

In other words, if the speed of light is constant, time must be relative.