ALL OF PHYSICS explained in 14 Minutes — Transcript

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1. 0:00Hi!
2. 0:01You’re on a rock.
3. 0:02Floating in space.
4. 0:03Surrounded by more rocks.
5. 0:04And gas.
6. 0:05And a bunch of nothing, mainly.
7. 0:06Oh hey, look at that, the rocks are going around the gas.
8. 0:08Hold on, what the heck, is going on here?
9. 0:11To understand, let’s look a little bit of Physics.
10. 0:13Wait, did I say a little bit?
11. 0:17To find out what kind of magic this is, we’ll have to go back in time.
12. 0:20Okay, not that far.
13. 0:23Stop!
14. 0:24Yeah.
15. 0:25That’s perfect.
16. 0:26This is gravity guy.
17. 0:27But most people call him “Isaac Newton”.
18. 0:28One important thing he said is that Force equals mass times acceleration.
19. 0:31Now what do all these words even mean?
20. 0:33Force is just a push or pull on something, in a certain direction.
21. 0:36Mass tells you how much of something there is, and it’s also a measure of inertia,
22. 0:39but we’ll get to that later, and acceleration is the derivative of velocity with respect
23. 0:43to time, but that’s too many big words for my taste, so let’s just say it’s how fast
24. 0:47velocity is changing.
25. 0:48The key takeaway is that if you apply a Force to a fixed mass, you get a predictable amount
26. 0:52of acceleration.
27. 0:53If you know all the forces acting on a basketball mid-air, you can predict with 100% certainty
28. 0:57if the ball will go in the hoop or your neighbours windshield.
29. 1:01“Whoa, did an apple just fall on my head?”
30. 1:05Yes Newton, it did.
31. 1:07“That must have happened for a reason” said Newton, as he discovered that two masses
32. 1:10attract one another, making the apple fall.
33. 1:13Yes, even you, no matter how ugly you think you are, attract pretty much the whole universe,
34. 1:17at least a little bit.
35. 1:18Hey, can you put that on paper?
36. 1:19“yup” said Newton, who gave us the Law of Universal Gravitation.
37. 1:23In other words, how much two bodies pull on each other, given their mass and distance,
38. 1:26times a constant.
39. 1:27Bigger mass?
40. 1:28Bigger Pull.
41. 1:29Bigger distance?
42. 1:30Smaller pull.
43. 1:31Actually, a lot smaller pull.
44. 1:32You see, the as the distance increases, the Force gets smaller by the square.
45. 1:36That my friends, is the Inverse-Square Law.
46. 1:38Gravity is also the reason why the planets in our solar system orbit the sun.
47. 1:42They got their initial velocity when the solar system formed out of spinning gas, and since
48. 1:46there’s nothing in space to stop them from moving, they’ll keep moving.
49. 1:49Hey, that’s Newton’s first Law.
50. 1:51The sun is so massive, that the force of gravity keeps pulling the planets towards the sun,
51. 1:55but the planets are fast enough to essentially fall towards the sun but miss it, and this
52. 1:59goes on forever, creating a round orbit.
53. 2:01Actually, that’s kind of a lie.
54. 2:03Most orbits orbits are not perfectly round but more egg-shaped and pluto’s orbit is
55. 2:07just…a complete mess.
56. 2:08But you get the idea.
57. 2:09In this case, the gravity is what we call a centripetal force.
58. 2:13One thing many people confuse is mass and weight, and no, they are not the same.
59. 2:16Mass tells you how much of this blob there is, and Weight is the force of Gravity the
60. 2:20blob would feel.
61. 2:21To make things clear, your mass would be the same on the earth and on the moon, but the
62. 2:25“weight” you would perceive, is different, because the moon has a weaker gravitational
63. 2:28pull, meaning, a weaker force acting on your mass.
64. 2:31So really, you’re not overweight, you’re just on the wrong planet.
65. 2:34Aight, enough about Newton, let’s break some stuff.
66. 2:36If you ever dropped your phone, it might look like this: What the hell ground, why’d you
67. 2:40do that?
68. 2:41The answer is Energy.
69. 2:42You know, the thing kids have after eating gummy bears.
70. 2:45Energy has the unit Joule.
71. 2:46And it’s not like Force, it’s doesn’t have a direction, it’s just a number, that’s
72. 2:49kind of chilling there, as a property of a thing.
73. 2:51You see, there’s two main kinds of energy: Kinetic energy, and potential energy.
74. 2:55In plain English, energy of movement, and stored energy due to some circumstance.
75. 2:59For example, when you held your phone, it stored gravitational potential energy, due
76. 3:02to being held above the ground, at a certain height.
77. 3:05Once you dropped it, the potential energy was converted into kinetic energy, as the
78. 3:09phone fell.
79. 3:10Then it smashed into the ground, and the phone absorbed some of the energy making the screen
80. 3:13go boom.
81. 3:15Work is defined as Force applied over distance.
82. 3:17For example: If you lift an apple by 1 meter, you would
83. 3:19have done about 1 Joule of work.
84. 3:21This happened by converting chemical energy stored in your body to gravitational potential
85. 3:24energy stored in the apple.
86. 3:26As you may have noticed, Energy and Work have the same unit “Joule”.
87. 3:29So they must be the same thing?
88. 3:31Uhhh, No.
89. 3:33Energy is the total amount of work that a thing could possibly do.
90. 3:36Work is just the stuff that actually happened and required energy.
91. 3:38You know, force applied over a distance, which most often implies converting energy from
92. 3:39one form to another.
93. 3:40If you try to lift a weight that’s too heavy for you, you’d feel like that took a bunch
94. 3:42of work, right?
95. 3:43Well, yes, but your feelings are invalid in the face of Physics!
96. 3:47Mathematically, no work has been done!
97. 3:49Because, work is a force applied over a distance.
98. 3:51And since you didn’t move the weight at all, no distance means no work.
99. 3:55The key thing to remember about energy is that it cannot be created or destroyed, only
100. 3:59converted.
101. 4:00Aka, the conservation of energy.
102. 4:01Okay, but a car, that’s moving has kinetic energy.
103. 4:04When the car stops, assuming the car doesn’t smash into a wall, where does that energy
104. 4:09go?
105. 4:10When you apply the brakes, there’s friction between the brakes and the wheels, causing
106. 4:12the car to slow down, and creating heat as a byproduct.
107. 4:16That heat is then dissipated to the surrounding air.
108. 4:18And that makes the molecules in the air move faster.
109. 4:21And things that move have kinetic energy.
110. 4:23So ultimately, the kinetic energy is transferred from the car to the air.
111. 4:26With this knowledge, we can define that Temperature is just the average kinetic energy of atoms
112. 4:30in a system.
113. 4:31You see, all atoms, not just molecules in the air, wiggle.
114. 4:34Like this.
115. 4:35The faster they move, the hotter things get.
116. 4:37That is temperature.
117. 4:39All that talk about hot stuff, I think it’s time we talk about Thermodynamics.
118. 4:42It tells us that jumping in lava is probably a bad idea, but more importantly, the absolute
119. 4:47mess that is entropy.
120. 4:48Literally, it tells you how much disorder there is in a system, indicating the number
121. 4:52of possible states a system can be in.
122. 4:54For example, get an ice cube, no not that one, yes that’s perfect, and put it in the
123. 4:59sun.
124. 5:00The sun will obliterate the ice cube and turn it into water.
125. 5:03Looking at the structure of ice and water, we can see that ice is more neatly organized
126. 5:06than water, which just kind of goes all over the place.
127. 5:09Also, the water could look like this, or this, or even this, but the ice will always look
128. 5:13a little something like this.
129. 5:15In total, the system went from low entropy to high entropy, meaning more disorder and
130. 5:19more possible microstates.
131. 5:21This trend applies everything.
132. 5:22The whole universe is on an unstoppable path to higher entropy.
133. 5:25It’s also the reason why time seems to go only forwards, or at least, that’s what
134. 5:29we believe at this point.
135. 5:30Practically, entropy tells us that some forms of energy are more useful for doing work than
136. 5:33others.
137. 5:34Burn some gasoline, and your car will move, spitting out heat and gas.
138. 5:37That heat and gas is pretty much gasoline, just in the form of higher entropy.
139. 5:41And as you can imagine, this stuff won’t really make your car move, and the gas won’t
140. 5:44spontaneously turn back into liquid gasoline.
141. 5:46Meaning, the form of gasoline with lower entropy is more useful for doing work.
142. 5:51Okay, but if you put some water in the freezer, will it not decrease in entropy?
143. 5:55Yes, BUT the fridge is not an isolated system and will heat up the room more than it will
144. 6:00cool down the water, increasing the total entropy.
145. 6:02Wanna see some magic?
146. 6:04Woah, what just happened?
147. 6:06Some electrons apparently moved through some wires and let there be light.
148. 6:11What is going on here?
149. 6:13Objects have a fancy something called a charge.
150. 6:14It can be positive or negative.
151. 6:16Or, if you have the same amount of both, an object is neutral.
152. 6:19Electrons have a single negative charge.
153. 6:20The flow of electrons is called electric current.
154. 6:22To describe it, we use three parameters: Current, Voltage, and Resistance.
155. 6:26Current is the amount of electrons passing through a wire in a given amount of time,
156. 6:30Voltage is what pushes the electrons to move, but simply put, it’s a difference in electric
157. 6:34potential, so you can imagine it as a slope that goes from high potential to low potential,
158. 6:38where the flow of current goes downhill, and resistance is pretty self explanatory.
159. 6:42This is Coulomb’s Law.
160. 6:43Wait a minute, this is just Newton’s Law of Gravitation in disguise!
161. 6:47This tells us that electric charges attract each other in a similar way masses do.
162. 6:51Opposites want to cuddle, while like charges literally couldn’t think of a more disgusting
163. 6:54thing than to be with one another.
164. 6:56These four equations explain pretty much all of electromagnetism.
165. 6:59But don’t be scared just because they look scary!
166. 7:01I mean, yeah, they do, but it’s simpler than it seems at first.
167. 7:04The first one states that if there is an electric charge, there will be an Electric field, or
168. 7:07this big E, emerging form it.
169. 7:09Add another and you have an electrostatic field.
170. 7:12These lines tell us in which direction a charged particle would feel a force at any given point.
171. 7:16The second one tells us the same for magnetic fields, AND, even though electric charges
172. 7:20are cool and can be alone, magnetic poles, are not.
173. 7:23They’re very lonely.
174. 7:24There will always be a north pole together with a south pole, and a single pole can never
175. 7:28be alone.
176. 7:29Okay now here’s where things get kind of freaky.
177. 7:32You know how electric charges only act on other charges, and magnets only affect other
178. 7:35magnets?
179. 7:36Well that’s only true if they’re not moving.
180. 7:38The third and fourth maxwell equations tell us that a moving magnet creates an electric
181. 7:42field, and a moving charge or electric field creates a magnetic field.
182. 7:45One consequence of this is that current can seemingly come “out of nowhere” by moving
183. 7:49a magnet next to a conductor.
184. 7:51The moving magnet creates and electric field, which makes the electrons inside the conductors
185. 7:54go crazy.
186. 7:56That is called induction.
187. 7:57It’s the reason why your phone charges when you put in on the charging pad, even though
188. 7:58it is not directly connected to a cable.
189. 7:59In other words, electric and magnetic fields are so tightly linked that they are the two
190. 8:00parts of the same bigger thing.
191. 8:02Let’s say we have a charge.
192. 8:04Since it doesn’t move, it has a static electric field.
193. 8:06If we accelerate the charge, there will be a magnetic field around it.
194. 8:09That magnetic field interacts with the electric field, which again changes the magnetic field,
195. 8:13and this is a sort of chain reaction that makes the electromagnetic field radiate outwards
196. 8:17into space as an electromagnetic wave.
197. 8:19Depending on the frequency, the human eye can actually see this, it’s called light,
198. 8:23but most of the spectrum is invisible to the human eye and is used for things such as Bluetooth,
199. 8:27wireless charging and confusing human apes into thinking magic is real.
200. 8:31Hey, can we go back to the water and look at those molecules?
201. 8:33Yeah, those, what are they made of?
202. 8:35The molecules are made of Atoms.
203. 8:37Atoms are made of a core and some electrons.
204. 8:39The core is made of protons and neutrons, both of which are made of quarks.
205. 8:42They’re strange yet charming, from up top down to the bottom.
206. 8:46Oh yeah there’s some more stuff, like for example the overweight brothers of the electron.
207. 8:50All of this together makes up the standard model, which we believe to be the smallest
208. 8:54things in the universe.
209. 8:55At least that’s the excuse we have for not knowing what quarks are made of.
210. 8:58Fun Fact!
211. 8:59Depending on the number of protons in the core, you get different elements.
212. 9:02Depending on the number of Neutrons in the core, you get different Isotopes of the same
213. 9:05element.
214. 9:06Most of which are a little overweight and very unstable.
215. 9:08So they fall apart, into smaller atoms.
216. 9:11That releases ionizing radiation.
217. 9:13Not so fun fact: That stuff will kill you.
218. 9:15Do not play with radioactive atoms.
219. 9:16If you have a large group of atoms, you can predict when half of those will have fallen
220. 9:18apart.
221. 9:19That’s the halflife.
222. 9:20Depending on how unstable an isotope is, it will survive a certain amount of time.
223. 9:23Some don’t want to live, some really don’t want to live, but some will live far longer
224. 9:27than you probably will.
225. 9:28Oh yeah, did I mention that light is like the fastest thing in the universe?
226. 9:32To be exact, 299, 792, 458 meters per second in a vacuum.
227. 9:38“That is pretty fast” said everyone.
228. 9:41Also, “Light is a wave” said everyone.
229. 9:43Why?
230. 9:44If you shoot it through two teeny tiny slits it creates a fancy pattern due to interference,
231. 9:47which is just a wave thing.
232. 9:49You see, when two waves cross, they can add up, or cancel each other out.
233. 9:52These gaps, are the spots where they cancel each other out, so in this case, light behaves
234. 9:56like a wave.
235. 9:57“Nah, screw that, everything you know is wrong” said Albert Einstein, probably smoking
236. 10:02crack, after hearing about the photoelectric effect and discovering that light comes in
237. 10:05tiny packets called photons.
238. 10:07I sure hope that doesn’t unravel a whole new area of phyiscs, haha.
239. 10:11“Anyway” he said, as he continued to casually drop an absolute bomb on the entire field
240. 10:16of physics with his theory of relativity: He assumed the speed of light is constant
241. 10:20because it arises from two other constants.
242. 10:22He also assumed the laws of physics are the same for everyone, regardless if moving or
243. 10:26at rest.
244. 10:27Now think about it: If two people turn on a flashlight, but one person is standing still,
245. 10:30while the other person is on a moving train, wouldn’t the person standing still see the
246. 10:34other person’s light as going faster than the speed of light?
247. 10:37The reality is: NO!
248. 10:39It would be the same as their own flashlight.
249. 10:41That’s impossible, except if time passes slower for that person from the perspective
250. 10:44of this person.
251. 10:46In other words, if the speed of light is constant, time must be relative.
252. 10:49Also, gravity is not actually a Force, sorry Newton, but rather a consequence of masses
253. 10:53bending spacetime.
254. 10:55Einstein thought that the universe is a mesh of space and time, and anything with a mass
255. 10:58bends this fabric.
256. 11:00Also, all objects move freely on a straight line when moving through space.
257. 11:04Gravitation is simply the result of objects following these bent lines, which appear straight
258. 11:07to them.
259. 11:08If you have a hard time understanding this, you can imagine two people on earth, walking
260. 11:11in parallel, straight lines.
261. 11:12On a short distance, the straight lines will never meet.
262. 11:13Now imagine one standing on the east cost, and one the west coast of the US.
263. 11:16If they both walk north, eventually, they will meet at the north pole.
264. 11:20Because of the curvature of the earth, they ended up at the same point even though they
265. 11:23both walked “straight” relative to themselves.
266. 11:25“Oh yeah by the way Energy and mass are kind of the same thing” he added, which
267. 11:28explains why atom bombs are so frickin powerful.
268. 11:31According to this formula, even just tiny atoms can release a humongous amount of energy
269. 11:35by giving up just a fraction of their mass during fission.
270. 11:39What is Fission?
271. 11:40It’s the same thing Oppenheimer used to make this thing go boom.
272. 11:42You see, there’s two main ways to gain energy from changing nuclei: Fission and Fusion.
273. 11:46Fission aims to split the nucleus of an atom into two or more smaller nuclei, which is
274. 11:50most often achieved by blasting the core with neutrons.
275. 11:53Fusion is the opposite, where you combine two smaller nuclei to get one bigger one.
276. 11:57The energy came from something we call a “mass defect” where the resulting nucleus is lighter
277. 12:01than the starting nuclei.
278. 12:02This “missing” mass is what was converted to energy during Fusion.
279. 12:06Fission and Fusion are cool, but you have got to be careful or you might just blow up
280. 12:09the planet.
281. 12:10That totally didn’t almost happen before…multiple times.
282. 12:13Hey remember when Einstein said light is a particle?
283. 12:16He accidentally discovered a whole new field of physics which he though is just a giant
284. 12:20hoax: Quantum Mechanics.
285. 12:21This stuff is crazy.
286. 12:23Another german guy called Max Planck said “yes, Einstein, you’re right.
287. 12:26Light does come in tiny packets.
288. 12:27Actually, all energy comes in tiny packets”.
289. 12:30Or “Quanta”.
290. 12:31He is the daddy of Quantum Mechanics.
291. 12:32Wanna know where an electron is inside an atom?
292. 12:33It’s here!
293. 12:34And there!
294. 12:35And everywhere, at the same time, actually!
295. 12:36That’s a superposition.
296. 12:37It’s not in one state, it’s in multiple states at once - at least until you measure
297. 12:41it.
298. 12:42Then it chooses one cozy spot to be in.
299. 12:44Schrödinger gave us an equation that gives you a probabilistic model of where you can
300. 12:47find it if you were to measure.
301. 12:49You can imagine this as a cloud, and the denser it is, the more likely it is for an electron
302. 12:53to be there.
303. 12:54But still, where exactly it will end up once you measure it, is random.
304. 12:57Speaking of observing particles, they’re also super sensitive about their private data.
305. 13:01Look at these two images of a flying ball: in one, you can clearly see where the ball
306. 13:04is, but not in which direction it’s moving, and in the other you can see where it’s
307. 13:08moving and approximately how fast, but not where exactly it is at the moment.
308. 13:12That is essentially Heisenberg’s uncertainty principle: You can never know both the exact
309. 13:16position and the exact speed of a quantum particle at the same time.
310. 13:19Okay, let’s recap, a small thing can be a particle and a wave at the same time, and
311. 13:22when we try to look at them, weird stuff happens.
312. 13:24But you know what, it gets even weirder.
313. 13:27Think back to the double slit experiment: We know that a light beam acts as a bunch
314. 13:30of waves and we get interference.
315. 13:31But here’s the weird thing: Even if you send individual photons, after sending enough
316. 13:36of them and detecting where they end up, you get interference.
317. 13:38Like, how can that be?
318. 13:40What did a single particle interfere with?
319. 13:42Well, we think it interfered with itself, because it acted as a wave and went through
320. 13:45both slits at the same time.
321. 13:48That’s a superposition.
322. 13:49“Okay, well let’s just measure which slit it goes through”.
323. 13:51Uh, yeah, that’s not going to happen.
324. 13:53Once you start measuring which slit the photon goes through, it stops acting like a wave
325. 13:56and the interference pattern disappears, as every particle chooses just one of the slits
326. 14:00to go through.
327. 14:01Sounds kinda suspicious to me.
328. 14:03Anyways, all this knowledge is going to cost you one subscribe and a thumbs up, thank you
329. 14:07very much, and you can decide if maybe you’d want to tip with a comment, perhaps?