Quantum Mechanics - Part 2: Crash Course Physics #44

e=mc2... it's a big deal, right? But why? And what about this grumpy cat in a box and probability? In this episode of Crash Course Physics, Shini attempts to explain a little more on the topic of quantum mechanics.

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[crashcourse]

We made quiz questions to help you review the content in this episode! Find them on the free Crash Course App!

[Ermude]

For those curious about the Heisenberg's uncertainty principle, it's a direct consequence from Fourier transformation. As explained in the video, we need to think of the particle as waves (having momentum) or particles (having position). The Fourier transform let's you go between these different spaces (momentum space / position space) but it kind of "bundles up" a range of values into a single value when changing space, and that gives you the uncertainty.

For example, imagine a sinus wave, just a wavy rope going from the left to right. Now, rotate your viewing position to one end of the rope so that the wave travels straight from your position. From this point, it would look like a vertical line. So even if the wave was very irregular with different heights at different nodes, from this perspective, we would only see a single vertical line. We have thus "bundled up" a range of different values, and we can't be certain what the height of the rope would be at different positions, but we know it's within the range of our vertical line.

So the uncertainty principle is a purely mathematical restriction which was known long before quantum mechanics, but took a practical meaning after the discovery of quantum mechanics.

[semiawesomatic]

Heisenberg and Schrodinger are in a car together. Heisenberg is driving. A cop pulls them over. the cop asks "Do you know how fast you were going?" to which Heisenberg responds "No, but i know exactly where i am." The cop now confused, asks the two men to step out of the car. He then walks to the back of the vehicle and opens the trunk. Startled he shouts "Holy s***! You guys know you have a dead hooker back here right?!?" Schrodinger yells back "THERE IS NOW!"

[chandinimohan]

with 50 minutes with crash course my whole physics class was completed in a semester

[chowtom]

"Mr Heisenberg do you have any idea how fast you're going?!"
"No officer but I know exactly where I am."

[SOLACEISHERE]

god this is the smartest comment section on youtube I've ever seen

[kevinfoss]

I am currently 12 and I am watching these videos, I am going to keep practicing and learning physics until high school and I am going to try to get a PhD in experimental physics and mechanical engineering
Wish me luck

[alancotter]

Feel like I'm getting a Masters with these videos

[scottfranco]

We should really find out what, exactly, theoretical physicists have against cats...

[timothymclean]

Quantum mechanics: The biggest example of how our common sense has no place in scientific discourse.

[Kumar-oejm]

At 1:38, it should have been interference pattern instead. A diffraction pattern is obtained when a single slit is used. Not that diffraction doesn't occur for a double slit when its used, its just that the double slit is used to obtain an interference pattern instead.

[henriklarsen]

Best explanation of the Uncertainty Principle I ever saw. Thank you!

[Nitroxien]

Can we have a crash course biochemistry please!

[islacasey]

"But that's quantum mechanics for you".


Me trying to study for my modern physics exam:



*sniffle* yeah :, (

[PinkChucky]

I love the weirdness of Quantum Mechanics :-)

[anjulichaudhary]

Shrodinger married twice, was busy with his own double slit experiments.

[FewMinuteProgramming]

Why was Heisenberg's wife unhappy?

Whenever he had the energy, he didn't have the time.

Like if you get the joke :)

[jamescarmody]

Heisenberg's uncertainty principle makes intuitive sense to me. When something moves a lot, you're less certain about where it is at any point in time--it could accelerate, friction might apply, the thing might slow. But if it isn't moving too much, then you can tell where it is more accurately. Now, though, its speed is hard to measure; if it's slow enough, you might not measure movement at all!

For super small particles, like on the quantum level, this uncertainty is so pronounced that you can't _ever_ know position and momentum.

[sparklingstarsforeverinthe]

At 0:57 ( pause the video) it says that something will happen in 2020 I don’t understand, this was posted 2 years ago so umm and on top of that it’s now 2020 🤔

[UteChewb]

I'm dreading the last episode of this series. It must be getting very close now. Excellent work, CC and Shani. Personally I would have preferred more equations (dodges rotten tomatoes) but still excellent.