Understanding Quantum Mechanics #6: It's not just a theory for small things

In this video I explain that quantum mechanics is not merely a theory for short distances, as it is often portrayed. Quantum mechanics applies to all objects, regardless of size. Indeed, quantum effects are necessary to explain many rather mundane observations: the sun shines, atoms are stable, laser light is strongly focused and coherent.

Correction: The map at 5 mins 13 secs does not show the islands of Tenerife and La Palma but, mistakenly, the islands of Tenerife and Gran Canaria (the captial of which is Las Palmas). Lots of palms there, I figure. ht Jose de la Puente for pointing out.

Note: The animation at 1 mins 31 secs does not show what really happens if an electron hits an atomic nucleus. It merely illustrates "this is not how atoms work". If an electron hits an atomic nucleus, there constituents of the nucleus most definitely do not fly off in all directions!

The paper I mention about superpositions of large molecules is this:

And the one about Bose Einstein Condensates is this

The previous videos in the series "Understanding Quantum Mechanics" are:

Content of this video:

0:00 What and Why
0:36 Nuclear Fusion in the Sun
0:55 Stability of Atoms and Solar System
3:50 Lasers
4:50 Entanglement on the Canary Islands
6:15 Big Molecules and Bose Einstein Condensates
7:14 Brilliant Sponsor Message

[cipaisone]

depite being not a physicst, it was always clear to me that quantum mechanics could not be a serious theory if its application was only valid for "small" objects.
it is umbelivable that so many physicists on youtube describe QM as the theory of the small objects.
thanks for making it clear.

[alisaiterkan]

This is freaky. İt's almost as though she knows what i am wondering about and then provides a video to answer all questions İ can't lookup due to the technical depths into which I can't venture. And every single explanation is understandable yet not watered down. Science communication at its best.

[jlpsinde]

I'm a physics teacher and this video is just amazing really incredible.

[parasuramvenkatesh]

"Why don't planets fall into the sun?"
"They *do*!"
bruh that got dark for a sec there

[wesbaumguardner]

"Men substitute words for reality and then talk about the words." Edwin Armstrong.

[pabloemiliorui]

The Steel Man argument: she makes the opposing case as strong as she can and still refutes it. Evidence of a solid argument.

[wholenutsanddonuts]

Don’t forget that we can see through our transparent corneas due to quantum mechanics, and that photosynthesis (the very basis of life) depends on quantum effects. These are pretty macro bits of life too. :)

[cristianchisbora]

You are one of a kind, Sabine, so few scientists know to communicate in such an accesible and logic manner!

[ashirahelat]

I am addicted to your talks and I love your sense ofhumor

[XylyXylyX]

My favorite quantum effect that has major macroscopic consequences: The Pauli Exclusion Principle. This effect is what makes chemistry possible and the entire world as we experience would just be a blob of uninteresting atomic matter without it. Sabine discussed the stability of atoms, which is closely related to this, but I think arguably different. The fact that QM tells us that the ground state has a finite energy is, arguably, why atoms are stable. The Pauli Exclusion Principle is why electrons must stack themselves in a complex way around the nucleus giving us all of chemistry!

[astronomiskungdom]

At 5:10, the animation shows the islands Tenerife and Gran Canaria (with it's largest town, Las Palmas), not the islands Tenerife and La Palma. It's a common mix up/confusion...

[antoniomaglione]

Hello Ms. Hossenfelder,
There is no Nobel prize for explaining well (well=coherently) the quantum mechanics; in the case, you would be the clear winner!
I recall, decades ago, when I expunged the quantum theory by myself. Of little help was my knowledge of calculus. The book which taught of wavefunction had more symbols and formulas than written text. Two years passed before I grasped the base concepts; this was because all books explained (mathematically) how to operate with those concepts, not what they meant.
More than thirty years later, there is Internet, then you.
This short video is the best logically chained explanation of what quantum mechanics is, so have my compliments for that. If I may suggest, the part that follows immediately after "why the electron doesn't emit RF radiation and falls into the nucleus" could benefit from introducing the concept of "behaviour vs. appearance" intrinsic to quantum mechanics.
Thank you.

[patricialauriello]

Doctor you have solid arguments. Thank you for making it clear. Glad you calmed down since the last video. You were gluing people to buses.

[Earwaxfire]

Sabine, I wish I had a teacher like you when I was introduced to quantum mechanics! What text books would you recommend we read to learn more? Also, I would like to mention super-fluidity, superconductivity, Wannier periodic crystal potentials, and the Hall effect among others which are macroscopic quantum phenomenon. And of course Black holes too...

[gashery]

Another exceptionally clear science communication. Such a fresh wind in a field of science usually entangled in mysticism and general drivel. Thank you 👍

[TheVincent]

I like the example that is given in the book QED by Richard Feynman where he explains the partial reflection of glass. Every time I look at a window at night I remember that example.

[CUDAbuster]

I am glad to discover these videos. Well prepared, illustrated and explained. The lecturer is engaging. Reenergizing my interest in physics after several years of no longer needing to study the subject matter, it is interesting to revisit it from a non-academic perspective.

[seanspartan]

I try to keep my wave function as non-localized as possible to keep the people around me guessing. I like to keep friends and family on their toes 🙃

[lezhilo]

I think superconductivity would've been a nice example of macroscopic quantum effects for this video. Particularly quantum levitation which if I remember correctly, relies on the quantization of magnetic flux, can be demonstrated on a macroscopic length scale, and definitely looks super weird.

[matoatlantis]

Thank you! I was wondering if somebody did the experiment similar to one on Canary Islands. I can imagine myself being there super excited seeing that experiment live.
Your videos are one of those that keep my interest into this topic.