Why is matter solid, if it’s made out of quantum waves? The answer is revealed in this action-packed episode. It involves Fermi statistics, the Pauli Exclusion Principle, and the spin-statistics connection. All illustrated with delightful visual aids.
The Biggest Ideas in the Universe | 17. Matter
And here is the Q&A video. Among other things, we talk about what “matter” means to a cosmologist.
The Biggest Ideas in the Universe | Q&A 17 - Matter
Bosons can have mass, even though they’re not matter (which is strange in itself). So how do we know dark matter is matter – i.e., fermions, and not massive stable bosons hanging out in empty space. That would make it dark forces, I suppose. Dark Side of the Force?
(How much) is it incorrect to think that atoms do not overlap mainly because of standard Electromagnetism? I mean: if we imagine the atom to have an “external shell” made by the wave(s) of the electron(s), these are negatively charged and thus would repel each other by standard EM. Is the Fermi pressure mentioned in the video somehow related to that fact or it’s a genuinely new force/concept?
Hi doctor Sean! As always, your video was amazing! It’s awesome to watch you explain, to see a teacher that really loves his work! It’s sad to think that one day this series will come to an end. I hope it doesn’t hehehehe!
Anyway, no doubts this time, at last not in the subject of the video, hahahahaha!
When you said about the universe making sense, I remembered Teilhard de Chardin and his notion of the Omega point. That’s my best guess about the meaning of the universe, and surely your videos send us to a better universe.
Anyways, I just wanted to thank you! =)
Another wonderful video. The visuals were great fun: the brick wall, the coffee cup rotation (such flexibility!) and the ribbon.
Could you talk about ANYONS (I only capitalize for ease of use, because you must scroll though many, many emails).
My understanding (slim) is that they are “in between” fermions and bosons in terms of rotation. They also trace out world lines in interesting ways (“braiding”).
Lastly, there has been a recent experiment in Italy XENON (I think you tweeted about it) which is suggestive.
So much enjoy your talks.
Hi. Thank you again for your great videos. Could you explain how conservation of angular momentum works with spin. Specifically, for spin 1/2, if you measure along x you always get non-zero. When you switch to y later in the path you always get non-zero. Does a measurement causing a change of axis by its nature apply a torque? How does this work? Thanks
Why is spin discrete? You’ve made the point previously that quantum mechanics is largely about continuous objects, which take on discrete values due to boundary conditions. Is that the case with spin as well or is there something fundamentally discrete about it?
Regarding how a wave function can satisfy the Interchange requirements, you mention two possibilities:
1) Int Psi = Psi (bosons)
2) Int Psi =-Psi (fermions)
But wouldn’t
3) Int Psi = complex conjugate of Psi
work as well. Could such particles exist too?
So Pi1(SO(3))=Z2.. That one confused me a bit. Maybe you could elaborate on that, and how it relates to actual rotations? And also how it relates to SU(2) being a double cover of SO(3)?
Thanks!
A recent paper on quark-matter cores in neutron stars: http://dx.doi.org/10.1038/s41567-020-0914-9
I always wondered why there was so much space in a unit cell of any metal. Thank you for that. My question relates to heat conduction and electrical conduction. I have read that there is an electron soup, but that doesn’t sound realistic. It even sounds less realistic when you discuss the electron as waves within. It appears that it needs to be the wave of untethered electrons. How does that work? My looking though the internet does not help.