After three videos in a row about quantum field theory, we bring things a bit more down to earth by talking about the sizes of things. Mostly about particles and atoms; the sizes of people and planets will have to come later.
The Biggest Ideas in the Universe | 12. Scale
And here is the associated Q&A video:
The Biggest Ideas in the Universe | Q&A 12 - Scale
Hi Professor Carroll,
1. Another great episode (and cool background)! I’ve heard “Compton Wavelength” used but never understood it.
2. You mentioned “axions” briefly. Could you go more into depth at some point?
3. You also mentioned “proton decay” as a prediction/essential aspect of GUT? Why ?
3. Where would “magnetic monopoles” fit in to your scale story? I believe Dirac postulated that they should exist. Why would they be important?
Thanks for all your thoughtfulness.
1 Caliban = 10^36 eV. When do we use the Compton wavelength and when do we used the de Broglie wavelength?
Hi doctor Sean! Thanks a lot for the video! Please keep this level of complexity! =)
Here are some questions:
1. So, quark is fundamental?
Not related to the video:
I still dont understand the decayment of particles… if heavier particles decay rapidly, how we still have heavy particles?
Thanks!
Hi Sean
Is this series or your notes to become a book?
Definitely keeping my brain alive during my weeks of isolation.
Thank you
John Webb
In the scale from 10^(-3) eV to 10^(27) eV, where will photons be? Is it possible for tachyons or gravitons to be smaller than the Compton wavelength?
Why do protons and neutrons have a mass of about 1geV despite containing three quarks, which you placed at a point two orders of magnitude higher on the scale at around the mass of the Higgs boson?
I’ve been enjoying these videos from the beginning and although the maths is way beyond my level, I’m trying to follow the concepts. Thanks.
When talking about scales, I always got scale invariance in mind, a concept that is well known in hydrodynamics and in mathematical research on chaos and self-similarity. In particle and astrophysics one might imagine some thought experiments like these: What would a hydrogen atom look like if it had a muon circling around it? What would the universe look like if c was less by a factor of … you name it? Is there some research done in this area?
Is length (size) divided by mass considered a measurement of scale?
At the Planck scale this is ~ 10^-27 and at the universe (diameter/ordinary mass) ~ 10^-27.
For an electron the size scale (l/m) = Planck size scale times (l/m) *( Fine structure / Grav coupling constant)
For Higgs the size scale (l/m) = electron size scale (l/m) times Fine structure.
First off, thank you deeply for this video series. Hoping it goes on for many more months (years?). I’ve been a fan since your lecture on particles, fields and the future of physics at Fermilab. The phrase “It’s waves” still rings in my mind.
A small question on this video: so you say Earth is composed of more neutrons than protons. Why is this?
PS
I checked the masses of the quarks. Didn’t know the top quark was so much heavier than the others so the protons are really much more massive than their constituent quarks. I expect we’ll have to wait for the QCD video (if you plan to make one) for an explanation.
Sean
FYI, Chapter 1 of Scale by Geoffrey West (2017, Penguin) is titled “The Big Picture.”
One thing he points out is that scales are often not linear and may not even have a mathematical description. This is often true for size. One example is taking an adult medicine dose and trying to determine a child size dose by using proportions.
West notes it may be impossible to predict a past condition from the present unless one knows how to scale the relevant events. This is particularly true when properties of a system are emergent. Seems this could be applicable to various questions in physics.
I appreciate you going into more depth than is usually available to us non-academics.
I’m wondering where some really energetic things sit on the scale. Examples:
Hiroshima bomb
Hydrogen bomb
Energy output of the sun
Supernova
Gamma ray burst
Thanks
Ooops! I think you got something wrong in your video (at about 9 minutes).
The following relations should read correctly:
1 cm = 10^(-5).eV^(-1)
1 second = 10^(-15).ev^(-1)
You can check this easily by introducing the Planck energy =1.22×10^(28) eV. Then you get the Planck length and the Planck time.
Not sure if this is on topic but I am currently reading your book Something Deeply Hidden. I am not a physicist but I truly am puzzled by the description of a wave collapse. How is that not conditional set probability? It seems to me that the wave function describes 100% of the probability where a particle can be so 100%=(x*probability of at+x1*probability at x1+x2*probability at x2+x0*probability at x0….) When you measure a particle and place it at x0 through a measurement you get a set of 100%=(x*0+x1*0+x2*0+x0*100+x3*0…) basically so long as the set value is equivalent and the set variables remain viable solutions the probabilities within the set can change, By measuring you fix the position of the particle and that has a value of being there 100% while all the other positions it could have been now have a 0% chance of being the position.