The Very-Many-Questions-Not-Worth-Their-Own-Thread Thread XLIII

are there any good modern comics (preferably in English) similar in their layout and narrative style to the bande desinee Tintin and Asterix? Most comics I see nowadays have this disorienting style of different-sized panels, panels-within-panels and lengthy dialogues within the same panel
 
Have I got this right?
  • Fermions have spin 1/2, so matter cannot all be in the same place and we cannot walk through walls
  • Photons have spin 1, so like electrical charges repel and opposites attract
  • Gravitons have spin 2, so like matter attracts gravitationally, like being like all matter we have found
The later two are from the below youtube from Sabine Hossenfelder, and she references the Feynman lectures.

Spoiler 10 Physics Myths You Probably Believe - This is 2 at 8:34 :
 
Fermions have spin 1/2, so matter cannot all be in the same place and we cannot walk through walls
Correct. This is the Pauli exclusion principle, which says that for fermions only 2*spin +1 (= number of spin states (all these states are quantum states) = number of different internal states) particles can be in any external state (given by momentum, place in space).

Photons have spin 1, so like electrical charges repel and opposites attract
Gravitons have spin 2, so like matter attracts gravitationally, like being like all matter we have found
These are not at all comparable to the previous statement. The analog for the statement about fermions is that bosons prefer to be in the same state. For low energies this leads to Bose-Einstein condensation.

In my opinion the easiest explanation of the different particles' spin are the following:

The photon having spin 1 is analogous to saying that an interaction with one photon changes the spin by 1 unit, or that it is a dipole interaction. (second order multipole expansion. The first order is a monopole which is equivalent to a charge. Since the photon is to leading order a dipole it can not carry electric charge.) The electromagnetic interaction being a dipole interaction to first order can be shown in classical electrodynamics.

Aside - the multipole expansion may be most familiar to you from electrodynamics or especially different radio modes (the simplest radio receiver is only sensitive to dipole fields and is thus frequently called a "dipole"). It is basically a decomposition into spherical harmonics.

Typically gravitons having spin 2 is stated as a consequence of the waves in linearized gravity (approximately the gravitational waves we measure today. Also linearized, because that makes the equations much simpler and the theory of general relativity in its least approximate form is extremely complicated.) being quadrupole waves to leading order (third order multipole expansion), as this is an easier calculation. A quadrupole interaction changes the spin by 2 units. This is analogous to an interaction with two photons.

Now, about being a repelling or attracting force:

she references the Feynman lectures.
... and a quick look into the "Feynman Lectures on Gravitation" (on archive.org) reveals that this is in fact only a statement in this book and not a calculation. Take a look on page 30. Maybe there is something else, and maybe I will look further.

Assuming these statements to be true, I would change your statements 2 and 3 to the following:
  • Since in electromagnetism like charges repel, the associated mediator particle needs to have odd spin.
  • Since in gravitation like charges attract, the associated mediator particle needs to have even spin.
Note that this does not fix the spin. I made this change to better represent the direction of the reasoning: We start with an interaction with a known property (like charges attract/repel) and want to deduce the properties of an associated quantum theory (spin of the mediator particle).

Lastly, let me state that the existence (and properties) of the graviton as a particle relies on it being possible to formulate Gravity as a quantum theory, which has not yet been done and has proven to be a physically difficult problem.

Tl;dr:
Yes to all three, but 1 is completely different from 2 and 3.
 
Why do intelligent people say things like the pH scale ranges from value of 0 to 14? It is wrong and would appear to be likely to confuse people about how both pH and logarithms work?

pH well over 14 is most commonly in our everyday lives, and caustic soda usually comes as a 50% solution, and from the below calculations that is pH 15.1. It is important people understand what an "extreme" chemical that is. The lowest pH I can find referenced is runoff water from the Richmond metal sulfide mine at Iron Mountain, California has a pH of -3.6, which is nice but we should be being taught about these things to understand what we are doing to our planet.

Making people think about log of zero as some "barrier" like zero in the counting numbers or something is just wrong. It is more like one or equivalence than zero.

If you need an example of "smart" people saying this this is from the other place, and they are not supposed to be stupid and the rest of the document is quite good. Here is a place that says it and has the data and calculations I use to prove it wrong.

Spoiler Calculations :
Molecular Weight NaOH = 40 (39.997) g/mol
It is generally used as a solid or a 50% solution (equal weight of water and NaOH?)

1 litre has 500g NaOH = 500/40 = 12.5 = 12.5M

pOH = -log[OH-]
log(500/40,base=10) = 1.09691
pOH = -1.09691
pH + pOH = 14
pH = 14 - pOH
pH = 14 - -1.09691
pH = 15.09691
 
Most people don't care about details unless they are personally important. In addition, science and math are outside of most people's lives except as 'less interesting" parts of larger contexts. The pH of soda? Who cares. My flight seat assignment? Super important.
 
Most people don't care about details unless they are personally important. In addition, science and math are outside of most people's lives except as 'less interesting" parts of larger contexts. The pH of soda? Who cares. My flight seat assignment? Super important.
I agree most people, but I am quoting the Chemistry Dept. of Oxford University and a media company that is "
where inquiring minds come to learn about the natural world in all its complexity". Surely they care? Why do they choose to present these somewhat artificial points? pH 14 at least means something, the optimal buffering point of water if we were using that as the acid? pH of zero means nothing in the real world as far as I can figure out, it would be different if we had a different number of fingers.

The last couple of points I would love to be corrected on by someone who understands.
Spoiler My understanding :
The pK of vinegar is ~10^-5. That is why this graph is flattest at pH of 5. The pK of water is 10^-14 so if you did this with pure water the flat bit would be at pH 14. There is no such physical experiment you could do to demonstrate pH = 0.

1753990948774.png


From here
 
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Why do intelligent people say things like the pH scale ranges from value of 0 to 14? It is wrong and would appear to be likely to confuse people about how both pH and logarithms work?
I wouldn't know from certain, but in NZ most people in high school experience the joys of titration (I was always so impatient!) and pH levels in chemistry class, and it is instilled in their head that pH only goes from 0 to 14 because they're not taught that there's more to it. Actually I did not know it went beyond, either.

They did, however, have to stress the fact that just because it's red doesn't signify acidity etc., but our constant use of universal indicator didn't help us very much.
 
I wasn't directly taught it, but the colour chart for the strips we used at school only went up to 14, so I long assumed that was as high as it could get.
 
Is the bodily action in this video (once the camera zooms out) also called "thrashing," (even though the dictionary definition says thrashing is uncontrolled and this is very controlled)?


In other words, are the two words essentially synonymous? Or is this "headbanging" specifically? Is thrashing something else that people do in connection with music? If so, could I get a video of what thrashing is?

Thank you, you youngsters who are in touch with this stuff.
 
Thanks, Chukchi.

So, if I understand it right, "thrash" is used mostly as an adjective, to distinguish one sub-genre of metal, and not much as a verb describing an action that a performer or audience member makes in reaction to the music.
 
The aggressive dancing that's done in heavy metal concerts that can include headbanging I've only ever heard it called "moshing" and where it's done a "mosh pit".
 
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