Home » Open thread 4/10/23

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Open thread 4/10/23 — 28 Comments

  1. the energy and mass conversion ratio makes it nearly infinite for our purposes, unless we can get around it with an alcubierre drive, of course there are tachyons theoretically but they pose their own problems,

  2. Since you can’t just plug “infinity” into the Maxwell equations I’m not sure what “infinite” speed of light does. To actually answer this question well you have to do some careful math with the Maxwell equations and then see what happens to a whole bunch of other equations that govern gravity and the behavior of charged particles, for example.

    The video is just a bunch of hand-waving special relativity stuff about causality. I don’t think causality depends on a finite speed of light. Back when people thought it might be infinite I don’t think they had any trouble with causality, I’m not aware of anyone identifying some kind of problem and arguing that therefore there can’t be infinite speed, but I haven’t read every book and paper ever either.

    If you make the speed of light not infinite but lots bigger, I’m not sure what experimental consequences you’d get, since you’d be changing the sizes of atoms too. I didn’t see they discussed that in the video.

    The speed of light isn’t just “the speed of light”, it’s a property of space that comes in to a lot of things that don’t appear to be related to light at all, like the size of an atom.

  3. Shorter summary: the speed of light is a large constant because it is a constant, and large.

    This video is a monument to tautological reasoning. I’m not saying the speed of light isn’t what it says, just that the video doesn’t explain anything – just re-states it as a fact in various ways!

  4. “The speed of light isn’t just “the speed of light”, it’s a property of space that comes in to a lot of things that don’t appear to be related to light at all, like the size of an atom.”

    Yep. The video glosses over a very interesting fact: c is determined by epsilon0 and mu0. One can derive from Maxwell’s equations the standard wave equation [d2u/dt2 = v^2(del^2 u) ] where the speed of the wave is shown to be 1/SQRT(epsilon0*mu0). That’s how Maxwell showed light is a wave and *derived* c. The video does point out that the speed of any wave is given by the “viscous” nature of the medium. So, one can interpret epsilon0 and mu0 as defining the “viscosity” of spacetime.

    Now we can move on to less established ground and move to more speculation. Bringing GR into the picture, spacetime is now “deformed” by the presence of matter/energy. Going back to the standard wave equation and thinking of say, water. The speed of sound in water is determined by it’s viscosity. So why not spacetime? It also brings up the idea of spacetime “flowing” which would eliminate the need for dark matter/energy. An Italian group of theorists are working on this idea. Flowing how?? Well, to be consistent with the 2nd Law, spacetime flows to higher entropy. QM?? Who knows!!?? Fun stuff!!

  5. i imagine light slows down, say in the gravity well of a black hole, but speeds up, unpossible,

  6. That’s an idea I’d never known of: the dependence of atom size upon c. But then also c is not the independent value that I thought it was, if it’s essentially a function of the permittivity and permeability. Why does atomic size (I take it we’re talking about radius here) vary with those, then? Unless not directly connected to c, perhaps, but rather to the strength of EM fields at atomic scale.

  7. @Phillip Sells:Why does atomic size (I take it we’re talking about radius here) vary with those, then?

    Electrons are bound to atoms by electric fields. The positively-charged nucleus attracts the negatively-charged electrons. Furthermore the electrons repel each other through being negatively charged.

    So yeah, the size of atoms depends on that.

    Unless not directly connected to c

    It’s all the same thing. Light is what you get when you wiggle charged particles, and you get that because you created changing electric fields which create changing magnetic fields which create changing electric fields and so on forever, the disturbances moving through space at speed c.

    Calling it “connected to c” or calling it “connected to the strength of EM fields” is just how you label it, or how you define the units. There’s no way to separate c from the strength of electric and magnetic fields.

    c is not the independent value that I thought it was, if it’s essentially a function of the permittivity and permeability

    It’s up to you how to write it. You can nail down c and one of the other two and derive the third if you wish. Some people do. Some people redefine their units to eliminate one of the three. But however you do it you are describing a property of space from which light and the sizes of atoms follow.

  8. This physics guy seems to be positioning himself as a male version of Dr. Sabine Hossenfelder. He’s got a ways to go. She does pretty damn good (especially for not being a native English speaker) at explaining abstract theoretical concepts!

  9. I’m not going faster than light, but I will be gone over the summer.
    AesopSpouse and I will be docents for one of our Church Historic Sites in Wyoming.
    https://www.churchofjesuschrist.org/learn/historic-sites/wyoming/martins-cove?lang=eng

    Packing the car today and leaving on Wednesday.
    I’ll try to check in occasionally, but probably won’t happen more than once a week, and I certainly won’t be reading everything as is my usual practice.
    If World War 3 starts, I suppose someone will let us know.

    We expect to be home by Halloween (seems appropriate somehow), but if you don’t hear from me after that, so long, and thanks for all the fish!

    Douglas Adams aside, I appreciate Neo and everyone at the Salon. The news and reflections thereon from so many viewpoints are very educational, and we also have ballet discourses, French lessons, and recipes for Jell-o!

    https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fmissashleypants.com%2Fwp-content%2Fuploads%2F2014%2F08%2Fthanksforallthefish.gif&f=1&nofb=1&ipt=30160ec591f52b3ace4b39a2218994064b501c6dd661a36dfa0bed237caf7d03&ipo=images

  10. I did not have the patience to listen to the whole video. I bet the presenter did not get around to the anthropic principle. This is the principle that if the physical constants were substantially different then human life could not exist. This drives atheist physicists bonkers so they’ve come up with ridiculous ideas like the multi-verse where there’s an infinite number of universes, with different physical constants. They then say that we happen to live in one where life is possible. A little problem with that is there’s absolutely no evidence for this other than Atheist angst. The obvious answer to the question in the video is that the values of the constants were set by God to make life possible.

  11. well that may be true, multiverse, is a theoretical concept based on infinite choices,

    but are there examples where c is faster than standard, this is the classic counting angels on a pin,

  12. Happy trails, AesopFan. Looks like a place with plenty of peace and quiet once the tours are done for the day. Your voice will missed. Temporarily.

  13. Aesop Fan:

    Pack some warm clothes, Wyoming in the spring can have cold blustery weather; Sweetwater River, Granite Mountains, Wind River Mountains, Pronghorn antelope, and Sage grouse are calling you.

    Happy trails!

  14. I envy you and your husband, AesopFan. I look forward to any stories you are able to share. Happy trails until we see you here again.

  15. AesopFan:

    Best! Have a great time.

    Yesterday I was listening to a James Fadiman interview on YouTube. He’s an early psychedelic researcher, one of Ram Dass’s students back at Harvard. And I thought of you.

    Fadiman said that psychologists have learned that if you are researching mind drugs and you need a group of subjects who have not used drugs before, you send a bus to Salt Lake City.

    Well, I made up the last part.

    But I mean to say, psychologists know that Latter Day Saints (he was careful not to say Mormons) can provide a rich pool of candidates.

  16. I’m fond of the theory that the constant speed of limit is a hack put in when the Cosmic Programmers simulated our Universe, so as to reduce the computational complexity and storage requirements.

    Think about how much computer speed, memory and hard disk you need to keep track of the Universe! Then there’s the programming…

    If the hardware don’t get you, then the software will.

  17. It wasn’t Schrodinger who worked out the quantum properties of light, that was Dirac, The quantum theory of the emission and absorption of radiation. There were tricky new things to handle, for instance, the creation and destruction of photons (emission and absorption). That in itself is a pretty revolutionary take on particles, but his theory also allowed the calculation of emission probabilities and other such essential things. He followed that up with the equation of the electron, which again had to deal with the fact that the number of particles (electrons) was not fixed, they could be created and destroyed. It is hard to understand how revolutionary all that was.

  18. Aesop Fan,
    Clear skies and smooth landings!
    Your daily contributions to this blog will be missed.

  19. @ huxley > “If the hardware don’t get you, then the software will.”

    Reminds me of my favorite joke when I was programming:
    “The software is what makes the hardware do what the salesman sold.”

    Best wishes for a joyful spring & summer to everyone.

  20. so like deep think is hitchhiker’s guide, no these constants are there for a reason, like those solid yellow lines in the highway, the answer is not 42

  21. Best book on relativity I’ve read is Why Does E=mc2? By Brian Cox and Jeff Forshaw.

    Using simple algebra they clearly explain why Einstein was right. So yes there is math but it’s easy math.

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