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Originally Posted by OngBonga
GR seems to be an incredibly accurate approximation. Only when we get to the Planck scale does this accuracy break down. It of course doesn't mean GR is wrong, just that it is yet to incorporate QM.
Remember that QM is as accurate (more in some aspects) as GR.
Originally Posted by OngBonga
But there must be a way for GR and QM to unite. The universe is proof of that.
This is now my favorite quote.
Originally Posted by OngBonga
Maybe, though it seems the necessary measurement accuracy is ridiculous and well beyond what we can hope for any time soon, if ever.
Gravity waves propagate at the speed of light. That kinda implies that these waves behave similar to light. Gravity waves are a form of energy, just like light, and so maybe they're the same thing at the fundamental level. Maybe gravity waves are photons. If so, then gravity waves aren't helping us any more than light.
According to QM, if gravity has a quantum particle, a graviton, it wont be a photon.
Photons are spin-1 and gravitons (though not yet observed) are spin-2.
I believe if anyone can perform a repeatable experiment in which it is shown that a massless particle of spin-2 exists, that will earn them a Nobel for the discovery of the graviton.
Originally Posted by OngBonga
We've talked about this before. I'm unconvinced any such merger actually happens.
My bad. I was talking about the distance between the event horizons the moment before they combine into a single event horizon. Though, now that I say it that way, I suspect we have the same problem with the extreme curvature of spacetime making the notion of distance meaningless.
Originally Posted by OngBonga
Ok, I don't get any of this to be honest. I don't understand why there's debate about which of these values is "right". The Planck constant is derived from the relationship between photons and energy. The Planck length is derived from this constant. idk why there would be two possible values. But the Planck constant is... constant.
That relationship is E = hf, where E is the energy of a photon, h is Planck's Constant, and f is the frequency of the photon.
So if we're using that equation as the origin of h, then we should not use the reduced constant, h_bar, in calculating the Planck Length, and yet... we find that when anyone talks about the Planck Length, they've used h_bar in the calculation, and not h.
Why?
Because h_bar seems to capture something about angular momentum in it. The units are the same, but it comes up with the reduced constant in many QM equations, like Schroedinger's Equation. And that seems relevant.
And when picking which constants are "fundamental" ... that's a human game. The universe has these constants. They are inter-related. There are way more of them than are strictly needed, in a mathematical sense, to define everything. Mathematically, these constants are not all independent. So we can play a game in which we determine the minimum number of constants such that they are all independent, yet form a complete set by which ANY constant could be calculated.
Like in SI. We consider the fundamental constants to be meter, second, kilogram, Ampere, Kelvin, mole, and (totally unnecessarily, as it is redundant, dependent on other constants already) candela. Candela is even dumber than the Planck Length, so don't get me started. Candela is so dumb, even spellcheck rejects it.
So in SI, the "Planck" length is 1 meter. The "Planck" energy is 1 kg m^2/s^2 = 1 J. OK, so what am I getting at? Maybe it's more clear to look at electric charge. The "Planck" charge is 1 As (amp-second), which is 1 Coulomb, or 1.6(10)^19 times the charge of a proton. What is the significance of this charge? History, really. Our ability to measure currents, kinda... when the definition of an Ampere and a Coulomb were invented.
So the mathematical method of deriving "Planck" units is just a game to be played.
Playing the game with base units of c, the fine structure constant, h or h_bar, the charge of a proton, the Boltzmann constant, etc.. when you do that, we expect some cool surprises. Like to find meaning in the Planck Length, because the units we've chosen as fundamental aren't tied to humans aside from our ability to accurately measure them.
BUT, the meaning in those things is not guaranteed. And just because we can juggle some measurable numbers to come up with a length unit doesn't mean the magnitude of that length unit is relevant to the universe as a limit.
As Matt said in the video, it's not *at* the Planck Length that the QM weirdness suddenly happens. The quantum wierdness happens when the certainty in a finite volume containing a particle over-constrains a volume to the point that the number of particles in the volume becomes uncertain happens "near" the Planck Length, but its exact volume varies for each particle.
So the exact value of the Planck Length may not be meaningful, even if there is a meaningful something going on near that length scale. The juggling of numbers to derive the Planck Length is not based on physics, but math. The numbers being juggled are based on physics, but the way they're being juggled is not.
Originally Posted by OngBonga
I really like Steve Mould. He has the glazed look of a man that has enjoyed his life.
Veritasium, on the other hand, is clean as a whistle.
LOLOL.
I know exactly what you mean.
BTW, the wind car on Veritassium stirred up a whole lot of controversy in the physics world, with qualified doctorates in physics betting thousands of dollars against each other that the other was wrong. Apparently, Derek from Veritassium is about to receive a $10k payout from Alex Kusenko.
https://docs.google.com/presentation...0eb9892c_0_180
The green pages are Kusenko's critique of the claim in the Veritassium video. The white pages are the rebuttal to the critique.
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