General Relativity doesn’t end just above the atmosphere and quantum mechanics ought to apply to everything, not just experiments.
The current microscopic models don’t even attempt to explain how a molecule of water is lighter than the oxygen and two hydrogen atoms that went into making it.
Oh sure, we can wave our hands at it and invoke the mass-energy relation from GR, but this doesn’t “pop out” of the Standard Model in any sense.
This isn’t some exotic phenomena only found in deep space!
We have a long way to go before we can par ourselves on the back and claim to truly understand what’s going on.
> General Relativity doesn’t end just above the atmosphere and quantum mechanics ought to apply to everything, not just experiments.
No one disagrees, but if it were that easy to just jump straight to the final theory we would have done it long ago. For now, effective theories are all we've got.
> Oh sure, we can wave our hands at it and invoke the mass-energy relation from GR, but this doesn’t “pop out” of the Standard Model in any sense.
Yes, it does. You don't need GR for mass-energy equivalence, just special relativity. And the Standard Model is fully special-relativistic.
> We have a long way to go before we can par ourselves on the back and claim to truly understand what’s going on.
This is a misconception of scientific endeavour in general and of physics in particular. All models are approximations of reality. We have a theory that is consistent with experimental observations, then we make observations with which the theory is not consistent anymore and we develop a new theory that explains those new observations as well, and so on. We will never have an "exact" model, whatever that even means. But we have models that have limitations that are far beyond what's relevant for most people's life.
At many points in time, we could pat ourselves on the back. The heliocentric model. Newtons model. General Relativity. The Standard Model. All these models were important steps forward and led us to where we are today, which is absolutely astonishing. No, we don't have a full theory explaining everything, but we never will.
> Oh sure, we can wave our hands at it and invoke the mass-energy relation from GR, but this doesn’t “pop out” of the Standard Model in any sense.
Mass-energy equivalence, a.k.a. E=mc^2, is special relativity. It's fundamentally linked with our understanding of electromagnetism. Physics students generally learn about special relativity before they get to quantum mechanics.
You appear to be confusing special relativity and general relativity. Mass-energy equivalence pops out of special relativity, and is part of general relativity because GR extends SR. Another class of theories which extend special relativity are (relativistic) quantum field theories. These also have mass-energy equivalence baked into them because they contain special relativity.
Your are correct that there is a (strong) conflict between general relativity and quantum field theory, and this is a major problem for theorists, but it does not pose problems for using mass-energy equivalence in quantum field theories (since it comes from SR not GR).
There are real, physical, examples where the GR/QFT conflict is more problematic. For example in quantum physics labs around the world it is possible to put things which have mass in superpositions of being in two different places. This is usually done with very small objects, but it happens. We have absolutely no idea what is happening to space-time when we do this.
Nothing says mass-energy equivalence cannot be applied to small particles. We have a good explanation of a very large set of physical phenomena. Yes, there are always things that are unknown and more you know, the more there is to know at the edges.
No one is claiming to "truly" understand anything and your cynicism is misplaced.
You mean experimental evidence? I don't think our mass measurements are that precise.
Just to be clear, that statement is very well accepted physics, and we have plenty of evidence of bounding energy changing the mass of things on the more energetic reactions (the nuclear ones). It would be incredibly surprising (in "redo all of physics" surprising) if it didn't hold for chemical reactions too, but I don't think anybody has evidence.
You mean experimental evidence? I don't think our mass measurements are that precise.
You don't need to weigh individual atoms or molecules to take measurement!
Just to be clear, that statement is very well accepted physics, and we have plenty of evidence of bounding energy changing the mass of things on the more energetic reactions (the nuclear ones). It would be incredibly surprising (in "redo all of physics" surprising) if it didn't hold for chemical reactions too, but I don't think anybody has evidence.
Not sure I follow your direction here. Seems to be a conflation of three separate things, not necessarily compatible with each other. In classical physics mass and charge (of a particle) are different properties. One defines how particle behaves in response to forces, the other how it interacts with em fields. That's one. The other, if we go into relativistic physics, there's mass-energy equivalence (as stated by einstein)... however, charge itself isn't a form of energy, BUT charged particles can have energy associated with their electric fields that would contribute, in a sense, to the overall mass-energy of a system (which is usually ignored unless we're talking sub-atomic particles or high-energy physics). That's two. And then there's binding (not bounding) energy which represents the amount of energy required to split a system of particles into its non-interacting components (such as, in context of nuclear physics, splitting a nucleus into protons and neutrons).. or you've meant electron binding energy which represents amount of energy needed to remove an electron from an atom.. that'd be a third.
The mass ratios of charged particles, such as atomic and molecular ions, can be measured incredibly accurately in Penning traps. Some of the most accurate comparisons are between the mass-3 ions ³He⁺, HD⁺, T⁺, and H₃⁺. Of these, only H₃⁺ has long-lived excited states, and the different excitation energies are clearly resolved in the mass comparisons [1]. The binding energies are much larger and have to be taken into account in the comparisons.
> Can you point to some evidence for the claim that "a molecule of water is lighter than the oxygen and two hydrogen atoms that went into making it?
Not OP, but burning hydrogen in oxygen is exothermic. It makes intuitive sense that the energy from that reaction no longer contributes to the mass of its products.
"
The weight of a molecule of water (H2O) is the sum of the weights of the two hydrogen atoms and one oxygen atom that compose it. Here are the atomic weights of these elements:
Hydrogen (H): Approximately 1 atomic mass unit (amu)
Oxygen (O): Approximately 16 amu
So for a molecule of water:
2 Hydrogen atoms: 2 * 1 amu = 2 amu
1 Oxygen atom: 16 amu
Adding these together gives a total of 18 amu for a molecule of water.
This means that a molecule of water has the same weight as the sum of the weights of the two hydrogen atoms and one oxygen atom that compose it, because the molecule is simply a combination of these atoms. There's no loss or gain in weight when the atoms combine to form the molecule.
However, this does not take into account the minor decrease in mass that occurs during the formation of a water molecule due to the conversion of some mass into binding energy according to Einstein's equation E=mc^2. This decrease is incredibly small and generally not considered in standard atomic weight calculations, but it does technically make the water molecule ever so slightly lighter than the sum of its constituent atoms."
> the minor decrease in mass that occurs during the formation of a water molecule due to the conversion of some mass into binding energy according to Einstein's equation E=mc^2
Is highly imprecise at best, and misleading at worst.
It is true that the mass of the water molecule is slightly less than that of the oxygen and hydrogen atoms combined. It is not true that this excess mass is converted into "binding energy", binding energy is negative in stable molecules. That is the binding energy measures how much energy you would have to add to break up the molecule, or conversely, how much energy is lost (as heat/light/whatever) to the environment when the molecule is formed.
The mass is lower because it has been converted into heat in the environment, not because it has been converted into binding energy.
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I would call this an instance of the language model producing convincing sounding nonsense (something that they do quite often when asked about technical stuff).
Okay, somebody explain these downvotes, because afaik none of these statements in this comment or the other downvoted comments about the mass of water are incorrect. Somebody make it make sense.
I believe this one is downvoted for quoting Chat GPT. The other one is downvoted not so much for the claim about water molecule mass, but because of the combative tone and feeling that it is challenging established physics in a somewhat shallow way, most likely.
It cracks me up that my comment is seen as "challenging established physics" (and being downvoted into oblivion) when literally everything I stated is established physics.
I really don't see what's controversial about what I've said that's riled up people so much...
It is factually incorrect in the assertion that the standard model can't explain the reduction in mass (special relativity and quantum mechanics work fine together. It's general relativity that is the problem). In fact mass-energy equivalence is a pretty core part of quantum mechanics.
> In fact mass-energy equivalence is a pretty core part of quantum mechanics.
It may be stated as such, and added in to equations as an external piece of knowledge from relativity, but this is cheating a bit.
Essentially, when we state that H2O has less mass than H+H+O, what we actually mean is that H2O bends spacetime a little bit less than the three atoms individually that made it up. There's no accepted variant of QM or the Standard Model that explains this. The dynamics of spacetime curvature rearranging as the photon is emitted as the hydrogen atoms burn is not explained by modern science. This is fundamentally the "QM is incompatible with GR" issue.
My point was that it isn't just near black holes that a GR-compatible microscopic theory is relevant.
It's relevant even in the flame of a candle. It's a small effect, but it's there. The inconsistency in the theories occurs at all scales.
While you're right about the inconsistency between GR and QM applying at any level, you're wrong about needing GR to talk about the mass of the water molecule.
Even in pure QM, the water molecule will have less inertia than unbonded hydrogen and oxygen atoms. This should in principle be measurable by applying a known force to the water molecule and to the three atoms, and measuring their acceleration. The difference should perfectly match the inertial difference predicted by SR and GR.
GR adds the observation that, if the water molecule has less inertia, it should also bend space-time less, and it is this bending of space time that can't be explained by QM.
Though I should add that I've had a reply to a different comment once that explained that QM is actually compatible with the flat-ish but not perfectly flat space times that GR predicts anywhere not very close to a black hole. They were claiming that in fact modern QFTs can even predict things like the gravitational lensing produced by our sun, and that they only break down when near the event horizon of a black hole.
> Essentially, when we state that H2O has less mass than H+H+O, what we actually mean is that H2O bends spacetime a little bit less than the three atoms individually that made it up. There's no accepted variant of QM or the Standard Model that explains this.
I'm not sure this is correct. It bends spacetime less simply because it's in a lower energy state. It's correct to say that the Standard Model doesn't explain spacetime curvature, but the curvature in GR is implied by the energy which is explained.
The current microscopic models don’t even attempt to explain how a molecule of water is lighter than the oxygen and two hydrogen atoms that went into making it.
Oh sure, we can wave our hands at it and invoke the mass-energy relation from GR, but this doesn’t “pop out” of the Standard Model in any sense.
This isn’t some exotic phenomena only found in deep space!
We have a long way to go before we can par ourselves on the back and claim to truly understand what’s going on.