If the forces are unified then it must, mustn't it?
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5$\begingroup$ That's not how unification works. If you really wanted to ask "What do physicists mean why they "unify" forces?", please do ask that explicitly (after searching for duplicates and exhibiting some amount of search effort on the term in general) - it's a much better question. $\endgroup$– ACuriousMind ♦Commented Jan 4, 2019 at 23:15
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$\begingroup$ That isn't what I wanted to ask, and that is how unification works, showing that two things which you had previously believed were not the same thing are the same thing is a unification. I maybe shouldn't even be posting this here but in some philosophy forum because this argument, when it comes to grand unification and quantum gravity is all semantics. $\endgroup$– Sam CottleCommented Jan 4, 2019 at 23:20
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$\begingroup$ @SamCottle if you ascribe to such a viewpoint, then shouldn't your question be "Does the unified force hold electrons in orbit around atomic nuclei"? $\endgroup$– enumarisCommented Jan 4, 2019 at 23:26
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$\begingroup$ No, because it's a semantic argument. $\endgroup$– Sam CottleCommented Jan 4, 2019 at 23:30
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3$\begingroup$ I'm voting to close this question as off-topic because of lack of elementary due diligence. $\endgroup$– ZeroTheHeroCommented Jan 5, 2019 at 17:48
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2 Answers
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The answer is roundly negative.
We can measure the energy of electrons. That energy is just too high for a gravitational potential. Remember that we already know the masses of electrons, protons and neutrons, so we can compute the gravitational force. The energy of the electron in those "orbits" requires a tremendously stronger force.
When we use the electromagnetic one, it works. Quantum mechanics, in fact, predicts the behaviour of the hydrogen atom pretty well using only electrostatic interaction. With more sophisticated models, still based on electromagnetism, the atomic theory works. So I don't think there's much more to add.
If the forces are unified then it must, mustn't it?
No, it must not.
- First of all, the forces are not unified. Three of them can be explained with the same theory, but not gravity (at least not yet).
- They were only unified a few instants after the Big Bang.
- Do not try to apply dictionary definitions to science. Do it the other way round: correct the dictionary from what you know. Dictionaries are quite bad at science haha.
And finally, do not believe you understood what you heard. I'm against "popular science" because of that. People think they understood, but they didn't, and that's dangerous. I prefer teaching instead.
As others point out, "it means that they come from a common gauge group".
Understanding what that means requires, I think, many years of learning maths and physics. I encourage you to learn them, but my advise is not to try to grasp too advanced concepts without background.
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$\begingroup$ I think you'll find that the invention of science and the dictionary actually weren't separated from one another from the breadths of time that you'd like to imagine. I'd also like to point out that the philosophical considerations in quantum gravity do largely concern language and mathematics (which is also a form of language) and how these are applied. I'd challenge you to describe the universe in any meaningful way using solely an equation and not also language. $\endgroup$ Commented Jan 4, 2019 at 23:55
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1$\begingroup$ I did not mean that at all. I'm sorry if that was confusing. Language matters, and philosophy too, in fact, it's the mother of science. What I meant is that you must be careful when scientific words have another meaning in real life. For example, you cannot say "weight and mass are the same because I said I weight 80kg". How we normally speak doesn't mean that the scientific term must be used in the same way. $\endgroup$– FGSUZCommented Jan 5, 2019 at 0:14
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3$\begingroup$ It's really important to slow down and ask for definitions (which reinforces the idea that language is important, of course). We must agree in what things mean. Once the concepts are clear, we can build ideas relating concepts, but the concepts must be clear. And the dictionary is not the best help when trying to find rigorous scientif usages of words. $\endgroup$– FGSUZCommented Jan 5, 2019 at 0:16
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$\begingroup$ From what I understand of gauge theories and gauge groups points to the notion that for there to be a unification the force must share commonalities in terms of the gauge particles exchanged, in this case it would W+/- gauge bosons. If it were not these particles then gravitation could not be seen as a higher energy extension of the electroweak interaction and hence also could not be said to be unifiable with the other forces. If the W particles are not present in the fundamental interaction for gravity and there is some other particle (a graviton) it is not unified with the EW interaction. $\endgroup$ Commented Jan 6, 2019 at 18:30
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$\begingroup$ That's far different from what you wrote in the question. Consider posting another question including that. But, as you said, they are not unified. $\endgroup$– FGSUZCommented Jan 6, 2019 at 18:36
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The short answer is no. The thing responsible for bounding the orbit of the electron mainly the electrostatic potential. If you compare $\frac{V_{elec}}{V_{grav}}$ you will get an insanely large number.
answered Jan 4, 2019 at 23:15
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$\begingroup$ So is the force holding moons in orbit around planets not also an electrostatic potential? $\endgroup$ Commented Jan 4, 2019 at 23:22
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1$\begingroup$ What? I don't see how you concluded that from my answer. Gravitational force is proportional to the product of the two masses, and the electrostatic force is proportional to charge. Unification doesn't mean that forces are the same at all scales it means that they come from a common gauge group $\endgroup$ Commented Jan 4, 2019 at 23:25
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$\begingroup$ please read these answers physics.stackexchange.com/questions/275428/… $\endgroup$ Commented Jan 4, 2019 at 23:25
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2$\begingroup$ You seem to have overlooked the important phrase “at high energy” in the first sentence of that article on GUTs. The electrons in an atom are not at a the GUT energy. Moons around planets are not at the GUT energy. Nothing has been at the GUT energy after the first trillionth of a trillionth of a trillionth of a second after the Big Bang. The forces were unified when the universe was very hot. Now that it is cold, thet are no longer unified. At ordinary energies, gravity is just gravity. $\endgroup$– G. SmithCommented Jan 5, 2019 at 2:58