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Thanks for those of you who took their time answering my problem but it seems that there is a misunderstanding between us. Most answers are based on the assumption of Electroweak symmetry breaking which was not my intent. My question belongs to an era even before this breaking took place. So, here is the edited version that it reflects my thought processes better than previous version of the question in the hope that new responses will be modified accordingly.


Let's assume that the singularity from which our Universe was created about 13.8 billion years ago (according to the Big Bang Standard cosmological model,) proceeded such that there was no need of any sort of spontaneous symmetry breaking (for any reason) to produce massive particles in early epochs. This would have created numerous massless fundamental particles. How do you think the history of our Universe would have been changed in terms of the underlying physics in large scales? In other words, if building blocks of our Universe (at least baryonic matter) were in fact all massless due to the absence of some sort of Mechanism, what would have happened to gravity? Here I truly mean before the epoch where EW and Strong interactions got separated. So, I am not talking about EW symmetry breaking but EW-Strong symmetry breaking (which happened even earlier than EW symmetry breaking such that even hadrons could not form into massive particles.) After all, we believe gravity is intertwined with spacetime fabric. What would have been the story if all the baryonic matter had started out being massless?

Somehow I thought knowing the answer for this question can guide us towards establishing a better understanding of Dark Matter and Dark Energy sectors. Maybe all the mystery lies in the fact that we have all three components interacting with each other and that's why it's too hard to make sense of everything. So, removing at least one component right from the beginning of the Universe (namely baryonic matter) should be a nice thought experiment.

Thank you for your time,

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marked as duplicate by CuriousOne, John Rennie, Kyle Kanos, Martin, Qmechanic Mar 18 '16 at 10:13

This question was marked as an exact duplicate of an existing question.

  • $\begingroup$ You can't take individual pieces out of the whole. They are all integral part of reality. $\endgroup$ – CuriousOne Mar 18 '16 at 5:53
  • $\begingroup$ Possible duplicates: physics.stackexchange.com/q/31395/2451 , physics.stackexchange.com/q/33334/2451 , and links therein. $\endgroup$ – Qmechanic Mar 18 '16 at 6:33
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    $\begingroup$ I'm voting to close this question as off-topic because it is an open-ended, hypothetical question. $\endgroup$ – Kyle Kanos Mar 18 '16 at 10:01
  • $\begingroup$ I don't think you understand where the masses come from. All the fermion masses come from the Higgs mechanism, which is electroweak symmetry breaking. We don't even reliably know yet that there was some electroweak-strong breaking, as that is the realm of GUTs, none of which has been reliably confirmed. $\endgroup$ – ACuriousMind Mar 19 '16 at 23:21
  • $\begingroup$ Yes. I just needed that update that GUT's are not confirmed theoretically yet. Thanks for that, $\endgroup$ – Benjamin Mar 19 '16 at 23:30
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The standard model of particle physics developed from observations made at the present time. It contains measured symmetries of massive particles which become mathematically elegant/exact at very high energies and the Higgs mechanism was invoked to explain why the two forces, weak, electromagnetic, will become one multidimensional force with zero mass gauge bosons and zero mass elementary particles in the model. This has been extended to a unification at very high energies of the strong force too (where there is no longer one higgs but a set of them).

The Big Bang model is based on this elementary particle model.

BB

History of the universe click link for link to larger image

Up to 1 nanosecond, there would be no change in the cosmological model, because the standard model higgs will not yet have broken the electroweak symmetry and the universe at that point is a soup of virtual particles; the ones that may be real will have zero mass since the Higgs symmetry breaking threshold would not have been reached.

The question then arises, will protons form by the microsecond? without protons there will be no nuclear and atomic physics and the universe would continue in a state of zero mass particles expanding away from each other.

Except if zero mass quarks due to the strong interaction would tie up into a proton as their kinetic energy fell due to expansion. A model might then be devised for a proton forming but the problem would be with the electrons, which with zero mass would be traveling at the speed of light and would have no probability of being captured in the electric field of the protons. Currently in the model, as the universe cools the protons trap electrons in the plasma and hydrogen forms and then we are off to the universe we know.

All in all, at best there might be protons (with lower mass since the constituent quarks would have zero mass , but most of the mass of the proton comes from the sea of quarks and gluons) and the rest zero mass moving with velocity of light and expanding with the universe: electrons and photons, muons and taus with zero mass not decaying, and the accompanying neutrinos , until the end.

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Higgs mechanism is predicted by standard model. So, your question basically is asking what is the best explanation if we discard that model. Per standard model, everything would just fly away at speed of light, no mass, no currently known structures, no universe in its current form.

It is possible that Higgs mechanism is not a reality. But the universe still exists. General relativity does not require standard model, but GR also assumes presence of mass, energy, and spacetime.

Possible problem with Higgs mechanism -

Higgs mechanism is supposed to impart mass to particles. We know mass is concentrated energy. That means Higgs mechanism is also expected impart energy to the particles. I am not sure if standard model says that. If particles are expected to have energy without mass, then question will be what gives energy to the particles? And then why mass energy equivalence?

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  • $\begingroup$ No mass, no gravity? This isn't correct. $\endgroup$ – Rob Jeffries Mar 19 '16 at 21:08

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