Recent discoveries suggest that there's a perfect symmetry between matter and antimatter - meaning it's not clear why they didn't annihilate each other upon the birth of the universe. CERN's latest study sought to find out whether different magnetic properties accounted for matter's seeming victory after the Big Bang, but found another point of symmetry. Essentially, going by our findings so far, there simply shouldn't be a universe.
So much for 'symmetry breaking' :-} — Wayfarer
Or alternatively 'no reason to assume the universe is anything but a contingent accident'. — fdrake
Very surprisingly, CP is not significantly violated by the strong nuclear force, and no one knows why. We know the strong nuclear force does not violate CP symmetry very much because of a certain property of the neutron, called an “electric dipole moment”.
Now, how big would you expect the dipole moment of a neutron to be? Well, the neutron has a radius of about 10-13 cm, so you’d expect D should be about that size. And it consists of quarks, anti-quarks and gluons; the gluons are electrically neutral, but the quarks and anti-quarks have electric charges: 2/3 e (up quarks), -1/3 e (down quarks), -2/3 e (up anti-quarks) and +1/3 e (down anti-quarks). So you might expect q to be about that size. So you’d expect the neutron to have an electric dipole moment with a size in the vicinity of 10-13 e cm. That’s about a million times smaller than the dipole moment of a water molecule, mainly since the radius of a neutron is a million times smaller.
Actually there are some subtle effects which make a more accurate estimate a little smaller. The real expectation is about 10-15 e cm.
But if the neutron had an electric dipole moment, this would violate T, and therefore CP, if CPT is even an approximate symmetry. (It also violates P.) So if CP and CPT were exact symmetries, then the electric dipole of the neutron would have to be exactly zero.
Of course we already know that CP is not an exact symmetry; it’s violated by the weak nuclear force. But the weak force is so weak (at least as far as it affects neutrons, anyway) that it can only give the neutron an electric dipole moment of about 10-32 e cm. That’s far smaller than anyone can measure! So it might as well, for current purposes, be zero.
But if the strong nuclear force, which holds the neutron together, violates CP, then we’d expect to see an electric dipole moment of 10-15 e cm or so. Yet experiment shows that the neutron’s electric dipole moment is less than 3 × 10-26 e cm!! That’s over ten thousand million times smaller than expected. And so the strong nuclear force does not violate CP as much as naively anticipated.
Why is it so much smaller than expected? No one knows, though there have been various speculations. This puzzle is called the strong CP problem, and it is one of the three greatest problems plaguing the general realm of particle physics, the others being the hierarchy problem and the cosmological constant problem.
This puzzle is called the strong CP problem, and it is one of the three greatest problems plaguing the general realm of particle physics, the others being the hierarchy problem and the cosmological constant problem
In theoretical physics, the hierarchy problem is the large discrepancy between aspects of the weak force and gravity. There is no scientific consensus on why, for example, the weak force is 1024 times as strong as gravity.
In cosmology, the cosmological constant problem or vacuum catastrophe is the disagreement between measured values of the vacuum energy density (the small value of the cosmological constant) and the zero-point energy suggested by quantum field theory.
Depending on the assumptions, the discrepancy ranges from 40 to more than 100 orders of magnitude, a state of affairs described by Hobson et al. (2006) as "the worst theoretical prediction in the history of physics."
Wrong conclusion. It finds that current models don't necessarily match what is seen. If the findings were accurate, the universe should be different, but concluding that it should not exist is an absurd category error.Essentially, going by our findings so far, there simply shouldn't be a universe.
Science is a work in progress. Shock horror. — apokrisis
Confirmed universe is click baiting physicists. — Marchesk
It ought to give pause to any form of physicalism that such questions are still so wide open. — Wayfarer
You do realise that you only hear about these "crises in physics" because physics is right on the doorstep of an answer? — apokrisis
The confident predictions of science providing a naturalistic 'theory of everything' seem to be getting more, not less, remote. — Wayfarer
As far scientific cosmology is concerned, I am aware that at least some respectable scientists entertain the idea that 'The Big Bang' might have been one of a series. — Wayfarer
In which case, we're back at the Myth of the Eternal Return and a cyclical cosmos which, for unknown reasons, seems to have formed the backdrop of ancient Indian cosmology. — Wayfarer
You do realise that you only hear about these "crises in physics" because physics is right on the doorstep of an answer?
It has a range of candidate theories - any number of them generated by its armies of theoreticians. — apokrisis
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