It seems that the Physicists who first thought this concept up may have made some weak assumptions. One of the more glaring is that, from what we believe, a neutrino can only be formed as a result of certain processes such as beta decay as part of a fusion or fission nuclear reaction. That means that particles a LOT more massive than neutrinos were involved and must have existed.
It is still unclear if neutrinos even have any mass at all, but if they do, it is certainly far less than the mass of an electron, the smallest nuclear particle we know of which has mass. But even an electron has an extremely small mass, only around 1/1836 the mass of a proton or 1/1838 the mass of a neutron.
So, the obvious question is, if even ONE percent of the mass of the Universe happens to consist of neutrinos, where did all the mass of the necessary protons and neutrons go?
An example is:
Using the Atomic Mass Unit (AMU) (around 1.65 * 10-24 gm) as basis:
1.00866491578 decays to 1.00727646688 + 0.0005485799110 + neutrino + 0.78 Mev/931 Mev (or 0.0008374). Or 1.00866491578 = 1.008662446791 + neutrino. This could suggest a maximum mass of a neutrino as 0.000002469, only a few millionths of the mass of a proton and less than 1/200 the mass of an electron. And all of the values involved have statistical error values which are on that order of magnitude. This is why some Physicists still think that neutrinos have exactly zero mass. If they have any, it is a VERY small amount!
The point of these numbers here is that, for a neutrino (or anti-neutrino) to be created, there are necessarily other resulting particles, such as an electron and a baryon (proton in this case), each of which must exist and each of which has a mass many times greater than any mass a neutrino could have.
So, if Physicists insist that there are so many of these neutrinos that exist that they represent 90% or 99% of the mass of the entire Universe, they should explain where all the also created electons and positrons have gone, and where all the baryons that were involved disappeared to. It seems that, even if neutrinos are created in enormous numbers, they still could not be nearly as massive as even the total electrons which exist, and that is far less total mass than the (equal) number of baryons.
If an argument is to be made that "electrons could be recycled", alternately creating neutrinos and anti-neutrinos during beta- and beta+ decays, the logic seems to stretch credibility! The idea that every electron merrily enables outrageous numbers of neutrinos and anti-neutrinos, without any of them ever reacting / re-combining to annihilate, seems to violate every rule of both logic and Physics!
Thirty years ago, some Physicists had postulated that there MUST BE enormous amounts of "dark matter" in all galaxies in order to enable they to (appear to) rotate as they do. That was the original incentive for dark matter, and the later speculations that it MUST BE enormous numbers of neutrinos. Both assumptions seem rather unsupported by data. If simple Newtonian gravitation can explain the observed stability of spiral arms and their apparent non-keplerian rotations, then there is no longer any need to speculate about enormous numbers of neutrinos! They are really not needed for any other theories.
There is a web presentation that presents the gravitational explanation mentioned above, at:
I have always wondered about this assumption. These statements consider spin to be a simple number, where addition and subtraction work as in second grade problems! But any Physicist knows that angular momentum is a VECTOR quantity; it has not only a magnitude (size) but also a direction. Therefore, Pauli had assumed that all the spins of particles were always lined up along the same axis, where they could then be added and subtracted. This may have been a good assumption, but it is not clear to me exactly why that would have to be the case. What if the spins of a proton and electron happened to be aligned along non-parallel axes? Then, when they would combine to create a neutron, maybe the vector sum of 1/2 plus 1/2 could still equal, 1/2, but it would be aligned in yet a third direction!
We know that various atoms are generally oriented relatively randomly in space, not necessarily aligned with each other unless there is an external electric or magnetic field present. Why would it be required that a specific electron have its spin axis exactly lined up with the spin axis of some proton it encounters? That does not seem logical!
More than that, we know from Physics (specifically Euler) that angular momentum can only be altered in specific ways. In the case of a gyroscope, friction of bearings gradually reduces the amplitude of the angular momentum. We do not believe there is any such mechanism in nuclear interactions. And trying to change the direction of a spin axis, actually causes a precession effect along an entirely different axis. So, if anyone would try to claim that a proton axis and an electron axis somehow line up in the process of forming a neutron, a really good (Euler Equation) explanation of just how that axis chance could occur seems necessary. But, it seems that it has simply been assumed that spin can be treated as a simple scalar quantity, to be added and subtracted, that argument then requiring the existence of an invisible, possibly massless particle known as the neutrino.
Since that neutron beta decay into a proton and electron is the basic argument for the existence of neutrinos, because of the apparent violation of conservation of angular momentum, it seems that someone should provide a far more credible argument than to just assume that a scalar addition is the explanation!
After Pauli postulated the existence of the neutrino, it became universally accepted in Nuclear Physics, but no experiment gave even the slightest confirmation of its existence for about 25 years! And those results, and all later results, have been extremely indirect, never actually detecting an actual neutrino! A popular approach is to install an experiment in a very deep mine, so that human activities on the surface, and atmospheric and cosmic events should not be able to affect the results.
One popular approach is to have a giant tank of pure water, surrounded by thousands of very sensitive light sensors. The logic of this kind of detector is that a neutrino impacts an electron, transferring its energy to the electron, in principle as a kinetic energy transfer. The electron is therefore given an extremely high velocity, slightly slower than the speed of light in a vacuum but faster than the speed of light in water! The result is an optical shockwave akin to a sonic boom, and it is known as Cherenkov radiation, which creates a unique pattern of light that the light sensors detect.
This argument seems fairly sound, but it actually contains a number of assumptions which must all be true for the results to actually be identifying neutrinos. For example, all of the Earth layers contain small amounts of radioactive materials, so even though the experiments are deep in mines to shield them from cosmic rays, it seems that the possibility might exist that some high energy decay could occur somewhere near the mine and cause an effect that might be detected, not necessarily having anything to do with neutrinos themselves!
( http://mb-soft.com/public/index.html )
C Johnson, Physicist, Physics Degree from Univ of Chicago