Neutrino masses are weird. First we thought neutrinos were massless. Then we thought they had positive mass. Then some evidence pointed to an IMAGINARY mass, which was crazy. That went away when the data got better. Now some people say evidence from cosmology points to a NEGATIVE mass. But I think this is even more crazy.
You may think Einstein said
E = mc²
but actually his theory, special relativity, says
E² = m²c⁴ + p²c²
where p is momentum. So you can measure energy and momentum and figure out the SQUARE of mass - not mass itself.
You might think mass creates gravity, but actually it's energy and momentum that create gravity, and we use the above equation to figure out mass from those.... or really the mass SQUARED.
If the mass squared is negative, you've got something with imaginary mass, which is called a tachyon. Tachyons are bad - take my word for it.
But if the mass squared is positive, the mass itself could be positive or negative. And it doesn't really matter which, since in special relativity all that matters is mass squared!
You might think we can figure out mass just by *weighing* something - that is, using gravity. But in general relativity, gravity interacts with energy and momentum. So those are what matter. We work out mass from the formula above... but actually, it only tells us mass squared.
Some new experiments in cosmology are somewhat in conflict with each other, in ways that supposedly could be explained by neutrinos with negative mass. But I don't buy it.
I could be confused. I'll think about it more....
https://www.sciencenews.org/article/neutrino-mass-phenomenon-cosmology
You may think Einstein said
E = mc²
but actually his theory, special relativity, says
E² = m²c⁴ + p²c²
where p is momentum. So you can measure energy and momentum and figure out the SQUARE of mass - not mass itself.
You might think mass creates gravity, but actually it's energy and momentum that create gravity, and we use the above equation to figure out mass from those.... or really the mass SQUARED.
If the mass squared is negative, you've got something with imaginary mass, which is called a tachyon. Tachyons are bad - take my word for it.
But if the mass squared is positive, the mass itself could be positive or negative. And it doesn't really matter which, since in special relativity all that matters is mass squared!
You might think we can figure out mass just by *weighing* something - that is, using gravity. But in general relativity, gravity interacts with energy and momentum. So those are what matter. We work out mass from the formula above... but actually, it only tells us mass squared.
Some new experiments in cosmology are somewhat in conflict with each other, in ways that supposedly could be explained by neutrinos with negative mass. But I don't buy it.
I could be confused. I'll think about it more....
https://www.sciencenews.org/article/neutrino-mass-phenomenon-cosmology
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