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“Six thousand billion of them are going through your body every second.” That’s physicist Lawrence Krauss on neutrinos, on the June 15th weekly Science Talk podcast. “Neutrinos are the lightest elementary particles we know of. The name comes from the fact that they had to be neutral because we couldn’t see them in detectors. But they had to be light. So Enrico Fermi called them "a little neutron," in Italian is neutrino. So they were baby neutrons, which were the only other neutral particles at the time that were known.”
Now astrophysicists [Shaun Thomas, Ofer Lahav and Filipe Abdalla] have put a best-guess upper limit on the mass of the neutrino. The research is being reported this week at the Weizmann U.K. conference at University College London and will appear in an upcoming issue of Physical Review Letters.
The work took advantage of the huge 3-D galaxy map called Mega Z. Because there are so many neutrinos, their tiny masses add up to influence the overall distribution of galaxies. And the researchers say the galactic map depends on a neutrino’s mass being no more than 0.28 electron volts, less than a billionth of the mass of an atom of hydrogen, the lightest element. “These are the most interesting particles in nature.”
—Steve Mirsky
[The above text is an exact transcript of this podcast.]
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6 Comments
Add CommentAren't estimates based on estimates based on estimates ad nauseam just a bit like a house built on ethereal cards?
Reply | Report Abuse | Link to thisJust to illustrate: what would the probability of failure be for a construction of 10,000 components, each with a 10% confidence factor?
Isn't this carrying things just a bit too far? What calculations will now be based on this dubious estimate of neutrino mass?
@jtdwyer, the point here is not to make a definitive claim about the mass of the neutrino but to apply what we do know to put some constraints on the system. You're analogy is an appeal to ridicule as the numbers you have offered are clearly ridiculous and do not reflect the actual system being discussed. What calculations like this can be used for is setting up experiments to determine if this is in fact the case. If one is looking for something, one often starts by taking a guess at where they might find it, as it is impossible to simultaneously look everywhere. If they guess wrong not only have they eliminated a possibility but they have learned that their model is missing some key element. You don't seem to understand the scientific "process". It is not about proving something with absolute certainty. It is about refinement. This hypothesis suggests how the estimation of the mass of the neutrino can be refined. Now, hopefully an experiment can be assembled to test it. Best to understand something before you criticise it.
Reply | Report Abuse | Link to thisrobert schmidt - I'll give a more 'concrete' example of well established ethereal data:
Reply | Report Abuse | Link to thisOnly about 4.6% of the mass-energy of Universe is thought to be ordinary matter; about 23% is thought to be composed of dark matter; the remainder is thought to be dark energy.
This is currently widely accepted, despite there being no direct evidence for the existence of dark matter. It has only been indirectly inferred by observed gravitational effects that exceeded that expected of the estimated mass of observed matter, based on astrophysicists' gravitational estimations. Standard practices can produce errors when applied to new conditions. Perhaps you don't understand scientific practice.
@jtdwyer, "This is currently widely accepted", no it is not widely accepted as being a fact. It is considered a good candidate and a valid hypothesis. Until it is proven it will not be "accepted" as factual. I do understand science and margins for error. This hypothesis includes in it a margin for error, that is why it is a range, an upper limit, rather than being a fixed amount. You are making a common error that many people without a science background make when criticising science, if they can show that science can't quantify something precisely they claim science doesn't know anything about the subject at all. That is binary thinking. You are claiming that something is either known completely or not at all. As scientific theories are refined more and more constraints are placed on the system limiting the range of possible values, limiting the "margin of error". Are these concepts too difficult for you? Once again you don't seem to appreciate the difference between a hypothesis and a theory. You don't seem to understand that science is a process. You seem to expect that everything posted here should be an absolute, uncontroversial fact rather than a best estimate based on what we know. Show some humility, it is quite arrogant to think that despite you having done no work in the field that you know better than the people who are actually crunching the numbers. Consider for a moment that the reason you disagree with their findings is because you don't understand the problem or the proposition and instead are inserting your own prejudices.
Reply | Report Abuse | Link to thisSteve Mirsky writes this stuff just to see if we're still awake.
Reply | Report Abuse | Link to thisBut, given all he writes is absolutely true--riddle me this:
What is that mass as measured in Higgs Bosons?
We do want to be current, don't we? Electronvolts are so 1980's.
Quinn the Eskimo - Well put, but first we'll have to make our best-guess on the upper limit of the mass mediated by the Higgs Boson...
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