Monday, Aug 6 2001
The Phantoms of the Universe- Neutrinos
- Divya ThakurDivya Thakur is a 16 year old high school senior in Austin, TX who aspires to major in aeronautical engineering. Fierce with dreams and zeal, Divya is still looking for a way to combine her interests in science, writing and the White House (in that order), though still in vain. When asked for the likelihoods of her finidng such a profession she quoted, "It is hard to find a cat in a dark room especially when there is no cat"-Confucious. Whatever her future might hold in store for her, she knows never to lose her main goal in life, that is to invent a new figure of numbers, a quadrillion, herself being the sole proprieter.
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Centered on the Sun's postion, the picture covers a significant fraction of the sky (90x90 degrees in R.A. and Dec.). Brighter colors represent a larger flux of neutrinos.
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One of the most perplexing aspects of the universe, particles known as neutrinos are also one of the most fundamental. In a tantalizing recent announcement, an international collaboration of researchers at Super Kamiokande or Super-K in Japan, has now presented evidence that the ghostly neutrinos undergo quantum mechanical oscillations, changing their particle identities and quantum properties over time, thus implying neutrinos have mass. So what's all the fuss about? Just what is it about Neutrinos that gets it the attention no other astrophysical anomaly attracts?
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Space Ghosts
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Neutrinos are unique subatomic particles that are produced in supernovae and in nuclear reactions and very rarely interact with matter. They have no electrical charge, travel essentially at the speed of light, are far lighter, if not virtually massless, than electrons and come in three types: electron-neutrino, muon-neutrino and tau-neutrino. These particles are so elusive that you do not notice the hundred billion solar neutrinos that pass through your thumbnail every second. To this phantom-like neutrino, the world is as barren and empty as the bottomless rabbit hole that Alice finds herself perpetually falling in. Virtually unstoppable and all but undetectable, neutrinos would seem to be of tremendous use to the physicists.
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Because neutrinos can penetrate almost any barrier, they carry information about some of the most inaccessible places in the heavens above and beyond, from the cores of collapsing stars, to gamma-ray bursts, to the black hole-powered jets of active galaxies.
Why the Hype?
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The recent evidence for neutrino oscillations comes from studying solar neutrinos. Nuclear reactions in the sun were thought to produce only electron-neutrinos, but the actual number of electron-neutrinos observed from the sun was far less than that estimated. Scientists accounted for this by the "oscillating" theory, or the random metamorphosis to tao-neutrinos or muon-neutrinos. For the first time this was confirmed experimentally when a flux of muon-neutrinos was discovered coming from the sun. The solar-neutrino problem was finally solved, pending only independent conformation for the skeptics.
The Dark Mystery
Scientists have known for decades that all the visible matter in galaxies does not account for nearly enough mass to explain the rotation speeds of galaxies and galactic clusters- the gravitational force would not be great enough to prevent the galaxies from flying apart. This is known as the dark matter problem - there has to be a significant amount of mass in some intangible form that resides in our universe. The mass of everything we see around us from the stars in the heavens to the sand under our feet is mostly accounted for by the mass of protons and neutrons. Here's where the numbers come into play. For every proton or neutron in the universe there are about a billion neutrinos! So even if neutrinos have minuscule masses, their sheer number and ubiquity would make them accountable for a significant fraction of the total mass of our Universe, and at least help to partly solve the quandary of the dark matter.
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Solar experiments at Super-K
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A Web of Riddles
The latest findings also challenge the existing model, or the 'Standard Model' of our universe. In a nutshell, matter is hypothesized as being constructed of six quarks and six leptons. In the simplest standard model, neutrinos have zero mass, which implies that each kind of neutrino is immutable. Thus, this evidence that a neutrino oscillates, spontaneously changing from one form to another, as for example an electron-neutrino to a tau-neutrino and so forth, is the first experimental evidence that the standard model in its present form is somewhat flawed, giving scientist yet another conundrum to unravel.
Neutrinos have intrigued scientists for over decades. With the latest findings, its perplexities are now within our comprehension, securing another missing link and bringing us closer and closer to unlocking the mysteries of the heavens. However, as one mystery is solved, a quagmire more seem to appear. The link might very well be the key to a Pandora's Box, unleashing an army of quandaries that manage to defy every level of our understanding. And there will come a time when the quest for solving the enigma of who we are and where we came from will take us places where the fine line between science and faith might cease to exist.
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