Yes, the sunlight you see today was likely created in the Sun's core about 100,000 - 300,000 years ago. We are bathed in ancient starlight every day. However, we know that the Sun's core is still producing energy because of "neutrinos," nearly massless particles produced in nuclear reactions. Neutrinos pass through the Sun like cannon balls through fog banks so they escape from the core immediately. In fact, in the time it takes you to read this sentence, trillions of neutrinos from the Sun's core and other sources have passed through your body, through Earth and into outer space where they will likely travel for billions of years without constraint.
The detection of electron neutrinos from the Sun's core indicates that
our parent star is still producing energy in its core. (Image: SOHO)
Even though a neutrino would only have a fifty percent chance of being absorbed by a light year of lead, some of them will occasionally interact with certain atoms, such as chlorine. For instances, the interaction of a chlorine atom and a neutrino will produce argon through a radioactive process that scientists will detect. The detection of these solar neutrinos (properly called "electron neutrinos") lend us the assurance that our Sun is working just fine!
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FROM THE CATACOMBS OF INFINITE KNOWLEDGE
Neutrinos were once thought to have had no mass. Now, physicists know they contain some mass, albeit precious little. A single neutrino's mass is a minute fraction of that of an electron, which is just a whisper of a thing (or a non thing, if you're a devotee of the new Zen Quantum religion.) While a single neutrino is the ultimate lightweight, the neutrinos en mass might have enough matter to account for much of the dark matter spread throughout the Universe.
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