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Right now, 100 trillion ghost particles are passing through you
💡 Neutrinos are nearly massless, chargeless particles that pass through almost all matter untouched, letting us peer directly into the Sun's fusion core.
As you read this, roughly 100 trillion neutrinos stream through your body every second — mostly born in the nuclear furnace at the Sun's core. You feel nothing. They arrive during the day through the sky above you and at night straight up through the entire Earth, which barely slows them down.
The reason is that neutrinos are almost pathologically antisocial. They carry no electric charge and interact only through the weak nuclear force and gravity, so they almost never bump into anything. A neutrino could fly through a wall of solid lead a light-year thick and still have a decent chance of coming out the other side untouched.
That ghostliness makes them fiendishly hard to catch. Physicists build detectors the size of swimming pools or fill entire tanks with thousands of tons of water, buried deep underground, and wait for the rare flash when a single neutrino happens to strike an atom. Those rare hits are precious: because neutrinos escape the Sun's core directly, they give us a live X-ray of nuclear fusion happening 150 million kilometres away — confirmation that the Sun really is powered by fusion.