Neutrinos are neutral particles that usually cross ordinary matter without interacting. IceCube studies rare high-energy neutrinos using light sensors deep in Antarctic ice.

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The particles crossing your body

The Short gives an estimate of about 100 trillion neutrinos per second through a person's body. It illustrates the scale of the solar-neutrino flow. The exact count depends on projected body area and the chosen estimate.

The Sun produces neutrinos during nuclear fusion in its core. Fusion joins light nuclei through reaction chains and releases energy. Some reactions also release neutrinos.

Neutrinos have no electric charge and very small masses. The lack of charge prevents ordinary electromagnetic interactions. Their weak-interaction probability is small, but not zero.

Through buildings and Earth

Most low-energy solar neutrinos cross buildings and Earth without interacting. When the Sun lies below the horizon, its neutrinos approach through the ground. Night therefore does not stop their arrival.

This claim needs its energy range. Earth absorbs a significant fraction of sufficiently high-energy neutrinos. The penetrating ability of a solar neutrino cannot apply unchanged to every IceCube event.

The lead-wall example

A light-year is the distance light travels in a year. The Short imagines lead with that thickness to illustrate a very low interaction probability.

The fraction crossing depends on neutrino energy. A Fermilab teaching example gives about half crossing, so “most” is not a reliable universal value. The example concerns low-energy neutrinos, rather than every neutrino from every source.

A different population at IceCube

Ordinary solar fusion neutrinos have energies below IceCube's usual detection range. The observatory instead studies much higher energy events, including neutrinos from distant astrophysical sources.

The original deep array contains 5,160 optical modules on 86 strings. Each string carries 60 modules. Hot-water drilling places them deep in ice, which later freezes around the instruments.

Francis Halzen receives the 2026 physics prize for the IceCube work and discoveries. The observatory itself depends on a large international collaboration.

How a rare interaction becomes light

A neutrino occasionally interacts in or near the ice. The interaction can create charged particles. Those particles can travel faster than light travels through ice while remaining below the vacuum speed limit.

This produces Cherenkov radiation, including the blue light shown in the animation. Sensors measure its arrival pattern. Researchers reconstruct the interaction's direction and energy from that pattern.

The neutrino does not simply strike an atom and turn into a visible photograph. The detector observes secondary particles through their light.

The distant galaxy example

A September 2017 event prompts a rapid alert to other telescopes. Observations identify a flaring blazar in the corresponding sky region, roughly four billion light-years away.

A blazar is an active galaxy with a jet pointing about toward Earth. The evidence supports a likely source association. It does not make every individual neutrino's origin certain.

What this means

During a Short lasting many seconds, the opening approximate rate gives thousands of trillions of crossings. That scale concerns the abundant low-energy flux, not a comparable number of detected cosmic events.

Neutrinos can reveal hidden sources because they interact so rarely. The same property makes their detection difficult and demands large instruments.

FAQ

Does IceCube detect the solar neutrinos in the opening?

No. Ordinary solar fusion neutrinos lie below its usual energy range.

Does anything stop neutrinos?

Yes. Interaction probability depends on energy, material, and path length.

Does a detector see a neutrino directly?

It measures products of an interaction, including secondary light.

Sources