By Jay, from 凹非寺
QbitAI | Official Account QbitAI
Just now, the Nobel Prize in Physics has been announced.
This time there was no tie at all; the winner was just one person, from the University of Wisconsin–Madison in the United States.Francis Halzen(Francis Halzen).
If you don't know this university, you should still know it has a well-known alumnus in China's tech and internet sector—
Pinduoduo founder,Colin Huang (Huang Zheng)。
So, why exactly did Francis win the prize?
Here is what the official statement says:
In recognition of his decisive contributions to the IceCube Neutrino Observatory at the South Pole, and for the discovery of high-energy neutrinos of astrophysical origin.
Specifically, he took the [data/samples from] more than 2,000 meters deep beneath Antarctica's1 cubic kilometerpure ice layers, forcibly transformed into a machine that captures ghostly particles from the universe.Super Telescope。。。
Today, there is even a highland in Antarctica named after him, calledHalzen Mesa。
Why capture "ghosts" in the deep ice of Antarctica?
There has long been an ultimate puzzle in the universe that has troubled the physics community for a hundred years: where exactly do those cosmic rays with absurdly high energies get emitted from?
The universe contains natural particle accelerators that spit out protons with energies millions of times higher than those of the most powerful accelerators in Earth's laboratories. But protons carry an electric charge, and as they race through the cosmos they get twisted around by interstellar magnetic fields, so by the time they arrive at Earth, no one can tell which direction they came from.
How can one find the true source?
Physicists have turned their attention to neutrinos.
Neutrinos are the shyest particles in the universe—electrically neutral and with an extremely tiny mass. Every second,65 billionNeutrinos from the sun pass through your thumbnail, yet you feel absolutely nothing.
Places where high-energy protons are accelerated are often accompanied by high-energy neutrinos. Neutrinos carry no electric charge, are not disturbed by magnetic fields, and are not blocked by interstellar dust, like a straight-line target pointing directly to their birthplace deep in the universe.
But how do you catch it?
Neutrinos occasionally collide with atomic nuclei, producing charged particles and emitting an extremely faint blue light. As long as the medium is sufficiently transparent and large in volume, photodetectors can be used to record their trajectories.
Although the deep sea is transparent, it is full of lively bioluminescence, plus ocean current interference. In the 1980s, Halzen proposed a bold idea: go to Antarctica and use natural ice!
Melt 2.5-kilometer-deep wells with hot water to create a giant eye under 1 cubic kilometer of ice
Catching particles in the icy wastes of Antarctica sounds like pure fantasy.
The ice deep beneath Antarctica is in complete darkness, with no marine creatures causing trouble and an extremely stable geological structure, free from earthquake interference. The only headache-inducing problem was: how do you stuff sensors into a glacier more than two thousand meters thick?
The research team came up with an extremely hardcore solution—using specially made high-temperature hot-water drill bits to melt shafts more than two thousand meters deep into the Antarctic ice, then quickly sinking cables studded with photosensitive sensors into the icy water.
Halzen described these sensors as reverse light bulbs: they do not emit light, only capture faint light signals and convert them into electrical signals.
When the early pilot experiment AMANDA first started, everyone was nervous. The shallow ice was full of tiny air bubbles, and light entering it was scattered to pieces.
But when the drill descended below1400 meterssomething magical happened—the pressure crushed and squeezed out all the air bubbles, and the ice below was astonishingly pure and transparent. Blue light produced by neutrino collisions could even travel300 metersthrough the ice before being absorbed!
After feasibility was verified, IceCube officially got to work.
When it was completed in 2011, the entire IceCube was buried deep beneath the Antarctic ice at1450 to 2450 metersand consisted of86 cables、and 5160 optical sensorsturning a full1 cubic kilometerof natural glacier into an unprecedented neutrino telescope.
Capturing the ghosts of the universe and opening a brand-new door to astronomy
Even with this giant telescope, searching for signals from deep space remains like looking for a needle in a haystack.
Every day, more than one hundred million cosmic ray particles from the atmosphere above Antarctica pass through the detector, along with hundreds of neutrinos from the atmosphere on the other side of the Earth that penetrate through the crust.
Filtering out high-energy neutrinos that truly come from the distant universe amid a massive amount of background noise makes data processing incredibly difficult.
In 2013, the IceCube team finally announced that it had, for the first time, clearly captured high-energy cosmic neutrinos from beyond the solar system. This breakthrough directly won that year's Physics World Breakthrough of the Year award.
In the years that followed, key evidence kept appearing:
Scientists recorded 79 neutrino candidate signals in the direction of the active galaxyNGC 106879 neutrino candidate signals were recorded in the direction of (M77), locking in a potential extreme astrophysical source.
In 2023, the IceCube team produced the first image of high-energy neutrinos from the plane of the Milky Way, allowing humanity to see the full picture of our galaxy through the eyes of neutrinos for the first time.
After visible light, radio, X-rays, and gravitational waves, astronomy's door to high-energy neutrino astronomy has been fully pushed open.
About the Nobel laureate: from hadron physics to building a telescope under the ice
This physicist who single-handedly won the Nobel Prize in Physics, Francis Halzen, is 82 years old this year.
Born in Tienen, Belgium in 1944, he received his doctorate in 1969 from KU Leuven in Belgium, and in his early years mainly studied quark-composed heavy particles and symmetry breaking in hadron physics.
After completing his postdoctoral research, he went to the University of Wisconsin–Madison in the United States, where he has taught long-term since 1972 as a professor in the physics department.
The classic textbook he co-authored, Quarks and Leptons, has accompanied generations of particle physics students around the world through their studies.