These tiny, high-energy cosmic particles are often referred to as “spectral” because they are extremely volatile or vaporous particles that can pass through any type of matter without changing.
Neutrinos have almost no mass and can travel through the most extreme environments, such as stars, planets and entire galaxies, and not change their structure at all.
“Neutrinos are these crazy and bizarre particles. Nobody has ordered all the crazy characteristics they have, they just showed up, and we’re still trying to figure out what they are,” said Peter Gorham, professor of physics at the University of Hawaii ‘ i in Mānoa. “The universe is chock full of them. A billion of them go through the nose every second and we don’t even feel it.”
Data collected by detectors in Antarctica and teams of votary scientists suggested new insights into neutrinos, as well as some anomalies that cannot be explained.
The data did not, however, demonstrate the existence of a parallel universe, says Gorham, who is also the principal investigator of ANITA, which stands for Antarctic Impulsive Transient Antenna, a high energy particle detector in Antarctica.
Why the confusion?
Recent articles from other media on some of the unusual data collected by ANITA have confused the theories of physicists outside the experiment with those of researchers who use the tool. One of these theories concerns the idea of a parallel universe. Gorham noted, however, that the team of directly involved researchers did not support this theory.
The exciting thing about the search to understand neutrinos, strange particles detected on Earth that are prevalent in the universe, is that it is ongoing and evolving – and has just begun, really. While it may take decades to truly understand what they can tell us, scientists believe that tracking down neutrinos at their sources may shed light on their origins in the distant universe.
Some physicists claim that this is leading to a new era of neutrino astronomy. Strange as they are, neutrinos can help us understand the universe in new ways. Here because.
Neutrinos on Earth
Detecting neutrinos on Earth can allow them to trace their sources, which could reveal more about the origin of the mysterious cosmic rays.
Cosmic rays, the most highly energetic particles in the universe, bombard Earth from space. Their ionizing particles in our atmosphere were first detected over 100 years ago, in 1912, by the physicist Victor Hess. He decided that they came from space.
Cosmic rays are mostly made up of protons or atomic nuclei and are launched throughout the universe because whatever produces them is an accelerator of particles so powerful as to diminish the capabilities of the Large Hadron Collider near Geneva.
But these rays have left scientists perplexed by their discovery. Where do they come from and what creates and launches them? Neutrinos could tell us.
“For me, neutrinos are the key to getting to know the universe in its most extreme form,” said Abigail Vieregg, associate professor at the physics department of the University of Chicago, Enrico Fermi Institute and Kavli Institute for Cosmological Physics.
“They will let us know the sources of the universe that produce the most energetic things that rain on us, such as cosmic rays. They travel very far across the universe. While other particles get confused in the dust of the universe, neutrinos are a signal. pure and beautiful that indicates where they come from. I think of them as a perfect messenger and they speak to us of very distant sources “.
But Vieregg said the beauty of the pure signal provided by neutrinos acts as a double-edged sword: they are difficult to detect because they don’t often interact with their surroundings.
Neutrinos interact with the ice, however. And the highest concentration of ice on our planet is found in Antarctica.
To build it, workers made 86 holes in the ice, each 1.5 miles deep, and spread a network of 5,160 light sensors on a 1-cubic kilometer grid. It is managed by a team based at the University of Wisconsin-Madison, but the IceCube collaboration includes 300 scientists and 49 institutions.
In 2013, IceCube discovered the first higher energy neutrinos beyond our galaxy and continued to observe a series of high energy neutrinos without tracking them until the summer of 2018. IceCube monitors the sky and detects around 200 neutrinos per day, but most are low energy, created when cosmic rays interact with the Earth’s atmosphere.
But he is not the only detector who tries to understand neutrinos in the ice of Antarctica.
The ANITA experiments
While the IceCube sensors are deep beneath the ice, ANITA flies over it.
ANITA’s roots go back 20 years, said principal investigator Gorham. He and physicist David Saltzberg, professor and president of the physics and astronomy department of the University of California, Los Angeles, worked on research and experiments to confirm a prediction by the Russian-Armenian physicist Gurgen Askaryan. He suggested that when a high energy particle interacts in a solid medium like ice, it creates a secondary rain of particles known as an electromagnetic cascade.
This effect could almost create a mini-lightning strike within the material in which it interacts. For example, if this particle were able to penetrate and interact deeply within the Antarctic ice, a visible blue flash would be created by lightning between 20-30 feet in length. That blue light is known as Cherenkov radiation.
Askaryan realized that in addition to the blue light, an explosion of radio emissions would also occur. In 2001, Gorham and Saltzberg managed to measure this secondary explosion of radio waves in a laboratory experiment for the first time, showing that Askaryan’s prediction of 1962 was correct.
They were attracted to the idea of using ice to detect the interaction of very high energy cosmic ray neutrinos. Radio waves spread further in cold ice than in optical light. This is how geophysicists and glaciologists can probe the bottom of glaciers and use radar to look through thick ice sheets.
ANITA has become the logical next step, Gorham said.
“If we want to see neutrinos, maybe we should fly a radio detector over Antarctica and wait for those radio explosions to appear,” Gorham told CNN, recalling a conversation he had with Saltzberg about ANITA’s design.
They designed the ANITA instrument as a radio telescope to detect high energy neutrinos that could be attached to a scientific balloon flying over Antarctica. Each flight lasted about a month, with the first one in 2006 and the last in late 2016. ANITA was funded by NASA.
So far, ANITA investigators have not seen convincing evidence of neutrinos – in the traditional definition they were looking for – through cascading explosions in the ice sheets, Gorham said.
But he found something intriguing. ANITA was designed to detect showers of cosmic ray particles through radio signals on their way to the ice or traveling back after bouncing off it.
And during its flights, ANITA found high-energy fountains of ice particles, a kind of inverted rain of cosmic rays.
Neutrinos are available in three flavors, essentially: electronic neutrinos, muon neutrinos and tau neutrinos. Although these are cousins of charged particles with unique properties, there are limited ways of distinguishing them, Gorham said.
The tau neutrino has an interesting feature in that it regenerates itself. These neutrinos are short-lived, but when they decay at high energies, they produce another tau neutrino, as well as a particle called the tau lepton, and so on. This means that they are more likely to pass than other neutrinos.
And if this decay occurs in the atmosphere, it creates a cascade of particles like a cosmic ray.
Coincidentally, ANITA is sensitive to very high energy cosmic rays that rain on Earth and create a radio burst that acts like a torch beam of radio waves.
ANITA’s unique perspective means that it is looking at the ice, in the same direction as a ray that would rain and reflect on the surface of the ice.
When ANITA observes a cosmic ray, the torch ray is really a burst of radio waves over a billionth of a second that can be mapped, like a wave, with a certain order of crests and channels to show how it reflects on ice – probably in reverse.
But twice in their data from ANITA flights, the researchers spotted what appeared to be the eruption of a high-energy particle rising through the ice. The ridge and trough order was not reversed.
Low-energy neutrinos may be able to traverse our planet unharmed, but high-energy neutrinos would experience greater arrest and not detonate from ice.
The researchers thought. Perhaps if a tau neutrino spreads across the Earth and escapes from the ice, regenerating along the way, a similar radio torch beam would face towards ANITA.
But could a tau neutrino, even with its regenerations, go so deep through the Earth and produce a rain through the ice that indicates ANITA? Gorham and his colleagues did not believe it: the neutrino would run out of gas, so to speak.
It was only the beginning of a mystery, with the signing of something too deep to be a neutrino in the normal sense, and without explanations beyond this.
ANITA and IceCube
Gorham and his colleagues are still reviewing ANITA’s fourth flight data. They used blind analysis, in which they blind themselves to certain data features, so they can’t simply produce the things they want to see.
Until the third flight, they have two events that can signal an unusual particle, or one that it could be explained by more mundane physics they don’t understand, said Gorham.
ANITA and IceCube complement each other because they can see and detect things differently.
The 48 ANITA antennas – installed on a 25 foot high balloon gondola – points to the ice from above in search of radio waves created by high-energy neutrinos when they crash into an atom in the ice.
When a neutrino interacts with the nucleus of an atom, it creates a secondary charged particle, producing a blue light cone that can be detected and mapped by the IceCube light sensor grid and traced back to its source.
“IceCube does not see these events despite the fact that our sensitivity is more than an order of magnitude greater than ANITA,” said Francis Halzen, principal investigator of IceCube and professor of Hilldale and Gregory Breit at the University of Wisconsin-Madison, in an email to CNN.
“We have published our conclusions and the ANITA collaboration does not call them into question. It remains an unsolved problem.
“It is clear however that these events cannot be neutrinos that have crossed Earth and somehow escaped detection by IceCube,” said Halzen.
“The conclusion is that they must have come from above and they reflected the ice in the ANITA detector without leaving any signature in the deep ice where IceCube would have recorded them.
“ANITA observes such routine events; they are cosmic rays reflecting off the surface of the ice. The anomaly is that two events have not changed the polarization when reflected. This is the result of new physics or an unexpected way that particles they can reflect from the surface of the polar ice cap. “
Gorham said there is an inevitable tension between the results of ANITA and IceCube because they don’t see the same things and still don’t know how to fix it. They are very different detectors that use different methods.
“In physics, that’s a good thing,” said Gorham. “It’s great to face a problem from different angles using different techniques. Sometimes, it’s the way you get the best view of something.”
Confusing about a parallel universe
There are many more details in Turok and Anchordoqui’s theories, both in the article and in their studies.
When other media the stores collected the story, what followed was a fusion of theories such as the idea of the parallel universe directly associated with Gorham’s research and statements on ANITA.
“NASA and the Gorham team do not believe that the data collected is evidence of a parallel universe,” according to an agency statement. “NASA relies on the peer review process of the scientific community through research journals and publications. Tabloids have misleadingly linked the experimental work of NASA and Gorham, who identified some anomalies in the data, to a theory proposed by physicists external unrelated to work. Gorham believes there are more plausible and easier explanations for the anomalies. “
Gorham said from his own level of intuition at this point in their work, none of the possible explanations of the anomalies are completely satisfactory. He cited the Occam razor approach: “The most likely explanation for any phenomenon is the simplest,” said Gorham. “Right now, we don’t have a simple one.”
Exotic physics, like the idea of the parallel universe, does not even provide simple explanations.
“I have no problem with this type of free speculation,” said Gorham. “I think it’s wonderful for physicists to explore all the possibilities in any abnormal result. It’s still a valid explanation, but in my opinion, it’s probably not the most likely explanation.”
After articles with incorrect information circulated, a reaction followed against the parallel universe idea.
“Neil Turok and Luis Anchordoqui, these are serious physicists,” said Gorham. “I would never do such a thing, and science shouldn’t work this way. Let’s look at the hypotheses, see if they are testable and try to do those tests.”
The future of neutrino astronomy
The next generations of IceCube and ANITA could provide the greatest amount of information and information on neutrinos to date.
For ANITA, this is PUEO and RNO. Vieregg, who was a graduate student on an ANITA early flight, will be the principal investigator for both.
PUEO is the payload for very high energy observations, similar in design to ANITA, and will also fly over Antarctica in a hot air balloon. This tool benefited from the lessons learned during the ANITA experiment. The technology developed for PUEO is 10 times more sensitive and will allow scientists to dig even deeper into the search for neutrinos, “we hope to find out what the universe has to offer the highest neutrino energies,” said Vieregg .
The Radio Neutrino Observatory is a ground-based experiment that will position radio antennas across the Greenland ice sheet. This position on the ground will allow researchers to search for lower energy particles that do not make the signal brighter, which overlaps the IceCube.
And IceCube itself will receive an update, which is called IceCube Gen 2. Progress is being made on “continuously updating the detector and our preparations for the next generation instrument which will be an order of magnitude larger,” said Halzen.
Together, PUEO, RNO and IceCube2 will act as a set of observers covering the neutrino range and their energy ranges.
“What we learned from ANITA and IceCube provides us with the tools to build the next generation and do it so we can quickly reach science,” said Vieregg.
As Gorham looks to the future of neutrino study, it unfolds more like a marathon than a sprint, but it’s worth it.
“What we do has horizons that last for a generation, that’s the benefit for the society we have to look at,” said Gorham.
“When Pierre Curie discovered the X-rays from the radio he had placed in his desk in 1890, he had no idea that, a generation later, X-rays would become the most valuable medical instrument ever, and still are. 20s and 30s we didn’t work on quantum mechanics, we would never have had transistors in the 50s and 60s. Today we wouldn’t have phones and computers.
“These things require a generation to really develop in terms of benefits, and this is certainly the case with neutrinos. It could be another generation before we understand them, and we can’t predict what the result will be, but it will probably be incredible.”
The beginning of neutrino astronomy is happening now, Vieregg said. As researchers learn the sources of these neutrinos, they can put together the bigger picture.
And we also live in an era where multi-messenger astronomy – a combination of observations and data across the electromagnetic spectrum – is helping to shed light on previously mysterious events in the universe. These messengers include the detection of gravitational waves or ripples in space-time, as well as the detection of the neutrino trace by IceCube in 2018.
“We will reap the scientific rewards in the next 10-15 years,” said Vieregg. “Neutrinos are interesting because you can combine them with other observations, such as normal telescope optics or gravitational wave observations. Put them together and we can learn even more about what’s out there in the universe.”