Anne-Katherine Burns, University of California, Irvine
When theoretical physicists like myself say that we’re learning why the universe exists, we sound like philosophers. However new knowledge collected by researchers utilizing Japan’s Subaru telescope has revealed insights into that very query.
The Big Bang kick-started the universe as we all know it 13.8 billion years in the past. Many theories in particle physics recommend that for all of the matter created on the universe’s conception, an equal quantity of antimatter ought to have been created alongside it. Antimatter, like matter, has mass and takes up space. Nonetheless, antimatter particles exhibit the alternative properties of their corresponding matter particles.
When items of matter and antimatter collide, they annihilate each other in a powerful explosion, forsaking solely vitality. The puzzling factor about theories that predict the creation of an equal stability of matter and antimatter is that in the event that they have been true, the 2 would have completely annihilated one another, leaving the universe empty. So there should have been extra matter than antimatter on the delivery of the universe, as a result of the universe isn’t empty – it’s stuffed with stuff that’s made from matter like galaxies, stars and planets. A little bit little bit of antimatter exists around us, however it is extremely uncommon.
As a physicist working on Subaru data, I’m on this so-called matter-antimatter asymmetry problem. In our recent study, my collaborators and I discovered that the telescope’s new measurement of the quantity and kind of helium in faraway galaxies might supply an answer to this long-standing thriller.
After the Large Bang
Within the first milliseconds after the Large Bang, the universe was sizzling, dense and stuffed with elementary particles like protons, neutrons and electrons swimming around in a plasma. Additionally current on this pool of particles have been neutrinos, that are very tiny, weakly interacting particles, and antineutrinos, their antimatter counterparts.
Physicists consider that only one second after the Large Bang, the nuclei of sunshine elements like hydrogen and helium started to type. This course of is called Big Bang Nucleosynthesis. The nuclei fashioned have been about 75% hydrogen nuclei and 24% helium nuclei, plus small quantities of heavier nuclei.
The physics neighborhood’s most widely accepted theory on the formation of those nuclei tells us that neutrinos and antineutrinos performed a elementary function within the creation of, specifically, helium nuclei.
Helium creation within the early universe occurred in a two-step course of. First, neutrons and protons transformed from one to the opposite in a series of processes involving neutrinos and antineutrinos. Because the universe cooled, these processes stopped and the ratio of protons to neutrons was set.
As theoretical physicists, we will create fashions to check how the ratio of protons to neutrons depends upon the relative variety of neutrinos and antineutrinos within the early universe. If more neutrinos were present, then our fashions present extra protons and fewer neutrons would exist in consequence.
Because the universe cooled, hydrogen, helium and different parts formed from these protons and neutrons. Helium is made up of two protons and two neutrons, and hydrogen is only one proton and no neutrons. So the less the neutrons obtainable within the early universe, the much less helium could be produced.
As a result of the nuclei fashioned throughout Large Bang Nucleosynthesis can still be observed today, scientists can infer what number of neutrinos and antineutrinos have been current in the course of the early universe. They do that by wanting particularly at galaxies which are wealthy in gentle parts like hydrogen and helium.
A clue in helium
Final yr, the Subaru Collaboration – a gaggle of Japanese scientists engaged on the Subaru telescope – launched knowledge on 10 galaxies far exterior of our personal which are nearly completely made up of hydrogen and helium.
Utilizing a way that permits researchers to differentiate completely different parts from each other based on the wavelengths of light noticed within the telescope, the Subaru scientists decided precisely how a lot helium exists in every of those 10 galaxies. Importantly, they discovered much less helium than the beforehand accepted concept predicted.
With this new consequence, my collaborators and I labored backward to search out the number of neutrinos and antineutrinos crucial to supply the helium abundance discovered within the knowledge. Assume again to your ninth grade math class once you have been requested to unravel for “X” in an equation. What my staff did was basically the extra refined model of that, the place our “X” was the variety of neutrinos or antineutrinos.
The beforehand accepted concept predicted that there must be the identical variety of neutrinos and antineutrinos within the early universe. Nonetheless, once we tweaked this concept to offer us a prediction that matched the brand new knowledge set, we found that the variety of neutrinos was higher than the variety of antineutrinos.
What does all of it imply?
This evaluation of recent helium-rich galaxy knowledge has a far-reaching consequence – it may be used to elucidate the asymmetry between matter and antimatter. The Subaru knowledge factors us on to a supply for that imbalance: neutrinos. On this research, my collaborators and I proved that this new measurement of helium is in line with there being extra neutrinos then antineutrinos within the early universe. By way of known and likely particle physics processes, the asymmetry within the neutrinos might propagate into an asymmetry in all matter.
The results of our research is a typical sort of consequence within the theoretical physics world. Mainly, we found a viable method through which the matter-antimatter asymmetry might have been produced, however that doesn’t imply it undoubtedly was produced in that method. The truth that the info suits with our concept is a touch that the idea we’ve proposed could be the proper one, however this truth alone doesn’t imply that it’s.
So, are these tiny little neutrinos the important thing to answering the age outdated query, “Why does something exist?” In line with this new analysis, they only could be.
Anne-Katherine Burns, Ph.D. Candidate in Theoretical Particle Physics, University of California, Irvine
This text is republished from The Conversation beneath a Inventive Commons license. Learn the original article.
