When theoretical physicists like myself say that we’re finding out 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 Massive 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 area. Nonetheless, antimatter particles exhibit the other properties of their corresponding matter particles.
When items of matter and antimatter collide, they annihilate one another in a robust 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 had been true, the 2 would have completely annihilated one another, leaving the universe empty. So there will need to have been extra matter than antimatter on the start of the universe, as a result of the universe isn’t empty; it’s stuffed with stuff that’s manufactured from matter, like galaxies, stars, and planets. A little bit little bit of antimatter exists round us, however it is rather uncommon.
As a physicist engaged on Subaru knowledge, I’m on this so-called matter-antimatter asymmetry downside. In our latest examine, 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 Massive Bang
Within the first milliseconds after the Massive Bang, the universe was scorching, dense, and stuffed with elementary particles like protons, neutrons, and electrons swimming round in a plasma. Additionally current on this pool of particles had been neutrinos, that are very tiny, weakly interacting particles, and antineutrinos, their antimatter counterparts.
Physicists consider that only one second after the Massive Bang, the nuclei of sunshine parts like hydrogen and helium started to type. This course of is named Massive Bang nucleosynthesis. The nuclei shaped had been about 75 p.c hydrogen nuclei and 24 p.c helium nuclei, plus small quantities of heavier nuclei.
The physics neighborhood’s most widely-accepted concept on the formation of those nuclei tells us that neutrinos and antineutrinos performed a basic position within the creation of helium nuclei, particularly.
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 collection 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 are able to 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 extra neutrinos had been current, then our fashions present extra protons and fewer neutrons would exist in consequence.
Because the universe cooled, hydrogen, helium, and different parts shaped 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 out there within the early universe, the much less helium could be produced.
As a result of the nuclei shaped throughout Massive Bang nucleosynthesis can nonetheless be noticed at this time, scientists can infer what number of neutrinos and antineutrinos had been current throughout 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 outdoors of our personal which are virtually solely made up of hydrogen and helium.
Utilizing a method that permits researchers to differentiate completely different parts from each other based mostly on the wavelengths of sunshine 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 previously-accepted concept predicted.
With this new outcome, my collaborators and I labored backward to search out the variety of neutrinos and antineutrinos mandatory to supply the helium abundance discovered within the knowledge. Assume again to your ninth grade math class once you had been requested to resolve for “X” in an equation. What my group did was primarily the extra refined model of that, the place our “X” was the variety of neutrinos or antineutrinos.
The previously-accepted concept predicted that there ought to be the identical variety of neutrinos and antineutrinos within the early universe. Nonetheless, once we tweaked this concept to present us a prediction that matched the brand new knowledge set, we discovered that the variety of neutrinos was higher than the variety of antineutrinos.
What Does It All Imply?
This evaluation of latest 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 examine, my collaborators and I proved that this new measurement of helium is per there being extra neutrinos then antineutrinos within the early universe. By way of identified and certain particle physics processes, the asymmetry within the neutrinos might propagate into an asymmetry in all matter.
The results of our examine is a typical sort of outcome within the theoretical physics world. Mainly, we found a viable means through which the matter-antimatter asymmetry might have been produced, however that doesn’t imply it positively was produced in that means. The truth that the information matches with our concept is a touch that the idea we’ve proposed is likely to 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 previous query, “Why does something exist?” In accordance with this new analysis, they only is likely to be.
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Picture Credit score: NASA
