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 Large Bang kick-started the universe as we all know it 13.8 billion years in the past. Many theories in particle physics counsel 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 house. Nevertheless, antimatter particles exhibit the alternative properties of their corresponding matter particles.

When items of matter and antimatter collide, they annihilate one another in a robust explosion, abandoning solely power. The puzzling factor about theories that predict the creation of an equal steadiness 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 will need to have been extra matter than antimatter on the delivery of the universe, as a result of the universe isn’t empty; it’s filled with stuff that’s manufactured from matter, like galaxies, stars, and planets. A bit little bit of antimatter exists round us, however it is extremely uncommon.

As a physicist engaged on Subaru knowledge, I’m on this so-called matter-antimatter asymmetry downside. In our current examine, my collaborators and I discovered that the telescope’s new measurement of the quantity and sort of helium in faraway galaxies could 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 filled with elementary particles like protons, neutrons, and electrons swimming round 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 components like hydrogen and helium started to kind. This course of is named Large Bang Nucleosynthesis. The nuclei shaped have been about 75 p.c hydrogen nuclei and 24 p.c helium nuclei, plus small quantities of heavier nuclei.

The physics group’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, 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 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 is dependent upon the relative variety of neutrinos and antineutrinos within the early universe. If extra neutrinos have been current, then our fashions present extra protons and fewer neutrons would exist in consequence.

Because the universe cooled, hydrogen, helium, and different components 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 accessible within the early universe, the much less helium can be produced.

As a result of the nuclei shaped throughout Large Bang Nucleosynthesis can nonetheless be noticed immediately, 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 might be wealthy in mild components 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 might be nearly completely made up of hydrogen and helium.

Utilizing a way that permits researchers to tell apart completely different components 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 end result, my collaborators and I labored backward to search out the variety of neutrinos and antineutrinos vital to supply the helium abundance discovered within the knowledge. Assume again to your ninth grade math class whenever you have been requested to resolve 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 previously-accepted concept predicted that there needs to be the identical variety of neutrinos and antineutrinos within the early universe. Nevertheless, once we tweaked this concept to provide us a prediction that matched the brand new knowledge set, we discovered that the variety of neutrinos was better 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 recognized and certain particle physics processes, the asymmetry within the neutrinos may propagate into an asymmetry in all matter.

The results of our examine is a standard kind of end result within the theoretical physics world. Mainly, we found a viable manner wherein the matter-antimatter asymmetry may have been produced, however that doesn’t imply it positively was produced in that manner. The truth that the info matches with our concept is a touch that the speculation we’ve proposed is likely to be the right one, however this reality 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 is likely to be.

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Picture Credit score: NASA