Can we measure radiation from the big bang?

Also at the International School for Advanced Studies is Nicoletta Krachmalnicoff. She’s part of a team trying to see further back in time than we have ever managed previously. This is into that “opaque” period that Roberto Trotta mentioned in the very young Universe. She’s planning to do it by looking at tiny fluctuations in an entity called the Cosmic Microwave Background Radiation - CMBR. This is also referred to as the afterglow of the Big bang. It’s radiation produced as the Universe was first unfurling. And imprinted into that radiation is a footprint of the structure of the Universe as things were at the time. The key is how to read it…

Nicoletta - So the cosmic microwave background radiation, CMB, is the first light emitted by our universe 380,000 years after the Big Bang. So it's the first radiation that we can see. So wherever you look in the universe, you will be able to observe this radiation. And this radiation can tell us a lot of things about how our universe was created and how it evolved.

Chris - And how does looking at light tell you anything about its history?

Nicoletta - So the point here is that this radiation has tiny fluctuations in the signal. So I told you that you can observe it in whatever direction you look, but it has tiny fluctuations in the signal. The temperature of this radiation is slightly different in every direction of the universe. And these differences are due to fluctuations present in the primordial universe. So hotter points in the universe are where we had under densities in the primordial universe, while colder spots are where there were over densities in the universe. So by studying these little fluctuations, we can learn something about the distribution of the matter in the primordial universe and then understand how these tiny fluctuations that were present in the primordial universe evolved into the structures that we can observe today.

Chris - You're working on a new experiment that's going to go live in about a year's time. What's that going to do and what will it add that we haven't already learned?

Nicoletta - CMB radiation has been observed. We have been able to observe CMB for the past 50 years. So we have studied a lot and we have learned a lot of things, but now we are trying to observe the polarization of the CMB. Part of the CMB has a preferential direction, and we can observe this polarization. And thanks to this polarization, we can understand things about what happened in the very early phase of the evolution of our universe. And with the very early phase, I mean the fraction of seconds after the big bang, what we call inflation. So inflation is a theory that the universe, in the very first instant after the big bang, went through an exponential expansion that allowed the universe to go from microscopic scales to macroscopic scales. And this theory was introduced to explain some of the observations that we have in our universe, which were not explained by the standard Big Bang theory.

Chris - Because we talk about the very early universe as being this sort of dark period. It's opaque. We can't see there because light, as we see it, could not escape. Therefore, it's literally a black box. We don't have an insight into that. But your fluctuations, polarizations, in the microwave radiation give us potentially a window into that world if they're there and you can read them.

Nicoletta - Yeah, exactly. It's not like a direct window. So we cannot observe directly this dark phase of the universe, but we can observe the imprint of this phase into the cosmic background. So if we are able to detect this very tiny signal, then we can say something about inflation.

Chris - What's the experiment you're doing? Where are you doing it? How would it work?

Nicoletta - It's going to be a network of telescopes located in Chile in the Atacama Desert. So it's a ground based experiment for telescopes with two different kind of telescopes. One smaller, like a meter diameter. And the other type of telescope will be much bigger, like six meters diameter. And thanks to the complementary of these two experiments, we hope we will be able to observe for the first time this particular polarized signal of the CMB and to prove that inflation really happened.

Chris - And when will it go live? When will the first light flow into this telescope?

Nicoletta - In the current schedule, it could be in about one year. Then we will have a phase of a few months where we like to do commissioning. So we will try to understand whether our instruments are working well and then we start to do scientific observations and we will collect a lot of data and then we will start to analyze these data. So the first results will probably come in three years from now. Something like that.

Chris - Very exciting to be sitting on what's going to give us one of potentially our earliest looks at our universe.

Nicoletta - Yeah, that's super exciting. I must say that I'm lucky to have joined this collaboration since the beginning and to be able to really now see the telescope going live.