New knowledge about the origins of our universe.

New data published today by the Atacama Cosmology Telescope (ACT) in Chile indicates that our universe is around 13.8 billion years old, which coincides with measurements made by the Planck satellite in 2015 and questions the 2019 findings of another group of research that determined age. of the universe to be much younger than the Planck satellite had predicted. That study had measured the motion of galaxies to arrive at their number, while ACT measured polarized light to reach its conclusions.

Mark Halpern, a UBC professor in the department of physics and astronomy, is part of the international team collaborating on the ACT, which includes scientists from 41 institutions in seven countries. We spoke to Halpern about these new findings and their importance.

How does the ACT telescope work?

The Atacama Cosmology Telescope is a six meter diameter telescope with a very sensitive camera that measures polarized light. It is one of the highest elevation observatories in the world, located along the Chilean Andes mountain range to avoid having to look through the humid air. The telescope itself was built by Empire Dynamic Systems in Port Coquitlam, and taken from Vancouver to Chile by boat.

It is tuned to work at wavelengths close to a few millimeters, where the brightest thing in the sky is a thermal glow left over from the plasma that filled the early universe. ACT spends all its time scanning from one side to the other, making the most sensitive maps of cosmic structure possible. What’s new in this data post is that our polarization measurements are very accurate. The brightness of the sky tells us about the structure in the early universe. Polarization tells us about movement. Together, the data gives us a very detailed picture of the dynamics.

What do these new findings tell us about the age of the universe? And why is this significant?

The importance of these results, for me, is that even with improved data and a better understanding, our model of the universe remains very well. Age is not really the big issue here. We used to think that the universe was about 13.77 billion years old, roughly 40 million years old. Now we believe that it is 13.790 million years old, more or less 21 million years old.

Maybe 21 million years sounds like great uncertainty, but as a fraction, this is very accurate. Imagine a doctor examining a 50-year-old patient, and based on his current condition, not his history, estimating his age to the nearest 25 days!

We can be so accurate because the data is excellent, the model fits very well, and the model is simple. Considering the data, we understand the system, and there aren’t many options for how the universe has aged. The amazing thing is how self-aware we are, and what this tells us about our lives is that we can know that the universe has a beginning and know its age with a high degree of precision.

Do these findings raise new questions about our universe and its origins?

Yes and no. The main story is that these data add quite a bit of precision to our measurements, and yet the simplest model in our universe remains in very good shape. This has been an extraordinary story over the years, with the data improving in accuracy by a factor of 100,000 and the same models still fitting.

But these data add to the strain on the overall cosmological data set. When we infer the Hubble constant, the universe’s current expansion rate, the cosmic microwave background (CMB), and other large-scale measurements, we get a different value than the one that is measured more locally than is called a distance ladder. If this difference is real, it is a challenge for cosmological models.

What’s next for the ACT?

Our observations continue. Our next big goal is to look for a small polarization pattern that violates parity. If we see it, it is a clue to the gravitational radiation generated in the first moments of the birth of the universe. Many experiments, not just ACT, are looking for this signal.