If you look around the cosmos, you will see that it is made up of many ingredients with one quality in common: planets, stars, moons, even galaxies, rotate. Does it mean that the universe rotates too?
It is one of the mysteries that cosmologists have been studying deeply for a long time, because it can tell us about the fundamental nature of the universe.
“It is a very abstract question, as is most of cosmology, but those of us who study cosmology think that it is a way of studying fundamental physics ,” says Tess Jaffe, an astrophysicist at the University of Maryland (USA). and research assistant scientist at NASA’s Goddard Space Flight Center. “There are certain things that we cannot test in a laboratory on Earth, so we use the universe and the geometry of the universe, which could tell us something about fundamental physics.”
Scientists, when thinking about the fundamental nature of the universe, began by assuming that the universe is not spinning and is isotropic, which means that it looks the same in all directions. This assumption is consistent with Einstein’s equations, but is not required by them. From this thinking, scientists built a standard cosmological model that describes the universe.
To see if these assumptions about the universe and its fundamental physics were correct, the scientists gathered observations to test their models. In particular, they used the light from the cosmic microwave background. This light is the oldest that we can observe, emitted only380,000 years after the Big Bang,and it is a treasure trove of information for cosmologists studying the universe.
The cosmic microwave background is perceived almost identical in all directions,But there are small variations in its temperature, just one thousandth of a degree, that have been affected by the history, content, and geometry of the universe. By studying these differences, scientists can see if the universe has warped in any way, suggesting a rotation or expansion that increases in one direction more than another. Measurements of the polarization of light, essentially its orientation, can also provide information about the geometry of the universe.
The scientists discovered that the light from the cosmic microwave background shows no evidence that the universe is spinning or rotating. What’s more,the probability that the universe is isotropic is 120,000 to 1, which means it looks the same no matter which way we look, according to a 2016 study published in the journalPhysical Review Letters Led by Saadeh and Stephen Feeney, an astrophysicist at Imperial College. London. Another study found a 95% chance that the universe is homogeneous.
The resolution is clear
All of these studies suggest that the universe is largely uniform and not rotated. This conclusion is not likely to change. Future measurements of the polarization of the cosmic microwave background may improve in the coming decades, but the new data is unlikely to challenge previous findings.
While the result that the universe is not rotating is certainly a relief to cosmologists who have based their models on this assumption, it also gives us an interesting perspective on our place in the cosmos. See how small and insignificant we are.
