When you travel throughout space, you’ll see that many objects — planets, stars, moons, and even the galaxy, Is the universe, in turn, spinning?
Cosmologists have been researching this problem closely because it has the potential to provide information about the universe’s essential nature.
“It’s a really abstract subject, like much of cosmology,” Tess Jaffe, an astrophysicist at the University of Maryland and an assistant research scientist at NASA’s Goddard Space Flight Center, said. “We can’t test some things in a lab on Earth, so we turn to the cosmos and its geometry, which may reveal something about basic physics.”
Scientists began by believing that the cosmos is not spinning and is isotropic, meaning that it appears the same in all directions when considering the universe’s basic nature. This assumption is supported by Einstein’s equations, although it isn’t needed. Scientists developed a cosmological model that explains the cosmos due to this reasoning.
“This [assumption] is actually ingrained in the way we perform our calculations, the way we evaluate our data, in a lot of ways,” Daniela Saadeh, a research fellow at the University of Nottingham’s School of Physics and Astronomy, told Live Science. “However, it is necessary to put it to the test. It’s not enough to just wish for the best.”
Scientists collected data to test their models to check whether their assumptions about the cosmos and basic physics were correct. The radiation from the cosmic microwave background, or CMB for short, was utilized in particular. This light is the earliest we can see, produced only 380,000 years after the Big Bang. It contains a wealth of data for cosmologists investigating the cosmos.
The CMB seems essentially the same in all directions. Still, minute temperature fluctuations have been influenced by the universe’s history, content, and geometry, ranging from a thousandth of a degree to a thousandth of a degree. Scientists can discover whether the cosmos has been distorted in any manner by examining these discrepancies, which would indicate a rotation or expansion that is greater in one direction than the other. Measurements of light’s polarization, or direction, may also provide details about the universe’s shape.
According to scientists, the CMB light does not exhibit any signs of the cosmos spinning. According to a 2016 research published in the journal Physical Review Letters led by Saadeh and Stephen Feeney, an astrophysicist at Imperial College London, the universe’s probability that the universe is isotropic is 120,000 to 1 everything seems the same no matter which way you look. According to another research, there’s a 95% likelihood that the cosmos is homogenous, which means it’s the same everywhere on huge sizes.
These investigations indicate that the universe is mostly uniform and does not rotate. This is a hard-to-change conclusion. Further observations of the CMB’s polarization may improve in the next decades, but the new evidence is unlikely to overturn prior conclusions.
“We’ve described the [temperature] signal to the point where it doesn’t have any more information for us,” Jaffe told Live Science. “I don’t believe [new polarization data] will have much of an influence on the issue of the rotation, exactly because the rotation is the signal we’d expect to see at very large scales, and that has been ruled out by the evidence we currently have.”
While discovering that the world is not spinning is a relief for cosmologists whose models were built on this assumption, it also provides us with an unusual perspective on our location in the cosmos.
“As humans, we began with the concept that we were the center of the universe,” Saadeh said. “It’s amazing how little and unimportant we are,” says the narrator.