What’s the matter with the Universe? Scientists have the answer

A team of US astrophysicists has produced one of the most precise measurements ever made of the total amount of matter in the Universe, a longtime mystery of the cosmos.

The answer, published in The Astrophysical Journal on Monday, is that matter consists of 31.5 percent — give or take 1.3 percent — of the total amount of matter and energy that make up the Universe.

The remaining 68.5 percent is dark energy, a mysterious force that is causing the expansion of the Universe to accelerate over time, and was first inferred by observations of distant supernovae in the late 1990s.

Put another way, this means the total amount of matter in the observable Universe is equivalent to 66 billion trillion times the mass of our Sun, Mohamed Abdullah, a University of California, Riverside astrophysicist and the paper’s lead author told AFP.

Most of this matter — 80 percent — is called dark matter. Its nature is not yet known but it may consist of some as-yet-undiscovered subatomic particle.

The latest measurements correspond well with values previously found by other teams using different cosmological techniques, such as by measuring temperature fluctuations in the low-energy radiation left over from the Big Bang.

“This has been a long process over the course of 100 years where we’re gradually getting more and more precise,” Gillian Wilson, the study’s co-author and a professor at UCR told AFP.

“It’s just kind of cool to be able to make such a fundamental measurement about the Universe without leaving planet Earth,” she added.

So how exactly do you weigh the Universe?

The team honed a 90-year-old technique that involves observing how galaxies orbit inside galaxy clusters — massive systems that contain thousands of galaxies.

These observations told them how strong each galaxy cluster’s gravitational pull was, from which its total mass could then be calculated. (AFP | Issam AHMED)

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