Why scientists’ latest calculations on dark matter and dark energy are so important

Why scientists' latest calculations on dark matter and dark energy are so important
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In 1998, scientists stumbled upon a surprising cosmic truth. Not only is the universe expanding, they realized, but it also appears to be throttle As the years go by, accelerated by a force we can’t see.

That mysterious influence would soon be known as dark energy, one of the greatest puzzles in physics.

It would complement the equally, if not more, confusing aspect of our universe called dark matter, a general concept that scientists First evidenced in 1933 to describe whatever constitutes the hidden halo-like barriers that prevent galaxies from simply falling apart. (Another force that we cannot understand with human eyes).

But even though we are unable to understand the elusive nature of dark matter and dark energy with sight, we can measure it with mathematics. And on Wednesday, in a series of articles in the Astrophysical Journalastrophysicists managed to place the most precise limits so far about the composition and evolution of our universe, including the dark universe.

Using a powerful analytical engine called Pantheon+, the team found that the cosmos is made up of roughly two-thirds dark energy and one-third matter, mostly in the form of dark matter. More specifically, they suspect that 66.2% of the universe manifests as dark energy, while the remaining 33.8% belongs to both dark and visible matter.

Even more exciting than the result of Pantheon+ may be the amazing way it operates. In short, the team harnessed a series of powerful cosmic lanterns to look back in time and document the contents of the universe as they were more than 10 billion years ago.

By “flashlights,” I mean Type 1a supernovae.

These starbursts are so bright that they outshine entire galaxies and are therefore seen from distances of billions of light-years away from Earth. They are like flashlights, but instead of illuminating a long corridor, they illuminate the infinite tunnel of space and time. In fact, they are central to the discovery of the dark universe, helping to discover the existence of dark matter in 1933 and dark energy in 1998.

Pantheon+ took things to the next level. The scientists behind the analysis focused on more than 1,500 supernovae that, when brought together, collectively light up about three-quarters of the known universe. Wow, actually.


A timeline of the universe.


“With this combined Pantheon+ dataset, we get an accurate view of the universe from when it was dominated by dark matter to when the universe became dominated by dark energy,” said Dillon Brout, an astronomer at the Harvard-Smithsonian Center for Astrophysics. . he said in a statement.

“This dataset is a unique opportunity to see how dark energy ignites and drives the evolution of the cosmos on the largest scales up to the present,” said Brout.

This could settle some scientific debates.

Further ahead, the legacy of Pantheon+ is ready to transcend the dark universe.

As a bonus, the analytical tool also confirmed that the cosmos really is expanding at an accelerating rate. Y offered extremely promising evidence in support of a cornerstone of scientific thought: The standard model of particle physics.

This framework largely describes how each known particle behaves independently, as well as with each other, and even serves as the basis for many major theories about what the dark universe is really about.


An image of the particles in the Standard Model.


“We are able to put the most precise constraints on the dynamics and history of the universe to date,” said Brout. “We have reviewed the data and can now say with more confidence than ever before how the universe has evolved over the eons and that the best current theories about dark energy and dark matter remain sound.”

In other words, Pantheon+ could be telling us that we should conclude some alternative theories of dark matter and dark energy. not related to the Standard Model. Those theories could be, well, wrong.

In addition, we also have to talk about my personal favorite consequence of the Pantheon+ datasets. At long last, it could help end a long-standing, rather heated debate among physicists.

We may finally be on the way to deciphering what is known as Hubble’s constant. Something like.

Basically, we know that the universe is expanding exponentially. We can literally see it happen in real time. But scientists can’t agree on the exact speed at which that expansion is occurring. The key to the solution is the Hubble constant, but different ways of calculating that constant seem to give different answers.


Arcs and streaks in the galaxy cluster Abell 370 reveal “gravitational lensing,” the distortion of light from distant background galaxies by the cluster’s gravitational field. Lensing helps astronomers measure the distribution of dark matter in galaxy clusters.

NASA, ESA and the Hubble SM4 ERO team

Although after combining the Pantheon+ sample with data from another scientific collaboration, a press release from Harvard claims that we may now have the most accurate local measurement of the current expansion rate of the universe. (The key word here is “local”. That will come up later.)

In a nutshell, the collaboration found the Hubble constant to be 73.4 kilometers (45.6 miles) per second per megaparsec (km/s/Mpc) with a surprising 1.3% uncertainty.

“Put another way, for every megaparsec, or 3.26 million light-years, the analysis estimates that in the nearby universe, space itself is expanding at more than 160,000 miles per hour,” the statement explains. That figure, for context, is right in the middle of 2001. historical measurement of 72 km/s/Mpc and later reports of 74 km/s/Mpc.

However, it is quite far from another leading measurement that suggests a constant 69.8 km/s/Mpc.

OK, yes, there is still a discrepancy. And, again, the Pantheon+ constant is based on “local” measurements.

As such, the Pantheon+ team emphasizes that “observations from a completely different time in the history of the universe predict a different story.” So, in a way, having a new contrasting Hubble constant could No resolve the Hubble tension, but add to the already tense debate? Like I said, it’s complicated.


A simulation of filaments of dark matter throughout the universe.

Zarija Lukic/Lawrence Berkeley National Laboratory

“We thought it might be possible to find clues to a novel solution to these problems in our data set, but instead we found that our data rules out many of these options and that the deep discrepancies remain as stubborn as ever,” said Brout. . .

But at the end of the day, because the Pantheon+ results are so pristine, perhaps they could at least clarify where the sticking point lies in the ongoing Hubble debate.

“Many recent theories have begun to point to exotic new physics in the very early universe,” said Brout. “However, such unverified theories must withstand the scientific process, and the Hubble strain remains a major challenge.”

Physics is chock full of brain teasers and brain teasers and, honestly, straight up obstacles. But I like to imagine these obstacles as motivation to keep the field going and minds turning. That’s why Pantheon+ was innovated in the first place.

And with this mechanism, we’ve absolutely made progress in dissecting the truth about the dark side of our universe, if nothing else. Or as Brout puts it, “Pantheon+ is giving us our best chance yet to constrain dark energy, its origins, and its evolution.”

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