While people were trying to understand dark energy, the mysterious force causing the rapid expansion of the universe, scientists began to wonder about something quite futuristic. Can computers do better? The first results from a team using artificial intelligence (AI) techniques to reveal the impact of dark energy with unprecedented precision may provide an answer: Yes.
The team, led by University College London scientist Niall Jeffrey, worked with the Dark Energy Research collaboration to use measurements of visible matter and dark matter to create a supercomputer simulation of the universe. While dark energy helps push the universe in all directions, dark matter is a mysterious form of matter that remains invisible because it does not interact with light.
After creating the cosmic simulation, the team used artificial intelligence to create a precise map of the universe covering the last seven billion years and showing the actions of dark energy. The data the team uncovered represents a staggering 100 million galaxies stretching across about 25% of Earth’s Southern Hemisphere sky. Without AI, creating such a map using this data, which represents the first three years of observations from the Dark Energy Survey, would have required many more observations. The findings, when combined with dark energy dynamics, help confirm which models of cosmic evolution are valid, while ruling out the possibility that some may not be valid.
“Compared to using old-fashioned methods to learn about dark energy from these data maps, using this AI approach doubled our accuracy in measuring dark energy,” Jeffrey told Space.com. “When you use the standard method, you will need four times as much data.
Relating to: ‘Axion stars’ that exploded after the Big Bang may shed light on dark matter
Jeffrey added: “If you wanted to get this level of precision and understanding of dark energy without AI, you would have to collect the same data three more times in different parts of the sky. This would be the equivalent of mapping another 300 points.” million galaxies.”
dark energy problem
Dark energy is a sort of placeholder name for the mysterious force that is accelerating the expansion of the universe, pushing distant galaxies away from the Milky Way and each other faster and faster over time.
Today’s period of “cosmic inflation” is different from the period following the birth of the universe after the Big Bang; It appears to have come into play after the initial expansion came to a halt.
Imagine pushing a child once on a swing. Once the initial force is added, the swing slows, but instead of stopping before you push again, the swing suddenly begins moving once again. This in itself would be quite strange, but there is actually more to it. The oscillation would also begin to accelerate and reach increasingly higher heights and speeds after the motion suddenly restarted. This is similar to what happens in space; the universe bubbling outward rather than an oscillation moving back and forth.
You’d probably be pretty eager to figure out what adds that extra “push” and causes the acceleration. Scientists think the same thing about what dark energy is and how it adds an extra cosmic push to the fabric of space.
This desire is further enhanced by the fact that dark energy accounts for approximately 70% of the energy and matter budget of the universe, although we do not know what it is. When accounting for dark matter, which makes up 25% of this budget and is not composed of the atoms we are familiar with (those that make up stars, planets, moons, neutron stars, our bodies, and our neighbor’s cat), they only really have apparent access to about 5% of the entire universe.
“We don’t really understand what dark energy is; it’s one of those weird things. It’s just a word we use to describe some kind of extra force in the universe that’s pulling things apart as the expansion of the universe continues to accelerate,” Jeffery said. “Dark Energy Research is trying to understand what dark energy is. What we’re really trying to do is ask the question: Is it a cosmological constant?”
The cosmological constant, represented by the Greek letter lambda, has quite a storied history for cosmologists. Albert Einstein first introduced it in 1915 to ensure that the equations of his revolutionary theory of gravity, general relativity, supported what became known as a “static universe.”
However, this concept was challenged when Edwin Hubble’s observations of distant galaxies showed that the universe was expanding and thus expanding. Negative static. Einstein threw the cosmological constant into the scientific dustbin and allegedly described it as his “greatest mistake.”
But in 1998, two separate teams of astronomers observed distant supernovae and discovered that the universe was not only expanding, but appeared to be doing so at an increasing rate. Dark energy was invented as an explanation for the force behind this acceleration, and the cosmological constant was removed from the hypothetical dustbin.
The cosmological constant lambda represents the background vacuum energy of the universe and acts almost like the “anti-gravity” force driving the expansion of the universe. As of now, the cosmological constant is the leading evidence of dark energy.
“Our results were tightly conclusive compared to using standard methods with the same dark matter map, and we found that it was still consistent with describing dark energy by a cosmological constant,” Jeffrey said. “So we excluded some physical models of dark energy with this result.”
But that doesn’t mean the mysteries of dark energy or the headache the cosmological constant represents have disappeared.
‘The worst prediction in the history of physics’
The cosmological constant still poses a big problem for scientists.
This is because observations of distant celestial objects suggest a lambda value that is 120 orders of magnitude (10 followed by 119 zeros) smaller than that predicted by quantum physics. There is good reason why the cosmological constant has been described by some scientists as “the worst theoretical prediction in the history of physics.”
Jeffrey is clear: As pleased as the team is with these results, this research cannot yet explain the huge gap between theory and observation.
“This inequality is huge, and it shows us that our quantum mechanical theory is wrong,” he continued. “What these results can tell us is what kind of equations or what kind of physical models describe the way our universe is expanding and how gravity works by pulling together everything in the universe that is made of matter.”
Moreover, although the team’s results suggest that general relativity is the correct prescription for gravity, they cannot rule out other potential models of gravity that could explain the observed effects of dark energy.
“On the face of it, just looking at these results is consistent with general relativity — but there’s still leeway because it also allows for other theories about how dark energy or gravity works,” Jeffrey said.
This research demonstrates the benefit of using artificial intelligence to evaluate simulated models of the universe, picking out important patterns that humans might miss and thus looking for important dark energy clues.
“Using these techniques, we can get results as if we had obtained the same data three more times, which is quite surprising,” Jeffrey said.
The UCL researcher points out that carrying out these studies requires a very specific form of artificial intelligence that is well trained in detecting patterns in the universe. Cosmologists will not be able to feed universe-based simulations into their AI systems, such as adding a question to ChatGPT and waiting for results.
“The problem with ChatGPT is that if it doesn’t know something, it will make it up,” he said. “What we want to know is when we know something and when we don’t. So I think there’s still a lot of growth needed for people interested in studies that combine science and AI to get reliable results.”
RELATED STORIES:
— The expansion of the universe may be a mirage, according to new theoretical study
— Mysterious dark energy spreads evenly across the universe
— Black holes may be the source of mysterious dark energy
Six more years of data continue to arrive from the Dark Energy Survey, which, when combined with observations from the Euclid telescope launched in July 2023, are expected to provide much more information about the large-scale structures of the universe. This will help scientists refine their cosmological models and create more precise simulations of the universe, which could eventually lead them to answers to the dark energy puzzle.
“This means that the simulated universes we produce are very realistic; in a sense, they can be more realistic than what we can do with our old-fashioned methods,” Jeffrey concluded. “It’s not just about certainty, it’s also about believing these results and thinking they’re reliable.”
The team’s research is available as a preprint on the arXiv paper repository.