(ORDO NEWS) — Everything in the Universe has gravity and also feels it. However, this most common of all fundamental forces also presents the biggest challenge for physicists.
Albert Einstein’s general theory of relativity was surprisingly successful in describing the gravity of stars and planets, but it wasn’t. it seems to apply on all scales.
General relativity has undergone decades of observational testing, from Eddington’s measurement of the deflection of starlight by the Sun in 1919 to the recent detection of gravitational waves.
However, gaps in our understanding begin to appear when we try to apply it to the extremely small distances where the laws of quantum mechanics apply, or when we try to describe the entire universe.
Our new study, published in the journal Nature Astronomy, has already tested Einstein’s theory on the largest scale yet.
We believe that our approach may one day help solve some of the biggest mysteries of cosmology, and the results hint that general relativity may need to be scaled up.
Quantum theory predicts that empty space, vacuum, is filled with energy. We do not notice its presence, because our instruments can only measure changes in energy, not its total amount.
However, according to Einstein, vacuum energy has repulsive gravity it pushes empty space apart.
However, the amount of vacuum energy, or dark energy as it has been called, is necessary to explain that the acceleration is many orders of magnitude smaller than quantum theory predicts.
Hence the big question, dubbed the “old problem of the cosmological constant,” is whether vacuum energy actually gravitates – exerting a gravitational effect and changing the expansion of the universe.
If so, why is its gravity so much weaker than predicted? If vacuum doesn’t attract at all, what causes cosmic acceleration?
We don’t know what dark energy is, but we need to assume that it exists in order to explain the expansion of the universe.
Similarly, we also need to assume that there is a type of presence of invisible matter called dark matter in order to explain how galaxies and clusters evolved in the way we observe them today.
These assumptions are incorporated into scientists’ standard cosmological theory, called the Lambda Cold Dark Matter Model (LCDM), which suggests that space contains 70 percent dark energy.
25 percent dark matter, and 5 percent ordinary matter. And this model agrees surprisingly well with all the data collected by cosmologists over the past 20 years.
But the fact that much of the universe is made up of dark forces and stuff taking on strange values doesn’t make sense, prompting many physicists to wonder if Einstein’s theory of gravity needs to be modified to describe the entire universe.
A few years ago there was a new twist when it became apparent that different ways of measuring the rate of cosmic expansion, called the Hubble constant, gave different answers, a problem known as the Hubble voltage.
Disagreement or tension arises between two values of the Hubble constant.
One is the number predicted by the LCDM cosmological model, which was designed to match the light left over from the Big Bang (cosmic microwave background radiation).
The other is the rate of expansion, measured by observing the explosion. stars known as supernovae in distant galaxies.
Many theoretical ways have been proposed to modify the LCDM to explain the Hubble tension. Among them are alternative theories of gravity.
Looking for answers
We can develop tests to see if the universe obeys the rules of Einstein’s theory.
General relativity describes gravity as a warp or warp in space and time, a warp in the paths that light and matter travel.
It is important to note that he predicts that the paths of light rays and matter should bend under the influence of gravity in the same way.
Together with a team of cosmologists, we are testing the basic laws of general relativity.
We also explored whether modifying Einstein’s theory could help solve some open problems in cosmology, such as the Hubble voltage.
To find out if general relativity is true on a large scale, we first decided on time to explore three aspects of it simultaneously. This is the expansion of the universe, the effect of gravity on light and the effect of gravity on matter.
Using a statistical technique known as Bayesian inference, we have reconstructed the gravity of the universe through cosmic history. in a computer model based on these three parameters.
We could estimate the parameters using data from the Planck cosmic microwave background, supernova catalogs, and observations of the shape and distribution of distant galaxies with the SDSS and DES telescopes.
We then compared our reconstruction with the prediction of the LCDM model (essentially the Einstein model).
We found interesting hints at a possible discrepancy with Einstein’s prediction, albeit with rather low statistical significance.
This means that, nevertheless, there is a possibility that gravity works differently on large scales, and that general relativity may need to be changed.
Our research also found that it is very difficult to solve the problem of Hubble tension, it is enough to change the theory of gravity.
A complete solution would likely require a new component of the cosmological model that existed before the time when protons and electrons first combined to form hydrogen.
After the Big Bang, such as a special form of dark matter, an early type of dark energy, or primordial magnetic fields.
Or perhaps there is an as yet unknown systematic error in the data.
However, our study has shown that it is possible to test the validity of general relativity at cosmological distances using observational data.
Although we have not yet solved the Hubble problem, in a few years we will have much more data from new probes.
This means that we will be able to use these statistical methods to further tune general relativity. , exploring the limits of modifications to pave the way for solving some of the open problems of cosmology.
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