Everything in the Universe has gravity – and feels it too. This most fundamental force is the most common, but it presents the greatest challenges for physicists.
Albert Einstein’s Theory of General RelativityIt has been extremely successful in explaining the gravity of planets and stars, but it doesn’t seem to work well on all scales.
General relativityMany years of observational testing have been passed. Eddington’s measurementThe deflection of starlight from the Sun in 1919 to the Recent detections of gravitational waves.
When we try to apply it to very short distances, however – gaps in our knowledge begin to show. Quantum mechanics operates according to the lawsOr when we attempt to describe the whole universe.
Our new study, Publié in Astronomy of NatureNow, he has tested Einstein’s theory at the largest scale.
We believe that our approach will one day resolve many of the greatest mysteries in cosmology. Our results also suggest that the theory about general relativity may need some tweaking on this scale.
Failure of the model
Quantum theory says that empty space, or the vacuum, is filled with energy. It is not visible because our devices are able to measure energy changes rather than the total amount.
However, according to Einstein, the vacuum energy has a repulsive gravity – it pushes the empty space apart. It was found that the Universe’s expansion is actually accelerating in 1998 (a finding which was awarded the 2011 Nobel Prize in Physics).
However, the amount and quality of vacuum energy are not comparable. dark energyIt is necessary to explain acceleration, as it is sometimes called. The acceleration is much smaller than quantum theory predicts.
Hence the big question, dubbed “the old cosmological constant problem”, is whether the vacuum energy actually gravitates – exerting a gravitational force and changing the expansion of the universe.
If it is, then why does its gravity seem weaker that predicted? What is causing the cosmic acceleration if the vacuum doesn’t gravitate?
Although we don’t know the exact nature of dark energy, it is something that we must assume in order to explain the expansion of the Universe.
In the same way, we need to assume that invisible matter exists, which is also what we call dark matterTo explain how galaxies formed into the clusters we see today.
These assumptions are baked into scientists’ standard cosmological theory, called the lambda cold dark matter (LCDM) model – suggesting there is 70 percent dark energy, 25 percent dark matter, and 5 percent ordinary matter in the cosmos. The model has been remarkable in fitting all data collected by cosmologists over 20 years.
Many physicists wonder if Einstein’s theory of gravity must be modified to explain the universe.
An innovative twist was added to the equation when it was discovered that there were different methods of measuring cosmic expansion. Hubble constant, give different answers – a problem known as The Hubble tension.
The Hubble constant has two values. This is the reason for the tension or disagreement.
One is the number that the LCDM cosmological modeling predicts. It was developed to match. The light that remains from the Big Bang (the Background cosmic radiation radiation).
Another is the expansion rate determined by looking at supernovas, which are exploding stars in distant galaxies.
Many theories have been put forward to modify LCDM in order to explain Hubble tension. Alternate gravity theories are just a few of the options.
Looking for answers?
We can create tests to verify Einstein’s theory.
General relativity defines gravity as the curving of space and time and the warping of matter and light. It predicts that gravity will also affect the trajectories for light rays as well as matter.
With a team of cosmologists we tested the basic laws general relativity. We also looked into whether Einstein’s theory modification could be used to resolve some of the unresolved problems in cosmology such as the Hubble tension.
We set out to investigate three aspects of general relativity simultaneously in order to determine if it is true on large scales. These were the expansion and effects of gravity upon light, as well as the effects of gravitation on matter.
The Bayesian inference is a statistical technique that reconstructs the gravity of a universe through cosmic history. This computer model uses these three parameters.
The Planck satellite’s cosmic microwave background data, supernova catalogues and observations of the distributions of distant galaxies by the Observator of the Shapes and Distribution of Far-Eastern Galaxies (Observator of the Atmosphere) could be used to estimate the parameters. SDSS DES telescopes.
The reconstruction was then compared to Einstein’s prediction for the LCDM model.
Interesting hints were found that Einstein’s prediction might be mismatched, but with low statistical significance.
This suggests that gravity may work differently at large scales and that general relativity theory might need to be modified.
Our study also revealed that it is difficult to solve the Hubble tension issue by changing only the theory of gravity.
To find the complete solution, a new component would likely be needed in the cosmological modeling. It would have to be present before protons or electrons first combined to create hydrogen shortly after the Big Bang. Big Bang, such as a particular form of dark material, an early type or primordial magnetic field.
Perhaps there is an undiscovered systematic error in data.
Our study proved that observational data can be used to verify the validity of general relativity at cosmological distances. Although we still have not solved the Hubble problem yet, we will soon have more data from new probes.
This means we can use statistical methods to continue tweaking general relativity and exploring limits of modifications in order to resolve some open problems in cosmology.
Kazuya KoyamaProfessor of Cosmology. University of Portsmouth Levon PogosianProfessor of Physics. Simon Fraser University
This article was republished by The ConversationUse the Creative Commons license Please read the Original article.
