With his theory of general relativity, Albert Einstein laid the foundation for our understanding of the universe, providing a mathematical model that made it possible to explain phenomena such as the curvature of space-time, the formation of stars and even the existence of black holes. However, a recent study conducted by a team of Canadian researchers suggests that this seemingly unassailable theory may have a flaw. Scientists have in fact identified what they called a "cosmic glitch" in gravity, that is, a 1% weakening of the gravitational pull over distances of billions of light years.
This discovery could help shed light on the enigmatic phenomenon of the accelerated expansion of the universe and pave the way for a new era in our understanding of gravity on a cosmic scale. In the meantime, I'll link you to the paper published on Journal of Cosmology and Astroparticle Physics, then we'll talk about it.
An incomplete gravity model?
Einstein's theory of general relativity, published in 1915, revolutionized the way we think about space, time and gravity. According to this model, gravity is not a force in the traditional sense of the term. It is rather a consequence of the curvature of space-time caused by the presence of mass and energy. This theory has successfully explained numerous astronomical phenomena, from the deflection of starlight during solar eclipses to the precession of Mercury's orbit.
However, when trying to apply general relativity on cosmic scales, some apparent inconsistencies emerge. How do you explain Robin Wen, lead author of the study and graduate student in mathematical physics at the University of Waterloo, “when we try to understand gravity on the cosmic scale, at the level of galaxy clusters and beyond, we encounter inconsistencies with the predictions of general relativity.” In particular, gravity appears to become about 1% weaker when considering distances on the order of billions of light years.
A “cosmic glitch” in gravity
To explain this discrepancy, the research team proposed a new model. A model that introduces what has been called a “cosmic glitch” into Einstein's theory. In essence, this is a modification to the equations of general relativity that takes into account this weakening of gravity on cosmic scales.
Think of this model as a footnote to Einstein's theory. Once you reach the cosmic scale, special terms and conditions apply.
Robin Wen
This “glitch” could help solve one of the greatest mysteries of modern cosmology: the accelerated expansion of the universe. In fact, about a century ago, astronomers discovered that the universe is not only expanding, but that this expansion is accelerating. The most distant galaxies move away from us at ever greater speeds, so much so that they appear to move almost at the speed of light, the maximum limit allowed by Einstein's theory (whatever they say).
A new era in the understanding of gravity
Secondo Niayesh Afshordi, co-author of the study and professor of astrophysics at the University of Waterloo, this discovery suggests that, on cosmic scales, Einstein's theory may simply be insufficient.
Our model of the 'cosmic glitch' may be just the first clue to a puzzle we are starting to solve across space and time.
Niayesh Afshordi
In summary, the model proposed by the Canadian team is only a first step towards a more complete understanding of gravity on a cosmic scale. Further studies and observations will be necessary to confirm the existence of this “glitch” and to explore its full implications. Even after more than a century, Einstein's theory continues to amaze us and challenge our most deeply held beliefs.
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