Measurements of galaxy clusters at vast distances confirm Newton's and Einstein's laws and strengthen the existence of dark matter
Gravity, one of the most fundamental forces in nature, continues to prove its stability even on the largest scale ever tested. A new study, published in the journal Physical Review Letters, presents the most extensive examination yet of the laws of gravity – confirming that they work exactly as predicted by Isaac Newton and Albert Einstein, even at vast cosmic distances.
The study, led by physicist Patricio Gallardo of the University of Pennsylvania, examined the motion of galaxy clusters separated by hundreds of millions of light years. The result: the strength of gravity decreases with distance according to the inverse square law – just as formulated back in the 17th century.
The "missing mass" problem returns to center stage
The study was born out of one of the biggest problems in cosmology: the gap between the amount of visible matter and the behavior of galaxies. Observations show that stars and galaxies are moving faster than can be explained by visible matter alone.
This problem led to two main options:
Either there is invisible matter – dark matter – or the laws of gravity themselves are different on a large scale.
The new study supports the first possibility. Since the laws of gravity have been found to be valid even at vast distances, it seems that the solution is indeed the existence of additional, invisible matter.
How do you measure gravity on a cosmic scale?
The researchers used data from the Atacama Cosmology Telescope, which measures the cosmic microwave background radiation – the oldest light in the universe, emitted about 380 years after the Big Bang.
When this light passes through galaxy clusters, their motion affects it, creating tiny distortions. Analyzing these distortions allows us to measure the speed of the clusters and the strength of gravity acting between them.
The researchers analyzed hundreds of thousands of galaxy clusters, examining how gravity works over tens of millions of light years – the most comprehensive examination done to date.
Affirming classical law – and rejecting alternatives
The results showed complete agreement with Newton's and Einstein's predictions, thereby undermining alternative theories, such as Modified Newtonian Dynamics (MOND), which propose modifying the laws of gravity to explain the behavior of galaxies.
The implication is clear: if the laws of gravity do not change, another explanation for the gap is needed – and the most likely explanation is the existence of dark matter.
According to Gallardo, "It is impressive to see that a law that was drafted more than 300 years ago continues to operate on a scale that was unimaginable at the time."
Open riddle: What is dark matter?
Despite confirmation of its existence, the nature of dark matter is still unknown. Scientists do not know what it is made of, how it can be directly detected, or how it fits into the framework of known physics.
The current study doesn't solve the puzzle, but it narrows down the possibilities. It strengthens the standard cosmological model and directs future efforts toward discovering matter itself, rather than changing the laws of gravity.
In the future, a combination of more precise measurements of the cosmic microwave background radiation and large-scale surveys of galaxies is expected to further deepen our understanding.
More of the topic in Hayadan:
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Is it possible that at cosmological distances, the mass of matter increases and therefore it is assumed that there is dark matter, when in fact the weight of existing matter increases!!!
Shaul Shaltiel did not.
Because in that case it would *absorb* some of the radiation. Not only that, it would absorb in a typical frequency range. For example, dust blocks visible light, but is transparent to infrared (which is one of the reasons the Webb Space Telescope sees in infrared).
Dark matter *does not interact at all* with electromagnetic radiation *in any domain*. And in fact does not interact with any matter in any way except gravity.
By the way, this shows that there is no such thing as "transparent", but rather transparent to a certain frequency range. For example, your house is transparent to light in the microwave and radio ranges, but not to visible light. If the house were opaque to this range, you would have no reception at home.
Unfortunately, the article is completely wrong.
The reason is that the authors do not understand that the "dark matter" effect is a near-field effect and not a far-field one and therefore is not reflected in the distances between galaxy clusters.
For details, please refer to my articles:
Yahalom A. Effects of Higher Order Retarded Gravity. Universe. 2021; 7(7):207. https://doi.org/10.3390/universe7070207. https://arxiv.org/abs/2108.08246
Isn't it possible that dark matter is ordinary matter that does not radiate (brown dwarfs, dust, gases) or is radiated and therefore not visible in astronomical observations?