Time is an elastic band: how scientists want to measure its distortion in distant galaxies
A new experiment could help unravel the mysteries of dark matter, dark energy and the fifth force.
Scientists want to measure time distortion in ancient, distant galaxies to solve fundamental mysteries of our reality, including the potential existence of a “fifth force” beyond established physics, a new study reports.
The researchers hope to find signs of an effect called gravitational redshift, where light turns redder after it escapes the gravitational pull of massive objects. This redshifted light contains clues about how the gravitational fields of massive objects warp time, which could limit a number of unanswered questions about our universe.
For example, time distortion measurements can reveal whether the laws of gravity change at extreme scales in ways that are not predicted by Albert Einstein’s theory of relativity or Leonhard Euler’s equations describing celestial motions. This concept of “modified gravity” can assess whether a mysterious force called dark energy is causing our universe’s expansion to accelerate and shed light on dark matter, the unidentified substance that makes up the vast majority of mass in space. It can also explore the existence of an undiscovered fifth force that only acts on particles of dark matter, not on the particles that make up planets, stars, and people.
Camille Bonvin, assistant professor of cosmology at the University of Geneva, has been developing a mathematical method to measure the distortion of time for several years now. Now Bonvin and Levon Poghosyan, professor of physics at Simon Fraser University, have come up with a plan to get a “direct measurement of time distortion” and find “a possible smoking gun for modified gravity,” according to research published Thursday in the journal Nature Astronomy.
“The reason we want to test Einstein’s equations is because there’s one big mystery in our universe that we don’t yet know how to explain,” Bonvin said. “We have observed that about 8 billion years after the big bang, the expansion of the universe begins to accelerate, and we do not know the reason for this. Such an accelerated expansion is impossible if gravity is described by general relativity (Einstein’s theory of gravity) and if our universe contains only matter and radiation.”
“Also, the reason we want to test the Euler equation is because we have never tested it for dark matter,” he continued. “Euler’s equation describes the motion of matter in the universe. It has been tested and confirmed very accurately for ordinary (visible) matter. However, we believe that in addition to ordinary matter, there is a large amount (85%) of dark invisible matter in the universe.”
To measure the distortion of time, scientists plan to use data from the James Webb Space Telescope, which will launch later this year. This telescope will be able to observe the light from the most distant and ancient galaxies in the universe. By comparing the redshift of light from these galaxies with the redshift of light from closer objects, scientists can determine the degree of time distortion.
“We want to measure the difference between the redshift of light from a galaxy and the redshift of light from a supernova or quasar in the same galaxy,” Bonvin explained. “This difference depends on how much time slows down under the influence of gravity.”
If measurements show that time is warped more or less than standard physics theories predict, this could indicate that gravity works differently on cosmic scales. It could also confirm or disprove the hypothesis of a fifth force that influences dark matter.
“The fifth force is a hypothetical force that only acts on dark matter, not on ordinary matter,” Poghosyan said in an email. “If it exists, then it could be responsible for accelerating the expansion of the universe.”
Poghosyan added that time distortion measurements could also help scientists understand the nature of dark energy, a hypothetical force that some believe is causing the expansion of the universe to accelerate. However, he noted that dark energy and the fifth force are not mutually exclusive hypotheses and both could be real.
“Dark energy is a generic name for any mechanism that can cause the expansion of the universe to accelerate,” he said. “The Fifth Force could be one such mechanism.”
Scientists hope that their method of measuring time distortion will help them test these hypotheses and unlock the mysteries of our reality.
“We want to understand what the nature of dark matter and dark energy is,” Bonvin said. “Those are the two biggest questions in cosmology today.”