The smallest conceivable period of time may not be greater than one millionth of a billionth of a billionth of a billionth of a second. That’s according to a new theory that describes the implications of the universe having a fundamental clock-like property whose tics would interact with our best atomic clocks.
Such an idea could help scientists get closer to doing experiments that would illuminate a theory of everything, a general framework that would reconcile the two pillars of 20th century physics: quantum mechanics, which analyzes the smallest objects that exist, and that of Albert Einstein relativity, which describes the most massive.
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Most of us have some sense of the passage of time. But what exactly is time?
“We don’t know,” Martin Bojowald, a physicist at Pennsylvania State University at University Park, told Live Science. “We know that things change, and we describe that change in terms of time.”
Physics presents two conflicting views of time, he added. One, which comes from quantum mechanics, speaks of time as a parameter that never stops flowing at a constant rate. The other, derived from relativity, tells scientists that time can contract and expand for two observers moving at different speeds, who will disagree on the interval between events.
In most cases, this discrepancy is not terribly important. The separate realms described by quantum mechanics and relativity hardly overlap. But certain objects, like black holes, which condense a huge mass into an inconceivably small space, cannot be fully described without a theory of everything known as quantum gravity.
In some versions of quantum gravity, time itself would be quantized, meaning that it would be made of discrete units, which would be the fundamental period of time. It would be as if the universe contained an underlying field that sets the minimum tick rate for everything inside it, something like the famous Higgs field that gives rise to the Higgs’ Boson particle that lends mass to other particles. But for this universal watch, “instead of providing mass, it provides time,” Bojowald said.
By modeling such a universal clock, he and his colleagues were able to demonstrate that it would have implications for man-made atomic clocks, which use the pendulum-like oscillation of certain atoms to provide our best time measurements. According to this model, the ticks of atomic clocks are sometimes not synchronized with the ticks of the universal clock.
This would limit the accuracy of the time measurements of an individual atomic clock, which means that two different atomic clocks could eventually disagree on how much time has elapsed. Since our best atomic clocks agree with each other and can measure marks as small as 10 ^ (minus 19) seconds, or one-tenth of a trillionth of a trillionth of a second, the fundamental unit of time cannot be greater than 10 ^ (minus 33) seconds, according to the team’s document, which appeared June 19 in the newspaper. Physical Review Letters.
“What I like most about the article is the neatness of the model,” Esteban Castro-Ruiz, a quantum physicist at the Free University of Brussels in Belgium, who was not involved in the work, told Live Science. “They get a real limit that you can measure in principle, and this seems incredible to me.”
Research of this kind tends to be extremely abstract, he added, so it was nice to see a concrete result with observational consequences for quantum gravity, meaning the theory could one day be tested.
While verifying that such a fundamental unit of time exists is beyond our current technological capabilities, it is more accessible than previous proposals, such as Planck’s time, the researchers said in their document. Derived from fundamental constants, Planck’s time would set the smallest measurable tics to 10 ^ (minus 44) seconds, or one-ten-thousandth of a billionth of a billionth of a billionth of a billionth of a second, according to Universe Today.
Whether or not there is a time period less than Planck’s time is up for debate, since neither quantum mechanics nor relativity can explain what happens below that scale. “There is no point in talking about time beyond these units, at least in our current theories,” said Castro-Ruiz.
Because the universe itself began as a massive object in a small space that then rapidly expanded, Bojowald said that cosmological observations, such as careful measurements of cosmic microwave background, a relic of the big BangIt could help limit the fundamental period of time to an even smaller level.
Originally published in Live Science.
