We’re all too familiar with the inexorable march of time, but why exactly it
flows in one direction remains a mystery of physics. A few years ago
Australian physicist Joan Vaccaro proposed a new quantum theory of time, and
now a team is planning to test the hypothesis by searching for time dilation
in a nuclear reactor.
The “arrow of time” points from the past towards the future, but physics has
a hard time explaining why it favors one direction over the other. The most
widely accepted explanation for this asymmetry is covered by the second law
of thermodynamics, which states that time tends to flow in the direction of
increased entropy, which is essentially the measure of disorder in a system.
But according to Vaccaro’s quantum theory of time, entropy is more of a
symptom of the flow of time, rather than the root cause. She uses the
analogy of a tree blowing in the wind – while the leaves (entropy) may
appear to be shaking the tree, they aren’t responsible for the motion
themselves, but are the result of another force (wind). In this new theory,
the "wind" is created by time reversal symmetry violations (T violations).
Vaccaro points out that physics regards space and time as being
interconnected, as spacetime. But nature seems to treat the two differently.
From experience we know, for instance, that objects are localized in space –
a particular book or tree or person can only be found in one specific spot.
Yet that’s not the case for time – that same book or tree or person can be
found in a range of times. Because spacetime is one thing, theoretically
objects localized in space should be localized in time as well, popping in
and out of existence.
Obviously that’s not our experience with the universe, and it goes against
the laws of motion and conservation of mass. But, Vaccaro proposes, T
violations make it impossible for matter to remain localized in time.
Because of T violations, objects don't appear and disappear at random, they
exist continuously. What we know of as the laws of motion and conservation
of mass are instead symptoms of these T violations.
Vaccaro proposes that something on the quantum scale creates T violations
locally, and if enough of them occur it could begin to have a wider effect
on the macro scale – essentially producing the dynamics we see as time
moving forward.
Vaccaro’s quantum theory of time is a pretty major departure from accepted
physics, and she freely admits that it’s controversial and may very well be
wrong. But importantly, like any good hypothesis there’s a way to test it
experimentally.
The Experiment
Subatomic particles called neutrinos may hold the key to unlocking the whole
thing. Recent studies have suggested that neutrinos exhibit time symmetry
violations.
So in a new study, researchers from Griffith University, the National
Measurement Institute (NMI) and the Australian Nuclear Science and
Technology Organization (ANSTO) are attempting to measure these T violations
from neutrinos.
Neutrinos and their antimatter counterparts, anti-neutrinos, are produced in
nuclear reactors, so that’s where the new experiment will be conducted. The
team has installed two extremely precise atomic clocks in the OPAL reactor
in Sydney, and the idea is that if the clocks fall out of sync, it would be
evidence of quantum time dilation, which itself would be evidence of local T
violations.
Time dilation is a well-studied phenomenon, predicted by the theory of
relativity. If you have an atomic clock on the ground and one on a satellite
orbiting Earth, the ground clock will tick ever-so-slightly faster than the
one in the sky. That’s thanks to differences in gravity, which bends
spacetime.
Vaccaro says that there’s currently no reason to believe that time dilation
should also occur in a nuclear reactor, so if any sign of it is found it
could support her hypothesis.
To investigate, the team will use two timing stations, one placed 5 m (16.4
ft) from the reactor and the other 10 m (32.8 ft). Each station contains a
cesium primary clock, three secondary clocks and a series of measurement
systems that will compare the clocks down to under a billionth of a second,
looking for any discrepancies.
The experiment will gather data continuously for six months, including
regular periods where the reactors will be shut down for maintenance. These
will serve as useful controls, since any time dilation effects should stop
during the downtime.
And the results could be fascinating. It’s almost expected that there would
be a null result, returning us to the established path of physics. But if
the experiment does find evidence of time dilation, it could be a huge
breakthrough. That’s a big “if,” but one worth at least checking.
“All I’ve said could completely be wrong,” Vaccaro says in a video
presentation from 2017 (below). “But it’s not me that decides whether this
is a good theory or not – it’s nature. And if nature is showing this, this
would be quite remarkable. So this is where the efforts should be, I think.”