So time only moves
forward—or does it? Physicists usually refer to this idea as the “arrow of
time,” and the idea of unidirectional time seems to hold true for life and
objects on a human scale. But on a quantum scale, things seem to work very
differently, even strangely.
For physicists, the arrow of
time is dictated by the second law of thermodynamics, which says that disorder
(or entropy) increases over time. The transfer of heat is a perfect example of
this. On a chilly day, you’d expect your coffee to get colder if the air around
it is cooler. Heat scatters in the presence of lower temperatures; it doesn’t
concentrate.
But a new experiment shows
that, unlike heat dissipating from your coffee cup on a cold day, quantum
particles can transfer heat energy away from cold particles and toward hotter
ones, a reversal of the second law. If the second law can be reversed in that way,
then it’s entirely possible that the arrow of time can be reversed, too.
Theoretical physicists had
already predicted this could happen, but now we have proof that it’s possible.
Here’s Emily Conover,
reporting for Science News:
The new result, however,
“shows that the arrow of time is not an absolute concept, but a relative
concept,” says study coauthor Eric Lutz, a theoretical physicist at the
University of Erlangen-Nürnberg in Germany. Different systems can have arrows
of time that point in different directions, Lutz says. While the arrow was
apparently reversed for the two quantum particles the researchers studied, for
example, the arrow pointed in its typical direction in the rest of the
laboratory.
Reversing the arrow of time
was possible for the quantum particles because they were correlated—their
properties were linked in a way that isn’t possible for larger objects, a
relationship akin to quantum entanglement but not as strong. This correlation
means that the particles share some information. In thermodynamics, information
has physical significance.
“There’s order in the form
of correlations,” says physicist David Jennings of the University of Oxford,
who was not involved with the research. “This order is like fuel” that can be
consumed to drive heat to flow in reverse.
In the experiment, the
researchers manipulated chloroform molecules (made of carbon, hydrogen, and
chlorine atoms) so that the temperature of the hydrogen nucleus was greater
than the carbon nucleus. In quantum terms, temperature refers to the
probability of the atom’s nucleus being in a certain energy state. “When the
two nuclei’s energy states were uncorrelated, the heat flowed as normal, from
hot hydrogen to cold carbon,” Conover writes. “But when the two nuclei had
strong enough quantum correlations, heat flowed backward, making the hot
nucleus hotter and the cold nucleus colder.”
The main virtue of the
experiment is that it illustrates an example of a system in which the arrow of
time is not we see it to be in most other conditions. That doesn’t mean that
time was running backwards. But what the scientists saw happen between the two
particles over time was the opposite of what you or I can expect in our
ordinary lives. It’s a nice confirmation of a theory physicists proposed years
ago.
Via PBS.org
That's how broken finance works - the rich get richer by taking from the poor - it's a backwards arrow...
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