Mind-bending material properties
In January, a team of physicists from Rutgers and MIT published a paper in Nature describing a new property of matter. While fiddling around with a super-cooled Uranium compound, URu2Si2,
they found that it breaks something called double time-reversal
symmetry. Normal time-reversal symmetry states that the motion of
particles looks the same running back and forth in time: magnets break
that, though, because if you reverse time, the magnetic field they
produce reverses direction. You have to reverse time twice to get them
back to their original state.
This new material, though, breaks double
time-reversal symmetry. That means you need to reverse time four times
for the behaviour to get back to its original state. It's something the
scientists have dubbed hastatic order — and if you're struggling to get
your head round it, well, that's the appropriate reaction. The
scientists who discovered the phenomenon can't explain a good physical
example of what it is, how it works, or what it means. One to keep on
the back burner, then.
The universe weighs less than we thought
When
the world's best scientists decided to team up and measure the mass of
the universe all the way back in the 1970s, they set themselves a pretty
tall challenge. Applying their best understanding of gravity and the
dynamics of galaxies, though, they came up with an answer — an answer
which sadly predicts our universe should be falling apart. We know that the Universe's
galaxies' matter orbits a single central point — we've observed it! —
and that must mean their own motion generates enough centripetal force
to make that happen.
But
calculations suggest that there's not actually enough mass in the
galaxies to produce the forces required to keep themselves moving in the
way we've observed. So physicists scratched their heads, worried a
little, then proudly stated that there must be more stuff out there than
we can see. That's the theory behind what everyone now refers to as
Dark Matter. The only problem? In the past 40 years, nobody has
confirmed whether it really exists or not—so, effectively, the problem
thrown up by those initial calculations remains.
The placebo effect
Feed
a sick man a dummy pill that he thinks will cure him and, often, his
health will improve in a similar way to someone taking real drugs. In
other words, a bunch of nothing can improve your health. In theory, it
could be a powerful treatment technique.
But
experiments have shown that the kind of nothing you deliver matters:
when placebos are laced with a drug that blocks the effects of morphine,
for instance, the effect vanishes. While that proves that the placebo
effect is somehow biochemical—and not just a psychological effect—we
know practically nothing else about the power of placebo.
It's real,
sure. It can help people get better, agreed. But if we're ever to make
anything of the much-studied but little-understood effect, we're going
to have to unpick how the mind can affect the body's biochemistry—and,
right now, nobody knows.
Temperatures below absolute zero
It
used to be that scientists all agreed that it was impossible to achieve
temperatures below absolute zero. It was literally the coldest anything
could ever get. Late last year, though, a team of scientists from the
Max-Planck-Institute in Germany blew that out of the water:
finally, they'd cooled a cloud of gas atoms to below −273.15°C. In
fact, the result was as much a quirk of the definition of temperature as
anything else, and the way it relies on both energy and entropy (the
measure of disorder of particles). New Scientist explains:
In principle [it's] possible to keep heating the particles up, while driving their entropy down. Because this breaks the energy-entropy correlation, it marks the start of the negative temperature scale, where the distribution of energies is reversed – instead of most particles having a low energy and a few having a high, most have a high energy and just a few have a low energy.
It's this
curious logic that allowed the Max-Planck-Institute researchers to cool a
variety of atoms in a vacuum, for the first time ever, to below
absolute zero. So far, though, they haven't managed to work out what to
do with the chilled particles.
Cold fusion
Back in 1989, a pair of scientists—Fleischmann and Pons—claimed that they'd achieved a remarkable feat: they'd successfully observed nuclear fusion at room temperatures.
Momentarily, the finding was heralded as a revolutionary discovery that
could transform energy production around the globe. Sadly, their
experiments weren't reproducible—but they did inspire scientists to
study cold fusion in more depth.
Turns out, the process is in fact theoretically
possible. For two atoms two fuse together, they need to come close
enough to each other to overcome their mutual electric repulsion, which
is caused by the cloud of electrons that orbit them. Usually that's made
possible by super-high temperatures—like at the center of the sun—but
quantum physics suggests that, because the position of the electric
field causing the repulsion is probabilistic, there is at least the
possibility that atoms can fuse without the need for energy injection
via high temperatures.
And it's
that hope that means a small band of scientists still work in the
shadows, trying to get cold fusion to work. Of course, while occasional results come and go,
they tend to be rather dubious. Fundamentally that's because, even
though quantum theory tells us it should be possible, nobody knows how
to use that understanding to actually get a fusion reaction going.
Source: gizmodo
