Dark matter might be
made of super-heavy particles almost as big as human cells
Usually, when a new particle is discovered or
its existence hypothesised, it's on such a tiny scale that it's hard for us to
imagine. But that might not be the case with dark matter, because researchers
have found evidence to suggest that these mysterious, invisible particles could
be about one-third the size of a human cell, and dense enough to almost create
a mini black hole.
Though they reportedly make
up five-sixths of all of the matter in the Universe, no one
truly knows what dark matter is, how it works, or even what it could look like.
Despite its mysterious nature, scientists hypothesise that dark matter has to
exist in some form to account for the amount of mass needed for the Universe to
exist and act in the way it does.
Knowing this, researchers from the University
of Southern Denmark decided to investigate the size of these hypothetical
hidden particles. According to the team, dark matter could weigh
more than 10 billion billion (10^9) times more than a proton.
If this is true, a single dark matter particle
could weigh about 1 microgram, which is about one-third the mass of a human
cell (a typical human cell weighs about 3.5 micrograms), and right under the
threshold for a particle to become a black hole.
The researchers came up with this number by
creating a new model for a super-heavy particle they call the PIDM particle
(Planckian Interacting Dark Matter). These supermassive particles belong
to a class of particles known as 'weakly interacting massive particles', or
WIMPS.
Before now, researchers have suggested that
WIMPs were about 100 times the mass of a proton, Charles Q. Choi reports for LiveScience, but
while the existence of WIMPS has been hypothesied for years, evidence of them
is, well, extremely lacking, like everything else about dark matter. This
leaves open the possibility that dark matter particles could be made of
something significantly different, says Choi.
If the team from Denmark is right about the
size of dark matter particles, it means dark matter is too large for
researchers to recreate with particle accelerators. Instead, evidence of dark
matter might exist in the Universe’s cosmic microwave background radiation,
which is basically the light left around from the Big Bang.
In short, when the Big Bang happened 13.8
billion years ago, the Universe grew rapidly, a time period researchers call
'inflation'. The next stage on the Universe’s development chart is called
reheating, which, among many things, created particles. It's here, during
reheating, that supermassive dark matter particles might have first formed.
"However, for this model to work, the
heat during reheating would have had to be significantly higher than what is
typically assumed in Universal models," says Choi. "A hotter reheating would in
turn leave a signature in the cosmic microwave background radiation that the
next generation of cosmic microwave background experiments could detect."
Obviously, if we do eventually observe direct
evidence of dark matter, it would solidify many hypotheses about how the
Universe works and initially formed. However, before that happens, we need
better tools, which University of Southern Denmark cosmologist, McCullen
Sandora, says we should have within the next decade.
Until then, we can only speculate how dark
matter works and how it fits into longstanding hypotheses and models.
You can view the team’s
report in Physical Review Letters.