Aliens, hamsters in tutus, and the nightmare scenario for particle physics
Could aliens be blocking the progress of human science? Well, that’s a science fiction plot, but it has some truth behind it…
In science fiction novel The Three-Body Problem, the alien Trisolarans send advanced AIs to block the progress of human science until their invasion fleet arrives. The AIs tamper with scientific experiments, such as using particle accelerators to search for the basic building blocks of matter, space and time. Physicists get random results. Believing that the laws of physics vary from place-to-place, they are driven to insanity and suicide.
The Three-Body Problem is fiction, but the plot is truer than it may seem. In 2010, the Large Hadron Collider, the world’s most powerful particle accelerator, ran its first experiments. Nearly seven years later, scientists are still awaiting clues to a ‘new physics’ that promises to unlock mysteries of how the universe began and what it is made of.
When particles smash together and break apart, they allow scientists to test their theories for how the tiniest particles that make up the universe behave. This allowed scientists to, among other things, discover a new particle called the Higgs Boson in 2012.
A grand unified theory of almost everything
The Higgs Boson was predicted by the Standard Model of particle physics. This simple theory, finalised in the mid-1970s, explains how the basic building blocks of matter interact with a handful of fundamental particles. It explains much of what the universe is made of and what holds it together.
Unfortunately, the Standard Model leaves many mysteries unexplained. For example, it doesn’t explain dark matter, the invisible unidentified material that makes up about 26% of the mass and energy of the universe. For this reason, it’s been described as a ‘grand unified theory of ALMOST everything’.
The jargon-quantum physics bit
One big thing the Standard Model doesn’t explain is the difference in strength between gravity and the so-called weak nuclear force, which is responsible for radioactive decay (radioactivity, in other words. Like in a nuke).
Now here’s the geeky bit…
In the Standard Model, the weak nuclear force is carried by particles called W and Z bosons. These get their mass from an invisible Higgs field that spreads through the whole of space. The question is why the Higgs field – and weak nuclear force – isn’t stronger. During events called ‘quantum fluctuations’, energy should spill into the Higgs field, increasing its strength, the mass of the W and Z bosons, and the weak nuclear force.
An elegant symmetry
Supersymmetry is an elegant theory that explains dark matter and the disparity between gravity and the weak nuclear force. The idea is that every basic particle has a ‘superpartner’ of an opposite type. Fermions, the particles that make up matter, have boson superpartners that carry forces, and vice versa. As these have opposite signs of energy, one type dials down the energy contributed to the Higgs field, and the other dials it up. As an added benefit, the superpartners could make up dark matter.
To date, the Large Hadron Collider hasn’t found superpartners. To evade detection, and fit the theory, the superpartners must have higher energies than the LHC can produce. Higher energies mean the superpartners must be much heavier than their partners. This makes it harder to cancel their contributions to the Higgs field. Supersymmetry theory has become less elegant as a result.
“The first thing, which would worry a lot of my colleagues in particle physics, would be the end of particle physics,” he says. “If the Large Hadron Collider doesn’t find anything interesting then any future collider would already be in doubt.”
More broadly, physicists would need to reexamine some of their assumptions. For example, they might need to find new candidates for the particles making up dark matter. Or even alternative theories to dark matter itself. Some explanations, such as modified gravity, could get science fictional, he says.
Getting science fictional
According to Clements, reexamining supersymmetry could change our understanding of the early universe – with implications for science fiction writers. The leading candidate for dark matter has long been ‘cold’ dark matter (CDM).
CDM is a type of dark matter that moves slower than the speed of light and only weakly interacts with other matter. Scientists believe CDM is some kind of exotic particle yet to be detected. It was probably around near the beginning of the universe and affected how galaxies grew.
“If dark matter isn’t CDM then the early evolution of the universe could be different and we must have been fooling ourselves into thinking we have it as right as we do,” he says, although he thinks this is unlikely. If that is the case, hard sci-fi writers might have a scientific loophole to include Faster Than Light travel.
Another possibility is an Alcubierre drive, where a spacecraft moves at light speed by contracting space ahead of it, and expanding space behind it. This needs exotic particles, but might be plausible if new theories are up for grabs.
The REAL Three-Body Problem
I asked Clements whether scientists might discover the laws of physics change over space and time – as happens in The Three-Body Problem.
“Variations in basic laws with time is something some people have looked at,” he says. The Euclid mission, currently under development by the European Space Agency, aims to see if the density of dark energy has changed over time.
“Link this in with the problems with dark matter and the Standard Model and it might be that time-varying physical laws might have to be invoked,” he says.
A more radical possibility is the simulation hypothesis. This argues that what we think is reality is actually a giant computer simulation created by a greater intelligence. According to Clements, “If we’re in a simulation the laws of physics don’t have to be consistent or coherent.”
A darker possibility
There are other possibilities for why the Large Hadron Collider hasn’t found anything yet, of course. In Three Worlds Collide by Elizer Yudokwsky, physicists hide important laws of physics after discovering a terrible secret:
“Aren’t we lucky that physics didn’t happen to turn out that way, my lord? That in our own time, the laws of physics don’t permit cheap, irresistable superweapons?”
Akon furrowed his brow –
“But my lord,” said the Ship’s Confessor, “do we really know what we think we know? What different evidence would we see, if things were otherwise? After all – if you happened to be a physicist, and you happened to notice an easy way to wreak enormous destruction using off-the-shelf hardware – would you run out and tell you?”
“No,” Akon said. A sinking feeling was dawning in the pit of his stomach. “You would try to conceal the discovery, and create a cover story that discouraged anyone else from looking there.”