Challenging the orthodoxy in dark matter, dark energy, fusion and more

Australian Institute of Physics, Australian Institute of Physics Congress, Media releases

Good science happens when clever people ask insightful questions. Some papers at the national physics congress in Canberra last week took on their colleagues—asking penetrating questions of mainstream science.

Defence against the dark parts

In theory, dark matter and dark energy together comprise 95 per cent of the Universe. But no-one’s ever seen them. No-one’s quite sure what they’re made of, nor how they work. Do they exist at all?

The textbooks say they must exist—to account for observations such as the rapid spin of the outer reaches of our galaxy and the accelerating expansion of the Universe. But ‘inventing’ something to fix the equations makes some physicists nervous. And there are other theories that also explain these observed phenomena—without the need for dark matter and dark energy.

A handful of physicists at the national physics congress in Canberra last week favour other explanations of the basic building blocks of the Universe:

What if space itself expanded more in areas of higher matter density, and less elsewhere. This fairly simple starting assumption has some startling results: the speed of light for example—constant in an area with a given matter density (such as in the region of our own Solar System)—would effectively slow down in regions where matter is less dense. In the outer Galaxy, the reduced density of stars and resulting slower speed of light would make it appear that stars moved faster out there. Physicist Peter Lamb, of Deakin University, explains that the model similarly accounts for the other ‘requirements’ that persuaded physicists we needed dark matter and dark energy, while accounting for missing antimatter, and reconciling quantum mechanics with general relativity.

Too many particles

Do we really need the 17 proposed fundamental elementary particles of the ‘standard model’? Vivian Robinson says we might only need one: our universe could be made up of many different orientations of just one particle—the simple photon—moving either in straight lines as energy, or spinning in tight circles as matter. Vivian’s theory fits measurements for atomic and nuclear structure, the lack of dark energy in our galaxy, and relativity without requiring 17 fundamental particles.

Are we heading down the wrong path for a fusion future

The fuel used by most fusion energy researchers is a mix of deuterium-tritium, two isotopes of hydrogen. To ignite, this mix requires very high temperatures (around 100 million degrees C) and massive compression, achieved using very strong magnetic fields, which also confine the reaction once underway. During the reaction, short-term neutron radiation poses operational issues , and tritium waste remains radioactive for a number of decades.

Heinrich Hora is working on something quite different. He proposes to use a different (proton-boron) fuel, which can be directly ignited using short-burst lasers to accelerate plasma blocks. This alternative fusion method, recognised since the 1970s, had been discounted by most researchers because of the high energies needed to ignite the fuel, and higher magnetic fields needed to contain the reaction. But recent developments in both short-pulse, high-power lasers and generation of ultra-strong magnetic fields have now made it feasible. Compared with the deuterium-tritium method, it would promise elimination of dangerous short-term neutron radiation, no hazardous tritium to dispose of, lower energy required to initiate the reaction, and cheaper construction costs. Because it uses already-proven technology, it could be a far faster route to commercial fusion energy than is being pursued elsewhere, with commercial fusion possibly available in ten years. Steven Haan, an expert in nuclear fusion at Lawrence Livermore National Laboratory in California, has called block ignition “the fastest route to fusion energy”.

You want how many dimensions?

Even the physics Congress’s plenary guests don’t always agree. Like most cosmologists, Lisa Randall thinks the Universe requires eleven space-time dimensions—or perhaps ten. But Lawrence Krauss says any theory that requires that many dimensions to work properly is probably too complicated to be true. Lisa Randall speaks in Sydney tonight.