Physicists shed light on mysterious “dark universe”

1 July 2014 | Source: Physics World

In July’s special issue of Physics World, which is devoted to the “dark universe”, physicists from around the world describe some of the efforts currently being used to understand more about the mysterious dark energy and dark matter that, combined, make up 95% of the universe.

Physics World July 2014

In this month’s issue of Physics World…

Physicists shed light on mysterious “dark universe”

In July’s special issue of Physics World, which is devoted to the “dark universe”, physicists from around the world describe some of the efforts currently being used to understand more about the mysterious dark energy and dark matter that, combined, make up 95% of the universe.

Dark matter gets its name from the fact that it does not emit light, which subsequently makes it extremely difficult to observe and study. One of the strongest pieces of evidence pointing to the existence of dark matter is a phenomenon known as gravitational lensing.

As Catherine Heymans, a reader in astrophysics at the University of Edinburgh, explains, this occurs when light from distant galaxies is distorted on its journey to us via a vast network of dark matter, and physicists are exploiting this phenomenon to map the structure of this dark cosmic web.

Since dark matter is the dominant form of matter, it plays an incredibly important role in the formation of structures such as stars and planets. In this special issue, Tamara Davis, from the University of Queensland, describes how snapshots of the sound waves from the early universe, known as baryon acoustic oscillations (BAO), can help scientists characterise the nature and the amount of dark matter.

Davis also describes how the BAO can be used to probe the nature of dark energy, which is causing the expansion of the universe to accelerate. By comparing the BAO at two different ages of the universe, scientists can calculate by how much the universe grew over that period and therefore further their understanding of dark energy.

Jeff Forshaw, from the University of Manchester, takes a closer look at the properties of dark matter and gives an overview of the possible candidates of dark matter particles.

Forshaw also explains how these candidate particles can be detected, either by measuring the interaction of dark matter with ordinary matter, or using particle colliders such as the Large Hadron Collider (LHC) to detect the signs of two dark matter particles crashing together and annihilating each other.

Theorists believe the two main candidates for dark matter particles are the axion and weakly interacting massive particles (WIMPs), both of which are included in a special flow chart produced by Physics World that offers a guide to the many options of what dark matter could be.

In his opening editorial, Matin Durrani, editor of Physics World, writes: “The simple and sobering fact is that there is a huge chunk of our universe that remains waiting to be explored. After all, as we now know, ordinary matter makes up only 5% of everything – and look how long we have spent exploring its mysteries.”

Also in this issue:

  • End of the road? -- axe looms for European Science Foundation
  • Party trick -- how physics can get you out of an armlock
  • The bottom line -- meet the P&G physicist who's improving babies' nappies