SCIY.Org Archives

This is an archived material originally posted on sciy.org which is no longer active. The title, content, author, date of posting shown below, all are as per the sciy.org records
'Black-hole universe' might explain dark energy

Originally posted on sciy.org by Ron Anastasia on Mon 08 Oct 2007 01:00 AM PDT  

'Black-hole universe' might explain dark energy

  • 06 October 2007
  • NewScientist.com news service
  • Zeeya Merali

Imagine that we live inside a black hole. That could be the key to understanding the origin of dark energy, the mysterious force widely thought to be causing the expansion of the universe to accelerate.

Some physicists have previously suggested that dark energy could arise from the quantum bubbling of virtual particles in empty space, but it wasn't clear how. Now Jae-Weon Lee at the Korea Institute for Advanced Study in Seoul and his colleagues are proposing that dark energy is created as pairs of these virtual particles are ripped apart from each other by the expanding edge of our universe.

According to quantum theory, even the perfect vacuum of space isn't empty: it is a sea of virtual particles, created as entangled pairs of particles and antiparticles which exist only fleetingly and then annihilate each other.

Calculations also show that funny things can happen to these entangled virtual particles when they are near a black hole's event horizon - the boundary beyond which light cannot escape. If one member of a virtual pair crosses the event horizon before it can recombine, its partner will be converted to a real particle. So from the outside, the black hole would appear to radiate particles, a phenomenon known as Hawking radiation.

Lee's team don't seriously suggest that we live inside a black hole, but say that the portion of the universe that we can observe can be thought of in a similar way. Just as a black hole has an event horizon, our observable universe has a boundary known as the "cosmological horizon", which moves as the universe expands. Anything beyond this horizon is hidden because light from there has not had enough time to travel to us.

“Just as a black hole has an event horizon, our observable universe has a boundary known as the 'cosmological horizon'”

The team calculated the energy generated when entangled particles are wrenched apart by this "event horizon", and found that it matches the amount needed to explain the acceleration of the universe. "Dark energy is energy observed inside the spherical cosmological horizon," says Lee (Journal of Cosmology and Astroparticle Physics, DOI: 10.1088/1475-7516/2007/08/005).

Tomislav Prokopec, a cosmologist at Utrecht University in the Netherlands, finds the idea appealing. "They've come up with an interesting physical mechanism for how [virtual particles] could lead to dark energy," he notes. But he also points out that Lee's model depends closely on the highest energy associated with the virtual particles that contribute to dark energy. "They have chosen a very reasonable value for this, but if it turns out that this value is slightly wrong, it could throw off all their predictions," he says.

Seth Lloyd, an expert on entanglement at the Massachusetts Institute of Technology, is also impressed. "I think they could really be onto something," he says. Now he would like to know whether the model's predictions match detailed dark-energy measurements.

That could soon be possible. Lee and his team are using their model to predict how dark energy might affect imprints on the cosmic microwave background. This will be measured by the Planck satellite, due to launch next year. "Our model could be easily verified or ruled out soon," Lee says.

Cosmology - Keep up with the latest ideas in our special report.


From issue 2624 of New Scientist magazine, 06 October 2007, page 1

Attachment: