Astronomy Buff

Edge of the Universe May Be Creating Dark Energy

by Tony on October 29th, 2007

In a paper that came out earlier in the August Journal of Cosmology and Astroparticle Physics, a group has suggested a really interesting source of dark energy.

For those who don’t know, most of our universe is made up of stuff that won’t have anything to do with us. Only 5% of the universe is made up of normal matter like protons, neutrons, electrons, etc.

We have no idea what the remaining 95% of the universe consists of, not in detail anyway. We have accounted for everything, we just don’t know what it’s made of.

Here’s a complete inventory of the universe:

• 5% normal matter. Protons, neutrons, electrons, everything we see and can interact with.
• 25% Dark matter. This is stuff made up of a cold, charge-less particle that whose existence we can only infer from it’s interactions with gravity and spacetime.
• 70% dark energy. This is what constitutes the majority of our universe. We only know it’s there because its existence best explains why we live in a flat universe and the fact that the universe is expanding and accelerating. In other words, that explanation best fits what we observe.

Most of you know by now that the universe is expanding. Well, that means there’s an edge, a “cosmological horizon” to our universe. It is at this horizon that the authors of the paper think dark energy is being created.

Here’s how:

It turns out empty space isn’t all that empty. Even in the perfect vacuum of space, there is a seething ocean of entangled particles and antiparticles being created and then almost instantaneously destroyed.

This all happens in a very short period of time, called the Planck time, that we have no hope of ever measuring it.

The particles literally come out of nowhere and then immediately recombine into oblivion. They always come in pairs and they always annihilate each other.

Well, almost always. If these particle/anitparticle pairs are created near very strong gravitational fields, like, say, a black hole, then one of the virtual particles can get sucked into the black hole before the pair can recombine. The remaining virtual particle will then be converted to a real particle in our universe and we literally have matter and energy coming out of nowhere.

When this happens near a black hole, it’s called Hawking radiation, black holes appear to radiate particles.

This new research suggests that something similar may be happening at the edge of the universe. As the universe gets bigger, the virtual particles created near the boundary are being pulled apart by the expansion, prevented from recombining when one particle passes the horizon.

The team found that the energy generated when entangled particles are wrenched apart by the edge of the universe, matches the amount needed to explain the acceleration of the universe.

Why would anyone ever want to do anything else besides cosmology?

Here’s a link to the full paper.

Technorati Tags: cosmology, dark energy, dark matter

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POSTED IN: cosmology