Episode #10 of the course “Strangest Things in Space”
Vacuum energy is the odds-on-favorite to be the mysterious dark energy that accounts for a staggering 68% of the universe. In essence, it is free-flowing energy within the fabric of space-time. To best understand vacuum energy, first think of the concept of free energy, which is something we should all be familiar with. Free energy is simply energy we harness from sources like the sun with solar panels or the wind from windmills. Vacuum energy is also free energy, but it is more abundant than those other forms of free energy. Vacuum energy is essentially infinite.
When we think about how the universe is constantly expanding and that the major portion of the universe is dark energy, this makes sense. As two polar-charged particles—matter and antimatter for example—are created, they inevitably collide and destroy each other in the process. The energy released from this explosion is pushing the universe outward. This energy could be vacuum energy.
Another appealing element of vacuum energy is that it could explain why the universe has only started accelerating at the rate it has fairly recently on the cosmic timescale. The early universe was smaller, with less space between galaxies. Because of this, gravity played a more prominent role in holding everything together and slowing down the acceleration of the universe.
The theory of vacuum energy is not without problems, however. It alone should be far too weak to account for the acceleration seen in the present-day universe. Still, it is the most complete scenario scientists have to date.
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