Approximately 100 years ago, astronomer Edwin Hubble discovered that galaxies are generally moving away from each other, like raisins in an expanding cake. This led to the “Big Bang” theory that suggests that the early Universe was hot and dense and has been expanding ever since. It was expected that the mutual gravitational pulls amongst the galaxies would slow down the expansion of the Universe. However, in 1998, it was discovered that the Universe is in fact accelerating! Although not well understood, the source of the acceleration could be a “dark energy” filling the Universe – a subject of active astronomical study. One possibility is that the acceleration is caused by a fifth force of nature, called “quintessence”, associated with particles we have yet to discover. Stay tuned!
