– Some years ago, astronomers discovered that our universe is expanding at an ever-increasing rate, implying that space is not empty, but instead filled with dark energy that pushes matter away.
The Universe expands very slowly, and scientists are trying to determine what mysterious force is behind this process. Solving this riddle, can shed light on the fate of the universe.
The expanding universe is finite in both time and space. The reason that the universe did not collapse is because it has been from the moment of its creation. The American astronomer Edwin Hubble made the observations in 1925 and was the first to prove that the universe is expanding. He proved that there is a direct relationship between the speeds of distant galaxies and their distances from Earth. This is now known as Hubble’s Law.
So, what is the fate for an expanding universe? Will it go on forever or is there a limit to the expansion?
Actually, by measuring how fast the universe expands relative to how much matter the universe contains, it possible to understand the fate of the universe.
An expanding universe can be of three types, open, flat and closed. An open Universe would never cease to expand. A flat universe would also expand forever, but at a slower rate. A closed universe will eventually stop to expand and collapse. This could result in another Big Bang.
Now, that we know that our universe is expanding, next step is to try and determine what causes the expansion. It has long been assumed that the force behind the expansion is gravity, but it the etire process be much more complicated than we have previously thought?
A group of scientists from the University of British Columbia are now trying to solve one of the greatest mysteries in nature – what causes the accelerating expansion of our universe?
In a new study, PhD student Qingdi Wang, is attempting to a major incompatibility issue between two of the most successful theories that explain how our universe works: quantum mechanics and Einstein’s theory of general relativity.
The study suggests that if we zoomed in-way in-on the universe, we would realize it’s made up of constantly fluctuating space and time.
“Space-time is not as static as it appears, it’s constantly moving,” said Wang.
“This is a new idea in a field where there hasn’t been a lot of new ideas that try to address this issue,” said Bill Unruh, a physics and astronomy professor who supervised Wang’s work.
The most natural candidate for dark energy is vacuum energy. When physicists apply the theory of quantum mechanics to vacuum energy, it predicts that there would be an incredibly large density of vacuum energy, far more than the total energy of all the particles in the universe.
If this is true, Einstein’s theory of general relativity suggests that the energy would have a strong gravitational effect and most physicists think this would cause the universe to explode.
Unlike other scientists who have tried to modify the theories of quantum mechanics or general relativity to resolve the issue, Wang and his colleagues Unruh and Zhen Zhu, also a UBC PhD student, suggest a different approach. They take the large density of vacuum energy predicted by quantum mechanics seriously and find that there is important information about vacuum energy that was missing in previous calculations.
Their calculations provide a completely different physical picture of the universe. In this new picture, the space we live in is fluctuating wildly. At each point, it oscillates between expansion and contraction. As it swings back and forth, the two almost cancel each other but a very small net effect drives the universe to expand slowly at an accelerating rate.
But if space and time are fluctuating, why can’t we feel it?
“This happens at very tiny scales, billions and billions times smaller even than an electron,” said Wang.