In 2011, three researchers won the Nobel Prize for discovering that the universe expands at an ever-increasing rate. Americans Saul Perlmutter and Adam Ries and Australian Brian Schmidt made the discovery, while studying type 1a supernovae, in the late 1990s. This is a type of supernova which occurs when a white dwarf star dies in a gigantic explosion.
The scientists were actually part of two teams, the Supernova Cosmology Project in the US and the High-Supernova Search Team in Australia. Both examined supernovas (supernovae) and in doing so, discovered the same thing—that the universe is expanding at an accelerating rate. They announced their findings within weeks of one another. How they found this out was that objects farther away from a supernova seemed to be moving faster than the event itself.
The edges of a supernova when observed from Earth, give off roughly the same amount of light as at its center. As a result, we can measure that distance. Subtle changes in the color of the light show how fast it’s moving. By observing different supernovae and more distant objects, astronomers can calculate their relative distance and speed.
If it all started with the Big Bang, shouldn’t things slow down over time? Several theories have been posited, including dark energy pushing the universe forward with an increasing speed. Since it’s been so hard to find or prove its existence, that theory has remained static. Up to 74% of the universe is supposedly comprised of dark energy, a force thought to repel gravity. In fact, dark energy has been called "the most profound problem" in modern physics. Some physicists today question whether it even exists at all.
Now, a PhD student has come up with a new theory that’s shaking things up. He and colleagues at the University of British Columbia suggest that the universe doesn’t expand in only one direction. Instead, time and space fluctuate in all different areas of the universe and they even oscillate, sometimes expanding and at other times, contracting.
Qingdi Wang is the PhD student who in trying to unravel this essential mystery of nature. In the same way, he’s also attempting to mend one of the major discrepancies in physics, the rift between quantum mechanics and general relativity. Wang and fellow PhD student Zhen Zhu worked together on the project, under the supervision of Professor Bill Unruh, a physicist and astronomer at the university.
Design Alex Mittelmann, Coldcreation [CC BY-SA 3.0], via Wikimedia Commons.
Wang and Zhu began by saying that if dark energy exists, it’s most likely expressed as vacuum energy. We usually think of a vacuum as empty space. According to quantum mechanics, there is a rather large density of energy inside a vacuum.
Overall, the universe expands at a very slow pace. Even so, the fact that it’s picking up speed is a serious issue that physics must address. Other theories have modified general relativity or quantum mechanics to fit with this phenomenon. But both work really well as they are. So Wang and Zhu decided to take a different approach. They suggest that the amount of energy density present in a large vacuum as explained by quantum mechanics is true.
Given that, they took that missing piece, vacuum energy and crafted the proper calculations necessary to express it. This newly established mathematical structure, when plugged into the whole, paints a far different picture of our universe than we’re accustomed to. Instead of moving outward at the same set rate of speed, originating from the Big Bang, the movement of the universe fluctuates from one point to the next.
The current cosmological model. NASA/WMAP Science Team.
"Space-time is not as static as it appears, it's constantly moving," Wang suggests. In some places it’s expanding while in others it’s contracting. This type of movement fluctuates but the two effects cancel each another out, almost. The end result is, the universe is still expanding, slowly, but in a way that picks up speed over time.
So if space is always moving, why don’t we notice it? According to Wang, "This happens at very tiny scales, billions and billions times smaller even than an electron." Prof. Unruh likened it to ocean waves. "They are not affected by the intense dance of the individual atoms that make up the water on which those waves ride," he said. So we’re part of an immense universal wave but we don’t even feel it.
To learn more about the universe’s expansion, click here: