Back in 1929, Edwin Hubble discovered that the universe is expanding. All galaxies, including our own Milky Way, are slowly moving away from one another. The speed of their movement is dictated by their distances. From our perspective, galaxies that are farther away are moving at a greater speed than those closer to us. But that’s not to say we’re the center of the universe. Every galaxy experiences the same principal regardless of its location. This is known as the Hubble Law.
A great example for demonstrating this law is to take a deflated balloon and draw dots on it. The balloon represents the universe and the dots, galaxies. As you inflate the balloon, its covering stretches and every dot moves away from the others uniformly, with dots that are farther apart moving more rapidly from one another. Recently, physicists have discovered that all galaxies are moving away from each other at a faster pace than we originally thought by about five to nine percent.
A group of physicists led by 2011 Nobel Prize winner Adam Reiss, made this discovery using a device named after Edwin Hubble himself, the Hubble telescope. This team of physicists used the telescope to measure the distances of 19 galaxies beyond the Milky Way. They did this by focusing on a specific type of star known as Cepheid variables. These stars have a regular cycle of brightness with a frequency related to its luminosity which allows scientists to estimate their distances from Earth. The physicists eventually realized their measurements did not meet up with expectations. “You start at two ends, and you expect to meet in the middle if all of your drawings are right and your measurements are right,” Reiss said in a press release. “But now the ends are not quite meeting in the middle and we want to know why.”
There are three reasons that may account for the discrepancy. The first is that dark energy may be pushing galaxies away from each other with ever increasing power. Dark energy is a theoretical force that scientists believe constitutes about 70 percent of the cosmos. Another reason may be that dark radiation particles, which travel close to the speed of light, could be throwing off their predictions. Finally, dark matter (the opposite of dark energy which acts as an attractive force) may have some unknown characteristics that account for the miscalculations. “This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95 percent of everything and don’t emit light, such as dark energy, dark matter, and dark radiation,” Riess said.
The discovery by Reiss and his team not only points out that our collective home is growing faster than we thought, but also may raise the possibility that Einstein’s general theory of relativity may be slightly off. But this wouldn’t be the first time the speed of the universe has been recalculated. When the Hubble telescope was first launched in 1990, scientific estimates about the rate of galactic recession varied by a factor of two, but improved measurements narrowed that gap considerably. So to recalculate this variable by five to nine percent shows science is narrowing in on an accurate model of universal expansion.