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What We Learned From a Bit of Space Dust

Earlier this year, a group of astrophysicists announced that they may have discovered the first evidence that would confirm the Big Bang theory, which is a proposed explanation about the origin of the universe. People have been researching and looking for proof of the Big Bang theory for decades, so the announcement got a lot of press and attention. However, it turns out that there may be a problem with the data. So, what did we learn from the whole experience? Were the experiments worthwhile, even if we didn't find the answers to our questions? What people don't always realize is that science is about asking questions, testing theories and making mistakes that force you to ask more questions. It's important to look, not only at the things we can prove and results that we can find, but also at how scientific methodology works.

So, what is the Big Bang theory?

To get a better understanding of the Big Bang theory, we need to go back almost a hundred years. In 1916, Albert Einstein presented his (now-famous) theory of general relativity. Relativity made Einstein a scientific rock star. The theory weaves space and time together into a single fabric called spacetime. Einstein showed that spacetime can be thought of as a fabric that curves or warps (to get a better idea of what Einstein meant watch the video below). Relativity theory also showed that there can be disturbances, or ripples, in this fabric that can move through spacetime. Physicists call these ripples, gravitational waves.

A few years later, astronomers discovered that the universe is expanding outward in all directions! Scientists theorized that if the universe is expanding outwardly, then a long time ago it must have started as a very small point in space. This starting point of our universe is called the Big Bang and it is believed that immediately after this occurred the universe underwent a massive expansion (called inflation) in a really, really short period of time (much, much, much less than a single second). Inflation gave a credible explanation as to why the universe is filled with what is known as Cosmic Microwave Background radiation (CMB). This radiation is a relic of the Big Bang and is somewhat smoothly distributed throughout the universe (there are some lumpy areas but that is a story for another time).

So, what is this possible discovery that the scientists made?

It turns out that when physicists combined the theories of general relativity and the Big Bang, it showed that there should be gravitational waves moving through the universe and, if there were, these would alter the CMB in very specific ways. With these waves in mind, physicists have been trying to take careful measurements of the CMB to see if they could detect these alterations. If they could match experimental measurements to the theoretical predictions, then we would have some of the first solid evidence of the Big Bang theory.

In March of 2014, a team of scientists from the Harvard-Smithsonian Center for Astrophysics announced that they had found such a match. The measurements of the CMB were collected using an instrument called the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization 2), which is located at the South Pole.    

However, within a few weeks of the announcement, a team of European researchers unveiled data from another instrument (the Planck telescope) that called into question the data measured by the BICEP2 team. When the BICEP2 team initially analyzed their data, they knew that their CMB measurements could have been affected by interstellar dust under the influence of magnetic fields, in space. Even though the BICEP2 team  took this space dust into consideration, the Planck telescope provided more accurate information about the dust. When teams re-analyzed the BICEP2 data using this new information, it appeared that the BICEP2 data may not have actually measured CMB radiation.

It is important to note that, while confidence in the initial findings has been considerably lowered, it doesn't mean that the BICEP2 data has been invalidated. In fact, what we are observing is scientific methodology at work. The BICEP2 scientists measured and analyzed their data in good faith according to the best information and methods they had. The Planck telescope team has now added new information and is working with the BICEP2 team to go back and re-analyze the data. What these teams will learn from this process will allow them to push ahead in further experiments. This is how good science is supposed to work and, for scientists, it's every bit as exciting as the initial findings!

If you would like to learn more about the work done by the BICEP2 team you can visit their homepage. However, my favorite explanation comes in cartoon form from the great site, PHD Comics. You can learn more about gravity by catching Science World's Locomotion show at the Peter Brown Family Centre Stage.