Ancient Galaxies and Even Older Dark Matter

We tell each other stories to make sense of our lives. That’s how humans communicate. It’s the same in every culture. The most common stories that people tell are creation stories. People believe that creation stories contain profound meanings, even though story tellers don’t always mean them literally. Creation stories have recurring themes. The world may be created out of chaos, by a diver who brings soil up from the sea bed, by emerging from some earlier state, by childbirth or from nothing at all.

Most creation stories are cosmological, meaning that they explain how and why the world is ordered and what our place is in that order. In our modern culture, we still tell stories. The difference is that we tell them using science. We expect our stories to be based on facts and evidence. Our creation story is called the Big Bang, and it’s based on our observations of the universe. Readers, and viewers of the American sitcom The Big Bang Theory, will be aware that “Our whole universe was in a hot dense state, when nearly 14 billion years ago, expansion started. Wait!”

How do we know that the universe had a beginning, and that it started all at once? Science has three main pieces of evidence. First, everything in the universe is moving away from everything else. Logically, if we think in reverse, everything must have all been in one place at some point. Second, no matter where we point a radio telescope, we receive microwave signals in the background. This is called the Cosmic Microwave Background. This faint radiation is a remnant of the Big Bang explosion. Third, if the universe had always existed, the light from an unimaginable number of distant stars would have had time to reach us by now. The night sky wouldn’t be dark.

Another story that science is trying to tell is about something called dark matter. We would explain what dark matter is to you if we could, but nobody knows. For a long time, whenever scientists have studied the way galaxies behave, they see far more gravity at work than we can account for. Franz Zwicky, for example, was studying galaxy clusters and found that they contained for less observable mass than what is needed to hold them together. He called this the “missing mass” or “dark matter”.

Nobody can explain what dark matter is, but based on the way galaxies behave, we know that it must make up about 80% of the matter in the universe. In the past week, there have been two new discoveries about dark matter. The first comes from the University of Tokyo.

Combining observatories on earth and in space, researchers there have discovered 39 ancient massive galaxies. Scientists have been unable to detect them until now because they are so far away that the light from them has shifted out of the visible spectrum and into infrared. Scientists believe that finding these enormous and primordial galaxies will increase our understanding of black holes and of the mysterious dark matter than seems to hold galaxies together.

The second discovery is more mind-blowing. Scientists at Johns Hopkins University are now suggesting that dark matter may have existed before the Big Bang. Readers may have heard that nothing existed before the Big Bang. The idea has been that dark matter is a residue from the primordial explosion. If this were true, though, scientists should have found the particles that make up dark matter. As we discussed in an earlier post, nobody has found even a trace of dark matter particles.

This study casts that idea into doubt. Scientists believe that dark matter consists of some sort of particle that we haven’t discovered yet. Readers may have heard of the Higgs Boson. It’s known as a scalar particle. The researchers at Johns Hopkins believe that dark matter may also consist of another form of scalar particle.

The reason scientists believe that dark matter exists is that its gravity influences the formation and distribution of galaxies. Whatever dark matter is, nobody has actually detected it. If it’s true that dark matter consists of scalar particles that existed before the Big Bang, scientists may be able to use this knowledge to better explain what dark matter is, and also to tell us what, if anything, happened before the Big Bang. We need our creation stories. This age of reason has robbed us of the ones we had. Science has lifted us onto what Newton called “the shoulders of giants”. We can see further than our ancestors, and we can be supremely confident that our beliefs are justified. The trouble is, our new creation story is incomplete. We know what galaxies are, but we can’t explain why they form, how they get distributed, or what holds them together. It’s not a satisfying story to tell without filling in these details.

The good news is that these researchers at the University of Tokyo and at Johns Hopkins University are moving us closer to understanding the origin and fate of our universe.

There is always more to learn if we dare to know.

Learn More:
University of Tokyo
A dominant population of optically invisible massive galaxies in the earlyUniverse
Johns Hopkins University
Dark Matter from Scalar Field Fluctuations