We know something about the universe.
I know that sounds mundane, but it is one of the most profound statements we can make. Many species on this planet are intelligent and aware of their surroundings, but I think it's safe to say that they don't ponder the greater Universe around them.
We do.
We know a lot about it. We know how stars form and how they die. We know that planets form around those stars, and have a good grasp of how that works. We know that moons form around planets, and that they come from the gas and dust in the nebulae. All of these things happen in the stars.
Yes, the universe. The immense stellar cities are one of the fundamental building blocks of structure in the Universe.
We see a spectacle when we look at ones that are close by.
It's NGC 691.
Wow. The stars, gas, and dust of the spiral galaxy are forming a pinwheel pattern. The arms are blue because the nucleus is made up of older stars, and massive stars are blue and bright. More red stars are born there, but they are so faint that we can't see them.
This is normal for a spiral galaxy. The light from an exploding star that reached us in 2005 is what makes NGC 691 special, and worthy of observing with precious time on Hubble Space Telescope. It was a type Ia supernova, and it was called SN 2005W. The amount of energy released by these kinds of explosions is the same over time. Their distance can be gauged from how bright they are.
The redshift can be used to measure the distance to the galaxy. The supernovae were dimmer than their host galaxy's redshift would indicate, thanks to the two methods used by the two teams of astronomer. The expansion of the Universe was accelerated because this implied they were farther away than the simple redshift measured.
We discovered dark energy by doing that.
The acceleration is very small at close distances, and only picks up for a very long time. There are several methods used to measure how fast the Universe expands, and they don't all agree. One number is given to those who look at objects that are less than a billion light years away, but another number is given to those who use extremely distant sources. The tension between the two methods is not easy to explain.
It was observed in the first place. It's close enough that several of the distance measurements can be used, and compared to one another to try to tighten them up. When I first saw the image, I had to laugh because it was taken by my friend and colleague Adam Riess, who was on the team that discovered dark energy and was able to correlate the distances of Type Ia supernovae.
I chuckled when I saw his name after seeing the faded image of this galaxy. It's an amazing thing.
This brings me back to my point. We know a lot about the Universe and how it works. We don't know everything.
Absolutely not! That's why science exists. It's a method of knowing.
We don't know how dark energy works, what dark matter is, or how Type Ia supernovae explode. We know some of the basics of how they work. Even though we have methods of studying them, we still look at them and try to refine them so we understand better.
One of my favorite things about science is that it can be used to improve our understanding.
I think reflecting on this year's events is important as we start another. I think it's important that we learn more about how science works, because science plays an outsized role in our lives every day.
I hope that more people take the time to learn why science is such a great way to know the Universe. We're a part of the Universe and so we have to know ourselves. We can all strive to do that better.
