As a guest selector this year Gill Arbuthnott created a series of events about the importance of communicating science. Christophe Galfard worked with Stephen Hawking and wrote children’s books with Lucy and Stephen Hawking and now he has written a book explaining the journey and the mechanics of the universe.
Galfard stands, saying he will take us on a journey. He begins with the Milky Way, showing an image of the complete galaxy as seen from Earth, cobbled together from pictures taken around the world. Then comes an (artificial) image of the entire galaxy from above and he explains that Earth is not at the centre but out along one of the twisting arms, relatively near the edge. The analogy of a phone call is used to explain the distances involved. If you are on the moon there is a delay of 1 second. If you called someone on the sun it would take around 8 minutes and 30 seconds for your words to reach them. If they were on the nearest star it would take 4 years. At the centre of the galaxy 40,000 years. The position from which the simulated image could be taken? 90,000 years. The biggest nearby galaxy is 2 million light years away.
He then explains that when a star dies and explodes you get a nebula. A picture appears of an enormous nebula filled with the dust of 100,000 dead stars. Then it zooms in to a feature known as the Pillars of Creation. Galfard explains that the temperature at the centre will be 50-60 million °C and new stars are being born. Looking at the birth and death of stars allows us to look into our own history, and to work out how far away galaxies are. The death of a star releases a specific pattern that expands and so the distance can be calculated.
There are thousands of galaxies and while often a picture from the Hubble telescope will contain stars from the Milky Way there are points where the magnification is so great that nothing from our galaxy is seen and every shining dot is an entire galaxy. He demonstrates the sheer volume of them by displaying an animation of the 400,000 galaxies closest to us. It’s a breath-taking moment that provides an intense perspective of how small our little world really is and just how much is out there.
Galfard explains that frequently the telescope will focus on what appears to be a black patch in space and then it will find 100s more galaxies. The odd thing is that what we are able to see is in the past. If a galaxy is 3 million light years away then the image we see is that galaxy as it was 3 million years ago and plenty of these galaxies are billions of light years away. Physics suggests that a long time ago the universe was much smaller and so dense that no light could travel through it. It was predicted that we would be able to see the wall from that dense history and that it would be -270 °C. If you zoom in far enough (essentially peering into the past) you can see that wall at the edge of the visible universe and it is indeed -270 °C.
When he sits once more Arbuthnott asks the inevitable question: are we alone? Galfard thinks there must be life somewhere else, though there is currently no proof and then jokes that Hawking once said there was little sign of intelligent life on Earth. He then quotes Sagan, more seriously, saying that if it’s just us it seems like an awful waste of space. Galfard points out that people have wondered about other worlds for thousands of years, at some points in history people were burned for speaking of the possibility. 20 years ago we found the first evidence of a planet outside our solar system. Now there are 6,000. 11 of these are fairly Earth-like and 2 are very similar to Earth. Who knows what we will find in the next decades and centuries.
Discussion and questions keep bringing up new facets of what we know about the universe and the theories that surround it. The explosions of stars are violent but silent, as sound cannot travel in space. When we leave the realm of what our sense can detect the rules of nature begin to change. What we are able to see is only the visible universe, there seems to be a great deal more and we might never be able to fully fill in the edges of the map.
It was a fascinating hour and it became clear that the theories we work with now are the best we currently have but there are occasions where they don’t work. There could be immense revelations hidden in those problems and what we know in 6,000 years time will likely be quite different to what we know now.