Moment that mattered: A new way of looking at the universe
“In order to understand the details of cosmic evolution you need to have amassed a great data set so you can see stars at various points in their stellar evolutions, and galaxies in their galactic evolutions. The Sloan Digital Sky Survey is the most refined and powerful set of data of that sort – it would take half a million high-definition TVs to view at its full resolution – and we now have it at our disposal.
The new image the survey has produced represents a grand opportunity to refine our understanding of the full extent of cosmic history. It’s a kind of time machine. When you look at it, you need to bear in mind that the further away something is the longer it has taken for its light to reach you; for something very far away, the light your camera is receiving has been travelling for millions or maybe billions of years. So any single pinpoint of light you see in this picture could be a record of how things were billions of years ago – a cosmic message that has been travelling for all that time.
When you recognise that some of these pinpoints of light are themselves galaxies, which themselves have hundreds of billions of stars inside of them, I think that can inspire a grandeur that is hard to capture in words.
A feature of the universe that I wish people grasped more fully is that on different scales the universe has a different appearance. When you are looking at it on the scale of the solar system, the planets are the vital elements, and they are majestic and beautiful – and if you pull back further you see the solar system as part of a galaxy, our galaxy. But if you pull back further still and you see our galaxy as one of hundreds of billions of galaxies – which is more the scale you are seeing in the Sloan Digital Sky Survey’s image – then there is a different sense of awe which that image instils in you. And I think a full appreciation of the cosmos requires that you be able to imagine on all of these scales – to flick through the photos that show our universe in all of its richness, from planets to stars to galaxies to clusters of galaxies. That’s the beauty of it all.
We theorists try to use mathematics to describe the universe, and it’s these kinds of observations which straitjacket the maths – which tell us which mathematics is giving us insights into the origin and the evolution of the universe, and which can be culled because it doesn’t match the data. For example, in 1998 it was observed that the expansion of the universe is accelerating – not only are other galaxies moving away from us (a fact we have known about since 1929, following Edwin Hubble’s observations of the night sky), but that they are moving away from us increasingly quickly. It’s as if someone put their foot on the gas pedal, forcing space to rev up and expand ever more rapidly. That discovery was a shock we are still reeling from – and it forced us to rethink much of the detailed nature of cosmic history. The data that are in these new images will help us to refine our understanding of that accelerated expansion, of the dark energy we think is pushing the universe apart.
I think this image has the power to give a feel for what the totality of reality is like. It can make you feel very small. But at the same time that can be deeply inspiring, because you recognise that, even though we are so small, we have been able to figure out so much. We understand the universe way back to a fraction of a second after the beginning, and we understand the grand sweep of space, as depicted in this image – and that’s wondrous.”
Brian Greene is a theoretical physicist, string theorist, professor and writer. His latest book, The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, is published by Knopf.
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