Astronomers probe the history of the cosmos
The universe. (NASA image)
This is the deepest view of the universe ever seen by humans, called the Hubble Ultra Deep Field. Scientists estimate the universe to be about 13.7 billion years old, and they think these images capture some of the first galaxies to be created, less than a billion years after the Big Bang. Pictured are over 10,000 infant galaxies located in the direction of the constellation Fornax, below Orion, and the exposure time required the Hubble Space Telescope to complete over 400 orbits around the Earth.
Astronomers believe our universe began in a Big Bang nearly 14 billion years ago.
They believe our universe started off very hot and very dense, but in a sense very simple. Simple . . . because, after the initial Big Bang, the universe is thought to have expanded in a uniform way. For a short time on a cosmic scale, perhaps 200 million years, every part of the universe was like every other part.
But, as the universe continued to expand, differences in densities emerged – and those little differences are what enabled stars and galaxies to come into being. Earth & Sky spoke about the early universe with Martin Rees, professor of cosmology and astrophysics at Cambridge University in Cambridge, England.
Martin Rees: now we can see galaxies so far back that we’re almost certainly seeing, as it were, embryonic galaxies, galaxies which are just about 1 billion years old, which is less than 10% of their present age. So we’re really getting a snapshot, as it were, of all the stages in the evolution of a galaxy — from its formation from the first primordial clouds that condense out under gravity, to the present structures that we see around us, and of which we are a part in our own Milky Way.
Martin Rees also said: We’ve made immense progress in cosmology in the last few years, but this progress has brought into focus a new set of mysteries that we never envisioned before. We’ve learned about what the universe is made of, but that’s given us surprises. We’ve learned that it’s only 4% made up of ordinary atoms, about 25% is made up of dark matter, which is completely unknown, but more than 70% is even more mysterious – energy latent in space itself. And so the challenge in the future is to understand the nature of dark matter, to understand the nature of space, and also to understand the way our universe has changed, from a Big Bang, which is very dense and very hot, to our complex cosmos nearly 14 billion years later.
Thanks to Research Corporation, a foundation for the advancement of science.
