Part of the College of Science Lynch Lecture Series
with Prof. Jeremiah P. Ostriker
Charles A. Young Professor Emeritus,
Department of Astrophysical Sciences
In the last 100 years, an extraordinary amount has been discovered about the universe. It wasn’t until the 20th century that astronomers discovered that ours was not the only galaxy, but one of many. Later still we were able to use increasingly sophisticated telescopes that allowed us to see so far out into space that we can actually look back in time.
Dark matter is all around us; it fills the universe and yet we cannot see it, touch it or even determine what it is. Astronomers the world over are still trying to explain this elusive presence in the Universe – a presence with nothing except its weight to prove its existence. So far all it has is the name: dark matter.
But this increased knowledge brings with it even deeper mysteries:
Once we realised we could calculate the weights of planets and stars by measuring their gravitational pull, we started to realise that there was much more matter in the Universe than can be accounted for by the visible objects alone.
There are elements – particles of some kind perhaps – that don’t shine, don’t react with anything and yet they exist in the Universe. It seems to be their gravity that is the "glue" that holds galaxies together, and is responsible for the growth of cosmic structures from tiny early seeds.
More recently still, we have discovered strong evidence to suggest that alongside this dark matter is an even stranger component of “dark energy”, which dominates over gravity and is causing the Universe to expand at an ever accelerating rate. What this means for the future of this Universe is something we can still only guess at.