Dastardly Dark Energy with Kathy Romer (6/5/13)

6th May 2013

In our 51st show, we turn to the darker side of the universe by looking into its most mysterious component. It’s so mysterious, scientists only inferred its existence for the first time in 1998. Astronomer Dr Kathy Romer from the University of Sussex joins us to probe this darkest of all dark things as we try to unravel the secrets of the universe…

Following on from our shows with Tony Padilla, Ed Copeland and Meghan Gray, we can turn our sights onto that Dastardly Dark Energy. This stuff is supposed to make up 68% of the stuff in our universe! Compare that to the normal stuff that makes up you and all the stuff around you like paper and other such revision materials which only accounts for 5% of the universe.

So how did we discover dark energy? In 1998 and 1999, astronomers measured the distances to exploding stars called Supernovae. They discovered that the universe had expanded more in the most recent half of it’s life – the expansion of the universe was accelerating! This was totally unexpected – the best things in life are.

Makeup of the UniverseOther evidence for a mysterious ‘anti-gravity’ force surfaced in the decades that followed. Observations of the universe have shown that it’s flat, rather than ‘curved’. The concoction of matter and dark matter could not explain the flatness of the universe and adding dark energy into the mix allowed astronomers to explain this boringly flat universe.

Not to dwell on this evidence, astronomers looked at how common astronomical things like galaxies, galaxy clusters and super clusters were on different scales. For example, sky scrapers aren’t very common in your bathroom but on the scales of cities like London or Tokyo they are prevalent. Looking at this distribution, the presence of a dark energy can be inferred! That’s 3 pieces of independent evidence for this mysterious stuff.

Okay, so we know there’s something out there. But what is dark energy? The short answer is we don’t really know! There are two main theories out there that speculate what this mysterious stuff is. The simplest and most common is the ‘concordance model’, or Lambda-CDM (Λ-CDM). This adds a constant dark energy term throughout all of space and time. Essentially, this is the ‘cost’ of having empty space. Nothing is free in life!

Kathy has also come into talk about our next efforts to unlock the secrets of dark energy. The Dark Energy Survey will probe dark energy using 4 different methods at the same time over an unprecedented area of the sky and further back in time than before. Impressive stuff!

Dark energy has the effect of pulling parts of the universe, stars, planets and us, apart. It exhibits properties that act like ‘negative pressure’ – Just imagine blowing into a balloon and it getting smaller in volume. It seems likes pretty strange stuff and it remains pretty elusive.

Fate of the Universe

The universe it is expanding, and this expansion will decide the overall fate of everything. If there is enough dark energy, the expansion will continue to grow forever and the universe will be torn apart “Like warm bread” – George O’Neill 2013.
However, if in the future, the forces that are trying to stop the motion become stronger than the dark energy, we may end up with ‘The Big Crunch’. If this happens all the matter of the universe will collapse back onto itself.

Modified Gravity

One of the attempts to explain whether or not we need to find this ‘Exotic Dark Energy’ is Modified Gravity. Scientists around the world are trying to prove Einstein wrong and find new and complicated equations to solve the mysteries of the universe in a more elegant manner than we have so far.

The Dark Energy Survey is the biggest ever survey that is looking at the dynamics of the universe. Using a state of the art Dark Energy Camera mounted on the Victor M. Blanco telescope in Chile, the team will scan the heavens to produce the most detailed look at the expansion of the universe ever undertaken.