First up is June talking about chemistry in space.
If you look up, the visible universe is very different – parts of it have very different characteristics. Until recently, the only way to look at space chemistry was to look at light. In the fifties, we had radio astronomy but it took until 1958/1959 before we could see things larger than carbon dioxide (it was easier to detect smaller molecules due to the way that they emit light). In the seventies, millimetre telescopes opened the field as they could look at a large number of large molecules, thus giving birth to the discipline of astro-chemistry.
Initially, there were astronomers who didn't believe that molecules could survive the radiation in space. These days, the Atacama Large Millimetre Array in Chile is very important for astro-chemistry. It's a sub-millimetre telescope with 66 antennae. But how does astro-chemistry work? First we need to collect photons and examine the patterns. What are the changes of energy in the particle? These patterns are like fingerprints. Once we have identified them we can relate it back to work done in the lab and we can then distinguish the particle.
Identification is one thing, modelling is another – kinetics, thermo-dynamics. In a lab, it's relatively straightforward to add "A" to "B" and then investigate "C" through spectroscopy or weighing – there are many ways to examine it. There are also many variables you can change – temperature, concentration, pressure for example. Astro-chemists don't have this control – it's a one shot experiment and the universe determines the variables. There are huge temperature variations in space and there isn't much of a concentration of the molecules that we want to look at.
In low temperatures, molecules don't have the energy to cross the energy barrier. In some clouds, there are only around 300 molecules in a cubic centimetre. To give some context in a die of the same size, there are 1024 molecules. In more diffuse regions, molecules could be as far apart as the size of eight football pitches. Then there are the problems caused by using ground-based equipment due to photons being absorbed by the atmosphere.
So far we haven't identified any molecules with more than fourteen atoms, but we have found things such as carbon dioxide, water, methanol and sulphur dioxide. It's harder to identify larger molecules but all of this means there is chemistry taking place in space. For reactions to occur you need a surface. In space this is dust. Without dust, our models don't work and this is especially the case with dihydrogen. No-one knows how the dust grains form or how things stick to the surface but we can investigate this dust in two different ways.
In the infra-red spectrum, we get a reading from a molecule when it vibrates. When it's attached to a surface, the vibration changes. The other way is to collect dust particles. We’ve been doing this for years from our upper atmosphere, but these are orphan dust particles. More recently, we've been trying to collect from comets. In fact this is how we discovered glycerine in space. Then in 2010, they discovered "Buckyballs" a Carbon 60 molecule. It is so symmetrical that it only emits four signals but the equivalent of 1.5 moon masses of it were discovered.
So, chemistry is happening in space and we can detect it, but why is this important? Well, space chemistry is essential for cooling down gas clouds, which is key for star formation. So, by looking at molecules, we can look at the history of the universe.
Next up we have Simon who is weighing galaxies (or more accurately, measuring their mass content).
But why would we want to weigh galaxies? How would we weigh galaxies? What would we learn from weighing galaxies? But before we get onto those questions – what is a galaxy? It's a system of stars, gasses and dust held together by gravitational attraction. Our galaxy, the Milky Way, is a spiral galaxy and it's "milky" because we can't resolve all of the stars with our eyes. The catchily named NGC6744 is the most like our galaxy in terms of size, mass and its spiral arms. There are other types of galaxy: elliptical galaxies have more chaotic stars that do not just orbit around a centre, then there are hybrid galaxies such as the "sombrero" galaxy – a mix between elliptical and spiral.
So, why would we want to weigh galaxies? If we can weigh a galaxy then we can measure the overall mass of the universe. This would be a little like trying to estimate the mass of a house by weighing one brick. So we'll miss things out, but we can make adjustments. If we know the mass of the universe, we can better understand its fate. Enough mass will halt the expansion of the universe and cause it to slowly collapse. We can also measure dark matter, from which we can learn about galaxy structure and formation. Examining the mass of galaxies also gives us clues as to which ones might have merged in the past – this tells us about the densities of galaxies in the early universe.
How do we weigh galaxies? There are three ways. Firstly, we can measure visible light. We know our own sun's mass and brightness and from this we can extrapolate the mass of other stars. This gives us "visible mass" but doesn't give us any measurement of dark matter. The second way is to measure the rotation of galaxies – faster rotation means that more mass is required to hold the galaxy together. If it spins twice as fast, it needs four times the mass.
The third way is using gravitational lensing – how much does the gravitational field of the galaxy bend light from sources on the far side of the galaxy? Then we measure the separation between the image and the source – more distance means more bending means more mass. Gravitational lensing leads to so-called Einstein rings which you can replicate using the base of a wine glass.
What can we learn from weighting galaxies? Well, there is not enough mass in galaxies to explain the lensed images that we are seeing – the Einstein rings are much larger than they should be. In fact visible mass is just the tip of the iceberg – mass of galaxies is made up of around 10% visible mass and 90% dark matter. There is a dark matter halo around all galaxies. This means that if you can model a foreground galaxy then you can use it as a telescope to disentangle background images - this gives a free 30 times magnification. The current best estimate for the weight of the universe is a billion times a trillion times the mass of the sun.
Following a space quiz and sometime writing messages using galaxies, it's time for Ed, the final speaker whose talk is named Our Universe - So Simple, Yet So Much We Don't Understand.
Our place in the universe – Earth is 12,000km across. Day three of Pint of Science Festival is the anniversary of John F Kennedy's speech about Gagarin being the first man in space when he announced America's intention to win the race to the moon. We are protected by the sun, which is 1.5 million kilometres in diameter. We're part of a solar system which measures 5.9 billion kilometres from the sun to Pluto.
The sun is just one star is a galaxy containing some 200 billion of them. The galaxy is around 100,000 light years across, that's 10 trillion kilometres. Our galaxy is part of an expanding universe filled with galaxies. The deepest picture that we've ever taken of the universe is of 11 billion light years away – that's 1022 kilometres.
The universe is accelerating – things are moving apart faster but what is providing the energy? We believe that it's dark energy and it seems to provide 70% of the energy in the universe (dark matter is thought to make up 25% of the energy and molecules just 5%) We fit the universe to our models, if it doesn't fit then we change the model. We keep working with a theory until it stops working.
At the moment our best model shows that the universe is expanding. The Standard Model shows what we are made up from. There are quarks and leptons and then there are the particles that give rise to forces. Photons give us electromagnetism, gluons give us the strong force (which stops atoms from blowing up), vector bosons give the weak force (which is needed to make the sun function), gravitons with give gravity and the Higgs which delivers mass (without it everything would have zero mass).
There are also anti-particles. As we know Einstein came up with e=mc2 which was experimentally verified in 1932 by Cockcroft and Walton. Even though we know things like this, we still have to make some assumptions about the universe. Most of our models assume that the universe is homogenous and isotropic.
The big bang theory predicts that the universe is expanding and that the lightest nuclei were formed in the first few minutes. Now, some 13.8 billion years later, the universe covers some 93 billion light years of space. At 400,000 years old the temperature of the universe was 2.7 degrees Kelvin. At this stage, the universe is smooth but with some very small fluctuations in temperature. These fluctuations tell us about the universe when it was just 10-32 seconds old. But if the universe is homogenous and isotropic then structures can't form. So, what caused those fluctuations in temperature? Our best guess is that there are 106,688 galaxies in the universe. Can it really be homogenous on such a large scale?
What and where is the dark matter? It's not ordinary matter – it must be a new particle. The Large Hadron Collider in Switzerland had two goals - to find the Higgs boson and to find dark matter. We have discovered the Higgs but seem no closer to finding dark matter. Is it really a fundamental particle? Have we misunderstood gravity? Our observable universe was around the size of a grapefruit when inflation stopped. It grew exponentially in a very small time frame. Inflation explains why the universe appears flat even though it might not be. It seems that there were quantum fluctuations that caused the structure formations. Inflation seems to fit the data really well, but what caused inflation?
Our theory of gravity and the standard model seem to describe the universe very well, but some issues remain. How do we reconcile gravity and quantum mechanics? What will the fate of the universe be? What is the nature and amount of dark energy? Why is gravity so weak on Earth? Even a magnet can pick up a drawing pin. Does the gravity seep into an extra dimension?
Those philosophical questions draw the first ever Pint of Science Festival in Nottingham to a close. The team behind it organised a great event – three nights, four venues, three speakers per night. The three nights that I went to were all sold out and the speakers were all good. It's great to see that there is an audience for science in Nottingham and I can't wait to see what happens when Pint of Science returns on 2017.
Pint of Science Day 1 – The Psychology of Addiction
Pint of Science Day 2 – Sourcing Food for an Increasing Population
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