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Slide 1 - Extreme Machine
Slide 2 - The Large Hadron Collider at CERN
This is the inside story of the most powerful particle accelerator on the planet. It's the most complicated machine ever built.
It's called the Large Hadron Collider, or LHC, and its job is to discover what the universe is made of.
Slide 3 - The Large Hadron Collider at CERN
It's taken 25 years to plan and build, involving around 8,000 scientists and engineers from all over the world. It is one of the biggest scientific experiments in history.
Slide 4 - The Scale of Things
A dew drop is made of a billion trillion molecules of water (1021). Each molecule is made of an oxygen atom and two hydrogen atoms (H2O). At the start of the 20th century, atoms were the smallest known building blocks of matter.
Each atom has a nucleus, surrounded by electrons. The nucleus of a hydrogen atom is just a single proton. Protons consist of three quarks.
Quarks are fundamental particles, not made up of even smaller particles. They're way too small to see directly, so how do we know anything about them?
Slide 5 - The Limits of Light
Normal microscopes can't see details smaller than about a micrometer across because of the wavelength of light. Atoms are much smaller, so you can never see them with light.
In other words, normal microscopes are fine for studying plant and animal cells, but no use for seeing inside the atom.
Slide 6 - Seeing Smaller
This electron microscope uses a beam of electrons instead of light - it's actually a small particle accelerator. The electron beam has a much shorter wavelength than light rays, so it can make out much smaller details, right down to spotting individual molecules. But you still can't see atoms.
Slide 7 - Building Bigger to See Smaller
Investigating particles a billion times smaller needs a different approach. Instead of shining a beam on something, accelerators smash particles - either into a target, or against each other. The faster the particles are going, the more energy they have when they hit, and the more you can learn from what happens.
To give the particles enough energy to reveal all the different particles that we think the universe is made of, you need a really big accelerator.
Slide 8 - The Ultimate Microscope…
Over the last 50 years bigger and bigger accelerators have, bit by bit, revealed a hidden world of unimaginably tiny particles inside of atoms. Physicists have sorted these into a framework called the Standard Model that describes what we see pretty well, but it isn't the complete picture. It doesn't include gravity, for example. Or explain what gives particles mass.
By colliding protons (and lead nuclei) at a much higher energy than ever before, physicists are pinning their hopes on the LHC to provide the missing pieces.
Slide 9 - Particle Creator…
Smashing particles together this hard doesn't just break them open, like a nut. Einstein realized that energy can be turned into matter, and matter can be turned into energy. The collisions in the LHC are so powerful some of the energy actually creates particles that weren't there before. So, a more powerful accelerator lets you create heavier particles.
Slide 10 - …and Time Machine!
When we look at distant galaxies, it's taken billions of years for the light to get here. We're looking back in time. But we can't ever see all the way back to the start of the universe because there was no light to see it by - light just didn't exist.
By recreating the conditions just after the Big Bang, the LHC experiments are like a time machine taking us right back to the beginning of the universe, when it was unimaginably hot and dense.
Slide 11 - Detecting the Invisible
The particles created in the LHC are way too small to see. Many only exist for a tiny fraction of a second, decaying almost instantly into other particles. Huge, complex detectors the size of mansions record aspects of the particles as they zap outwards from the collision. Physicists can then carefully reconstruct what must have happened, and see if there were any new particles or effects.
Slide 12 - Extreme Conditions…
To make the magnets strong enough, they need to be superconducting. They are bathed in liquid helium at -271.3°C (just 1.9 degrees above absolute zero) - that's colder than outer space. The beam pipe needs all the air pumped out of it to create an ultrahigh vacuum, where the pressure is ten times lower than on the Moon - that's emptier than outer space. Otherwise, the hadrons would keep colliding with air particles as they hurtle round the 27km tunnel 11,000 times a second.
Slide 13 - For Extreme Collisions…
Individual protons collide with the energy of around a dozen flying mosquitoes. That doesn't sound much until you realize that the energy is concentrated into a space a million million times smaller than a mosquito.
The total energy in the beam is equivalent to a 400 tonne train (like the French TGV) going at 150 km/h. Where the beams cross, they're squeezed to less than the diameter of a human hair.
Slide 14 - …And in 2008?
Here's a simulation of the particle trails left by a collision between two lead nuclei. Making sense of particle signatures like this is difficult, but the reward could be a major discovery that changes our understanding of how the universe works. For the thousands of physicists studying the results from the LHC, it's an incredibly exciting time.
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