Faster Than The Speed Of Light
Professor Marcus du Sautoy begins with Einstein
These are the Apennine mountains in central Italy. Buried underneath them is one of the most sophisticated science labs in the world. Last month an international group of scientists working here on a particle physics experiment, called Opera, made an astonishing claim.
They said they had detected particles that seemed to travel faster than the speed of light. It was a claim that contradicts more than a hundred years of scientific orthodoxy.
Marcus du Sautoy
My name is Marcus du Sautoy. I'm a mathematician and as a mathematician I'm used to dealing with ideas that seem impossible in the real world. For me, its moments like this when data clashes with theory that's always rather thrilling. You can almost feel the shudder that passes through the entire scientific community when a result as strange as this comes out. Everybody's talking about it. Is this the moment for a grand new theory to emerge, that makes sense of all the mysteries that still pervade physics? Or has there just been a mistake in the measurement?
I'm going to explore one of the most dramatic scientific announcements in a generation. What does it mean and why does it matter?
Our story starts with light. For centuries light has fascinated us. Our ancestors built monuments to capture light from the Sun at particular times of the year. Light gives us colour, its how we see the world. Light floods the cosmos but, it has always been mysterious. One of the biggest mysteries about light is how fast does it travel? Unravelling this question would lead to one of the greatest and most surprising leaps in the history of science.
Until 350 years ago, many scientists argued that light didn't really travel at all. It was transmitted instantaneously from source to eye. But then, an astronomer making careful observations of the moons of Jupiter showed it took a finite time for light waves to reach Earth. That meant that light travel couldn't be instantaneous, it had to have a finite speed. But, another puzzle remained.
If light was a wave, scientists concluded that it must be transmitted through some medium, just the same way sound travels through air. This medium was given a name - The Ether.
It was thought The Ether was able to flow like the wind therefore, light waves that were travelling in the same direction as The Ether could travel faster than those fighting against it.
In the 1880s, scientists tried to measure variations in the speed of light, travelling in different directions. But, to their susprise they found no difference. However you measure it, light always went at the same speed. As the 20th century dawned, scientists were still wrestling with the strange behaviour of light and in particular what speed it travelled at.
The stage was set, the arrival of a genius who would unravel the mysteries of light and, in the process, transform our understanding of The Universe.
In 1902, a young physicist arrived in the Swiss town of Bern. He trained as a Physics and Maths teacher in Zurich but, had been unable to find a teaching job. Eventually, he found work in the Swiss patent office. It was far from a lofty, academic institution but it turned out to be just the environment he needed. His name was Albert Einstein.
Professor Fay Dowker Imperial College London "An amateur scientist, someone who didn't have an academic position, this patent clerk who worked on physics when he wasn't doing his day job. Quite an unusual person to be the one who revolutionised our ideas of space and time."
Professor John Ellis Kings College London "I don't know what the workload was in the patent office, maybe he had a lot of time to think. Somehow, he was able to think long and think hard."
The clerk's job gave Einstein time to ponder thought experiments. Deceptively simple scenarios that enabled him to explore the most complex of concepts.
Professor Ellis "Einstein was very much an individual, lone scientist, thinking his deep thoughts and precisely because he was working by himself he got insights that other people hadn't seen."
Einstein was fascinated by the mysterious behaviour of light. It was a wave, but it also hade the properties of a particle, what came to be known as a photon. How fast did it travel? he wondered and did it have a speed limit. From the age of 16 Einstein had been pondering a thought experiment. If one looks into a mirror and accelerates faster and faster towards the speed of light, does the image suddenly disappear? Einstein believed that his image wouldn't disappear. He started to think about how to resolve this paradox.
In the spring of 1905, Einstein was ready to launch his ideas on the world. In that one year, Einstein published four papers, any one of them would have been enough to create a sensation in their own right. It was arguably the most sustained and extraordinary burst of scientific creativity the world has ever seen. One of these papers transformed our understanding of light.
It contains a set of scientific laws that define, not just our world, but also our entire universe. At the centre of these is the statement that 'The Speed of Light when it travels in a vacuum is absolute' Nothing can travel faster. It was an incredibly audacious piece of reasoning.
Einstein realised that the way we looked at the universe was wrong. Particularly our intuitive sense of how time and space worked. We can see how by doing a thought experiment of our own with the help of a train. If I shine a torch while standing still on the platform, the beam of light from the torch will be going at the speed of light. But, what happens to the same beam of light when I'm on a moving train? The train is travelling at 140mph. If we switch the torch on now, for somebody standing outsidw, how fast do they think the light is travelling? Logic would suggest that the light is travelling at the speed of light from the torch plus the 140mph the train is doing. Einstein said no, the speed of light is a constant. It doesn't matter where you are in the universe or how you measure it.
Einstein's brilliance was to realise that if the speed of light was the same regardless of where you measured it from, then something else had to give. He comcuded it was time that was changing. Time was not a constant, instead it changed depending on how quickly you were moving. The faster you travel, the slower time passes.
These theories have a practical impact on the real world. One example being GPS or Global Positioning System.
Einstein's view of the world was seen as radical at the time and is still hard to grasp. But, over the years, countless experients have proved him right.
Einstein didn't stop there. He theorised that not only did light travel at a constant speed but, that speed was also the speed limit of the universe. Nothing can travel faster. That's because of the relationship between mass and energy. Einstein said that mass and energy were two sides of the same coin. That means if the amount of energy an object has increases then so does the mass. Crucially, increasing an object#s speed increases its energy
From a thought experiment, Einstein was able to radicallyalter our view of the world. H e concluded that the speed of light is constant and that nothing with mass can travel faster than this speed. These comcepts are at the heart of our modern understanding of the universe.