Scientists at CERN have recently obtained a bizarre result: neutrinos (tiny neutral subatomic particles with almost no mass) have apparently exceeded the speed of light. This has thrown the scientific community into confusion. The speed of light being the ultimate speed limit is the basis for much of modern physics. If it turns out that it can be broken, does this mean that we need to rethink all of physics? Or was the answer to this conundrum hidden in current theories of physics all along? Four years ago, I noticed a possible ‘loophole’ in relativity that could allow speed of light travel. I put together the article below in an attempt to explain it:
Travel at the speed of light has long been a common feature in science fiction stories and films, where spaceships can traverse the stars, covering enormous distances in a blink of the eye. But, as any physicist will tell you – this simply isn’t theoretically possible. It all boils down to the theory of Relativity, one of the most famous theories of all time, which was proposed by none other than Albert Einstein in 1905.
Einstein’s theory was based upon two ‘postulates’ – statements about the nature of the universe that he deemed to be true, although he had not yet experimentally confirmed them nor derived them from other true statements. They were, however, experimentally confirmed later. The two postulates now form the basis of Special Relativity.
These postulates are:
- The speed of light, as measured by an observer moving at a constant velocity, is the same no matter what the observer’s velocity is.
- The laws of physics, as perceived by an observer moving at a constant velocity, are the same no matter what the observer’s velocity is.
A good way to visualise the second postulate is to imagine throwing a ball up into the air and catching it whilst sitting on a train moving at a steady 40 kmph. The ball will go straight up and fall back down into your hand, moving under gravity. Now if you imagine doing the same thing whilst standing on the platform, you can see that the ball will behave in exactly the same way. The fact that the train is moving and the platform isn’t makes no difference to the way you perceive gravity acting on the ball.
The first postulate is a little bit stranger. This time, imagine you are on the train moving at a steady 40 kmph and another train overtakes yours. It is travelling at 50 kmph, but from your perspective (i.e. if you aren’t aware that your train is moving) it appears to be travelling at 10 kmph past your train. If your train then did come to a stop, you would see that same train is moving past you at its real speed of 50 kmph. But now for the weird part. You are sitting on the train, which is once again moving at 40 kmph. This time, a super-fast train overtakes your train. This super-fast train is travelling at the speed of light. To amuse yourself, you decide to pull out your handy speed measuring device. You point it out the window to measure the speed of the super-fast train. Your device displays the speed as 1,080,000,000 kmph (300,000,000 metres per second). You take note of this, as your train pulls to a stop again. You take another measurement out the window, grinning in expectation. You know what speed the device will measure. Since you’re now not moving at all, you will now measure the ‘real’ speed of the super-fast train, and that must be 1,080,000,040 kmph, surely? But your jaw drops as the device displays its reading. To your amazement, it says 1,080,000,000 kmph, the same speed as before. But how, when you were moving before? Your measuring device then displays a message. In astonishment, you read the words: ‘Welcome to Relativity!’
Of course, there is no way that a super-fast train could travel at the speed of light, because one of the consequences of relativity is that as the speed of a massive object (i.e. one that has mass) increases, its energy increases exponentially, making it harder and harder to accelerate the object further. Therefore it would require infinite energy to accelerate an object up to the speed of light. As it is not possible to lay our hands on an infinite energy source, the super-fast lightspeed train cannot be built.
Or can it?
Let’s imagine that you enjoyed your train journeys so much that you decided to become a super-fast train engineer. You build a very long, frictionless track and begin testing your super-train prototype. The super-train is pulled along by magnets on the track. You watch from your control centre as your super-train accelerates, but to your frustration, you just can’t get it to go to the speed of light, as no matter how much you increase the magnetic field strength (or energy), it is just not enough.
You are just about to give up when a thought occurs to you. You’ve been busily trying to accelerate this super-train to the speed of light from the outside, and it hasn’t worked. What if you were to try to accelerate it from the inside?
You switch the magnets off and attach rocket boosters to the back of the train. You make sure there is enough fuel on board. Now the energy for thrust will be internally generated by the train, as opposed to being drawn from the outside. In your control centre, not quite knowing what to expect, you hit the fire button. The train accelerates down the track, gaining energy exponentially, but still accelerating as its fuel is gaining energy too. Therefore there is still enough energy to accelerate the train even as it approaches the speed of light and its energy becomes infinite… because the fuel energy has become infinite too. Before your astonished eyes, the train hits the speed of light barrier and…
Is there a good reason why this idea won’t work? It is difficult to say, but there is a way that the theory can be experimentally verified (without building a super-fast train, that is). Particle accelerators, using electromagnetic fields, routinely push tiny particles of matter (such as electrons) up to speeds that are very close to (but not quite) the speed of light. I propose that nanotechnology and particle physics come together in the creation of a ‘nanorocket’. This would be a tiny molecule with its own means of propulsion. This ‘nanorocket’ could be accelerated in a particle accelerator as much as possible, and then it would fire its own thrusters to accelerate further. Could it then accelerate up to the speed of light? Could it even go beyond it?
Four years later, the neutrino measurements were made. Neutrinos had apparently broken the speed of light barrier, even though it was theoretically impossible. However, when I investigated some of the special properties of neutrinos, I discovered something interesting. Neutrinos oscillate between their different flavours (types) and different masses (mass energies), whilst maintaining a constant momentum. This means that neutrinos are constantly accelerating and decelerating because in order to conserve momentum when their mass (mass energy) changes, they have to increase or decrease their speed. This means that the neutrino may well be a natural ‘nanorocket’ and the experiment that I proposed four years ago has already been conducted… with startling results.
The neutrino result has yet to be confirmed by other research teams. It could turn out to be some kind of measurement error, or perhaps other experimental factors have been overlooked.
But if it is a true result, it may not be necessary to rewrite all of physics – just to take a fresh look at relativity instead.