The real reasons nothing can go faster

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Source:  BBC

By Chris Baraniuk

It was September 2011 and physicist Antonio Ereditato had just shocked the world.

The announcement he had made promised to overturn our understanding of the Universe. If the data gathered by 160 scientists working on the OPERA project were correct, the unthinkable had been observed.

Particles – in this case, neutrinos – had travelled faster than light.

This time the scientists got it wrong

According to Einstein’s theories of relativity, this should not have been possible. And the implications for showing it had happened were vast. Many bits of physics might have to be reconsidered.

Although Ereditato said that he and his team had “high confidence” in their result, they did not claim that they knew it was completely accurate. In fact, they were asking for other scientists to help them understand what had happened.

In the end, it turned out the OPERA result was wrong. A timing problem had been caused by a poorly connected cable that should have been transmitting accurate signals from GPS satellites.

There was an unexpected delay in the signal. As a consequence, the measurements of how long the neutrinos took to travel the given distance were off by about 73 nanoseconds, making it look as though they had whizzed along more quickly than light could have done.

Despite months of careful checks prior to the experiment, and plentiful double-checking of the data afterwards, this time the scientists got it wrong. Ereditato resigned, though many pointed out that mistakes like these happen all the time in the hugely complex machinery of particle accelerators.

Why was it such a big deal to suggest – even as a possibility – that something had travelled faster than light? And are we really sure that nothing can?

We cannot go as fast as light (Credit: SCPhotos/Alamy Stock Photo)

We cannot go as fast as light (Credit: SCPhotos/Alamy Stock Photo)

Let’s take the second of those questions first. The speed of light in a vacuum is 299,792.458 km per second – just shy of a nice round 300,000km/s figure. That is pretty nippy. The Sun is 150 million km away from Earth and light takes just eight minutes and 20 seconds to travel that far.

He needed to use ever-larger amounts of additional energy to make ever-smaller differences to the speed

Can any of our own creations compete in a race with light? One of the fastest human-made objects ever built, the New Horizons space probe, passed by Pluto and Charon in July 2015. It has reached a speed relative to the Earth of just over 16km/s, well below 300,000km/s.

However, we have made tiny particles travel much faster than that. In the early 1960s, William Bertozzi at the Massachusetts Institute of Technology experimented with accelerating electrons at greater and greater velocities.

Because electrons have a charge that is negative, it is possible to propel – or rather, repel – them by applying the same negative charge to a material. The more energy applied, the faster the electrons will be accelerated.

You might imagine that you just need to increase the energy applied in order to reach the required speed of 300,000km/s, but it turns out that it just is not possible for electrons to move that fast. Bertozzi’s experiments found that using more energy did not simply cause a directly proportional increase in electron speed.

As objects travel faster and faster, they get heavier and heavier

Instead, he needed to use ever-larger amounts of additional energy to make ever-smaller differences to the speed the electrons moved. They got closer and closer to the speed of light but never quite reached it.

Imagine travelling towards a door in a series of moves, in each of which you travel exactly half the distance between your current position and the door. Strictly speaking, you will never reach the door, because after every move you make you still have some distance still to travel. That is the kind of problem Bertozzi encountered with his electrons.

But light is made up of particles called photons. Why can these particles travel at the speed of light when particles like electrons cannot?

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Categories: Physics, The Muslim Times

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