140. Going Faster Than Light

09 Jun

Nothing can go faster than lightThat is the immutable irrefutable edict. Einstein’s legacy and the ultimate law, unfortunately it is wrong, just a little bit but it is still wrong. The wrong part is ‘faster than light’. We can, and do go faster than light, and it shows. This is Cherenkov Radiation.

There are two things you need to know, firstly is that light can go at that famous speed, c as it is written in e = mc². The blistering 300,000 km/s. That is the speed of light. Nothing can go faster than that speed, but light doesn’t always go so fast, only in vacuums such as space. When going through actual stuff, Light slows down, and then we can overtake it, with some very interesting consequences. When light goes through water it is slower, and then we race it, and beat it.

You know the sonic boom – when something approaches the speed of sound the air in front literally cannot move away; so pressure builds up until there is a large shockwave. This flies away at the speed of sound and  produces a thunderous sonic boom. When we go faster than light, we get this too, it is just not quite so loud.

This is Cherenkov Radiation and it won Pavel Alekseyevich Cherenkov the Nobel Prize. What happens is this, in nuclear reactor cores, there is water; it cools the whole system down. In the water the speed of light is reduced, down to the still rather zippy 224,910 km/s. However this is a nuclear reactor, it can beat that. Charged electrons released into the water, because they are charged, it disrupts the local electromagnetic field in the medium(water). Surprise surprise, because the electron is traveling faster than the speed of light in that medium, the electromagnetic charge which is limited by the speed of light in that medium cannot escape. The waves propagate in front and then the magic happens. The photonic shock wave, light is released. In the water, this causes a blue glow.

Now bear in mind that charged particles like electrons are microscopic, so the effect isn’t so spectacular as a sonic boom. Similarly if I accelerated a flea past the speed of sound, the sonic boom produced would be audible, but not particularly loud. In the same vein, were one to accelerate an electrically charged fighter jet beyond the speed of light in a medium, the glow would be significantly blinding, let me assure you.

On a final note, remember that the speed of light changes in every medium or material. This would work with carpeting, diamond or knitting. Just remember, whilst we can best light in these mediums, the physicists have it right. Light travels at 300,000 km/s in the vacuum of space, and we can never beat that.

Unless of course we don’t understand the Universe at all. However the chances of that are rather slim.


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One response to “140. Going Faster Than Light

  1. Peter Edwards

    July 19, 2011 at 22:07

    As interesting as Cherenkov radiation is, saying that it breaks the rule of faster-than-light speed, while technically faster than light in the circumstance, is still incorrect. The rule about faster-than-light travel is in regards to the speed of light in a vacuum, and it technically has nothing to do about light itself as it is about the relativistic effects of moving at such a high velocity. As the velocity of an object with mass increases, the mass of the object increases and the flow of time, as experienced by the object, slows down. As the object approaches the speed of light it’s mass approaches infinity (and since accelerating an object with mass requires energy proportional to the mass, accelerating an object with infinite mass requires infinite energy) and time approaches stopping (so accelerating it further would create temporal paradoxes).

    So although Cherenkov radiation is the results of charged particles going faster than light, it’s only going faster than light in water, not in a vacuum, and therefore does not violate the faster-than-light rule.


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