Photonic Boom?

Matheous-2 | 15:57 Mon 10th Mar 2014 | Science

9 Answers

We all know and have seen footage of 'sonic boom' when capable aircraft break through the sound barrier.....
Is it reasonable to assume there may be a similar effect if we had a craft capable of breaking the speed of light barrier?

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jim360

The only problem with this question is that there isn't a craft capable of breaking the light speed barrier, nor ever will be most likely. The nature of the light barrier and the sound one are totally different. In the case of a sound barrier, it was more an engineering problem than anything else. In the case of the light barrier, it's something that underlies the entirety of physics as we know it today. Not much you can do about it.

The only exception would be if you sort of "cheated" and managed to find a way of travelling between two points in a shorter route than light would take. Similar, in a sense, to the difference of travelling between New York and London. One could either follow the surface of the Earth (as light might have to do) or dig a tunnel between the two points. Then if two people travelled at the same speed, one in the tunnel and one on the surface, the person in the tunnel would arrive quicker, even though he's not breaking any theoretical "speed limit".

jim360

All that said, the purely theoretical answer would be, to an extent, yes. For any objects travelling faster than the speed of light, known as "tachyons", the way in which light behaves would be similar to the way that sound behaves for a supersonic craft. The object would arrive at your location before its sound does, so you would only hear the oncoming craft once it has passed you. And then you might hear two separate sounds: those emitted as the craft approached, and those from as it travelled away. The same sort of thing goes on with tachyons, as this rather pretty animation shows:

http://en.wikipedia.org/wiki/File:Tachyon04s.gif

In a second answer, the speed of light in some materials is such that it is possible for an object to travel faster through that medium (so in glass, for example, the speed of light is about two-thirds that of its speed in a perfect vacuum). In such cases we really do see a sort of "photonic boom", in the form of what is called the Cherenkov radiation:

http://en.wikipedia.org/wiki/Cherenkov_radiation

The effects are, again, rather pretty. In this sense the answer is "yes, but only of light is slower than normal".

Sycamore3House

This question reminds me of being scared when I was a child hearing the 'sonic booms' from Concorde approaching the UK from New York. Every night it flew you could hear the booms at if I remember correctly at about 9.30pm to 9.45pm. When I was young it used to scare me but As I got older we used to think it was great to be out at night and hear them. I remember a lovely Bonfire night weather wise and being on the headland with my friends and hearing them.

LazyGun

I think a photonic boom sounds pretty intriguing ;)

Following on from Jims comments re Cherenkov radiation ( much abused in sci-fi), article here on it, funnily enough entitled Cherenkov radiation is a sonic boom for light ;)

http://io9.com/5947197/cherenkov-radiation-is-a-sonic-boom-for-light

Matheous-2

Question Author

Thanks guys for such knowledgable answers! I really thought it was all hypothetical- Didn't know about Cherenkov radiation which actually displays what I imagined!