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Faster Than A Speeding Light Beam? - by John Prytz

We are well aware that there is an eleventh commandment (thanks to Einstein) that says something along the lines that ‘thou shall not travel at or faster than the speed of light’ (or any form of electromagnetic energy) which in space, unhindered, is roughly 300,000 km/second – the cosmic speed limit. Why does the speed of light (in a vacuum) have the value it has? Why not 600,000 km/second or 150,000 km/second or 3,000,000 km/second or even 30 km/second? I don’t know, and I suspect nobody else does either. However, it has to be some value and I guess the value it has is as good a value as any other. But there's a special condition attached.

 

And what’s the special condition? Well, it’s that ‘in a vacuum’ bit.

 

Regardless of a vacuum or otherwise, of course you can, and must, travel slower than light speed, and indeed, that’s what we all do. Perhaps one day physics engineering will achieve the reality of Star Trek, what with warp-drives achieving superluminal travel via hyperspace or some such, but in the here and now, its subluminal, like it or lump it.

 

But, even light travels slower than the speed of light, when light enter another medium. For example, it takes a long, long time for a photon (a particle of light) produced in the core of our Sun to reach the surface of our Sun, because there’s so much stuff in the way, but once reaching the surface of the Sun, then off it goes quick-smart, taking only another eight minutes to reach your eye. Light speed in say air, is less than in space (assumed to be the ‘in a vacuum’). Light speed through water is further retarded, and light traveling through glass is slower yet.

 

So, let me propose this thought experiment, and remember this is only a ‘what if’ thought experiment, along the lines of ‘what if’ you had this really fast submarine, say one that could travel underwater at 299,000 km/second. That’s faster than light itself travels in water (225,000 km/second) and a race between a light beam and our super submarine would see the submarine the winner.  So, in fact you’ve ‘broken’ the eleventh commandment and traveled faster than the speed of light (albeit with an asterisk attached pointing out it was in water, not ‘in a vacuum’ or in space – same difference). I’m not exactly sure what this would accomplish other than bragging rights, as you could legitimately boast that you traveled faster than the speed of light!



Science librarian; retired.

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