# Where the smart money is…

Mark Twain is reputed to have said on investment choices "Buy land – they’re not making it anymore". There’s got to be a good deal of truth in that – it’s hard to see that there will be a decreasing demand for land on a global scale in the next century (though there are perhaps some local areas where that might happen).

But there’s something else that’s not being made anymore that is in great demand, and that might prove to be a pretty good investment too.  Bandwidth. By bandwidth, I’m referring to the electromagnetic spectrum, and specifically to our insatiable demand for devices that use electromagnetic waves – radio, television, mobile phones, radar, remote garage door openers and the like.

Electromagnetic waves (e.g. radio waves) obey of course the basic laws of electromagnetism, that are encompassed in Maxwell’s equations. (Much loved or hated by students, depending on your opinion.) Maxwell’s equations are actually really easy to work with, because they have the fantastic property of being linear. Mathematically, there’s a tedious definition of what linear actually means, but the outworking of it is this – if you have two things that obey Maxwell’s equations, you can add them together and the result will also obey the equations. In practical terms this means that if you have, say, a radio wave at 100 MHz and a mobile phone wave at 1000 MHz they can happily coexist in the same region of space (e.g. your living room) without stuffing each other up. You can send numerous signals all at once, so long as they use different-enough frequencies, and one won’t affect the other.

As we develop more and more technology that puts out electromagnetic waves, we are more and more restricted on what frequencies are available for their use. (That said, technology also helps us to be able to cram more signals into the same range of frequencies – i.e. narrowing the bandwidth required by each signal). The licensing of frequencies (e.g. permits to use that frequency) tend to be controlled by individual governments, and they are valuable commodities. It’s hard to see that bandwidth (meaning a range of frequencies across a ‘band’) will become less valuable in general in the near future.