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How seriously do we need to take the laws of physics?

Posted By Robert Bell, Thursday, May 17, 2012

In the Seventies, there were major fears that the world was running out of stuff.   Food, metals, energy resources, you name it.  A 1972 book called The Limits to Growth portrayed a future in which population growth, industrialization, pollution, food production and resource depletion ended in tears unless we learned to curb our appetite for growth.   

In 2001, a Danish statistician and environmentalist named Bjørn Lomborg published The Skeptical Environmentalist.  He made a startlingly different case, based on numbers.  If we are running out of everything, he wrote, then why are the costs of almost everything going down?  The laws of supply and demand say that the scarcer a commodity, the higher a price it will fetch.  But in case after case he presented, the opposite had happened.   

Innovation explains the difference.  We have become much better at finding and extracting raw materials, and at making more efficient use of them.  The global supply of useful stuff keeps expanding because our ability to get at it continues to grow.  

Of course, there are limits, whether to the supply of oil and gas or to the Earth’s ability to absorb greenhouse gases.  There are always limits – but we don’t seem to be very good at forecasting them.   

Which brings me to the laws of physics.  Currently, the number one discussion on WTA’s LinkedIn Group is about bandwidth.  It started when we posted news of Newtec announcing a new speed record by helping Yahsat deliver 310 Mbps over a 36 MHz transponder.  Group members weighed in with questions and answers about the achievement, and a NovelSat executive described delivering 365 Mbps over a 72 Mhz transponder for SES, which helped the company win our Teleport Technology of the Year Award in March.         

This is important work.  Satellite technology can provide high bandwidth capacity to places that no other technology can reach as cost effectively.  It can deliver one-to-many better than anything else.  But the total bandwidth available remains bound by the laws of physics.  Every advance that lets us send more bits per hertz – from frequency re-use to adaptive coding – is of great significance.   

This discussion, however, raised an interesting question in my mind.  Practically speaking, just how seriously do we need to take those laws of physics?  We know there are limits.  Claude Shannon of Bell Labs defined the theoretical maximum information transfer rate of a communications channel, for a particular noise level, and it became known as the Shannon Limit.  His son was a childhood friend of mine and I remember Dr. Shannon as a quiet, courteous gentlemen quite absorbed in his own remarkable thinking process.  I am no more equipped to dispute his Limit now than I was at the age of ten. But I wonder.  In the manufacture of silicon chips, we read every few years that we are coming up against a theoretical limit which will prevent us from squeezing any more transistors or wiring onto that tiny square of high-quality sand.  And every few years, regular as clockwork, we find that the forecast date for reaching that theoretical limit has been pushed a few more years into the future.   

I suspect that, in the back rooms of the technology companies in our membership, there are wild-eyed visionaries conceiving the next impossible bandwidth breakthrough and making it work.  Which means that there are a lot more interesting discussions waiting to happen. 

Tags:  bandwidth  compression  frequency  physics  spectrum 

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