[ExI] hard science

spike spike66 at att.net
Wed Feb 12 05:44:26 UTC 2014


On Tue, Feb 11, 2014 at 6:30 PM, William Flynn Wallace <foozler83 at gmail.com>

Assume tens of thousands of years from now:



Will they still use wires for anything? I hate wires!  What do you need to
go wireless?  More wires.)



Hmmmm.  Bill, the mechanical analog to what you are asking is "Can we
transmit mechanical work without shafts?  I hate shafts."


The answer is yes you can, however.  It isn't the right way to transfer
mechanical force in most applications.  For instance, you could take
mechanical energy and use it to create sound waves, such as in a big
speaker, like you might see at a stadium rock concert.  Then some distance
away, another speaker would pick up the vibrations and would itself vibrate,
moving a magnet mounted to the speaker cone, generating electrical energy,
which could then be turned into mechanical energy.  So you have transmitted
mechanical energy without a big heavy greasy shaft.  Well, you transmitted a
little bit of it anyway, a very small fraction of a percent of what you
started with.


Transmitting electrical power without a wire is more efficient than that two
speaker trick.  You have the option of turning the electric power to a
laser, shining the laser on a distant target and turning the light back into
electrical energy.  As in the example above, you would get back a little of
the energy you put in.  In some applications that might even be an OK way to
go, such as when you only need a small amount of energy at the target, or
when you don't have the option of a wire, as in Keith Henson's vision with
the laser powered launch vehicle.


However, shafts and wires are your friends for most energy transmission
applications, and still will be tens of thousands of years from now.



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