The Sky is the Limit The Sky is the Limit The Sky is the Limit The Sky is the Limit

The Mind-Set of Physical Limits over Time

There is an old folk adage that goes like this: The Sky is the Limit. The meaning was that anything was possible. That may have been true in theory, BUT in the real world there were limits everywhere. In the world of Physics, there were many limits;

speed of light

Most of these “limits” have been overcome in the last 200 years, but those were not physical LAWS, like Newton’s 3rd. Turns out they were just a lack of imagination, and failure to notice the clues that nature has provided.

Thr List of counter examples

I offer examples where Newton DID NOT notice ALL of the clues. The simplest clues were available in Newton’s time (and two thousand years earlier). It is unknown why Newton did not include this lowly machine “incline plane” in his studies of forces. incline-plane

One of the simplest of machines is the incline plane (known from the classical Greeks). Because of the mind-set we inherited from Newton, we would not even look for help in building a space engine [needing a uni-directional force] from an incline plane. It is true the incline plane is NOT the machine we are looking for, BUT when we blow the top off of the “limiting mind-set” by examining the incline plane, other examples are out there to offer us clues to follow.

My first example is the wood-splitting wedge, which is two incline planes glued together. This is simple example shows that some of the output force comes out in a different direction than the input force.

screw-jack The next example shows that all of the output force comes out at right angles to the input force. The screw jack (not used much any more, hydraulic jacks are more common now) gets its input power from the rotation of the drive nut in the horizontal plane and all of its output power in the vertical plane. You should notice that this is different than what Newton claimed.

aapt_fanCart The next example is more recent in time, and after Newton’s time. The propeller or fan blade is a moveable incline plane, usually in the vertical plane. And this incline plane is moving in a wheel fashion where the input force comes from the axle of the wheel. Now the force can be something other than just brute physical force. Propellers are usually driven by gas motors and fans by electric motors. Either way, the force vectors are the same: the rotating propellers get their force from the axle in the vertical plane and transfer the force to the air (or water) in the horizontal plane. It is easy to only look at the air flow, which goes in the opposite direction to the propeller frame [vindicating Newton] but in the bigger picture the initial force comes in through the axle which is NOT opposite to the air flow.

mousetrap The mouse trap is another good example, but this time we need to look at the trigger mechanism. When you cock the trap, you store a large amount of energy in the spring. With a much smaller force, the mouse releases the stored energy, which comes from a different direction than the mouse force. Triggers are know for being force multipliers, which violate the 3rd law in two different ways, NOT EQUAL in amount and NOT OPPOSITE in direction.

jet engine At the pinnacle of modern engineering is the Jet Engine. This is a scaled up fan, going from ounces of thrust to horse powers of thrust. This example of a device that moves the ambient fluid to get the thrust is if the analog we need for a space engine. Remember, the input force is at right angles to the thrust, turning the turbine shaft.

gyroscope The last example finally gives us a clue about the space engine. The toy top, like a gyroscope, shows us precession when the top slows down. This gyroscope shows us the same precession when it is laid on its side. This looks like an output force without any input force. But the circular motion is really powered by the force of gravity pushing down on the gyroscope. The larger the angle from vertical, the larger the precession force.

Eric Laithwaite and Alex Jones gave us these tantalizing clues 35 years ago.
Apple QuickTime is required to view this video clip.

What We Have Learned

out-of-box The important thing to notice is Newton’s 3rd Law is NOT really a limiting factor after all.

And we should keep in mind that historical pronouncements of physical limits have all failed the smell test.

So the Sky really is the Limit, OR not.

Norman Silliman, January 2012

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