I'm finding this a very interesting discussion, since it illustrates how a
simple question (how current flows in a vacuum tube) quickly morphs into
much more profound issues once the surface is scratched. To me, that's the
way science progresses. Here are a few of my thoughts on comments raised by
some of our distinguished list members:
> So the Heisenberg Uncertainty Principle is still uncertain? I feel it's
> obvious once the process is measured, the process is changed.
> The main bang in my bag is gravity. What is it???
> 73 N7RT
I don't think there's anything obvious about the uncertainty principle.
Hardy is correct that measuring the property of e.g., the position of an
electron, always causes it to move a little bit. As he says, "once the
process is measured, the process is changed." True enough, but before the
uncertainty principle, it was always assumed that the "change" in the
process could be made arbitrarily small by using more an ever more sensitive
measuring instrument. The uncertainty principle says that there's always a
minimum change which cannot be made smaller, no matter how delicate and
sensitive the measuring device. In other words, the change is quantized, and
there's nothing obvious about that!
The uncertainty principle comes out of quantum mechanics, which says
that small objects, like electrons, are described by a probability wave, and
that the frequency of the wave is a measure of the electron's kinetic energy
(or speed). The peak in the probability wave is the most probable location
of the electron. To get any wave to peak up, however, you have to add
together waves of different frequencies, and the sharper the wave peaks, the
more waves have to be added together. It's analogous to the key clicks that
occur when a CW signal turns on and off too quickly. The sharper the keying
envelope, the wider the frequency spread of the key click. With the
probability wave of an electron, the sharper the peak, the broader the
spectrum of waves that have to be added together, and since the frequency of
a wave component corresponds to the speed of that component, then the
electron's speed becomes increasingly uncertain. In other words, the more
precisely you try to the position of an electron (or anything else), the
more likely you are to give it a large, uncertain speed.
Now, to gravity. Bill W6WRT asserts that
> "Einstein's description of gravity as a "distorting of space" is typical
[of a fixation on the math and losing > > sight of what is real.] Gravity is
simply a force which is poorly understood, not a distortion of anything."
Sorry to disagree with you, Bill, but actually gravity is very well
understood. Our understanding comes out of the general relativity field
equations, and the equations have been verified by experiment thousands of
times. Every GPS detector depends on the equations, as do precise time
bases, and measurements of light deflected by stars, and satellite
trajectories, and on and on and on.
Here's the intuitive explanation given in beginning relativity courses about
how a distortion of space can seem like an ordinary force. We live in a
three dimensional universe, but imagine a two dimensional flat universe,
which we can envisage as the surface of a large flat mattress. All motion in
our 2D universe then corresponds to moving around on the surface. Now place
two heavy bowling balls near each other on the mattress. The weight of the
bowling balls causes a depression in the mattress, which will cause the
balls to roll into each other. In other words, the distortion of the
mattress into the third dimension looks just like a force on the balls that
draws them together. It's the same idea in our 3D universe. The mass of the
earth distorts our 3D universe into a 4th dimension, causing masses to fall
toward the earth..
You may have heard recently about the discovery of gravitational waves,
predicted by Einstein. A friend of mine worked on the experiment for thirty
years, (He had a lot of help. More than a thousand scientists and engineers
worked with him.), and it's probably the most amazing experiment in the
history of the human race. Basically, when masses collide, they cause space
around the collision site to reverberate, like striking a gong, and ripples
in space radiate out from the collision at the speed of light. The
experiment detected the propagating gravity waves from two black holes that
spiraled into each other over a billion years ago, traveling more than a
billion light years to reach us. One of the cool things about the experiment
is that the colliding black holes spiraled into each other at an audio
frequency. The resulting gravity waves were thus in the audible range, and
to a listener sounded like an audio sound wave chirp. The two detectors,
which were spaced a thousand miles apart, each heard the chirp as the wave
passed by. You owe it yourself to read about this experiment, called LIGO.
Here's the website: https://www.ligo.caltech.edu/news/ligo20160211
One final comment, pertaining to the role of mathematics in physics. Bill
W6WRT is completely correct that math is just a method for describing the
laws of the universe, and he's also correct that physics equations can be
error-free mathematically, but still hugely wrong if they're based on faulty
premises or bad data. That's why all science ultimately rests on data and
experiment. By the way, the best theory in the world, in terms of how
accurately it explains real laws, is called "quantum electrodynamics." The
equations of the theory have been tested against experiment out to ten
digits, with no measurable error. Many people worked it out, but Richard
Feynman probably gets most of the credit. Heck of a smart guy.
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