[^^Back to the TIME-LINE]
Relativity
See also:   [Literary Terms] 
           
Relativity

So, as it turns out "relativity" just didn't spring ready-made
out of the box, or, errr off the rack.

First off Galileo had noticed that if you were in a very 
quietly moving ship and couldn't look out a port hole
you wouldn't be able to tell if you were moving or not.
This is refered to as the principle of Galilean Relativity.

Come the great ages of discovery culminating in the 1850's
when EVERYTHING CAN BE KNOW IS KNOWN. The great theories 
of science fell into place and inventions (by the century's
end) as the likes of which had never been seen:

    Railroads & staem engines
 
    Fire Trucks with steam pumpers (1863) that could put out
    a fire on the FIFTH floor of one of the new high-rises!

    Telegraph, Telephone,

    The Electric Light,

    Anesthetic for surgery,

    Unlimited Rice Pudding!!

So, only a few loose ends had to be tied up. In fact Einstein's
parents didn't want him to study physics since it was an almost
dead science (sort of like studying Latin and Greek ;). 

Only a "few" problems remained and one of thse was to get a 
good way of "geting at" the problem of the propagation of
light. In once sense it behaved like a particle; eg, in the
way it scatters around corners, off dust particles, etc.  But
on the other hand it behaves *just* like a well-behaved wave;
eg, diffraction patterns, interference patterns, Moirre patterns,
-- more patterns than you throw a prism at!

And that was worst of all: The splitting up of white light
into the rainbow of colours (and Newton's bril idea of then
using a SECOND prism to re-combine them back into PURE white
light) -- both the PARTICLE and WAVE theories could adequately
explain that.

So, it had to be figured out:

  If light was a particle, then it just zinged here and there
  like any other good particle; well, other than the electron
  there weren't any OTHER particles - lots of speculations.

  If light was a wave, ah ha! Then it must have a MEDIUM to
  travel in. Sound waves got air, water waves got well, water.

So, the search was undertaken by many - notably by two chaps
in 1893:  Albert Abraham Michaelson and E. W. Morley - to try
and measure this wave effect.

How to do it?  After all, when Galileo had one of his assitants
climb to the top of a distant hill and he climbed up another
and they tryed to flash their lanterns to measure the speed of
light, he later sed, "If it's not infinite; then it's simply
to fast for us to measure it." - not an exact quote.

The problem comes down to a simple idea:  Swimming across or
along with a river. This is a *classic* problem for students
of elementary physics (not to be confused with students of
elementary partical physics or elementary students for that
matter, or for... Alas; i, digress).

Say you have two twin swimmers (call them "D" and "F").

One is going to swim across a river (moving at speed, c,
- c for "current") and then back. Say the river is exactly
50 metres across (that means a standard Olympic effort for
the "100 metre" free style ;).  This will be "D".

The other swimmer is going to swim from a dock up the river
and then back down (or depending on how things go start 
swimming DOWN river and then back up again). This will be
"F".

Both swimmers will swim with the same constant speed, 
v (for velocity).

Now let's do one of Uncle Al's "thought experiments".

We know that D will have to sort of point up-stream
to make it straight across - this means (pull out the
old Pythagorean theorem here) D will have to travel
along the diagonal IN JUST THE RIGHT direction so that
the current (c) plus D's velocity (v) will cancel out
and the NET PATH will be directly across. Coming back,
simply do the same thing - follow a diagonal into the
current. 
 
Note that if D doesn't do this, he will simply end up 
WAY down stream.

Now, we come to F. Having done his warm ups (checked 
for wind chill, light reflecting off of the water's
surace, and being distracted by several ducks) he 
sets off. Swimming up stream the 50 metres (thinking
to use the current to speed him back to the finish 
line).

Now as it turns out that F should always beat D because
of the diagonal thing.

Well, sort of. 

What if the current of the river, c, is greater than v?

Then, no matter what F will simply drift further and
further down stream and NEVER reach the 50-metre mark
to turn around and begin swimming down stream.

But, on the other hand if F "tacks into the current"
- much like a sail boat", he can almost always reach
the other shore and then return back again.

We assume that neither D nor F "get tired" - what ever
that is!

Thus, it's possible to figure out:  WHAT IS THE CURRENT's
SPEED, v, by comparing D's and F's "time of flight" - er,
ahm "time of swim".

So, it turns out that the Earth (moving as it does around
the sun - see Copernicus, Tyco Brahe, and of course Johanes
Kepler) travels a mere 30 km/sec - (about 65_000 miles per hour!)
around the sun. But, of course the speed of light is
 
   300_000 km / sec 

that is about (670 MILLION miles / hour - our about about
1_000 times faster than sound travels in air).

So, the speed of light is roughly 10_000 times faster than
the Earth's speed around the sun.

Thus, the current, c, casued by the passage of the Earth
thru the invisible aether of space is much less than v 
the speed of of light. And one of the main points about
this mysterious "space aether" as a MEDIUM for light
is that it doesn't move at all - it's sort of IS space.

So, it turns out if we can *somehow* set up the two rays
of light to be such that one travels WITH/AGAINST the
current and the other (perpendicular to it) travels
ACROSS the current (back and forth) - then we can use 
the simple MODEL of our two swimers (who have since
dried off, and have gone off to listen to some Jazz).

            And now for the payoff:

Michaelson and Morely didn't just create an experiment
they created AN UNBELIEVABLY ELEGANT EXPERIMENT!!! 
So, worried were they that the effect would be so
small (the ratio of the Earth's "current" is 1/10_000th
that of the speed of light). That they set up their 
light beams and mirrors and such on a huge round
slab, sitting in a large vat of Mercury (being liquid
and about 20 times denser than water it would take
a LOT to shake it up as the experiment was run).

They even did the experiment at NIGHT so that passing
horses and carts wouldn't create extra vibrations.
They could then rotate the whole thing around thru
every possible angle.

After all, there was no reason to expect that the 
Earth was in any particular orientation to the aether
field. But, as it turns out there was never ANY difference
no matter which angle they measured.

Zounds!!!

Well, after due inspection of the equipment, and many more
repetitions (and by other scientists around the world), the
THEORETICAL scientists were quite up-set.

After all - LIGHT HAD TO BE EITHER A WAVE OR A PARTICLE.
And this clearly didn't even show that a wave acting like
a well-behaved swimmer.

The KEY was that Michaelson and Morely had used the SAME
beam of light crossing itself and thus *supposedly* 
self-interfering just like any other light beam with a
diffraction grating, a prism, etc. Thus, it SHOULD act
like a wave.

Finally, another chap, Hendrik Antoon Lorenz came up with 
some equaions (which are based directly on the swimmer's 
algebra/trig eqautions) and sed, well if this is true, 
then that's true, but on the other hand if it isn't true, 
then well, what???? 

In other words, he broke it all down
and said that the result simply couldn't be fit into the
equations - THEORY and EXPERIMENT clashing; just like
happened with Radioactivity (unknown at the time) and
Darwin's time line for evolution - but, that's another story.

A lot of theoretical physicists grumbled, but they couldn't
fault the experiment and Lorentz was well respected (he
was one of the first to suggest that ELECTRONS existed
which J.J. Thompson and Ruthererford were now getting
around to studying at Cambridge; so what's your major?
Oh, i'm studying art history, how about you? I'm studying
electrons. ; blink blink ).

So, it was all laid out, and of course we know the rest of
the story. A part-time patent clerk working in the Zurich,
Switzerland, Terra patent office often day dreamed of
physics. And as he was riding the trolly to work (or so
as i heard the story) he would often see motor cycles 
(or motorised bicycles as they were known in those days)
zooming past *faster* than the trolly. And of course it
finally came to:

   What would the world look like if the light coming
   from behind me could never catch up - like the 
   swimmr (F) whose velocity, v, was less than the
   current, c - see how quickly algebra creeps into
   the act?

If the trolly suddenly lurched forward faster than the
speed of light, then when you looked back - everything
there would VANISH - the light couldn't catch up. And
what about the motor cycle?  It was going even faster.
and, and, and, and.

Well it turns out that (and Newton had only "tossed off"
a slight remark about it) that everything depended on
TIME.

And time was the joker in the deck. Time wasn't absolute.
Time depended not only on where you were, but how fast
you were moving.

And not to mention the mass (weight) was involved as well.

The worst thing is that the "the little paper" (in 1905) by
Einstein didn't use much more than basic high-school maths
(algebra, geometry, and a smidge of trigs) and it was based
mainly on two in-controvertable facts:

    Lorent'z thorough analysis of the motion problem.

    The Michaelson Morely experiment.

and then a rather curious little equation  E = m c^2
popped up.

The worst was yet to come of course, the idea that time
WASN'T absolute (not to mention HOW the photon? does the
MASS change) outraged quite a few.

One rather famous and (again well-established) physicist
Ernest Mach wrote an entire paper which showed how this
upstart Einstein (despite the fact that he HAD worked
on several important *experimental* problems - notably
the photo-electric effect) couldn't be right.

Mach's beautiful paper is wondrous beyond words. And the
odd thing is that it is ABSOLUTELY true. It refuted Uncle
Al's paper and of course that meant that TIME and MASS
were still ABSOLUTE and in-vioable.

In fact Mach's formulas explain "breaking the sound barrier",
trans-sonic jet design, etc - the so-called "Mach numbers",
eg, Mach I = speed of sound, Mach II = twice the speed of
sound, etc.

Only prob was:  No aether.  That's what the Michaelson/Morley
                            experiment said.

Sound needs a medium (air for example); light doesn't.

And then oddly enough, the Nobel Prise committee awarded in
the same year (1905) the prise of Physics to Albert Einstein
(for his work on the PhotoElectric effect - relativity was
way too controversial and *technically* didn't exist; unless
you believed Einstein's paper).

The Nobel prise in Physics to *that* patent clerk? Sort of 
a "keep going, lad!" encouragement - those Swedes' been 
known to do that, Martin Luther King, Al Gore - must be 
the climate that keeps their minds so clear when others 
seem to lose it.

Well, i've waxed a bit poetic here, hope you enjoyed the
show - pay as you leave (as always).

Now the funny thing is that at the first Solvay Conference in
Physics, Madam Curie sits centre stage, with Einstein off
to the side. At the second Solvay Conference, a few years
later, Uncle Al sits in the place of honour.

Well, for scientist and engineer types i remind you to 
take responsibility for your work. Einstein was to remark
later that if he had known that his equation would just
some 40 years later lead to the deaths of people, that he
wouldn't have become a physicist - but would have become
a gardner and studied the violin more assiduously.       


(nite all; happy Solstice 2007/2008)
-- Frank.

OH YES, i almost forgot:  Next time don't forget to bring 
        your Quantum Singularities to class, we'll be 
making universes.