Relativity

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In Germany, In the fall of Nineteen Hundred and Five

Albert Einstein revealed a theory that he worked to derive.

 

His paper in Septemberís Annalen der Physik revealed

the special Relativity he obtained when to logic he appealed.

 

Guided on his quest by a logico-mathematical muse,

he found that only two postulates did he need to use.

 

While contemplating his physics he conceived an idea sublime.

"Time is part of space," he said, "and space is part of time."

 

He devised the concept to which we must give deference;

spacetime consists of endless inertial frames of reference.

 

So on those ghostly picture frames he saw without a doubt,

two postulates and their consequences clearly all laid out.

 

Postulate I

The laws of physics are mathematically and logically the same

for observers in each and every inertial reference frame.

 

Postulate II

Maxwellís Equations told him that he could claim

for all observers the speed of light is always the same.

 

From those two postulates new knowledge we can gain

from imaginary experiments performed on an imaginary train.

 

Mathematically, effect by effect, we extend the logical relation

and cobble together the four equations of the Lorentz Transformation.

 

We know that logicís non-contradiction rule never ever fails;

so in both frames the trainís wheels must always stay on the rails.

 

From such a simple thought comes to us a great notion;

the measurements of lateral distances are unaffected by relative motion.

 

Between moving clocks Einstein inferred a strange relation,

and conceived the bizarre phenomenon of real time dilation.

 

From rail to rail a pulse of light goes forward and back.

The train makes a clock out of a length of railroad track.

 

For Einstein by the track on a sawtooth path the pulse does go.

Compared to the ticking of his clocks the trainís clocks are running slow.

 

Between two clocks on the train he conceived most sublime

the weirdest of all the effects Ė the offset of time.

 

At the center of a coach there flashes a bright light

and starts two clocks ticking in the middle of the night.

 

We know that simultaneously those clocks are going to chime;

equidistant from the light source, they started at the same time.

 

But the second postulate says that for Einstein by the track

the rear clock started earlier and the front clock appears set back.

 

Reality treats space and time logically in equal proportion,

so space, like time, displays relativistic distortion.

 

From front and rear of a carriage two mail bags were dropped.

The train didnít slow down; it simply could not be stopped.

 

Simultaneously the bags fell at the stationís approach;

their distance apart measures the length of the coach.

 

Einstein by the track said, "Think again. You couldnít be more wrong.

The rear bag fell first by an instant, so the coach appears extra long.

 

Even though we canít see the effect Ė itís a purely inferred notion Ė

length, like time, is dilated by relative motion.

 

Spatial offset, the analogue of temporal offset, adds little to our intellectual stock.

Itís merely the distance between two events measured on the very same clock.

 

Itís classical physics through and through. Thatís easy enough to see,

but on the list of Relativityís effects we know it must simply be.

 

Between length dilation and temporal offset there exists a truly strange linkage;

working together, upon objects they impose a relativistic shrinkage.

 

So length dilation and temporal offset working in mutual action

produce for everyone to see the Lorentz-Fitzgerald contraction.

 

Finally Einstein combined all the facts that he had learned

and saw before him the fantastic reward he had earned.

 

Of space and time he worked out their geometric relation.

He found four basic equations of relativistic calculation.

 

He gave us the means to interrelate what we measure,

the centerpiece of Relativity, a mathematical treasure.

 

Einsteinís train came to rest as it pulled into the station,

carrying the four equations of the Lorentz Transformation.

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