General Relativity

Once a Swiss carpenter took a strange fall.

He fell off a building that stood two stories tall.

The man was quite lucky; it couldn’t have been planned.

He ended his fall softly in a pile of sand.

Describing his fall, he casually noted

that before him his tools had weightlessly floated.

In the city of Bern a young patent clerk

read of the fall and sat up with a jerk.

The happiest thought came to him that day;

for the falling carpenter gravity had gone away.

The Equivalence Principle, he knew he could claim,

says that gravity and acceleration are identically the same.

He worked out the math and discovered something new:

Gravity takes spacetime and warps it out of true.

Mass-energy distorts spacetime in a subtle aetherial flow

and warped spacetime, in its turn, determines where matter and energy go.

Of ways to prove and verify that theory we have only one;

we need to study phenomena that pass close to the sun.

Mercury’s orbit swings around the sun with excess apsidal precession.

Einstein calculated the excess correctly in General Relativity’s finest expression.

We know that gravity manifests and exerts a force of attraction,

but on waves the shrinkage of space causes a kind of refraction.

So starlight flying past the sun through a tiny angle is deflected.

Newton and Einstein disagreed on how much: Einstein’s amount was detected.

Between two points a path gets longer as into the sun’s gravity it sinks,

putting extra kilometers between the points as space itself shrinks.

So a radio signal passing the sun won’t arrive on time, they say.

It will get where it’s going a trifle late because of Shapiro’s delay.

Into the wider cosmos Einstein cast his mind’s eye’s gaze,

seeking to discern the Creator’s esoteric ways.

His famous tensor equation, a work of mathematical grace,

would give a complete description of the entirety of space.

He worked out the description through a procedure highly demanding

and discovered that his equation described a space that was expanding.

Such a thing could not be, on that point he was emphatic.

Space could not expand: the Universe had to be static.

Then he made a mistake, what he called his greatest blunder,

and missed seeing the Universe born in a blast of luminous thunder.

But he got it right the first time; his theory did not have to be completed,

so from the theory the cosmological constant was permanently deleted.

Now the theory stands before us, elegant and clean.

It allows us to envision sights that no human eye has seen.

Looking deeper into the cosmos, the theory lets us recite

how a point-instant of Creation became a space full of galaxies and light.

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