Spring 2008's vernal equinox (beginning) occurred today, March 20, 1:28 EDT (5:28 GMT) when the sun crossed the equator on its annual apparent journey northward from Capricorn to Cancer.

Poems can help explain difficult scientific concepts. This one deals with precession, a slow twisting of Earth's axis that causes the vernal equinox to occur ~20 minutes (one/third hour) earlier each year. This is because precession forces Earth to orbit only 35971/72o between successive vernal equinoxes - or 1/72o less than 360o, "the perfect mark." After 26,000 years (the precession cycle), Earth returns to the same location in its orbit where the cycle began.

An Equinox! An Equinox!
Springs up the vernal paradox.
One twenty-six thousandth less around
Than last the spot where Spring was found.

A seventy-second degree of arc -
Thus much we miss the perfect mark.
One-third more hour's time is past
Ere Earth its full ellipse elapsed.

Precession of the axial line,
The cause of Spring's haste ev'ry time.
Spring is always premature;
Arriving early, to be sure.

Precession secrets now divulge:
The Sun pulls on Equator's bulge
But fails to straighten up the axis --
Which can't respond to phototaxis.

Equator's tilt will always be
Ex-ecliptic, definitely.
Old Earth is tired and needs a nap,
It simply cannot close the gap.

Could we but lay hands one each pole
And push with strength of heart and soul,
We'd still no more affect the axis
Than stop inflation, death and taxes.

Julian Kane

Note: GMT (Greenwich Mean Time) is Britain's Standard Time on which Longitude is based. Phototaxis is what sunflowers do.