Vernal equinox: How dare they call it spring? (+video)

A dog wears protective glasses prior to the solar eclipse in Regent's Park in London Friday. Unfortunately, due to heavy cloud cover, the eclipse was not visible in London.

The vernal equinox, which marks the beginning of spring, is upon us.But that’s a tough sell when many parts of the US are still expecting more snow. And while there are other ways to define the seasons, none are very satisfying.

At 6:45 p.m. EST, the sun will shine directly on the equator, producing a 12-hour day for both hemispheres. Our planet reaches this point in its orbit twice a year – on the autumnal and vernal equinoxes. Ancient civilizations recognized this astronomical phenomenon as the ideal time to begin planting crops and raising livestock – in other words, the first day of spring. And to some degree, we still accept that notion.

But with the inclusion of leap years, there cannot be an exact annual date for the equinoxes. And because of Earth’s elliptical orbit, the length of each astronomical season varies. As such, it used to be difficult to compare seasonal climate data between different years. So in the mid-20th century, meteorologists campaigned for a new, simpler system. The National Climatic Data Center defined each season as an even three-month period – meteorological spring spans March, April, and May. So while the sun says spring sprung today, weathermen say it started almost three weeks ago.

But if you asked Boston’s snow-battered masses, neither factor would make a convincing argument for spring. Warm weather may be on the horizon, but that’s hardly comforting when forecasts continue to warn of additional snow. For most people, spring can’t be defined by orbits and climatological data. It’s a feeling – you know it when you see it. Sure, 50 degrees Fahrenheit would provide New Yorkers a welcome reprieve from frigid temperatures, but it would make for an unseasonably cold day in Atlanta.

So it may not be spring in the blooming-flowers sense, but astronomy buffs still have a lot to be excited about today. A total solar eclipse was visible from points in the North Atlantic this morning, and was streamed live for those in other parts of the world. And coinciding with the equinox, the moon will reach its closest point of orbit tonight, resulting in a “supermoon.” Seasonal pessimism aside, it’s an exciting way to usher in the “first day” of the season.