Today is the Winter Solstice, meaning that today will be the shortest day (and longest night) of the year in the Northern Hemisphere. What you may not know, however, is that tonight will also be the longest night in the history of the Earth.
The reason for the Winter (and Summer) solstice is because of the way the Earth is tilted on its axis, MSN explains. The Northern Hemisphere is currently pointed away from the sun, meaning that it’s winter here, and we’ve reached the mid-point in our journey. After today, as the planet continues its orbit around the Sun, the days will steadily start increasing in the Northern Hemisphere. Six months from now, when the Northern Hemisphere is pointed toward the sun, it will be the Summer Solstice, and the longest day of the year.
And for Inquisitr readers in the Southern Hemisphere, the whole thing is reversed.
But tonight will not only be the longest night of the year, but it will also be the longest night in the planet’s four-billion-year history. Science blogger pointed this out on his blog. The reason, Schultz explains, is that the rotation of the Earth has been steadily decreasing throughout its existence, to the tune of a few millionths of a second every year. That means that in your lifetime, the Earth will gain about two thousandths of a second, give or take.
Although that small a period of time means little to casual observers, to scientists it’s actually a rather big deal. To keep our clocks and calendars in sync with the universe’s system of timekeeping, sometimes a leap second has to be added. It may seem trivial, but in 2012, a leap second caused several websites to crash, according to this Inquisitr report.
We can thank the Moon for our ever-increasing winter nights. As the Moon pulls on the oceans, causing tides, it also causes a bit of friction, slowing down the planet’s rotation. A few millionths of a second here, a few millionths of a second there, and over the course of four and half billion years it adds up; scientists estimate that a day on the Earth has gone from six hours early in its existence to the 24-hour-day (give or take a few millionths of a second) we experience now.
So when you go to bed tonight, if you live in the Northern Hemisphere, keep in mind that tonight won’t only be the longest night of the year, it will also be the longest night on Earth in your lifetime, or any other lifetime. Until next Winter Solstice, that is.
[Image courtesy of: NASA]