This time-lapse shows
the Sun only rises due east two days a year
You've been lied to.
This incredible time-lapse shows an entire
year's worth of sunrises condensed into 23 glorious seconds. And while the
colours and scenery are all breathtaking, what's really interesting here is
that the footage demonstrates something not many people are aware of - the fact
that the point at which the Sun rises (and sets) moves slightly north and south
with the seasons. In fact, it only rises due east two days a year.
This time-lapse was created by Tobias
Hoerburger, who took a photo looking due east over the German city of
Regensburg 10 minutes after sunrise each day between 21 March 2015 and 20 March
2016.
Coincidentally, just last week, astronomer and
science writer Phil Plait wrote about the vernal equinox (better
known as the spring or fall equinox), which occurred on March 20 this year, over on his Slate blog, Bad Astronomy.
He was explaining how those two days are the
only ones of the entire year when the Sun actually sets due
west, and rises due east, despite what you've been told throughout your
childhood. But he was lacking any long-term time-lapse footage to
demonstrate this effect in action - which is where Hoerburger stepped in withthis
incredible record of the Sun's motion throughout the year.
So what you can see in
the time-lapse is that, for the first sunrise, the Sun is
coming up due east, and then continues to move further north every morning
fairly quickly. Then it slows down, hits the June solstice, and begins to move
south again.
Eventually, it gets to the December solstice,
and reaches its most southern point, before moving back up to due east for the
2016 vernal equinox (which occurs September 22 this year).
This all happens because of the tilt
of Earth's axis as it orbits the Sun, Plait explains over at Bad Astronomy. And when
you think about it, this is probaby something you already instinctually knew,
but never really thought about too seriously. I mean, we all know the Sun
moves, but sunrise is just always due east!
So why does the Sun speed up and slow down as
it moves across its path for the year? Plait explains, referring to the sunset this time:
"The thing is, as the 'sunset point' moves north and south
over the year, it doesn’t always move at the same speed. At the equinoctes it’s
moving the fastest, and before the solstices it appears to slow down and stop
(solstice means 'the Sun stands still') before reversing direction. For the
mathophiles, the motion itself is a sine wave, and the speed it travels is the
derivative, a cosine."
So there you have it, the sunrise isn't as constant as you might
or might not have thought. But either way, you have to admit that it's even
more beautiful when you know the science behind it. And enjoy it, because
thanks to Earth's tilt, not everyone gets to: