"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."
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 with this 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:
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: