Christmas Countdown, Sunday #2

Day 10

Sunday’s theme is a reminder that there are more holidays than just Christmas in December — or in the winter in general, so we’ll be going to another continent for this one. Now, why are there so many holidays this time of year?

Simple. Astrophysics.

The very basic version of this is that the Earth rotates around its axis, which you can imagine as a stick that goes from its north to south pole. (Illustrated version available here.) The Earth is perfectly happy to rotate around this axis at a rate that gives us one revolution per day. While the Earth rotates around its axis, it also orbits the Sun, and this takes about 365.25 days (which is why Leap Years exist, but that’s not relevant here.)

Now if the axis were straight up and down — meaning that the equator was exactly level with the Earth’s orbit, we’d have no seasons and all days would be the same length. However, it’s not. It’s tilted about 23 degrees. This means that as the Earth goes around the Sun, the angle at which light hits it changes. On the first day of spring and first day of fall (in the Northern hemisphere), the axis is straight up and down relative to the orbit, so day and night are of equal length. As spring progresses into summer, the axis (in the north) tilts toward the Sun; from fall into winter, it tilts away. Tilting toward makes days longer; tilting away makes them shorter.

In winter, the days become the shortest of all, and the winter holidays, like Christmas, tend to happen right around that longest night of the year, which is the Winter Solstice, generally around December 22nd now, but a few thousand years ago it was closer to the 25th.

But the salient bit is this: Once the solstice comes and goes, the days after that start to get longer, light returns, and the world is eventually reborn in spring. All of these winter festivals are partly a way for communities to come together at the darkest and coldest parts of the year, and partly a way to remind them that it’s going to get better soon.

Which brings us to Diwali, which happened in mid-November (in America) this year, although it’s a holiday celebrated by Hindus, Sikhs, Jains and some Buddhists around the world. Basically, it celebrates the triumph of good over evil, and prominently features, well… lights, since it’s the festival of lights. But it definitely fits the winter theme, and again you can see how astronomical realities can dictate social conventions. When the year gets dark, we celebrate the fact that the light will always win and return.

Don’t forget to check out the previous post or watch the next.

Whole lot of shaking goin’ on?

(Warning: Betteridge’s Law alert in effect.)

Damn. Puerto Rico has been getting pounded by quakes over the last month to the point that they have visibly changed the landscape. Why so many earthquakes? Well, as they say in real estate, it’s all about location, location, and location. The island happens to be situated on top of or next to various tectonic plates and mini-plates, and it’s the collision of these pieces of the Earth’s crust that cause quakes in the first place. Well, the ones that aren’t man-made, anyway.

Puerto Rico isn’t alone in this, either. A look at significant earthquakes over the last 30 days shows the image of a very unsettled Earth. Now, it would be easy to buy into an interesting astronomical fact being the cause. That is, the Earth reaches its closest point to the Sun, perihelion, in January. This year, it was January 4th, with the centers of the Earth and Sun being only about 91.4 million miles apart. On July 4th, they will be at their most distant, at about 94.5 million miles.

Now, true, that’s only a little over a 3% difference, but that distance is about 390 times the diameter of the Earth, and enormous masses are involved on both ends. Perihelion is also the point in the Earth’s orbit when it reaches its maximum velocity, which is what flings it to aphelion, where it slows, reaches its minimum velocity, and comes flying back into a smaller orbit, which the Sun slingshots back out. Lather, rinse, repeat.

Of course, the difference between maximum and minimum velocity is only about sixth tenths of a mile per second, but, again, we’re dealing with some pretty big objects here. And, anecdotally, I can tell you that the biggest earthquake I’ve ever experienced was in January, and so was Japan’s, a year to the day later, and now Puerto Rico is shaking apart, and it must be connected, right?

Right… except that it’s not. Earthquakes are not driven by orbital mechanics or the weather or any other factors like that, and any belief in “earthquake weather” or “earthquake season” are pure confirmation bias and nothing more nor less.

However… there’s one thing to keep in mind about this time of year. We are closer to the Sun, and so get more heat from it, right at the time when it’s winter in the Northern Hemisphere, but summer in the Southern Hemisphere. And why is that the case? Because of the way the Earth is tilted. Winter is the season when its axis is titled away from the Sun. Summer is when it’s tilted toward. Spring and Fall are the seasons where the axis is mostly straight up and down.

So… in the Northern Hemisphere, we get winter when we are closest to the Sun and summer when we’re farthest away. In the Southern Hemisphere, it’s exactly the opposite, and this is where we can see events in our solar system having an effect down here. Mainly Australia is burning.

Why? Climate change, hotter temperatures, drier forests, extreme weather (thinking thunderstorms with lightning that can start a fire), and human elements, although far from the “200 arsonists” dreamt up by the anti-climate change crowd. More like 24 actual arsonists, and then a bunch of idiots who may or may not have started fires, but at least did something that might have. And, anyway, claiming that arson and accident don’t add to the concept of anthropogenic climate change is a bit of a stretch. Humans did it? All that smoke is going to screw up the environment. And the burning would have stopped a lot sooner if the hotter climate hadn’t pre-baked the forests.

But… it’s hard to avoid confirmation bias when the earthquake alert app on my phone has been ridiculously busy since at least January 4th. The good news is that it’s easy to survive a quake with warning, and if you’re not living in buildings basically made out of mud, stone, and hope.

Just remember this: A) Do NOT get into a doorway. That’s outdated Boomer advice. Instead, squat down next to a heavy piece of incompressible furniture, like a sturdy armoire or a sofa, or barring that, right next to your bed, on your knees, rolled over, hands covering the back of your neck and head.

Once the shaking has stopped, if you can, grab your loved ones and go-bag (you have one, right?) get outside, shut off your gas if necessary, and escape to shelter, which could be your car if it wasn’t smashed flat in the collapse of a Dingbat style apartment. People, really, don’t live in them. Also try avoiding buildings that are four to eight stories tall, because they tend to sway at resonant frequencies in sync with seismic waves, and so sway harder and collapse more often.

The good news is that in a lot of places prone to earthquakes, things have been upgraded to a ridiculous and safe degree. The bad news? In a lot of places they haven’t.  Fun fact: Most of the U.S. and Canada reside on a single tectonic plate, so are not naturally susceptible to earthquakes. Not fun fact: Fracking completely fracks with that, and creates seismic events (aka earthquakes) in places that they should not be. Less fun fact: the tectonic plate with a lot of Southern California and half of the Bay Area is not the same one as the rest of North America.

Consequently, while people in other parts of the country grow up dreading tornadoes or floods, earthquakes have been my lifetime bugaboo. Good news, though. I’ve survived 100% of the ones I’ve been in… and I’ve accepted the fact that, for now, they are 100% unpredictable.