An even more horrible azimuth gag

#whatssofunnyaboutazimuths

#azimuthgag

Every little star in the sky

An azimuth compass shows 360° starting with 0/360°at due North.

Who wants to talk about Ptolemy some more? I told you about how people back then thought Earth was at the center of the universe and all the stars and planets revolve around her. This is called the geocentric model. The geocentric model has the stars on a humongous sphere. Good ol’ Ptolemy calculated the positions of all the stars and planets in the sky. He mapped exactly their azimuth and altitude.

Imagine you’re standing outside on a clear night and can see all the way to the edge of the sky—no trees or buildings in the way. That’s Earth’s horizon (we usually don’t see the horizon unless we’re in a flat desert or a big lake or ocean). You’re standing in the middle of a big circle, the base of a big dome. Directly above your head is the zenith, the center of the dome above. You can use a compass to find the direction of a star’s position—that’s its azimuth.

Using a cross-staff to find a star’s altitude.

You’ll need another device to figure how high that star is from the horizon—you work out the angle with your eyeball being the center point, the horizon at zero and the zenith at 90 degrees. A cross-staff is something Ptolemy may have used. You sight along the staff and point it in the star’s direction. Move the crossbar until it touches the horizon at the bottom and the star at the top. The position of the crossbar on the staff marks the angle of the star’s altitude.

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In case you hadn’t remember’d—

(Originally posted Oct 25, 2013)

Happy St Crispin’s Day!

But we in it shall be remember’d;
We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother; be he ne’er so vile,
This day shall gentle his condition:
And gentlemen in England now a-bed
Shall think themselves accursed they were not here,
And hold their manhoods cheap whiles any speaks
That fought with us upon Saint Crispin’s day.Spoken by Henry; from William Shakespeare’s Henry V, Act IV Scene 3

Gang, this beautiful language is our inheritance—a gift to us from people long gone. Here is the entire scene. More info here. If you saw the Queen Elizabeth movie that came out a few years ago, you’ll remember Cate Blanchett in armor giving a speech to her troops just before they battle the Spanish. I assumed the screenwriters had been inspired by the King Henry speech above. Silly me, I got it backwards—in fact it was Queen Bess’ speech that had inspired Shakespeare.

Charlemagne & Pope Leo III from yesterday

Here’s the painting I did yesterday. Still a bit rough; needs some tightening up. Charles’ right hand doesn’t look like it’s holding the hilt of that sword. I have to figure out how to mount my camera (phone) so it’s not in the way when I paint. I kept bumping into it.

Charlemagne & Pope Leo timelapse

Here’s a little painting—you can watch as it gets painted. https://www.instagram.com/p/B3-HCj-gCVs/

It’s an image for this post.  Enjoy!

Ptolemy—why not take Ptolemy?

Ptolemy showing his geocentric model of the universe. That’s Earth in the middle.

We’re coming up on the Middle Ages, everybody! The Roman Empire has become the Holy Roman Empire—we’re still working on creating individual countries out of the territories of various tribes. The Christian Church has become a stabilizing institution. With Charlemagne’s help, religious centers—like monasteries—are also places of learning. Alcuin of York (Charlemagne’s right-hand man) designed an easier-to-read way of writing using capital letters and small letters instead of ALL CAPS!

Life isn’t easy for regular peasants, which is most people. It’s hard to make a living on a farm. Some people head to the towns to learn a trade. Sanitation isn’t so great and the bubonic plague is always just around the corner. It will be centuries before anyone figures out that plague is carried by fleas.

It usually takes a long time for civilizations to accept new ideas. Even after Eratosthanes showed the Earth to be round, many people thought she was flat. Both educated and uneducated people believed that the Earth was the center of the universe and the Sun, planets and stars revolved around her. They thought of the universe as a giant sphere—a ball—with planets and stars stuck onto it. This sphere would be like clear glass. The word for this idea is geocentric—geo is a Greek word for Earth, centric means smack dab in the middle.

We get this idea from an astronomer named Ptolemy (TOE-leh-mee), who lived in Alexandria, Egypt (100-170 ad, we think). He improved on the basic geocentric idea. Ptolemy used math to place the stars in fixed positions on this big sphere. He observed that the planets didn’t stay fixed on the sphere, though, so they were called wandering stars and got their own smaller spheres that fit inside the big one. The Sun made its own orbit, a circle, called an ecliptic.

Here’s Billie Holiday singing “All of Me.”

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https://www.britannica.com/biography/Ptolemy
https://www.teachastronomy.com/textbook/The-Copernican-Revolution/Ptolemy-and-the-Geocentric-Model/