April 17 - Happy Birthday, Giovanni Riccioli

Posted on April 17, 2021

Key Points

This is an update of my post published on April 17, 2010:

Born on this day in 1598 in Italy, Riccioli became an astronomer. He and another astronomer he worked with, Francesco Maria Grimaldi, carefully studied the moon using telescopes.

Not only did they study the moon, they drew a map of it and named many of the craters and other features they saw. We still use the lunar names Riccioli and Grimaldi assigned today.

During Riccioli’s life, the Catholic church (including the Jesuit order) stood officially opposed to Copernicus’s idea that the earth traveled around the sun rather than vice versa. (Do you remember what happened to Galileo?) Riccioli, who was a Catholic priest of the Jesuit order, apparently took the church’s stance as his own and even argued against the ideas of Galileo and others in a book he published in 1651.

But did he really believe that the Earth stood still and the sun orbited around it? Or did he just say that so that he wouldn’t be thrown out of the church or otherwise punished?

We will never know. But we do know two things:

First, Riccioli complimented Copernicus’s hypothesis for being simple and elegant, even while he was arguing against it.

Second, Riccioli and Grimaldi named a large crater after Copernicus, and they named other important features after Copernicus’s supporters, including Galileo. They even named craters in that same general region after themselves…

Copernicus Crater is the bright one
in a relatively uncratered portion of the
Moon.

Some other craters they named after other Jesuit astronomers, and these all lay in a different part of the moon, near Tycho.

Tycho Crater is the bright one with
all the rays extending from it.

Some say that these two things indicate that Riccioli really did believe the heliocentric hypothesis that states that the sun, not the Earth, is the center of the solar system.

Seeing Doubles

Another of Riccioli’s contributions is that he realized that the star Mizar was really two stars, Mizar and Alcor. We now know of many double stars, which don’t just appear to be nearby in the night sky, but which actually are near each other and which, in fact, revolve around each other. If you live in the Northern Hemisphere, you should be able to spot the Mizar / Alcor star system – it’s the middle “star” in the handle of the Big Dipper.

Picturesque Lunar Names

Earlier lunar observers had named the flat-looking dark plains of the moon maria, or seas, even though they aren’t water at all! Instead of naming the seas after famous scientists, as they named the craters, Riccioli named them after moods, such as Tranquility, Serenity, Crises; or after weather conditions, such as rain (Mare Imbrium), clouds (Mare Nubium), and cold (Mare Frigoris). All these names were in Latin.

The circle marked “Landing” in the Sea of
Tranquility is the spot where Apollo 11 landed
and became the place where humans first
walked on another world.

Whose names?

We often find that the first person to discover something gets to name it, but apparently several people named the moon’s features before Riccioli and Grimaldi did so—and yet these earlier names didn’t catch on. In 1645, Michel Florent van Langren named most of the visible features of the moon, many of them honoring a Catholic “royal” of his time or a Catholic saint. In 1647, Johannes Hevelius published his own map, which ignored all the names suggested by van Langren. Hevelius’s names were names from places on the Earth, especially place names from the ancient Greek and Roman world. A few years after that, when Riccioli and Grimaldi named the same features, THOSE are the names that stuck!

What’s in a name?

People throughout history have told stories of various goddesses of the moon, and some of the goddess names are used today in modern words. Match the numbered items with the lettered items below:

1. Selene
2. selenology
3. selenography
4. selenium
5. Luna (match with two items)
6. lunar
7. lunatic (and loony)
8. Artemis
9. Diana

—————————————–

A. the study of the moon
B. a chemical element
C. Roman version of Artemis
D. early Greek goddess of the moon
E. having to do with the moon
F. name of Earth’s moon
G. insanity, crazy (it used to be thought that the moon caused madness)
H. Roman version of the goddess Selene
I. the “geography” of the moon
J. later Greek goddess of the moon and the hunt

ANSWERS:

1. D
2. A
3. I
4. B
5. F and H
6. E
7. G
8. J
9. C

Phases of the moon

Can you see a full moon tonight? Without waiting for nightfall or using Google, is there a way to find out?

Hopefully, you looked at the moon last night, and the night before. People who make frequent observations know what to expect in the future, and people who routinely look up at the sky are likely to spot beauties such as “falling stars” and lens-shaped clouds and halos around the moon.

And they know where and when to look for the moon, because they know if it is waxing (with the illuminated portion getting larger and larger, every night), or waning (with the illuminated portion getting smaller and smaller, every night).

Many printed calendars mark “full moon,” “new moon,” “first quarter” and “last quarter.”

Here is a free online site that shows you the phases of the moon for today, tomorrow, yesterday, and every day!

Learn more about the moon

Universe Today has gathered together some interesting moon activities for kids. Make your own craters, figure out your moon weight, listen to a podcast, and more…