Monthly Archives: July 2015

I have a new opinion of Italian justice

In 2009 there was a major earthquake in the town of L’Aquila in Italy. The next year six scientists along with a government official were charged with manslaughter for failing to predict the earthquake. The trial lasted more than a year and in the end all participants were convicted. The prosecutors asked for a four year prison sentence and the judge handed down SIX year terms. It took another two years before the scientists were acquitted but the guilty verdict for the government official  was upheld.

(Magazine – Smithsonian – June 2015)

Don’t get too close to that planet

Since tidal forces are much closer to a planet a moon that has an orbit too close to a planet will be pulled apart. This is called the Roche limit and it is about 2.4 times the planet’s radius. Outside that limit the moon can be held together by its own gravitational forces. The rings of Saturn are due to planets that were closer than the Roche limit so they were pulled apart by Saturn’s gravity.

(The Great Courses – Black Holes, Tides, and Curved Spacetime: Understanding Gravity)

Tidal locking in a planetary system

Tidal forces and internal friction are what caused the Earth’s moon to slow its rotation so that it is locked into keeping the same side facing the Earth. This same ‘tidal locking ‘effect is also seen elsewhere in the solar system where other large moons around other planets also only show one side to their planet.

(The Great Courses – Black Holes, Tides, and Curved Spacetime: Understanding Gravity)

Natural collection spots for asteroids

In an orbiting system of two objects like the Earth and the Moon there are stable positions where another object, like a satellite can remain in a fixed position in relation to the two objects. These are called Lagrange points and there are five of them. Imagine a line which intersects the Earth and the Moon. In our Earth-Moon system L1, L2 and L3 are located on the line. One is just inside the Moon’s orbit between the Earth and the Moon, another is just outside the Moons orbit on the other side of the Moon, and the third is on the other side of the Earth but just inside the orbit of the Moon. These are not very stable and any objects which are not exactly at this point will tend to drift. L4 and L5 are very stable points and they exist on the Moons orbit. One of them is 60 degrees in front of the Moon and the other is 60 degrees behind the moon. There are small asteroids which exist at these points for some of the moons of Saturn. In the Jupiter-Sun system the L4 and L5 points thousands of small asteroids have gathered and remain in Jupiter’s orbit. These two groups of asteroids are called Trojan asteroids and the named asteroids just in front of Jupiter are usually named for Greeks and the named asteroids behind Jupiter are named for Trojans.

(The Great Courses – Black Holes, Tides, and Curved Spacetime: Understanding Gravity)

Powerful Number 2 (or maybe 1.5)

Through out the period when Octavian (yet to be renamed Augustus) was gathering power he was assisted by two boyhood friends Agrippa and Maecenas. Agrippa was actually the general behind almost all of Octavian’s military victories and when Augustus became the priceps (first citizen) Agrippa had almost all the of the same powers as Augustus. They would each go to parts of the empire where they were needed and each had the authority to do whatever was needed.

(Book – Augustus: The Life of Rome’s First Emperor – Anthony Everitt)

Ever heard of the Rings of the Asteroid Belt?

Most people are aware that there are many rings of Saturn that are separated by gaps such as the Cassini division. These rings and gaps are caused by ‘gravitational resonance’ between Saturn and many of its moons which can each be responsible for a ring. This same principle is in effect between the Sun and the planet Jupiter which causes the same kinds of ‘rings’ and ‘gaps’ that occur in the asteroid belt between Mars and Jupiter.

(The Great Courses – Black Holes, Tides, and Curved Spacetime: Understanding Gravity)

Slower than watching grass grow

The calculation for the force of gravity was first calculated in 1798 by Henry Cavendish. Using brass shot puts hanging on an intricate balance he was actually able to calculate the gravitational constant by measuring their movement due to their gravitational attraction to each other.

(The Great Courses – Black Holes, Tides, and Curved Spacetime: Understanding Gravity)

The Second Triumverate

After Julius Caesar was murdered there were basically three groups vying for power. The Republicans lead by Brutus and Cassius were opposed by Mark Antony who saw himself as the political inheritor from Caesar, and the teenager Octavian the who had just been named in Caesars will as his adopted son and inheritor of this estate. All three powers fought against one at different times until Mark Antony and Octavian finally forged an alliance to defeat the Republicans to avenge Caesars murder and then form the second triumvirate (with Lepidus who was by far the lesser of the three). After a lot of maneuvering and plots Antony and Octavian eventually decided to really try and form an alliance to rule Rome and Mark Antony married Octavian’s sister Octavia. It was a lavish wedding and Antony had a coin struck with his and his new wife’s heads. This is the first time that we know about where a woman appeared on a Roman coin.

(Book – Augustus: The Life of Rome’s First Emperor – Anthony Everitt)

Let’s write a hit song!

There are a lot of songs that weren’t exactly original. Because the originals are so old they are part of the public domain and can be used without fearing a lawsuit. “There’s a place for Us” is from Beethoven’s Emperor Concerto second movement, “I don’t know how to love him” is from the second movement of Mendelssohn’s Violin Concerto,  “Don’t sit under the apple tree” is from an old folk song, “I can’t help falling in love with you” is from a 1790’s French song called “Plaisir D’Amour”. There are many other examples as well.

(The Great Courses – Great American Music: Broadway Musicals)