Astronomy: Moon Phases, Eclipses, Time Scales, and History

Flashcards cover moon phases, timing in a lab model, synodic vs sidereal months, eclipses (solar and lunar), orbital inclination, transits, historical models, and basic relativity notes mentioned in the lecture.

What are the four primary lunar phases in order?

New Moon, First Quarter, Full Moon, Third Quarter.

In the lab model, how many hours is the Sun up each day?

Twelve hours.

In the described simulator, when is the waxing crescent at its highest point?

3:00 PM (three in the afternoon).

When is the first quarter moon highest in the model?

6:00 PM (sunset).

What is the relative timing of the full moon with respect to sunset in the model?

The Moon rises as the Sun sets (timing not perfectly aligned, but this is the model’s relation).

For the third quarter moon, what is its highest time and its rise/set times?

Highest at 6:00 AM; rises at midnight; sets at noon.

In this view, what shape does the waxing crescent resemble?

The letter 'd'.

In this view, what shape does the waning crescent resemble?

The letter 'c'.

What is the length of a synodic (solar) month?

About 29.5 days.

What is the length of a sidereal (star) month?

About 27.3 days.

Why don’t solar eclipses occur every month?

Because the Moon’s orbital plane is inclined about 5.2 degrees to the ecliptic, so perfect alignment is rare and totality occurs only in a favorable position.

Define a lunar eclipse.

Earth passes between the Sun and the Moon, casting Earth's shadow on the Moon.

Define a solar eclipse.

The Moon passes between the Sun and the Earth; totality occurs when alignment is precise; partial or annular eclipses occur otherwise.

What is the penumbra in an eclipse?

The partially shaded region around the total eclipse.

What causes an annular eclipse?

The Moon is too far away to fully cover the Sun, leaving a ring of sunlight.

What is the Moon’s orbital inclination relative to the ecliptic?

About 5.2 degrees.

What is a transit in astronomy?

A planet passes in front of its star as seen from Earth, causing a dip in brightness; used to detect exoplanets (e.g., Venus transit).

What does the term 'wanderers' refer to in ancient astronomy?

Planets (from the Greek word planētes, meaning wanderers).

How did the geocentric model explain retrograde motion?

Planets were thought to move in small looping epicycles around a main orbit, creating apparent backward motion.

Who contributed to early astronomy with the concept of wandering planets and epicycles?

Plato, Aristotle, and Arabic astronomers (planets described as wanderers).

What is the relationship between space and time as discussed, and how does gravity affect time?

Space and time are intertwined; gravity causes time to run slightly slower (relativistic time effects) for objects in stronger gravity.

What alignment is required for a total solar eclipse?

The New Moon must line up precisely with the Sun and the Earth so the Moon’s shadow falls on Earth.

What is a transit and how is it used in exoplanet detection?

A planet passes in front of its star from our viewpoint, causing a dip in brightness used to detect exoplanets.

How does eclipse visibility vary geographically?

Totality occurs over a narrow path on Earth; depending on your location (e.g., Sept 7 eclipse visible in Australia/Asia but not New York), you may or may not see it.

What is the difference between astronomy and astrology as described?

Astronomy is a hard science; astrology is considered pseudoscience.