Introduction to Astronomy

Table of Contents

Intro to Astronomy
Definition of Astronomy
Electromagnetic Spectrum
Periodic Table
Astronomy Word List

Misconceptions
Questions

Archaeoastronomy
Equitorial Coordinates
Understanding the Seasons

Time & Its Measurement

Telescopes  

Solar & Lunar Eclipses

The Solar System

The Earth

The Moon

Mecury, Venus, Mars

The Outer Planets

Solar System Debris

The Sun

Evolution of Stars

Intersteller Matter

Sky Literacy








Popular Misconceptions in Astronomy    

     More Misconceptions about The Moon

The Moon has no Gravity

Any object which possesses mass (matter) has the force of gravity as a condition of its being. That goes for all matter: cars, baseballs, battleships, the moon, sun, planets, and all other objects found everywhere, regardless of whether they are large or small. The force of attraction felt by one object for another is directly proportional to the product of their masses and inversely proportional to the square of the distance to which they are separated. Isaac Newton put it this way: the force of attraction between two objects, F, is equal to G m1 m2/r², where G represents the universal constant of gravity; m1 and m2, the respective masses of the two attracting bodies; and r², the square of the distance between the center of the two objects. When comparing the acceleration of an object at the surface of the more massive body, m1, the equation simplifies itself to a = m1/r². The mass of the moon is 0.0123 of Earth's mass, while the radius of the moon is 0.2717 of Earth's radius. The acceleration of an object at the surface of the moon is 0.0123/(0.2717)² = 0.1667, or 1/6th that of Earth. The moon attracts objects at its surface with a force of 1/6 that of Earth. Therefore, the moon definitely has a gravitational field which is noticeable when an astronaut performs activities on its surface.

The Moon Appears Larger on the Horizon than when it is High in the Sky

This is called the Moon Illusion, and it is just your brain playing a psychological trick on your perceptions. When rising, the eye sees the moon against distant landscapes which may contain houses, trees, or mountains among many other things. Your brain knows that these distant objects would indeed look large if they were close to you. This psychological effect is transferred to the moon which is now made to appear bigger than reality by the brain.

The Blue Moon is really Blue

The blue moon is not blue at all, since the light which we see reflected from its surface is only sunlight. A blue moon is really the second full moon which can occur during a month's time. Since the phase cycle of the moon is 29 1/2 days, and a month has normally 30 or 31 days, blue moons occur very infrequently, about once every two to three years.

The Surface of the Moon is very Reflective

Look at the full moon in the night sky. It appears bright, in fact brilliant enough to read the headlines of a newspaper by its light. The true tonal gradations of the lunar surface are actually dark gray to nearly black, with an average reflectivity of only 7%. The extremes range from 3% to 30%. The lunar surface appears similar to a macadamized roadway. With about 93% of the sunlight absorbed by the lunar surface, the brightness of the moon is really a contrast difference between its dark surface and an even darker sky. That's why the moon appears so bright at night.

When the Moon is Full, Lunacy Reigns

There is no statistical proof from hospital or police records that people are crazier, or that more crimes are committed, or that more babies are born when the moon is full. However, every nurse or policeman will tell you that this simply cannot be so.