The moon

waxing - moving toward a full moon.

waning - the moon is decreasing in size, moving from the Full Moon towards the New Moon.

Moon phases.

gibbous -  having the observable illuminated part greater than a semicircle and less than a circle

crescent - is part way between a halfmoon and a new moon, or between a newmoon and a half moon.

how the moon affects ocean tides.

lunar cycle= Metonic cycle, which means a cycle of 235 synodic months, very nearly equalto 19 years, after which the new moon occurs onthe same day of the year as at the beginning ofthe cycle with perhaps a shift of one day,depending on the number of leap years in thecycle.

1 lunar cycle =29.53059 days

Earth's Seasons/Eclipses

Nicolai Copernicus (1473-1543) radically changed our understanding of astronomy when he proposed that the sun, not Earth, was the center of the solar system. This led to our modern understanding of the relationship between the sun and Earth.

Nicoial Copernicus

We have seasons because the Earth rotates on an axis that's titled in its orbit. The 23.5 degree tilt causes the different hemispheres to be at different angles to the sun at different times of the year.

In winter, the sun is closer to Earth, but it isn't warmer. It's because the earth's axis is tilted.

During the summer, the sun's rays hit the Earth at a steep angle. The light does not spread out as much, thus increasing the amount of energy hitting any given spot. Also, the long daylight hours allow the Earth plenty of time to reach warm temperatures.

During the winter, the sun's rays hit the Earth at a shallow angle. These rays are more spread out, which minimizes the amount of energy that hits any given spot. Also, the long nights and short days prevent the Earth from warming up. Thus, we have winter.

Lunar eclipses

There aren't lunar eclipses every month because the Earth, Sun and Moon are not in the same orbital planes. The Moon orbits the Earth in a slightly tilted manner, thus most of its orbits it either passes above or below the shadow of the Earth, or passes above or below the Sun, thus preventing an eclipse.

the causes of eclipses.

We have day and night because the Earth rotates. It spins on its axis, which is an imaginary line passing through the North and South Poles. The Earth spins slowly all the time, but we don't feel any movement because it turns smoothly and at the same speed.

Why we have day and light.


equinox - the time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length (about September 22 and March 20).

solstice - either of the two times in the year, the summer solstice and the winter solstice, when the sun reaches its highest or lowest point in the sky at noon, marked by the longest and shortest days.

equinox and solstice