The Star closest to our Sun is 4.5 light years away... ((A Light Year is the distance light travels in one year... Light moves at the speed of 186,272 miles or 300,000 kilometer per second...))

Our Sun is 30,000 light years from the center of the Milky Way Galaxy... So, the light that we see coming from our Milky Way Galaxy's center, left there 30,000 years ago...

The known Universe contains at least 1,000,000 billion of other Galaxies... There is no doubt that there are other vast Universes in existence... Absence of evidence is not the evidence of Absence...

The Milky Way Galaxy contains at least 400 billion stars...

We are living on a planet that is in a constant high speed motion around itself and traveling on its orbit around the Sun. The circumference of the Earth at the equator is 25,000 miles or 40,000 kilometers. The Earth rotates around its axis once every twenty-four (24) hours time, or one whole day and night.

Earth’s circumference at the equator is 25,000 miles or 40,000 kilometers, divided by 24 hours is the equivalent to over 1000 miles or 1609 kilometers speed per hour. Therefore our home, Planet Earth rotates around its axis at speed of over 1000 miles or 1609 kilometers per hour.

Multiply by the cosine of your latitude to see how fast the Earth is rotating where you are.

While Planet Earth is rotating on its axis at the speed of over 1000 miles or 1609 kilometers per hour, Earth is also traveling, revolving on its oval orbit around the Sun at the speed of about 67,000 miles or 107,200 kilometers per hour once every 365 days or one whole year.

Why do we have the four seasons?

As the earth spins on its axis, producing night and day, it also moves about the sun in an elliptical (elongated circle) orbit that requires about 365 1/4 days to complete. The earth's spin axis is tilted with respect to its orbital plane. This is what causes the seasons. When the Earth's axis points towards the Sun, it is summer for that hemisphere. When the Earth's axis points away, winter can be expected. Since the tilt of the axis is 23 1/2 degrees, the north pole never points directly at the Sun, but on the summer solstice it points as close as it can, and on the winter solstice as far as it can. Midway between these two times, in spring and autumn, the spin axis of the Earth points 90 degrees away from the Sun.

This means that on this date, day and night have about the same length: 12 hours each, more or less. Why should this tilt of the Earth's axis matter to our climate? To understand this, take a piece of paper and a flashlight. Shine the light from the flashlight straight onto the paper, so you see an illuminated circle. All the light from the flashlight is in that circle. Now slowly tilt the paper, so the circle elongates into an ellipse. All the light is still in that ellipse, but the ellipse is spread out over more paper. The density of light drops. In other words, the amount of light per square centimeter drops (the number of square centimeters increases, while the total amount of light stays the same).

The same is true on the Earth. When the Sun is overhead, the light is falling straight on you, and so more light (and more heat) hit each square centimeter of the ground. When the Sun is lower in the sky, the light gets more spread out over the surface of the Earth, and less heat (per square centimeter) can be absorbed. Since the Earth's axis is tilted, the Sun is higher when you are on the part of the Earth where the axis points towards the Sun, and lower on the part of the Earth where the axis points away from the Sun.

For the Northern Hemisphere, the axis points most toward the Sun in June (specifically around June 21), and away from the Sun around December 21. This corresponds to the Winter and Summer Solstice (solstice is Latin for "the sun stands"), or the midpoints of winter and summer. For the Southern Hemisphere, this is reversed.

For both hemispheres, the Earth is 90 degrees away from the sun around March 21 and then again around September 21. This corresponds to the Fall and Spring Equinox (equinox is Latin for "equal night"). Everyplace in the world has about 12 hours of daylight and 12 hours of night.

Why are sunrise and sunset not exactly 12 hours apart on the Equinox?

Day and night are not exactly of equal length at the time of the March and September equinoxes. The dates on which day and night are each 12 hours occur a few days before and after the equinoxes. The specific dates for this occurrence are different for different latitudes.

On the day of the equinox, the geometric center of the Sun's disk crosses the equator, and this point is above the horizon for 12 hours everywhere on the Earth. However, the Sun is not simply a geometric point. Sunrise is defined as the instant when the leading edge of the Sun's disk becomes visible on the horizon, whereas sunset is the instant when the trailing edge of the disk disappears below the horizon.

At these times, the center of the disk is already below the horizon. Furthermore, atmospheric refraction (or bending) of the Sun's rays cause the Sun's disk to appear higher in the sky than it would if the Earth had no atmosphere. Thus, in the morning, the upper edge of the disk is visible for several minutes before the geometric edge of the disk reachs the horizon. Similarly, in the evening, the upper edge of the disk disappears several minutes after the geometric disk has passed below the horizon.

For observers within a couple of degrees of the equator, the period from sunrise to sunset is always several minutes longer than the night. At higher latitudes in the Northern Hemisphere, the date of equal day and night occurs before the March equinox. Daytime continues to be longer than nighttime until after the September equinox. In the Southern Hemisphere, the dates of equal day and night occur before the September equinox and after the March equinox.

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