Did you really think you were going to get an article about Eclipses without that joke?
On Earth we can observe two kinds of eclipses: the solar eclipse and the lunar eclipse.
Both types of eclipses require the Sun, the Moon and Earth to be aligned, but the order of the alignment is what makes the difference.
Normally the moon appears to be emitting light when we see it at night. This is because the light of the sun hits the moon's surface and gets reflected back to us. The moon itself does not actually produce any light, but because it is so close to us, it appears as the second brightest object in the sky to us, with only the sun itself appearing brighter when viewed from earth.
The moon orbits earth, taking about a month to make a full revolution. This means that if the moon started out being between the earth and the sun, it will have moved so the earth is now between it and the sun instead in the span of two weeks. After another two weeks, the moon will have completed its orbit and will return to the original position between earth and the sun.
This orbit is responsible for creating the different phases of the moon. At new moon, the moon is directly between earth and the sun, and so the visible side of the moon is not visible on earth, as no light from the sun hits the side of the moon turned towards earth.
Opposite, when the moon is on the other side of earth, the entire lit side of the moon is visible from earth and we get a full moon. The other phases are simply steps in between these two ends of the spectrum.
As I mentioned above, eclipses happen when the moon, sun and earth align perfectly. In lunar eclipses the alignment must be such that the moon enters into earth's shadow, meaning that earth must be between the sun and the moon. This alignment would in most cases only result in a full moon, and in fact lunar eclipses can only occur during a full moon. The reason not every full moon becomes a lunar eclipse, is because the moon orbits on a different plane than earth, which means that unless the moon is crossing earth's orbital plane, the moon will not be in earth's shadow even though earth is between it and the sun. If the moon and earth did orbit on the same plane, every full moon would result in a lunar eclipse.
Solar eclipses are not all that different from lunar eclipses, except that instead of the moon passing through earth's shadow, the roles are reversed and it is the moon casting a shadow on earth. For this to occur the moon must of course be between the sun and earth, which means that it must be in the new moon phase. It must also be crossing earth's orbital plane or the eclipse would not occur. This is exactly the same as with the lunar eclipse and like the lunar eclipse, it would happen once a month if earth and the moon orbited on the same plane.
This is an illustration of what would happen if the moon, without changing size, was much further from us. The rays from the sun would reach across the point where the moon's shadow would fall and there would be no chance for a full eclipse. This actually does happens at earth because the moon's orbit around earth is not circular, but elliptical, meaning that there will be times where the moon is further from earth and times where it will be closer. If the moon is so far away from earth that it appears smaller in the sky than the sun, it will not be able to cover the sun entirely, and instead create what is known as an annular eclipse where the sun creates a ring of light around the moon.
Mars is one of those planets that can have solar eclipses, but whose moons are too small to create total solar eclipses. Jupiter, Saturn, Uranus and Neptune also experience solar eclipses, and because their moons are large enough, they experience full solar eclipses.
As the image illustrates, solar eclipses are not visible on the whole surface of the earth at the same time, but only on the part that falls in the shadow of the moon. Because the moon is much smaller than both the sun and earth, it cannot cast a shadow on all of earth at the same time. During a lunar eclipse everyone on the side of earth facing towards the moon will be able to observe the eclipse, since we observe from the object casting the shadow.
All planets that have moons are able to experience lunar eclipses, but solar eclipses are a little more special. On earth we are able to see total solar eclipses because of two factors: our moon is relatively large and fairly close to us. If the moon was smaller or much further away, we would never be able to experience full solar eclipses.
The last total solar eclipse occurred on the 21st of August 2017. It was visible from large parts of the United States. The next chance to see a total solar eclipse will be on the 2nd of July 2019. This eclipse will be travelling mostly over water and only be visible from land towards the end of the event where it will travel over South America.
https://www.livescience.com/60037-do-ot ... ipses.html
https://en.wikipedia.org/wiki/Template: ... _2015-2018
https://en.wikipedia.org/wiki/Template: ... _2018-202
Scientifics are slightly geeky additions that have been with us since the eagle has known how to fly. Okay, not that long, but it's a nifty category that separates it from the usual ramble of articles.