Skywatch - 1. Moon

The Moon is a piece of the Earth that splintered off when struck by a meteor when still largely molten. It is still moving away from the Earth. A couple of odd facts are that the Moon is 400 times closer to Earth than the Sun and coincidentally 400 times smaller, enabling us to see a total eclipse and the 'diamond ring' effect. The other fact is that we only ever see one face of the Moon as its rotational spin is locked together with with its revolution around the Earth.

To see what sort of battering the Earth has taken over the ages, you need look no further than the Moon. In fact with a larger surface area it is reasonable to assume the Eart has been hit far more often. The hits on the Earth have with the passage of time all but disappeared, with the Moon however there is no atmosphere and the impact craters are there to be seen.

A popular misconception:

In September 1608 Hans Lippershey a Dutch spectacle maker came up with a device which could make distant objects appear close. He and several others were quick to apply for patents and by the time a certain Galileo Galilei heard of the telescope in the summer of 1609, small 4x magnification examples were being sold in France.

So Galileo didn't invent the telescope but he did increase its power to 9x magnification. With this new tool he noticed the uneveness of the Moon's surface and began to chart the craters and plains.

The Moon of course is also responsible for the rise and fall of tides with its gravitational pull. A 'harvest moon' comes soon after the autumnal equinox. It is simply the first full moon after that equinox. About once every four years it occurs in October (in the northern hemisphere), depending on the cycles of the moon. Currently, the latest the harvest moon can occur is on October 7.

When the night of the harvest moon coincides with the night of the equinox, it is called a "Super Harvest Moon." In 2010 in the contiguous United States, the harvest moon happened in the early morning hours of Sept 23, only 5 1/2 hours after the autumnal equinox, creating the first Super Harvest Moon since 1991.

Often, the harvest moon seems to be bigger or brighter or more colourful than other full moons. The warm color of the moon shortly after it rises is caused by light from the moon passing through a greater amount of atmospheric particles than when the moon is overhead. The atmosphere scatters the bluish component of moonlight (which is really reflected white light from the sun), but allows the reddish component of the light to travel a straighter path to one's eyes. Hence all celestial bodies look reddish when they are low in the sky.

The apparent larger size is because the brain perceives a low-hanging moon to be larger than one that's high in the sky. This is known as a moon illusion and it can be seen with any full moon. It can also be seen with constellations; in other words, a constellation viewed low in the sky will appear bigger than when it is high in the sky.