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(Premium) Gist of Science Reporter Magazine: January 2014

Premium - Gist of Science Reporter: January 2014

EARTH & MOON, A REVIEW (Full Material Available Only For Premium Members)
LIVING ON THE MOON (Full Material Available Only For Premium Members)
MEANING OF GAME THEORY (Full Material Available Only For Premium Members)
BRIEF HISTORY OF GAME THEORY (Full Material Available Only For Premium Members)
SUCCESS OF BUENO DE MESQUITA’S GAMES (Full Material Available Only For Premium Members)

EARTH & MOON, A REVIEW

We all become familiar with the Moon right from our childhood days. We its changing phases. We see the dark markings on its face, which resemble different things to different eyes. Some people see in the dark markings a figure of a woman with the spinning wheel, while in many western countries people see the face of a man or a hare.

One of the few astronomical bodies in the sky that can be observed without any optical aid, the
Moon was enshrouded in mystery for much of history. Earlier, it was revered as a reflection of gods and goddesses. It was even viewed as another planet with seas and land. Eventually, Galileo and his telescope got a picture of what we know the Moon to be today—a natural satellite with mountains, craters and expanses of flat plains.

The coming of the Space Age has turned around our ideas about our nearest celestial neighbour. Today, the Moon no longer holds any mystery for us. Extensive exploration by space probes and astronauts has unravelled new facts not only about the Moon, but also about the past history of our Earth and the Solar System.

A Unique Satellite

Of the eight planets of the solar system two planets, Mercury and Venus, do not have any moon of their own. Of the rest, our Earth has the least number of moons - only one, compared to a total of 168 moons discovered for the remaining five planets.

But Earth’s only Moon has no parallel in the solar system. With a diameter of 3,476 kilometres, our Moon is smaller than four other moons of the solar system. Three of the Galilean moons of Jupiter are bigger than Earth’s Moon, as is Saturn’s moon Titan. But if we compare our Moon’s diameter with the Earth’s diameter of 12,756 kilometres, the Moon is just about one-third the size of the Earth. The solar system’s largest moon Ganymede, with a diameter of 5,276 kilometres, is only about 1/26th the size of its mother planet Jupiter.

The Earth is about 81 times as massive as its only moon, whereas the masses of the other planets are several thousand to a million times the masses of their moons. At least in this sense, the Earth and Moon seem more like a double planet system rather than a planet and its satellite. In fact, planetary scientists consider the Earth and the Moon going round a common point called ‘barycentre’ that lies 1,710 kilometres below the surface of the Earth.

Another peculiarity of the Moon is its distance from Earth, which is far greater than is the case for some moons of the other planets relative to their radii. The mean distance of the Moon from Earth is 3,85,000 kilometres, which is sixty times the radius of Earth. This is more than double the distance between Jupiter and its outermost moon Callisto; almost three times the distance between Uranus and its outermost moon Oberon; and four times the distance from Neptune to its large moon Triton.

However, despite its large distance from Earth, the relatively large mass of the Moon exerts enough gravitational pull on Earth to cause visible effects. The main visible effects are the ocean tides, which make the ocean waters rise and fall twice a day under the influence of the Moon’s gravity. The gravity of the Sun also influences ocean tides, but not as strongly as the Moon, and peak tides depend on the position of the Sun, winds, and rotation of the Earth. Sometimes the gravitational pull of the Sun and Moon work together to produce very high tides (spring tides) and sometimes they work against each other to produce low tides (neap tides).

The large size of our Moon also plays a decisive role in sustaining life on Earth. On Earth we have the seasons because of the tilt of Earth’s axis, which is at present 23.5 degrees. Were it not for the Moon, the influence of the giant planets Jupiter and Saturn would have made the tilt of Earth’s axis vary wildly - between values as extreme as 0 to 80 degrees. Such variation would probably have caused extreme climatic changes that would render our planet uninhabitable. Thus, having a large Moon may be a boon for us - without it life may not have evolved on Earth.