Published on March 23rd, 2010 | by Yellow Magpie

Planet Mercury: The Strange World That Supported Relativity

A strange planet in many ways. Eerily like our Moon in both appearance and scale, planet Mercury is a dull, grey world that bares a remarkable past.

Planet Mercury is the smallest of all the inner terrestrial planets. Yet, despite its size, it has earned its place in Greek and Roman mythology. Deified as the Messenger God, Mercury, the planet closest to the Sun has an inhospitable environment. Too cruel for life, it’s Sun-scorched surface bares the full brunt of the fierce heat and Solar Winds of our life-giving star.

Roman Prescience And Coincidence

The Romans were sagacious in choosing the planet to be the Messenger God. Mercury, is an apt name as the planet races across the Sun at a far quicker rate than any other planet in the Solar System. One year on Mercury lasts just 88 Earth-days. However, because of Planet Mercury’s close proximity to the Sun and consequently the extreme gravitational forces exerted upon it, its day lasts over 58 Earth-days. This means that its day is exactly two-thirds the length of its year.

The Romans were also accidentally responsible for associating the planet with the element mercury. Although its temperature is no where near as hot as Venus, its mean surface temperature is a blistering 130 degrees Celsius 260 degrees Fahrenheit.

With no atmosphere, planet Mercury is subjected to heavy bombardment from meteors and an odd mixture of freezing and boiling temperatures depending on what part is exposed to the Sun. Mercury’s axis tilt is a negligible two degrees. As a result, the poles receive hardly any sunlight. This makes it very hazardous to life as we know it.

Coincidentally, the element mercury is one of the most toxic substances on the planet. As the University of Calgary has noted, mercury causes grave damage when it comes in contact with neuron tissue.

Planet Mercury And A Never Setting Sun

One interesting phenomena is that because of the speed at which Mercury orbits the Sun and because of its long days not only can the Sun be seen rising on the planet but its direction is reversed. In other words, as the Sun rises its movement is sometimes reversed so that it appears to go backwards.

Core Of A Much Larger Planet

At 4,875 kilometres across, Mercury is just over one-third the size of Earth. Yet, it is almost as dense as our home planet. The structure of Mercury consists of a huge core of solid iron ore. The core is surrounded by a mantle and crust composed of silica. So massive is Mercury’s core that astronomers believe that Mercury was a good deal larger in size than it is today. It is maintained that a large impact with a large rogue planet resulted in much of the surface of Mercury being stripped.

Site Of Huge Impacts

Planet Mercury also has a huge impact crater, after the Moon’s South Pole-Aitken Basin, the Caloris Basin is the second largest crater in the Solar System. Measuring a vast 1,340 kilometres (840 miles) across, it is one of the largest features on the planet.

A Strange Distortion And General Relativity

For years scientists have used Newtonian Physics to calculate and predict planet’s orbits and alignment. However, the planet brought up an interesting conundrum. Planet Mercury was not where it was predicted to be. This lead people to speculate that there must be another planet causing Mercury’s orbit to be different than its predicted model.

The truth behind this phenomenon is that Newtonian Physics is limited. Areas which are under the effects of very strong gravity cause problems for Newtonian Physics. Nevertheless, these discrepancies could be explained by Einstein’s General Theory of Relativity. Therefore, Mercury is right where it is supposed to be and there is no unidentified planet causing its orbit to be perturbed.

Highly Recommended

You may wish to check out Yellow Magpie’s The Solar System And Beyond: A Guide To The Cosmos.

Cosmos is a highly recommended book. It contains large, full-page pictures of the known surface of planet Mercury and insightful writing on the subject by the highly competent author, Giles Sparrow.

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For people living in Ireland or the United Kingdom, you can access: Cosmos from here.

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For Germany: Cosmos.

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For France: Cosmos.