And: What about the planets lining up in the sky?

Quite a number of readers have written to us about the comet Elenin. A number of websites are preaching doom and gloom about this, as they have done with planetary alignment. Dr Jonathan Sarfati demolishes these claims with real physics and astronomy.

What is a comet?

We have addressed the issue of comets in detail in Comets—portents of doom or indicators of youth? Readers may like to study this, especially for the strong evidence they provide against millions of years. This also points out that comets have widely been regarded as indications of looming disaster. Now the sensationalism has a pseudo-scientific gloss involving the actual comet.

But in reality, the comet itself is a ‘dirty snowball’ only a few km across. And when it is close to the sun, then some of this material evaporates and forms an ion tail and a dust tail. These can dominate the sky. However, the actual material of the tail is even thinner than our best laboratory vacuums. So there is no way the tail can hurt us in the slightest—there is almost nothing there! Indeed, Earth passed through the tail of Halley’s Comet in 1910 and barely noticed.

A direct comet impact would certainly be damaging to life. Because of their enormous speed relative to the earth (11 to 74 km/s), their kinetic energy is huge as shown by the standard formula E = ½mv². Because of the likely damage of an impact, NASA is tracking Near-Earth Objects (NEOs).

A small comet about 50 m across has been proposed as a cause of the 1908 explosion in Tunguska, Siberia, a ~10 megaton blast which flattened over 2,100 km² (800 sq. miles) of forest. But this caused no loss of human life, since there were no human habitations close by; there was no global effect. In fact, as explained in this 2008 feedback, impacts from far bigger comets would barely make a detectable difference to Earth’s axis, rotational speed or orbit.

What about Elenin itself?

Comet C/2010 X1 was named after Leonid Elenin (Леонид Еленин), a Russian amateur astronomer who discovered it on 10 December 2010. He was remotely using the International Scientific Optical Network’s robotic observatory near Mayhill, New Mexico, USA. It is not a very spectacular object: even at its brightest, it will be 25 times too faint for the naked eye to see. It is probably only about 3–4 km in diameter. It’s most likely a lot smaller than the famous Halley’s comet, which has a mass of 2.2×1014 kg. This sounds a lot, but the earth’s mass (M) is 5.9722 × 1024 kg—27 billion times more….

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