Where is the coldest place on Earth, and how heavy is our atmosphere?

We explore the curious questions that science can answer

Penguins in the South Pole, home to average temperatures of -50C (Getty/iStockphoto)

Where is the coldest place on Earth?

The South Pole is the coldest place on Earth, with average temperatures of -50C (-58F). The coldest place in Antarctica is the Russian station of Vostok, where temperatures as low as -89C have been recorded. 

Where is the highest waterfall in the world?

The Angel Falls in Venezuela are the highest falls in the world, at 979m (3,212ft).

What is the weight of Uluru?

Uluru (also known as Ayers Rock), in the Australian outback, weighs about 10 million to 20 million metric tonnes – an estimate from its shape and density. 

Of what material is Uluru made?

Ayers Rock is a monolith of a terracotta-coloured arkose sandstone. Arkose is a term used to describe an arenaceous rock – that is one which is sandy or sand like in appearance. There are three main groups of arenaceous rock: quartz sandstones, greywackes and arkoses. The definition of arkose is sandstone containing quartz and 25 per cent or more of feldspar.

I saw a rainbow very high in the sky near cirrus clouds, with no curve. It was on a damp evening. What was this?

What you saw was no rainbow – although it was very similar. Rainbows are caused by sunlight being reflected and split inside raindrops. This other effect is called parhelia, or sundogs.

Instead of water, ice crystals (hexagonal in shape) refract light and refocus some of it towards you, giving a ring of light around the sun.

It is rare to see the whole ring, but arc-sections are common. At the four compass points of this ring you often see brighter patches of “rainbow-like” light, several degrees in extent.

Why do the Earth's magnetic fields flip every million years or so?

The current understanding is that the Earth’s magnetic fields are produced by a complex system of electric currents circulating in the molten part (not all of it is molten) of the Earth’s iron core.

The currents exist because molten iron is a good electrical conductor and is undergoing convective stirring as it passes its heat upwards into the overlying solid mantle.

The currents produce a magnetic field in a similar way to an electromagnet; but the whole thing is more complicated because the magnetic field interacts with the electric currents and keeps changing the convection pattern.

Inside the core the magnetic field is complicated but, fortunately, the net effect seen from the outside is less so, and the Earth’s field we measure at the surface is rather like that from a bar magnet which is slowly wobbling. This is why the direction of magnetic north changes slowly with time.

It seems that the convection process sometimes gets into a pattern where the magnetic field seen from the outside becomes very small and then grows again but with the opposite polarity; that is, it reverses.

This has been shown to occur in some mathematical models of the Earth’s core and also in physical models (involving complicated systems of bar magnets and coils of wire in the laboratory). The only problem is that we are not sure whether these models are exactly like what happens inside the Earth’s core, so we cannot predict just what to look for when a reversal is imminent. The bottom line is that we understand the process in general, but not yet in extreme detail.

How heavy is the Earth’s atmosphere?

Assuming the Earth to be a perfectly flat sphere with an air pressure of 9.65 x 10⁴ newtons per square metre (14 pounds per square inch) all over its surface, the atmosphere weighs 4.9 x 10¹⁸ newtons (a mass of about 5 million billion tonnes).