PLANET EARTH
The Sun won’t warm you up if atmospheric pressure is low
Does Earth have a constant oxygen level? No. The oxygen level has varied a lot in the past. It was 35 per cent during the Carboniferous period. But, as the climate cooled and land plants died off, it fell to 12 per cent by the beginning of the Triassic. Back then, the air at sea level would have felt thinner than at the top of the Alps today. Burning fossil fuels has only reduced oxygen levels slightly, and deforestation also has a small effect, as other plants grow in place of trees. But global warming will have a significant impact on marine plankton, which produce about 70 per cent of atmospheric oxygen.
WHY IS IT COLDER AT THE TOP OF A MOUNTAIN, IF YOU’RE CLOSER TO THE SUN? As the Sun is around 150 million kilometres away, even being on top of Everest only brings you 9km closer – too small a difference to make you feel warmer. At these altitudes, barely 10 per cent of the atmosphere remains. As the air isn’t so compressed, the air pressure is so low that the temperature falls to a lethally cold -55°C. In an airplane, passengers and crew are kept warm using hot air taken from the compressor stages of the engines before it’s mixed with fuel.
Why is most of the world’s landmass in the northern hemisphere? The Greek philosopher Aristotle argued that there simply had to be a huge landmass south of the equator in order to balance out the vast amount to the north of the planet. The idea of ‘Terra Australis’ persisted for over 2,000 years and even appeared on maps between the 15th and 18th Centuries. It was finally debunked by Captain James Cook’s expedition to find it in the 1770s. It’s now recognised that the continents aren’t that important, being merely slightly thicker parts of the upper crust, which itself represents barely one per cent
90
of the volume of the Earth. Satellite studies of the distribution of gravity across the entire planet reveal little difference between the amount of mass in the northern and southern hemispheres. As such, the arrangement of the world’s continents has little significance – and, in any case, has changed over time. Around 200 million years ago, Earth’s surface was dominated by the Pangaea supercontinent, much of which was actually south of the equator. Pangaea broke up over time to form the modern continents that we’re familiar with today.
IN NUMBER S
2,500 The distance, in kilometres, that autonomous sub Boaty McBoatface will travel under the Arctic sea ice.