We’ve examined our planet from core to surface, and it seems that we know everything about it and now we are ready to explore space, but Earth isn’t at all done surprising us just yet.
Seismologists believe that the inner core of our planet is solid, while the outer one is liquid and molten. Next comes the mantle, with the crust floating on top. However, we still have no idea what it consists of, because we’ve never reached it: its depth is from 30 km to 2,900 km, and the deepest well mankind has dug so far is the Kola borehole in Russia, which is just 12.3 km deep.
Earth’s magnetic poles can move and even change direction altogether, and scientists have found that it’s happened many times. The latest switch happened 10 million years ago and will probably occur again, but no one knows why.
Astronomers say Earth had two satellites about 4.6 million years ago. The second one was about 1,200 km across and went around the same orbit the Moon does, until they collided. Such a cataclysm may explain why the two sides of the Moon are so different.
Few people are aware that there earthquakes also occur on the Moon. Unlike terrestrial ones, though, they’re not quite as powerful, and occur very rarely. There’s a theory that they happen because of the tidal forces of the Sun and Earth, as well as falling meteorites.
600 km/h, and its movement around the Sun is even faster at 108,000 km/h. We, though, can only feel the movement when its speed changes. Because of the constant speed and the force of gravity, we don’t feel it at all.
620M years ago, a day on Earth lasted 21.9 hours. Earth is gradually slowing down, but it happens at a rate of about 70 msec per 100 years, so it would take 100M years for a day to last 24 hours.
Our planet isn’t a perfect sphere, so there are high- and low-gravity areas on it. One such anomaly is Hudson Bay in Canada. Scientists found out that weak gravity there is due to the low density caused by rapidly melting glaciers.