Earth is a special spot in the solar system for so many reasons- its sprawl; ing continents, its blue seas, its nearly limitless variety of ice-cream flavors. But one earthly thing stands out above the rest: its Earthlings. Ours is the only planet currently known to harbor life. In fact, Earth's unique combination of air, water, and land nurture life of every sort, from microscopic amoebas to submarine-size blue whales.
Earth's atmosphere not only provides the right mix of breathable air for animals and plants but it- combined with an oxygen-rich ozone layer and the planet's electromagnetic field-also acts as a force field against solar radiation and deadly space debris. The solar system's other planets are typically too hot or too cold to support liquid water, but Earth is just right. Oceans cover nearly 70 percent of the planet's surface and are a source of the water vapor responsible for our weather.
WHY IS THE EARTH ROUND?
Actually, it's not perfectly round; It's an "oblate spheroid," a sphere that's slightly wider at the Equator than at the Poles. Gravity squashed Earth and the solar system's other planets into spherical shapes back when they formed from clouds of dust and gas. Earth's rotation is what causes its slight bulge around the middle.
Earth's rotation is a side effect of the formation of our solar system, which started as a massive cloud of gas and dust roughly 4.6 billion years ago. The cloud began to rotate as it scrunched together under its own gravity. The material at the center eventually became the sun, while whirlpools of dust and gas farther out spun faster and faster until they formed into planets. With nothing to stop its spinning motion, Earth retained the rotation from its early days.
HOW FAST DOES THE EARTH SPIN?
Along the Equator - the imaginary line halfway between the North and South poles - Earth rotates at 1,037 mph (1,670 kph), a speed rivaling that of a fighter jet at full cruise.
WHY DOES THE EARTH SPIN FASTEST AT EQUATOR?
Still, confused? That's where the Earth is widest along its axis, so any point along the Equator has a greater distance to travel during each daily rotation than any point closer to the poles. Think merry-go-round. The horses on the outside have a greater distance to travel around the carousel - and thus move faster - than the horses on the inside.
HOW DO WE KNOW WHAT'S IN THE EARTH'S CENTRE
The truth is, we don't know for sure. Geologists can only guess at the planet's ingredients by studying seismic waves created by earthquakes. Bouncing through Earth's interior, these vibrations of energy travel at different speeds through different materials, such as granite, iron, and nickel. By measuring the speed of the waves, seismologists can get to the bottom of what lies beneath our feet. We're making discoveries all the time. In 2014, geologists found what might be a reservoir of water larger than all the planet's oceans combined deep in the Earth's mantle.
If you want to see the deepest hole ever dug- although it's covered by a metal plate- you'll need to travel to the Kola Peninsula in northwest Russia. Here, for more than 20years, geologists burrowed 7.6 miles (12km) through layers of rock to unlock the secrets of the Earth's crust. Called, appropriately enough, the Kola Superdeep Borehole, the project ground to a halt in 1992 when the drill hit a pocket of extreme temperatures.
WHAT WOULD HAPPEN IF THE EARTH STOPPED SPINNING?
Buildings would topple. Mountains would crumble. Seas would slosh into your bedroom. If the Earth suddenly put on the brakes, everything and everyone on it would suddenly hurl in the planets' former spin direction. (People who live near the equator - where Earth's spin is fastest - would have the roughest ride.) Gravity would keep us from flying into space, but Earth would become a different place - even for those who live far from the equator. For starters, the worldwide system of time zones would change drastically. A day would last a year. Crops would wither. The good news is that this nightmare scenario is a virtual impossibility.
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