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The extinction of dinosaurs is one of the many periods of mass extinctions on earth. www.shutterstrock.com/Jaroslav Moravcik

5 periods of mass extinction on Earth. Are we entering the sixth?

Scientists believe since 2010 we have entered the sixth period of mass extinction. CO2 emissions will change the lives of plants and animals in the next three to four decades.
The mass of the Earth is big enough that the gravitational force it creates can pull the hard shape of ice, rock and metal into a sphere. NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA's Goddard Space Flight Center

Curious Kids: Why is the Earth round?

Imagine the Earth pulling everything it is made up of, all of its mass, towards its centre. This happens evenly all over the Earth, causing it to take on a round shape.
Lasers being shone from the European Southern Observatory’s Very Large Telescope in Chile. These lasers help remove the twinkles in the night sky and help astronomers see stars clearer on Earth than ever before. F. Kamphues/ESO

Curious Kids: Why do stars twinkle?

How exactly do the stars twinkle in the night sky? As it turns out, the answer is full of hot air... and cold air.
A solar eclipse observed over Grand Canyon National Park in May 2012. Grand Canyon National Park

How eclipses were regarded as omens in the ancient world

More than 2,000 years ago, the Babylonians understood the cycle of eclipses. They also regarded them as signs that could foretell the death of a king.
Earth, shot from space, as it absorbs and reflects rays of light coming from the Sun - the same white-looking rays that give our sky its colour. NASA

Curious Kids: Why is the sky blue and where does it start?

Some people think the sky is blue because of sunlight reflected off the ocean and back into the sky. But that's not the real reason.

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