The official definition of the speed of light in a vacuum is c = 299 792 458 meters per second. To help you make sense of this, here are some other ways of describing this: Light travels at just over a billion kilometers (or 600 million miles) per hour. If you could make a beam of light curve, and sent it on a trip around the Earth, it would make the journey 7 times in under a second. It takes … Continue reading →
That’s a dangerous question! Last time somebody asked it seriously, they demoted Pluto! A planet is any object orbiting the Sun which is heavy enough to both squeeze itself into a spherical shape and clear the space around its own orbit (in other words, its gravity must be powerful enough that anything nearby gets drawn in and either smashes into the planet or gets catapulted away into space). By this definition, we have eight planets in our Solar System. It’s … Continue reading →
Mercury is the smallest planet known, with a diameter of just under 4900km. Until it was disqualified as a planet in 2006, though, Pluto held the title at somewhere over 2300km – less than half the size! Thanks to the formal definition of a planet, Mercury is not likely to lose its place at the bottom of the size ranks for a while: we can see quite clearly that there is nothing smaller in our Solar System which meets all … Continue reading →
“Shooting star” is the common name for a meteor, because it looks just like a regular star shooting across the sky. The Solar System is full of dust and debris left over from when it first formed, and thousands of tonnes of this stuff falls on Earth every year. When larger particles (about the size of a grain of sand) hit the atmosphere, they’re coming in at speeds up to 70 kilometers per second, and have a tremendous amount of kinetic … Continue reading →
Twelve. There were six successful moon missions (Apollo 11, 12, 14, 15, 16 and 17), and each of these had a crew of three. One crew member stayed in orbit in the command module, while the other two landed the lunar module, and walked on the Moon’s surface. Everybody remembers the names of the two men who landed in the first mission (Neil Armstrong and Buzz Aldrin), but hardly anybody remembers that the third man was Michael Collins. … Continue reading →
