A Supermoon is a Full Moon which appears larger than usual in our skies. The Moon’s orbit is not perfectly circular, but is elliptical. This means that there is a point in its orbit that is closer to Earth than any other (called ‘Perigee’) and a point that is further (‘Apogee’). The orbit takes 27.3 days, so the Moon is at Perigee exactly once every 27.3 days. However, the cycle of phases takes a little longer (Because they are … Continue reading →
Escape velocity from the surface of the Earth is about 11.2 kilometers per second (or just over forty thousand km/h, or twenty five thousand mph), meaning that if you want an object to leave Earth and never fall back, you have to throw it at least that fast. How does that work? Well as you’ll remember from high school physics, Newton’s law of universal gravitation tells us that an object’s weight (The downward force applied by gravity) depends inversely on … Continue reading →
An equinox is a point in the Earth’s orbit when day and night are both exactly the same length. There are two equinoxes (or equinoctes if you want to be excessively correct) each year, but they also mark the change of the seasons between warm and cold. The Earth’s axis is tilted, so that for half of each year, one hemisphere is tilted towards the Sun, so that it gets more heat and light from the Sun that the other. … Continue reading →
Jupiter has a mass of about 1.9 x 1027kg – 1900 trillion Trillion kilogrammes. That’s more than double all the other planets, asteroids, comets and dust of the entire Solar System put together. Jupiter is BIG, yet still manages to not weigh anything at all. How? Because it is in orbit around the Sun, just like an astronaut orbits the Earth, and so experiences zero gravity. That’s not to say there is no gravity around Jupiter – it has plenty gravity … Continue reading →
Mars does not have a weight, but does have a mass of about 6.4 x 1023 kilograms, which is a little more than a tenth that of Earth. When astronauts or spacecraft orbit the Earth, we describe them as being weightless, because they are in freefall. They are not resisting gravity (the way your body does when you stand on the ground) so “Weight” becomes a totally meaningless concept when you’re in space. Written by Allen Versfeld Comments? Questions? … Continue reading →
