But anytime Jupiter is visible in your sky featues a good time for viewing Jupiter’s four major moons. So if you get a chance, grab some binoculars or a small telescope and go see Jupiter’s Galilean moons with your own eyes! Click here for recommended sky almanacs; they can tell you Jupiter’s rising time in your sky.

Europa

Ganymede

This ‘family portrait’ shows a composite of images of Jupiter, including it’s Great Red Spot, and its four largest moons. From top to bottom, the moons are Io, Europa, Ganymede and Callisto.

Titan

Jupiter’s moons stay in orbit because gravity pulls them towards Jupiter. it mainly happens like a game of tug of war . Two forces are included, one pulls the moons towards Jupiter , the other one pulls them towards space. So Jupiter’s moons stay in orbit around Jupiter because Gravity pulls them !

Albedo

Newton was the first to see that Earth and the moon are bound by gravity. And he didn’t stop there. Jupiter has moons circling around it — so Jupiter must have gravity too. And the sun — its gravity holds the planets in their orbits.

Gravitational attraction provides the centripetal force needed to keep planets in orbit around the Sun and all types of satellite in orbit around the Earth. The Earth’s gravity keeps the Moon orbiting us. It keeps changing the direction of the Moon’s velocity.

The Moon does not fall towards Earth right now because Earth rotates itself. The energy from the Earth’s own rotation around its axis is gradually tranferred into energy of the Moon’s orbital motion. That’s why the Earth’s rotating speed decreases but the distance to the Moon increases.

The moon does not fall to Earth because it is in an orbit . One of the most difficult things to learn about physics is the concept of force. Just because there is a force on something does not mean it will be moving in the direction of the force.

Most space scientists have come to believe that the moon was created when another planet (now called Theia) collided with a very early Earth—pieces of Earth, Theia or both that were flung into space during the collision eventually coalesced into the moon.

If the Moon did escape from Earth, the main effect would be the lack of tides on Earth. Tides are caused by the differential gravitational force on the equatorial regions: i.e. the region closer to the Moon experiences more gravitational force than the region on Earth away from the Moon.

A new study led by Qian Yuan, a geodynamics researcher at Arizona State University (ASU), Tempe, suggests that the remnants of Theia is still inside Earth, probably located in two continent-size layers of rock beneath West Africa and the Pacific Ocean. Seismologists have been studying these two rock layers for decades.

Originally, the hypothesis supposed that Theia had struck Earth with a glancing blow and ejected many pieces of both the proto-Earth and Theia, those pieces either forming one body that became the Moon or forming two moons that eventually merged to form the Moon.

Sediments from China suggest that 1.4 billion years ago the Earth-moon distance was 341,000km (its current distance is 384,000km).

Water is abundant in space and is made up of hydrogen created in the Big Bang and oxygen released from dying stars. Earth was moulded from rocks that came from the inner solar system where the fierce heat of the Sun would have boiled away any water. So, according to the textbooks, water must have come later.

From the Water Wired blog: “Much has has been made of several recent statements that we are indeed drinking ‘dinosaur pee’ because the same water that is around today was around then as well.

Water, as a vapor in our atmosphere, could potentially escape into space from Earth. While our planet as a whole may never run out of water, it’s important to remember that clean freshwater is not always available where and when humans need it. In fact, half of the world’s freshwater can be found in only six countries.

Evaporation happens when a liquid substance becomes a gas. When water is heated, it evaporates. The molecules move and vibrate so quickly that they escape into the atmosphere as molecules of water vapor. The water level will decrease as it is exposed to the heat of the sun.

Evaporation happens when a liquid turns into a gas. It can be easily visualized when rain puddles “disappear” on a hot day or when wet clothes dry in the sun. In these examples, the liquid water is not actually vanishing—it is evaporating into a gas, called water vapor. Evaporation happens on a global scale.

Water at the Earth’s surface evaporates into water vapor which rises up into the sky to become part of a cloud which will float off with the winds, eventually releasing water back to Earth as precipitation.

The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Ice and snow can sublimate directly into water vapor. Air currents move clouds around the globe, cloud particles collide, grow, and fall out of the sky as precipitation.