Magnetic Fields

An electromagnetic field is produced by any charged particle, and extends indefinitely throughout space. This force is one of the four fundamental forces of nature, with the other three being gravity, the strong force and the weak force. The Earth acts like a massive charged particle, with a field that encompasses it entirely. The core of the Earth creates this powerful field. The Earths negatively charged pole is located around the geographic north pole, and the positively charged pole at the south pole.
One of the most important thing the field does for Earth is that it shields us from solar wind. Solar wind is a stream of charged particles that come flying off from the sun. Without this protection the surface would be not a very habitable place.

Solar wind

The field is responsible for the northern lights. The northern lights are commonly seen in the latitudes between 60 and 72 degrees north and south, just within the Arctic and Antarctic polar circles. The light is created by collisions of charged particles created by the magnetic field. The light is usually created in the ionosphere, about 80km (50 miles) up.

Climate Change

While not a space topic, i think everyone could do with a bit more informing on this topic.

Click for full-sized image.

I'm not going to try and sway you one way or another. You can draw your own conclusions from these pictures.

Titan

Titan is a cold moon in orbit around Saturn. Titan is the largest moon in orbit around Saturn, slightly larger in size to the planet mercury. Titan is the only other celestial body in the solar system that has liquid oceans. But these oceans are not water, they're methane so cold they have condensed into a liquid state, evaporating and falling again as rain. The satellite experiences much the same forces as Earth with wind, and weather patterns.

Composite view of Titan built with Cassini images

"It has also been suggested that a form of life may exist on the surface, using liquid methane as a medium instead of water; and anomalies in atmospheric composition have been reported which are consistent with the presence of such a life-form, but which could also be due to an exotic non-living chemistry"  -Mckay, Chris (2010). "Have We Discovered Evidence For Life On Titan"

The gravity on Titan is only 14% of that on Earth. Titan is the only known moon with a fully developed atmosphere that consists of more than just trace gases.
If you were on Titan, you could fly.

Theia

A colossal interplanetary collision doesn't sound like a good thing.

But when Theia collided with Earth 4.5 billions years ago, it resulted in a satellite that is anomalously big in comparison to its parent planet. There is nothing else like it in the solar system, where satellites are relatively small bodies that either accredited slowly from orbiting debris or were captured in passing. Elsewhere it seems a similar story. Giant collisions in other solar systems would produce abundant dust visible to the infrared Spitzer Space Telescope, but although a few such dusty systems have been found, collisions big enough to produce something like the moon seem to happen in only 5 to 10 per cent of solar systems - with the number of instances where this has actually happened considerably smaller even than that.

Why does this matter? Because the moon's size provides a steadying gravitational hand that helps to stabilise the tilt, or "obliquity", of Earth's axis. That prevents wild changes in the pattern of solar heating on the planet's surface that could lead to extreme climate swings, including frequent periods where the whole planet freezes over. That's a big deal for us. Conditions might be bad for complex land-based life if there were no moon and obliquity varied significantly.

more space info to come, and pictures.