Asteroids and comets are both remnants of the early formation of the solar system 4.5 billion years ago. As of August 2011, there were less than 4,500 known comets in the solar system, compared to over 550,000 known asteroids (although there are thought to be many millions more).

Asteroids are composed of rocky material and metals, while comets are made of ice. As a result, asteroids formed nearer the Sun than comets, because ice could not remain solid at a close distance. Comets that formed further out and later approached the Sun lose material with each orbit because the ice melts, forming a tail behind the body. Asteroids, on the other hand, do not lose material, and thus do not have a tail. Comets are often found in large elongated orbits extending outwards up to 50,000 times the distance from the Earth to the Sun. By comparison, Neptune – the furthest planet of the solar system – is just 30 times further from the Sun than the Earth.

Concurrently, asteroids are usually found following a circular orbit around the Sun and they tend to group together in belts, such as the asteroid belt found between Jupiter and Mars, which was formed when the gravitational pull of Jupiter prevented the asteroids from forming into another planet.

Weather is temperature, precipitation (rain, hail, sleet and snow) and wind, which change hour by hour and day by day. Climate is the general long-term character of the weather and the nature of its variations that we experience over time. The Earth’s climate has changed on many timescales in response to natural factors. Over thousands of years we see the Earth move in and out of ice ages. At the other extreme, El Nino (variations in surface temperature of ocean water across the tropical eastern Pacific Ocean) come and go every few years, temporarily raising the Earth’s temperature. Over the course of the last century there has been an unusual increase in the average global temperature, accompanied by changes in extremes of weather. The term ‘climate change’ is often used to refer to changes to our climate arising from human activities.

Answered by the Met Office team, OPAL Climate Centre.

Asked by: Jenna Kelly

Ice is transparent but not totally clear if it contains air bubbles or imperfections. Snowflakes are made of tiny ice crystals that join together in the air. They are not made of perfect blocks of ice, but have much more interesting shapes. Light ends up scattering in many directions as it meets the borders of those crystals and the air locked inside, making it look white. Even when they land there is a lot of air trapped, and that’s why fresh snow feels very soft when you walk over it.

José Monteiro

To answer this question there are two things which need to be considered – colour theory and refraction.
Refraction is the change in direction of light as it goes from one material to another. It is due to a slight change in speed of the light and it explains why straws look bent in water. When light enters snow, it refracts. This is because snow is made from lots of ice crystals tightly packed together, the important fact here being that these crystals are translucent (light can pass through but not in a direct path – it changes direction).
Additive colour mixing tells us that if we combine all of the frequencies of colours we get white light. When light falls on snow it is composed of a mixture of different frequencies which all refract slightly differently as they enter the ice crystals. Eventually due to refraction, the light leaves the surface of the snow in all directions and hits our eyes. This light is composed of a mixture of frequencies which our eyes detect as white light.

Capturing an iceberg collapsing or calving is a rare sight, and this couple filming off Labrador, Canada, picked up their camcorder just in time to catch the dramatic event. The pair and their dog are clearly excited about what they’ve just witnessed, but are soon chased away by a rush of smashed up ice that starts floating towards them. For an in-depth look at how icebergs are formed check out issue five of How It Works, which goes on sale on 25 February. By the way, when you watch this video just try not to imagine Kermit the Frog is behind the camera. You’ll see what we mean.

Image courtesy of NASA

The Moderate-Resolution Imaging Spectroradiometer (or MODIS) on board NASA’s Terra satellite captured this incredibly chilling image of Great Britain on 7 January as most areas experienced freezing temperatures of -10C on the coldest night of the winter so far. Isolated areas were even subjected to lows of -22C in the Scottish Highlands.

Snowfall followed by freezing temperatures left areas dangerously icy, resulting in widespread chaos on the roads. Schools across the nation were closed and many businesses sent staff home. The emergency services, including roadside assistance, were inundated with incidents.

One possible reason for the severely cold conditions across the Northern Hemisphere this last month is an extreme negative phase of Arctic Oscillation (AO). AO refers to a state of seesawing atmospheric pressure over the Arctic. The negative phase of AO causes high pressure over the polar region and low pressure at mid-latitudes.

MODIS images the entire Earth every one to two days. The grey areas against the white land surface on the map are actually the cities of Manchester, Birmingham and London.