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.

Amazing NASA images of the British Isles blanketed in snow

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.