Why wear black clothes in heat, and is the UK tilted?

We explore some of the curious questions that science can answer

Nobody panic: the southeast of the country is slowly sinking into the sea (Getty)

If dark things absorb heat better than white, why do people in hot countries sometimes wear black clothes?

Indeed, people who wear dark clothes in hot countries sometimes get hotter than if they wore white. But as a result, the clothes are much hotter than the body, causing a significant difference in temperature between the two.

Temperature differences cause air to move, creating a breeze. This cools the body. However, it is unlikely that this is the main reason people in hot countries wear dark clothes. They are much more commonly worn for cultural reasons.

Does the speed of sound increase the farther underwater you go?

Sound is the transfer of vibrations from one particle to another. If sound is travelling through a material where the particles are close together, then not only will the sound travel farther, it will also travel faster. So in water, which gets denser the deeper you go, as more and more liquid presses down from above, sound will travel faster and farther.

How does heat make things rise?

If you make any part of a liquid or gas hotter than the air or liquid around it, it will rise. This is because of density, which is worked out by dividing the mass of something by its volume. If a gas or liquid is heated, it becomes less dense. Atoms get more energy as you heat them, so they move about more and start to take up more volume. Although the atoms have the same mass, the volume goes up, and the density goes down. Things that are less dense than their surroundings rise. So balsa wood is less dense than water and floats, but it is denser than air, so it doesn’t fly away.

Do stalactites have a transparent coating of crystals?

Transparent calcite crystals can coat the outside of a stalactite and cause it to sparkle – giving it the impression of being covered in crystals.

Do tornadoes turn in opposite directions in the northern and southern hemispheres?

Tornadoes usually rotate anticlockwise in the northern hemisphere and clockwise in the southern. They have been observed spinning “the wrong way” in either hemisphere, but this is less common. The effect of the Earth’s rotation – known as the Coriolis effect – acts on objects moving with respect to the Earth’s surface (aeroplanes, birds and so on). It is only significant over distances spanning hundreds or thousands of miles and time spans of 12 hours or longer. Hence tornadoes themselves are not influenced by the Coriolis force. But the Coriolis force does affect violent storm systems called supercells, causing them to rotate in different directions in the hemispheres.

Many tornadoes arise from supercells, so the Coriolis effect indirectly causes the tornadoes to rotate differently in the two hemispheres.

It is not certain what causes “renegade” tornadoes to rotate in the other direction, but it may be something to do with the topography of the area they are in.

Is it true that the UK is tilted towards the southeast?

Yes. The southeast of the country is slowly sinking into the sea while the northwest of Scotland is slowly rising because of a process called isostatic compensation, whereby something that has been covered by a heavy weight bounces back when that weight is removed. Scotland used to be covered by ice during the last Ice Age.