Babies have about 300 bones at birth, with cartilage between many of them. This extra flexibility helps them pass through the birth canal and also allows for rapid growth. With age, many of the bones fuse, leaving 206 bones that make up an average adult skeleton.
When a substance is heated up, its particles move more and it takes up a larger volume – this is known as thermal expansion. The mercury level inside a thermometer, for example, rises and falls as the mercury’s volume changes with the ambient temperature. This effect is most dramatic in gases but occurs in liquids and solids such as iron too. For this reason, large structures such as bridges are built with expansion joints which allow them some leeway to expand and contract without causing any damage.
There are certain metals – including potassium, sodium, lithium, rubidium, and cesium – that are so reactive that they oxidize (or tarnish) instantly when exposed to air. They can even produce explosions when dropped in water! All elements strive to be chemically stable – in other words, to have a full outer electron shell. To achieve this, metals tend to shed electrons. The alkali metals have only one electron on their outer shell, making them ultra-keen to pass on this unwanted passenger to another element via bonding. As a result, they form compounds with other elements so readily that they don’t exist independently in nature.
Over the coming hundreds of millions of years, the Sun will continue to get progressively brighter and hotter. In just over 2 billion years, temperatures will be high enough to evaporate our oceans, making life on Earth impossible. Our planet will become a vast desert similar to Mars today. As it expands into a red giant in the following few billion years, scientists predict that the Sun will finally engulf Earth altogether, spelling the definite end for our planet.
Thermal cameras detect the heat lost by a subject as infrared, but polar bears are experts at conserving heat. The bears keep warm due to a thick layer of blubber under the skin. Add to this a dense fur coat and they can endure the chilliest Arctic day.
In space, light travels at 300,000 kilometers (186,000 miles) per second. Even at this breakneck speed, covering the 150 million odd kilometers (93 million miles) between us and the Sun takes considerable time. And eight minutes is still very little compared to the five and a half hours it takes for the Sun’s light to reach Pluto.
stomach digests food thanks to highly corrosive hydrochloric acid with a pH of 2 to 3. This acid also attacks your stomach lining, which protects itself by secreting an alkali bicarbonate solution. The lining still needs to be replaced continually, and it entirely renews itself every four days.
Earth’s inner core is a sphere of solid iron, surrounded by liquid iron. Variations in temperature and density create currents in this iron, which in turn produce electrical currents. Lined up by the Earth’s spin, these currents combine to create a magnetic field, used by compass needles worldwide.
Our Solar System started off as a swirling cloud of dust and gas which eventually collapsed into a spinning disc with the Sun at its centre. Because of this common origin, all the planets move around the Sun in the same direction and on roughly the same plane. They also all spin in the same direction (counter clockwise if observed from ‘above’) – except Uranus and Venus. Uranus spins on its side, while Venus defiantly spins in the complete opposite direction. The most likely cause of these planetary oddballs are gigantic asteroids which knocked them off course in the distant past.
A jumping flea reaches dizzying heights of about eight centimeters (three inches) in a millisecond. Acceleration is the change in speed of an object over time, often measured in ‘g’s, with one g equal to the acceleration caused by gravity on Earth (9.8 meters/32.2 feet per square second). Fleas experience 100 g, while the Space Shuttle peaked at around 5 g. The flea’s secret is a stretchy rubber-like protein which allows it to store and release energy like a spring.
The human genome (the genetic code in each human cell) contains 23 DNA molecules (called chromosomes), each containing from 500,000 to 2.5 million nucleotide pairs. DNA molecules of this size are 1.7 to 8.5 cm long when uncoiled — about 5 cm on average. There are about 37 trillion cells in the human body, so if you were to uncoil all of the DNA encased in each cell and place the molecules end to end, it would sum to a total length of 2×1014 meters — enough for 17 Pluto round-trips (the distance from the sun to Pluto and then back again is 1.2×1013 meters)
Like the ears of people, the grasshopper sound detector is a thin membrane called a tympanum, or “eardrum”. In adults, the tympanum is covered and protected by the wings, and allows the grasshopper to hear the songs of its fellow grasshoppers.