84% of the Earths volume is molten rock
Most of the Earth’s volume is contained in the mantle, a rocky layer 2,970 kilometres (1,845 miles) thick, sandwiched between the planet’s core and crust.
Despite temperatures approaching 4,300 degrees Celsius (7,772 degrees Fahrenheit) near the core, most of the mantle is solid due to the huge pressure it is under. Earthquakes are an important source of information about what lies beneath our feet. By studying how seismological waves spread through the planet, geologists can deduce its structure.
Certain waves, for example, can’t travel through liquids, leading scientists to conclude that the planet’s outer core is liquid.
Babies have around 100 more bones than adults
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. Conversely, a drop in temperature causes it to contract again.
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.
Butterflies’ hind feet, technically known as tarsi, are covered in chemoreceptors – tiny organs which allow them to taste something just by standing on it. This anatomical quirk enables a female butterfly to pick a leaf suitable for her caterpillars to eat before she lays her eggs. More generally, once it has spotted a tasty-looking flower, a butterfly can sample the goods quickly before settling down to feed.
Muscles can remember
The first time you perform an action -tying shoelaces, for example, it feels awkward, but with enough repetition it becomes second nature. The brain stores sets of motor instructions, allowing such tasks to be executed without conscious effort. Muscle memory is retained for a long time, so skills like driving a car are rarely completely lost.
Pumice is the only rock that can float
Pumice is formed when hot, highly pressurised lava is ejected from a volcano. The sudden drop in pressure and rapid cooling trap bubbles of gas in the rock, giving it a lower density than water.
Diamonds are carbon, with each atom bound with strong covalent bonds to four neighbours in a rigid lattice Diamonds tend to grow In octahedral shapes, and some of the octahedron’s faces are weaker than others. Jewellers can cut along these planes with special tools coated in diamond dust.
20% of Earth’s oxygen is produced by the Amazon rainforest
Our atmosphere is made up of roughly 78 per cent nitrogen and 21 per cent oxygen, with various other gases present in small amounts. The vast majority of living organisms on Earth need oxygen to survive, converting it into carbon dioxide as they breathe.
Thankfully, plants continually replenish our planet’s oxygen levels through photosynthesis. During this process, CO and water are converted into energy, releasing oxygen as a by-product. Covering 5.5 million square kilometres (2.1 million square miles), the Amazon rainforest cycles a significant proportion of the Earth’s oxygen, absorbing large quantities of CO at the same time.
The brain does not feel pain
We feel pain thanks to nociceptors – sensory receptors which send signals to the spinal cord and brain, alerting us to danger and enabling us to react. Nociceptors are found throughout the body, particularly just under the skin, but they are entirely absent from one place: the brain. When you have a headache, it isn’t actually your brain that’s suffering but the tissues around it which include muscles, sinuses and the membranes that protect the organ.
Some metals are so reactive that they explode on contact with water
There are certain metals – including potassium, sodium, lithium, rubidium and caesium – 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.
At any one time, over 98 per cent of our planet’s water is liquid, with ice making up a little under two per cent, and only a tiny fraction existing as vapour. Water is made of hydrogen and oxygen atoms, bound together as H20 molecules. Changing from one state of matter to another doesn’t involve any chemical changes but is a case of adding or removing energy as heat or pressure, affecting the behaviour of the H20. In liquid water, molecules move freely. Cool it down and, as they lose energy, the molecules slow down until the point where they form a rigid structure: ice.
Your blood vessels would circle the world two and a half times if laid end to end
Blood vessels are hollow tubes that carry blood around your body, delivering vital oxygen, nutrients and water. Arteries carry oxygen-rich blood away from the heart, minute capillaries deliver it to the tissues, while veins transport the deoxygenated blood and waste back to the heart for replenishing in the lungs. The biggest vessel – the aorta – is 3,000 times wider than the smallest capillaries, where red blood cells (which carry the oxygen) have to line up in single file to squeeze through. These red blood cells are unusual in that they have no nucleus, meaning they can dedicate even more space to transporting oxygen.
The 9m-long Stegosaurus had a brain the size of a walnut
This peaceful prehistoric herbivore was certainly big but not very clever. Animal intelligence is often estimated using the encephalisation quotient, or EQ, which compares an animal’s brain weight to that of other ‘typical’ similarly sized creatures. Cold-blooded animals usually have lower EQs than warm-blooded mammals, but Stegosaurus still lags in the dino smarts rankings, with smaller carnivores like Velociraptor occupying the top spots.
Blonds have more hair
The average blond has 140,000 hairs on their head, compared to 110,000 for brunettes and 90,000 for redheads. Blond hair tends to be finer than other hair colours.
Chalk is made of trillions of microscopic plankton fossils
Tiny single-celled algae called coccolithophores have lived in Earth’s oceans for 200 million years. Unlike any other marine plant, they surround themselves with minuscule plates of calcite (coccoliths). Just under 100 million years ago, conditions were just right for coccolithophores to accumulate in a thick layer coating ocean floors in a white ooze. As further sediment built up on top, the pressure compressed the coccoliths to form rock, creating chalk deposits such as the white cliffs of Dover. Coccolithophores are just one of many prehistoric species that have been immortalized in fossil form, but how do we know how old they are? Over time, rock forms in horizontal layers, leaving older rocks at the bottom and younger rocks near the top. By studying the type of rock in which a fossil is found palaeontologists can roughly guess its age. Carbon dating estimates a fossil’s age more precisely, based on the rate of decay of radioactive elements such as carbon-14.
Every day a human produces 300 billion new cells
Your body renews itself continually as old cells are discarded and new ones created. On average, cells live for eight years. Some, however, last just a few days, whereas others (like brain cells) are with you for life.
Electric eels get their spark from specialised cells called electrocytes. These create a negative charge of about -o.i volts by controlling the flow of ions across cell membranes. When an eel spots its prey, these thousands of tiny batteries join forces to deliver a mind-numbing shock.
Every living thing has at least one parasite living on/in it
The majority of species on Earth are parasites, including everything from cuckoos to intestinal worms, bacteria and viruses. These organisms have co-evolved with their hosts, developing an arsenal of tricks to take advantage of them. In fact, many consider parasites to be a dominant force that drives evolution.
Space is not a complete vacuum
A vacuum is a space utterly devoid of any molecules, particles or any matter. Yet even the deepest recesses of our universe contain a few hydrogen atoms and photons per cubic metre.
Hawaii moves 7.5cm closer to Alaska every year
The Earth’s crust is split into gigantic pieces called tectonic plates. These plates are in constant motion, propelled by currents in the Earth’s upper mantle. Hot, less-dense rock rises before cooling and sinking, giving rise to circular convection currents which act like giant conveyor belts, slowly shifting the tectonic plates above them. Hawaii sits in the middle of the Pacific Plate, which is slowly drifting north-west towards the North American Plate, back to Alaska. The plates’ pace is comparable to the speed at which our fingernails grow.
The surface area of the lungs is equivalent to a tennis court
The lungs facilitate gas exchange between the air we breathe and our blood, allowing oxygen to enter the body and carbon dioxide to leave. This exchange takes place inside 700 million alveoli, tiny hollow air sacs wrapped in an intricate network of blood vessels. The membrane across which the gases pass is about two micrometres (0.00008 inches) thick, 50 times thinner than a sheet of paper and its total surface area adds up to 70 square metres (750 square feet).
Lizards can walk on water
Fringes of skin on the outer edges of the Central/South American basilisk lizard’s hind toes increase the feet’s surface area, making this impressive trick possible. The lizard slaps its feet down as it runs, creating an upward force and trapping bubbles of air. Its feet also push sideways, helping it to stay upright.
Our universe is growing continually, with the space between objects expanding just like an inflated balloon. This fact wasn’t discovered until the 1920s, when Edwin Hubble observed that distant galaxies are rushing away from us. Not only that, but the farther a galaxy is from us, the faster it moves away. This groundbreaking observation also implied that the whole universe must once have been contained in a single point, giving rise to the Big Bang theory. According to this model, the cosmos was born 13.7 billion years ago, with all its energy compressed into one incredibly hot and dense point which has been expanding and cooling ever since.
Even more surprisingly, the universe’s expansion is accelerating. The reason behind the universe’s swelling has been dubbed ‘dark energy’, but very little is known about this mysterious force which is thought to occupy a staggering 70 per cent of the universe.
At light speed it would take 2.5 million years to reach our galactic neighbour
Andromeda is one of our galaxy’s closest neighbours, but popping over to borrow some sugar would be quite a trek. By measuring the apparent brightness of its stars, astronomers have estimated that Andromeda is 2.4 x 10on9 kilometres (1.5 x 10on9 miles) away. To avoid drowning in zeros, scientists prefer to measure such distances in light years. As its name suggests, a light year is the distance travelled by light in one year – in other words, a whopping 9.5 trillion kilometres (about six trillion miles) -making Andromeda 2.5 million light years away.
While trees grow mostly from the end of their branches, bamboo is actually a grass, so it grows very differently. A bamboo shoot is split into segments which can all host cell division (ie growth), allowing the bamboo to extend a bit like a telescope Equally vital to its record-smashing growth rates (60 centimeters/24 inches per day) is the plant’s rhizome, an underground network of roots connecting a cluster of canes. Like all plants, bamboo gets its energy from photosynthesis, but the rhizome enables it to distribute nutrients and water where they are most needed.
Early humans date back up to 7 million years
It’s difficult to define the point when our ancestors became ‘human’, but one important milestone A occurred when the human lineage diverged from that of our closest living relatives: chimpanzees. The last ancestor we shared with chimps lived about 7 million years ago -a relatively short time ago in the 2 billion odd years since life first appeared on Earth. Since then there have been 15-20 different species of early hominid. Another key chapter in human evolution was the beginnings of bipedalism – the ability to walk on two feet. Australopithecus was the first genus to accomplish this feat around 4 million years ago in eastern Africa. It wasn’t until 2.4 million years ago that the Homo genus appeared. Their distinguishing feature was a bigger brain and they were the first of our ancestors to use stone tools. Homo sapiens are only about 200,000 years old, emerging in Africa before migrating across the globe.
Gravity is only 3% weaker 100km above the Earth
According to the laws of gravity, any two objects with mass attract each other. For this effect to be noticeable, one of the objects needs to have a considerable mass; at roughly 6 x io24 kilograms (1.3 x 1025 pounds), our planet fits the bill nicely. Gravity decreases the farther you are from Earth’s centre, but given that standing on its surface you are already 6,370 kilometres (3,960 miles) away from the core, a 100-kilometre (62-mile) increase makes a relatively small difference. Air pressure, on the other hand, is caused by the sheer weight of the air molecules above you. Standing at sea level, the air above you causes a pressure equivalent to about 1,000 kilograms (2,205 pounds). Luckily this pressure pushes on us in all directions. Water weighs about 800 times more than air, so exerts a far greater pressure; in fact, at just ten metres (33 feet) underwater, the pressure would be double.
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
Stomach acid is strong enough to dissolve razor blades
Your 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.
Alpha radiation can be deadly but a sheet of paper can stop it
As an unstable radioactive atom decays, it ejects particles and energy, producing alpha, beta and gamma radiation. Alpha particles carry the strongest charge so can cause the most harm. Their large mass, however, stops them penetrating very far into matter, so they’re only likely to cause damage if ingested.
The Earth is a giant magnet
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.
Nerve impulses can travel as fast as 200mph
Electrical signals are the body’s principal means of communication, controlling everything from your heartbeat to pain. The nervous system is a network of millions of neurons – tiny messenger cells which transmit information using electrical signals called nerve impulses. By controlling the flow of ions, each neuron can build up an electrical charge and transmit it down its axon, a long branch which passes the impulse on to the next neuron. The speed of nervous impulses varies but the fastest signals are carried within motor neurons. These relay messages from the brain telling muscles to contract.
The difference between tides can be as great as 17m
The extreme tides in eastern Canada’s Bay of Fundy are caused by tidal resonance. All over the globe, high tides occur every 12 and a half hours. The Bay of Fundy is peculiar in that it takes 13 hours for seawater to slosh into the mouth of the bay, to its head and then back out to sea, roughly matching the rhythm of the tides. As each tide rises, it therefore amplifies the water’s sloshing motion – just like someone giving a child on a swing a small push at just the right moment. These two bulges result in two high tides, which sweep around the globe at intervals of 12 and a half hours.
Known as the law of conservation of energy, this principle is key to understanding our entire universe. Energy can’t be created or destroyed, but it can change form. Think about a moving car, for example. Chemical energy contained in the fuel is converted into mechanical energy by the motor. This propels the car forward, transforming into kinetic energy.
Step on the brake and this energy is converted into heat and sound. Energy sometimes seems to disappear, but this usually means it is being stored as potential energy, like a stretched spring. Although energy is never destroyed, it can be Most’ when converted into unwanted forms, eg a traditional light bulb expends lots of energy as heat rather than light.
Sound moves faster in water than air
Sound is a vibration. It travels as a compression (or longitudinal) wave when particles (molecules or atoms) collide with one another, passing on the vibration. Sound therefore can’t cross a vacuum but needs a medium to pass through, and its speed is determined by the properties of that medium. In general, sound travels fastest in a solid, then a liquid and slowest in a gas. Inside a solid, particles are packed tightly together, meaning vibrations are passed on easily. In a liquid particles are more spaced out, making it harder for vibrations to be transmitted from one particle to the next, but they can travel faster than when passing through a gaseous medium like air.
Stretching from the north-east coast of Australia, the Great Barrier Reef is the world’s largest coral reef system. The 2,600-kilometre (1,616-mile)-long structure is made of millions of tiny living animals -coral polyps – whose hard calcium carbonate exoskeletons give the reef its structure. Like all coral reefs, the Great Barrier Reef provides an incredible range of marine habitats. As well as 400 species of coral alone, the Great Barrier Reef supports thousands of other animals and plants including over 1,500 fish species.
If you could drive up, you’d arrive in space in about an hour
The Karman Line at 100 kilometres (62 miles) in altitude is generally accepted as the boundary of space. Driving at a leisurely 90 kilometres (56 miles) per hour, a trip to space would therefore take just 67 minutes.