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Crikey, this is a question and a half!
Firstly, just to check whether you mean the mantle – the deep layer of mostly-solid, very slowly moving material which makes up most of the Earth’s inside, or the core – the part solid, part liquid metallic mass at the Earth’s centre, which generates our magnetic field and most of the heat.
The short answer is – nobody is sure (reference 1, for a snapshot of the un-moderated debate). Another short answer is - it won’t, for a long long time. The heat inside the Earth (5400 degC) is maintained by radioactive decay and it cools by only about 100 degC per billion years… (reference 2).
A slightly longer answer would be to look at a planet like Mars, where (because it is smaller) it is thought that the interior cooled down much faster than on Earth. Although the core of Mars is still hot (reference 3), the heat flow out from it is too weak to make the mantle soft enough to move (convection) and so there is no longer any plate tectonics or volcanism on Mars.
If the same happened on Earth, there would be no volcanoes, no big earthquakes, no mountains, no continental drift… eventually erosion would wear down the land and we’d probably become completely covered with water. Except, that the magnetic field of Earth may also become less strong; then radiation from the Sun would be able to reach our atmosphere and slowly ‘blow’ it off into space; and as that happened, then the water would likely also be lost – we would be a dry, airless, barren world.
It is important to understand that this is all just conjecture – even now scientists are unsure of the exact workings of the Earth’s interior and its role in our planet’s ability to sustain life. But it does seem clear that, as with the rest of the Earth system – if the core wasn’t the way it is, life as we know it wouldn’t have evolved!
Answered by Dr Jonathan Bridge
Centre for Engineering Sustainability
University of Liverpool
Since 1969, the distance to the Moon has been almost continuously measured using lasers (reference 1). When the Apollo astronauts visited the Moon, they left reflectors (a bit like very good mirrors) there. Strong lasers shone at the moon from Earth are bounced off these reflectors in a certain way, so that scientists can clearly detect the light as it comes back to Earth. This takes advantage of the special properties of lasers which have light only at a specific wavelength which can be precisely monitored (reference 2).
Since we know that laser beams travel at the speed of light, it is possible to work out the distance to the Moon based on the time it takes (about 2.5 seconds) for the light to travel from the Earth, to the Moon, and back again. Interestingly, before the laser experiment and as long ago as Ancient Greece, the distance to the Moon was calculated by taking careful measurements of its movement in the sky and using trigonometry, somewhat like you learn in Maths at school!
The Greek astronomer Hipparchus (reference 3) calculated that the distance was around 61 Earth radii – or about 390,000 km. Amazingly, the actual distance measured using the high-tech laser method ranges from 356,700 km to 406,300 km (because the Moon’s orbit is not a perfect circle) – so Hipparchus was more or less spot-on! Which goes to show that good science is about careful observation and intelligent thinking, not just about having the best equipment!
Answered by Dr Jonathan Bridge
Centre for Engineering Sustainability
University of Liverpool
(Question submitted by Louis)
What are the most intelligent animals in the world? Question submitted by Louis
This is an interesting and difficult question to answer because it is hard to properly describe what ‘intelligence’ means when it comes to the animal kingdom. Humans are often considered to be the most intelligent animal on the planet, and so other animals are often compared to us when we think about intelligence. Many animals are able to think creatively to solve problems and puzzles, can use tools like we do and can effectively communicate (or talk) with one another. So with that in mind, here are my top six most intelligent animals in the world. Let’s see if you agree with me!
1. Great Apes
Closely related to humans, the Great Apes are considered to be among the most intelligent animals on Earth. Orangutans, chimpanzees and gorillas cleverly use tools for finding food and for overcoming obstacles. For instance, chimpanzees have often been seen using sticks like fishing rods in order to catch termites, while gorillas have been seen using sticks to measure the depth of water before crossing a swamp. Use of tools in these ways suggests that these animals are highly intelligent. Further, all of the Great Apes are highly skilled at communicating (talking) with other members of their family groups and even with humans. Chimpanzees use hand gestures, facial expressions and their voices to make a range of sounds for communication, similar to the way that we talk to one another. Gorillas and Orangutans are so intelligent that they have even been taught to use sign language to speak to their human keepers!
2. Dolphins and Whales
Dolphins are tremendously talented at imitating (copying) and can be trained to perform complex tricks. Like pigs, they can recognise themselves in a mirror. Dolphins also make clever use of their surroundings. In fact, some wild bottlenose dolphins have been caught tearing off bits of marine sponges that grow on the sea floor and using the pieces of sponge to cover their noses so that they can hunt for fish among sharp coral. The sponge offers protection to the dolphin’s nose and helps to stop it becoming scratched by the coral – a bit like putting shoes on your feet before walking on stones!
Toothed whales are close relatives of the dolphin and are very intelligent too. Scientists in the USA reported that a Beluga whale called Noc suddenly began to copy human speech patterns with no training. He seemed to recognise that these noises came from humans as he only made these calls when humans were around. Noc’s ability to ‘speak’ was discovered when a diver in his tank heard someone tell him to get out of the pool. It was Noc!
Along with dolphins, whales and the Great Apes, elephants are often considered to be among the most intelligent animals on the planet. Elephants have excellent memories, can recognise themselves in a mirror, can solve complicated problems – for instance, working as a team to reach food that would be too far away for one elephant alone – and use sticks and tree bark as tools to help them get food and water or as fly-swatters! Like many other intelligent animals, elephants keep themselves entertained by playing. This often involves squirting water with their trunks. They are also talented imitators and can learn to repeat sounds to talk to other members of their family group. One elephant, named Kosik, from South Korea has even learned to copy the sounds of the Korean words for ‘yes’, ‘no’, ‘sit’ and ‘lie down’.
Octopuses are very smart creatures that are extremely good at problem solving. Scientists have studied the way that an octopus selects its food when given a choice between mussels or clams. Mussels are easier to open than clams, so the octopus tends to select mussels as its first choice because it can get the most food for the least effort this way. The octopus can tell the difference between the clams and mussels, and it knows that it has to use a different method to open each of the shellfish. In scientific studies, octopuses have been shown to quickly solve puzzles – for example opening a box or jar to reach food inside – and can remember how to successfully find their way through a maze. In the wild, they can leave their den to go hunting and will remember how to get back home again. This tells us that they have what is called ‘spatial memory’. Because they are intelligent and get bored easily, octopuses are curious animals and will investigate and play with objects in their environment. In aquariums, this playful behaviour can involve destroying all sorts of things like thermometers and water pumps, and even stealing fish from neighbouring tanks!
When thinking about intelligent animals, the pig might not be an obvious choice - but it should be! Pigs can be trained and are even kept as pets by some people. Interestingly, scientists have shown that young pigs see and respond to reflections in a mirror placed in their pen; this is quite a rare ability among animals. In one experiment, a mirror was placed in an enclosure so the pigs could see a reflection of food but could not see the food directly. The scientists noticed that the pigs that had not seen a mirror before looked for the food behind the mirror, while the pigs that had seen mirrors before recognized that the food was a reflection and set off in the opposite direction, finding the food in less than 30 seconds. This suggests that pigs are capable of fast learning and that they are quite intelligent.
Finally, the humble crow is also a highly intelligent animal. Scientific studies have shown that crows are able to make and use tools to solve puzzles at a level similar to that of a 5-year-old child! Crows can also modify existing tools to make them more suitable for solving a particular problem or puzzle, such as bending a wire to make a hook that can be used to scoop out food from a tube. People have also observed crows throwing nuts onto the ground and waiting for cars to drive over them, breaking the shells open. The clever crows then wait for a red light to stop the cars before swooping down to claim their prize! Smart or what?
Answered by Dr. Suzanne Humphrey, University of Liverpool
Planets are spherical (round) in shape due to the effect of gravity. When the solar system was forming, the planets formed from clumps of gas and dust, which under the force of gravity, attracted more material and so grew larger.
The new material would impact into the "proto"-planet (meaning original) causing the material to become molten due to the heat generated by the impacts.
Gravity then pulls the material into the smallest possible space, which in the vacuum of space is a sphere. Planets however are never fully spherical, due to rotation.
Rotation acts against the force of gravity, which causes them expand at their equator.
Also large bodies, such as the sun can cause the planets to warp due to their strong gravitational pull.
Answered by Neil Mawson, Liverpool John Moores University
(Question submitted by James)
Thank you for the excellent and interesting question. Scientists have been trying to answer this for many years using two main methods.
The first is the discovery and study of fossil remains and the second is the study of human genetics. The oldest known fossils of our species Homo sapiens come from Ethiopia and were found in rock which has been dated to approximately 195,000 years old. They look very much like us in their anatomy.
Scientists have also been looking for clues as to how old our species is through studying our DNA. From studying DNA of many different individuals from all around the world and examining the differences between them, they have concluded that all humans share ancestors who lived in Africa about 200,000 years ago.
The study of human evolution is called palaeoanthropology. What we know about human evolution changes all the time due to new fossil discoveries, so keep on watching the news and the internet to see if there are any new developments in this field.
Answered by Dr Laura Bishop, Professor of Hominid Palaeoecology, Liverpool John Moores University
Copper (chemical symbol Cu) is a soft metal which conducts electricity and heat very well.
The most common use of copper is as wire in electrical appliances, because of it excellent electrical conductivity.
Copper is also used to make coins. Pennies and two-pences made before 1992 are 97% copper and later ones are made from steel with a thin layer of copper.
Other uses involve the antibacterial properties of copper, as copper-zinc alloys (a metal mix of copper and zinc) can kill bacteria on their surface, and so are used in hospitals, schools and other public areas in plumbing, pipes and handrails.
Copper is obtained from its ores. This is done using a number of physical, electrochemical and chemical processes. The exact method depends on the ore source and the country in which it is being extracted (as different countries have different regulations). Generally, the ore must be concentrated by crushing it. It is then roasted, so it oxidised to produce an copper sulphide or oxide and these are then smelted down. This final product is then refined using electrolysis.
As iron is a magnetic substance, when it comes into contact with a magnet at room temperature, the magnet will attract the iron and they will effectively stick.
The melting point of a substance depends on both temperature and pressure. The temperature of the core is high enough to cause melting, but on the other hand, the pressure at the core of the earth is very large and therefore the melting point is also greater... so great that the core remains a solid.
A few readers have emailed in their questions about how salt is made.
Salt is found mostly underground in rocks and also dissolved in sea water. To get the salt from the sea, you have to collect sea water in shallow ponds and let the wind and sun dry out the water naturally, leaving only the salt behind. This is called solar evaporation, and the salt can form in layers up to 30 cm thick.
However, as the concentration of salt in the sea is about 3%, a great deal of energy is needed to produce dry salt, and it is only feasible in hot, dry areas.
In northern regions, salt is usually produced from solid deposits of rock salt. These deposits were formed from the evaporation of shallow seas in hot, dry climate, around 200 million years ago and occur in many regions of the world. In the North of England we have deposits in mid-Cheshire (in Northwich and Winsford).
The extraction process involves injecting hot water into these underground deposits of salt, which dissolves the salt, and the resulting concentrated solution (brine) is pumped out. The saturated brine (26% NaCl or sodium chloride) is then boiled in large vessels called effects.
Steam is used to heat the brine in chambers called calandrias. To save energy, there are lots of chambers linked together at different pressures. As the boiling point of water decreases with decreasing pressure, you only need to heat the first chamber, and the steam from the first will heat the second chamber, and so on.
This means that the final evaporation chamber is under vacuum. For this reason, the salt made in this process is called vacuum salt. This is what happens at the INEOS salt plant in Runcorn.
The first product of the evaporation process is a mixture of salt in brine. This is then centrifuged (spun round very fast) to give a slightly damp salt called Undried Vacuum Salt which is largely used by the chemical and water treatment industries.
Some of this salt is further dried to give Pure Dried Vacuum Salt (PDV). This product is used for industrial water softening, the cosmetics industry, food and many other applications.
Did you know?
The word “salary” comes from the Roman times, when soldiers were given money to buy salt!
(answered by Daniel Colquitt, University of Liverpool)
To understand why water expands when it is close to its freezing point, we have to look at how the water molecules interact with each other. A single water molecule it made up of two Hydrogen atoms and a single Oxygen atom (Click here for a picture http://www.lsbu.ac.uk/water/images/molecul2.gif (taken from lsbu.ac.uk)). The two Hydrogen "ears" are positively charged, whilst the Oxygen "head" is negatively charged. Now, opposite charges attract so each negatively charged "ear" will attract a positively charged "head", this makes the water molecules want to group together. Unfortunately, when water is warm its molecules have so much energy that they bounce around randomly so that the attractive forces between the "ears" and "heads" can't keep groups of molecules together. Imagine making popcorn in the microwave: before you put in the bag in the microwave the popcorn is cold and just sits at the bottom of the bag, all clumped together. When you heat the popcorn in the microwave, it starts flying around inside the bag, bouncing around randomly.
Now, the reason water expands when it cools down is that instead of just forming clumps like the popcorn, the water molecules form a special structure. Since each molecule has two "ears" and one "head", each molecule of water wants to be next to two "heads" and one "ear" from other water molecules. This means that, when cooled, water molecules arrange themselves into an hexagonal structure. If we take a look at this picture http://media.web.britannica.com/eb-media/90/62690-004-1FB5CC40.gif (from Encyclopædia Britannica, Inc.), we can see that the same number of water molecules take up more space in the hexagonal structure of ice (left), than in the random structure of water (centre). This means that when all the water molecules are in this hexagonal structure, the same amount of water takes up more space than when the molecules are arranged randomly. This is why water expands when it freezes.
The fact that water expands when frozen is very important, particularly for aquatic life. For example, the fact that ice is less dense than water means that any water the freezes in a pond always floats on the surface, whilst the water underneath remains liquid. This means that the fish in the pond don't get crushed by the ice or forced up to the surface. It is also useful because the layer of ice which forms on the top of a pond insulates the water from the cold, which helps prevent the water underneath from freezing.
However, the expansion of frozen water can also have some negative effects. For example, in winter if the water insider water or central heating pipes freeze, it will expand and can cause pipes to burst.
Challenger Deep in the Marianas Trench is the deepest place in the ocean at nearly 11 kilometres. The trench formed because when tectonic plates (pieces of the Earth’s crust that fit together like a jigsaw) meet each other, one is sometimes bent underneath the other, and the boundary forms a long deep trench under the oceans. We know the exact depth because scientists sent down a submersible (a type of submarine made for really deep journeys) right to the very bottom.
Did you know?
If you were standing at the bottom of the ocean in Challenger Deep, the pressure of all the water would feel like 50 jumbo jets on top of your head!
The short answer is very hot! The temperature of a volcano depends on what you measure. If you measure the temperature of the gases that can come out of the ground by a volcano, these can be high enough to boil water. Chunks of rock that have been blasted out the top of a volcano (called pyroclastic deposits – from the latin ‘pyro’ meaning fire and greek ‘clast’ meaning broken) can be as hot as 200°C.
If you measure the lava (hot melted rock) that flows out of a volcano, then this can be anything from 700°C to 1200°C. Compare that to the hottest setting of 240°C in your oven at home!
Did you know?
One in 10 people live in the danger zone of an active volcano!
(Question submitted by Jess)
The simple answer is that if you mixed them at room temperature not a lot would happen. You would have to have very high temps for a reaction. Beryllium Chloride is a compound which is slightly unusual compared to similar group 2 compounds so I suggest this link which gives a little more detail:
Also have a look at the 118 videos from Professor Poliakoff on each element in the periodic table at: www.periodicvideos.com
(Answered by Sue Halliday - Catalyst Science Discovery Centre)
(Question submitted by Craig)
This is a great question as the answer isn’t as straightforward as you think. Not only are there loads of different ways to measure how big something is, the size of the Sun will be different in the future than it is now! Read on…
Here are three ways of measuring how big a sphere is (the shape of the Sun is called a sphere):-
Diameter – this is the measurement from the two furthest points on the surface of a sphere, passing through its centre (for example the distance between the North and South pole on Earth right through the middle). The diameter of the Sun is 1.4 million kilometres, or to put it in perspective, 109 times bigger than that of Earth!
Surface area – this is how much exposed area a solid object has. For the Sun, this is 6.0877×10^18 square metres, or put more simply, 6,087,700,000,000,000,000 square metres! That’s 11,990 times larger than the Earth!
Volume - the amount of space an object takes up - shows just how big the Sun is. The volume of the Sun is estimated at 1.412×10^27 cubic metres, or 141,200,000,000,000,000,000,000,000 cubic metres! To compare this with our planet, you could fit 1.3 million Earths inside the Sun!
The life-cycle of the Sun
The Sun is about half-way through its life, and is thought to be around 4.5 billion years old. In about 5 billion years, the Sun will become a red giant star which will be about 400 times bigger (in diameter) than it is at the moment. This is because all the hydrogen that is being burnt up in the Sun’s shrinking core will make its hot outer gases expand. After this, the Sun will cool down and become a much smaller white dwarf, which is made up of the remains of the core of the star.
Find out more at: http://www.bbc.co.uk/science/space/
(Question submitted by Lamese, Ciara and Alice)
When you say ‘burn’ I suspect you mean ‘combust’ (set on fire). Combustion is a chemical process that requires a fuel and some oxygen. Most ‘fuels’ that are burnt in this way are or used to be alive – wood and paper come from trees for example.
Living and ex-living things store up the energy they originally got from sunlight and then let it go when they burn. Most rocks originally came from deep inside the Earth and were never alive – they can’t be ‘burnt’ because they don’t have this type of energy available for release. An important exception is coal which is a rock and which can be burnt very easily. In fact, it is burnt everyday in power stations all over the world and the energy this burning releases provides much of the electricity we use.
Why does coal burn when other rocks don’t? The answer is that it was once alive – coal is a rock made up of the remains of plants and other living things which died, in most cases, hundreds of millions of years ago.
The word ‘burn’ can also be used in a broader sense to describe the alteration of something by a lot of heat. Think of how toast ‘burns’ (becomes hard and black) without having to catch fire if you accidentally leave it in the toaster for too long. Most rocks will start to melt into liquid at about 1,000 degrees Celsius but even well below this temperature, they can change colour and hardness just like toast. Geologists sometimes refer to rocks that have been altered by heat in nature (from a nearby volcano for example) as ‘burnt rocks’.
(Answered by Dr. Andy Biggin - Geophysicist at University of Liverpool)
(Question submitted by Priyanka Lad)
Coal is a rock which is formed from the dead remains of plants that have been buried over many years under water. Over time, the plant matter becomes squashed and buried under sand and other rock and in the end turns to coal. The coal traps carbon from the atmosphere from when the plants were alive.
When you burn a lump of coal in air, the carbon it contains joins with the oxygen in the air and forms a gas called carbon dioxide. People burn coal to heat their fires and also to generate electricity through the use of burning the coal in an oven which heats a boiler to produce steam and drive steam turbines which can generate electricity.
If you burn coal in an enclosed space, there is not enough oxygen to make carbon dioxide and so another gas called carbon monoxide is formed, which can be dangerous to humans and animals.
If you want to know more about Carbon and Oxygen, why not visit the Video Periodic Table at http://www.periodicvideos.com/ ?
Electricity is a form of energy that comes from tiny charged particles in an atom (called electrons) which flow around in a path. This movement is called an electric current, and although we can’t see this, we can see the effects it makes, like powering a light bulb or phone.
Electricity can be made by using generators, which change one type of energy into electricity. For example, by changing water power into electricity using a hydro-electric power station, or by burning coal or oil to heat water (the steam drives the generators to make electricity).
Another good example of electricity generation is wind power. The wind causes the propellers of a wind turbine to move and this movement in changed into electricity.
The Future Flower at Widnes uses wind energy to power the red lights on its petals!
(Question submitted by Kendal)
The Earth is made up of layers (a bit like an onion), with a thin crust on the outside, then a semi-solid mantle and then the core. The outer part of the core is liquid, because of the hot temperatures that keep the material molten. The inner part of the core is solid because at that depth, the pressure of all the rocks above is so great.
The source of the heat in the earth is thought to come mostly from the radioactive elements in the mantle (the layer between the core and the crust), but some heat comes from what was already there when the Earth formed (the crust that formed kept in the heat, like a blanket).
We can’t measure the temperature at the core directly, but because we think it is made mostly of iron, we can do experiments to compare how other materials behave at different temperatures and pressures, and guess at what temperatures iron melts at the same pressures as the core. The answer could be somewhere between 4000 and 7000 degrees C, but nobody really knows yet.
The Earth is cooling all the time, and as it does the liquid outer core freezes and a little bit more becomes solid. One day, the Earth will cool down completely, like the Moon has already.
See the other questions about the Earth further down the page!
Carbon Monoxide (CO) can be formed when there is not enough oxygen in the atmosphere to form Carbon Dioxde when organic matter like oil or coal is burned. For example, this could be from a oven or heater in the home where there is not enough ventilation (free flowing air) around.
CO can join up with haemaglobin (the protein in our blood which helps to carry oxygen around our bodies) and make a new compound. This means that oxygen can no longe combine with the haemaglobin and parts of the body are starved of oxygen.
Low levels of CO can cause headaches, dizzyness and short of breath, but higher levels could cause memory-loss, heart problems and even death.
Because we can't see, smell or taste CO, it is best to have a detector put near any machines that may produce CO and warn us when levels are too high.
Since 1930, everyone thought that Pluto was the furthest planet from the Sun in the Solar System.
However, in 2006, another small object called 2060 Chiron was found in the outer Solar System and then many more similar ones were discovered, one called Eris which is bigger than Pluto (Pluto is actually smaller than the Earth's moon).
Scientists then defined the word 'planet' for the first time, and Pluto along with other small objects, were now called 'dwarf planet's.
This means there are only 8 planets in the Solar System, with Neptune being the furthest one away from the Sun.
Beryllium is obtained from two minerals called bertrandite and beryl with nearly all the world’s supply coming from a mine in Utah, USA.
Beryllium is very reactive towards oxygen and water, and so is not easy to obtain and purify. The current industrial method involves reaction of the ore with hydrogen fluoride to form beryllium fluoride which is then reduced using magnesium metal.
Beryllium is also found in aquamarine and emerald precious stones.
Berylllium is used in making alloys to make softer cheaper metals such as copper harder. Because beryllium is light and stable at very high temperatures it has been used in rocket nozzles and space telescopes. It is also fairly transparent to X-rays and other ionizing radiation so has been employed for windows for radiation and particle physics experiments. For example, it has been used to make components around detectors in the Large Hadron Collider.
Applications of beryllium metal are limited because beryllium-containing dusts are very toxic.
A vacuum cleaner has a fan inside, like an aeroplane’s propellers, that is powered by an electric motor. When the blades of the fan turn around, the air particles are forced away from the fan and the air pressure drops behind the fan.
Because this air pressure is less than the normal air pressure outside the vacuum cleaner, the fan sucks in air particles from outside and out through the back of the cleaner. Because of this difference in pressure, there is a space where there is less air particles than normal – this is called a vacuum and gives the cleaner its name.
The flowing air particles hit loose dust and dirt and the friction they make, carries the dust into the vacuum cleaner. Rolling brushes on the bottom of the cleaner help to knock the dust from the floor into the moving stream of air.
Inside, a filter bag, with holes big enough to let air particles through, but small enough to trap dust and dirt particles helps to keep all the dirt inside the cleaner.
Because it’s the movement of air that makes a vacuum cleaner work, it doesn’t have to be just oxygen; any gas would work. Because the air in our atmosphere is mostly nitrogen (78%) and oxygen (21%), then you could say that oxygen is used by vacuum cleaners, but it’s mostly nitrogen instead!
This is a good question as the Earth’s core is gradually solidifying as it loses heat and freezes. To read more about this, take a look at the answer to the question below: “How do we know the Earth's core is so hot?” Billions of years from now, the planet may have cooled so much (by losing heating to space) that the core will be entirely solid. This may have already happened to our neighbouring planet Mars which is around the same age as the Earth but which has cooled down much more because of its smaller size (about half the radius of Earth or one-seventh of its volume).
One of the most dramatic effects of the Earth’s core solidifying would be that the huge magnetic field that is generated there will die. This is because the magnetic field relies on the motion of the electrically-conducting iron liquid in the outer core (motion caused by its cooling by convection and by the rotation of the planet) to generate it. There is evidence that Mars had its own magnetic field but that it died around 4 billion years ago because the core became too cold to continue generating it. A planet’s magnetic field protects its surface and atmosphere from particles fired out by the sun (called the solar wind). Mars’s atmosphere is much thinner than the Earth’s in part because it does not have the protection of the magnetic field. So a short answer to your question is: if the core solidifies, the magnetic field will die and the atmosphere will be more prone to being blown away by the solar wind. However, by then this may be the least of our worries. The sun is expected to change from being a yellow dwarf star to being a red giant in the next few billions of years. When this happens, the entire planet will be gobbled up by it, magnetic field or not.
(Answered by Dr. Andy Biggin - Geophysicist at University of Liverpool)
This question can be answered in many ways, depending on what you mean by the most common country.
In terms of coal reserves (how much un-mined coal a country has), USA has the biggest coal reserves; 246,643 million tonnes, which is 27% of the world’s reserves.
This is followed by Russia and then China.
In terms of the largest coal producers, China is the biggest, producing 42.5% of the world’s coal (2782 million tonnes in 2008). This is followed by USA and then the European Union.
Australia is the largest exporter of coal, exporting 25.6% of the world’s coal in 2008 (252 million tonnes). Indonesia is the second largest coal exporter, and Russia is the third.
However, Japan is the largest coal importer, importing 19.4% of the world’s coal in 2008 (187 million tonnes). South Korea is the second largest coal importer, and India is the third.
When oxygen is cooled below -182.96 °C, it becomes a liquid of a pale blue colour.
Liquid oxygen is made by cooling and compressing air in an air separation plan. When the cooled air is warmed up, nitrogen will evaporate leaving the liquid oxygen.
Oxygen in its liquid state has many uses.
In the space industry, liquid oxygen is used in rocket fuel as a propellant, mixed with liquid hydrogen. This is because it is a powerful
oxidsing agent, that is, organic matter will buurn quickly in liquid oxygen. It has been used in the main engines of the Space Shuttle
In the aerospace industry, it can be used to provide breathing gas for military and commercial pilots.
In medicine, liquid oxygen can be used to improve the availablity of oxygen in conditions of, for example, surgical trauma, shock, carbon monoxide poisoning, or resuscitation of critically ill patients.
Average winter temperatures are around -34°C and average summer temperatures are around 0°C.
Compared with the South Pole, the North Pole is relatively warmer, because it is at sea level in the middle of an ocean, rather than high up in a land mass, as the South Pole is.
(Submitted by Azam & Adam)
When playing your xBox 360 or any other type of hand held gaming console controller, you are mostly using the muscles of your thumb and any one or more of your fingers.
The nine muscles of the thumb are split into two groups, extrinsic (those that start in your arm) and intrinsic (those that start in your hand).
If you use the controller too much, you may start to feel some discomfort in your thumb and finger muscles. This is a form of injury known as Repetitive Strain Injury (RSI) and can lead to stress of the tendons, nerves and ligaments in your hands.
In the gaming world, this type of injury is jokingly called ‘gamers’ grip’, Playstation Thumb or ‘Nintendonitis’(!), but it’s not just gaming consoles that are to blame. Repeated texting on your mobile can lead to the same type of problems.
The mantle is a layer of the Earth which starts about 60 miles below the surface, and directly below the Earth's crust.
It is mainly made of a green coloured rock called peridotite. Because of the high temperatures and pressures at this depth, the mantle is plastic, which means that it flows very slowly.
This behaviour is the same as that of glass, which can also flow very slowy over time.
It is this plastic property of the mantle which helps the more rigid plates of the Earth's crust move about (called plate tectonics, or continental drift).
We think the Earth's heat comes from radioactive isoptopes in the mantle releasing energy that were present when the Earth was first formed.
Other heat is thought to be gravitational heat (from friction caused by heavier elements sinking down and lighter ones rising up).
Once the heat source ruins out, the core and the mantle of the earth will become solid and the Earth will be like the moon is now - a cold, dead planet.
(Question submitted by Andrew)
The temperature of lava as it erupts from a volcano can reach up to 1200 Celsius. The melting point of ceramics (pottery) is normally more than this (the exact temperature depends on what recipe has been used to make the ceramic) so no, lava won’t melt ceramic. Part of the process to make ceramics is baking in a kiln to very high temperatures.
Did you know?
In Mexico City ,lava flowed over ancient settlements and baked pieces of ceramic pottery that were there? We know that they were heated to over 600 Celsius as the magnetic information they contain was completely reset by the lava flow. It was not however hot enough to melt them.
(Answered by Dr. Mimi Hill - Geophysicist at University of Liverpool)
Scientists think that the temperature at the centre of the Earth isbetween 4000 and 7000 degrees Celsius. We can’t measure the temperature at the core directly, but because we think it is made mostly of iron, we can do experiments to compare how other materials behave at different temperatures and pressures, and guess at what temperatures iron melts at the same pressures as the core.
The temperature inside the Sun is though to be around 13.5 million degrees Celsius! This is the temperature at which nuclear fission can happen, hydrogen atoms fuse together to form Helium atoms. Huge amounts of energy are released by this reaction, and this energy travels out towards, cooling to around 6000 degrees Celsius at the surface of the Sun.
The huge amount of energy that is released by this fusion process is mainly due to the vast size of the Sun, rather than the production power (which is similar to the heat generated by a compost heap).
So, the centre of the Sun is much, much hotter than the centre of the Earth!
It is a very bad idea to taste beryllium as it is very toxic.
At some time someone must have tasted it because the early name was glucinum ( as in glucose) due to the sweet taste, but scientists have done things in the past that we would never do now!
So don’t try it!!
(Question submitted by Alex)
The geographic poles of the Earth are either end of the Earth's rotational axis (the line that the Earth's spins around). They are called the North and South pole. The magnetic poles are also at near to the geographic poles, but not quite. This is because, even though the spinning of the Earth helps to produce the magnetic field, through electrical conduction in the metal liquid outer core, the magnetic poles will 'wobble' a bit and can wander slowly around the geographic poles (this is called 'secular variation'). So, over thousands of years, the average position of the magnetic poles is similar to the geographic poles, but at any point in time, they are a bit off.
Did you know?
On some planets like Uranus, their magnetic poles are tilted far away from the geographic poles (by about 60 degrees!)
(Question submitted by Connor)
Oil, coal and gas are all called ‘fossil fuels’, which means they are made from the decay of ancient organisms that lived millions of years ago. The organic matter has been squashed beneath layers of rock and turned into coal reserves, with oil and gas being produced from the same process and trapped by overlying rocks.
Also, the Earth’s crust is full of metal deposits (aluminium is the most common metal in the crust), but these have also taken millions of years to form.
People are trying to explore other ways of making energy, instead of burning fossil fuels. Nuclear, wind, hydro-, solar and tidal are all alternative ways of producing electricity (called renewable energy sources, as they don’t run out).
Also, by recycling metals, instead of throwing them away, we can reduce the amount of mining new metals from the Earth.
Aquamarine is the name given to the blue type of beryl, a crystalline mineral.
Beryl is often found with granitic pegamites, igneous rocks that have large interlocking crystals within them.
Pegmatites are formed in the Earth’s crust, either surrounding large magma chambers, (molten rock) or maybe by the squeezing of metamorphic rocks (rocks that have been changed from their original state) which releases hot fluids of the right temperature and chemistry to form pegmatites.
Did you know?
The largest known crystal of any mineral in the world was a beryl crystal from Madagascar. It was 18 metres long and 3.5 metres across!
(Question submitted by Rob)
The Earth is thought to be at 4.5 billion years old. The gases that made up the atmosphere at that time would have been very different from today’s atmosphere.
Scientists have been able to guess how much carbon dioxide was in the atmosphere around 1.2 billion years ago by using evidence from fossils.
By looking at fossils found in shale (a rock made from fine clay and mud laid down in quiet deep waters) from China, geologist have fired a tiny ion beam into the centre of these fossils, which destroys the organic carbon matter and measured the type of carbon ions that are given off.
Because carbon dioxide is more likely to form with carbon-13 ions, and the fact that the fossils lived near the surface of the sea, the atmospheric content of the atmosphere could be estimated.
Carbon dioxide values of about 10 times as high as present day levels were calculated.
How do scientists measure the temperature of the moon?
On board the Lunar Reconnaissance Orbiter (LRO), there is an instrument called Diviner which measures the amount of infrared radiation coming from the Moon. The more infrared radiation that is emitted, the hotter the surface of the Moon is.
During the day, in areas of direct sunlight, the temperature can reach up to 107 degrees centigrade, hot enough to boil water.
During the night, the temperature can fall to -180 degrees centigrade!
And because the Moon takes 27 days to rotate, days and nights are 13 Earth days long!
That’s why lunar astronauts needed special suits to keep them cool in the day and warm at night.
Humus is the word used to describe stable organic matter found in soil. Humus is formed from the decomposition of organic matter (plant remains, and will not break down any further.
Humus is an important part of soil as it helps the soil keep its moisture and stores nutrients, vital to the plants and animals living within and on the soil.
(Question submitted by Anna)
The boiling point of NaCl (sodium chloride or common salt) is 1413 degrees celsius. When NaCl is dissolved in water to the point of saturation, the boiling point of saturated salt solution near to 108.7 degrees celsius.
The difference in boiling points is because when dissolved in water, the framework of sodium chloride is broken, and the Na+ and Cl- ions are surrounded by water molecules.
The heat from lava (normally between 700 and 1200 degrees celsius), will be transferred to the tree by conduction (direct contact between the tree and the hot liquid) and convection (heat transferred by motion of air around the lava).
Copper does not burn in a flame but just turns black - this blackening is the copper oxide - a result of the following chemical reaction.
2 Cu + O2 -> 2 CuO or Copper + Oxygen -> Copper Oxide
When sodium is added to water, the reaction produces heat (this is called an exothermic reaction) and melts the sodium.
The reaction can be written as:
2 Na + 2 H2O ----> 2 NaOH + H2
Sodium hydroxide and hydrogen gas is produced. The heat ignites the hydrogen which then burns with a bright flame.
The see reaction take place at: http://www2.uni-siegen.de/~pci/versuche/english/v44-1-1.html
Unlike the Nintendo’s Wii, which uses a controller to track player’s movement (see previous answer below), the Xbox 360 uses Kinect, which can track your movement across a room, without using any hand-held controllers.
It can do this by using an infrared laser which is scanned across the room (the laser measures infrared part of the spectrum of light, that is, a part of light which our eyes can’t see). The laser works out which parts of the view are far away and which are near. This is called a ‘depth field’.
Once this hardware has all the information, there is some software which takes the image and works out which part of the image is the player and which is the room. It bases this on the fact that most people are of a certain size range and have two arms and legs. All the other joints of the skeleton are guessed and filled in, so the Xbox has a complete picture of the player and their movements and position.
The average distance between the Sun and the Earth is about 92,935,700 miles.
The actual distance between the Earth and the Sun changes slightly over the course of the year. This is because orbit of the Earth around the Sun is not a perfect circle.
Astronomers refer to this distance as one astronomical unit (AU), the distance that light travels in about eight and a half minutes.
When an object feels hot, the atoms that make up the object are moving around fast. When it feels cold, the atoms are moving slower.
Some atoms are moving faster than others in the object, but their average speed always remains the same, and so temperatures is a way of describing the range of speeds of the atoms all together.
The usual way we measure temperature is using the Celsius scale, but there is another scale called the Kelvin scale, which is based on theory, rather than experiments.
On the Kelvin scale, the zero point (0K)is the same as -273.15 degrees Celsius.
As the temperature of an object drops, the speed of the atoms slows down, until at 0K (or -273.15 degrees Celsius), the atoms all stop moving.
So, it is impossible to get colder than this temperature. This is called Absolute Zero.
The coldest place in nature, is in outer space where it is 3K, just three degrees above Absolute Zero (0K), though in laboratories, scientists have cooled objects down to 1/1000th of a degree above 0K.
(Question submitted by Deepti)
To understand earthquakes, first of all, we need to talk about a theory called ‘plate tectonics’.
The earth’s most outer layer, the crust and part of the upper mantle (the next layer down) is broken into separate pieces called ‘plates’ which sit on top of the heavers and softer lower mantle (which behaves like a soft plastic, over long periods of time).
Where two plates drift towards each-other, one plate is pushed underneath the other one, and gets changed by the high temperatures and pressures as it goes down into the mantle. This is called a destructive boundary.
Where two plates are moving away from each-other, the space left is filled by erupting magma that cools and forms new crust, normally under the oceans. This is called a constructive boundary.
Where two plates move slide against each-other (in opposite directions, or in the same direction but a different speeds), this is called a conservative boundary.
In all three types of boundaries between plates, earthquakes happen. This is because stresses that build up in the moving rock at the plate boundaries are suddenly released, along lines of weakness in the rock, called ‘faults’.
This sudden burst of energy produces an earthquake and sends shock waves around the world.
However, some earthquakes happen away from plate boundaries. On ‘continental plates’, far away from oceanic plates, the stresses that build up near constructive plate boundaries can reach far into the middle of these plates and, along with other internal stresses, can cause earthquakes.
Because these ‘intra-plate’ earthquakes are rare, how they happen is still not fully understood, but it is important to understand them as they can still cause lots of damage to those who live near where they happen.
When an object is hotter than its surroundings, then a process called heat transfer happens. This is when heat (or thermal energy) flows from the hotter object to the cooler one, for example a cup of tea cooling down on a table.
Some of the heat will be lost to the table through conduction (through direct contact with eachother), while some will be lost through convection (in the steam rising up from the cup). The rest of the heat will be lost through radiation (heat transfer through empty space), or the sides of the cup being in contact with the cooler air.
Heat transfer will only happen when there is a difference in temperature. When the two objects are at the same temperature (for example the cup and the table, or the cup and the air), the transfer stops and is said to be in equilibrium (meaning in the same state). This is why a hot object in room temperature can't cool down further than the temperature of the room.
A Plasma Ball is very simply, really! It is basically made up of a glass ball, filled with an inert gas (a gas that won’t chemically react) such as neon or argon, with a smaller glass sphere in the middle that contains the electrode (the electrical conductor that connects a metallic conductor, with a nonmetallic conductor - the outside glass ball!).
When we turn it on, a voltage is induced in the electrode, which creates an electric field inside the ball. This field means that electrons can travel from the negatively charged electrode, trying to make a neutral charge elsewhere, which just happens to be at the glass ball. At the same time, another oscillating voltage is induced, which changes the electric field, and changes the electrons’ paths, making what we can see as the ‘wavey’ trail as the plasma arms.
As it is explained now, you wouldn’t actually see the trails. This is where the gas comes into play! When the voltage is great enough, the electrons break free from the electrode and begin to accelerate, always gaining energy. As the electrons pass through the gas, they give it a charge, ionizing it. The path that an electron travels, makes it easier for other to follow it, and so there is a continuous tendril from the electrode to the glass ball. While this happens, the excited atoms must lose energy, and do so by emitting a photon, which we can see as light. The color of it depends on what gas is used, normally an eerie purple color.
Lava that is still inside a volcano is called magma. Lava can reach temperatures of 1200 degrees celsius, which is too hot for scientists to use a normal thermometer (the kind you use at home or in school). Instead, scientists use an instrument called a thermocouple.
This is made of two wires of different types of metal which are joined to an electrical source (usually a battery). When the electric current passes through point where the two wires are joined, the resistance of the current can be measured. This electrical resistance is very sensitive to the temperature, and so this can be measured using an ammeter and converted to a temperature reading.
The type of thermocouple used for measuring lava can work up to temperatures of 1600 degrees celsius, as the melting point of the two wires, and the ceramic insulation and stainless steel protecting the wires are all higher than the temperature of lava.
Another way of measuring the temperature is to do it from a short distance (remotely) using an instrument called an optical pyrometer. This is a bit like a telescope with filtered lenses. A scientist will point this at the lava and adjust an electrical filament (like in an old fashioned light bulb) until the two colours match. They can then work out how hot the lava is.
You would think that as the top of the mountains are closest to sun, that it would be nice and hot up there! In fact, the Sun only radiates solar energy, not heat, which is absorbed by the land and the sea, and radiated out again as heat radiation- warming the air from the bottom, up!
You are right, hot air rises. When something is hot, it’s molecules move further away from each other, taking up more space. This means hot air is less dense and lighter than cold air, and so the cold air falls lower in the atmosphere while hot air sits on top. The higher the altitude however, the less pressure there is. This is because the air on the edge of the atmosphere, near space, has only it’s weight being acted on by gravity, pulling it towards the Earth.
The air closest to the ground, however, has the weight of all the air above it pushing down on it! The lack of pressure makes the hot air expand, which cools it. And as it is less dense, there is less air to hold the heat in, so the heat energy escapes quicker than dense air, until it cools down enough to fall. In fact as the air rises, for every 1000m, it cools by 6 Degrees Celsius.
Answered by Dr Jonathan Bridge, University of Liverpool
Hello and thank you for your question. There is a simple answer - not easily! Imagine if you were trying to find out whether it rained exactly on your house at 7 am one morning just a few days after you were born. Although your parents were there, I would be very impressed if they could recall much about the weather at that precise time. So what we have to do is find something called ‘proxy’ evidence – pieces of information which we know have some connection to the thing we are trying to find out. The Met Office has weather data from all over the UK which would say what the weather was like at the measuring station closest to your house on that day, but that’s still in a different place. You might be able to find a relative with a particularly good memory, or more likely a neighbour who kept a diary. If none of this was available, you could ask people about their memories of that year (was it particularly wet or dry?) and use what you know about the sort of weather you always get on your birthday to make an ‘educated guess’. But it would always be an estimation rather than a fact, and someone else might come to a different answer.
But why am I talking about all this when I should be answering your question? Well, because scientists really have to do exactly the same things if they want to try to understand the atmosphere of the very early Earth, without having any sort of direct information at all! 4.6 billion years ago the Earth had barely formed. We can make an educated guess that the very first atmosphere it had must have come from the cloud of gas and dust that it formed from. Astronomers can observe and measure these clouds around other young stars, so we can say that it probably consisted of hydrogen, helium and things like methane (a carbon-hydrogen gas, reference 1). However, physicists are able to calculate that much of this gas disappeared into space or was transformed by the Sun’s strong radiation rather quickly; and when the Moon was formed, probably by a massive impact from another small planet, all the atmosphere would have been lost.
So the really interesting question is what happened to the atmosphere after that – between about 4.4 billion years ago, and maybe 3 billion years ago when we first have signs of oxygen coming into the air from early life forms? Different scientists have chosen to use different proxy evidence to make their guesses about this, and have come to very different conclusions. Some (reference 2) think that the atmosphere would have been made of the gases released from rocks which no longer exist on Earth but are still found in the Solar System as asteroids and meteorites – lots of methane, ammonia (a nitrogen-hydrogen gas), hydrogen and water vapour. Others (reference 3) think that the gases released by modern volcanoes are the best proxy for the early atmosphere, and so make measurements of volcanic gases which suggest that the early atmosphere would have been mainly water vapour, carbon dioxide and nitrogen – very similar to our current atmosphere!
The debate between these scientists is very important, because the way in which life formed on Earth depends on the sort of atmosphere. A famous experiment done in the 1950s (reference 4) was the first to show that the ‘building block’ chemicals of life could be formed from non-living chemical mixtures – but only in the type of atmosphere found in the ‘meteorite gas’ model. If the ‘volcano gas’ model is true, it is much more difficult for chemists to imagine how and in what conditions life could start. This is an ongoing research problem. So although we are only able to make educated guesses about the early atmosphere, those guesses have really big implications for life on Earth. I hope this answers your question – and shows you what an important question it was to ask!
3. http://cshperspectives.cshlp.org/content/2/10/a004895.long (you may only be able to see a small part of this article)
(answered by Neil Mawkins, Liverpool John Moores University)
When two objects come into contact with each other a process known as thermal (heat) transfer will occur if there is a difference in temperature between them. This is where heat is transferred from the hotter object to the cooler by the process of conduction. This happens in the kitchen when cooking. Heat comes from the stove, to the pan, then into the food. This will also get transferred into any implements being used.
The rate this happens depends on what is called the 'thermal conductivity' of the material. This is a measure of how well a material channels heat. Metals like steel and copper have a high conductivity, while materials like wood and plastic have a low conductivity. This is why a wooden spoon won’t burn a cooks fingers where a metal one might. Plastic has a low conductivity but also has a lower melting point so might melt, and end up in your food instead!
(answered by Dr Lynda Christian, Vetinary Nurse)
Dogs eat grass, and also other vegetation, for a number of reasons.
When dogs have some stomach upsets they will often eat grass and then be sick. The sort of grass they eat at these times is very coarse, thick bladed grass and it appears to encourage vomiting as dogs are not able to easily digest this type of grass.
Dogs also eat a variety of grasses and herbs which do not make them sick. Most of the animals which wild dogs kill are herbivores (grass eaters) and the dogs eat both the stomach and its partially digested contents. Dogs can also be seen eating the droppings of herbivores such as rabbits and horses; these droppings are partially digested vegetation.
Although dogs enjoy meat very much they are scavengers and, as such, can survive on a poorer mixed diet which can include significant amounts of vegetation.
(answered by Nessa Carson, Oxford University)
What you’re talking about is an oxidation reaction. When you burn magnesium in air, two magnesium atoms from the metal will combine with each oxygen molecule they come across, which is why we write the equation
2 Mg(s) + O2(g) --> 2 MgO(s)
(if you haven’t seen the subscript symbols in brackets before, they just tell you about the physical state of the substance – (g) means gas, and (s) means solid). Magnesium’s two outer electrons are not held very strongly to the nucleus, so it gives them up to oxygen and forms a white solid made up of Mg2+ and O2- ions in a regular pattern to minimize the energy needed to hold them together with ionic bonds.
But unless you’ve spent a lot of time thinking about what symbols and equations actually mean, this doesn’t really make you understand what’s going on. Magnesium is a very reactive metal and does actually react with the oxygen in air slowly at room temperature, which is why magnesium ribbon needs to be cleaned with sandpaper before you stick it in a Bunsen flame – you need to remove the unreactive magnesium oxide coating that’s already formed after storage in air. The metal is so reactive that when burned, it can pull the oxygens off a carbon dioxide molecule to produce MgO and carbon, or even react with the normally ‘inert’ gas nitrogen to form Mg3N2!
However, if you add a source of energy to the reaction in the form of the high temperature of a flame, it all happens very quickly and you get the blinding white sparks that probably prompted you to ask this question (incidentally when I say blinding I mean it – you can seriously damage your eyes if you stare too hard at the flame for a long time).
So okay, we’ve seen how the actual atoms respond to each other, but why is the flame white, when metals like manganese, copper and sodium display coloured flames? Flame colours happen when electrons in the substance being heated are given extra energy. The change in energy is specific to the type of atom, and requires a photon (particle of light) with a frequency directly proportional to the energy change.
For manganese, copper, sodium and many other metals, this photon frequency is in the range that’s visible to humans, and a colour is produced, which is just what white looks like if you subtract this particular frequency (a visible photon’s frequency is a colour). For magnesium, the frequency is larger, and ultraviolet light instead of visible is subtracted, so the flame appears white. The way most people get to see this is in sparklers and other fireworks on Bonfire Night!
Lightning is thought to form from ice and water droplets colliding in a thundercloud. A large electrical spark forms from electrons moving from between the ice and water droplets. Electrons cannot be seen but when lightning flashes they are moving so fast that the air around them glows. The actual streak of lightning is the path the electrons follow when they move.
Thunder is formed by the heat from lightning compressing the air around in and forming a supersonic wave that decays into a sound wave that you hear as thunder. You always see the lightning first as light travels faster than sound does.
How to stay safe in a thunderstorm
If there's a thunderstorm, make sure you stay indoors and don't use any electrical equipment like the television, computer or telephone. If the lightning strikes the house, it will take the easiest route to earth, e.g. electrical cables or water pipes.
If you can't get indoors, avoid any high places, or tall isolated structures (towers, trees, etc.).
Did you know?
In June 2009, a teenage girl survived a direct hit by a lightning bolt thanks to wearing her iPod. The girl and her boyfriend were under a tree sheltering from the thunderstorm when the lightning struck.
The lightning passed through her headphones (not in her ears at the time!) and down into her mp3 player.
Experts think that lightning takes the easiest route to the ground and the metal contained in her mp3 player was the best conductor of electricity.
The controller (or Wii-mote) is stuffed full of tiny motion sensors called accelerometers. These measure the acceleration (how much things speed up) of the controller in 3 directions (up / down, left / right and forwards / backwards). A microprocessor in the controller works out the movement of the player as well as the speed of the movement and then beams the signal across to the console using infra-red (a part of light that humans can’t see).
People are now using accelerometers to control loads of other things like vacuum cleaners, mobile phones and even to make 3D pictures on your computer screen!
Did you know?
Playing a Wii sports game where you move around burns 60 calories an hour more than when you play a game sitting on the sofa!
(Question submitted by Jacqui)
The Earth is like a big bar magnet with a North and a South Pole. These are near to the real poles but not exactly in the same place. There isn’t a real bar magnet in the Earth though. Liquid metal in the centre of the Earth’s core (liquid because it’s so hot down there) moves around as the Earth rotates and generates electricity and magnetism just like an electric generator does.
The tip of a compass needle is magnetised so it is attracted to the magnetic North pole of the Earth. The magnetic field of the Earth is quite weak at the surface, so any strong magnetic near the compass will change its direction.
Did you know?
The North and South magnetic poles sometimes change places! The last time this happened was 780,000 thousand years ago.