Answers to March-April issue's Do You Know?

1. Can we use lightning and thunderstorms as sources of energy?
Answer: This is perhaps something human beings have fantasised about for hundreds of years. Surely, lightning and thunderstorms carry a great amount of energy, can we not somehow make use of them for our energy needs?
In fact, a great deal of electrical energy is unleashed during a thunderstorm. On average, a lightning bolt is said to contain about five billion joules! The trouble is that capturing that energy is very difficult.
To start with, we have no idea where lightning is likely to strike. With all the science and computing capability we have now, we still cannot predict it. At any given time, there are around a hundred lightning occurrences around the globe, but these flashes are unpredictable. Only a very small fraction of them reach the ground.
Suppose that we have managed to "catch" it. The next problem is to convert all that energy into some useful form. The heat generated by lightning can be over 20,000 degrees Celsius, and the voltage can be as high as around a hundred million volts. We do not have equipment that can safely withstand these extreme conditions. If we manage to build such material, the next issue is storage. We need to convert the energy into the low voltage, alternating current that powers our homes. This is very difficult.
The last big problem is dissipation into the atmosphere as heat. We would get at most 1500 kilowatthours after all the effort.
A company in the USA called Alternate Energy Holdings did try to develop technology to harness energy from lightning in the early years of this century, but gave up. Perhaps you will make the great breakthrough some day that will address this challenge!

2. I saw the film Meg. Are megalodon sharks real? How big are their teeth?
Answer: Megalodon shark is a real animal, one that can make white sharks look 'normal'! Not only are they the largest sharks to have ever lived, but also one of the most dominant creatures to roam the oceans. Their predatory behaviour has shaped entire marine ecosystems.
If you are terribly scared, please do not be. You are unlikely to meet any megalodon shark, because they are extinct! We know of them only though tooth fossils.
What size was a megalodon shark? Big. Very big. The megalodon shark was roughly 16 metres in length. That is longer than a normal sized bus, and three times the length of the average great white shark. Scientists also estimate that their fins were the length of an average adult human.
We do not have fossil evidence to tell us how their bodies were built. Scientists have used mathematical models to make estimates. They have calculated that a megalodon head might have been around 4.65 metres long, its dorsal fin approximately 1.62 metres tall and its tail around 3.85 metres high. They suggest that at birth a baby megalodon was two metres in length, much bigger than an adult human! 
How big were megalodon teeth? By the way, the word ‘megalodon’ actually means ‘giant tooth’ in ancient Greek, so it is no surprise that their teeth were big. Each shark had 276 teeth, each measuring up to 18 cm long. Unlike other parts of the megalodon skeleton, which was made from cartilage, each tooth was formed by hard dentin (like human teeth). From fossils, we gather that the jaw was around 3 by 3.5 metres wide. That is big enough to fit at least two adult movie stars inside, so imagine it for your favourite film.
Here is something very interesting. Megalodons would lose a complete set of teeth between every one and two weeks, and grow them. This means they would produce up to 40,000 teeth during their lifetime! That is why these fossils are so common to find.
It is estimated that megalodon bites could exert a force of up to 182,200 Newtons, giving them the hardest bite of any ever creature known on Earth. In comparison, the Tyrannosaurus rex could bite with a force "only" of 60,000 Newtons, while the Nile alligator (who has the strongest bite of any living animal on Earth today) can manage "merely" 22,000 Newtons.
Megalodons became extinct about 3.6 million years ago. The earliest Homo sapiens species emerged roughly 2.5 million years ago, so they were before "our time". Megalodons seem to have lived even 20 million years ago. 
How did such an awesome animal go extinct? We do not really know. Some scientists say they were killed by a period of global cooling. Others say they died out due to a lack of suitable prey, alongside the appearance of predators like the great white shark, which depleted the megalodon's food source.

3. How small would the Earth have to be for us to feel it spinning?
Answer: We do not feel the rotation of the Earth, because we are rotating with it. But it is also because we are very small relative to the size of the Earth.
Now suppose that the Earth is somehow compressed without losing any mass. Then it would have to spin faster to conserve its angular momentum. Have you seen dancers do this on one leg, folding themselves and spinning faster? This would increase the centrifugal force acting on us. Since this force acts radially outwards, it could partly cancel out the force of gravity, and our weight would decrease.
How much should we compress the Earth for this to happen? Halving the diameter of the Earth would reduce our weight by around 1.2kg, which is probably not enough to even notice. But centrifugal force does not increase linearly, and on a quarter-sized Earth our weight would drop by 15kg in total, so you would feel lighter and could jump higher.
Whether this counts as "feeling the rotation" itself is debatable. On a merry-go-round, you feel the spinning because the radius of the ride is so small that the centrifugal force varies noticeably across the length of your body. For this to happen, our miniature Earth would have to be so small that your own height was a significant proportion of the planet's radius. Long before we reached that point, though, the Earth would have disintegrated from its own centrifugal force.
In short, if it were so small that you would feel it, you would not be around to feel it!

4. How far away is the Orion Nebula? Why is it so clearly visible?
Answer: When stars are being born, or when they are dying, they form nebulae, clouds of dust and gas. Some nebulae are where stars have died, and some where stars are forming. The Orion Nebula is the latter.
At "only" 1,344 light-years away, the Orion Nebula is the closest and one of the brightest nebulae visible from Earth. This means that it can be seen with the naked eye at some times of the year when viewed under dark skies.
The brightness of objects in the night sky as seen from the Earth is measured on a logarithmic scale: the lower the number, the brighter the object. This scale means that an object with magnitude 1 will be 10 times brighter than a magnitude 2 object. The Sun has a magnitude of approximately -26, while the brightest star in the night sky, Sirius, has a magnitude of -1.46. The Orion Nebula has a magnitude of 4, which means it is fairly faint. You will need to go somewhere dark and let your eyes adjust to really see it. A new moon night is good for this.
Finding the Orion Nebula is easy as it is in the constellation Orion, one of the most easily recognisable constellations. Orion is most visible in the evening sky from January to March, winter in the Northern Hemisphere, and summer in the Southern Hemisphere. In February and early March, Orion will be visible in the eastern sky as soon as the Sun sets, sweeping south in the northern hemisphere then setting in the west in the early hours of the morning. In the southern hemisphere, Orion will be visible in the north, appearing upside-down compared to how it looks in the northern hemisphere. To find the nebula, look below the three stars of Orion's Belt. You will see a faint line of stars, which make up Orion's sword. The nebula is halfway down the sword and appears as a fuzzy-looking star.

5. Could robots be programmed to evolve?
Answer: The answer is yes, and this was demonstrated by scientists in 2015. If ever humans want to settle on other planets, we would want to send an advance party of robots. They would first create conditions favourable for humankind. But then, if they need to survive within the inhospitable cosmic climates that await them, they would need to be tough, adaptable and recyclable. Thinking along these lines, scientists concluded that that the best way to make them tough and adaptive would be to get them to evolve.
Out in the cosmos, what shape and size should the ideal robot be? Should it crawl or walk? What tools will it need to manipulate its environment? How will it survive extremes of pressure, temperature and chemical corrosion? These are difficult for us to answer but nature has already solved this problem. Darwinian evolution has resulted in millions of species that are perfectly adapted to their environment. 
The problem is that biological evolution takes millions of years, and we cannot wait that long. But artificial evolution, modelling evolutionary processes inside a computer can take place in hours, or even minutes. Now computer scientists have graduated from modelling to physical robots that reproduce their hardware (using 3-D printing) in an evolutionary manner. This process is slow, but much faster than biological evolution already, and will get faster as we learn the processes better.
The "mother" is a robotic arm that builds "baby" robots out of small cubes. Each cube has a mechanism where one side can waggle. When you place it on a surface, it clumsily drags itself around. The mother glues these moveable cubes together in various arrangements. Some combinations move further and faster than others. The mother robot builds each arrangements using assembly instructions in the form of a "genome" that is passed between successive generations of robots.
These algorithms evolve both the body-plan and brain of the robot. The brain contains a controller that determines how the robot moves, interpreting sensory information from the environment and translating this into motor controls. Once the robot is built, a learning algorithm quickly refines the child brain to account for any potential mismatch between its new body and its inherited brain.
The mother is programmed to insert random mutations into each generation. Some offspring move around better than their forerunners, but others do worse. The mother rejects deficient generations but uses the genetic blueprints of successful ones to build subsequent offspring. In the lab, after only 10 generations, the robots performed twice as well as those at the start of the process.
Shall we call this "unnatural selection"!?
From various sources