Answers to last issue's Do You Know?

1. What is vertigo? 
Ans: Vertigo is this sensation of dizziness or spinning and most people will have experienced it -- if not at any other time when, as a small child, you spun round and round looking at the sky until you fell . But some people get it quite regularly and it's all to do with your inner ear. Inside your ear, you have three semi-circular canals, little sort of loops which are filled with fluid and they're all at 90 degrees to each other. That's how you know which way up your head is and which way it's moving because the fluid inside them moves, knocks into these little sensor hairs and that tells you how you're moving.
When you spin around, the fluid in them starts to spin as well, but after you stop, it keeps spinning for a while and that's what makes you feel dizzy after you have been spinning around. But lots of things can make you feel like you are moving even when you are not, which is what is happening in vertigo. There are some circumstances when it can be caused by little pieces of dirt that have found their way into the inner ear and they confuse the signals that are being sent to the brain. That type of vertigo tends to happen only when your head is in a certain angle so the dirt is hitting the little cells.
It can also be linked with migraines. In which case, the problem is probably actually not in your ear, but in the nerves or in the brain itself. But scientists still don't really understand migraines. They are a bit of a mystery to us. 
Now, we may wonder why the body has evolved to make the decision that when you get motion sickness or vertigo to throw up (vomit). 
Well, vomiting is a sensible response if you have eaten something bad and it seems that dizziness can sometimes be an indicator of poison. It is very likely that this is how this trait evolved, that in some circumstances it was very useful to throw up because you had eaten something bad. And actually, if you throw up a few more times than you need to, that's better than not throwing up when you should.

2. Can magnets on pipes soften water? 
Ans: This question comes up presumably because there is such a belief in many parts of the world. There are even commercial advertisements that refer to this belief. All this led some citizen science groups to investigate the claim that attaching magnets to pipes causes water to be soft, that scaling is avoided. The investigators concluded that there was no basis to the claim at all.
We can consider what the magnets could be doing. We have to think about what hard water is. It is mainly calcium and other minerals dissolved. There is a tiny amount of iron in there that could be affected by the magnets. But even this iron is it in a form which is actually magnetic. Most of it is in unmagnetic form, in one of the electronic configurations that are not magnetically active. 
So why is the belief so prevalent? It is very likely a `placebo' effect. After having spent the money to buy a gadget and put on the pipes, people expect to see a difference and hardly cut the pipes to see if scales have formed, so they think the water tastes `good'. 

3. Can we achieve artificial photosynthesis? 
Ans: Yes, artificial photosynthesis does indeed exist. Photosynthesis is essentially the means by which energy from the Sun is captured and used to split water molecules to generate fuel for the plant to use in growth. What scientists are trying to do is to use the principles from natural photosynthesis to harvest the Sun's energy and convert it into fuel. The main challenge being met in the field is in the splitting of water. 
If we split water we produce hydrogen, and hydrogen is a much cleaner fuel than the fuels we are currently using, and this fuel can be used, for example, using fuel cells to power cars. 
The challenges scientists are facing at the moment are coming not just from the light harvesting side where we have the same challenges as in solar cells, but also from the catalyst side because the catalysts have to be very efficient and very robust. The catalysts are essential because they speed up the reaction, and in general increase the efficiency of the device. At the moment, platinum catalysts fulfil these criteria. However, they are very expensive, so scientists are working on cost effective catalysts such as copper based and nickel based ones.

4. Why do migratory birds fly in a V-formation? 
Ans: The linear flight formations of migratory birds are called echelons. The V and the J formations are typical and are the most readily recognized flock echelons, but other variations also occur. Studies of several species have shown that a true V-shaped echelon is, in fact, less common than a J formation is.
There are two well-supported and complementary explanations for why birds fly in formation. One is to conserve energy by taking advantage of the `upwash vortex fields' created by the wings of the birds in front. The other is to facilitate orientation and communication among the birds. These explanations are not mutually exclusive, and both have been backed by a variety of studies. The relative importance of each undoubtedly shifts as various factors, such as the season of the year or the purpose of individual flights, change. During local feeding flights, for example, energy conservation is probably much less important than careful orientation and collision avoidance are. 
During long-distance migration, orientation and communication remain necessary, but there is also much to be gained for each bird in the flock by optimizing its position to conserve energy.
Fluid dynamics and energy wave configuration calculations have been used to test predictions of where birds should position themselves in relation to others to conserve the most energy as they travel through the air. Analyses of flock formations using photography have measured bird positions and found them to almost always be located such that they gain some energetic advantage. The animals are not very often in the expected optimal location, however, indicating that other factors also influence position in the formation. 
Knowledge of birds' visual axes, "blind spots" and field of vision have allowed researchers to pinpoint the best locations for birds within a flock to maintain optimal visual positioning. Actual positions of the animals are usually similar to these predictions but are, again, not always optimal. Studies have categorized the positions of birds and found that some individuals take positions that are most closely predicted to satisfy the energy conservation hypothesis; others are in better visual contact positions; and still others are not apparently responding to either benefit or are in a position that should gain some advantage from both benefits.
The leaders of formations change from time to time, but the causes, frequency and characteristics of these changes have not yet been determined. Sustained observation from the ground of flocks covering great distances in the air is very difficult. There are plenty of intuitive predictions about leader choice that quickly come to mind relative to the age, experience, sex, condition and social status of the leaders, but researchers have not figured out how to overcome the prohibitive logistic issues to test them. Some scientists have trained birds to fly in formation with small aircraft; perhaps their experiences will yield opportunities to test these ideas. 

5. Would music sound different on Mars?
Ans: In fact, another similar question often comes up too. Is it true that on Mars, no one can hear you scream? First up, we can do some calculations. In general, the speed of sound is proportional to the square root of the substance's stiffness divided by its density. Since Mars's atmosphere has a lower density than here on Earth, you'd expect the speed of sound to be faster than here on Earth. But if you reduce the pressure of a gas, the stiffness also reduces. So, the speed of sound should stay about the same on Mars as it is on Earth. But there's another factor to consider. Mars is further away from the Sun. How does this affect the speed of sound?
The difference is temperature. If you reduce the temperature of the atmosphere, the speed of sound does get slower. In fact, the speed of sound on Mars is about 2/3 of the speed of sound on Earth.
So, say two humans were to land on Mars, given the slightly lower speed of sound there, could they still speak to each other?
The speed of sound on Mars is around 240 meters a second, a bit lower than the 340 meters a second on Earth. By itself, that would not make sound communication harder. However, the atmospheric density of Mars is less than 1% of Earth, almost a vacuum by our standards. This means that sound attenuation is much greater and so, speech would not carry very far. Human mouths and ears would not be able to couple sound efficiently into or out of the thin Martian atmosphere, so humans would be effectively deaf.
The atmosphere's lower density is not suited to human speech and hearing systems which have evolved for life on Earth. Instead, radio waves, a form of light travels fine through low densities and so, can be used as a method of communication up there which is how exploratory rovers on Mars like Curiosity communicate, not with each other but with us on Earth using radio wave messages traveling at the speed of light and taking about 15 minutes to be received here on Earth.

6. What is the lifetime of a comet?
Ans: Comets are actually large clumps of ice and rock that were left over when the planets were formed. We can think of them as huge dirty snowballs orbiting the Sun. Being snowballs, this means that they can melt and they also actually do melt.
Every time a comet passes close to the Sun, a part of it sublimates, meaning that the snow and ice turn directly into vapour and this is the vapour that we can see as one of the tails of the comet. So, since part of the comet sublimates every time it passes the Sun, it cannot live forever.
Recently the ISON comet came very close to the Sun, reached perihelion on 28th November 2013 (closest point of approach to the Sun) and completely disintegrated within the next few days. On the other hand, we have, for example, Haley's comet, which is quite well-known since it passes the Sun once every 75 years or so, and this comet will be completely sublimated and disappear after only 10,000 years or about 100 rotations around the Sun.
This is a typical lifetime for a comet. But still, this does actually not mean that there will come a day when all the comets are gone and that is because there are huge hidden supplies of comets waiting beyond the orbit of Neptune. That is the Kuiper belt and the Oort cloud. These regions continuously replenish the inner Solar System with new comets.

Source: The Naked Scientist