Answers to last issue's Do You Know?

1. Do yoga and meditation actually cause internal changes in the brain?
Ans: In general, it is known that if we do something repeatedly, we build up ichanges in the brain. Using EEG (electro-encephalograph) studies researchers have linked meditation wth lower frequency waves. This suggests that when you are in a meditative state you are more relaxed.  Actually when scientists looked at the waves more carefully they also noticed that the waves linked with attention and awareness as well.  Some very limited studies have seen changes in the structure of brains of people who meditate regularly, in comparison with those who do not.
But one has to be careful here. These studies are very limited as yet, and we need many more studies before systematic answers can be provided.  Many neuroscientists have noted that meditation can improve medical conditions such as depression and anxiety, but this again has not been analysed carefully yet.
More generally, there are regions in the brain that are consistently altered and they are regions that are involved in things like memories, being aware of one's own body, as well as attention regulation and tuning out distractions. As it happens, these are things you do when you are meditating as well. And we know that the more you practice something, whether it is a musical instrument or a sport, the better you get at it.  Thus meditation may be practice in activity that consistently alters these regions.
The way memory works, the more times you recall a memory the stronger the trace of that memory is in your brain and the more likely you are to remember it in the future, this might be similar. 

2. If a human could be fed with energy via USB ports rather than food, how long would it take to fully charge an average human being with, say, 1000 or 2000 calories of energy?
Ans: Those 2000 Calories are very big calories because an average person uses between 2000 and 2500 Calories a day. So this is quite an interesting question indeed. With a USB typically you can draw up to 3 amps. Given that it is at 5 volts, that means that the rate of energy delivery from a USB is a maximum of 15 watts – in other words, 15 Joules per second.
Now, one big Calorie -- like it is in food -- that is equivalent to 4200 joules. If you want someone to consume 2000 big Calories in a day, which is your average, that is 2000 times 4200 joules, about 8 million joules.
To work out how long it will take in seconds to get that much energy into someone with a USB port then you have to divide 8 million by 4200. That comes to about 53000. In other words, it takes you 6 days to get one day's worth of energy, equivalent to one day's food ration, into you. Probably this is not going to be a very sustainable means of nutrition unless we can up the wattage. A person runs at about 2 watts per kilo. So, on average, a 50 or 60-kilo person is running at about 100 watts. Therefore, we have got to find a way of delivering energy at that sort of rate. 
I think it is best stick to food. Food is nicer.
Of course we could use several USB plugs per person ....

3. Do other mammals have blood types like human beings do ?
Ans: The very quick answer is yes. But the explanation is interesting as well.
Blood groups are due to the molecules that are on the surface of your red blood cells.  In humans, you have probably heard of the blood groups A, B, AB and O.  Other animals do not exactly have the same molecules as us because these molecules enable us to recognise what is our selves versus what is foreign. Other animals need this ability too, because it is part of the immune system to check out whether a tissue belonging to me or not. So they have a similar system as well.
Apes being very closely related to humans, they have very similar blood markers. There are other types of markers in other species. For example, dogs have about 13 different blood groups because they have a whole bunch of different molecules that are found on the surface of their blood cells. Cats have only about three. So yes, other animals do have blood groups, not the same as ours, but fulfilling a similar function.
As for injecting blood from other animals into humans, do not even think about it. The human immune system is very efficient at getting rid of foreign substances, and this can cause a big problem  if the quantity of those foreign substances is too high, even leading to death.

4. In the deep oceans where the pressure may be very high, why are the creatures which have evolved there not simply crushed by the force?
Ans: Firstly, let us understand that we ourselves are designed to withstand pressure. We have pressure pressing down us all the time from the air above us. 
Have you ever seen someone suck the air out of the inside of a can and it immediately crumples ? This is because the air pressure is strong enough to actually crush that can. The only reason it does not crush it most of the time is because there is air inside it as well.
Our bodies work the same way. There is air inside us and there is air around us and this (more or less) balances out. When you go down into the deep sea, there is a huge amount more pressure.  In fact, the pressure increases by about 1 atmosphere for every 10 metres as you go down in the sea. 
This means that deep sea creatures have over a thousand times the pressure on them than we do. But they have evolved to live in that pressure.  They do not have air pockets inside them like we do. Their muscles have lots of water in them and water is not compressible, this stops them from being squeezed too much.
Deep sea creatures have many different changes to their physiology.  Some of them have a molecule called a PISA light which actually prevents other molecules from being distorted when they are under pressure. As yet we do not really understand how this works because one of the big challenges in studying these animals is that we cannot go down (we could not survive down there), and they cannot come up (they cannot survive up here). By the time one of those fish is brought up, it would look very different from how it looked down below.
What about whales then ?  They travel between lots of different pressures which is very hard.  They have lots of different adaptations that help them. For instance their lungs effectively collapse so that when they are diving down, those air-filled pockets basically just disappear !  They can deal with that physiologically in a way that we couldn't if our lungs collapsed, that would be really bad news for us. Whales also do not have some of the other air-filled cavities we have like sinuses.
Whales have very interesting behaviours. Remember that down below, they compress all this gas in their lungs down to a miniscule volume, and effectively make it dissolve in their blood (which is what happens when you put it under that pressure). Now if they were to surface very fast, they would get fully bent. But they do not; they come up slowly, so there is an opportunity for the gas to come back out of solution in the blood and go into the lung tissue. It does this at a slow enough rate that you do not get bubbles forming in the bloodstream. 
If you scare a whale, which can happen with underwater detonations and seismic surveys for oil etc, that can make them rush to the surface and then they do get the bends, and people have found whale carcases where they have looked at the bones of these whales. Some of them are more than 100 years old and you can see what are called osteonecrotic lesions. This is where a bubble has formed in the blood vessel that supplies that patch of bone and the bubble has lodged in the blood vessel. This blocks the supply and therefore devitalises the bone downstream, the whale dies and you get a hole in the bone. This is a sign that whales can probably get decompressed, in response to being frightened and surfacing fast.

5. How do amateur astronomers discover comets?
Ans: Rather than answer this in general, let me tell you about one amateur astronomer who has become famous recently with his find, Comet C/2014 Q2 (Lovejoy). He is Terry Lovejoy, an Australian IT specialist and amateur astronomer with five comet discoveries to his credit. 
Lovejoy found his first comet in 2007. His third discovery, made in 2011, was distinctive because it was what is known as a Kreutz sungrazer, a comet that literally grazes the atmosphere of the sun. That object, called Comet C/2011 W3, flew through the sun’s corona, passing within 140,000 kilometres of the solar surface, and emerged damaged but still intact.
The magazine Scientific American published a very interesting interview with Lovejoy, where he described how he ``hunts'' comets.
Most comets are discovered by the professional surveys. Amateurs tend to find stuff in areas near the sun where the surveys do not look.  How do they do it?  The computer and the telescope do most of the work.  Lovejoy has a shed just on the side of his house; it has a roll-off roof that he can just push off, connect the telescope to the computer and run an automated sequence to image parts of the sky.
It takes three images of the same part of the sky, but they are separated by about 10 minutes. If there is a comet or any moving object you would see it move between those exposures. He has software that basically trawls through those images and looks for objects that are moving. Then he verifies by eye whether what the computer found is real or not.
How often does the software flag photos that need to be checked by eye?  Lovejoy says that during any one night's session, a 100 or so may get flagged. But these are little preview windows and he can flip through them very quickly. Some of them are real objects, like asteroids and other comets, so these need to be eliminated. For this Lovejoy uses reputed Web sites on the Internet, where you can put in a position and look for known objects in that area.
Thus the software finds 100 possible objects every night but it takes a year or two before one turns out to be a real new comet. As you see, this takes great patience.
For the last two comets Lovejoy went though about 70,000 images to find each comet. He says that it is the challenge of working on the telescope, working on the software to get it more efficient that gives him satisfaction.  

Sources:
Science Forum, Cambridge University
Scientific American
Physics World