Answers to last issue's Do You Know?

1. We hear of global warming and ice melt in the Arctic. When will all the ice in the Arctic be fully gone?
ANSWER: This is a question that many are asking. As we hear more about global warming, and read of icemelt in the Arctic, there is natural concern among the general public as well as people in Governments. As ice keeps melting in the Arctic, when will it all be gone? 
As we will see, this is actually not the right question to ask, as this assumes that sea-ice loss is irreversible. Ice keeps re-forming, so we need not consider that it will be "gone". The right question to ask is: how much more sea ice we are willing to lose?
What is usually call ice loss in the Arctic is loss of *summer ice*, measured in September. We monitor summer ice in September because that is the time of year with the least amount of sea ice in the Arctic Ocean. Historically, the Arctic Ocean was covered by ice year-round, but today this area is about half of what it used to be.
So we should ask: when are we likely to see ice-free Septembers in the Arctic? The most recent IPCC report (Intergovernmental Panel on Climate Change) gives what is likely to be a conservative estimate: it states that if global temperatures increase by two degrees C, ice-free Septembers will at happen once every decade. Several scientists point out that the observed relationship between sea-ice decline and global warming is much larger than that seen in the climate models (including those used by IPCC). Compensating for this, they assert with certainty that ice-free conditions will occur *every* summer at a global warming of 2 degrees C.
The probability of ice-free summers is greatly reduced if the warming is kept to below 1.5 degrees Celsius. But this seems unlikely as of now.
To understand more, we need to see that ice loss is a function of natural climate variability and warming caused by increased atmospheric carbon dioxide (CO2) concentrations due to human activity. Every metric ton of CO2 added to the atmosphere causes another three square meters of September sea ice to disappear. Currently we add 35 to 40 billion metric tons of CO2 each year.  When we will have added another 800 billion metric tons, September sea-ice will disappear in the Arctic. Will this be in 20 years, or less? Remember that these are statements based on models, and there is a variety of climate models. The predictions vary widely, from 2 years to 20 years.
What is worse is that it does not stop there. With another 1,800 billion metric tons of CO2 added, the Arctic will likely have no ice from July through October.
So what we need to do is to discuss ways in which we can limit the amount of additional CO2 in the atmosphere in order to preserve summer ice cover in the Arctic.

2. Why do we forget so many things but never forget how to ride a bicycle?
ANSWER: Many adults tell you this: they used to ride a bicycle during childhood; never even touched a bicycle for a decade after they started working; but then suddenly, when they had an opportunity to ride a bike, all they had to do was hop on, it came to them naturally!
When the same person is unable to recall where s/he kept the bicycle key afterwards! Or s/he tells you, there used to be a restaurant at that corner until last year, what was its name? How is it that we do not forget the skill to ride a bicycle but forget so much else?
The short answer is that  different types of memories are stored in distinct regions of our brains. The kind of memory relating to biking, called procedural memory, resides in basal ganglia,  below the cerebral cortex, relatively better protected in the brain's centre. In this region, fewer new nerve cells may be formed in adults and hence there is less re-forming. Therefore, unlike in other areas where there is neurogenesis, or continuous remodelling, fewer memories get erased as well.
Long term memory is of two kinds: procedural memory and declarative memory. While the former relates to performance (like singing, playing an instrument or riding a bicycle), the latter is related to knowledge.  Declarative memory may be factual knowledge (What is the capital of Uttarakhand?) or consist of recollections (What did you do on your 10th birthday?). For both of these you are aware that you know (or not) and can communicate this to others. Declarative knowledge involves interpretation and the brain does a great deal of "modelling" (to decide what to remember) in memory of facts and recollections. This is the neurogenesis we referred to.
How do scientists know this? In a famous study of an epilectic patient called Henry Gustav Molaison, they found some of this. Large parts of his hippocampus (in his brain) had been removed during a surgery. The operation was successful and the number of his epilectic seizures ("fits") reduced, but Molaison had also lost many memories from before the surgery, and could not form new memories. As his hand-eye coordination improved, doctors could make him learn -- for instance, to draw and reproduce an image. But he could never remember drawing the image. Basically they saw that he could develop procedural but not declarative memories.
By now neuroscientists know that procedural memory is more resistant to loss and trauma (due to major injuries). So it does seem that memories of sequences of actions, responsible for performing actions, are more stable than that of recollections.

3. Can one lose weight only by exercising, or is dieting also needed?
ANSWER: Many advertisements by soft-drink manufacturers seem to suggest that you need not worry so much about calories and dieting as about exercising.  Of course, this is good for them since those drinks add many calories. But is this true at all?
According to many diet and behaviour experts, any such claim is false.  They say that working out is not, by itself, very effective for weight loss. There is no data saying that if you exercise so many hours a week at some particular level of intensity you lose so many grams, independent of what you eat. On the contrary all data seem to refute this. 
Regular exercising is important, since it keeps people focused on their health and it keeps them psychologically stable as well. However, exercise increases appetite and people often just make up for whatever they burnt off by exercising.
On the other hand, people who diet tend to restrict themselves overly, which often leads to overeating when they do eat. Often cutting out some kind of food makes that food more desirable. To lose weight, you have to change your behaviour for the rest of your life, so the change should be sustainable.
Doctors say weight loss is like training to run marathons, not training to run a sprint race. It is about making regular, sustainable diet changes.  You should not change your eating pattern drastically, but make small changes that are easy to sustain and work up to dropping about 300 calories per day.
Fundamentally exercising is good in multiple ways and it is also helps to burn off calories. But it cannot make up for diet control.
4. Who invented soap?
ANSWER: The timeline in the Box shows how the making and use of soap goes back at least 5000 years ago to the Sumer region, now in Iraq.
Soap originally seems to have been used primarily for the treatment of ailments.  One Sumerian text dating back to 2200 BC describes a form of soap being used to wash a person with some type of skin condition. Exactly what the physicians believed this would do is unclear, but the idea that soap had medical benefits was accepted by many ancient civilisations.
The primary cleaning agent in ancient India was taken from soap nuts also known as soap berries (from the plant Sapindus saponaria). The literal translation of Sapindus is sap = soap and indus = India. In other words, soap from India!
This nut was used in ancient China as well and its usage spread from India to Middle Asia and then Europe. Soap nuts are boiled to soften them up, and then crushed to filter out the essence which contains the all-important cleansing chemicals. It lathers but in small quantities. Ancient India also used shikai or shikakai (a variant of the acacia plant) as a hair and body cleanser.
As early as 3000 years ago during the Zhou Dynasty, the Chinese discovered that using ashes of certain plants could be used to remove grease. This method was improved upon in subsequent dynasties using and mixing these ashes with crushed sea shells, as well as discovering a naturally-occurring form of saponin which was a useful and effective cleaning agent.
When mixed with water, certain tadpole-like molecules in soap form spherical structures called "micelles" around any droplets of germy dirt or oil, with their water-hating ("hydrophobic") tails pointed inwards and their water-loving ("hydrophilic") heads pointed outwards. The outside of the micelle is soluble and so it washes away, along with any grime trapped in the middle.
BOX
3000 BC Sumerians use soap solutions made from ashes and water.
2800 BC The Babylonians record the basic method of making soap.
1500 BC The Ebers papyrus shows that Egyptians produced a soap-like substance.
1200 to 200 BC The Greeks and Romans use public baths but do not use soap.
79 AD An entire soap factory of this period found among the ruins of Pompeii.
200 AD Roman baths use soap regularly.
700 AD Arabs produce the first solid soaps.
800 AD Soap making processes in Italy and Spain.
1200 AD Fragrances in soap; Italy and France lead in soap making.
1500 AD European processes use vegetable oil rather than animal fats.
1791 First commercial soap making  by Nicholas Leblanc and Michael Chevreul.
1811 Chevreul discovers the chemistry of soap.

5. How do ants breathe?
ANSWER: For human beings, the diaphragm plays a major role in breathing. It actively pumps air in and out of our lungs. Try this: open your mouth and throat, but hold your diaphragm and chest absolutely still. Actually, even now, though you think you are holding your breath, some oxygen does manage to find its way into your lungs by the random diffusion of air molecules. But that is not enough to keep up with what your body needs and you gasp. 
If you didn't have a diaphragm, you would need a much smaller body, or more than one throat. Ants have both.
Some species of ants have nine or ten pairs of openings, called spiracles, along the side of their body. Each spiracle is connected to a very finely branching series of tubes called tracheae. This seems similar to our lungs, but insects do not use blood to carry oxygen from the tracheae to the rest of the body.  Instead, the tracheae spread throughout the body and each branch ends in a little bag with a moist end-wall that touches directly against the membrane of a cell.
An ant's movement helps the oxygen to circulate through the trachea, with the released carbon dioxide exiting through them as well.
This system works well only in tiny animals. Once the body grows beyond a centimetre or two, the tracheae are simply too long for air to be able to diffuse along them fast enough. What do the larger insects do then? They supplement the passive breathing system by flexing their abdomens to pump air along the tracheae.
For ant-sized insects, though, the trachea work just fine. In fact, scientists have found that  many insects this size actually have to close their spiracles periodically to avoid getting too much oxygen!
An extra fact about ants: they are as old as the dinosaurs! Scientists have found that ants first rose during the Cretaceous period around 130 million years ago. They have survived the Cretaceous-Tertiary (K/T) extinction that killed the dinosaurs as well as the ice age.
Sources: Scientific American,