Saturday, August 30, 2008
A recent study in the August 27 issue of the Journal of the American Medical Association points out that around twenty per cent of ayurvedic products purchased through the internet have significant levels of arsenic, lead and mercury. About 60 percent of the samples were from U.S. companies and 40 percent from Indian companies. Twenty-one percent had significant levels of lead, mercury and arsenic. The ingestion of these metals “could result in lead and/or mercury ingestions 100 to 10,000 times greater than acceptable limits..". This is not the first time that the Journal has reported this. In 2004, a similar study uncovered very similar facts. The existence of heavy metals in Ayurvedic medicine will not be a surprise to most Indians who are probably familiar with the claims of Ayurvedic Vaidyas, that these, in a suitably processed form are not harmful to the human body. The Wikipedia article on Ayurveda quotes Vaidyas as claiming that the practice of using heavy metals therapeutically as anti-microbials and anti-cancer agents is an old one and they have no toxic effects since as they are "meticulously and elaborately processed to oxides, salts and ashes that do not have the same biological activity as the more active, unprocessed compounds". Unfortunately the detoxification process as described in Wikipedia (called samskara) is not exactly guaranteed to fill one with great confidence. The described detoxification is a simple chemical process which involves four successive rounds of boiling the crude Aconitum root in cow's urine (twice) and cow's milk (twice). This process is claimed to chemically modify both toxic and proposed therapeutic components of the root. It also extracts some of these compounds from the root into the boiling solvents, thereby decreasing their concentration in the final product. Like most of Ayurveda, these are just empirical statements quoting some of the Shastras. The above description of the detoxification of Aconite is from the work of a certain Thorat Dahanukar which was carried out on mice and has not been reproduced. There is no attempt to understand what cow's milk and urine have to do with the detoxification. I think for the moment, I will stick to standard (also known as Allopathic) medicine.
This seems to be the latest fashion in blogs. Like Orwell's, Samuel Pepys's famous diaries are now being serialised in real time as a blog. If you have never heard of Samuel Pepys :-( then this is a good place to start. Of course, there is the ubiquitous Wikipedia entry, dry, mechanical and lifeless as always.
Monday, August 25, 2008
Yes indeed! Most of you who know me are aware that for long I have admired Orwell and his writing. In fact, this blog is named after Orwell's column in the Tribune. (see the right column). So it makes me very happy to learn that Orwell's diaries on a day to day basis is being published in real time as a blog (though shifted in time by 70 years) at orwelldiaries.wordpress.com. Thus today, 25 August 2008, we have an entry for 25 August 1938. A lot of it has a rural feel to it, since Orwell was then living in Kent in a sanatorium recovering from a bout of tuberculosis and he describes the crops, the birds, the blackberries. Seems not very different from a contemporary description, until he actually comes to a description of some major event during that era. Of course the war is not too far and so, very soon we might expect more political entries. What better way to enjoy Orwell! The blog also has convenient footnotes to describe items that may not be familiar to present day readers, including strangely enough a link from blackberries and geraniums to the appropriate Wikipedia entry. Aren't readers supposed to know about blackberries, even in this present highly urbanised world? Or perhaps, as the New York Times cattily suggests, to distinguish them from the type you press with your fingers! But surely not for geraniums?
Saturday, August 23, 2008
Planetary supplies of fresh water are becoming more and more scarce as demand from six billion people on earth keeps soaring. Partly this is because world population continues to explode and many of its inhabitants are getting richer and and thus expanding demand. In other words it's the old story all over again that I explored in my 'food' posts - India and China are to blame! Be that as it may, and it may well be true, it is indeed a fact that water supplies are dwindling. Rivers such as the Nile, the Yangtze, the Jordan and the Ganges regularly peter out during the summer months and the water table in major cities like New Delhi, Chennai, Beijing and others have fallen drastically. Here are some little known facts which would help to put the problem in perspective. On an average, according to the Stockholm International Water Institute, on average each person on earth uses 1000 cubic meters (m^3) of water per year. A cubic meter being a 1000 litres, this works out to one million litres of water per year per capita! Now, before you think I, or the gentlemen at the institute above have been indulging in some vapourous stimulants to come up with such outrageous numbers, let me explain what these numbers mean. This is the average water footprint of each person on earth i.e. this is all the water we use for drinking, hygiene, growing food and all other activities. Or in other words, the water footprint of an individual, business or nation is defined as the total volume of freshwater that is used to produce the goods and services consumed by the individual, business or nation. It is then easy to understand the magnitude of these numbers. A kilo of beef needs 16000 litres of water (for grain fed cattle and therefore not true in India). a kilo of wheat or corn requires about 1000 litres for irrigation, even a cup of coffee requires around 140 litres of water to grow the requisite number of seeds to make that coffee. The actual drinking water that the metropolitan supply delivers to our homes (or, as in Chennai, more often than not, does not deliver) is a minuscule fraction of our total water footprint. The water footprint could also include items like a cotton shirt (which has a virtual water content of about 2000 litres). Consequently, an individual's water footprint is also dependent in many ways on his/her prosperity level. India's average water footprint per year per capita is around 980 cubic meters not very different from the world average. You can also calculate your individual water footprint from this site. For an average meat eater in India, this works out surprisingly to around 540 cubic meters per year, of which something like 520 is for food and 18 is for domestic use (this is the part which is actually supplied to our homes). Of this 520 for food, in India, almost 90% is for cereal consumption, the meat contribution being negligible. The same parameters including annual incomes applied to the US produces a number of around 1200, about 80% of which is from meat consumption. The difference in India between vegetarians and non vegetarians is in fact negligible. If anything, the vegetarian water footprint is marginally higher, presumably due to higher grain consumption. These and many other interesting facts can be discovered by playing with the water footprint site calculator given earlier. Which begs the question -- if most of us have a water footprint of around 500, why is that of the country around a 1000. Which part of the population is tilting the balance to such high numbers? Here are some other interesting facts which you can find from the papers linked at the site. For example, with regard to the water footprint of nations, in absolute terms, India is the champion -- 987Gm^3/year. Even though India's population is 17% of the world's, its people contribute only 13% to the global water footprint. On a per capita basis, the US is the champion -- 2480 m^3/year/capita followed by people in Southern European countries. On the other hand, despite our tendency to blame China's growth for most developmental problems, China has a much smaller footprint -- around 700 m^3/year/capita. However, as with many consumption patterns, India (13%), China(12%) and the US(9%) are the largest consumers of the global water resources. Interestingly, Japan's external water footprint ratio to the total footprint is very large (65%) compared to the three countries above (1.6% for India), mainly because it imports a large number of agricultural and industrial products. An interesting aspect of this external footprint is that, by importing say rice and other grains from another country with higher productivity per acre, we are actually reducing our own water footprint and making more effective use of water. Sources of water Finally, where is all this water coming from? All the fresh water on earth comes from precipitation. Of this, 61% is what is called Green water that flows through the landscape and is absorbed by soil and plants and is not available for direct withdrawal. About 38% is called Blue water and collects in rivers, lakes, wetlands and groundwater and is available for withdrawal. Irrigation from this blue water is the largest single use of freshwater (1.4% of the total), with cities and industries consuming a tiny fraction of the total usage (.1 %). However, this tiny usage actually creates a large local demand, thus draining nearby regions of ready supplies of fresh water as we have seen happen in India. Finally around 1.3% is lost through evaporation. In a future post, I will discuss what we can do (both individually and as a nation) to reduce water consumption. For those of you interested in reading some more, the August 2008 issue of Scientific American has an article on Water. The Water Footprint site mentioned in my post above is a rich resource for water related issues.
Nils Olav has been a part of Norway's elite King's Guard for 35 years, and even became honorary colonel in chief in 2005. Finally, in a crowning achievement of his career, Nils Olav became Sir Nils Olav in a morning ceremony on 15 August, watched by several hundred onlookers and attended by 130 guardsmen. Why is this news fit to print? Because Sir Nils is a penguin! And here is the news item along with a picture for all you skeptics. And as far as I can tell, unlike some other news items in recent times, this is not a hoax :-) . I have a question, though. How many of those guardsmen standing at attention in the picture suffered a thrombosis trying to stop themselves from cracking up?
Sunday, August 17, 2008
Nicolas Kristof, whom I have often quoted on my blog, is one of the few New York Times Op-Ed Columnists who are readable and have something worthwhile to say. Most of the others are either infantile (TF), hysterical (MD) or plain dull (PK). In his most recent Op-Ed column, Kristof decides to personally test out China's new experiment in allowing protest demonstrations provided prior permission is taken. It's a hilarious description of how the oppressive Chinese system works. Read it here. My take on this? Once the Olympics are over, it's going to be back to business as usual. Nothing will change (though I would be happy to be proved wrong on this one). Even now, if it were not a NYT columnist but a Chinese coming to get permission, he would just be labelled a counterrevolutionary and thrown in jail. This is not just me being predictably cynical about China. Zhang Wei who applied for the requisite license was promptly arrested for “disturbing social order.” Read it here para 5. There are no depths to which the perfidious Chinese system will not sink. Come to think of it -- why don't we send our comrades (whose admiration for that country is legion) to China to hold their hartals, bandhs and protest marches? Hopefully we will never hear from them again! Tailpiece: "Mr. Putin’s already stratospheric popularity at home has grown to Phelpsian proportions" - quote from the second article above. We now seem to have a synonym for 'Olympian' :) Update 19 August 2008: And so it goes on ... ...and on
Friday, August 15, 2008
This post is mostly about non carbon alternatives for electricity generation, induced by an article in Nature. However, that article may not be available to people without a subscription and furthermore, in addition to a summary, I also include here some numbers specific to India which are not available in the article. The numbers quoted in the rest of this post are taken from either the Nature article or from sources which are linked in appropriate places. The world's total energy requirement is around 45,000 terawatt-hours of energy a year, of which about 18,000 terawatt-hours a year, or roughly 40% is for electricity alone. (At 9000 hours approximately to a year, this works out to a constant 2 TW generation capacity). Electricity generation alone produces 10 gigatonnes of carbon dioxide every year, the largest fraction of all the fossil fuel derived emissions. India's total energy consumption is around 4000 kilowatt-hour per year per capita. Of this around 10%, or more precisely 460 kWh per year per capita is for electricity alone. (Some comparative figures are 28,200 for Iceland, 13,300 for the USA, 1,600 for China). These are all 2005 numbers. (Aside: The energy debate is sufficiently complicated as it is; however matters are made worse by different agencies using different units, depending on whether they are in the US or UK or elsewhere in the world. To make sense of this mad profusion in units, here is a quick conversion: 1 Quad = 1 quadrillion btu, a quadrillion is ten to the power fifteen. 1 kWh = 3412.14 btu. May the devil take the non-metricians). Now let us look at the distribution of different types of electricity generation in India. (Here again, there is some disagreement in numbers -- the Nature article gives the total for India, as I stated above, at 460 kWh/year/capita whereas this quotes 587). Of this 25% is hydroelectric, around 2.5% is nuclear, 69% is conventional thermal and the rest (a little more than 3%) is a combination of what is commonly called non-conventional energy sources (geothermal/solar/wind/biomass but in fact, is mainly wind). Hydropower development in the Brahmaputra river basin in eastern India is expected to result, by 2012 in six large power plants, which will add nearly 30,000 megawatts of generating capacity. (At present the total installed electricity generation capacity is around 118 gigawatts though using the above numbers gives us about 50-60 gigawatts. Thus there are significant discrepancies in various numbers floating around). Now a look at the rest of the world for these non-carbon-polluting sources. The total hydroelectric generation capacity in the world is 800 gigawatts, about 10 times more than geothermal, solar and wind power combined. The Three Gorges dam in China will eventually generate 18 gigawatts. In the best of all possible worlds, the International Hydropower Association estimates that hydroelectric capacity could triple worldwide with sufficient investment, the growth being mostly in Asia and Africa. It is expected that up to a terawatt of capacity could be added. However, while a clean technology, hydropower causes, as we in India have seen over the last few decades, enormous disruption in human lives, and enormous costs involved in relocating people, along with significant ecological damage caused to ecosystms downstream and upstream. Nuclear power produces 370 gigawatts of energy, around 15% of energy generated worldwide. (The number for India is abysmally small - less than 3%). With improvements in design, using breeder reactors, and introduction of thorium as a fuel, nuclear capacity can grow by a factor of two or three and continue for a century or more. In principle the world could be 100% nuclear power based. However, apart from being capital intensive (offset partly by their long lifetime), there are issues of storage of nuclear waste, diversion of nuclear fuel for nuclear weapons, the dangers of the spread of radiation in case of an accident and so on. Various different studies both by he IAEA as well as by academic organisations predict a rise to around 1000 to 1200 gigawatts of energy by 2050. Biomass and geothermal account for about 40 to 50 gigawatts of energy generation and are easily surpassed by windpower. The total installed capacity for windpower is around 94 gigawatts (or around 5% of total electricity generation) and at the present rise of around 20% per year, could triple in the next six years. In this, India too is doing very well. Unfortunately, its intermittancy means only up to around 20% of a grid's capacity can be met with wind energy. Incidentally large wind farms can affect local and potentially global climate by altering wind patterns and reducing the cooling effect of the wind, as large turbines slow the wind down. Solar energy is plentiful, particularly in a country like India which has negligible solar energy generation. Unfortunately solar cells have an efficiency of around 12-18% going up to around 20%, which is much higher than photosynthesis (1%). Additionally solar cells are still expensive, though their price is falling. Even though installed capacity is 9 gigawatts, the actual energy produced is much less, due to nights and clouds. The Earth receives 100,000 TW of solar power at its surface - enough power it is said, per hour to supply humanity's needs for a year. I don't see though, how this number adds up. It is also said that the world's primary energy needs could be served by less than a tenth of the area of the Sahara. But I am yet to see a clear calculation that backs this up. However, there is clearly no question that the Sun does represent a virtually inexhaustible and non polluting source of energy for our needs, if only we knew how to harness it efficiently. Other than wind power, India lags behind very badly in developing non-carbon methods of generating energy, including electricity. Its success with hydroelectric power is marked by controversial and incomplete resettlement programs for people displaced by large dams (coupled with somewhat knee-jerk extreme reactions by environmental fundamentalists). Given our rising energy needs, there seems to be no option but to develop one or more of these energy sources. However, with the nascent state of research in solar energy and the almost complete exploitation of wind energy, nuclear power today appears to be the only option to pursue in the short term (10-20 years). This is contingent on two premises: that the Department of Atomic Energy improve its track record significantly, in adding substantial electricity generation capacity (it has over the years fallen behind hugely, its own predictions of capacity addition) and secondly that the world stop treating us as a pariah state and agree to do nuclear commerce with us, so that we can buy nuclear fuel in the open market.
Today, 15 August, is India's 61st independence day. An ancient land but a young political entity. Is this one any different from any of the earlier ones? Not really...except that this is the first since I started my blog! I thought I should commemorate this fact in some way, like placing a flag or a marker as one passes. So here is that marker. As it happens, last evening, we went to see a two act one man play 'Mahadevbhai' by Ramu Ramanathan, acted out as a monologue by Jaimini Pathak. Mahadev Desai was Gandhiji's secretary but he was also much more than that. He was the Mahatma's friend, his translator, his diarist, his Boswell. It is to Mahadevbhai that we owe a debt for the detailed descriptions he left behind of the days of Gandhiji's life and hence of the nitty-gritty of the freedom struggle. The play bases itself loosely on Mahadev Desai's diary to take us through the crucial years of the freedom struggle, ending on 15 August 1942, the day Mahadev Desai died with Gandhi next to him. Many of the famous names of the freedom struggle -- Patel, Nehru, Bose, Tagore flit in and out of the diary and hence of the play, giving us a glimpse of the march to Dandi, the irony of the meeting on communal harmony in Godra, the Champaran and Bardoli Satyagraha and even many apparently ordinary day to day events in the life of the Mahatma. As we remember some of those men and women who gave us our freedom, one can do no better, to commemorate 15th of August, than to quote some of the lesser known passages of Nehru's Tryst with Destiny speech, whose first few sentences are mechanically taught to most school children in this country. However, that speech has some resounding cadences which have an echo even in today's India. The ambition of the greatest man of our generation has been to wipe every tear from every eye. That may be beyond us, but as long as there are tears and suffering, so long our work will not be over.... The future beckons to us. Whither do we go and what shall be our endeavour? To bring freedom and opportunity to the common man, to the peasants and workers of India; to fight and end poverty and ignorance and disease; to build up a prosperous, democratic and progressive nation, and to create social, economic and political institutions which will ensure justice and fullness of life to every man and woman. We have hard work ahead. There is no resting for any one of us till we redeem our pledge in full... All of us, to whatever religion we may belong, are equally the children of India with equal rights, privileges and obligations. We cannot encourage communalism or narrow-mindedness, for no nation can be great whose people are narrow in thought or in action.
Thursday, August 14, 2008
"This is not 1968 and the invasion of Czechoslovakia, where Russia can invade its neighbor, occupy a capital, overthrow a government and get away with it. Things have changed." - CONDOLEEZZA RICE, secretary of state Yeah, right! Only we can do it, in Iraq and wherever we feel is good for us. It doesn't even have to be a neighbour.
Saturday, August 9, 2008
Ismail Serageldin, Director of the Library of Alexandria has a guest editorial in a recent issue of Science Magazine, on the problems of science in Muslim countries. Despite our Muslim forefathers who first held up the torch of rationality, tolerance, and the advancement of knowledge throughout the dark ages of medieval Europe, he points out that increasingly intolerant social milieu that is driven by self-appointed guardians of religious correctness, who inject their narrow interpretation of religion into all public debates. Rejecting rationality or evidentiary approaches, they increasingly force dissenting voices into silence and conformity with what they consider acceptable behavior. Of course the Muslim world is not alone in this. Even in the technologically most advanced nation in the world, the US, there are battles over creationism vs. evolution and, in fact, though he doesn't say so, over stem cell research, contraception and so on. He stresses the need for a commitment to fight for the values of science and to reject obscurantism, fanaticism, and xenophobia. I can't help thinking that while we in India are lucky not to have to fight over evolution and creationism, we are no slouches when it comes to obscurantist behaviour and attitudes. Belief in Ram as a real person with a well-defined birthplace, and the bridge he constructed, or even arguing in the Supreme Court over which version of the Ramayan is correct to decide the fate of the Ramar Sethu, modifying recorded history, geography and geology to insist that Hindu civilisation has existed for a 100,000 years (or is it a million?) does not speak well of our rationalist attitudes. (I am not even mentioning astrology, which even many of our distinguished scientists believe in). Let me quote Serageldin again when he says we need to liberate minds from the tyranny of intolerance, bigotry, and fear, and opening the doors to free inquiry, tolerance, and imagination. Here is a personal plug: if you seriously believe in a rationalist view of the universe (let me stress that this need not be equivalent to atheism) please do click on the Brights link on the right hand column near the top of the page and join the Brights movement.
Thursday, August 7, 2008
In a recent Op-Ed piece in the New York Times, Nicholas Kristof, who specialises in reporting from some of the most dangerous places in the world including Darfur, has presented a new set of proposals to the Chinese Government regarding Tibet, which he says has the sanction of His Holiness the Dalai Lama. While reading it, I couldn't help feeling an odd sense of familiarity with the proposal. To take just a few examples (these are quotes from the article)
- The Dalai Lama would dial back to some degree on demands for political autonomy for Tibet, while the Chinese government would offer more cultural and religious freedoms - no "one country two systems" like Hong Kong.
- create a Regional Authority for Tibetan Affairs that would administer key aspects of life in all Tibetan areas, particularly education, culture and religion
- ...restrict migration into all Tibetan areas, inside and outside the “autonomous region,” through China’s existing system of residence permits. The Chinese authorities would stop issuing resident permits, known as hukou, to non-Tibetans for any Tibetan area, and would grant temporary residence permits, or zhanzhuzheng, only when no Tibetan is available to take a job. This would halt the flood of Han Chinese into Tibetan areas.
- The Tibetan language would... be used in government offices in all Tibetan areas, alongside Chinese, and there would be a new push (as there was in the 1980s) to increase the proportion of ethnic Tibetans holding government and party positions.
- The upshot would be a Tibet that remains politically under the control of the Communist Party.... it would be able to preserve its character indefinitely as a distinctly Tibetan and Buddhist region, both inside and outside the formal Tibet Autonomous Region.
This time when I visited Singapore (see the previous post) I went without my laptop. It turns out that this is the first time in some two years that I have been away from a keyboard for as long as four days. If there is one place which is a paradise for the internet junkey it's Singapore - everywhere starting from Changi airport to the hotels, internet is ubiquitous and it's all free and fast. And therefore all the more reason to avoid if you not planning to spend your vacation hunched over the keyboard. And....I survived (and so did the world)!! I had thought the withdrawal symptoms of not connecting to the net sometime at least during the day would start affecting my nerves to the extent that my feet would start moving inexorably towards the nearest internet cafe. But I hardly missed it and just for that, as Henry Higgins says 'I should be given a medal or even made a knight'. Perhaps it helped that this was mostly the weekend but at the end of it all, there were just 64 messages waiting to be answered (or not answered) not counting spam which took me just about an hour to get through. All in all, a valuable lesson learnt - to use a cliche, take time off to smell the roses (more like orchids in this case but the idea is the same). And there's always the TV in the room to catch up with who is killing whom in the world. My friend Omar (he who is not AMOK) says I have begun to use the perpendicular pronoun once too often like some others who shall remain anonymous. Alas, this post is guilty of more of the same. Perhaps I can think of some weighty matters not referring to me to discourse upon next. Continue watching this space....
Tuesday, August 5, 2008
In Singapore. On a short visit recently to the city state, I found these wonderful creatures in a special enclosure built, we were told, at a cost of a million Singapore dollars. Having only seen photos and movies of penguins on the vast scale-less expanse of the Antartica, I had not realised that they were quite small - just about waist-height. And the waddling walk with their chest thrust out of the patriarch tailed by a bunch of youngsters is vividly reminiscent of our pot-bellied politicians with their retinue of hangers-on. Here, for example is a bunch of them having a conclave: And so to Singapore. What can I say of this place that has not already been said before by a thousand, nay a million visitors before me? Its roads and sidewalks are so clean you could eat your dinner off it. None of the 'great' cities of Europe or of the US, Paris, Rome, London, New York can match it in organisation and cleanliness. Not the smallest piece of paper, not a wisp of a plastic wrap sullies its fair face. It helps of course, in this almost police state, to have severe penalties for littering (S$500), for eating in the subway (S$500), smoking in the subway and restricted public spaces (S$1000). Clearly nobody dreams of breaking the law, it seems. In fact even leaves which I noticed one afternoon on the sidewalk had been swept clean by the evening. How often do they clean the streets? Its excellent public transport is another great boon for tourists and locals alike. Singpapore is, of course, a tourists' delight and not just for shopping which is what most Indians seem to come for. (Out of sheer perversity we decided to avoid Little India and the phenomenally popular Mustafa Mall). Their innovative tourists attractions are fascinating for young and old alike -- Night Safari at the zoo, Tram Ride at the Jurong Bird Park where I saw the penguins, live shows with animals in both places, visit to Sentosa Island, keep people in thrall and holidays are for fun-filled family outings and picnics. Its Botanical Gardens and the Orchidarium is truly out of this world. Beats dragging a five year old around the Taj Mahal expecting it to develop an appreciation for Islamic architecture. Singapore is also a foodie's delight, though personally I found the food to be very indifferent at the innumerable Food Courts dotting the city. It's generally better to go to a reasonable restaurant though it's unnecessary to visit five star level places to get good food. The Government (or the People's Action Party which is the same thing) clearly believes that if you keep the citizens happy and content with enough money and things to do, they won't clamour too much for pesky little ideas like multi party democracy. However, one cannot but help admire the fact that the Government provides subsidised housing to all its citizens. As a result every Singaporean has a roof over his or her head. This is not only useful but absolutely necessary. Singapore being a city state has very limited land area available for construction, and so land prices are astronomical and beyond the reach of most middle level citizens. Some private plots in the suburbs are available for the rich and famous and it is here that foreigners are also encouraged to build their houses. We asked one of the guides whether there are poor people and beggars since we hadn't seen any. We were told that if there are, they are usually 'rounded up'. Nobody seemed to have the heart to pursue this line of enquiry any further and find out what eventually happened to the 'roundees'. One particularly remarkable fact that struck me was that in all the days we were there, one saw not a single policeman or a police car ever on the road nor did we ever hear the blare of sirens. This would be unheard of anywhere else. I cannot recall any other city I have been to (and I think I have been to quite a few) which had such a complete absence of the constabulary. How do they maintain the peace - in this high-tech city do they just sit inside their offices observing the citizenry through video cameras? Unfortunately I couldn't find even one in any of the open areas so here is a mystery. A police state without the police!! Or is it that once you have put the fear of god and hefty fines in people, they police themselves! What a great idea! Tailpiece: Singapore has much Indian influence as everyone knows. Here is a Metro Station which is particularly evocative of that fact!