Friday, 27 July 2012
Be it climate change, economic situation, politics, society, relationships - we hear a lot about stability, equilibrium, feedback and these days the term tipping point is used frequently.
We, the homo sapiens, are comfortable when things are going as expected and we can predict what is going to happen, at least, in the near future. It just makes planning easier, there is more time do other interesting things - a state of equilibrium (stability) is sought.
Stability is defined as a state in which a system tends to return to its original state after being disturbed.
A good example of such stable equilibrium is a bowl with a marble in it. If we disturb the marble by moving it up the side of the bowl and let go then after a few oscillations, the marble returns to its original position of stability.
If the bowl was upside down and the marble balanced at the top of the bowl then a disturbance in its position will lead it to fall off, never to terun to its original postion. That is unstable equilibrium.
The question is what gives rise to stability? - why should a system return to its original position when disturbed?
It does so because a disturbance causes the system to generate some sort of restoring force which operates to cancel the direction of change.
Gravitational forces pull the marble back towards it original position. However, the marble oscillates for a while before settling down.
When you disturb something, you need to do work which is stored in the system as energy (potential energy or I shall call it latent or hidden energy) which has to be eliminated before stability is regained. This is achieved by dissipative forces or friction in the system.
Friction converts energy to heat - kind of wasted energy.
For the marble, the new displaced position gave it a higher potential energy. Oscillations about the lowest point in the bowl, cause loss of energy due to friction and gradually the marble returns to stability. If the bowl and the marble were completely smooth with no friction present then the marble will oscillate for ever.
We have described above, what in physics is called
negative feedback in which stability is regained after the system has been disturbed.
A familiar example of negative feedback at work is the thermostat of your central heating system. You set a temperature and the boiler comes on to heat the room to this temperature. But the boiler doesn't cut-off at the exact temperature chosen on the thermostat. If it did so, then as soon as the temperature drops by the smallest amount the boiler will have to come back on again. What the actual systems do is to have a small acceptable range of say about 0.5 degrees on either side of the thermostat setting. The boiler heats the room to the setting plus 0.5 degrees and cuts off and only comes back on when the temperature in the room falls to the setting minus 0.5 degrees.
Refrigerators, ovens, fan heaters, air conditioning systems all work on this basis. These are examples of what we call Linear Control Systems. Wiki has a diagram to explain how they work
Global climate regulates itself through feedback mechanisms.
Economic activity, our personal relationships all seem to operate on the basis of feedbacks and responses.
In part 2, we shall look at Positive Feedback...
Sunday, 22 July 2012
(An updated version of this post is available here). Application to hypo- and hyper- thermia are also discussed there.
Heat is generated in biochemical reactions in cells. Each gram of carbohydrate generates 4 Calories, while fat and protein generate 9 and 4.5 Calories respectively.
Humans are hot-blooded and their body temperature is maintained constant at about 37C, the heat produced in the body has to be given off to the outside. This is done through breathing, sweating and radiating away heat energy to cooler surroundings, say at 20C.
Your calorie consumption goes up if you are physically active, like running or climbing stairs than when you are sitting calmly. In one hour, a 70 kg man would burn, approximately, 80 Calories sitting; 110 standing; 320 walking and 500 jogging.
Suppose, that every day a human consumes 2000 Calories (Some eat much more and get obese!).
We can calculate, using physics, the amount of energy produced in a day.
The Calorie used by nutritionists is actually equal to 1000 times the calorie used by physicist to measure energy. Note C and c in the two definitions of energy.
1 Calorie = 1000 calories or 1 kcal
In physics the usual unit to express energy is a Joule (J), and 1 calorie = 4.18 J
So we consume 2000 x 1000 calories/day
= 2,000,000 calories/day
= 2,000,000 x 4.18 J/day
= 8,360,000 J/day
To make sense of Joule per day, it is better to talk about power that is J per second or Watt (W)
A day has 24 x 3600 second = 86,400 seconds
We produce 8360000/86400 J per second (W) = 96.76 W (nearly 100 W) and this is given off to the surroundings as heat.
A human gives off heat equal to that of a 100 W incandescent light bulb (old style light bulbs) which actually converts most of the electricity to heat.
The new fluorescent light bulbs and particularly LED lights are more efficient in converting electric energy to light and that is why they do not get too hot when in use.
They are also cheaper to use.
Now you know why the room feels very warm when a lot of people are present and talking animatedly.
Or why you sweat and breath faster when jogging - you are burning extra Calories and producing heat faster. The body has to get rid of the extra heat by sweating and respiration.
Thursday, 19 July 2012
There are over 7 billions of us in the world today and we are living very well thanks to the available cheap energy.
How under priced is the energy?
About a factor of 500 relative to manual labour - this is how it works out...
A gallon of petrol costs £6 in the UK (about £3 in the USA!) and provides energy equivalent to 500 hours of human labour worth £4000.
The amount of work that oil performs for you is equivalent to having hundreds of slaves working round the clock.
Thanks to cheap oil, even the kings did not have the comfortable life style that an average middle class family now enjoys.
It is one of Ravi's laws of nature that when something is cheap, it is bound to be misused.
Coal, gas and oil are no different. Humans have wasted energy as if it is unlimited, ignoring the damage to environment and climate. Cheap energy has also fuelled overconsumption.
Did you know that only humans and their pets suffer from obesity?
Have you heard of a wild animal being fat?
Cheap energy has also prevented development of plentiful, unpolluting renewable energy like solar and wind.
Global power consumption is 15,000 GW.
Solar power falling on the Earth is 120,000,000 GW!
This is 8000 times greater than what we consume.
But, humans have failed to tap this unlimited source of energy because buried under ground they found a heap of fossil fuel that will do them for another 100 years or so.
Never mind the damage - lot of it irreversible - that is being caused by the folly.
Some people are asking - is it too late? Most do not care.
I do not know the answer but feel sure that soon it will be too late.
Enjoy the lifestyle while it lasts!
Tuesday, 17 July 2012
Science For All
An exciting and innovative series of science talks launched in East Kilbride in October 2006. The Science For All programme is the result of a partnership between University of Glasgow & Scottish Enterprise in Lanarkshire.
The creator and presenter Dr. Ravi Singhal specifically designed the community based programme to highlight the role science plays in everyday life and improve the understanding of science in today's modern world in an engaging and informative way.
No previous knowledge of science is required and everyone is welcome to attend. The talks are most suitable for secondary pupils and adults of any age.
'The talks will be entertaining as well as being informative and thought-provoking for all attending. We are hoping to attract as many people as possible to the talks and guarantee there will be something for everyone, from the beginner to the expert.'
Audience comments include 'his lectures are so well prepared and well illustrated...his presentation is suitable for an audience with even quite limited previous knowledge of physics or cosmology, but also for enthusiasts.
All talks are free of charge and will take place from 11am on Saturday mornings in the James Watt Auditorium, East Kilbride Technology Park, G75 0QD. Click for map
To find out more email firstname.lastname@example.org more information.
· Talks 60 to 64 Population: Elephant in the Room (To be scheduled)
· Talk 59 Renewable Energy Sources Glasgow Science Festival 10 June 2012 (120 Minutes)
· Talk 58 Climate Change and Oceans Glasgow Science Festival 9 June 2012 (120 Minutes)
· Talk 57 Climate Change Dumfries Science Festival 10 May 2012 (120 Minutes)
In 2010 and 2011, three eight-hour sessions were held in the Department of Life Long Learning at Strathclyde University, Scotland. The topics were Exploring the Cosmos, Nanotechnology and Einstein & the Theory of Relativity.
Dr Ravi Singhal has lived in East Kilbride since 1970 and recently retired from Glasgow University's Department of Physics & Astronomy after 36 years. During that time he taught students from a wide range of disciplines and covered topics as diverse as birth of the universe to quantum mechanics. Dr Singhal is a widely published academic with almost 200 research papers, reviews and book chapters related to lasers, environmental and nuclear physics.
A passion for science and education combined with a desire to 'give something back' to the community Dr Singhal found retirement gave him the perfect opportunity to start up the Science Talks programme:
'My talks are designed to improve the awareness and importance of science at a local level and highlight the role it plays in everyday life...volunteers who will be able to expand the programme and give different talks to the community on diverse subjects including medicine, the environment, alternative energy sources and nanotechnology.'
Population – Elephant in the Room
We have only one planet and its resources are limited. Global population quadrupled during the 20th century.
Such is the dynamics of exponential growth that even if the population increases half as fast (doubles in 100 years), in about 1300 years each of us will only have a patch of 5ft x 5ft on dry land with no room for plants, animals or anything else. Overcrowding will be felt much before that. In fact mother Earth might get fed up at some stage and do something about her childrens' behaviour.
Consumption and the number of domesticated animals increases in line with population growth. We are depleting non-renewable resources and polluting the environment at a rate that the Earth cannot cope with.
Just now we are using resources 1.5 times faster than the Earth can regenerate. If everybody consumes as much as the Americans do, then we require resources of fifteen Earths.
Our planet responds to the stresses we create.
Bio-diversity is diminished.
Global climate is impacted by the burning of fossil fuels.
Oceans, where 60% of all photosynthesis happens, become polluted, more acidic and less able to sustain aquatic life.
Overgrazing is a major cause of desertification, irreversible loss of topsoil with consequent impact on the fertility of agricultural land.
Aquifer depletion due to over-pumping & retreat of mountain glaciers in response to rising temperatures create serious concerns about future fresh water supplies for human use and for agriculture.
Higher global temperatures are causing sea levels to rise, threatening many highly populated coastal areas.
Some of the above global parameters have already passed the tipping point and further changes can happen uncontrolled, quickly and irreversibly.
Various estimates put the carrying capacity of the Earth from 500 million (at US level of consumption) to 10 billion (at an unacceptably low level of consumption).
Nobody wants to talk about managing population growth.
Population is an elephant in the room. It has been more convenient to ignore the problem.
The fundamental issue is the growth in population and that must be addressed urgently. Education, empowerment of women, birth control can make a difference.
We have to ensure that the carrying capacity of the Earth is not further damaged by our excessive consumption habits.
Energy has been too cheap, at least four times cheaper than its true cost and must be priced correctly. A rapid transition from non-renewable fossil fuels to the plentiful supply of renewable solar and wind energy is essential to manage our climate and pollution.
There is enormous potential for efficiency gains by innovative designs and good practices.
For example, plug-in hybrid cars can potentially solve the storage problems for electricity, reducing the need to provide extra power generation capacity at peak demand times.
Smart grids and smart metering will go some way in alleviating the peak load problems. Regenerating our forests will help in stabilising the climate.
Food and water security can be helped by consuming more plant proteins in preference to animal protein which is up to ten times more water and energy intensive. Demand for animal protein is rapidly increasing in the BRIC countries and others.
Bio-fuels are joker in the pack.
It may not be too late to act, but the geo-political situation does not inspire confidence.
Nano- and digital- technologies will help to alleviate many of the problems but only if the population stabilises. The US population is projected to increase by one hundred million by 2050. Imagine the extra resources required to accommodate such numbers at the current US consumption levels. Over 2500 million people in China and India would like to consume four times more than they do now!
There are those who talk about space colonisation and people living on asteroids etc.
Technologically it might be possible sometime in the future but the question one needs to ask is: “What are the 7 billion humans on the Earth for? Why are they here?”
Surely human race is not here just to increase their numbers but consideration has to be given for the quality and fulfilment of life.
We have the choice of managing the population and what we consume and saving our civilisation by acting now, or let nature do it in her own way – that will not be pleasant for sure.
What do I tell my daughter when she asks “What type of world shall I inherit, daddy?”
ScienceforAll, a Community Education Initiative, will look at the issues and their potential solutions in a series of six 90-minute talks this autumn. Further announcements about the free talks will be made at the end of August 2012. ... Ravi Singhal (17/07/2012)