21 June 2012

Which is colder, Midnight or Sunrise?

          What is coldest time during a day? Common sense may suggest that it is Midnight and experience would suggest that it is just before sunrise. How many of you ever wondered why is it so? Its a common man's question, no? Sun is our supplier of heat and so the coldest time should be midnight, since that is the time we miss our Sun the most. Then why isn't midnight the coldest of all hours?
          Of course, Sun is our supplier of heat. But the thing is, he doesn't supply it to us directly. The heat (or temperature, loosely) we feel normally is that of the lower atmosphere in contact with the earth's surface. This heat is not the same heat coming from Sun. The energy coming from Sun, when it reaches earth's surface contains majorly visible light which does not have heat content. Our lower atmosphere (or the gases present there) cannot interact with this visible light. Our earth absorbs this heat and gets heated up. Then earth begins to give out this energy in form of longer wavelength radiation called Infra Red (IR) radiation (When you are near a fireside, visible radiation is what you call 'the light' and IR radiation is its warmth). The gases in the lower atmosphere including water vapor and carbon dioxide can absorb this IR radiation and that is what we feel as atmospheric temperature. In short, it is not Sun that gives the warmth we feel, but the Earth. In day time, our Earth stays taking in and giving out radiations, keeping a balance. But during night time there is no taking in, but only giving out. It is this given out heat by Earth that keeps us warm during nights. Otherwise we would have all gone frozen to death. Earth keeps on giving out heat energy without any intake of energy until the Sun shows up again. Now you can guess what happens just before sunrise no? Earth has lost maximum of its energy content and that is why dawn is the coldest of all time. Now it is also clear why isn't midnight the coldest of all hours. Because at midnight, the heat loss from earth is only half along its way to dawn.

14 May 2012

Why shouldn't we use mobile phone at petrol pumps?

          All among us have seen a warning board 'Don't use mobile phone' or something like that in petrol pumps (gas station in US). Haven't we? But do we really know why we should not? Isn't it interesting to notice that this warning is based on a pure myth? Yes, it is.
          The warnings of mobile phone hazards in petrol pumps started circulating by the beginning of 2000's, pointing to a petrol pump fire happened in Indonesia in 1999. The driver of the car was said to be using his mobile phone and the pump got fire. But the truth is, there is no direct evidence available anywhere to prove that such an incident ever happened.  Many other similar baseless stories are circulating widely through internet. There are independent authentic study reports published by American Petroleum Institute, Australian Transport Safety Bureau and Australian Mobile Telecommunications Association all of them saying they could never find a cell phone ever causing a fire. They had chosen around 300 petrol pump fires happened worldwide, for their studies. And so this warning stands purely based on a myth! Almost all the reported petrol  station fires have been caused by static electricity (similar to what happens in clouds in thunderstorms).
          Now a few words on the science of the matter. The risk which the petrol pumps are taking is that of a spark that can set off the petrol to fire and so to explosion. The minimum energy a spark should possess to ignite petrol vapor is around 0.2mJ. It is true that a fully charged mobile phone battery contains around 5 million times this energy. But the problem is, they are not designed to make sparks! If the internal circuitry is very faulty, lithium ion batteries can explode while charging. But how many of us use a mobile phone that is being charged in a petrol pump? Of course, the internal electronics of the phone can make a spark but it will be too small. Why should we bother only about mobile phones when the stereo or pocket-torch you use has higher risk of spark inside? Leave them all, what about the heavy Car battery which is capable of giving you a good shock if you don't handle it properly? Anyway it is becoming customary to blame mobile phones for whatever happens wrong, from infertility to memory loss, right?

(Possibly there are two reasons why mobile companies themselves issue such a warning. One is mobile phones don't come with in-built safety measures against truly hazardous highly inflammable situations. Second is the fear of legal liability if ever anything goes wrong somehow. Anyway let us strictly avoid mobile phones while driving)

22 March 2012

Moon doesn't always rise in the evening!

Most of us think Moon does the night-duty in an office where Sun does the day-duty. Majority of our literature pictures Moon like that; someone who rises in the evening after sunset and sets when Sun rises. But the fact remains, only once in a month our Moon does like that. If you are a good observer without much knowledge in astronomy, you may know that the fact I said is right. But still, you don't know why it is like that. This time we will talk about the Moon's drama up there in the sky.
As you all know, the shape of Moon we see is not always the same. It waxes and wanes in size and shape (വൃദ്ധി-ക്ഷയങ്ങള്‍) called the phases of Moon. Most of us think that this is due to Earth's shadow falling on Moon, don't we? But thing is NOT like that. Earth's shadow has nothing to do with this. It is because, as Moon goes around Earth, from here we see it from different angles on different days. I can make it more clear with a picture below.

Here the situations of Moon being at different positions around Earth is shown. Sunlight will illuminate Moon as it does to Earth. As Moon is a sphere, only half of it will be illuminated at a time (Exactly this is how half of Earth experience day and other half experience night at the same time. When at one side of Earth it is noon, the opposite side of it will have a midnight as shown in picture). As Moon goes once around Earth in every 27 (approx) days, its position around Earth with respect to the Sun rays will be different on every day of this 27 days period. Just take a little time to look at the picture. Seeing from Earth, when Moon is in the direction where sunlight comes from, the part of Moon illuminated by Sun is on the back side and so we cannot see Moon at all. In other words, we are seeing the 'night' in Moon. That day is what we call New Moon. Now consider when the position of Moon is opposite to the direction of Sun, the whole of illuminated Moon is visible to us, giving us a full moon day. (From picture you can also make out that a full moon comes right ahead on sky at midnight) On all other days we can see only a part of illuminated surface of Moon which becomes larger when we go from new moon day to a full moon day. In short it is not the shadow of Earth but the shadow of Moon itself, that causes the phases.
Now let us come to the point in title. First of all, we have to remember that the rise and set of any object on sky is due to the rotation of Earth around its on axis. As we have seen, on a new moon day Sun and Moon are on the same direction and so they rise together. (Yes, Sunrise and Moonrise are together!) But on a full moon day, they are on opposite positions and so Moonrise and Sunset happens together. That means Moon can rise at any time. On a particular day it will rise 5o minutes later it rose the previous day due to its motion in its orbit around Earth.

27 September 2011

A shock-relieving talk on Shock Treatment

       Majority of us keep a horrifying picture about Shock treatment used for the cure of mental illnesses. The bad credit goes mainly to the movies that mislead us and give a feeling that it is some kind of torture or punishment given to the most violent of mental patients.
       So, here we are going to have a talk on the same Shock Treatment that I hope will untether you off some misconceptions.
       'Shock treatment' is just a nickname of this method. Psychiatrists call it as 'Electroconvulsive Therapy' or simply ECT. It will be interesting to know that ECT is the first discovered meaningful treatment method in psychiatry (for movies have always picturized it as a last resort). For the sake of a little history, there was no meaningful treatment for mental illness around just 70 years ago. Von Meduna, a Hungarian psychiatrist, observed that epilepsy and schizophrenia rarely coexist. Even if they did, the seizures (or fits, loosely speaking, the sudden movement of muscles) associated with epilepsy reduced the severity of psychosis. This lead him to develop a treatment for psychosis: to induce seizures artificially using drugs. But use of drugs had many limitations because there was no considerable control over the way seizures occurred. Thereafter, Carletti and Bini, two Italian psychiatrists discovered that electricity can be used to induce seizures in a much controllable way. In 1938, the first experiment of ECT was done on humans, to be found a great success.
A psychotron used to control ECT
       ECT is not at all a cruel treatment. Before applying ECT to a patient, he is always undergone a 'fitness test' including EEG, and X-ray. To those who think it is a torture, ECT is never conducted on a conscious patient but is always given after an anesthesia. That means you don't feel any pain at all. Also drugs are given to prevent very violent movement of muscles during seizures. While doing all these pre-ECT steps, the patient is allowed to breath pure oxygen (a process called hyperventillation). The amount of current passed  is only around 0.5-0.8 ampere and that is for less than 4 seconds, using an apparatus called psychotron. This current never reaches the brain. It just flows through the scalp tissues and so there is no 'struck by lightning' type effects as we see in movies. This current can stimulate brain activity. It is this stimulated brain activity and NOT the electrical stimulus that causes the sudden muscular movements. When the effect of anesthesia wears off, the patient would wake up comfortably.
ECT produce recovery faster than drugs. It is also used in drug-resistant subjects (that is if patient does not respond to medicine) It is not necessarily meant for only the very violent and uncooperative patients (for such patients ECT will be the only way) but is also prescribed for very depressed patients. Psychiatrists say that patients who have received ECT find it less frightening than going to a dentist!
       One more interesting fact: despite being a 70 year old and globally used method, no one knows exactly how ECT works in human body!

21 September 2011

Polysomnography: Measuring sleep!

Today let us talk about another interesting term, Polysomnography. Those who already know that the Latin word 'somnus' means sleep, can guess what polysomnography deals with. Yes, it is a standard procedure to evaluate sleep, mainly for the cure of sleep disorders.
Well, when I say 'measuring sleep' what actually are we measuring? Polysomnography is a multi-parametric test (means it measures different parameters connected to the sleep activity, lest you are frightened by the term multi-parametric) Mainly there are three parts in your body that responds directly to your sleep; brain, eyes and muscles. The study of activity in these three parts constitute the core of polysomnography. Measurements are carried out by placing electrodes on specific parts of the body and measuring the voltage change associated with the corresponding activity.
Now let us have a close look at the core parameters:
Brain activity:
It is studied by the ordinary EEG (Electro Encephalography) technique. It is based on measuring the bioelectric aactivity of brain by placing electrodes on the scalp of the person in sleep. EEG will look like a polygrah, the one you see in a seismogram record of earth quake. Like a random scribble made by a pen. But by looking at EEG, the researcher can understand the various stages of the person's sleep.
Eye movements:
It is studied by a technique called Electro Oculography (EOG). It is based on a rarely known fact that the front part of our eye called Cornea is electrically positive with respect to its hind part Retina. This voltage will obviously change when eye moves left, right, up or down. EOG is based on the measurement of this voltage, thereby giving an idea about the eye-movements.
Muscle activity:
This is studied by a technique called Electro Myogram (EMG). The movements of our muscles are a result of rapid electrical activity within the muscle tissues. EMG measures the voltage change associated with it. In polysomnography, EMG electrodes are usually placed over the chin muscles.

A sample polysomnogram
Along with these many similar activities in the body can also be studied for a very detailed analysis, three of them being  breathing, heart rate and contraction of leg muscles.