Short Note On Comets

The cold water areas beyond Pluto are the regions of comets. During the early stage of solar system, when the sun was just ignited, its heat took lighter elements to the outer solar system. Hydrogen, oxygen and carbon collected into snow cotton like balls that float like a cloud. Comets are made of 'ices', ie ordinary water mixed with frozen gases such as methane, CO2 and ammonia. 

Comets move slowly in the enormous orbits around the sun. Comets do not shine while they are in the cloud. When the gravity of a passing star disturbs this cloud, comets are lost into the solar system. As comets move towards the sun, due to heat the frozen ice turns into gas forming a rapidly glowing cloud called its head or coma around its centre.

As it gets closer to the sun, the gas evaporates making its head bigger and brighter. A tail made of dust and gas is pushed out by the pressure of sunlight and solar wind. The tail will be away from the sun. When it passes very close, it gets enormous speeds and the tail points ahead.

Solar Wind

Streams of electrons and protons continuously flow out from the Sun's atmosphere and travel across the solar system. This rapidly moving stream of charged particles is called Solar Wind. About 1 million ton material is removed from the sun every second in the form of solar wind. These charged particles react with atoms of earth's atmosphere to produce northern lights and southern lights.

Life Story Of A Star

A young star is thought to be composed largely of hydrogen gas. Stars are believed to form inside large dense interstellar clouds of gas. Gas cloud starts contracting (under unknown reason), its contraction continues under gravitational pull of the gas. The pressure in the cloud increases and as a result, the temperature at its centre increased. At this stage, it is called a protostar. When the temperature reaches a certain level, nuclear reaction starts in the protostar. Hydrogen nuclei fuse together to form helium nuclei.

Large amounts of energy is released in the form of light, heat and radiation travels to the surface of the star. This energy creates an outward pressure and force. The contraction of the star stops only when the inward pull of gravity is balanced by the outward force of this radiant energy. At this time the star becomes stable in size and temperature. As the hydrogen inside the core depletes, the outforce of the radiant energy weakens, thus starting further contraction of the core.

This raises the temperature of the core. The extra heat from the core and outer region makes the star big and bright. But as the outer layer expand, it goes far from the nuclear furnace making it cool. The puffed up star looks red and cool. If the size is many times more than sun, it is called red super giant and if it is similar to the size of sun, it is called red giant.

The red giant stage is short. As hydrogen is consumed to form helium, the core contracts further and temperature rises. The helium nuclei then fuse together to form carbon nuclei. This is a critically unstable moment in a star's life as two layers are burning at the same time (outer layer hydrogen-helium and inner layer helium-carbon). The fate of the star now depends on the mass of its core.

If the mass of the core is less than 1.4 times mass of the sun, contraction stops at the size of the earth (this is known as Chandrasekhar limit). Such a star is called White Dwarf. Sometimes a white dwarf suddenly flashes millions of times brightly. This is called a Nova. As white dwarf cools, it becomes black dwarf and disappears. If the core mass is between 1.4 times Sun - 3 times Sun, the core shrinks to about 10Km forming a Neutron Star. If a Neutron star is born rotating very fast, it emits radiation in pulses. Such stars are called pulsars.

If star is with mass more than 20 times sun, its contraction continues. Then the core of the star collapses to become a black hole. Sometimes massive stars explode releasing a tremendous amount of energy. Such explosions are called Supernova.

Which Way To Turn Screw While Changing Car Tyre - Solved

While changing your car tyre, turn the screw in counter clockwise to loosen the screws and turn the screw in clockwise direction to tighten. Before changing the tyre make sure that you pull the handbrake and keep the car in 1st gear. 

Now keep a stone or a piece of wood on the tyre at the opposite end. Now loosen the nuts and then jack up the vehicle.

Big Bang Theory & Evidences

According to this theory, universe started with a huge explosion. It was not like a bomb explosion, it didn't explode from a specific point. It was an explosion which occurred everywhere in space at the same time. It was an explosion of space itself. Every particle of matter rushed away from every other particle. 1/100th of a second after creation of universe, the temperature was around 100 billion degrees centigrade. This was much hotter than in the centre of the hottest star.

Elementary particles were rushing apart in all directions. The abundant were electrons, protons and neutrinos. It was a kind of cosmic soup. After 1/10th of a second, the universe expanded and the temperature dropped to 30 billion degrees centigrade. 10 billion degrees after 1 second and 3 billion degrees after 14 seconds. After 3 minutes the universe became cool enough for protons and neutrons to begin to form into simple nuclei.

The nucleus of heavy hydrogen was the first to form, there was also helium nuclei. It was still too hot for atoms to hold together, they were ripped apart as they were created. Thousands of years later, it became cool enough for electrons to join with nuclei to form atoms of hydrogen and helium. The resulting gas began to form clumps under gravitation. These clumps condensed to form galaxies and stars after 5 billion years after the Big Bang.

Evidences Favouring Big Bang

The expansion of universe is an evidence for Big Bang. Expanding universe suggests that matter was packed much more densely in the early stages of the universe. The high density seen among quasars also suggest the same. Another substantial evidence comes from the cosmic background radiation. Astronomers believed that the radiation from Big Bang must still exist within the universe even in a feeble form. Radio-astronomers have discovered such faint signals, a constantly present background radio noise that pervades all space. This radiation is called the cosmic microwave background radiation and it is a relic of the ancient past.

The discovery of primordial abundance of elements is another evidence. The hydrogen and helium were the first elements to be created and thus it is seen in abundance in the universe. In the universe, out of 100 atoms, 93 are hydrogen atoms and 7 are helium. Elements heavier than helium are present in traces only. This suggests that soon after the very hot Big Bang, the universe quickly cooled as it expanded, denying the time required to form heavier elements. Heavier elements were made much later in the interior of massive stars.

Where Can You Get Yamaha R15 Bike Cover

In order to get original Yamaha R15 bike cover, you will have to go to the nearest Yamaha service center. They may not always have the cover in stock but you can order it and purchase it when it comes in stock.

How To Stop Facebook App From Playing Videos Automatically

Facebook's new settings in the mobile app plays all videos on the news feed automatically. This is very annoying as the videos start playing as soon as you scroll down. Moreover, it will make a huge dent in your data pack as these videos use up a lot of data. So the best thing to do is to turn off auto play. To do this

  1. Open Facebook mobile app
  2. Click on App Setting (Tab on the top right hand corner, just under the chat tab).
  3. Go to App Settings, scroll down
  4. Now click on 'Videos Play Automatically'
  5. Choose the option 'Off' or the 'Wi-fi only' option as per your requirement
 From now on, the videos won't play automatically. Thanks for reading.

Kepler's Laws Of Planetary Motion

Kepler's Laws are
  • The planets move in elliptical orbits around the sun and the sun is at one of the two foci
  • A planet sweeps out equal areas in equal times
  • The square of the period of revolution of a planet around the sun is proportional to the cube of the mean distance from the sun. 
Kepler was asked to study about Mars, by his assistant Tyco Brahe. It was supposed that the planets moved in circular orbits at constant speeds. Kepler found that the speeds changed with their distance from the sun. After several experiments Kepler found out that the anomalous movement of Mars could only be explained if the orbit was considered as an ellipse, with sun at one of its foci. Thus the idea of circular orbits were abandoned.

Features Of Scientific Knowledge

Scientific knowledge never stops. It is a dynamic and an ongoing process. A remarkable feature of scientific knowledge is that it is never complete. The more we add to knowledge, the more questions arise. New information is continuously added. Science is a self-correcting enterprise ie, it is open to change. Science is not dogmatic. Even the theories of prominent scientists were proven wrong. Science has no high priests who cannot be questioned. Any new discovery will be heavily scrutinized, discussed and verified by the scientific community.

Scientific knowledge is objective. That is, scientific results are repeatable and verifiable by anyone, anywhere if proper facilities are available. All new ideas must be supported by strong evidences. Sometimes it even takes hundreds of years for ideas to be verified. Eg: Demolition of Aristotelian ideas about universe.

Short Note On Scientific Method, Inductive And Deductive Logic

1. Observations

Scientists must observe how a phenomenon occurs and why it occurs. Scientists have to be clear about 'what to' observe and 'how to' observe it. The observations made by the scientists have to be correct and independent of their sentiments and wishes. Scientific observations may be about natural events or man made machines. All these observations are carried out systematically through carefully designed experiments or surveys in order to explain natural or social phenomena. These observations are then put in order, ie classified, carefully recorded in the form of tables or graphs and analysed. The aim is to discover regularities and patterns in the factual information obtained. A number of questions may be posed on the basis of observations.

2. Hypothesis

The next step is to formulate a hypothesis. A hypothesis is a statement put forward in the basis of reasoning, about the things that are being studied. It is an attempt to answer the questions that are posed. A hypothesis is formulated by taking into account all the observations that are known about the phenomenon under investigation. It tries to explain the known or predict the unknown but possible features of the phenomenon. Hypothesis can be described as an inspired guess based on reason and experience. Both inductive and deductive logic are used to frame a hypothesis.

a) Inductive Logic

A student comes late to the class for 3 days in a row. Then the teacher thinks that he will be late for the 4th day also. This is called inductive logic. 

If we have direct evidence about only a part of the phenomenon and if on that basis, we infer about the properties, behavior and other features of the whole phenomenon then we are using inductive logic. Inductive logic can be misleading and have different degrees of credibility and reliability. Conclusions have to be further tested for their reliability.

b) Deductive Logic

In a multiple choice test, if we find the answer by eliminating the other options then we are using deductive logic. For eg: For a question, there are 3 choices A,B,C. And suppose you know that B and C are not the correct answers, then A becomes the correct choice. This is deductive logic.

In deductive logic, the reasoning is more direct and we come to the answer by deducting the known quantities. 

Logical analysis involves risk or doubt. To test the hypothesis, we can use experiments.

3. Experiments

Experiments are situations designed to make certain observations under strictly controlled conditions. This sometimes involves mimicking nature. This allows the natural phenomena to be simplified for step-by-step study. The objective of an experiment may sometimes be to observe phenomena more minutely by the use of very sensitive instruments. The results of experiments will prove of disprove a particular hypothesis.

4. Laws, Models And Theories

We get scientific knowledge from observations and experiments. These results are tied up and related to each other in the form of logical, coherent theories or laws. A relationship between thing covering results of observations and experiments over a wide range of individual cases is called a law. 

A model is an artificial construction to represent the properties, behavior or any other features of the real object under study. Eg: Human heart.

A theory is a set of few general statements that can correctly describe or explain all experimental observations about the properties and behavior of a large number of varied objects, phenomena, situations or systems.

How Often Does BSNL Change IP Address - Solved

Bsnl assigns dynamic IPs to its broadband and Wi-Max users. Sometimes you might run into troubles like getting banned by your IP address from popular websites like facebook, google etc. You might not have done anything wrong and in many cases it will be a one off 'false positive'. Once you get banned, the only thing you can do is to wait until BSNL changes the IP address of your connection. This may take an hour, 12 hrs or even couple of days. The recent trend is that BSNL changes IP address every two days or so. Which means, the age old trick of switching off your modem for 10 minutes won't work all the time.
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