Why have fossils given rise to many myths?

Fossils are the remains of animals or plants which once lived on the Earth millions of years ago. When fossils were first discovered, people did not really understand what they were, and so, many myths and folklore developed over time, about where fossils came from.



            The coiled shell of some fossils led the Ancient Greeks to believe they were related to the ram-god Ammon. In China, these were also thought to resemble horns, and were called ‘horn stones’. In England, they were believed to be coiled snakes that had somehow lost their heads, and turned to stone. Echinoids, also known as sea urchins, are amongst the most commonly found fossils. In some places, they are considered to be snakes’ eggs, which have the power to protect one from deadly poisons.



Fire Eating Dragons



            Over 40,000 years ago, giant bears roamed over Europe. Some of them were buries in caves while hibernating, and over hundreds of years, their bodies turned into fossils with huge canine teeth. When these fossils were discovered in the Middle Ages, they were thought to be the remains of a mythical creature, the fire breathing dragon.



 


How did life originate on Earth?

Earth is estimated to be about 4.5 billion years old, hand for much of that history, it has been home to life in one form or another. Today, there are several theories for how life arose on Earth. The first of these is that life was created by a Supreme Being or spiritual force. The second theory is that life began in another part of the Universe, and arrived on Earth by accident when a comet or meteor crashed.



            Scientists say that life began around 3.5 billion years ago as a result of a complex sequence of chemical reactions that took place spontaneously in the Earth’s atmosphere. Molecules were formed as a result of these reactions. The molecules then interacted with one another, and this eventually led to the earliest forms of life.



            The first beings were probably bacteria which survived on naturally occurring food, and did not breathe oxygen. The fossils of these oldest forms of life have been found in Australian rocks dating back 3.5 billion years.


How did the Earth come into existence?

From the beginning of time, human beings have wondered how the Earth came into existence. Different religions have different explanations Scientists claim that a vast, dark, very hot cloud of dust swirled around a newly formed sun. Gradually, the cloud cooled, and the gas began to condense into billions of droplets. Slowly, these droplets were pulled together into clumps by their own gravity – and they carried on clumping until all the planets, including the Earth, were formed. In short, scientists and researchers have been arguing for centuries about how the Earth was formed, and the debate still continues.


When did slavery end?

Between 1450 and the late 1800’s, it is estimated that between 10 and 15 million Africans were kidnapped, and sold into slavery. The slave trade was incredibly profitable, but very cruel too. For over 300 years, slaves were captured along the west coast of Africa, often with the active help of African kings and merchants. Slaves were traded for beads, textiles, brandy, horses, and guns. Slavery was illegal in the United States after the Civil War, but slaves continued to be traded in Central and South America for another 40 years, until finally slavery was declared illegal in Central and South America as well. 



Slavery existed not only in America, but in other parts of the world as well. Denmark was the first European country to abolish slavery in 1804, while Britain abolished slavery in March 1907. In the United States, slavery was one of the main issues in the Civil War between the North and the South. The last day of legal slavery in the USA was 31st January, 1865, while the world wide abolishment of slavery took place only in 1926.



 


Why do we say that the beginning of the Earth can be traced to the Hadean Period?

The Hadean Period started when the Earth was formed about 4.5 billion years ago. During Hadean times, the Solar System was forming, probably within a large cloud of gas and dust around the sun. The sun was formed within such a cloud of gas and dust. The tendency of matter to clump together finally resulted in the formation of substantial bodies like the planets, and their moons.



            The oldest Earth rocks and Moon rocks we know about both date to this time. Water was brought to Earth by comets that crashed into the Earth. This water boiled into steam, because the Earth was still very hot, and formed a steam atmosphere around the Earth. As the Earth cooled down, about 4.3 billion years ago, the steam in the atmosphere also cooled down, and fell as rain on the Earth, and that made the oceans. By 4.2 billion years ago, Earth had land and oceans.


Why are there two high tides each day?

With reference to the answer that appeared in these columns on Feb 29, a discerning student might very well ask: The centrifugal force is not a real force, so what is the real explanation of tides?

            It is not difficult to explain tides. The question to ask is: Does not the moon’s gravity pull the rest of the earth, which is under the ocean water, towards it as well?



            It does. But the surface directly under the moon is nearer to it than the rest of the earth below, and hence gets pulled more. If this surface is water, being more elastic, it rises in the direction of the moon. The water at the ocean floor ‘remains’ with the earth. The difference between the ocean surface and the floor becomes greater than it normally is. We recognize this as high tide.


            Coming now to the opposite side of the earth, the bulk of the earth is nearer to the moon than the surface here and is pulled more. Water at the ocean floor here is ‘carried along’ with the rest of the earth towards the moon, but water on the surface stays where the lesser pull on it dictates. Again the difference between the surface and the floor increases and we see a high tide. When the moon is at the horizon at right angles to the overhead position the ocean and the earth below it are at roughly the same distance from the moon and experience the same pull. The ocean depth is normal. But, because some of the ocean water has flown to where there is a high tide, there is less water here and we see a low tide. Of course, this is a very simple model and the tides are influenced by many other factors, such as latitude and the shape of the continents.

How is the height of mountains measured?

There are various kinds of methods and they are all based on a method known as “triangulation”. If one knows one side and two angles of any triangle (or two sides and one angle), one can find out the rest of its measurement. Whether the land one wants to measure is a hectare or 1000 hectares, the method of measuring is the same. One begins by measuring one distance very accurately with a chain, steel or wire.

            This now becomes the side of the first triangle and is usually a level piece of ground between two landmarks. Now select a third landmark and make this the apex of the triangle. Then the angle it makes with each end of the first line is measured. These are the requirements for measuring the area of the triangle as described above (one side and two angles of a triangle).



            The instrument for measuring these angles is called a transit; with the area of one triangle the land to be measured into triangles should be divided until the area of the entire piece of land. The transit works vertically which is called leveling as there is a spirit level at the base of the instrument that indicates when it is in level. By raising the sight to any landmark on a mountain, the same process of measuring angles can be done and the length of one side (the height) can be measured.


The changing earth

The Earth’s crust has been in constant motion since its formation 4.6 billion years ago. Fractured into a patchwork of plates and floating on currents of molten rock beneath, the plates collide and pull apart.

            In fact the floor beneath your feet, even though it feels stable and motionless, rests upon a land mass that is in continuous motion. The plates that form the Earth’s crust are 50-100 kilometers thick. It has long been suspected that the plates are in motion, but the mechanism that drives them remained a mystery for many years.



            The east coast of South America and the west coast of Africa look as though they would fit together like the pieces of a jigsaw puzzle. With a bit of rearranging, most of the continents can be put together too. This was one of the first clues to continental drift, but other evidence supports the theory. Recently, the magnetic properties of rocks have been used to demonstrate the movement of continents. Lasers measure the movement across the San Andreas Fault in California, where two continental plates slide past each other. Measurements from satellites show North American and Europe to be drifting apart at the rate of about 4 centimetres a year.



            Today we know that all the surface elements of planet Earth are in constant motion. To understand continental drift we have to understand how these elements, or plates, move. The study of the crustal plates and their movement is called Plate Tectonics.



            Current form within any liquid when it is heated, just as they do in a pot of boiling soup. Similar currents form with the Earth’s thick, dense mantle. Radioactivity in the Earth’s core is a cause of the uneven heating of the lower mantle.



            As the semi-molten rock of the mantle is heated, it rises, creating massive, slow convection currents within the Earth. The heated rock spreads laterally at the base of the solid lithosphere, dragging fragments of the Earth’s crust with it. As the Earth’s crust moves, volcanoes and earthquakes occur.



            A powerful convection current pulls the Earth’s crust apart. Rift valleys form where continental plates separate. East Africa’s Great Rift Valleys, evidence of a continental pulling apart, is also a glimpse of an ocean in the making. When the rift is deep enough, it will be flooded by the sea.



            The Gulf of Suez and the Gulf of Aqaba slowly advance into rifts that mark a fracturing continent. A gift extends from the Red Sea and splits at its northern end, signaling the eventual of Africa and the Middle East.



 


Why and how do continents move?

The plate Tectonics theory was formulated in the 1960s to explain the phenomena of continental drift and seafloor spreading, and the formation of the major physical features of the Earth’s surface. The Earth’s outermost layer is regarded as a jigsaw of rigid major and minor plates up to 100 kilometers thick, which move relative to each other, probably under the influence of convection currents in the mantle beneath. Major land forms occur at the margins of the plates, where plates are colliding or moving apart – for example, volcanoes, fold mountains, ocean trenches, and ocean ridges.

            At times, the crust crumples gradually to form ranges of Fold Mountains such as the Himalayas. Andes (South America) and the Rockies (North America). Sometimes two plates will slide past each other – as in the San Andreas Fault, California, where the movement of the plates sometimes led to sudden jerks, causing the earthquakes common in the San Francisco-Los Angeles area. Most of the earthquake and volcano zones of the world are, in fact, found in regions where two plates meet or are moving apart.



            According to the theory of continental drift in geology, about 250 million years ago, the Earth consisted of a single large continent (Pangaea), which subsequently broke apart to form the continents known today. During that time, the rest of the Earth was covered by the Panthalassa Ocean. Later on Pangaea split into two land masses – Laurasia in the north and Gondwanaland in the south – which subsequently broke up into several continents. These then drifted slowly to their present positions.



            The existence of a single “supercontinent” was proposed by German meteorologist Alfred Wegener 1912. (There are reports that well known scientists made similar observations centuries ago.) Plate Tectonics was formulated by Canadian geophysicist John Tuzo Wilson and has gained widespread acceptance among earth scientists.


Are waves formed only near the sea shore?

Waves are formed everywhere on the sea or for that matter on any large water body. There are two physical mechanisms that control and maintain waves. For most waves, gravity is the restoring force that displaces the surface to be accelerated back towards the mean surface level. The kinetic energy gained by the fluid returning to its rest position causes it to overshoot, resulting in the oscillating wave motion.

            In the case of ripples, the restoring force is surface tension, wherein the surface acts like a stretched membrane. Waves on sea surface are generated by the action of the wind.



            The height of simple waves is the elevation difference between the top of a crest and the bottom of a trough. The height of wind waves increases with increasing wind speed and with increasing duration and fetch of the wind. Together with height, the dominant wavelength also increases. Finally, however, the waves reach a state of saturation, because they attain the maximum significant height to which the wind can raise them, even if duration and fetch are unlimited.



            After becoming swell, the waves may travel thousands of kilometers, particularly if the swell is from the great storms. In travelling, the swell waves gradually become lower; energy is lost by internal friction, air resistance and by energy dissipation because of divergence of the directions of propagation.



            When waves run into shallow water, their speed of propagation, height and wavelength decrease. In the final stage, the shape of the wave’s changes, and the crests become narrower and steeper until, finally, the waves become breakers (surf). Generally, this occurs where the depth is 1.3 times the wave height.


Where does sand come from? Has any thought been given to manufacturing it?


            Particles of sand, sometimes sorted by water transport into deposits of remarkably uniform size, are continuously being firmed, often from the bedrock of earth, by weathering and erosion by chemical and physical forces.



            The physical forces include water, wind and ice, in the form of the plant grindstones of glaciers.



            Sand particles may be glued together along with other minerals to form new sedimentary rocks, like the familiar sandstone, and sedimentary rocks may in turn by weathered into new sand.



            Quartz (a compound of the elements silicon and oxygen) is a very common component of primary rocks and is resistant to destruction by either mechanical or chemical means.



            It is not surprising that it makes up the biggest share of both sand and the larger than the very fine particles of clay and silt and smaller than gravel and pebbles.



            One widely used scale, the Wentworth Udden scale, puts the size of sand particles at approximately 0.0025 inches to 0.08 inches.



            The machinery earth provides for turning out such small hard particles if far cheaper to operate than any commercial equipment that could do the same job.



            Though there is a dwindling supply of mined sand on the continents because of restrictions on land use, there is a very large potential supply of offshore sand in the shallow shelf seas, presumably the results of cons of both the ocean’s undertow, chewing on the continents, and water and wind transport, carrying sand from inland.



 


Why is lava flowing out of a volcano hot?

 Magma is predominantly a molten silicate saturated with gases that are dissolved in it. It has a marked quantity of easily voltiling compounds ( O vapour, C , HF, HCI, etc).

            Owing to the high pressure existing in deeper part of the earth where volatile compounds are in a dissolved state within magma, diminishing its viscosity and increasing the degree of its mobility and chemical activity.



            Formation of magmatic sources under the earth is in general a continuous process. They are accumulated in the upper part of the asthenosphere (33-140 km deep from the surface of the earth) which then ascends into the upper levels of the earth’s crust.



            The movement of the magma towards the earth surface is conditioned by hydrostatic pressure along with considerable increase in the volume, which accompanies the transition of solid rocks into the molten state.



            Some magma melts penetrate and break through the horizons of earth surface and some invasive magma on its way to earth surface and solidifies at certain depth within the earth.



            Volcanism unites all the processes connected with the outflow on the earth’s surface. The volatile components, which, in the deeper regions owing to high pressure and temperature remains in the magma in dissolved state, are released it on the way to the earth’s surface. The products of volcanic eruptions include liquid, solid and gaseous materials (varitia).



            Liquid products of volcanic eruptions are represented by lava. And are classified as acid, medium, basic (or) ultra basic depending upon its chemical composition especially  (silica) content.



            Lavas of ultra basic or basic are poor in silica and rich in Ferro-magnesium compounds with temperature existing at the surface at the time of outflow being C and characterized by low viscosity and high mobility. So they easily move and spread themselves over a considerable distances and form sheets and streams of undulating surface. Thus the lava flowing out of a volcano is hot.



            Acid and medium lavas rich in silica with surface temperature of C - C possess high degree of viscosity and little mobility and more for short distance and quickly solidify forming small streams and blocks.



            Solid particles also emerge during volcanic explosion as a result of an ejection into the atmosphere and dispersion of huge masses of lava as well as fragments of rocks.



            Depending on size they are classified as volcanic bombs, Lapilli, volcanic sand and volcanic ash. Volcanic ash is the main product of eruption. Gaseous products released are made up of water vapour (60-90 percent followed by S, , Co, , HCI,HF, etc.)


What is ball lightning?

            One of the most rare and mysterious forms of lightning is ball lightning. It is a ball of luminosity that usually occurs near the impact point of a flash and moves horizontally at a speed of a few centimeters per second. It can penetrate closed windows, is usually accompanied by a hissing sound and has a life time of several seconds. The colour is quiet variable and the ball often ends with an explosion-however, it is not usually destructive. Also called as globe lightning, it occurs at times of intense electrical activity in the atmosphere. These balls are said to be plasmas. (Plasma is a completely ionized state of mater, at high temperature, in which positive and negative Ions freely move about.). However, no theory has so far satisfactorily explained the behavior of a ball as scientists have not been able to reproduce it in the laboratory. Lightning ball is comparatively rare sight and so next time you see it, take a picture.



            Clouds are masses of tiny water droplets and ice crystals that float in the air. As such they do not have any colour. But some look white and some grey.



            Some change shape continuously as parts of the cloud evaporate when they come into contact with the warmer air.



            Clouds are classified mainly by their appearance dimension, shape, structure and texture. While stratus clouds are sheet-like, fair weather cumulus clouds consists of piled-up masses of dazzlingly white clouds. They are made of water droplets. Cirrus clouds are curly white made of ice crystals at higher altitudes. In these clouds, water droplets or ice crystals are loosely packed and so light can pass through them without much loss in intensity.



            Some of the clouds which cause rain are the stratus and stratocumulus clouds which are near-earth clouds. Stratocumulus clouds are not as thick as stratus clouds and so they have light and dark areas.



            Altrostratus clouds form smooth white or grey sheets across the sky. Sometimes these clouds are so thick that the Sun or the Moon cannot be seen through it. At times the difference in thickness may cause relatively light patches between dark parts but the surface of the clouds do not show any relief.



            Nimbostratus is low, amorphous and occurs at higher altitudes. These are dark, grey and uniform. Cumulonimbus is the main rain clouds which are black. This is because light cannot penetrate through them as they are deep and densely packed with water droplets, ice and snow particles.



            If we look from an aircraft, flying at high altitudes, these clouds will look dazzlingly white, as they reflect all the light falling on them. But for an observer on the ground the clouds may look black and be raining. Clouds are thus white and black at the same time!




Why does rain fall as drops and sheets?

   Many windblown drops can be forced together to form what Weather reporters call ‘sheeting rain’, but rain is always born as minuscule drops of condensed  water vapour explains ‘Clouds and Weather’ by John A. Day and Vincent J. Schaefer (Houghton Miffin Company), U.S. The formation of these droplets depends on the right amount of water vapour at the right pressure and temperature, but it also requires the presence of tiny solid particles of matter in the air on which the water vapour can gather and condense.

            These bits of dust and salt are called cloud condensation nuclei. Salt starts collecting vapour at about 80 percent relative humidity, while bits of clay begin to take on water molecules at 100 percent relative humidity.



            


How do we measure rainfall?

            Rainfall is measured in terms of the level or height to which water is collected or accumulated on a flat surface through rain. It is usually expressed in millimeters to the nearest whole number. Rather than measuring all the rainfall falling over a large areas, which is impractical, rainfall is measured at a number of points over the area. There are many instruments for measuring rainfall; the most commonly used is the rain gauge.



            Rain gauge consists of a funnel (5”-6”in diameter), a measuring tube (usually one tenth of the funnel in diameter to measure accurately even the trace amounts of rainfall) and the outer cylindrical cover with a base. The rainfall falling into the funnel is directed into the measuring tube which is calibrated accordingly.



            The excess water, if any, overflows the tube and is collected within the outer cover. This is measured subsequently. Based on the material by which the parts of a rain gauge are made, it may be fibre glass type or metal type. For continuous recording of rainfall, recording rain gauge is used where the rise of water level is automatically monitored continuously. Recording rain gauge may be with float type recorder or weighing type recorder.



            In float type recorder the vertical movement of the float (with the rise of water level) is recorded by a pen on a chart fixed on a rotating drum; whereas in the weighing type, the weight    of the receiver is recorded by an weight balance. The rain gauge must be placed at horizontally (at about 12” height from the ground) at a distance of twice the height of the nearest objects like trees, buildings etc.



            Rainfall occurring in any place is simply measured as the height of the rainwater on the land in that place provided it is not lost due to run-off, evaporation etc. and the land is flat. Measuring rain this way is however impossible. A rain gauge must be used.



            A simple rain gauge which any one can use to measure rain at his place consists of a funnel (3”to 4” in diameter) fitted into a bottle (about 1 litre capacity) to collect the rain water and a measuring cylinder. (An air-vent is to be provided to prevent accumulation of water in the funnel in case of heavy down pours.)



            The rain gauge is kept on the ground in the open without obstructions from buildings, trees, etc. if the rainfall, over a period of time is 1cm at a place where the rain gauge is kept, then the height of the rainwater collected would also be 1 cm only if the bottle is flat at the bottom and its area cross section is the same as the area of the opening of the funnel.



            Since this specification cannot be followed the volume of water so collected has to be measured (this will be constant for a given size of funnel irrespective of the size or shape of the bottle) to know the amount of rainfall. Suppose the area of the opening of the funnel is 80 cm2then for 1 cm of rainfall the volume of water would be 80 cm2 x 1 cm that is 80 cm3. This amounts to 8 cm3 of water for every mm of rain.



            Thus if the total volume of rain water (in cm3) collected, over a specified period, is divided by 8, we get rainfall in mm in that place over the given period. To get accurate rainfall data quickly by directly observing the water level, a modified form of the above described rain gauge is used in all meteorological observatories. In this, rain water is collected in a narrow graduated tube so that the height of rain water is increased several times for the same amount of rain.



            This facilitates accurate measurement of even low rainfall like 1 mm or less. If the area of fifth of the area of the opening of the funnel then for 1 mm rainfall the height of rain water in the tube would be 5mm. if the graduations and made accordingly, the water level in the narrow tube directly gives the rainfall.



            For measuring continuous rain (which lasts several days on many occasions) automatic rain gauges are in use. In one type, called weighing type, the rainwater as it falls is weighed and translated into a continuous record on a clock-chart. Thus gives not only the total rainfall but also the time of its occurrence and its intensity.