How Can We See Black Holes ?

How Can We See Black Holes?  

Can we see a Black holes..? if you have this question in your mind than here is answer for you.

 

Though we cannot "see" a black hole itself (since not even light can escape the hole's gravitational field), we may see the hole's effects on nearby matter. For example, if gas from a nearby star were sucked towards the black hole, the intense gravitation al energy would heat the gas to millions of degrees. The resulting X-ray emissions could point to the presence of the black hole.

Or, if a massive black hole were surrounded by large amounts of orbiting material -- gas, dust, even stars -- their rapid motion close to the hole could be observable via shifts in the energy of the radiation they emit. Evidence along these lines is mount ing, suggesting that black holes may not be that rare in the universe.

However, such evidence remains indirect and therefore inconclusive. To confirm that black holes actually exist, we'll need to be able to observe the gravitational waves they produce as they form or interact.

If scientists could build gravitational wave detectors of sufficient sensitivity, they should be able to measure the vibrations in spacetime generated by black holes as they form from a collapsing star, when they ingest large amoun ts of matter, or if they interact, even collide with a second black hole or another massive object, such as a neutron star. Certain patterns of gravitational waves emitted would reveal the "smoking gun."

So far, the wavelike disturbances in spacetime have eluded detection. In a relativistic universe, there should be no shortage of places in which to hunt for black holes. Much larger and more sensitive detectors are now under construction. With luck, soon gravitation scientists may be shouting "Eureka!"

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10 Mind-Blowing Facts About Black Holes

10 Mind-Blowing Facts About Black Holes

 

Here are 10 interesting facts about black holes

1. It was John Mitchell who actually first proposed the idea of ‘dark stars’ or object. Later, in 20th century the term ‘black hole’ was coined.

2. Black holes are actually leftovers of former stars and are so dense that nothing can flee from their dominant gravitational energy. 

3. If the formation of a black hole has taken place, it can continue to grow by absorbing additional matter.

4. Generally the life cycle of most of the stars end up being a white dwarf or a neutron star, but, black holes are considered to be the last evolutionary stage in the lifetime of a star.

5. There are mainly three types of black holes namely stellar, super massive and miniature black holes, depending on their mass.

6. Since black holes possess strong gravitational force which pulls all of the light into its center, they cannot be seen.

7. Black holes follow the laws of gravity and hence in order to affect the earth, the orbit of a black hole would have to be very close to the solar system, which is not likely.

8. Astronomers are confident that our own Milky Way galaxy has a super massive black hole at its center.

9.Black holes have to hold a massive amount of mass in an incredibly small space to have the required gravity to pull light in. For example, to make a black hole with the mass of Earth, the entire planet would need to be squeezed down to a space 9 millimeters across.

10.When anything (be it planets, suns, galaxies or particles of light) passes close to a black hole, they will be pulled in by its gravity. If something else acting on the object, like say a rocket, is stronger than the black hole's gravity, it can escape the pull.

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Why does water freeze from the top to the bottom..?

Why does water freeze from the top to the bottom..??

The answer lies in a very peculiar property of water.  As you guessed, the density of water of water increases as the temperature is lowered, but below 4^oC this trend is reversed.   Here is a graph from The Physics Factbook. It shows the density of liquid water vs. temperature. The reason it can show liquid water below 0°C is that water can be supercooled, not actually turning to ice for a long time.




So what happens is the water that is just slightly above the freezing point rises to the top so the freezing process starts there.   This is the same reason why ice is at the top of a lake in the winter and not at the bottom.  This is beneficial to ice skaters as well as fish and other aquatic fauna.

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What Causes Optical Illusions?

What Causes Optical Illusions?

These yellow and blue blocks appear to move one after the other but actually not..!!

In simple terms, an optical illusion is caused by the structure of both the eye and brain and how they work together. Because of the anatomical make up of the eye and the complexity of the way images of transmitted from the eye to the brain, optical illusions are not as rare as one might consider.

The Anatomy of the Eye

The eye has two types of receptors on it (cones and rods) that pick up different bits of information on image. Around the retina, these cones and rods rest, waiting to pick up a stimuli and transfer it to the optic nerve. The optic nerve, in turn, transmits the information to the brain for processing.

Cone cells detect color and rod cells detect low-light contrasts. They work together to provide the necessary information to form an imag. However, at the edges of the retina, there are more rods and at the center of the retina, there are more cones. Because of this, based on how someone is looking at an image, they might see things differently. This is an optical illusion. For a better image, simply turning one's head and looking straight at something will provide the cones access and give a more detailed image.

Medical Syndromes Causing Optical Illusions

There is research to suggest that some optical illusions are caused by medical syndromes such as schizophrenia. Because of the nature of the disease, an individual sees something different than what is actually being seen. This is caused by the brain interpreting the information differently than it normally would be.

Effort on the Eye

Because it is more difficult to raise the eye than move the eye horizontally, the eye perceives that vertical distances are greater than horizontal distances. This creates depth in flat surfaces which can – especially when the eyes are fatigued – lead them to perceive something incorrectly and then pass that information onto the brain. The brain takes what information it has and processes it whether it is correct or not. Fatigue in the eyes is an exceptional cause of optical illusions because it takes a little longer for the eyes to focus more effectively.

 

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Voltage Transformer Basics

One of the main reasons that we use alternating AC voltages and currents in our homes and workplace’s is that AC supplies can be easily generated at a convenient voltage, transformed (hence the name transformer) into much higher voltages and then distributed around the country using a national grid of pylons and cables over very long distances.

The reason for transforming the voltage to a much higher level is that higher distribution voltages implies lower currents for the same power and therefore lower I²R losses along the networked grid of cables. These higher AC transmission voltages and currents can then be reduced to a much lower, safer and usable voltage level where it can be used to supply electrical equipment in our homes and workplaces, and all this is possible thanks to the basic Voltage Transformer.

A Typical Voltage Transformer

The Voltage Transformer can be thought of as an electrical component rather than an electronic component. A transformer basically is very simple static (or stationary) electro-magnetic passive electrical device that works on the principle of Faraday’s law of induction by converting electrical energy from one value to another.

The transformer does this by linking together two or more electrical circuits using a common oscillating magnetic circuit which is produced by the transformer itself. A transformer operates on the principals of “electromagnetic induction”, in the form of  Mutual Induction.

Mutual induction is the process by which a coil of wire magnetically induces a voltage into another coil located in close proximity to it. Then we can say that transformers work in the “magnetic domain”, and transformers get their name from the fact that they “transform” one voltage or current level into another.

Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of Electrical Power being transferred from one winding to another via the magnetic circuit.

A single phase voltage transformer basically consists of two electrical coils of wire, one called the “Primary Winding” and another called the “Secondary Winding”. For this tutorial we will define the “primary” side of the transformer as the side that usually takes power, and the “secondary” as the side that usually delivers power. In a single-phase voltage transformer the primary is usually the side with the higher voltage.

These two coils are not in electrical contact with each other but are instead wrapped together around a common closed magnetic iron circuit called the “core”. This soft iron core is not solid but made up of individual laminations connected together to help reduce the core’s losses.

The two coil windings are electrically isolated from each other but are magnetically linked through the common core allowing electrical power to be transferred from one coil to the other. When an electric current passed through the primary winding, a magnetic field is developed which induces a voltage into the secondary winding as shown.

Single Phase Voltage Transformer

In other words, for a transformer there is no direct electrical connection between the two coil windings, thereby giving it the name also of an Isolation Transformer. Generally, the primary winding of a transformer is connected to the input voltage supply and converts or transforms the electrical power into a magnetic field. While the job of the secondary winding is to convert this alternating magnetic field into electrical power producing the required output voltage as shown.

Transformer Construction (single-phase)

• Where:
•   V_P  -  is the Primary Voltage
•   V_S  -  is the Secondary Voltage
•   N_P  -  is the Number of Primary Windings
•   N_S  -  is the Number of Secondary Windings
•   Φ (phi)  -  is the Flux Linkage

Notice that the two coil windings are not electrically connected but are only linked magnetically. A single-phase transformer can operate to either increase or decrease the voltage applied to the primary winding. When a transformer is used to “increase” the voltage on its secondary winding with respect to the primary, it is called a Step-up transformer. When it is used to “decrease” the voltage on the secondary winding with respect to the primary it is called a Step-down transformer.

However, a third condition exists in which a transformer produces the same voltage on its secondary as is applied to its primary winding. In other words, its output is identical with respect to voltage, current and power transferred. This type of transformer is called an “Impedance Transformer” and is mainly used for impedance matching or the isolation of adjoining electrical circuits.

The difference in voltage between the primary and the secondary windings is achieved by changing the number of coil turns in the primary winding ( N_P ) compared to the number of coil turns on the secondary winding ( N_S ).

As the transformer is basically a linear device, a ratio now exists between the number of turns of the primary coil divided by the number of turns of the secondary coil. This ratio, called the ratio of transformation, more commonly known as a transformers “turns ratio”, ( TR ). This turns ratio value dictates the operation of the transformer and the corresponding voltage available on the secondary winding.

It is necessary to know the ratio of the number of turns of wire on the primary winding compared to the secondary winding. The turns ratio, which has no units, compares the two windings in order and is written with a colon, such as 3:1 (3-to-1). This means in this example, that if there are 3 volts on the primary winding there will be 1 volt on the secondary winding, 3 volts-to-1 volt. Then we can see that if the ratio between the number of turns changes the resulting voltages must also change by the same ratio, and this is true.

Transformers are all about “ratios”. The ratio of the primary to the secondary, the ratio of the input to the output, and the turns ratio of any given transformer will be the same as its voltage ratio. In other words for a transformer: “turns ratio = voltage ratio”. The actual number of turns of wire on any winding is generally not important, just the turns ratio and this relationship is given as:

A Transformers Turns Ratio

Assuming an ideal transformer and the phase angles:  Φ_P ≡ Φ_S

Note that the order of the numbers when expressing a transformers turns ratio value is very important as the turns ratio 3:1 expresses a very different transformer relationship and output voltage than one in which the turns ratio is given as: 1:3.

Transformer Basics Example No1

A voltage transformer has 1500 turns of wire on its primary coil and 500 turns of wire for its secondary coil. What will be the turns ratio (TR) of the transformer.

 

This ratio of 3:1 (3-to-1) simply means that there are three primary windings for every one secondary winding. As the ratio moves from a larger number on the left to a smaller number on the right, the primary voltage is therefore stepped down in value as shown.

Transformer Basics Example No2

If 240 volts rms is applied to the primary winding of the same transformer above, what will be the resulting secondary no load voltage.

 

Again confirming that the transformer is a “step-down transformer as the primary voltage is 240 volts and the corresponding secondary voltage is lower at 80 volts.

Then the main purpose of a transformer is to transform voltages at preset ratios and we can see that the primary winding has a set amount or number of windings (coils of wire) on it to suit the input voltage. If the secondary output voltage is to be the same value as the input voltage on the primary winding, then the same number of coil turns must be wound onto the secondary core as there are on the primary core giving an even turns ratio of 1:1 (1-to-1). In other words, one coil turn on the secondary to one coil turn on the primary.

If the output secondary voltage is to be greater or higher than the input voltage, (step-up transformer) then there must be more turns on the secondary giving a turns ratio of 1:N (1-to-N), where N represents the turns ratio number. Likewise, if it is required that the secondary voltage is to be lower or less than the primary, (step-down transformer) then the number of secondary windings must be less giving a turns ratio of N:1 (N-to-1).

Transformer Action

We have seen that the number of coil turns on the secondary winding compared to the primary winding, the turns ratio, affects the amount of voltage available from the secondary coil. But if the two windings are electrically isolated from each other, how is this secondary voltage produced?

We have said previously that a transformer basically consists of two coils wound around a common soft iron core. When an alternating voltage ( V_P ) is applied to the primary coil, current flows through the coil which in turn sets up a magnetic field around itself, called mutual inductance, by this current flow according to Faraday’s Law of electromagnetic induction. The strength of the magnetic field builds up as the current flow rises from zero to its maximum value which is given as dΦ/dt.

As the magnetic lines of force setup by this electromagnet expand outward from the coil the soft iron core forms a path for and concentrates the magnetic flux. This magnetic flux links the turns of both windings as it increases and decreases in opposite directions under the influence of the AC supply.

However, the strength of the magnetic field induced into the soft iron core depends upon the amount of current and the number of turns in the winding. When current is reduced, the magnetic field strength reduces.

When the magnetic lines of flux flow around the core, they pass through the turns of the secondary winding, causing a voltage to be induced into the secondary coil. The amount of voltage induced will be determined by: N.dΦ/dt (Faraday’s Law), where N is the number of coil turns. Also this induced voltage has the same frequency as the primary winding voltage.

Then we can see that the same voltage is induced in each coil turn of both windings because the same magnetic flux links the turns of both the windings together. As a result, the total induced voltage in each winding is directly proportional to the number of turns in that winding. However, the peak amplitude of the output voltage available on the secondary winding will be reduced if the magnetic losses of the core are high.

If we want the primary coil to produce a stronger magnetic field to overcome the cores magnetic losses, we can either send a larger current through the coil, or keep the same current flowing, and instead increase the number of coil turns ( N_P ) of the winding. The product of amperes times turns is called the “ampere-turns”, which determines the magnetising force of the coil.

So assuming we have a transformer with a single turn in the primary, and only one turn in the secondary. If one volt is applied to the one turn of the primary coil, assuming no losses, enough current must flow and enough magnetic flux generated to induce one volt in the single turn of the secondary. That is, each winding supports the same number of volts per turn.

As the magnetic flux varies sinusoidally, Φ = Φ_max sinωt, then the basic relationship between induced emf, ( E ) in a coil winding of N turns is given by:

emf = turns x rate of change

• Where:
•   ƒ  -  is the flux frequency in Hertz,  = ω/2π
•   Ν  -  is the number of coil windings.
•   Φ  -  is the flux density in webers

This is known as the Transformer EMF Equation. For the primary winding emf, N will be the number of primary turns, ( N_P ) and for the secondary winding emf, N will be the number of secondary turns, ( N_S ).

Also please note that as transformers require an alternating magnetic flux to operate correctly, transformers cannot therefore be used to transform or supply DC voltages or currents, since the magnetic field must be changing to induce a voltage in the secondary winding. In other words, Transformers DO NOT Operate on DC Voltages, ONLY AC.

If a transformers primary winding was connected to a DC supply, the inductive reactance of the winding would be zero as DC has no frequency, so the effective impedance of the winding will therefore be very low and equal only to the resistance of the copper used. Thus the winding will draw a very high current from the DC supply causing it to overheat and eventually burn out, because as we know I = V/R.

Transformer Basics Example No3

A single phase transformer has 480 turns on the primary winding and 90 turns on the secondary winding. The maximum value of the magnetic flux density is 1.1T when 2200 volts, 50Hz is applied to the transformer primary winding. Calculate:

a). The maximum flux in the core.

 

b). The cross-sectional area of the core.

 

c). The secondary induced emf.

Electrical Power in a Transformer

Another one of the transformer basics parameters is its power rating. Transformers are rated in Volt-amperes, ( VA ), or in larger units of Kilo Volt-amperes, ( kVA ). In an ideal transformer (ignoring any losses), the power available in the secondary winding will be the same as the power in the primary winding, they are constant wattage devices and do not change the power only the voltage to current ratio. Thus, in an ideal transformer the Power Ratio is equal to one (unity) as the voltage, V multiplied by the current, I will remain constant.

That is the electric power at one voltage/current level on the primary is “transformed” into electric power, at the same frequency, to the same voltage/current level on the secondary side. Although the transformer can step-up (or step-down) voltage, it cannot step-up power. Thus, when a transformer steps-up a voltage, it steps-down the current and vice-versa, so that the output power is always at the same value as the input power. Then we can say that primary power equals secondary power, ( P_P = P_S ).

Power in a Transformer

 

Where: Φ_P is the primary phase angle and Φ_S is the secondary phase angle.

Note that since power loss is proportional to the square of the current being transmitted, that is: I²R, increasing the voltage, let’s say doubling ( ×2 ) the voltage would decrease the current by the same amount, ( ÷2 ) while delivering the same amount of power to the load and therefore reducing losses by factor of 4. If the voltage was increased by a factor of 10, the current would decrease by the same factor reducing overall losses by factor of 100.

Transformer Basics – Efficiency

A transformer does not require any moving parts to transfer energy. This means that there are no friction or windage losses associated with other electrical machines. However, transformers do suffer from other types of losses called “copper losses” and “iron losses” but generally these are quite small.

Copper losses, also known as I²R loss is the electrical power which is lost in heat as a result of circulating the currents around the transformers copper windings, hence the name. Copper losses represents the greatest loss in the operation of a transformer. The actual watts of power lost can be determined (in each winding) by squaring the amperes and multiplying by the resistance in ohms of the winding (I²R).

Iron losses, also known as hysteresis is the lagging of the magnetic molecules within the core, in response to the alternating magnetic flux. This lagging (or out-of-phase) condition is due to the fact that it requires power to reverse magnetic molecules; they do not reverse until the flux has attained sufficient force to reverse them.

Their reversal results in friction, and friction produces heat in the core which is a form of power loss. Hysteresis within the transformer can be reduced by making the core from special steel alloys.

The intensity of power loss in a transformer determines its efficiency. The efficiency of a transformer is reflected in power (wattage) loss between the primary (input) and secondary (output) windings. Then the resulting efficiency of a transformer is equal to the ratio of the power output of the secondary winding, P_S to the power input of the primary winding, P_P and is therefore high.

An ideal transformer is 100% efficient because it delivers all the energy it receives. Real transformers on the other hand are not 100% efficient and at full load, the efficiency of a transformer is between 94% to 96% which is quiet good. For a transformer operating with a constant voltage and frequency with a very high capacity, the efficiency may be as high as 98%. The efficiency, η of a transformer is given as:

Transformer Efficiency

where: Input, Output and Losses are all expressed in units of power.

Generally when dealing with transformers, the primary watts are called “volt-amps”, VA to differentiate them from the secondary watts. Then the efficiency equation above can be modified to:

 

It is sometimes easier to remember the relationship between the transformers input, output and efficiency by using pictures. Here the three quantities of VA, W and η have been superimposed into a triangle giving power in watts at the top with volt-amps and efficiency at the bottom. This arrangement represents the actual position of each quantity in the efficiency formulas.

Transformer Efficiency Triangle

 

and transposing the above triangle quantities gives us the following combinations of the same equation:

 

Then, to find Watts (output) = VA x eff., or to find VA (input) = W/eff., or to find Efficiency, eff. = W/VA, etc.

Transformer Basics Summary

Then to summarise this transformer basics tutorial. A Transformer changes the voltage level (or current level) on its input winding to another value on its output winding using a magnetic field. A transformer consists of two electrically isolated coils and operates on Faraday’s principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.

Both the primary and secondary coil windings are wrapped around a common soft iron core made of individual laminations to reduce eddy current and power losses. The primary winding of the transformer is connected to the AC power source which must be sinusoidal in nature, while the secondary winding supplies power to the load.

We can represent the transformer in block diagram form as follows:

Basic Representation of the Transformer

 

The ratio of the transformers primary and secondary windings with respect to each other produces either a step-up voltage transformer or a step-down voltage transformer with the ratio between the number of primary turns to the number of secondary turns being called the “turns ratio” or “transformer ratio”.

If this ratio is less than unity, n < 1 then N_S is greater than N_P and the transformer is classed as a step-up transformer. If this ratio is greater than unity, n > 1, that is N_P is greater than N_S, the transformer is classed as a step-down transformer. Note that single phase step-down transformer can also be used as a step-up transformer simply by reversing its connections and making the low voltage winding its primary, and vice versa as long as the transformer is operated within its original VA design rating.

If the turns ratio is equal to unity, n = 1 then both the primary and secondary have the same number of windings, therefore the voltages and currents are the same for both windings.

This type of transformer is classed as an isolation transformer as both the primary and secondary windings of the transformer have the same number of volts per turn. The efficiency of a transformer is the ratio of the power it delivers to the load to the power it absorbs from the supply. In an ideal transformer there are no losses so no loss of power then Pin = Pout.

In the next tutorial to do with Transformer Basics, we will look at the physical Construction of a Transformer and see the different magnetic core types and laminations used to support the primary and secondary windings.

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What is the use of integration and differentiation?

What is the use of integration and differentiation?

Let us get into this with all interest. Yes integration is a reverse process of differentiation.
First let us put the question why do we need such a mathematical process called integration. Actually integration is nothing but the summing up of a lot, some million and million items.
Let me explain how.
Suppose you want to find the volume of a cone of radius r and height h.
Let the cone be seated such that its vertex get coincided with the origin and its height be along the x -axis.
In case of a cylinder the radius will be the same at all heights and so if you consider a small part both the sides of that part will have the same radius and so no problem in finding the volume.
But in the case of the cone, as we move away from the origin along x-axis the radius of the cone will be gradually increasing.
So as you consider a slice any where in the cone both the sides of the slice will not definitely have same radius. Is that ok?
Now calculus comes into play.
You choose a small slice in such a way that both the sides of the slice would have almost the same radius. It is possible only when you have a slice of negligible thickness. Such negligible thickness is denoted mathematically denoted as dx which means delta x tending to zero.
Once again note down the statement: delta x tending to zero. This means delta x is very so near to zero but not zero.
With such....... thickness, both sides of the slice would have the same radius.Let the slice of thickness dx be chosen at a distance x from the origin and let the radius of the slice be y at that position. Then the volume of our slice will be pi y^2 dx. Now imagine! Such slices, innumerable in number, can be got in the cone right moving from the origin and extending upto the total length (height) h of the cone. So we must collect all such slices and add their volumes to get the actual or total volume of the cone.
So we integrate the term pi y^2 dx within the limits of x ie 0 to h.
Now it becomes more essential to replace y interms of x. How can we do this? By using similar triangle concept, the ratio of the corresponding sides will be the same. So y/x = r/h
From this we can easily have y as (r/h) x.
Now replacing y we get the expression to be integrated (usually named as integrand) as pi (r/h)^2 x^2 dx. The formula for integral of x^n dx is given as x^(n+1) /(n+1).
So following this we get the integral value as pi(r/h)^2 (x^3 /3).
Next important step is supplying limit of x.
First upper limit h. This would give a value of pi(r/h)^2 (h^3 /3)
With lower limit 0, the value would become 0
Now the difference between these two values will be the required volume of the cone.
That comes to be 1/3 pi r^2 h. (cancelling h^2)
So interesting! See how much helpful the technique of integration in finding the volume of the cone!
By differentiation, we chop things into finer and by integration we collect all such finer.
Hope you have got a gist of the tremendous usage of the branch of mathematics, named as calculus.

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Why is air invisible..?

Air is invisible because it is a gas, and gas particles generally allow light to pass through them because they are so spread apart. Gases expand to fill any container they are in, as they do not hold a shape; therefore, it is usually easy to see through them

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Explain why the moon has no atmosphere..?

Moon has no atmosphere because the value of acceleration due to gravity ‘g’ on the surface of moon is small. Therefore, the value of escape velocity on the surface of moon is small. The value of r.m.s. velocity of the molecules of different gases is much above the value of escape velocity on moon. That is why all the molecules of gases escaped and there is no atmosphere on moon.

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What is geostationary satellite?

What is geostationary satellite?

 

A geostationary satellite is an earth-orbiting satellite, placed at an altitude of approximately 35,800 kilometers (22,300 miles) directly over the equator, that revolves in the same direction the earth rotates (west to east). At this altitude, one orbit takes 24 hours, the same length of time as the earth requires to rotate once on its axis. The term geostationary comes from the fact that such a satellite appears nearly stationary in the sky as seen by a ground-based observer. BGAN, the new global mobile communications network, uses geostationary satellites.

A single geostationary satellite is on a line of sight with about 40 percent of the earth's surface. Three such satellites, each separated by 120 degrees of longitude, can provide coverage of the entire planet, with the exception of small circular regions centered at the north and south geographic poles. A geostationary satellite can be accessed using a directional antenna, usually a small dish, aimed at the spot in the sky where the satellite appears to hover. The principal advantage of this type of satellite is the fact that an earthbound directional antenna can be aimed and then left in position without further adjustment. Another advantage is the fact that because highly directional antennas can be used, interference from surface-based sources, and from other satellites, is minimized.

Geostationary satellites have two major limitations. First, because the orbital zone is an extremely narrow ring in the plane of the equator, the number of satellites that can be maintained in geostationary orbits without mutual conflict (or even collision) is limited. Second, the distance that an electromagnetic (EM) signal must travel to and from a geostationary satellite is a minimum of 71,600 kilometers or 44,600 miles. Thus, a latency of at least 240 milliseconds is introduced when an EM signal, traveling at 300,000 kilometers per second (186,000 miles per second), makes a round trip from the surface to the satellite and back.

There are two other, less serious, problems with geostationary satellites. First, the exact position of a geostationary satellite, relative to the surface, varies slightly over the course of each 24-hour period because of gravitational interaction among the satellite, the earth, the sun, the moon, and the non-terrestrial planets. As observed from the surface, the satellite wanders within a rectangular region in the sky called the box. The box is small, but it limits the sharpness of the directional pattern, and therefore the power gain, that earth-based antennas can be designed to have. Second, there is a dramatic increase in background EM noise when the satellite comes near the sun as observed from a receiving station on the surface, because the sun is a powerful source of EM energy. This effect, known as solar fade, is a problem only within a few days of the equinoxes in late March and late September. Even then, episodes last for only a few minutes and take place only once a day.

In recent years, low earth orbit (LEO) satellite systems have become popular. This type of system employs a fleet or swarm of satellites, each in a polar orbit at an altitude of a few hundred kilometers. Each revolution takes between 90 minutes and a few hours. Over the course of a day, such a satellite comes within range of every point on the earth's surface for a certain period of time. The satellites in a LEO swarm are strategically spaced so that, from any point on the surface, at least one satellite is always on a line of sight. The satellites thus act as moving repeaters in a global cellular network. A LEO satellite system allows the use of simple, non-directional antennas, offers reduced latency, and does not suffer from solar fade. These facts are touted as advantages of LEO systems over geostationary satellites.

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What is force?

In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate.

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What Is the Difference Between Mass and Weight?

Comparison of Mass and Weight

Mass is a property of matter. The mass of an object is the same everywhere,	Weight depends on the effect of gravity. Weight varies according to location.
Mass can never be zero.	Weight can be zero if no gravity acts upon an object, as in space.
Mass does not change according to location.	Weight increases or decreases with higher or lower gravity.
Mass is a scalar quantity. It has magnitude.	Weight is a vector quantity. It has magnitude and is directed toward the center of the Earth or other gravity well.
Mass may be measured using an ordinary balance.	Weight is measured using a spring balance.
Mass usually is measured in grams and kilograms.	Weight often is measured in newtons, a unit of force.

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Does a fully charged battery weight more than when it's empty?

Does a fully charged battery weight more than when it's empty?

Yes because of E= mc*2
When you test the electrolite in a lead acid battery,as the battery charges the sulphuric acid becomes denser which gives it more mass so it "weighs" more.

Try it at home weigh a flat car battery on some reasonably accurate scales then charge it up and weigh it again.All you have added is potential energy.

The speed of light is constant,the energy has increased(it will start your car) so the only thing that can change is the mass.

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Is the number 0 even or odd..?

Is the number 0 even or odd..? 

 

A number is even if it is divisible by 2 without a remainder. For Example 8 is even since 8 divided by 2 is 4, and 12 is even since 12 divided by 2 is 6, but 7 is not even since 7 divided by 2 is 3 with a remainder of 1. 

What about zero? Zero divided by 2 is zero with no remainder so zero is even. 

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What would happen if Earth stopped spinning ?

What would happen if Earth stopped spinning ..?? 

 

 As you probably know, the Earth is rotating on its axis. This gives us day and night. Of course it’s impossible, but what would happen if the Earth stopped spinning? Remember, this isn’t possible, it can’t happen, so don’t worry.

Everything would be launched in a ballistic trajectory sideways
The first thing to think about is the momentum of everything on the surface of the Earth. You’re held down by gravity and you’re whizzing through space at a rotational velocity of 1,674.4 km/h (at the equator). You can’t feel it because of momentum. Just like how you can’t feel that you’re moving in a car going down the highway. But you feel the effects when you stop, or get into an accident. And so, if the Earth suddenly stopped spinning, everything on the surface of the Earth at the equator would suddenly be moving at more than 1,600 km/hour sideways. The escape velocity of Earth is about 40,000 km/hour, so that isn’t enough to fly off into space; but it would cause some horrible damage as everything flew in a ballistic trajectory sideways. Imagine the oceans sloshing sideways at 1,600 km/hour.

The rotational velocity of the Earth decreases as you head away from the equator, towards the poles. So as you got further away from the equator, your speed would decrease. If you were standing right on the north or south pole, you’d barely even feel it.

A day would last 365 days
The next problem is that day and night wouldn’t work the same any more. Right now the Earth is rotating on its axis, returning the Sun to the same position every 24 hours. But if the Earth stopped spinning, it would then take 365 days for the Sun to move through the sky and return to the same position. Half of the Earth would be baked for half a year, while the other hemisphere was in darkness. It would get very hot on the sunny side, and very cold in the shadowed side. You can imagine how that would be devastating to plants and animals. We get a hint of this at the poles, where you can experience weeks of permanent night and then weeks of permanent day. But imagine 6 months of night, followed by 6 months of day.

What Would Happen if the Earth Stopped Spinning

The Earth would become a perfect sphere
This might seem minor compared to the other catastrophes, but the Earth would become an almost perfect sphere. The Earth is currently rotating on its axis, completing one turn approximately every 24 hours. This rotational velocity causes the Earth to bulge out around its equator, turning our planet into an oblate spheroid (a flattened ball). Without this spin, gravity would be able to pull the Earth into a nice perfect sphere. This sounds interesting and probably harmless, but it’s actually a *big* problem. Because of the Earth’s bulge in the middle, the oceans are held out at the equator by 8 km. On perfect sphere Earth, the world’s oceans would redistribute, flooding many regions of the planet with an immense volume of water. We’d end up with a single continent around the middle of the planet, with oceans surrounding the north and south poles.

The Earth would no longer be tilted
The Earth’s tilt is defined by how the planet is rotating compared to the Sun. This axis of rotation defines the Earth’s seasons. But without any rotation, the concept doesn’t make sense any more. There’s still a north pole of the planet, where the radiation from the Sun is at its lowest angle, and an equator, where the light hits most directly. But there would no longer be seasons.

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Interesting Facts About Earth

Interesting Facts About Earth

 

Earth is the place that each person calls home. It is home to over six billion people and around 8.7 million different species. While everyone lives on Earth, there are many interesting facts that people do not know about the planet. Earth is unique in our solar system as being the only known planet to support the multitudes of different life. Earth facts can reveal the true nature of the place life calls home.

The Earth is not a Perfect Circle

It was long thought that Earth was spherical in shape. After careful studies and measurements by scientists, it is now known that earth is more of an oval. If you look at the diameter from pole to pole, Earth is 7882.4 miles long. If you measure the diameter from the equator line, earth measures 7908.9 miles long. The reason for the difference is how the Earth spins. It spins on its axes, which goes through the poles, making some of its mass move away from the poles and to its outside center.

There are Few Craters on Earth

When Earth is compared to the Moon, it has less impact craters caused by space debris. The Moon is documented to have billions of craters, as can be seen by looking at it. The reason behind so few craters on the Earth is that Earth possesses an atmosphere, which creates fiction for anything coming into it. The friction caused by an object moving at hundreds of thousands of miles per second entering the Earth?s atmosphere causes the object to burn up before hitting the ground. The Moon has no atmosphere and cannot stop even the smallest meteor hitting its surface, which is why there are so many craters on the Moon.

The Earth's Atmosphere

The atmosphere around the Earth keeps the animals and creatures living upon its surface a great deal as far as the requirements of life goes. It weighs around five trillions tons altogether, which is calculated based on the atmospheric pressure it exudes on the surface. The pressure is around one kilogram per square centimeter. The atmosphere protects its inhabitants from harmful space objects like meteors by burning them up before impact as well as harmful light rays such as X-rays, ultraviolet light, infrared and gamma rays.

Gravity is not the Same Everywhere

v There is an area in Canada called Hudson Bay that has a lower gravitational force than other regions of the earth. Scientists believe that 25 to 45 percent of the gravitational flux is due to a giant glacier sheet that was in the area long ago causing the Earth's crust to subside somewhat. The rest of the reason behind the gravitational flux can be explained by down drag due to the magma in the Earth's mantle.

The place that all known living creatures live is a fascinating place. The Earth facts discussed in this article can give an idea of the type of place life call home. The most important thing that people of planet Earth can do is to look after Earth so that all future generations can experience the wonders that Earth holds.

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In the earth where the gravity of the earth becomes zero..?

In the earth where the gravity of the earth becomes zero..?

In a perfectly-shaped sphere, with a smooth surface, and composed of exactly the same substance with the same density throughout it, the force of gravity is zero at the exact center of the sphere. That does NOT mean that 'gravity becomes zero' at the center. It means that at the center, for every speck of mass pulling on you in any direction with any force, there's another speck of mass pulling you in exactly the opposite direction with exactly the same amount of force, so the whole thing adds up to zero. In the real Earth, we can't tell exactly where that point is, because the Earth is not a perfect sphere shape, It doesn't have a smooth surface, and we don't know every last little detail about the distribution of mass inside it.

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Can you have zero gravity conditions on Earth..?

 Can you have zero gravity conditions on Earth..?

Gravity will always be there, but you can set up an arrangement where you will appear to be weightless. Such an arrangement is in a plane that flies up and swoops down so that its path is a circle standing on edge. You will hang in the plane and appear to be weightless. What is actually happening is that for a few seconds the plane is falling at the same speed as you are so if you measured your weight on scales in the plane, you would appear to weigh zero.

Zero gravity is impossible on earth. Actually, zero gravity is impossible anywhere. Gravity acts through millions of light-years, holding galaxy groups together, so there's no way that you can eliminate gravity this close to a major mass like the earth.

However - you CAN have a situation that is mathematically and physically equivalent to zero gravity, and that is free fall. Jump on a trampoline, you'll spend a few fractions of a second in free fall, which is just like zero-G. NASA does it with the Vomit Comet, which is a modified KC-135 aircraft that flies in parabolic paths to give astronauts-in-training a free fall experience. 

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Some Amazing Facts Collection part 2

Some Amazing Facts Collection part 2

--------------------------------------------------------------
1.The diameter of a proton is approximately 0.000000000001 mm (1/25,000,000,000,000 in).
2.The lightning bolt is 3 times hotter than the Sun.

3.If an item moves very, very fast, it becomes smaller and heavier.
4.The bark of the redwood tree is fireproof.
5.The Atlantic Ocean grows at about the same rate as your fingernails.
6.Lightning strikes about 6,000 times per minute on our planet.
7.The sum of the digits of a number which is a multiple of 9 is always 9
8.The Earth revolves around the Sun at a speed of about 18.5 miles/sec (30 km/sec)
9. there is no atmosphere on moon
10.If an atom were the size of a stadium, its electrons would be as small as bees
Don't Forget To Like Comment And Share

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Which Came First, The Chicken Or The Egg?

Chickens, as a species, became chickens through a long, slow process of evolution. At some point, a chicken-like bird produced an offspring that, due to some mutation in its DNA, crossed the threshold from mere chicken likeness into chicken actuality. That is to say, a proto-chicken gave birth to a real-life official chicken. And since that real-life official chicken came out of its own egg, we can say that the egg came first.

Another way to look at the question would be to ask which came first in evolutionary history. Once again, the egg takes precedence. Many characteristics of the modern avian egg—namely an oblong, asymmetrical shape and a hardened shell—were in place before birds diverged from dinosaurs about 150 million years ago. "A lot of the traits that we see in bird eggs evolved prior to birds in theropod dinosaurs," says Darla Zelenitsky, of the University of Calgary.

Another key moment in the history of avian eggs occurred at least 150 million years before that, when a subset of four-limbed vertebrates evolved to produce amniotic eggs. The embryos within the eggs were surrounded by three fluid-filled membranes that provide nourishment, protection, and a way to breathe. The earliest amniotic eggs contained large amounts of yolk, says James R. Stewart, a reproductive physiologist at East Tennessee State University. "You still see that in birds, crocodilians, and snakes," he explains. Like other placental mammals, we humans lost our yolk somewhere along the line, but our eggs still come with a vestigial yolk sac.

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Why 0! is equal to 1 ..??

Why 0! is equal to 1 ..??

We Know ,

n! = n x (n-1)!

Dividing both sides by n , We get

n!/n = n x (n-1)!/n 

Or, n!/n = (n-1)!

Or, (n-1)! = n!/n

Now , Putting n=1 , We get

(1-1)! = 1!/1

i.e. 0! = 1 

  

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What would happen if you drilled a tunnel through the center of the Earth and jumped into it?

What would happen if you drilled a tunnel through the center of the Earth and jumped into it..?

Want to really get away from it all? The farthest you can travel from home (and still remain on Earth) is about 7,900 miles (12,700 kilometers) straight down, but you'll have to journey the long way round to get there: 12,450 miles (20,036 kilometers) over land and sea.

Why not take a shortcut, straight down? You can get there in about 42 minutes -- that's short enough for a long lunch, assuming you can avoid Mole Men, prehistoric reptiles and underworld denizens en route. Granted, most Americans would end up in the Indian Ocean, but Chileans could dine out on authentic Chinese, and Kiwis could tuck into Spanish tapas for tea [sources: NOVA; Shegelski].

Of course, you'd be in for a rough ride. First, you'd have to pass through 22-44 miles (35-70 kilometers) of continental crust (3-6 miles/5-10 kilometers on the ocean floor) followed by 1,800 miles (2,900 kilometers) of mantle. After that, you'd have to traverse a Mars-sized outer core of liquid iron churning as hot as the sun's surface (10,000 degrees F, or 5,500 degrees C), then a solid, moon-sized inner core, and, some studies suggest, a liquid innermost core [sources: Angier; Locke; NOVA].

For sake of argument (and survival) let's pretend the Earth is a cold, uniform, inert ball of rock. While we're at it, let's ignore air resistance.

At the Earth's surface, gravity pulls on us at 32 feet (9.8 meters) per second squared. That means that, for each second you fall, you speed up by 32 feet per second -- but only near Earth's surface. Gravity is a function of mass, and mass is a property of matter. On the surface, all of Earth's matter lies below your feet but, as you fall, more and more of it surrounds you, exerting its own gravity. These horizontal tugs counterbalance each other and cancel out, but the increasing proportion of mass above your head exerts a growing counterforce to the proportionately decreasing mass below, so your acceleration slows as you near the core. At the planet's center, your acceleration due to gravity is zero -- Earth's mass surrounds you, gravity cancels out and you are weightless [sources: Locke; Singh].

You're still moving at a heck of a clip, though, so don't expect to stop there. Halfway to the center, your speed hits 15,000 mph (24,000 kph); 21 minutes after jumping in, you blow past the center at 18,000 mph (29,000 kph). Another 21 minutes later, with gravity slowing you as you go, you reach the far side and stop briefly in midair. Unless someone catches you, you'll then head back the way you came and start all over again. In our idealized case, this will continue indefinitely, like a pendulum or a spring, in a process called harmonic motion

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Funniest Math/Science Questions and answers

Q. How can you drop a raw egg onto a concrete floor without cracking it?

A. Concrete floors are very hard to crack!



Q. If it took eight men ten hours to build a wall, how long would it take
four men to build it?

A. No time at all it is already built.



Q. If you had three apples and four oranges in one hand and four apples
and three oranges in the other hand, what would you have?

A. Very large hands. (Good one)



Q. How can you lift an elephant with one hand?

A. It is not a problem, since you will never find an elephant with
one hand.




Q. How can a man go eight days without sleep?

A. No Probs , He sleeps at night.



Q. If you throw a red stone into the blue sea what it will become?

A. It will Wet or Sink as simple as that.



Q. What looks like half apple ?

A: The other half.



Q. What can you never eat for breakfast ?

A: Dinner.



Q. What happened when wheel was invented ?

A: It caused a revolution.



Q. Bay of Bengal is in which state?

A: Liquid

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Math Puzzle Questions

1. What is come in place of question mark (?) in the following series?





(a) HS

(b) IT

(c) IS

(d) HT



Solution:

2. If A is substituted by 4, B by 3, C by 2, D by 4, E by 3, F by 2 and so on, then what will be total of the numerical values of the letters of the word SICK?

(a) 11

(b) 12

(c) 10

(d) 9



Solution:

Total value = 4 + 2 + 2 + 3 = 11.

Answer: (a)



3. Four of the following five are alike in a certain way and hence form a group. Which one does not belong to the group?

(a) 52

(b) 70

(c) 48

(d) 68



Solution:All the numbers are multiple of 4, except 70.

Answer: (b)



4. If U is denoted by 7, M by 2, I by 5, O by 1, K by 8 and J by 4, then what will be the numeric form of the word MOUJIK when written in the reverse order?

(a) 217458

(b) 845712

(c) 854712

(d) 857412



Solution:

217458 is the number.

Now reverse the number 854712

Answer: (c)



5. How many letters of the word FAINTS, will their order in the word and that when the letters are arranged in the alphabetical order, remain the same?

(a) Two

(b) One

(c) Three

(d) Nil



Solution:

When the letters are arranged in the alphabetical order, two remains the same.

Answer: (a)



6. In a certain code GARNISH is written as RGAINHS. How will GENIOUS be written in that code?

(a) NEGOISU

(b) NGEOISU

(c) NGESUOI

(d) NEGSUOI



Solution:

So now, GENIOUS be written as;

Answer: (b)



7. How many such pairs of letters are there in the word MISPLACE each of which has as many letters between its two letters in the word as there are between them in the English alphabet?

(a) One

(b) Nil

(c) Two

(d) Three



Solution:

Answer: (c)



8. In a certain code INKER is written as GLLGT and GLIDE is written as EJJFG. How will JINKS be written in that code?

(a) GFOMU

(b) HGMMU

(c) HGOGH

(d) HGOMU



Solution:

As,

And,

Similarly, JINKS be written as;

Answer: (d)



9. If ‘AND’ is written as ‘EQF’ and ‘THE’ as ‘XKG’ then how will ‘COM’ be written?

(a) HRO

(b) GQO

(c) GRO

(d) GRN



Solution:

As,

And,

Similarly, ‘COM’ be written as;

Answer: (c)



10. Four of the following five are alike in a certain way based on the positions of their elements in the English alphabet and hence form a group. Which one does not belong to the group?

(a) UQ

(b) KG

(c) SO

(d) QL



Solution:

QL

Answer: (d)

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