Equinox Explained: Why Earth’s Seasons Will Change on Sunday

by Sidhi.S.L.Nair(2016-2019)

Sidnair017@gmail.com

The seasons will change this Sunday (Sept. 22), with the Northern Hemisphere moving into autumn and the South emerging from winter into spring.

The celestial event that marks this transition is called an “equinox,” and it happens twice every year, around March 21 and Sept. 21. Just what is an equinox, and why does it occur?

The Earth moves in two different ways. First, the planet spins on its polar axis — a line through the north and south poles — once every 24 hours, causing the alternation of day and night. Secondly, it moves in its orbit around the sun once every 365.25 days, causing the annual cycle of seasons. The equinox occurs when these two motions intersect.

Because the Earth is so big, its mass has an enormously powerful gyroscopic effect. For this reason, its poles always point in the same direction, although a major earthquake can cause tiny wobbles in this axis. Most importantly, the Earth’s motion around the sun has absolutely no effect on the direction the poles are pointing, which has very important consequences for Earth Seasons.

Astronomers mark the positions of objects in the sky relative to the Earth’s poles of rotation (those are the red lines you see in the picture). The most important line is the celestial equator, which divides the sky into the Northern and Southern Hemispheres.

The Earth’s pole of rotation is tilted 23.4 degrees relative to the plane of its orbit. This tilt is always toward the same point in the sky, called the celestial pole, no matter where in its orbit around the sun the Earth happens to be.

This tilt makes it appear to observers on Earth’s surface that the sun is moving across the sky at an angle to the celestial equator. This is marked by the green line in the image, called the “ecliptic” because eclipses happen along this line.

Twice a year, the sun crosses the celestial equator, moving from the Northern Hemisphere to the Southern Hemisphere, or vice versa. These two crossings are very important for the inhabitants of Earth, because they mark the change in the direction the sun’s rays fall on Earth.

Specifically, on Sunday, the sun will move from the Northern Hemisphere to the Southern Hemisphere. It will pass overhead everywhere along the Earth’s equator on that date, and the sun will rise exactly in the east and set exactly in the west. Day and night will also be of roughly equal length. (“Equinox” is derived from the Latin for “equal night.”)

After Sunday, the sun will shine more on the southern half of our planet and less on the northern half. Summer will be over in the Northern Hemisphere, and fall will have arrived. Winter will be over in the south, and spring will begin.

The sun will continue on its path southward for the next three months, reaching its southernmost point on Dec. 21, the date of the “solstice.” In the Northern Hemisphere, the days will become shorter, the nights longer, and the temperatures colder during this three-month trek, all as a result of the sun’s being south of the celestial equator.

 

It’s always important to remember that this is part of a cycle, and that after Dec. 21 the sun will start moving northward again, and spring will be on its way.

 

NASA tracks the rain behind Kerala floods

The National Aeronautics and Space Administration (NASA) has released a video created using satellite data that provide an estimate of the intense rainfall over India in the past week and show the spread of the resulting severe flooding in Kerala and parts of Karnataka.

Rainfall accumulations from August 13 to 20 show two bands of heavy rain across India, NASA said in a statement on Wednesday.

The first band appears much broader and extends across the northern part of the peninsula with weekly rainfall totals ranging from over 5 inches towards the western half of the peninsula to as much as 14 inches over parts of the eastern half towards the Bay of Bengal. The first band is associated with the general monsoon circulation.

 

The second band appears more concentrated and intense and is closely aligned with the southwest coast of India and the Western Ghats where onshore flow was enhanced by an area of low pressure embedded within the general monsoon. Weekly rainfall totals in this band are generally over 10 inches with embedded areas exceeding 16 inches. The maximum estimated value from the data in this band is 18.5 inches, NASA said.

Another contributing factor to the heavy rain along the southwest coast of India is the Western Ghats. The Western Ghats, with many peaks over 2,000 meters, is well positioned to enhance rainfall along the west coast of India as they intercept the moisture-laden air being drawn in off the warm waters of the northern Indian Ocean and the Arabian Sea as part of the southwest monsoon circulation.

The Integrated Multi-satellite Retrievals for GPM is used to estimate precipitation from a combination of passive microwave sensors, including microwave sensor and infrared data. The data are generated every half an hour, thereby allowing scientists to track rainfall across the globe almost in real time. GPM is the Global Precipitation Measurement mission core satellite. GPM is a joint mission between NASA and the Japan Aerospace Agency, JAXA.

Electric signals in human body

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

In reality very small electrical signals are running through our bodies that control everything we do. We know that everything is made up of Atoms and atoms contain neutron, protons and electrons. Neutron carries no charge, protons have positive charge and electrons have a negative charge. All these charged particles cancel each other effect and atom as a whole becomes a neutral particle. If this balance is disturbed an atom become either a positive or negative charged. This flow of charged particles is called electricity. As our body is composed of different atoms this means we can actually generate electricity from our body.

Our nervous system is continuously sending “Electrical signals” to brain. It means a very small magnitude of electrical signals is carrying signal to different parts of the body. An electrical charge is jumping from one cell to the next until it reaches its destination. These are electrical signal that tell our heart to speed up when we are in danger. But our heart pulse isn’t the only thing that relies on electrical impulses; almost all of our cells are capable of generating electricity.

Human Voltage

The phenomenon of electrical signals in human body is often referred to as sodium-potassium gate. In neutral condition our cells have more potassium ions inside than sodium ions. In neutral state the positive charge on sodium ion and negative charge on potassium ion cancels each other’s effect and no electrical signal is generated in neutral state.

When there is a need to send a message from one point to another the gate of the cell membrane open ups and sodium and potassium ions move freely in and out of the cell. This movement of positive and negative charges produces a switching in the form of 0 and 1 which ultimately results in an electrical pulse. This pulse triggers the gate of next cell to open and create another charge which travels all across the human body. That is how an electrical impulse moves from a nerve in your stubbed toe to your brain that senses pain.
These electrical signal are controlling our body and any breakdown in body’s electrical system is a real problem. That is why when you get an electric shock it interrupts the normal operations of your system it can result in heart palpitation (an extra heartbeat) or a lack of blood flow to the heart.
More electrical impulses are generated in one day by a single human brain than by all the phones in the world.

Boyle’s law in respiration

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

Just below the lungs is a muscle called the diaphragm. When a person breathes in, the lungs get air in it (or expands) . The lungs on expansion moves the diaphragm down. The diaphragm , which is a dome shaped muscle becomes more “flattened” . When the lung volume increases, the pressure in the lungs decreases (Boyle’s law). Since air always moves from areas of high pressure to areas of lower pressure, air will now be drawn into the lungs because the air pressure outside the body is higher than the pressure in the lungs.

The opposite process happens when a person breathes out. When person breathes out the diaphragm moves upwards and causes the volume of the lungs to decrease, the air inside lungs takes up lesser volume or has now higher pressure. The pressure in the lungs will increase, and the air that was in the lungs will be forced out towards the lower air pressure outside the body.

 Laplace’s law in respiration

The alveoli are all connected with each other via the alveolar ducts . When considering two differently sized alveoli that are connected to each other, we can see that the pressure in the alveoli can be described with
Laplace’s law:
P = 2 × T / r where T = wall tension, and r = radius.

The wall thickness can be neglected in this case, since it is the same with all the alveoli. Also, the surface tension ensures that the wall tension of all alveoli is equal. This brings us to the conclusion that the pressure in the smaller alveolus is greater than the one in the larger alveolus. Consequently, the gas from the smaller alveolus will be emptied into the larger alveolus in order to compensate pressure. The smaller alveolus collapses. If this happens in the entire lung, it is called atelectasis.

CDs AND DVDs

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

A compact disc or CD is a form of digital media. It is an optical device which can be encoded with digital data. When you examine a CD you can tell it is mainly plastic. In fact, a CD is almost pure polycarbonate plastic. There is a spiral track molded into the top of the plastic.
The surface of a CD is reflective because the disc is coated with a thin layer of aluminum or sometimes gold. The shiny metal layer reflects the laser that is used to read or write to the device. A layer of lacquer is spin-coated onto the CD to protect the metal. A label may be screen-printed or offset-printed onto the lacquer. Data is encoded by forming pits in the spiral track of the polycarbonate (though the pits appear as ridges from the perspective of the laser). A space between pits is called a
land . A change from a pit to a land or a land to a pit is a “1” in binary data, while no-change is a “0”.

Scratches Are Worse on One Side than the Other
Pits are closer to the label side of a CD, so a scratch or other damage on the label side is more likely to result in an error than one occurring on the clear side of the disc. A scratch on the clear side of the disc often can be repaired by polishing the disc or filling the scratch with a material with a similar refractive index.
Most of a CD is composed of a plastic called polycarbonate . The bottom layer is a polycarbonate layer where data is encoded by using tiny bumps on the surface. Above this layer is a reflective layer, which is typically made of aluminum (gold is also used, although quite rarely).
Above the reflective layer is a protective layer of lacquer and plastic, which shields the layers below it. The artwork or label is printed on the lacquer layer (i.e., on top of the CD) via offset printing or screen printing.
CDs store information digitally, i.e., with the help of millions of 1s and 0s. Data on a CD is encoded with the help of a laser beam that etches tiny indentations (or bumps, if you will) on its surface. A bump, in CD terminology, is known as a
pit, and represents the number 0. Similarly, the lack of a bump (known as a land ) represents the number 1. Hence, a laser beam can encode the required data into a compact disc by using pits and lands (0 and 1, respectively).
Now that you know how a CD is encoded with data, let’s take a look at how a CD player actually reads that stored data.

How does a CD player work?

There are two main components inside a CD player that help read a CD: a tiny laser beam (known as a semiconductor diode laser) and an electronic light detector (basically, a tiny photoelectric cell). When you switch on the CD player, an electric motor inside the player makes the CD rotate at a very high speed (the outer edge rotates at 200 RPM , while the inner edge spins at 500 RPM).

SONIC BOOM

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound . Sonic booms generate significant amounts of sound energy, sounding much like an explosion to the human ear.
Sound is a series of compression waves. When an object makes a sound, it vibrates a little, compressing the air around it. Those compressions moves outwards in all directions, and when they hit an ear, they are interpreted as sound.
If the object making a sound is standing still, the compressions move out with an even space between each one. If the object is moving, it adds – or subtracts – its own speed to the speed of the compression waves.
Since sound, in air, can only move at around 700 miles per hour, but objects can be pushed faster than that, the compression waves get pushed closer and closer together. When an object breaks the sound barrier it creates compressions faster than the compressions themselves can move away from it. The compression waves basically just pile up on top of each other, and then move outwards in all directions from the object. When they hit your ear, you hear a sonic boom, a ten-car-pile-up of sound

Example

The first example that springs to anyone’s mind when they think about sonic booms is fighter jets. When a jet breaks the sound barrier, a sonic boom trails behind it.
When an airplane travels through the air, it produces sound waves . If the plane is traveling slower than the
speed of sound (the speed of sound varies, but 700 mph is typical through air), then sound waves can propagate ahead of the plane. If the plane breaks the sound barrier and flies faster than the speed of sound, it produces a sonic boom when it flies past. The boom is the “wake” of the plane’s sound waves. All of the sound waves that would have normally propagated ahead of the plane are combined together so at first you hear nothing, and then you hear the boom they create.
It is just like being on the shore of a smooth lake when a boat speeds past. There is no disturbance in the water as the boat comes by, but eventually a large wave from the wake rolls onto shore. When a plane flies past at supersonic speeds the exact same thing happens, but instead of the large wake wave, you get a sonic boom.

Cause

When an aircraft passes through the air it creates a series of pressure waves in front of it and behind it, similar to the bow and stern waves created by a boat. These waves travel at the speed of sound and, as the speed of the object increases, the waves are forced together, or compressed, because they cannot get out of the way of each other. Eventually they merge into a single shock wave, which travels at the speed of sound, a critical speed known as Mach 1 , and is approximately 1,235 km/h (767 mph) at sea level and 20 °C (68 °F).
In smooth flight, the shock wave starts at the nose of the aircraft and ends at the tail. Because the different radial directions around the aircraft’s direction of travel are equivalent (given the “smooth flight” condition), the shock wave forms a Mach cone, similar to a vapour cone , with the aircraft at its tip. There is a rise in pressure at the nose, decreasing steadily to a negative pressure at the tail, followed by a sudden return to normal pressure after the object passes. This ” overpressure profile” is known as an N-wave because of its shape. The “boom” is experienced when there is a sudden change in pressure; therefore, an N-wave causes two booms – one when the initial pressure-rise reaches an observer, and another when the pressure returns to normal. This leads to a distinctive “double boom” from a supersonic aircraft. When the aircraft is maneuvering, the pressure distribution changes into different forms, with a characteristic U-wave shape.
Since the boom is being generated continually as long as the aircraft is supersonic, it fills out a narrow path on the ground following the aircraft’s flight path, a bit like an unrolling red carpet , and hence known as the boom carpet . Its width depends on the altitude of the aircraft.

Miniature sonic booms

The ‘crack’ of a bullwhip is also a sonic boom.
When someone uses a whip, they bring their arm up and then down quickly. This creates a wave, and that wave travels down the length of the whip. Although Catwoman wields them easily, bullwhips are heavy objects. It takes a lot of force to make the solid handle and heavy base of the lash move fast. The end of the whip is tapered and small. Since only a little energy is lost as the wave travels down the whip, a massive amount of momentum is channeled into a very small amount of leather. The makes the whip move faster and faster the more slender the whip becomes – sort of the way a river moves faster when the bed around it narrows. The result of this concentration is the tip of whip moves incredibly fast – fast enough to break the sound barrier.The end of the whip, known as the “cracker” , moves faster than the speed of sound, thus creating a sonic boom.  The whip is probably the first human invention to break the sound

The crack of a supersonic bullet passing overhead is also an example of a sonic boom in miniature.

Is it dangerous?

The strongest sonic boom ever recorded was 7,000 Pa (144 psf) and it did not cause injury to the researchers who were exposed to it. The boom was produced by an F-4 flying just above the speed of sound at an altitude of 100 feet (30 m). In recent tests, the maximum boom measured during more realistic flight conditions was 1,010 Pa (21 psf). There is a probability that some damage — shattered glass, for example — will result from a sonic boom. Buildings in good condition should suffer no damage by pressures of 530 Pa (11 psf) or less. And, typically, community exposure to sonic boom is below 100 Pa (2 psf). Ground motion resulting from sonic boom is rare and is well below structural damage thresholds accepted by the U.S. Bureau of Mines and other agencies.

IRIDESCENCE

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

Iridescence (also known as
goniochromism ) is the phenomenon of certain surfaces that appear to
gradually change colour as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles , butterfly wings and sea shells , as well as certain minerals. It is often created by
structural coloration (microstructures that interfere with light).
When light encounters boundaries between media that differ in refractive index, structural coloration can be produced by interference, diffraction or scattering. Both interference and diffraction can produce iridescent colours that change in appearance with viewing geometry, and are characterized by single or multiple reflectance maxima. Interference colours are produced when light interacts at boundaries of media with different refractive indices, where, depending on the dimensions of the media, some wavelengths constructively interfere to produce brilliant colours, while the remaining wavelengths destructively interfere . Interference-based colours can be produced by optical materials arranged in simple thin films or in multilayer reflectors. Diffraction gratings are reflective surfaces with regularly ordered parallel grooves or depressions that disperse different wavelengths of light in different directions, which, in turn, depends on the periodicity of the grating and its relation with incident wavelengths . Colour-producing nanostructures that are arranged in a crystalline pattern can also produce iridescence through diffraction following Bragg’s law . Diffraction and interference mechanisms can be combined to produce complex optical effects, as in the scales of some butterfly wings.

Some forms of scattering produce non-iridescent structural colours that tend to reflect maximally at shorter wavelengths ranging from ultraviolet to turquoise, although there are examples of long-wavelength structural colours produced by scattering . Non-iridescent structural colours in animals were long thought to be produced by incoherent scattering mechanisms such as Rayleigh scattering and Tyndall scattering . However, recent work by Prum and colleagues suggests that many, if not most, non-iridescent structural colours in animals are produced by the constructive interference of light . Thus, although iridescent and non-iridescent structural colours were assumed to involve fundamentally different mechanisms, it is becoming increasingly clear that both types of colour can result from coherent scattering, and that the main difference between them results from differences in the organization of their colour-producing nanostructures . Because non-iridescent structural colours are produced by quasi-ordered arrays instead of layered or crystalline structures, they tend to be less saturated, more diffuse and unaffected by viewing geometry. Nevertheless, it is sometimes difficult to distinguish between iridescent and non-iridescent colours, since structural colours often involve multiple scales of organization . It should also be noted that incoherent scattering can produce whiteness by scattering all visible wavelengths. For the purposes of this review, we interpret iridescence in its broadest sense, meaning colours that change in hue or intensity with viewing geometry.

UNIQUE FEATURES OF IRIDESCENT VISUAL SIGNALS

1. Directionality

Iridescent colours are by definition highly directional. Changes in viewing geometry can dramatically alter the appearance of iridescent colours, producing considerable changes in hue, intensity or both

2. Maximizing conspicuousness

Another unique feature of iridescent colours is that, depending on the underlying mechanism and viewing geometry, they can be exceptionally bright and saturated to a degree that is not usually achieved by pigment-based colours

3. Short-wavelength colours

Another important feature of iridescent signals, as well as other structural colours, is that they provide animals with the ability to produce colours reflecting maximally or secondarily at short wavelengths ranging from blue to ultraviolet.

4. Environmental variation

Another feature that sets iridescent colours apart from pigment-based colours is that their hue, saturation and brightness are directly dependent on the dimensions and refractive indices of the colour-producing nanostructures. Nanometre-scale differences in either of these characteristics can cause dramatic variation in colour both across species .

Iridescence in Butterfly Wings

When light hits the different layers of a butterfly wing, it is reflected numerous times. The combination of all these reflections causes the intense colours of many species.