The Bending of Light in a Gravitational Field

Let us consider a ray of light that shines through a window in an elevator at rest, as shown in figure. The ray of light follows a straight line path and hits the opposite wall of the elevator at the point P.

Let us now repeat the experiment, but let the elevator accelerate upward very rapidly, as shown in figure. The ray of light enters the window as before, but before it can cross the room to the opposite wall the elevator is displaced upward because of the acceleration. Instead of the ray of light hitting the wall at the point P, it hits at some lower point Q because of the upward acceleration of the elevator.

To an observer in the elevator, the ray of light follows the parabolic path, as shown in figure. Thus, in the accelerated coordinate system of the elevator, light does not travel in a straight line, but instead follows a curved path. But by the principle of equivalence the accelerated elevator can be replaced by a gravitational field. Therefore light should be bent from a straight line path in the presence of a gravitational field.

The gravitational field of the earth is relatively small and the bending cannot be measured on earth. However, the gravitational field of the sun is much larger and Einstein predicted in 1916 that rays of light that pass close to the sun should be bent by the gravitational field of the sun.

Another way of considering this bending of light is to say that light has energy and energy can be equated to mass, thus the light-mass should be attracted to the sun. Finally, we can think of this bending of light in terms of the curvature of spacetime caused by the mass of the sun. Light follows the shortest path, called a geodesic, and is thus bent by the curvature of spacetime.

Regardless of which conceptual picture we pick, Einstein predicted that a ray of light should be deflected by the sun by the angle of 1.75 seconds of arc. In order to observe this deflection it was necessary to measure the angular deviation between two stars when they are far removed from the sun, and then measure the deflection again when they are close to the sun. Of course when they are close to the sun, there is too much light from the sun to be able to see the stars.

Hence, to test out Einstein’s prediction it was necessary to measure the separation during a total eclipse of the sun. Sir Arthur Eddington led an expedition to the west coast of Africa for the solar eclipse of May 29, 1919, and measured the deflection. On November 6, 1919, the confirmation of Einstein’s prediction of the bending of light was announced to the world.

More modern techniques used today measure radio waves from the two quasars, 3c273 and 3c279 in the constellation of Virgo.

A quasar is a quasi-stellar object, a star that emits very large quantities of radio waves. Because the sun is very dim in the emission of radio waves, radio astronomers do not have to wait for an eclipse to measure the angular separation but can measure it at any time.

On October 8, 1972, when the quasars were close to the sun, radio astronomers measured the angular separation between 3c273 and 3c279 in radio waves and found that the change in the angular separation caused by the bending of the radio waves around the sun was 1.73 seconds of arc, in agreement with the general theory of relativity.


TIME TRAVEL & WORMHOLES – myth or truth

At present, we are changing according to the time. Time not change according to us. But what if we change the time. Time travel An imaginary thought.

We don’t know if It will be future or past. It is like changing time’s direction to past or increasing time’s speed to future, but if it will be possible in the future, It may be travel to past.

According to relativity, Nothing can travel faster than light (3 × 10⁸m/sec.). At light speed, mass will be infinite (according to relativistic mass formula) . And the length of object will be zero (according to length contraction formula). But if we travel with the light speed, what can we see? Is there any color? Is there any boundary of anything? Only white light appears on moving with light speed. Everything is white.

At present, black holes are the best source to see the past. Where, light cannot even pass through. The body’s shape , space-time will be changed at light speed . 

Even if we travel with such a high-speed it will take 2000 years in reaching and coming back to Earth from a thousand light years away star(or any Terrestrial body in space). When you travel such a large distance, an atom, the smallest unit of matter also traveled to that distance, and it is amazing to imagine.


According to scientists, a wormhole is a cylindrical path between two heavy bodies in space. It is not from any science fiction movie. It is scientist’s thoughts. 

Wormhole forms by two giant bodies have very high gravity value like black holes. If a path is a thousand light years long, wormholes can make it a few million miles long. So, it may be a possibility to travel faster than light.

In 1835, Albert Einstein and Nathan Rosen called them Einstein-Rosen Bridge. Bridge that connects two, bodies that are light years far away from each others.

Worm holes are like tunnels in space connecting to distant bodies because space and time are flexible (according to Einstein). Through the wormholes we can cover very long distance in a very short period.


According to another theory we can travel with light speed. The theory proposed that, if we are stable and space can move. In this theory, a large heavy body contract the space with fast and alternately a negative mass, behind the large body, can expand that contracted space.

Negative mass is only a hypothetical Idea. It behaves just opposite of positive mass that we have.

Positive mass can contract the space while a negative mass can expand it. Due to this, we remain stable on a position and space can move.

If all this phenomena possible, we can cover large distance with speed of light by stay at a place without any change.

To be continue…

Hope u like it




Feathers, are important parts of a bird’s flying equipment’. A bird’s tail feathers are used for lifting, steering, and breaking, and these are perfectly symmetrical, to allow a balanced and smooth flight.

Along the sides of a bird’s feathers are barbs, which if separated, look like a fringe, or even like the threads that stick out from the edge of a piece of unstitched cloth. Since these barbs end in hooks, they hook on to one another efficiently, making a strong, but light flying wing.

There here are two sources of feather colour- pigments, and the physical structure of the feather. Many feathers are coloured by a combination of these features. Pigments are chemical compounds that absorb certain wavelengths of light while reflecting others. The colours you see are those reflected back. Feathers coloured by pigments, range from crow black to canary yellow, and cardinal red.

Many colours, such as blue, are a result of feather structure. When light hits these feathers, it hits microscopic structures on the feather that act as prisms to reflect a colour.
No blue pigment is known in birds. Shimmering iridescent colours such as those found in peacocks, are caused by special structures, air bubbles, or films on feather surfaces.

These modifications interfere with the bending and scattering of light to strengthen some wavelengths, and cancel out others.


Hydrophobic interactions

Some molecules just don’t play nicely with water. Because water is a polar molecule, it tends to stick to itself via hydrogen bonds. Other polar molecules also stick to water molecules and can mix right in, dissolv ing into the water. However, nonpolar molecules have evenly shared covalent bonds and lack the slight negative and positive charges of polar molecules. Because they’re uncharged, nonpolar molecules don’t mix well with water.

Nonpolar molecules are also called hydrophobic molecules because “hydro” means water and “phobic” means to fear.

When nonpolar molecules are placed in a watery environment, the polar mol ecules will all stick to each other and push the nonpolar molecules away. You can think of the scenario as if the polar molecules all belong to a clique that refuses to hang out with the nonpolar molecules. (The name of this clique, by the way, is the hydrophilic molecules.) Because the nonpolar molecules all get pushed together, they become associated with each other.

The interaction between nonpolar molecules is called a hydrophobic interaction.

You can easily demonstrate a hydrophobic interaction to yourself. Just go into your kitchen, put some water in a cup, and then add a little oil. Even if you stir the mixture vigorously to mix the oil into the water, as soon as you stop stirring, all the oil will gather together on top of the water.

The water molecules all stick to each other and push the oil molecules away. Hence the saying, “They get along like oil and water!”


How viruses get into cells

Viruses attach to cells when viral proteins successfully bind to receptors on the host cell. If the viral protein has the right shape, it will tuck into the cor responding shape on the host cell receptor. You can think of viral attachment as a virus having the right key to fit into the lock on the host cell.

After the virus is attached, it may force itself into the cell by digging a hole through a cell wall slip in by fusing its envelope with the membrane of the host cell, or trick the cell into bringing it inside.

The ability of a virus to infect a host cell depends on a match between pro teins on the surface of the virus and receptors on the surface of the host cell.

The type of cells a particular virus can infect is called the host range of the virus. Because viruses can infect only cells that they can attach to with their proteins, each virus has a very specific range of hosts it can infect. In other words, each virus can infect only the host cells for which it has keys.

Some viruses have a key that works in the lock on many types of cells. These viruses have a broad host range. For example, the rabies virus can infect humans and many other mammals. On the other hand, some viruses have a key that fits into the lock on only a few cells. These viruses have a narrow host range. The HIV virus, which infects only certain cells of the human immune system, is a good example of a virus with a very narrow host range.


The structure of viruses

The simplest viruses have just two components: a nucleic acid core and protein capsid. The nucleic acid core, which may be DNA or RNA, contains the instructions for taking over cells and making more virions, or viral par ticles. The nucleic acid is surrounded by the capsid, a protective protein coat. Each individual protein that makes up the capsid is called a capsomere.

All viruses have at least a capsid and a nucleic acid core. The core consists of one of four types of nucleic acid:

*Double-stranded DNA

*Single-stranded DNA

*Double-stranded RNA

*Single-stranded RNA

One difference between cells and viruses is that cells contain DNA and RNA. However, a single viral particle contains only DNA or RNA. Also, single stranded DNA and double-stranded RNA are commonly found in viruses, but not in cells.

In addition to the capsid and the core, some viruses have an outer membrane layer called an envelope. It’s no coincidence that the envelope of a virus is similar to the plasma membrane of a cell viruses that have envelopes steal them from their cellular victims as they leave the cell! Viral envelopes aren’t exactly the same as plasma membranes because they’ve been changed to suit the needs of the virus by the addition of viral proteins.

Once modified and adopted, the envelope helps the virus enter and exit from host cells. Viruses may also have proteins that stick out of the envelope or off the sur face of the capsid. These proteins, called spikes, help the virus attach to host cells.

Viruses come in three common shapes:

*Helical viruses have a capsid that forms a twisting helix around the nucleic acid core.

*Polyhedral viruses have a regular geometric shape. The most complex polyhedral viruses are icosahedrons with 20 faces.

*Complex viruses have separate patches of proteins, often forming unique structures or extensions on the virus.

Under the microscope, enveloped viruses appear irregular in shape. However, a helical or polyhedral capsid may be located underneath the envelope.



Food webs
Energy passes from one animate thing to a different within the sort of food. Food webs show however living things go after each other. At very cheap of a food cycle are plants, that build their own food, taking energy from the Sun. At the highest ar predators, that go after alternative animals.

Food chain
Food webs are created from totally different, many various, many alternative food chains that have different levels. In a very organic phenomenon, plants are referred to as producers as a result of they create their own food. Animals that eat plants are referred to as primary customers. Primary customers are ingested by alternative animals referred to as secondary customers, or predators. Once all living things die they become the food of organisms referred to as decomposers.

Food pyramid
As we have a tendency to go up a organic phenomenon, the number of food offered decreases. This is often as a result of living things use most of the energy within the food they eat respiration. A organic phenomenon shows however energy is lost at every level. close to the highest, there ar simply many predators, whereas at very cheap there are more producers.



The bones are the hard structure ,Which form the rigid framework the body.
Bone is a highly vascular mineralized connective tissue consisting of cell and dense intercellular organic matrix impregnated with organic salts. The organic material mainly consist of collagen fibers and form one third of the bone.
The inorganic material mainly consist of calcium phosphate and traces of other salts. It provides hardness and rigidity to the bone and makes it radiopaque in x-ray film.

 Bone give shape and support to the body ,and resist any forms of stress.
 These provide surface for the attachment of muscle ,tendons,ligaments.
 These serve as levers for muscular actions.
 Bone marrow manufactures blood cells.
 Bone store 97%of the body calcium and phosphorus.
 Bone marrow contains reticuloendothelial cells which are phagocytic in nature and take part in immune responses of the body.
 The skull ,vertebral column and thoracic cage protect brain , spinal cord and thoracic and some abdominal viscera ,respectively.
 some bones around the nose contain large cavities filled with air (paranasal air sinuses which affect the timber of the voice).


According to shape
According to the structure
According to the development


Depending on the size and shape. the bone are classified into 7 type.
• Long Bones
• Short Bones
• Flat Bones
• Irregular Bones
• Pneumatic Bones
• Sesamoid Bones
• Accessory Bones

Long bones

Long bone are those in which length exceeds the breadth and thickness.
The long bone are two types.
 Typical long bones
 Miniature/short long bone

Short bones

Short bones are small in size and usually cuboidal in shape , presenting six surfaces. These bones are found in wrist (carpal bone ) and foot (tarsal bone).

Flat bones

Flat bone are flat and shallow plate-like bone.
They form boundaries of certain body cavities. the example of the flat bone frontal, parietal ,occipital ,scapula, ribs, sternum.

Irregular bones

Irregular bone are highly irregular shape ,hip bone vertebrae bone forming base of skull.

Pneumatic bones

Pneumatic bone are a variety of irregular bone which contain air filled cavity. These bones are mainly located around the nasal cavity.
Example maxilla ,frontal ,sphenoid and ethmoid bones.

Sesamoid bones

These are bony nodules found embedded in the tendons or joint capsules.they have no periosteum and ossify after birth. Ex. Patella.

Accessory bones

These bones are not always present. These may occur as ununited epiphysis developed from extra centres of ossification. Ex. Sutural or wormain bones.


Microscopically the architecture of bone may be compact or cancellous.
Compact bone Compact bone is dense in texture like ivory ,but is extremely porous. It is best developed in the cortex of the long bone.
Cancellous bone The cancellous bone is a mesh work of bony consist of interconnecting road and plates of bone called trabeculae.


According to the process of the bone development. The bones are three type.
Membranous bones are developed by membranous ossification.
Cartilaginous bone are developed by endochondral ossification.
Membrano-cartilaginous bone developed by both membranous and endochondral ossification.

Parts of growing young long bone
 Epiphysis
 Diaphysis
 Metaphysis
 Epiphysis plate

Epiphysis these are ends of long bones which ossify from secondary centers.
Diaphysis It is the elongated part of bone between the metaphysis. It develops from primary ossification center.
Metaphysis the end of diaphysis toward the epiphyseal cartilage is called metaphysis.
Epiphysis plate Epiphysial plate separates epiphysis from metaphysis. Proliferation of the cells in this cartilaginous plate is responsible for lengthwise growth of a long bone.



There are many planetary systems like ours in the universe, with planets orbiting a host star. our planetary system is named the “solar” sytem because our sun is named Sol , after the latin word for sun, “solis”, and anything related to the sun we call “solar.”

Age 4.568 billion years

our solar system formed about 4.5 billion years ago from a dense cloud collapsed, possibly due to the shockwave of a nearby exploding star, called supernova. when this dust cloud collapsed. it formed a solar nebula – a spinning, swirling disk of material. As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars.

The solar system consists of the Sun, planets, dwarf planets, moons, and numerous smaller objects such as comets and asteroids. 194 moons, 3,583 comets and 796,289 asteroids have been found in the solar system. 99.86% of the solar system’s mass is found in the Sun.

The Sun is our nearest star. It is, as all stars are, a hot ball of gas made up mostly of Hydrogen. The Sun is so hot that most of the gas is actually plasma, the fourth state of matter. The sun is classified as a G-type main-sequence star, or G dwarf star, or more imprecisely, a yellow dwarf. The planets in order from the Sun based on their distance are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Approx distance between neptune (8th) planet and sun is 4.476 billion km.
It is 143.73 billion km from the Sun, thus giving the Solar System a diameter of 287.46 billion km approx.

Based on where the planets end, you could say it’s Neptune and the Kuiper Belt. If you measure by edge of the Sun’s magnetic fields, the end is the heliosphere. If you judge by the stopping point of Sun’s gravitational influence, the solar system would end at the Oort Cloud. The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars, that is occupied by a great many solid, irregularly shaped bodies, of many sizes but much smaller than planets, called asteroids or minor planets.
The asteroid belt formed from the primordial solar nebula as a group of planetesimals.
Planetesimals are the smaller precursors of the protoplanets. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other’s orbits and collide, gradually coalescing into the dominant planets.

The Kuiper belt, occasionally called the Edgeworth–Kuiper belt, is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger – 20 times as wide and 20–200 times
as massive. Like the asteroid belt, it consists mainly of small bodies or remnants from when the Solar System formed.
The Kuiper belt is home to three officially recognized dwarf planets: Pluto, Haumea and Make make. Kuiper belt contain comets, mostly ice comets with black colour. When the orbit of the comet brings it close to the Sun, the ice evaporates into space, leaving some of the fine dust sitting on the surface. The dust is fine like talcum powder because comets are too small to have
enough gravity to squeeze the dust together into larger particles. The surface is very black.

The sun sends out a constant flow of charged particles called the solar wind, which ultimately travels past all the planets to some three times the distance to Pluto before being impeded by the interstellar medium. This forms a giant bubble around the sun and its planets, known as the heliosphere.

The heliosphere is the vast, bubble-like region of space which surrounds and is
created by the Sun. In plasma physics terms, this is the cavity formed by the Sun in the
surrounding interstellar medium. The “bubble” of the heliosphere is continuously “inflated”
by plasma originating from the Sun, known as the solar wind.
The heliosphere acts as a shield that protects the planets from interstellar radiation.

The Oort Cloud lies far beyond most distant edges of the Kuiper Belt. While the planets of our solar system orbit in a flat plane, the Oort Cloud is believed to be a giant spherical shell surrounding the Sun, planets and Kuiper Belt. The outer limit of the Oort cloud defines the cosmographic boundary of the Solar System and the extent of the Sun’s Hill sphere. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way itself. The Oort Cloud is made up of icy pieces of space debris.
In short, gravity from the planets shoved many icy planetesimals away from the Sun, and gravity from the galaxy likely caused them to settle in the borderlands of the solar system, where the planets couldn’t perturb them anymore. And they became what we now call the Oort Cloud.
The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 au .
The outer limit of the Oort cloud defines the cosmographic boundary of the Solar System and
the extent of the Sun’s Hill sphere.



ENDOCRINOLOGY in short and if we get more information then we’ll update this post.



  1. Adrenaline hormone
  2. Cortisol hormone
  3. Steroid hormone

Adrenaline –

Action of the adrenalin include increasing the heart rate ,increasing blood pressure , expending the air passage of the lunge entering of the pupil in the eye.


         Increases the gluconeogenesis in the liver.

Inhibitory effect on insulin which stop transport of glucose into the cells

Cortisol has diurnal variation.

No diurnal change In cushings syndrome.


Steroid hormones play an important role in    –

Carbohydrate regulation (glucocorticoids)

Mineral balance (mineralocorticoide)

Reproductive function (gonadal steroids)

Steroid play a important role in inflammatory responses stress responses bone metabolism, cardiovascular fitness, behavior


A pink gland with two lobes located in the thoracic cavity posterior to the sternum.

It is large during the child hood and puberty but shrinks during adulthood.


         Its primary function is to stimulate the production of T Cells which are an important part of the immune system.

Thymosin also assists in the development of B Cells to plasma cell to produce antibodies.

 Over production of thymosin- Lymphocytosis


HORMONE     Insulin 


           Insulin is the only hormone that reduce blood glucose levels and it does this by activating the glucose transport mechanism and glucose utilizing metabolic pathway in different tissues of the body.


4) Testes

Hormone -androgen (testosterone)


  1. Growth development and maintenance of male reproductive organs.
  2. Sexual differentiation and secondary sexual characteristics.
  3. Spermatogenesis
  4. Male pattern of aggressive behavior.
  5. pubertal transformation.
  6. Enlargement of testes ,penis and scrotum.
  7. Pubic and axillary hair.
  8. Bone growth
  9. RBC mass increase
  10. Skeletal muscle mass increase
  11. Larynx enlarges -deeping increase
  12. Development of beard.

5) Ovaries-

Hormone – Estrogens  and progesterone


  1. Maturation growth and development of the reproductive organs
  2. Stimulation of normal physiological process of the tubular reproductive tract.
  3. Growth of the uterine tube
  4. Development of the endometrial lining of the uterus
  5. Increase the vascularity of the uterus
  6. Induction of the behavioral estrus
  7. Dilation of the cervix liquefaction of mucous plug.
  8. Under the influence of the estrogens the uterus is less susceptible to infection.


Function of thyroid gland-

  1. Role in growth
  2. It has role in development
  3. It stimulate heart rate and contraction.
  4. Stimulate synthesis of proteins and carbohydrates
  5. It encreases vit. Requirements.

Function of thyroid hormone

  1. Maturation of bone
  2. Maturation of skeletal system
  3. Maturation of nerves in CNS
  4. Regulation of growth hormone
  5. Regulation of body temperature
  6. Generation of heat
  7. Metabolic function
  8. It  influence mood and behaviour

Disorders of thyroid gland – Hypothyroidism


Hormone  Calcitonin

Function of PTH

             Bone  Parathyroid hormone stimulates the release of calcium from large calcium stores in the bone into the bloodstream.

This increases bone destruction and decreases the formation of new bone.

Kidney Pth reduces loss of calcium in urine.

Pth stimulate the production of active vitamin D in the kidney.

Intestine  pth indirectly increases calcium absorption from food in the intestine via its effects on vitamin D metabolism.


Posterior pituitary

Hormone     ADH

Function        Stimulate water reabsorption by kidney.

Hormone   Oxytocine

Function   Stimulate uterine muscle contraction release of milk by mammary gland.

Anterior pituitary

Hormone   TSH

Function     Stimulate thyroid gland.

Hormone    ACTH

Function      Stimulate adrenal cortex.

Hormone    PRL

Function      Milk production

Hormone   GH

Function      Cell division , protein synthesis ,and bone growth.

Hormone   MSH

Function Unknown function in humans regulates skin color in lower vertebrates.