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.


short series – 8 SKIN


The skin has two primary layers: the epidermis (outer) and the dermis (inner). The epidermis has two important sublayers the stratum germi nativum and the stratum corneum. The epidermis is made up of cells called keratinocytes; these cells make up the epithelial tissue.

It is in the epidermis layer where blisters and calluses can form. Blisters occur when friction such as what might develop between the skin and the inside of a shoe-causes layers to separate within the epidermis or between the epidermis and the dermis.

As these layers separate, tissue fluid may build up, leading to a blister. While blisters often result because of fric tion, calluses result from pressure. When exposed to increased amount of pressure, mitosis will occur at a rapid rate, causing the epidermis to thicken.


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



Glucose, Fat, and Protein Metabolism

Glucose, Fat, and Protein Metabolism

In the muscles and other tissues, cortisol increases the breakdown of pro tein into amino acids.

Those amino acids are used to produce additional glucose (via a metabolic pathway called gluconeogenesis) in the liver.

Cortisol also conserves glucose for the brain and spinal cord by blocking the actions of insulin (which will be discussed later in this chapter) inhibiting glucose absorption into other tissues.

Cortisol also stimulates the release of fatty acids and glycerol from adipose tissue.

Glycerol is used in gluconeogenesis, while fatty acids are made available for energy to other tissues to preserve glucose for the brain.

Cortisol reduces protein reserves everywhere except in the liver.

As proteins continue to be broken down in muscles and in other tissues, blood levels of amino acids rise.

The additional amino acids are used for gluco neogenesis, glycogen formation, and protein synthesis in the liver.


Growth Hormone levels

Growth hormone, also called somatotropin, is a large polypeptide hormone produced by somatotroph cells in the anterior pituitary that plays a signifi cant role in growth and metabolism. It primarily affects bone, muscle, and tissue growth.

Without sufficient growth hormone, an individual would suffer from short stature. Too much growth hormone would result in gigan tism. For normal growth to occur, the body requires energy, which growth hormone provides through protein synthesis and the breakdown of fats.



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.


The Hypothalamus and Pituitary Gland

The hypothalamus and pituitary gland together serve as the command center of the endocrine system, and the core of the relationship between the endocrine and nervous systems. Together, they regulate virtually every physiological activity in the body.

As mentioned earlier, the nervous and endocrine systems also regulate each other: neurohormones from the hypothalamus direct the release of endocrine hormones, and hormones from the endocrine system regulate nervous system activity.



The pancreas is an irregular-shaped gland that is located just below the stomach and adjacent to the duodenum of the small intestine. It averages between 4.7 and 5.8 inches (12 and 15 centimeters) in length, and a little over 0.8 inches (2 centimeters) in thickness. For descriptive purposes, it is divided into three major sections, although there is little difference in the physiology of the sections. The head is located closest to the duodenum and is connected to the digestive tract by two ducts. The hepatopancreatic duct is a common duct formed by the linking of the bile duct and pancreatic ducts. A second duct, called the duct of Santorini, directly connects the pancreas to the duodenum. Moving away from the duodenum and the head of the pancreas are the regions called the body and tail.

The pancreas actually represents two separate organs, both of which contribute to digestion, which are integrated into a single structure. A por tion of the pancreas is an exocrine gland, meaning that it secretes com pounds into a cavity.

The second major area of the pancreas is the endocrine tissue, which secretes chemicals into the bloodstream. In general, the exocrine functions of the pancreas can be described as those directly involved with the processing of nutrients in the duodenum, while the endo crine is best described as those functions that involve hormones and the regulation of glucose homeostasis in the body. Both types of tissue exist throughout the pancreas.

Enzymatic Digestion

Enzymatic digestion is responsible for breaking organic material into smaller subunits that can be absorbed into the circulatory system.

The amount of enzymatic digestion within the oral cavity is small in comparison to the activity of the lower GI tract. However, there is some initial digestion of both carbohydrates and lipids in the oral cavity.

The salivary glands, primarily the submandibular and sublingual glands, secrete an enzyme called salivary amylase.

Recall that the nutrients are primarily absorbed from the digestive system in their simplest structure, or monomers. Salivary amylase belongs to a class of enzymes that digest complex carbohydrates, such as starch, into monosaccharides.

The monosaccharides are easily absorbed into the circulatory system, although little absorption occurs in the oral cavity. The salivary amylase is mixed into the food by the action of the tongue and cheeks and continues to break down the starches in the food for about an hour until deactivated by the acidic pH of the stomach. A second enzyme of the oral cavity is lingual lipase.

Lingual lipase is secreted from glands on the surface of the tongue. This enzyme acts on triglycerides in the food, breaking them down into monoglycerides and fatty acids. How ever, the action of this enzyme is relatively minor and it does not make a major contribution to overall lipid digestion.



Vitamins are similar to the energy nutrients in that they are organic mole cules, but differ in the fact that the body does not get energy directly from these molecules. Instead, vitamins serve as enzyme assistants, or coen zymes. Some vitamins, specifically the B-complex vitamins, are directly involved in the processing of energy nutrients, specifically lipids and carbohydrates. Certain vitamins serve as protectors of the delicate cellular machinery. These are called the antioxidants and are best represented by vitamins C and E. Others aid in the vision pathways (vitamin A), or in the building of healthy bones (vitamins D and A). Nutritionists divide the vitamins into two groups based upon how they interact with the body.

The first are the water-soluble vitamins, a group that consists of vitamin C and the B vitamins. These vitamins are readily absorbed by the digestive system and, with a few exceptions, do not require special processing. The other class, known as the fat-soluble vitamins (vitamins A, D, E, and K), are frequently treated in the same manner as the triglycerides, meaning that they are packaged into specialized lipoproteins and transported by the lymphatic system. In general, both classes are required in relatively small quantities (micrograms or less) daily by the body.