Category: Physics Notes PPT

What is a Circuit Diagram?

A circuit is a pavement that the electric current takes to traverse, and a circuit diagram is a graphical demonstration of an electrical circuit.

In EEE or Electrical & Electronics Engineering, students employ various drawings or diagrams to display a certain electrical ckt. These electrical circuits are demonstrated by lines to represent wires and symbols to represent electrical & electronic constituents, as it aids in better apprehending the connection between distinct components. Electricians depend upon an electric circuit diagram for initiating any building wiring.

In this article, we will learn how to draw a simple electric circuit diagram.

Circuit Diagram

A simple circuit diagram comprises three following components essential for operating an electrical circuit:

• A Voltage source

• A conductive pathway (a path that facilitates the motion of charges), and

• A resistor (that can be bulb/motor, which requires electricity to do work)

Types of Electric Circuit Diagrams

A Block diagram is one of the easiest approaches to display the complex circuit in its simplest form. Without considering the complex interconnections or wiring, it displays the functioning of the principal components of an electric circuit in the form of blocks, and the lines connecting them are to showcase the relationship between these blocks.

Example: A block diagram displaying the process of converting an audio signal into a desired frequency modulated signal can be described through the following diagram:

The schematic diagram of an electric ckt displays all the electrical components & interconnections of the ckt by employing systemized symbols and lines. 

These diagrams are employed in presenting the series & parallel combinations and the accurate linking between their terminals. For example, in drawing a schematic diagram of a voltage amplifier, we employ symbols for displaying the electrical components and lines to present the interlinking between their terminals. The below diagram displays the circuit diagram of a voltage amplifier:

The pictorial ckt diagram is one of the fundamental diagrams that employs simple images of electrical components. These diagrams present a sketch of the particular electrical components and the interconnection between these.  These diagrams are simple to understand for those who are not familiar with their physical appearance.  

These diagrams employ various electrical components’ without considering their real location, how the wiring is marked or routed; however, it does represent the order in which these components are connected.

The below diagram is the simple pictorial circuit diagram of an automobile starter and ignition system:

                           

An SLD diagram has a higher use in real life. This diagram is the one-line representation of a circuit. 

We use a single line diagram to simplify presenting the typical complex three-phase power circuits by displaying all the electrical components.

However, these circuits don’t represent the electrical interlinking of the components; but they do display the size & rating of the electric constituents. 

Simple Circuit Diagram

For drawing an electric circuit diagram, we need to understand the following elements used in an electric circuit:

1. An electric cell

2. A battery or combination of cells

1. Open

2. Closed

1. Voltmeter: To measure the electric potential

2. Ammeter: To measure the electric current

Simple Circuit Diagram Symbols

Below are the symbols of the elements employed in an electric circuit:

Basic Circuit Diagram

A circuit diagram is a simple representation of the electrical components of a circuit by employing either the images of the different parts or the standardized symbols. It displays the relative positions of all the electrical elements & their interconnections. While getting electrical fitting at our newly built home, we often use a ckt diagram to provide a visual representation to an electrician. The below figure demonstrates a simple circuit diagram:

We can draw a simple electrical circuit diagram in the following way:

Now, we will learn how to build a basic circuit by using the electric elements.

How to Build A Simple Electric Circuit?

Electricity is the primary source of our life. While using it, we all find a way out to draw a simple circuit diagram to experiment with how a circuit works, so today, we are going to the same.

Aim: We aim to set up an electric circuit.

Required Materials

• A simple electric bulb or an LED

• Two small button batteries (cells)

•  Copper wire for interconnections

• A scotch tube

Step-by-step Instructions

• Now, pile the two-button batteries (the two balls, as shown in the above diagram) in such a way that they face each other, i.e., the plus-end of one battery is touching the negative-end of the other battery.

• Connect one wire to one node (or leg) of a bulb (a simple/LED) and the other piece of wire to another node of the bulb.

• Now, we can observe that the light goes off after all the interconnection; this illustrates that our simple circuit is complete.

• We can try connecting & disconnecting the wire and record our observations.

Complementarity is an interesting concept that was introduced by Neils Bohr in the year 1928. Neils Bohr introduced the complementarity principle or the concept of complementarity in one of the famous Como lectures. The concept of complementarity was not precisely descriptive in Bohr’s work, but whenever he elaborated the concept of complementarity it was fitting the explanation profoundly. Neils Bohr recognized the need for the mathematical formalism of quantum mechanics to be constructed in a rationally coherent conceptual framework if it were to serve as the core of an acceptable scientific theory.

Explain The Principle of Complementarity

As we already know, classical physics postulates that, at each instant of time, every elementary particle is located at some definite point or the position in space, and has a definite velocity, and hence corresponding definite momentum. On the other hand, in quantum physics, an elementary particle is represented by various distributions of possibilities, where the distributions in position and in momentum are related by Fourier transformation. This consequence explains that localization at a point in position space demands a complete lack of localization in momentum space and vice versa. 

Because of these contradictory theories regarding quantum motion Bohr came up with the complementarity principle. He explains that the very nature of quantum theory eventually forces us to regard the claim of space-time coordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and definition respectively. 

Bohr further explains that the theories of quantum mechanics are characterized by the acknowledgement of a fundamental limitation in the classical physical ideas when applied to atomic phenomena. The essence of atomic physics may be expressed in the so-called quantum postulate, which attributes to any atomic process an essential discontinuity, or rather individuality, completely new to classical theories and symbolized by Planck’s quantum of action. The quantum postulate implies that any observation of atomic phenomena will involve an interaction with the agency of observation not to be neglected.  Accordingly, an independent reality in the ordinary physical sense can neither be ascribed to the phenomena nor to the agencies of observation. After all, the concept of observation is so far arbitrary as it depends upon which objects are included in the system to be observed. Ultimately, every observation can obviously be reduced to our sense perceptions.

Bohr’s Complementarity Principle

Now let us explain the principle of complementarity or Bohr’s complementarity principle. We know that the consequence of the uncertainty principle is both the wave and particle nature of the matter can not be measured simultaneously. In other words, we can not precisely describe the dual nature of light. Now suppose that an experiment is constructed in such a way that it is designed to measure the particle nature of the matter. This implies that, during this experiment, errors of measurement of both position and the time coordinates must be zero or absent, this in turns explains that the momentum, energy and the wave nature of the matter are completely unknown. Similarly, if an experiment is designed for measuring the wave nature of the particle, then the errors in the measurement of the energy and the momentum will be zero, whereas the position and the time coordinates of the matter will be completely unknown. 

From the above explanation, we can conclude that, when the particle nature of the matter is measured or displayed, the wave nature of the matter is necessarily suppressed and vice versa. The inability to observe the wave nature and the particle nature of the matter simultaneously is known as the complementarity principle. It was first explained by Niels Bohr in the year 1928 and hence it is familiarly known as the Bohr’s Complementarity principle.

What Bohr explained or Bohr exact words were “In a situation where the wave aspect of a system is revealed, its particle aspect is concealed; and, in a situation where the particle aspect is revealed, its wave aspect is concealed. Revealing both simultaneously is impossible; the wave and particle aspects are complementary.”

Compactly stated, the essential idea here is that in theories of quantum physics the information provided by different experimental procedures that in principle cannot, because of the physical characteristics of the needed apparatus, be performed simultaneously, cannot be represented by any mathematically allowed quantum state of the system being examined. The elements of information obtainable from incompatible measurements are said to be complementary: taken together exhaust the information obtainable about the state. On the other hand, any preparation protocol that is maximally complete, in the sense that all the procedures are mutually compatible and are such that no further procedure can add any more information, can be represented by a quantum state, and that state represents in a mathematical form all the conceivable knowledge about the object that experiments can reveal to us. 

Did You Know?

The introduction of quantum mechanics was one of the most controversial scenarios in physics history as it was about to violate many classical aspects. The correspondence principle is one such discovery. It was probably Einstein’s new derivation of Planck’s black-body radiation law (1916-17) that most directly inspired Bohr’s formulation of the Correspondence Principle around 1918, which thereafter played such a large role in his attempts to understand quantum phenomena. Bohr’s reliance on the correspondence principle seems to have been a principal motive for his distrust of the photon concept and related willingness to give up energy-momentum conservation to save the classical wave picture of electromagnetic radiation.

Conservation laws are the backbone of physics. They determine what can occur or what cannot occur. Some of them are considered to be universal in the sense that it is believed that any possible process has to fulfill them without exception. From the fundamental point of view, these conservation laws are either motional (the conservation of momentum, energy, linear momentum, etc..) or material (Conservation of charges). No one has observed any process violating any of these rules. 

However, we remark that the conservation laws are only necessary conditions and not at all sufficient conditions. A hypothetical process that obeys only these conditions is thus not necessarily a process that can really take place in nature. So in classical physics, a process that occurs in nature has to obey an additional condition: the conservation of matter in the form of the conservation of mass. The conservation of mass plays an important role in nature, in physics the conservation of mass is depicted with the help of consideration of conservation of electric charges. The concept of conservation of mass is widely used in the field of classical mechanics, chemistry, and fluid mechanics.

Law of Conservation of Mass:

The law of conservation of mass is formulated and systematized by 18th-century French chemist Antoine Lavoisier. According to the conservation of mass, all the reactions and interactions within a closed system will leave the mass of the system unchanged. In other words, the conservation of mass refers to the fact that the mass of an isolated system or closed system is neither increased nor decreased by the reaction between the parts. The total mass of the system before the reaction will be equal to the mass of the system after the reaction. The matter is always conserved.

What is The Law of Conservation of Mass:

The law of conservation of mass states that the matter can neither be created nor be destroyed, but it can be changed. It is also known as the conservation of matter. From the statement of the law of conservation of mass, it is understood that matter is conserved. In a closed system, the mass of all the substances before the chemical reaction will be the same as the mass of the substances after the chemical reactions.

According to the law of conservation of mass during any chemical reaction, no atoms will be created nor be destroyed, therefore the mass of reactants must be equal to the mass of the products in any low energy thermodynamic process. Initially, it is believed that the law of conservation of mass or the law of conservation of matter originated from classical mechanics, after some time it was modified according to quantum mechanics with the help of the mass-energy relation. In 1789, Antoine Laurent Lavoisier was an 18th-century French chemist who proposed the law of conservation of mass and discovered the conservation of mass. 

Derivation:

Though the conservation of mass mainly focused on the chemical reactions it’s considered to be equally important from the physics point of view as well. According to the conservation of mass, it says that the object or the collection of the object will remain the same no matter how many times we rearrange, it parts it away. With the help of the concept of the theory of relativity, the concept of mass underwent a radical revision. The meaning of mass lost its absoluteness. The mass of an object was seen to be equivalent to energy, and the mass and energy of the system were found to be interconvertible and to increase significantly at increasing high speeds near that of light. 

The meaning of the mass has been always varying according to the concerned subject of discussion. The mass has been viewed mainly in two compatible ways in physics. Sometimes the mass is viewed as a measure in terms of inertia, and sometimes as an opposition that offers forces to the body in motion. Thus, from the perspective of either inertial mass or the gravitational mass, according to the principle of the law of mass conservation, different measurements of the mass of an object considered under various circumstances should always be the same.

Consider a collection of objects located somewhere in space. This quantity of matter or the system of objects with well-defined boundaries is known as a system. The law of conservation of mass then implies that the mass of this given system remains constant it can not be created nor be destroyed, therefore, we get,

[ Rightarrow frac{Dm}{Dt} = 0]

Where, 

Dm is the infinitesimally small part of the considered system of objects. 

The volume occupied by the matter or the system of objects may be changing and the density of the objects within the system may be changing, but the mass of the system remains constant.

Importance of Conservation of Mass:

Physics is essentially an experimental and observational science. Predictions of any theory have to be confronted with experiments and observations. Conservation laws are the backbone of physics. All observed processes should conserve all universal laws and also specific laws associated with the interaction which governs the observed process.

The conservation of mass implies that matter can be neither created nor destroyed—i.e., processes that change the physical or chemical properties of substances within an isolated system or a closed system (such as the conversion of a liquid to a gas) leave the total mass unchanged. Strictly speaking, mass is not a conserved quantity. However, except in nuclear reactions, the conversion of rest mass into other forms of mass-energy is so small that, to a high degree of precision, rest mass may be thought of as conserved.

Did You Know:

The history associated with the discovery of the conservation of mass is remarkable. An important idea from ancient Greek philosophy was that “Nothing comes from nothing” so that what exists now has always existed: no new matter can come into existence where there was none before. An explicit statement of this, along with the further principle that nothing can pass away into nothing, is found in Empedocles (approx. 490–430 BC): “For it is impossible for anything to come to be from what is not, and it cannot be brought about or heard of that what it should be utterly destroyed.” We knew about the conservation of mass from ages and it took centuries to frame it to a universal law.

Jain philosophy, a non-creationist philosophy based on the teachings of Mahavira (6th century BC), states that the universe and its constituents such as matter cannot be destroyed or created. The Jain text Tattvarthasutra (2nd century AD) states that a substance is permanent, but its modes are characterized by creation and destruction. A principle of the conservation of matter was also stated by Nasīr al-Dīn al-Tūsī (1201–1274). He wrote that “A body of matter cannot disappear completely. It only changes its form, condition, composition, color, and other properties and turns into a different complex or elementary matter”.

In this world, we have both natural mirrors and man-made mirrors. Mirrors are a fascinating world by themselves. There are mirror museums where you have all shapes and kinds of mirrors which will make you appear tall, short, fat, thin and a variety of other things! Cartoons from our childhood would have their characters enter mirror worlds that were exactly the opposite of our real worlds. 

The study of mirrors is one of the fundamental topics in physics. Do you see how closely this science is connected to our daily lives? Each morning and evening we see our reflection in the mirror at home – we tend to see not only the external self but also end up reflecting on what is going on inside of us. It is said smiling to yourself in the mirror, first thing in the morning fills your day with positivity! 

Convex Mirror – Application and Working of Convex Mirror

Convex mirrors are also popularly called the fish eye mirror or diverging mirror. Its reflective surface bulges in the direction of the light source. A convex mirror has the ability to reflect all the light that falls on them in the outward direction. So, the type of image formed by these mirrors is always imaginary/virtual. 

 

Also, due to the above property the size of the object’s image is smaller as compared to the actual object’s size. Therefore, a convex mirror is the most appropriate in those areas where large objects have to be viewed in a tiny size. This makes it easy for a person to view the image. 

 

How does a Convex Mirror Differ from a Concave Mirror?

A convex mirror is also commonly called a curved mirror. Where the reflective surface of a concave mirror bulges towards the inward direction, in the case of a convex mirror it bulges in the direction where the light source is located. 

 

The image of the object formed by a concave mirror is bigger than the actual size of the object. In the case of a convex mirror, it makes the object appear smaller in size. A concave mirror is used to magnify the image of the object but a convex mirror reduces the image size so that it gets accommodated easily in the mirror. 

 

What are the Ways to recognize a Convex Mirror?

If you have to find which one is a convex mirror out of the different types of mirrors like a plane mirror, concave mirror, and convex mirror, then it can be done just by looking at the size of the image. 

 

When you use a plane mirror, you will find that the size of the image generated by it will be the same as the actual size of the image. In the case of a concave lens, you will find that when the object is placed near the mirror, its image gets enlarged. 

 

You will see an inverted form of the image when the object is kept at a far distance from the mirror. It is only a concave mirror that has the ability to generate an actual inverted image. The size of the image produced by a concave mirror is based on the screen placement. In the case of a convex mirror, it always generates a small-sized straight image.

 

Why is a Convex Mirror called a Diverging Mirror?

A convex mirror is given the name of a “diverging mirror”. It is because of the behavior of the mirror that makes light rays diverge upon reflection. By this, it means that when a light ray is directed on this mirror, it enables the originally parallel light rays that form the beam to deviate/diverge after hitting the reflective surface of the convex mirror.

 

Understanding the working of a Convex Mirror

In a convex mirror, there is a point where light rays received from all the different directions meet. This helps in creating a focused beam. This point is referred to as the “focal point” or the focus. There is another term called “focal length” that determines the distance between the front of the convex mirror and the focal point. 

 

Now let us understand the type of image formed by a convex mirror. A curved or convex mirror bends outward in the shape of a dome. It always forms an imaginary image. The reason behind it is that the “center of curvature” and the point of focus are both imaginary points in the mirror. Both of these points are unable to be reached. 

 

It implies that the type of image made by this type of mirror can’t be projected on the screen. The image generated by the convex mirror is an upright virtual image that is relatively smaller in size than the size of the projected object.

 

Below are the major possibilities of a convex mirror for the object positioning in a convex mirror.

 

When an object is located at infinity

When the object lies at infinity, then a tiny image is produced at a principal focus point. This point is located behind the mirror. You will see that the image produced is virtual, highly diminished and erect.

 

When an object lies between the pole and infinity of the mirror

When an object lies between the pole and infinity of this mirror, then you will see a diminished form of an erect and virtual image. This image is created between focus and pole behind the convex mirror.

 

What are the Areas of Application of a Convex Mirror? 

There are different functions performed by a convex mirror that makes it useful in a variety of applications. Let us see some of the important uses of convex mirrors. 

Automobiles: Safety and efficiency are the two most essential requirements when you drive on the road. By providing a good overview to drivers about the rear and side view of the roads, and surroundings, help drivers to foresee risky situations and avoid accidents. The convex mirror is one of the important things that offer a clearer rear view of the road to ensure maximum safety all the time. 

 

A convex mirror has broader fields of view as compared to reflective surfaces of concave and plane mirrors. Due to this, convex mirrors are used in forming side mirrors off an automobile. These mirrors provide a fish-eye view to the person who drives the automobile. This feature helps them to get a clear view of the rear area of the road easily.

 

The virtual image created of the object has a smaller size than its actual size. It provides a wide field view. Convex mirrors provide heightened safety for motor drivers on roads, alleys, and driveways where very little visibility is there.

 

Automated Teller Machines 

Convex mirrors are kept close to the ATM or automated teller machine to permit the customers to figure out whether someone is standing behind them. This is used to ensure the security of the customers while they use an ATM. It ensures safety from the theft of withdrawals of cash or any other precious item. Also, it keeps the identity of the machine user safe and secure.

 

In-Camera 

Some mobile phones come with a selfie camera built into them that aids users to capture a self-portrait shot.

 

Inside Buildings

Large hospitals, hotels, schools, offices, apartment buildings or stores use convex mirrors to allow people to view what goes around a corner. This helps in avoiding minor or major collisions.

 

In Sunglasses 

Convex mirrors are used in developing a sunglass lens. The overall purpose is to reflect the sunlight away from the pers
on who wears these glasses.

 

In the Magnifying Glass

Two convex mirrors when placed next to each other can form a magnifying glass.

 

In Street Light

A convex mirror is used as a street light reflector due to its ability to spread light rays over a larger region.

 

In Telescope

Convex mirrors are used in telescopes to see far off objects clearly in the form of point-sized images. 

  

Production Process

Another important use of a convex mirror is in the work environment at the time of the production process. A convex mirror placed on the conveyor belt assists in viewing a product from varying angles. 

 

This enhances the quality of the product by getting aware of any kind of production-based faults and improves the efficacy of production processes. This happens by eliminating the requirement to assess the quality of products on the conveyor belt.

Curie point is also named as Curie Temperature. Curie temperature is the temperature above which some changes are made due to its impact on certain magnetic materials. Curie temperature diminishes the magnetic properties of the material. 

If you consider some rocks and minerals, then you will notice that there is remnant magnetism. Also, the remnant magnetism appears below the Curie point.

The temperature is about 570 °C (almost 1,060 °F). This is the result of the general magnetic mineral magnetite. ‘Pierre Curie’ – is the name behind the temperature of Curie point. Find the definition of curie point in brief. 

Do you know the curie point of nickel? 

Nickel Curie point possesses a temperature of 627 K. 

Curie Temperature Definition

Curie point definition is very easy to understand. It is named after the French physicist. He had discovered it in 1895. He also put forward certain laws that were related to some magnetic properties in temperature change.

Let’s find something interesting that is related to the Curie point. Consider an example of iron—atoms with a temperature of 770 °C (1,418 °F). Each iron atom acts as a tiny magnet at this temperature spontaneously. Each of them will align themselves as some kind of magnetic material. 

In the case of pure iron, the atomic magnets are distributed within each microscopic region. Pure iron is considered among the categories of Ferromagnetic materials. The directions of the magnetic fields are the same so that their magnetic fields strengthen each other.

Well, you won’t find the same in antiferromagnetic materials. Their materials possess the atomic magnets that have the alternate property of magnetic fields. They act in opposite directions. This tendency explains that their magnetic fields cancel each other. 

You may notice different types of spontaneous arrangements in ferrimagnetic materials. This is a mixture of both patterns. They are generally involved in two types of magnetic atoms. This feature enables them to yield the property of partial reinforcement of magnetic fields.

Miscellaneous Facts on Currie Point

Three classes are there that involve the raising of temperature to the Curie point. They apply to any type of material. Numerous spontaneous arrangements are found in these types of disrupts. 

Among them, only a few weak magnetic behaviours exist. All of these processes are kind of more general. We call them paramagnetism. For information, you should know about the highest Curie point as the value for cobalt is 1,121 °C (2,050 °F). 

The rise of temperature above the Curie point can lead to the production of roughly similar patterns of decreasing paramagnetism. This behavior is constant in all three classes of materials. 

When you try to cool down the temperature of these materials below their Curie points, the magnetic atoms will start to realign spontaneously. This is the behaviour that initiates the effect of ferromagnetism or antiferromagnetism among the metals.

Néel temperature is the behavior that is pointing towards the antiferromagnetic Curie point. The name is given to the term in honour of the French physicist Louis Néel. He had explained antiferromagnetism successfully in 1936.

Application of Curie Point

Steel wire has atoms that tend to behave as a magnet when they are subjected to the electric field.  At this moment, they act like tiny magnets. Each end of the steel rod turns into a north and south pole. 

Generally, these atoms do not possess any significant direction of the magnetic field. They all are in different directions. So, you can say that the steel does not exhibit any type of net magnetic field. 

At a moment when you try to bring a magnet close to the wire, it makes the steel atoms close to each other and stays in a lineup format. The queued atomic magnets help the steel wire to convert into a magnet. The steel does not have any magnetic behavior in nature, but it turns into something that attracts the original magnet.

The process of magnetization can be disturbed by high temperatures. Thermal energy is very much responsible for the steel atoms to wobble back and forth. The energy leads to the disturbing tendency of the magnetic alignment. 

When you notice the maximum vibration among the atoms, the behaviour of being the atomic magnets do not remain as usual. At this moment, the steel gives up its magnetism. Curie point is the reason for which this occurs.

Do You Know?

You must have heard of a core of molten iron inside the earth. This iron ore cannot be magnetized, which has a temperature above the Curie point.

How the earth behaves as a magnet and possesses a magnetic field. Due to its magnetism, it has a North and a South magnetic pole. An electromagnet is a reason for the generation of the magnetic field of the earth.  

Do you know why? This is due to the passage of electrical currents flowing through the liquid metal core deep inside the earth.

Being a science enthusiast, you may have come across the word dark matter, or maybe you already have a theory of your own. Well, let’s take a deeper dive into the dark matter, and let’s find out what is dark about it. Dark matter may be defined as a form of matter considered to be approximately 95 percent of the matter of the universe. After several scientific studies, it is assumed that dark matters are about 27% of its total mass-energy density or about 2.241×10⁻²⁷ kg/m³. In this article, we are going to discuss dark matter theory, the meaning, and its discovery in detail. 

The Discovery

The existence of the ‘missing mass’ or ‘dark matter’ was first proposed by Swiss American astronomer Fritz Zwicky. In 1933, he discovered that only 1 percent of the mass of all the stars in the Coma cluster is needed to keep the galaxies from escaping the gravitational pull of the cluster. In the 1970s, this theory was approved upon observations by American astronomers, Vera Rubin and W. Kent Ford. They observed, within a galaxy, the mass of the visible stars is only about 10 percent that is required to keep the stars orbiting the center of the galaxy. To account for the slightly increasing (or constant) orbital velocity of the stars, the mass of the galaxy within the orbit of the star must be increasing linearly with the distance of the center of the galaxy from the stars.

Dark Matter Meaning

There are several observations to imply the presence of dark matter such as gravitational effects. Until and unless more matter is present beyond our observations, they are not explained by accepted theories of gravity. Dark matters are substances that do not absorb, reflect or emit light and hence not visible. Dark matter is a non-interacting substance, and this is what makes it dark and mysterious. It is considered that about 5 percent of the universe is known to us. The rest 95 percent includes about 27 percent of dark matter and 68 percent of dark energy. We are pretty sure of the existence of dark matter, but still to find out what dark matter is and how it exactly works.

Dark Matter Theory

The existence of dark matter can be confirmed upon the discoveries of Swiss American astronomer Fritz Zwicky and Jan Oort. According to them, the motion of the galaxies and nearby stars of the Coma clusters violates the expected motions according to Newton’s law of gravity. But still, any direct evidence of the presence of the dark matter is not encountered.

According to NASA, we know more about what a dark matter isn’t than what it is. Dark matter cannot be seen in the form of our known cosmic objects such as stars and planets. It is not in the form of baryons as we know we would be able to detect baryonic clouds by their absorption of radiation passing through them. Again, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter collides with another matter. Based on how many gravitational lenses we see, we can rule out large galaxy-sized black holes. High concentrations of matter cause the bending of light, which passes near them from objects further away. But we cannot see enough lensing events so that it can suggest that such objects have the required 25% contribution of dark matter. There must be several theories about the existence of dark matter, but no direct evidence is acquired till now. 

Did You Know?

Dark matter is a subject that gives us goosebumps, thinking about the fact that it is yet to be discovered. The Discovery of dark matter and dark energy would give us a better picture of the universe and how it exactly works. Here are some facts about dark matter. The substance of dark matter doesn’t interact with light and that is why dark matter is invisible. Though dark matter cannot be seen, it can be felt for its powerful cosmic impact. It is predicted that the powerful impact of dark matter binds the galaxies together. According to some research, dark matter might be cold in nature. Also, dark matter might not have any existence.