Category: Physics Notes PPT

Development in technology has been quite synonymous with advances in physics, and this has, over the years, influenced society beyond our wildest imagination. The indelible role of physics in society is thus wholly undeniable. Such influences and subsequent advancements could broadly be categorized as falling under two major categories – Macroscopic and Microscopic. The microscopic influence includes all phenomena related to atomic, molecular, and nuclear advancements. The macroscopic consists of everything within the ambit of laboratory testing, practical effects and advancements, and astronomical associations. 

As evident, these two categories are overlapping at times, and it is only through a close association between these two areas that the age of technology, as we know it today, has come to be. 

How is Physics Related to Society and Technology?

The first significant influence that physics exerted in terms of technological development led to the introduction of the steam engine, which subsequently ushered the age of industrialization. The steam engine worked on the laws of thermodynamics and greatly improved the efficiency of engines for starters. The applications of thermodynamics have subsequently also been used in later inventions like refrigerators, blowers, vehicles, etc. Here are some of the ways physics has left its impression on society through technological advancements.

1. Energy Industry 

The contributions that physicists like Faraday, Tesla, and Edison had on the commercialization of electricity is undoubtedly exceptional. They kick-started what is today called the age of globalization. The use of fossil fuels like petrol, diesel, coal changed everything from how the food was produced to how people travelled from one place to another. The influence was so prolific that it is difficult today to name an industry that wasn’t influenced for the better, through these developments. 

With increasing awareness about the growing levels of pollution today, the world has shifted to alternative and renewable sources of energy. Even this gradual shift is being overwhelmingly influenced by physics. Dams, solar panels, wind farms, nuclear reactors – the energy of the future is overwhelmingly dominated and influenced by the physics of today. 

2. IT Industry 

The IT industry has been spearheaded by the extensive proliferation of computers in our daily lives, thus giving rise to the modern MNCs as we know them today. While the computer may not have been developed exclusively on the foundation of physics, the subsequent infrastructure, including the once ancillary but now vital data processing and network speeds, have been largely contributions of physics. 

For starters, John Bardeen was instrumental in the development of transistors and the theory of superconductivity, factors that led to the development of the early computer. The use of lasers was pioneered by C.H. Townes, which is now used from microsurgery to the most commonly used computer mouse. Even the use of optical fibres is based on the principle of total internal reflection of light. Optical fibres ensure better connectivity speeds and minimal data loss, thereby ensuring faster processing speeds and better reception of signals.

3. Medical Industry

In the medical industry, physics has been especially essential in radiology. W.K. Roentgen discovered X-rays, which is today the most popular, conclusive, and inexpensive method of determining fractures in the body. Ultrasonography works on the principle of reflection of ultrasonic waves and forms an essential part of both the medical as well as the defence industry. 

Another singular influence has been the use of nuclear medicine to cure diseases. Nuclear medicine today includes therapies that use radioactive elements to treat conditions like hyperthyroidism and certain types of lymphoma. 

4. Communications Industry 

In this case, by the communications industry, we refer both to the telecom and television industry, which has connected the world digitally, as well as the commercial vehicular industry like airlines which has made physical travel between places extremely easy. Telephones and televisions operate on the principle of electromagnetic waves. The generation of electromagnetic waves was first shown by the German physicist Heinrich Rudolf Hertz. Aeroplanes, on the other hand, at the fundamental level, operate on Bernoulli’s principle. 

5. Contributions that Went Beyond a Single Industry

There are various other discoveries that physics propagated that went on to change society in more ways than one. These include:

• Principle of levers and carriers – Archimedes

• Galilean Telescope, Gaseous Thermometer – Galileo Galilei

• Geometric Optics – Johannes Kepler

• Law of Elasticity – Robert Hooke

• Expanding nature of the universe – Edwin Hubble

Physics also helps us understand other disciplines like geology, agriculture, chemistry, biology, and environmental science. Astrophysics and cosmology, the two branches of physics help in expanding our vision into the universe.

Conclusion

Thus, physics helps improve the quality of our life. Physics is necessary for the development of new gadgets. Most of the modern gadgets used in our homes make use of Physics to form and function. Understanding Physics makes us understand the world surrounding us. It also helps in the development of new techniques for medical applications, such as computer tomography, magnetic resonance imaging, positron emission tomography, ultrasonic imaging, and laser surgery.

This makes Physics touch all areas of our lives and illuminate them all. This brings to light the value of Physics in our life. Therefore, all educational institutes should and do promote the study of Physics and provide the necessary infrastructure for study and research in this field.

The length of the path travelled by a car moving from one point to another point is called distance and the distance travelled is also known as the path length. However, if it takes the shortest path, it becomes the  displacement. We can also say that the difference between the initial and final position of a car is its displacement. 

But before we move forward let us know what motion is. If we look around, everywhere we can see objects moving. Kids play, birds fly, animals move in search of food, people walk or run, vehicles run on the road, river flow, etc. So basically, we can find motion everywhere in the universe. But what is meant by motion?

If you notice the above-mentioned instances they all move from one place to another and change their place. Therefore, motion is nothing but change in the position of a body with respect to time. If a body is at rest, it means that the body is not in motion, merely means that it is being described concerning a frame of reference. 

Position – Understanding with an Example

To describe the motion of an object, you must know and be able to describe its position.

Let us understand this with an example, let us say Ram moved from point R to S. This means Ram’s initial/previous position was R from where he shifted to S after sometime. Now the question is how can we represent Ram’s initial position? 

In physics, we specify a position with the help of a reference point and a set of three mutually perpendicular axes or  rectangular coordinate systems. They are the X, Y, and Z-axis. The reference point is known as origin; it is the intersection of the above three-axis (X, Y, and Z). So we take point R as the reference point or origin with coordinates (0, 0, 0) and S is represented by a set of coordinates on the three-axis (X, Y, Z).

Since we know that motion is the change in position with time, we install a clock in this system. The coordinate system along with the clock is the frame of reference. A frame of reference is an arbitrary set of axes from which the position and motion of the object are described. Thus, if one or more coordinates of a body change with time, the body is said to be in motion.

Path Length

The path length is the actual length of the path traversed by the body between the Initial and Final positions.

Displacement – Understanding with an Example

It is the shortest length i.e. Straight line distance between Initial and Final positions. Displacement is a vector quantity.

Displacement formula:

If s_i is the initial position of an object and s_f is the final position, then the displacement of this object is:

s  = s_i – s_f

Here, s is a variable referred to as displacement.

Since displacement has magnitude and direction, it is a vector quantity and the path is a scalar because it has only and no direction.

Explanation with Examples

To have a proper understanding of the position, path length, and displacement and the difference between them. Follow are some examples given with explanation:

Let us take three examples here. In the first one, Ram starts travelling from point R of the square path RSTU with RS = 1 km. He travels through S, T, U, and comes back to R in 20 minutes. The distance travelled by him is 4 x 1 km = 4 km. But if you see the change in his position from the start to the end of the journey, it is nil (It has no change). Ram started at point R and came back at R.

In the second example, 

Ram travels from Point R to S along the straight line in 60 minutes. The distance travelled by him is 5 km. And the total distance from the start to the endpoint travelled by Ram is also 5 km.

Now in the third example, Ram travels through the triangular path. He starts from point R and reaches T through point S in 120 minutes. The distance that has been travelled by him is 3 km + 4 km = 7 km. But if we see how far he is from the point where he started his journey, it is 5 km.

If you notice the above examples, the distance travelled and the change in position may or may not be the same.

The distance travelled by the body is known as the path length. Whereas the change in position, that is the difference between the initial and final positions of the body is called its displacement.

Hence, the path length is 4 km but the displacement is 0 in the first case.  The path length is the same as the displacement – 5 km in the second example and the third example, the path length is 7 km but the displacement is 5 km.

From the above text, we understand that the position of an object describes the point at which the object is standing at an instant. The change in position describes that an object is set into motion and this distance travelled is the path length. Also, if an object takes the shortest path, it is displacement.

Pressure in Drops

Let’s consider a liquid drop which is having a pressure P1; on comparing its pressure with the atmospheric pressure Patm, we found that P1 > Patm.

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This happens due to surface tension.

The surface of the body behaves as if covered by a stretched membrane having tension in all directions parallel to the surface that the pressure of liquid increases within a bubble. 

Consider the free-body diagram of a liquid drop, as shown in Fig. 

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If the force due to surface tension at the circumference is balanced by the pressure forces inside the drop, then:

                                    2πRσ = PπR2

We get:                         ΔP = 2σ/R  

Here, ΔPis the pressure difference between inside the drop and outside.

What is Blood Pressure?

Our heart pumps blood, oxygen, and nutrients through the arteries in our body.

Blood pressure is the measure of the force exerted by the circulating blood against our arterial walls.

There Are Two Readings Which Measure Blood Pressure, Which Are

1. Systolic blood pressure

2. Diastolic blood pressure

Systolic blood pressure is the higher number. It measures the force of blood being pumped around our body when our heart contracts.

Diastolic blood pressure is the lower number. It measures when the heart relaxes between beats.

The normal bp value is 120 mm Hg/80 mmHg.

Where mmHg stands for millimeters of mercury.

High BP 

High blood pressure is always higher than the normal range of the bp. 

It is also known as hypertension.

Its value is 140 mmHg / 90 mmHg or higher. 

BP Drop

The value of bp, 90 mmHg/60 mmHg or lower is considered to be lower bp or bp drop. 

Bp drop is also known as hypotension.

A Sudden Drop in Blood Pressure

A sudden drop in blood pressure happens when your organs don’t get the proper amount of blood and oxygen.

According to the American Heart Association, we don’t have fixed readings for specifying low bp.

However, medical experts say that our bp is low when systolic bp is less than 90 mmHg diastolic bp is less than 60.

So, if bp measures 84 mmHg/57 mmHg; it means our bp is low.

The Consequences of a Sudden Drop in BP Are

1. Dizziness or light-headedness

This happens when our brain doesn’t get enough supply of blood.

     2. Fainting

Insufficient supply of blood to the brain can cause us to lose consciousness.

    3. Blurred vision

    4. Lack of concentration

    5. Unable to focus on anything

Bp drop diminishes attention.

   6. Memory nausea

We may feel discomfort, uneasiness, or an urge to vomit, and 

  7. Rapid breathing

   8. Breath becomes shallow and breathing rate per minute increases. 

The heart compensates for the lack of blood by pumping faster.

   9. Fatigue

Tired or not wanting to do any physical activity.

BP Drops During Exercise

Blood pressure is measured by multiplying cardiac output and the total peripheral resistance.

Bp can change in response to an activity, body size, and diet.

It may happen due to health problems like obesity, or because of the blood vessel disease.

Bp is internally managed by baroreceptors, enlarged arteries that can detect changes in the blood pressure, and alert our nervous system to release hormones that constrict or dilate the vessels as per the requirement.

According to the Hemodynamics of Hypertension report, the type and duration of the exercise, how much water we lose through sweat, and in-case we exercise in the heat are factors that can usher to a drop in blood pressure.

However, if our bp persistently drops when we go from lying down to sitting up or from sitting to standing, we may have an orthostatic drop in blood pressure or postural bp drop.

Postural Hypotension Drop

The age-factor is the cause of postural hypotension.

Let’s assume an old person seated or lying down just like a bottle resting on the table as shown below:

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The blood is uniformly distributed in the body. 

Now, if he suddenly stands up, due to the gravity effect, the blood tends to pool in the lower part of his body.

Just like we drink some amount of water, the remaining quantity rests at the lower part of the bottle.

Now, if he certainly stands up, the blood pools in the lower part (because of gravitational pooling), his upper part may not get enough blood. 

This, in turn, may lead to a deficiency in the supply of blood and oxygen to cerebral ischemia, resulting in vertigo dizziness.

Therefore, to compensate postural hypotension, his heart pumps at a higher rate to bring the bp at a normal level.

Postural Drop in Blood Pressure

While measuring our bp, we could see a drop from 120/80 to 100/70 within minutes of changing your position.

Do You Know?

According to Langdon’s position, if we suddenly stand or sit, 600 to 700 ml, our blood is reduced in the upper part of the body because of pulling in the lower part of the body.

Wood is the second most used material for construction purposes, making of furniture, flooring, etc. For building constructions, though the stone has taken first place, the boom of wood has increased dramatically in recent times. Let’s see more interesting facts about wood, different physical, chemical, mechanical, properties of wood.

Tissue Composition of Wood

Wood is a natural resource that can be obtained by plants and trees. Basically wood is a combination of different tissues like the xylem, which is a vascular tissue, phloem, and cell walls. The vascular cambium layer which is present inside the bark helps to produce new wood.

Properties of Wood

The properties of wood explain its behaviour, and how it reacts to different substances at different temperatures. These properties explain the characteristics of wood with a generalized meaning. The properties of wood may include physical properties, chemical properties, mechanical properties. The physical properties of wood can be defined as the characteristics of a wood that do not have any change in its size, shape, colour, etc.

Physical Properties of Wood

The characteristics of wood that explain the physical features of various types of wood are nothing but the physical properties of wood. They are explained as follows.

Colour – As the basic use of wood is to make furniture and decor items for the house, colour and appearance play a vital role in choosing a variety of wood. But the colour of the wood varies from type to type. The wood is available in a wide range of colours starting from white to dark brown etc. The colour of the wood also changes with the observation. If a tree can be observed from top to bottom, it appears in some colour and vice versa.

Lustre – Another physical property of wood is its lustre. Luster refers to the tendency of elements with the reflection of light. After colour, priority is given to the lustre of the wood.

Odour and Taste – We commonly observe different odours from different types of wood. For example, the sandalwood and the rosewood give a nice aroma whereas the other timber woods may give some tobacco odour. Also, the new wood sample gives a fresh aroma and it keeps on degrading with time.

The density of Wood – Another characteristic of wood is its density. But what is the density of wood? The density of wood refers to its mass per unit volume. Based on the weight of the wood sample, the density of wood changes. Different types of wood have different densities. Below detailed information about the density of different types of wood is given.

• If the density or specific gravity is 36 then the wood is called very light.

• When density or specific gravity is = 0.36 then the wood is called light.

• If the density or specific gravity is 0.36 – 0.05, then wood is considered moderately heavy.

• When density or specific gravity is > 0.05, then the wood is heavy.

Hardness – Hardness refers to the strength of the wood also the resistance or the capacity of wood which can stand strong for a long time after being affected by several factors. 

Mechanical Properties of Wood

The mechanical properties of wood can be explained as the capability of wood to withstand externally applied forces. These include different types of properties to understand the strength, resistivity, elasticity, durability, etc. many more characteristics of wood. The mechanical properties of wood were further classified into two. One is strength properties and the other is elasticity properties. There are different standards available to check the strength of wood. They are – 

• ISO (International standard institution

• ISI (Indian standard Institution)

• BSI (British Standard Institution)

• PSI (Pakistan Standard Institution)

Compression – The compression of wood depends on the directions of applied forces, like – 

• perpendicular to wood grain

• parallel to wood grain, and 

• an angle to the wood grain.

Tension –  The tension is very effective on wood when it is parallel to the wood’s grain.

Bending – Based on the load put on the wood, bending may occur. It shows the strength and stability of wood even if the load is increased in a parallel direction.

Conclusion

Wood is one of the most important materials used for several household and commercial purposes. Different types of physical properties and mechanical properties of wood explain the characteristics of a particular type of wood. All these properties were generalized to all types of wood. Few differences may occur accordingly.

In subjects like physics the topic radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:

• The electromagnetic radiation, waves of radio, microwaves, infrared rays, visible light, ultraviolet rays, X-rays and gamma radiation i.e., γ.

• The particle radiation such as alpha radiation (α), beta radiation (denoted by β), proton radiation and neutron radiation

• The acoustic radiation  such as ultrasound and seismic waves  that is said to be dependent on a physical transmission medium

• The gravitational radiation that takes the form of gravitational waves or the ripples in the curvature of spacetime.

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Radiation Definition

The term radiation is often said to be categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation generally carries more than 10 eV which is enough to ionize the atoms and molecules and break chemical bonds. This is said to be a very important distinction which is due to the large difference in harmfulness to living organisms. Here a common source which is of ionizing radiation that is said to be radioactive materials that emit by symbols that are α, β, or γ radiation which consist of helium nuclei that is we can say that the electrons or the positrons and photons respectively. The other sources which generally include X-rays which is from medical radiography examinations and muons and the mesons, positrons, neutrons and other particles as well constitute the secondary cosmic rays that are produced after primary cosmic rays interact with the planet’s earth’s atmosphere.

So further down the spectrum which is said to be the non-ionizing lower energies of the lower ultraviolet spectrum that generally cannot ionize atoms.

But we can disrupt the interatomic bonds which form molecules thereby thereby breaking down molecules which are rather than atoms a good example which is sunburn which is generally caused by long-wavelength solar ultraviolet. The waves which are said to be  of longer wavelength than the lights which are the UV in visible light so the infrared and microwave frequencies which generally cannot break bonds but can cause vibrations which are in the bonds which are sensed as heat. So the radio wavelengths are generally not regarded as harmful to biological systems. So these are not sharp and delineations of the energies that we can say that there is some overlap in the effects of specific frequencies.

What is Radiation in Science

The word which is known as radiation which generally arises from the phenomenon of waves radiating that is traveling outward in all directions which is  from a source. This aspect usually leads to a system of measurements and physical units that are applicable to all types of radiation.  Like the law of any ideal gas law there is the inverse-square law that approximates a measured radiation intensity to the extent that the source which generally approximates a geometric point.

The term which is radiation with sufficiently high energy that can ionize atoms, that is to say it can knock electrons off atoms which are creating ions. The process of ionization occurs when an electron is stripped or we can say that when it is “knocked out” that too from an electron shell of the atom. 

This is said to be because of living cells and more importantly we can say that the DNA in those cells can be damaged by this ionization so the exposure which is to ionizing radiation is considered which is to increase the risk of cancer. Thus the process of “ionizing radiation” is somewhat artificially separated from particle radiation and electromagnetic radiation that is said to be simply due to its great potential for biological damage. While an individual cell is made of trillions of atoms only a small fraction of those will be ionized at low to moderate radiation powers. The probability of ionizing radiation that is generally causing the disease which is cancer is dependent upon the absorbed dose of the radiation.  It is a function of the damaging tendency which is of the type of radiation that is equivalent to dose and the sensitivity of the irradiated organism or tissue (effective dose).

What is Meant by Radiation

The exposure which is to the radiation that generally causes damage to living tissue that is high doses result in Acute radiation syndrome that is written as ARS with skin burns and then the hair loss that is the internal organ failure and death.

so while any dose may result in an increased chance of cancer and genetic damage and then a particular form of disease cancer thyroid that is cancer that it often occurs when nuclear weapons and reactors are the radiation source which is because of the biological proclivities of the radioactive iodine fission product which is known as iodine-131. However it is calculating the exact risk and chance of the disease which is cancer that is forming in cells caused by ionizing radiation is said to be still not well understood and currently estimates are loosely which is determined by population that is based data from the atomic bombings of Hiroshima and Nagasaki and from follow-up of reactor accidents that is such as the Chernobyl disaster. 

Our universe is one of the most mysterious and interesting thing existing out there in space. We know that our universe is constantly expanding like a hot air balloon. The universe is expanding and inflating regularly that we can barely notice. This expansion and inflation of the universe imply that the distance between the celestial objects is also increasing over the period of time!! I.e., the distant stars and galaxies are moving further away from the earth. This further results in the stretching of their light as they travel through space towards the earth. This stretching makes visible light look redder in shade, which is familiarly known as the cosmological redshift or redshift. 

Now let us have a look at these interesting concepts of redshift, redshift meaning, and redshift light with fascinating facts and concepts.

Redshift Meaning

The famous astronomer Edwin Hubble used the 2.5m which is about a 100-inch long telescope on Mount Wilson, California, to study observe and study the night sky. He found that some of the nebulae which were found to be quite fuzzy, luminous specks in the dark night sky were actually in fact galaxies, just like our milky way, even though every galaxy will be different and could be of widely varying sizes, each containing billions of stars. 

Very hot celestial objects (objects that are present in the outer atmosphere of the earth or space), such as stars are capable of generating visible light, which may travel a very long way before it strikes something. When we gaze at the stars at night, the light from the stars may have been travelling in a composed manner through space for more than hundreds of years. The light from the star strikes your eye and jiggling electrons in your retina, turns into electricity, which is sent along the optic nerve to your brain and hence we can see the star!! 

For thousands of years, human beings have been aspiring to understand the structure and nature of the Universe and seeking to determine its true extent. But, whereas ancient philosophers have believed that the world consisted of a disk, a ziggurat or a cube surrounded by many celestial oceans or some kind of ether (an organic substance), the turtle holding the universe and many more. Later the advancement of modern astronomy opened their eyes to new frontiers. By the 20th century, scientists and cosmologists have begun to understand just how vast (and maybe even unending) the Universe really is.

The universe is constantly expanding, inflating like a hot air balloon. This implies that the distant stars and galaxies are moving away from the earth. As a result of these transitions, it will stretch its light (light from the celestial bodies) as it travels through space towards us, the further it travels, the more it gets stretched. This stretching will make the objects appear red in colour, the more they travelled away they appear redder, and this effect is known as the redshift. 

Redshift is a key concept for astronomers. The term can be understood literally – the wavelength of the light is stretched, so the light is seen as ‘shifted’ towards the red part of the spectrum or redshift between the two spectral lines. 

Laboratory experiments that are performed here on the Earth have determined that each element in the periodic table emits photons only at certain wavelengths which are determined by the excitation state of the atoms. These emitted photons are manifest as either emission or absorption lines in the electromagnetic spectrum of an astronomical object, and by measuring the position of these spectral lines, we can determine which elements are present in the object itself or along the line of sight.

However, when astronomers perform this analysis, they note that for most astronomical objects, the observed spectral lines are all shifted to longer wavelengths, which is usually the red region of the spectrum. This is known as cosmological redshift or just redshift. 

The light or the photons emitted from the distant stars and more distant galaxies is not featureless but has distinct spectral features characteristic of the atoms in the gases around the stars. When these spectra are considered and examined, they are appeared to be shifted toward the red end of the electromagnetic spectrum. This shift is apparently a Doppler shift or Doppler effect and indicates that essentially all of the galaxies are moving further away from the earth over the period of time. 

Using the results from the nearest celestial objects, it becomes evident that the more distant galaxies and the stars are moving away from the earth at the highest accelerated rate. This is the kind of result one would expect for an expanding and inflating universe. The red line of the electromagnetic spectrum below is the transition from n=3 to n=2 of hydrogen and it is familiarly known as the H-alpha line seen throughout all the universe.

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Of course, making these measurements is a bit tedious and trickier than just saying that the star looks redder than it should be. Instead, astronomers and astrophysicists make use of markers in the electromagnetic spectrum of starlight. This is the actual study of spectroscopy. If you shine a flashlight beam through a clear prism, as a result of dispersion, we witness a rainbow emerging out the other side. But if you place a clear container filled with highly concentrated hydrogen gas between the flashlight and the clear prism, gaps appear in the smooth rainbow of colours, places where the light literally goes missing.

Redshift Light

When the universe was just a few minutes old, the surviving protons and neutrons recombined to form an atomic nucleus, mainly of what would become hydrogen and helium. The hydrogen and the helium that formed at a very early time in the universe are still charged, so fog remains impossible to see through. At this point, the foggy material is not unlike what we find inside a star, but of course, it fills the entire universe.

After the heavy uncontrollable action of the few minutes of existence, the universe stays much the same for the few hundred thousand years, continuing to expand and cool down, the hot fog becoming steadily thinner, dimmer, and redded as the wavelengths of light are stretched by the expansion of the universe.

After 380,000 years, when the part of the universe that we will eventually observe from the earth has grown to be millions of light-years across the fog finally clears. Due to the presence of electric charges of the electrons and the nuclei cancel each other out, the complete atoms are not charged so that now the photons can travel uninterrupted, which implies that the universe has slightly got transparent.

After this long wait for the fog clearance, what do we get to see or witness? Only fading red wavelengths scattered in all directions, which becomes redder and dimmer as the expansion of space continues to stretch the wavelengths of photons. Finally, light radiation ceases to be visible in all directions. The photons from that last glow have been travelling and stretched into space and even steadily appeared to be redder and these photons are detected now as Cosmic Background radiation and they are still arriving on earth from every direction in the sky.

Redshift is often compared to the high-pitched whine of an ambulance siren coming at you, which drops in pitch as the ambulance moves past you and then further away from you. That variation or change in the sound of an ambulance is due to what’s called the Doppler eff
ect. It’s a good comparison because both sound and light travel in the form of waves, which are affected by their movement through air and space.

Did You Know?

• The earth’s atmosphere has not always been as it is today. If we were able to travel 3.5 billion years (to the time when the earth was about one billion years old) we will not be able to breathe, due to the absence of oxygen and the presence of many toxic gases such as hydrogen, helium, etc…

• The atmosphere around 3.5 billion years ago contained no oxygen. It was mostly made of nitrogen, hydrogen, carbon dioxide and methane that are extremely poisonous gases present in the atmosphere, but the exact composition is still unknown. What is known, however, is the huge volcanic eruptions that occurred around the period of time, releasing extremely hot steam, carbon dioxide, ammonia and hydrogen sulphide into the atmosphere. We know that hydrogen sulphide odour is extremely strong and it is poisonous when encountered or subjected to large amounts.

• Now, the earth is the only planet in our solar system that is capable of holding living organisms. The earth is having an ideal atmosphere with appropriate composition of gases. Today, the atmosphere of the earth is made of approximately 78% of nitrogen, 21% of oxygen and around 0.93% of argon. The remaining 0.07% is mostly carbon dioxide which is approximately 0/04% and the mixture of neon, helium, methane, krypton and hydrogen.