The Four Fundamental Forces of Nature are Gravitational force, Weak Nuclear force, Electromagnetic force and Strong Nuclear force. The Four Fundamental Forces of Nature are Gravitational force, Weak Nuclear force, Electromagnetic force and Strong Nuclear force.

Gravitational Force

The gravitational force is weak but very long-ranged. Furthermore, it is always attractive. It acts between any two pieces of matter in the Universe since mass is its source.

Weak Nuclear Force

The weak force is responsible for radioactive decay and neutrino interactions. It has a very short range and. As its name indicates, it is very weak. The weak force causes Beta-decay ie. the conversion of a neutron into a proton, an electron and an antineutrino.

Electromagnetic Force

The electromagnetic force causes electric and magnetic effects such as the repulsion between like electrical charges or the interaction of bar magnets. It is long-ranged but much weaker than the strong force. It can be attractive or repulsive and acts only between pieces of matter carrying an electrical charge. Electricity, magnetism, and light are all produced by this force.

Strong Nuclear Force

The strong interaction is very strong but very short-ranged. It is responsible for holding the nuclei of atoms together. It is basically attractive but can be effectively repulsive in some circumstances. The strong force is ‘carried’ by particles called gluons; that is, when two particles interact through the strong force, they do so by exchanging gluons. Thus, the quarks inside of the protons and neutrons are bound together by the exchange of the strong nuclear force.

Note:  While they are close together the quarks experience little force, but as they separate the force between them grows rapidly, pulling them back together. To separate two quarks completely would require far more energy than any possible particle accelerator could provide.

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The surface of Earth is broken into giant fragments called tectonic plates. The continents are situated on top of these tectonic plates, which carry them much like cargo on rafts. The plates move at rates of between 2 and 17 cm per year, and over millions of years this moves the continents over many thousands of kilometres.

The earth’s crust is broken into separate pieces called tectonic plates. The crust is the solid, rocky, outer shell of the planet. It is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. Both types of crust rest atop solid, upper mantle material. The upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

Each tectonic plate is free-floating and can move independently. Earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. The term fault is used to describe the boundary between tectonic plates. Most of the earthquakes and volcanoes around the Pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. Other observable results of short-term plate movement include the gradual widening of the Great Rift lakes in eastern Africa and the rising of the Himalayan Mountain range. The motion of plates can be described in four general patterns:

  • Collision: when two continental plates are shoved together
  • Subduction: when one plate plunges beneath another
  • Spreading: when two plates are pushed apart
  • Transform faulting: when two plates slide past each other


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Life on our planet developed millions of years ago, but if large life-forms are taken into consideration, then intelligent organisms like the Homo sapiens have never dominated any specific era or even a period. The Cenozoic Era can be known as the arrival and dominance of intelligent life-forms like modern human beings, which changed the world scenario permanently.

The term 'Cenozoic' has been derived from the Greek words: kainos meaning 'new' and zoe meaning 'life'. It is the shortest era of the Earth, spanning from about 66 million years ago to the present. After the sudden K-T boundary mass extinction, mammals got a chance to evolve extensively in this era, and hence, it is also called 'The Age of The Mammals'. The climate of our planet stabilized and atmospheric oxygen slowly increases with a simultaneous decrease in carbon dioxide and other toxic gaseous elements.

Earlier, the Cenozoic comprised two periods: Tertiary and Quaternary, the former being divided into Paleogene and Neogene, but now the term Tertiary is slowly phased out. Instead, the era is now divided into three periods: Paleogene, Neogene, and Quaternary, ranging from the oldest to the youngest. They are again subdivided into a number of stages/epochs. Apart from mammals, the Aves class of Chordates, i.e., the birds also evolved a lot, and several of them were larger than the average height of a human.

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Earth is the third planet from the Sun in our Solar System. From a distance, it looks like a great, round, blue jewel hanging in the darkness of space. It is blue because three-quarters of its rocky surface is submerged under blue, ocean waters, which shimmer in the light of the Sun.

The way light reflects off air molecules has an effect on the way people see the sky as well as the ocean. When orbiting the Earth, satellites and astronauts see a blue globe due to some of these same properties. The sheer amount of water on Earth makes it appear blue in these instances, but there are other factors as well.

Scattering in the Atmosphere

The atmosphere is predominantly made of two gases, nitrogen and oxygen. These molecules absorb and scatter, or radiate, different kinds of light. Red, yellow and orange light have longer wavelengths that are not affected by as much by atmospheric gases, so they are not absorbed, but blue light is scattered and radiated, creating the blue sky you see every day. That blue light is not as visible from space, but plays a role in the blue color of the Earth. At night, the sunlight no longer is around to interact with the gases, so the sky become black.

Water Coverage

The Earth has many oceans and seas, from the Arctic Ocean to the Southern Ocean. Although there is red-hot heat below the surface of the Earth, the top layer is dominated by water. The oceans cover about 71 percent of the Earth and are blue, while land makes up the other 29 percent and varies in color, from green to tan to white. This gives the Earth the appearance of a blue marble. If the planet consisted mainly of land masses, it would be appear to be a different color completely.

Water Color

Although water covers a large percentage of the Earth, it is important to understand why the water is blue as well. As with the Earth's atmosphere, most of the colors of the light spectrum are absorbed by the water. The water radiates the blue in the spectrum, giving it its blue color. If another color were radiated, say red for instance, the Earth would look red from outer space, like Mars. The land masses of the Earth do not look blue due to this same principle.

Some Contradictions

The Earth only appears blue if you are looking at it from outer space on the side that is being lit by the sun. When you are orbiting the Earth, it will appear black when you orbit around a part of the Earth that is experiencing night. Because there is no sun to create the light, all of the Earth will appear somewhat dark. The stars will be more visible as well during this period. Land masses will appear somewhat dark blue, as there are artificial light sources that illuminate the sky on land.

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Yes, Earth spins around a line between the poles called its axis. The axis is tilted over at 23.5° in relation to the Sun. Earth rotates once every 23 hours, 56 minutes and 4.09 seconds. The Sun thus appears to come back to the same place in the sky once every 24 hours.

Earth’s spin, tilt, and orbit affect the amount of solar energy received by any particular region of the globe, depending on latitude, time of day, and time of year. Small changes in the angle of Earth’s tilt and the shape of its orbit around the Sun cause changes in climate over a span of 10,000 to 100,000 years, and are not causing climate change today.

Daily changes in light and temperature are caused by the rotation of the Earth, and seasonal changes are caused by the tilt of the Earth. As the Earth orbits the Sun, the Earth is pulled by the gravitational forces of the Sun, Moon, and large planets in the solar system, primarily Jupiter and Saturn. Over long periods of time, the gravitational pull of other members of our solar system slowly change Earth’s spin, tilt, and orbit. Over approximately 100,000 – 400,000 years, gravitational forces slowly change Earth’s orbit between more circular and elliptical shapes. Over 19,000 – 24,000 years, the direction of Earth’s tilt shifts (spins). Additionally, how much Earth’s axis is tilted towards or away from the Sun changes through time, over approximately 41,000 year cycles. Small changes in Earth’s spin, tilt, and orbit over these long periods of time can change the amount of sunlight received (and therefore absorbed and re-radiated) by different parts of the Earth. Over 10s to 100s of thousands of years, these small changes in the position of the Earth in relationship to the Sun can change the amount of solar radiation, also known as insolation, received by different parts of the Earth. In turn, changes in insolation over these long periods of time can change regional climates and the length and intensity of the seasons. The Earth’s spin, tilt, and orbit continue to change today, but do not explain the current rapid climate change.


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