Physics Tutorial: Earth and Other Celestial Bodies

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In this Physics tutorial, you will learn:

  • What are celestial bodies? How do they move?
  • What is Solar System? What celestial bodies does it contain?
  • What are stars/galaxies/universe?
  • What are planets? What common features do they share?
  • How planets are classified? What is the main difference that has brought in this classification?
  • What are the main features of each individual planet?
  • What are the main features of natural satellites?
  • What are asteroids/meteors/comets and their main features?
  • How to calculate the distance of a given planet from the Sun?

Introduction

As a species, we have been aware of the existence of planets for thousands of years and they have played a key part in our everyday lives and our evolution. Astronomy, the science that deals with celestial bodies, is one of the oldest branches of physics. The Earth itself is a planet, a type of celestial body, yet scientists only realized this fact many centuries after discovering and observing other planets. It is very interesting that people knew many properties of other planets, including the period of revolution, position, spherical shape etc., but believed that the Earth to be different from all the other celestial bodies. They assumed that it was flat in shape. An entire theory was produced based on this false assumption - a theory that obviously was overthrown by famous scientists during the last period of Middle Age and Renaissance.

In this tutorial, we will discuss key questions relating to Astronomy including: What celestial bodies are made of? How do they move? How far are they from each other and from the Sun? and many other interesting questions that have been the most important and challenging questions for humanity for a long time.

Background

Nowadays, almost everyone knows that:

The Earth is a planet that belongs to a Solar System - a system of linked celestial bodies revolving around the Sun (the source of energy for the entire system), which is a common star. The Sun looks much brighter than other stars just because it is closer to us. Other components of the solar system include: planets, natural satellites, asteroids, comets and meteors.

The Sun on the other hand, belongs to a system of billions of linked stars (and all the other celestial bodies linked to each individual star). Such a system is known as a "galaxy". Our solar system is a tiny part of this gigantic system where the galaxy we belong to is known as the Milky Way. All galaxies together form the Universe.

Earth and Planets

Planets are big spherical-shaped celestial bodies that revolve around the Sun. The trajectory of planets is known as their orbit and each orbit has an elliptic shape. In other words, the orbit represents the path followed by a planet during their revolution around the Sun. Planets are visible because they reflect the light incident from the Sun. In ancient times, people were able to identify six planets: Mercury, Venus, Mars, Jupiter, Saturn and obviously, the Earth. The other two planets, Uranus and Neptune were discovered in recent centuries as well as Pluto, which until a few years ago was considered as a planet but now it is not classified as such anymore due to its small dimensions. The following figure represents a simplified illustration of the solar system.

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All planets of the solar system have been explored using space probes. However, humans have not been able to physically travel to any of them due to the large distance and technical difficulties though there are asperations for humans to travel to the planets within our solar system and beyond once technological advances permit this..

Earthy and Giant Planets

The planets of the solar system are classified in two categories: earthy planets (Mercury, Venus, Earth and Mars) and giant planets (Jupiter, Saturn, Uranus and Neptune).

Giant Planets are farther from the Sun than earthy ones and have a lower density than earthy ones. They can be considered as gaseous gigantic balls floating in space, held together by the high gravity produced by the gas itself. Matter in a solid state exists only in their center (core). Giant planets are mainly composed by hydrogen and helium.

Earthy Planets are closer to the Sun and are relatively small compared to giant ones. These planets are enveloped by a solid core (ground) and contain heavier materials than hydrogen and helium. Most metals we know are found under their surface.

The reason why giant planets are the farthest and earthy (solid) planets are the closest to the Sun is because kinetic energy of composing particles (gas) in farthest planets is very small due to low temperatures (recall the direct relationship between temperature and kinetic energy of particles in Section 13). It is a much smaller gravitational potential energy that keeps them connected. As a result, giant planets retain gaseous components within close proximity, unlike earthy planets in which most of the gaseous components have already dissipated due to their high kinetic energy from the higher temperatures of the environment. Hence, only the solid core composed by heavy elements is left which makes these planets smaller but harder. Earthy planets are mainly composed by Silicon, Carbon, Aluminum, Calcium and Magnesium as well as other heavy components but in smaller varying amounts. Therefore, The Earth for example is hundreds times lighter than Jupiter, as most of the Earths gaseous material dissipated in space long ago.

Main Features of Planets

Now, let's take a closer look at some general features of each planet starting with the earthy planets.

The Earth

The Earth is the most special planet in the Solar System because it contains water, oxygen in free state and it provides the right conditions to support life. Moreover, the Earth manifests tectonic activity, in the sense that its giant plates are dynamic, i.e. they shift in respect to each other. The Earth has a gaseous protective layer (known as atmosphere) of about 100 kilometers thick that is composed by Nitrogen (78%), Oxygen (21%) and other gases, mainly Carbon Dioxide (1%). The range of temperatures in inhabited areas ranges from -20° C to +40° C (-4° F to +104° C) with an average of +15° C but there are exceptions where temperature values extend beyond this range during specific times of the year (extreme weather conditions).

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About 71 percent of the Earth's surface is water-covered (the rest is covered by soil), and the oceans hold about 96.5 percent of all the Earth's water. We take the sea-level as reference for the surface of the Earth. The Earth contains a large number of mountains which rise up to a few kilometres above sea level and deep oceans extending a few kilometres below the sea level.

The radius of Earth is 6378 km from its' centre to sea-level. The Mass of earth is 5.91 × 1024 kg and the average density is 5500 kg/m3.

Mercury

Mercury is a planet without an atmosphere. This is because it is the closest planet to the Sun and due to the high temperature of its' environment all gaseous material dissipated a long time ago. There is no geological or technical activity on the surface of Mercury, which is covered by craters. The craters are not produced by volcanos but from continuous bombardment from meteors. Note that, unlike Mercury, meteors do not impact the Earth's surface as atmosphere melts them down during their descent towards the planet.

Due to the lack of atmosphere, mercury temperatures have a wide range of values. Thus, during the day they can reach the value of +430° C while during the night they fall at -180°C.

Mercury has a yellowish color due to its closen proximity to the Sun thought the original color is similar to that of Earth. This reduces its visibility because the Sun color is dominant.

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The radius of Mercury is 2439 km and its mass is 0.055 MEarth or 3.25 × 1023 kg. The average density of Mercury is 5420 kg/m3.

Venus

Venus (also known as the morning star) is the most visible planet on the sky. It looks as the brightest star in early morning and after the sunset. This is why people have always thought it is a star, not a planet. Venus has a very thick atmosphere (about 100 times thicker than that of Earth) composed mainly by Carbon Dioxide. The large clouds keep the heat inside the atmosphere producing a very intense greenhouse effect. As a result, the temperature of Venus is very high (471° C on average, with very low variations). The high temperature and atmospheric pressure prevent it from supporting the creation of any living forms.

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From a geological viewpoint, Venus is as active as the Earth. A number of space probes (more than 20 so far) have entered the atmosphere of Venus for exploration purposes but without touching its surface because of the high temperatures.

The dimensions of Venus are very close to Earth (Venus is slightly smaller). The radius of Venus is 6057 km and its mass is 4.87 × 1024 kg (0.815 MEarth). The density of Venus is 5240 kg/m3.

Mars

Mars is also known as the "red planet" due to its appearance, the predominant red colour is due to the presence of iron oxide.

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There is an intense meteorological activity on Mars. There are considerable variations of temperature in different seasons of the year but usually they vary from -150° C during the night to +20° C during the day where the average value is -30° C. Mars surface is covered by mountains and craters; there are continuous ice melting and freezing processes occurring on its surface.

For a long time, Mars has been considered as the twin planet of Earth and scientists believed that there might be suitable living conditions on it. However, closer studies performed on Mars surface using spatial probes have excluded this possibility. Recently, it was discovered that the conditions on Mars are very hostile to life. There is no water steam in its atmosphere (which is much thinner than the atmosphere on Earth), there is too little water on its surface, temperature variations are large, etc.

Mars atmosphere is mainly composed of carbon dioxide (95%), molecular nitrogen (2.8%) and argon (2%).

As for geological activity, Mars lies in-between the Earth (which has high geological activity) and Mercury (no geological activity).

Mars has a mass of 6.417 × 1023 kg, a radius of 3389.5 km and an average density of 3933 kg/m3.

Now, let's discuss some basic features of giant planets. They are Jupiter, Saturn, Uranus and Neptune, as explained earlier.

Jupiter

Jupiter has an atmosphere made up predominantly of hydrogen which accounts for 90 percent of the atmosphere. Most of the remaining 10 percent is composed of helium. A very small fraction of the atmosphere is made up of compounds such as ammonia, sulfur, methane, and water vapor. The atmosphere is very stirring, with continuous whirlpools, cyclones and other strong winds.

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Jupiter is a cold planet due to its longer distance from Sun compared to earthy planets. The average temperature on the surface of Jupiter is -145° C.

Jupiter's mass is 1.898 × 1027 kg, its radius is 71 492 km and the average density is 1326 kg/m3. Jupiter is the largest and heaviest planet of our Solar System. It is 2.5 times heavier than all the other planets altogether. If Jupiter was 10 times larger than its actual size, our Solar System would have two stars.

Saturn

Saturn is a special planet as it is surrounded by a gaseous ring that produces a unique view. Since Saturn is a gaseous planet, its atmosphere (mainly composed by hydrogen and helium) is similar to that of Jupiter, with whirlpools etc.

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Saturn is the second biggest planet of our Solar System. The radius of Saturn is 60 268 km and its mass is 5.6834 × 1026 kg. The average density of Saturn is 690 kg/m3.

Saturn is very cold; its average temperature on the surface is -178° C despite it has a hot interior, reaching 11,700° C at its core, and radiates 2.5 times more energy into space than it receives from the Sun.

Uranus

Uranus is the third gaseous giant planet of our Solar System. Uranus' atmosphere is predominantly made up of hydrogen and helium. Unlike Jupiter and Saturn, these light gases dominate the outer edges of the planet but are not a significant contributor to the rocky interior. The dull blue color of Uranus is caused by the presence of methane, which absorbs red light.

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The radius of Uranus is 24 973 km and its mass is 8.681 × 1025 kg. Uranus has a density of 1270 kg/m3.

Uranus is very cold as it is very far from the Sun. The average temperature of Uranus is -195° C.

Neptune

Neptune is the farthest planet from the Sun in our Solar System. Neptune's atmosphere is similar to all the large planets in the Solar System; it mostly consists of hydrogen and helium, with trace amounts of methane, water, ammonia and other ices. Unlike the other gas planets in the Solar System, Neptune's atmosphere has a larger proportion of the ices due to its long distance from the Sun.

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The radius of Neptune is 24 341 km and its mass is 1.02 × 1026,/sup> kg, having a density of 1638 kg/m3.

Neptune is a the coldest planet. Its average temperature is -201° C.

There are many other features associated with certain planets besides those mentioned above, these include: period of revolution around the Sun (the time necessary to make one complete revolution around the Sun) which determines the year duration of that planet, period of rotation around itself (which determines the day duration), the average distance from the Sun, inclination (the angle in degree formed by the equator and planetary orbit), etc. They are summarized in the table below.

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Example 1

Calculate the volume of Earth using geometrical methods and confirm this result using the value of mass and density from the table.

Solution 1

Assuming the Earth is a perfect sphere, we can calculate its volume:

V = 4/3 π ∙ R3

where R = 6378 km = 6.378 × 106 m is the average radius of the Earth, we obtain the Earth's volume:

V = 4/3 π ∙ R3
= 4/3 ∙ 3.14 ∙ (6.378 × 106 )3
= 1.08 × 1021 m3

When using the equation

ρ = M/V

where ρ = 5515 kg/m3 is the average density of the Earth and M = 5.91 × 1024 kg is its mass, we obtain for the volume V of Earth:

V = M/p
= 5.91 × 1024 kg/5.515 × 103 kg/m3
= 1.08 × 1021 m3

As you see, both methods give the same result.

Pluto

Pluto is another important celestial body which was considered until a few years ago as the ninth planet of our Solar System (it is now considered as a "dwarf planet"). It is the farthest one from the Sun (distance = 5.9135 billion km, radius = 1662 km, mass = 0.002 MEarth). Pluto is an icy celestial body with an average density of 2200 kg/m3 and an average temperature of -229° C.

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The Moon and Other Natural Satellites

Natural satellites are celestial bodies revolving around specific planets. Nowadays, there are 218 natural satellites documented so far that revolve around the 8 planets of our Solar System. Mercury and Venus have no natural satellites while Jupiter has more artificial satellites than all the other planets (79). Artificial satellites have various features; their diameters vary from a few kilometers to several thousand kilometers. They have different densities; some of them have an atmosphere and others do not; some of them have a surface covered by craters and others have a smooth surface; some of them have no geological activity while in some others intense geological activity such as volcanos and geysers are very common.

The smallest natural satellites have irregular shapes; they look like rocks detached from the surface of Earth. On the other hand, larger natural satellites have a planet-like spherical shape.

Natural satellites revolve around their corresponding planet and always display the same face to it. The only exception in this regard is Hyperon - a natural satellite of Saturn.

Moving on, we will briefly discuss the most relevant natural satellites that have been studied most frequently.

a. The Moon is the only natural satellite of Earth

The Moon is the only natural satellite of Earth. We often use the term "moon" to describe natural satellites of other planets as well. The Moon has neither atmosphere nor geological activity. The Moon makes a complete revolution around the Earth in 27.32 days and it always shows the same face to Earth.

There are two types of Moon surfaces that are visible from Earth: bright regions (continents), which in fact are surfaces covered by craters, and dark regions (seas), which in fact are flat areas.

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The dark region of the Moon has also been explored recently by space probes. The Moon is the only celestial body reached by humans. On July 20, 1969 humans (Neil Armstrong & Co.) landed on the Moon for the first time.

The Moon has a radius of 1737.5 km and it weighs 7.3 × 1022 kg (about 81 times lighter than Earth). The average density of the Moon is 3346 kg/m3. It is 384 000 km away from Earth.

b. Natural satellites of Mars

Mars has two natural satellites: the innermost one called Phobos (it has a radius of about 5.5 km) and the outermost one called Deimos (its radius is about 3 km). They revolve very fast around the parent planet (Mars). Phobos completes one revolution in 7h 39min while Deimos completes one revolution around Mars in 30h 19min.

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Phobos and Deimos are very small and they are irregularly-shaped. They do not have any atmosphere or geological activity and are very close to Mars (Phobos is 9400 km away from Mars while Deimos is 23 400 km away from it.

c. Natural satellites of Jupiter

As stated earlier, there are 79 known natural satellites (moons) of Jupiter. The largest of these are the four Galilean moons: Io, Europa, Ganymede and Calisto, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither the Earth nor the Sun.

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Io is very active from the geological viewpoint; it has 8 active volcanos. It has a radius of 1821 km and is 422 000 km away from Jupiter. Europe on the other hand, has a very smooth surface. Its radius is 1515 km and it is 671 000 km away from Jupiter. Ganymede is the largest moon of Jupiter; it contains a large number of ups and downs on the surface and is 1,070,000 km away from Jupiter having a radius of 2630 km. Last, Calisto has a radius of 2400 km and a distance of 1,883,000 km from Jupiter.

d. Natural satellites of Saturn

Nowadays, there are 62 natural satellites of Saturn are confirmed, most of which were discovered only recently and, at the time of writing this tutorial, are still unnamed. The largest moons of Saturn are Titan (radius = 2575 km), Rhea (radius = 764 km) and Iapetus (radius = 718 km). The corresponding distances from Saturn are: d(Titan) = 1,221,800 km, d(Rhea) = 527,100 km and d(Iapetus) = 3,560,800 km. Another interesting moon of Saturn is Hyperion. It is a small moon (radius = 133 km) but it has a special feature: Hyperion shows all faces to its parent planet (Saturn) unlike all the other natural satellites, which always show the same face to their planet. However, the motion of Hyperion is chaotic.

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Titan is very similar to Earth. Like Earth, it has an atmosphere composed mainly by Nitrogen, an atmospheric pressure very close to that of Earth and it contains complex organic molecules that are ready to produce living organisms. The only drawback of Titan is that it has a very low temperature (-200° C). Iapetus has two distinct faces: one is black due to strikes from other satellites of Saturn and the other is completely white. Rhea's features could be divided into two regions: the first being heavily cratered (bright) terrain with craters larger than 25 miles (40 kilometers) across and a second type of area in parts of the polar and equatorial region with craters less than 25 miles (40 kilometers) across.

e. Natural satellites of Uranus

Uranus currently has 27 known satellites. Uranus's moons are divided into three groups: thirteen inner moons, five major moons, and nine irregular moons. The most known of them is Miranda (radius = 235 km). Other satellites of Uranus include Ariel (radius = 580 km), Titania (radius = 789 km), Oberon (radius = 761 km) and Umbriel (radius = 585 km). All of them are very cold and without any considerable geological activity.

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f. Natural satellites of Neptune

Neptune has 14 known natural satellites, the most famous of which is Triton (radius = 1352 km). The other satellites of Neptune have much smaller dimension (the second largest is Proteus having a radius of 210 km). All of them are cold and without any notable geological activity or favorable conditions for life.

Other Celestial Bodies in the Solar System

There are other types of celestial bodies besides planets and natural satellites floating on the space of our Solar System. They include:

a. Asteroids

Asteroids are small celestial bodies revolving around the Sun. They are the leftovers from the formation of our solar system about 4.6 billion years ago. Over 150 million asteroids larger than 100 m are estimated to be actually floating throughout the space of our Solar System.

The difference between asteroids and moons is that asteroids do not pertain to any planet, instead they only revolve around the Sun. On the other hand, they cannot be planets either, due to their small dimensions.

Most asteroids present in our Solar System are located between Mars and Jupiter in a region known as the asteroid belt. The greatest of them is called Ceres; it has a radius of 500 km.

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Asteroids are classified in three groups based on their matter composition. They are C-, S-, and M-types.

  1. The C-type (chondrite) asteroids are most common. They probably consist of clay and silicate rocks, and are dark in appearance.
  2. The S-types ("stony") are made up of silicate materials and nickel-iron.
  3. The M-types are metallic (nickel-iron).

When an asteroid enters the Earths' atmosphere, it heats up because of friction with air and eventually burns out producing a moving light in the sky. In scientific terms, they are called meteors while in popular terminology they are known as falling stars.

Asteroids with a 1 km (0.62 mi) diameter strike Earth every 500,000 years on average. Large collisions - with 5 km (3 mi) objects - happen approximately once every twenty million years.

There is a formula known as Titius-Bode Law used to predict the distance between a planet and its corresponding star in any given solar system. The formula suggests that, extending outward, each planet should be approximately twice as far from the star as the one before. Its mathematical form when applied is our Solar System is

D(n) = 3 x 2n + 4/10 (au)

where n = minus infinity for Mercury, n = 0 for Venus, n = 1 for Earth, n = 2 for Mars, n = 3 for Jupiter, n = 4 for Saturn, n = 5 for Uranus and n = 6 for Neptune. This distance is measured in au (au stands for astronomical unit = 150 million km that represents a rounded value of Sun-Earth distance). The formula fits perfectly for the first 5 planets but lacks accuracy for the next three.

The original formula was slightly different where the number n = 5 was missing in the list and the counting started from n = 1. This was an indication that a planet is missing between Mars and Jupiter. Giving that the asteroids belt corresponds to this section of space, we conclude that these asteroids either derive from a destroyed planet or they represent a new planet not formed yet. Then, the formula of Titius-Bode Law was corrected to take the actual form.

Example 2

Calculate the distance from Sun to Mars in astronomical units and then express this value in kilometres.

Solution 2

Mars is the fourth planet of our solar system (n = 2). Thus, we obtain for the Sun-Jupiter distance by applying the Titius-Bode law:

D(n) = 3 × 22 + 4/10 (au)
= 1.6 au
= 1.6 × 150 million km
= 210 million km

This value is close (but not perfect) to the actual value (227.9 million km) calculated with modern tools

Comets

Comets are celestial bodies made up of various material's and ices mixed with space dust. They have diameters ranging from a few hundred meters to several tens of kilometers. Comets revolve around the Sun following stretched orbits. When a comet gets closer to the Sun, its temperature increases; the frozen ice begins to evaporate. As a result, a long bright cloud is formed around the nucleus of comet, forming a bright tail behind it.

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When a comet approaches the Sun at a distance comparable to the distance of Earth from the Sun, the tail elongates up to several ten millions of kilometers producing an amazing view. The most famous comet is Halley comet, which is visible from Earth one in about 76 years (the last time being in 1986). It will be visible again in mid-2061.

Summary

The Earth is a planet that belongs to a Solar System - a system of linked celestial bodies revolving around the Sun (the source of energy for the entire system), which is a common star. Other components of the solar system include: planets, natural satellites, asteroids, comets and meteors.

The Sun itelf, belongs to a system of billions of linked stars (and all the other celestial bodies linked to each individual star). This type of system is known as a "galaxy". Our solar system is a tiny part of this gigantic system where the galaxy we belong to is known as the Milky Way. All galaxies together form the Universe.

Planets are big spherical shaped celestial bodies that revolve around the Sun. The trajectory of planets is known as its' orbit and it has an elliptic shape.

Our Solar System has the Sun as source of energy and 8 planets revolving around it: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto is no longer considered a planet.

The planets of the solar system are classified in two categories: earthy planets (Mercury, Venus, Earth and Mars) and giant planets (Jupiter, Saturn, Uranus and Neptune). Each planet has its own special features.

Giant Planets are farther from the Sun than earthy ones. Giant planets have lower density that earthy ones. They can be considered as gaseous gigantic balls floating in space held together by the high gravity produced by the gas itself. Matter in solid state exists only in their center (core). Giant planets are mainly composed of hydrogen and helium.

Earthy Planets are closer to the Sun. These planets are relatively small compared to giant ones. They are enveloped by a solid core (ground) and contain heavier materials than hydrogen and helium. Most metals we know are found under their surface.

Natural satellites are celestial bodies revolving around specific planets. Currently, there are 218 known natural satellites that revolve around the 8 planets of our Solar System. Mercury and Venus have no natural satellites while Jupiter has more artificial satellites than all the other planets (79).

The smallest natural satellites have irregular shapes; they look like rocks detached from the surface of Earth while larger ones have a planet-like spherical shape.

There are other types of celestial bodies besides planets and natural satellites floating on the space of our Solar System. They include

Asteroids which are small celestial bodies not linked to any planet that revolve around the Sun. Most asteroids in our Solar System are found between Mars and Jupiter, in a zone known as the asteroid belt. The asteroid belt occupies the space where there once was (or there will one day be) a planet.

Asteroids are classified in three groups based on their matter composition. They are C-, S-, and M-types.

  1. The C-type (chondrite) asteroids are most common. They probably consist of clay and silicate rocks, and are dark in appearance.
  2. The S-types ("stony") are made up of silicate materials and nickel-iron.
  3. The M-types are metallic (nickel-iron).

When an asteroid enters the Earths' atmosphere, it heats up due to the friction with air and eventually burns out producing a moving light in the sky. In scientific terms, they are called meteors while in popular terminology they are known as falling stars.

There is a formula known as Titius-Bode Law which is used to predict the distance between a planet and its corresponding star in any given solar system. The formula suggests that, extending outward, each planet should be approximately twice as far from the star as the one before. Its mathematical form when applied is our Solar System is

D(n) = 3 x 2n + 4/10 (au)

where n = minus infinity for Mercury, n = 0 for Venus, n = 1 for Earth, n = 2 for Mars, n = 3 for Jupiter, n = 4 for Saturn, n = 5 for Uranus and n = 6 for Neptune. This distance is measured in au (au stands for astronomical unit = 150 million km that represents a rounded value of Sun-Earth distance). The formula fits perfectly for the first 5 planets but lacks accuracy for the next three.

Comets are celestial bodies made up of various material's and ices mixed with space dust. They have diameters ranging from a few hundred meters to several tens of kilometers. Comets revolve around the Sun following stretched orbits. When a comet get closer to the Sun, its temperature increases; the frozen ice begins to evaporate. As a result, a long bright cloud is formed around the nucleus of comet, forming a bright tail behind it. When a comet approaches the Sun at a distance comparable to the distance of the Earth from the Sun, the tail elongates up to several ten millions of kilometers producing an amazing view.

Earth and Other Celestial Bodies Revision Questions

1. Calculate the revolving speed of Moon around the Earth in km/h if the distance Earth-Moon is 384 000 km and period of Moon revolution around the Earth is 27.32 days.

  1. 3678 km/h
  2. 1022 km/h
  3. 589 km/h
  4. 14056 km/h

Correct Answer: A

2. What is the volume of Mercury if its average density is 5420 kg/m3 and its mass is 0.325 × 1024 kg?

  1. 6 × 1020 m3
  2. 1020 m3
  3. 1.67 × 1019 m3
  4. 6 × 1019 m3

Correct Answer: D

3. Calculate the distance Venus-Sun in kilometres using the Titius-Bode formula.

  1. 400 000 km
  2. 60 000 000 km
  3. 105 000 000 km
  4. 150 000 000 km

Correct Answer: C

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