Science 9 Unit E Section Science 9 Unit E Section 1.01.0

The Changing Understanding of The Changing Understanding of Earth and Space over timeEarth and Space over time

1.1 – Early Views1.1 – Early Views

People have watched the sky for People have watched the sky for thousands of yearsthousands of years

Through their observations of the Through their observations of the heavens, they discovered that the stars heavens, they discovered that the stars marked the passage of time and seasonsmarked the passage of time and seasons

Summer and winter Summer and winter solstices solstices (the days (the days that mark the start of summer and winter) that mark the start of summer and winter) were among the first dates to be identified were among the first dates to be identified using the starsusing the stars

Early great monuments often were used to Early great monuments often were used to either predict the coming of solstices and either predict the coming of solstices and the the equinoxesequinoxes (days where there are equal (days where there are equal amounts of light and dark), or to represent amounts of light and dark), or to represent the starsthe stars

Stonehenge was set up as a type of astrological calendar. In this diagram, the sun at the summer solstice shines on the altar stone

The Great Pyramids of Giza are aligned to The Great Pyramids of Giza are aligned to recreate part of the constellation Orionrecreate part of the constellation Orion

Overhead view of pyramids The constellation Orion

Models of Planetary MotionModels of Planetary Motion

About 2000 years ago, About 2000 years ago, Aristotle proposed a Aristotle proposed a geocentricgeocentric or “Earth or “Earth Centered Model” of the Centered Model” of the universeuniverse

He suggested that He suggested that planets orbited the planets orbited the Earth, and that the stars Earth, and that the stars were attached to a were attached to a “celestial sphere”“celestial sphere”

In 1530. Nicholas Copernicus proposed a In 1530. Nicholas Copernicus proposed a heliocentricheliocentric model of the universe, where model of the universe, where the Earth and other planets orbited the the Earth and other planets orbited the Sun.Sun.

Observations made with telescopes less Observations made with telescopes less than 100 years later and mathematical than 100 years later and mathematical work done by Johannes Kepler in fact work done by Johannes Kepler in fact confirmed that the orbits were ellipses, not confirmed that the orbits were ellipses, not circularcircular

This elliptical model could accurately This elliptical model could accurately describe and predict the motion of planetsdescribe and predict the motion of planets

1.2 – Discovery Through 1.2 – Discovery Through TechnologyTechnology

We use technological devices to help us We use technological devices to help us make measurements and observationsmake measurements and observations

In the late 16In the late 16thth Century, the telescope Century, the telescope allowed a closer view of nearby celestial allowed a closer view of nearby celestial objectsobjects

We now have very powerful optical and We now have very powerful optical and radio telescopes both on Earth and in orbitradio telescopes both on Earth and in orbit

Telescope TypesTelescope Types

Distance in SpaceDistance in Space

Distances in space are very large, so we Distances in space are very large, so we use different units of distance than we use different units of distance than we would here on Earthwould here on Earth

An An astronomical unit (AU)astronomical unit (AU) is equal to the is equal to the distance between the Earth and the Sun distance between the Earth and the Sun (about 149 599 000 km)(about 149 599 000 km)

AUs are used to measure distances within AUs are used to measure distances within the solar systemthe solar system

For interstellar distances, we use a unit For interstellar distances, we use a unit known as a known as a light yearlight year

A light year is the distance that light will A light year is the distance that light will travel in one year and is equal to about 9.5 travel in one year and is equal to about 9.5 trillion kmtrillion km

The star nearest to the Earth, Proxima The star nearest to the Earth, Proxima Centauri, is about 4 light years awayCentauri, is about 4 light years away

Time in SpaceTime in Space

Because the nearest celestial objects are far Because the nearest celestial objects are far away, it takes time for the light from them to away, it takes time for the light from them to reach usreach us

The light from the Sun takes about 8 minutes to The light from the Sun takes about 8 minutes to reach the Earth, so if we stare at the Sun we are reach the Earth, so if we stare at the Sun we are effectively looking 8 minutes back in timeeffectively looking 8 minutes back in time

That means that stars that are very far away That means that stars that are very far away may die out before their light reaches usmay die out before their light reaches us

1.3 – The Distribution of Matter in 1.3 – The Distribution of Matter in SpaceSpace

Stars are a hot, glowing ball of gas that Stars are a hot, glowing ball of gas that gives off electromagnetic radiationgives off electromagnetic radiation

Stars can vary in colour, size, density and Stars can vary in colour, size, density and temperaturetemperature

As well, stars change over timeAs well, stars change over time

This diagram shows the expected life of a This diagram shows the expected life of a star such as the Sunstar such as the Sun

The Birth of a StarThe Birth of a Star

Stars form in clouds of dust and gas known as Stars form in clouds of dust and gas known as nebulaenebulae

The gravitational attraction between the particles The gravitational attraction between the particles creates a small ball of matter, and draws in more creates a small ball of matter, and draws in more dust and gasdust and gas

As this occurs, the As this occurs, the protostarprotostar’s temperature ’s temperature increases and it begins to glowincreases and it begins to glow

At temperatures above 10 000 000 At temperatures above 10 000 000 ooC, hydrogen C, hydrogen atoms begin the process of fusion, and a star atoms begin the process of fusion, and a star formsforms

The Death of a StarThe Death of a Star

As the fuel in a star dwindles, it becomes a As the fuel in a star dwindles, it becomes a red giant red giant starstar

Eventually the fusion reaction stops and Eventually the fusion reaction stops and the star collapses to form a the star collapses to form a white dwarfwhite dwarf starstar

Very massive stars collapse rapidly, Very massive stars collapse rapidly, creating a massive shock wave known as creating a massive shock wave known as a a supernovasupernova

If there is still matter If there is still matter left from the exploding left from the exploding star, a star, a black holeblack hole is is formedformed

Black holes are very Black holes are very dense and their dense and their gravitational field even gravitational field even prevents light from prevents light from leavingleaving

Black holes can be Black holes can be identified by the trail of identified by the trail of stellar matter being stellar matter being pulled into thempulled into them

Star GroupsStar Groups

Constellations Constellations are groups of stars that are groups of stars that appear as patterns in the skyappear as patterns in the sky

You are probably familiar with some of You are probably familiar with some of these:these:

Galaxies Galaxies are groupings of millions or are groupings of millions or billions of stars that are held together by billions of stars that are held together by gravitygravity

Galaxies may be elliptical or irregularGalaxies may be elliptical or irregular

Spiral Elliptical Irregular

1.4 – Our Solar Neighborhood1.4 – Our Solar Neighborhood

It is believed that the planets formed from It is believed that the planets formed from leftover dust and gas that did not become leftover dust and gas that did not become part of our Sunpart of our Sun

We’ll take a look at each of our planets:We’ll take a look at each of our planets:

The Solar SystemThe Solar System

MercuryMercury Most of what we know about Mercury has been Most of what we know about Mercury has been

determined by telescopes and satellite data. determined by telescopes and satellite data. Mercury is the closest planet to the Sun. Its Mercury is the closest planet to the Sun. Its surface is very similar to that of the Moon. Like surface is very similar to that of the Moon. Like the Moon, Mercury has no atmosphere and the Moon, Mercury has no atmosphere and therefore no protection from the bombardment of therefore no protection from the bombardment of meteoroids, asteroids, and comets. The scars of meteoroids, asteroids, and comets. The scars of millions of years of impacts can be seen. Other millions of years of impacts can be seen. Other parts of Mercury’s surface are smooth, probably parts of Mercury’s surface are smooth, probably due to lava flowing through cracks in the rocky due to lava flowing through cracks in the rocky crust. The temperatures on Mercury vary greatly, crust. The temperatures on Mercury vary greatly, from over 400°C on the sunny side to –180°C on from over 400°C on the sunny side to –180°C on the dark side. the dark side.

VenusVenus

Venus is similar to Earth in diameter, mass, and gravity, and is often Venus is similar to Earth in diameter, mass, and gravity, and is often called Earth’s twin. A closer look at conditions on Venus’s surface called Earth’s twin. A closer look at conditions on Venus’s surface shows where the similarities end. Venus would be horrific for shows where the similarities end. Venus would be horrific for humans to visit. Surface temperatures are kept hot due to a humans to visit. Surface temperatures are kept hot due to a greenhouse effect caused by thick clouds. Temperatures can be greenhouse effect caused by thick clouds. Temperatures can be over 450°C—hot enough to melt lead. The atmospheric pressure is over 450°C—hot enough to melt lead. The atmospheric pressure is about 90 times that on Earth. The surface of Venus cannot be seen about 90 times that on Earth. The surface of Venus cannot be seen by telescope because of its thick cloud cover. The permanent by telescope because of its thick cloud cover. The permanent clouds are made of carbon dioxide, and it often rains sulfuric acid clouds are made of carbon dioxide, and it often rains sulfuric acid (the same acid found in a car battery). Russians landed a probe on (the same acid found in a car battery). Russians landed a probe on Venus in 1982, but it only lasted there for 57 min. In 1991, the Venus in 1982, but it only lasted there for 57 min. In 1991, the spacecraft spacecraft MagellanMagellan mapped Venus using radio waves (radar). It mapped Venus using radio waves (radar). It found huge canyons, extinct volcanoes, and ancient lava flows. found huge canyons, extinct volcanoes, and ancient lava flows. Venus is one of the only planets in the solar system to rotate from Venus is one of the only planets in the solar system to rotate from east to west—opposite to the other six. east to west—opposite to the other six.

EarthEarth

Earth is unique in the solar system for several Earth is unique in the solar system for several reasons. It is the only planet where water exists reasons. It is the only planet where water exists in all three phases: solid, liquid, and gas. It is in all three phases: solid, liquid, and gas. It is also the only planet that is at the appropriate also the only planet that is at the appropriate distance from the Sun to support life as we know distance from the Sun to support life as we know it. As well, Earth’s atmosphere provides it. As well, Earth’s atmosphere provides protection from cosmic rays and ultraviolet protection from cosmic rays and ultraviolet radiation that would otherwise harm life. Seventy radiation that would otherwise harm life. Seventy percent of the planet’s surface is covered in percent of the planet’s surface is covered in water. Earth is one of the few places in our solar water. Earth is one of the few places in our solar system that has active volcanism.system that has active volcanism.

MarsMars

Mars has been studied by telescope for centuries. Two Mars has been studied by telescope for centuries. Two missions have successfully landed robotic probes on the missions have successfully landed robotic probes on the surface of the planet: surface of the planet: VikingViking in 1976 and in 1976 and Mars PathfinderMars Pathfinder in 1997. Mars is often referred to as the “red planet,” in 1997. Mars is often referred to as the “red planet,” though it is actually more orangey. This is caused by the though it is actually more orangey. This is caused by the iron oxides on the planet’s surface. Mars has two polar iron oxides on the planet’s surface. Mars has two polar ice caps, one made up of frozen carbon dioxide and ice caps, one made up of frozen carbon dioxide and water, the other of just carbon dioxide. The atmosphere water, the other of just carbon dioxide. The atmosphere is very thin and composed mainly of carbon dioxide. is very thin and composed mainly of carbon dioxide. Although the average surface temperature is extremely Although the average surface temperature is extremely cold, temperatures at Mars’s equator can reach 16°C in cold, temperatures at Mars’s equator can reach 16°C in the summer. Like Venus and Earth, Mars has canyons, the summer. Like Venus and Earth, Mars has canyons, valleys, and extinct volcanoes. Mars also has two small valleys, and extinct volcanoes. Mars also has two small moons, Phobos and Deimos.moons, Phobos and Deimos.

JupiterJupiter

Jupiter has been observed through telescopes Jupiter has been observed through telescopes since the 1600s. The since the 1600s. The VoyagerVoyager probes visited probes visited Jupiter and many of its 16 moons in 1979, Jupiter and many of its 16 moons in 1979, followed by the followed by the GalileoGalileo probe in the probe in themid-1990s. Jupiter is the largest of all the mid-1990s. Jupiter is the largest of all the planets in the solar system, and contains more planets in the solar system, and contains more than twice the mass of all the other planets than twice the mass of all the other planets combined. It is a gas giant composed mainly of combined. It is a gas giant composed mainly of hydrogen and helium, and scientists speculate hydrogen and helium, and scientists speculate that if Jupiter were only 10 times larger than it is, that if Jupiter were only 10 times larger than it is, it may have formed into a star. The Great Red it may have formed into a star. The Great Red Spot on Jupiter is a huge storm in its Spot on Jupiter is a huge storm in its atmosphere. Jupiter has three very thin rings.atmosphere. Jupiter has three very thin rings.

SaturnSaturn

Galileo saw Saturn’s rings with his primitive telescope in Galileo saw Saturn’s rings with his primitive telescope in 1610, though he initially thought they were a group of 1610, though he initially thought they were a group of planets. planets. Voyager 1Voyager 1 and and 22 flew by Saturn in 1980 and flew by Saturn in 1980 and 1981, respectively. In late 2004, the 1981, respectively. In late 2004, the CassiniCassini spacecraft spacecraft will reach Saturn and drop a probe onto Titan, the largest will reach Saturn and drop a probe onto Titan, the largest of the planet’s 19 moons. Saturn is the second largest of the planet’s 19 moons. Saturn is the second largest planet in our solar system and has the most distinctive planet in our solar system and has the most distinctive ring system of all the nine planets. Over a thousand rings ring system of all the nine planets. Over a thousand rings exist, composed of pieces of ice and dust that range in exist, composed of pieces of ice and dust that range in size from grains of sand to house-sized blocks. Saturn’s size from grains of sand to house-sized blocks. Saturn’s composition is similar to Jupiter’s—mostly hydrogen and composition is similar to Jupiter’s—mostly hydrogen and helium. Because of the planet’s quick rotation, wind helium. Because of the planet’s quick rotation, wind speeds at Saturn’s equator have been estimated at over speeds at Saturn’s equator have been estimated at over 1800 km/h.1800 km/h.

UranusUranus

Voyager 2Voyager 2 has given us most of our close-up has given us most of our close-up information about Uranus, last sending data information about Uranus, last sending data back to Earth in 1986 before it left the solar back to Earth in 1986 before it left the solar system. Satellite and telescope analyses have system. Satellite and telescope analyses have provided other interesting details. Uranus has provided other interesting details. Uranus has one of the most unusual rotations in the solar one of the most unusual rotations in the solar system: its axis of rotation is tilted toward the system: its axis of rotation is tilted toward the plane of its orbit, making it appear to roll during plane of its orbit, making it appear to roll during its orbit. Another gas giant, Uranus is composed its orbit. Another gas giant, Uranus is composed mainly of hydrogen and helium. Methane in its mainly of hydrogen and helium. Methane in its atmosphere gives the planet a distinctive blue atmosphere gives the planet a distinctive blue colour. Uranus has a large ring system, and 17 colour. Uranus has a large ring system, and 17 moons.moons.

NeptuneNeptune

When scientists observed the orbit of Uranus to be When scientists observed the orbit of Uranus to be different from what they had calculated, they searched different from what they had calculated, they searched for an eighth planet. In 1846, they found Neptune. About for an eighth planet. In 1846, they found Neptune. About a century and a half later, a century and a half later, Voyager 2Voyager 2 flew to Neptune to flew to Neptune to collect more information. The composition and size of collect more information. The composition and size of Neptune make it very similar in appearance to Uranus. Neptune make it very similar in appearance to Uranus. Another gas giant composed of hydrogen, helium, and Another gas giant composed of hydrogen, helium, and methane, Neptune (like Uranus) is bluish in colour. Very methane, Neptune (like Uranus) is bluish in colour. Very little of the Sun’s energy reaches the eighth planet. little of the Sun’s energy reaches the eighth planet. Neptune gives off about 3 times more energy than it Neptune gives off about 3 times more energy than it receives. It boasts the fastest wind speeds in the solar receives. It boasts the fastest wind speeds in the solar system, at 2500 km/h. Like all the other gas giants, system, at 2500 km/h. Like all the other gas giants, Neptune has its own ring system, as well as eight Neptune has its own ring system, as well as eight moons.moons.

PlutoPluto

Pluto was discovered by telescope in 1930. Since then, the most Pluto was discovered by telescope in 1930. Since then, the most useful information about it has come from the Hubble Space useful information about it has come from the Hubble Space Telescope. One of the greatest debates among planetary Telescope. One of the greatest debates among planetary astronomers currently is whether Pluto is a planet or not. It is a astronomers currently is whether Pluto is a planet or not. It is a frozen ball of methane smaller than our moon. It doesn’t fit the frozen ball of methane smaller than our moon. It doesn’t fit the pattern of the outer planets, which tend to be large and gaseous, pattern of the outer planets, which tend to be large and gaseous, and it isn’t rocky like the terrestrial planets. Pluto’s orbit is raised and it isn’t rocky like the terrestrial planets. Pluto’s orbit is raised 17.2° from the plane of the other planets and is more elliptical than 17.2° from the plane of the other planets and is more elliptical than that of other planets. Like Venus and Uranus, Pluto rotates from that of other planets. Like Venus and Uranus, Pluto rotates from east to west. Between 1979 and 1999, Pluto was closer to the Sun east to west. Between 1979 and 1999, Pluto was closer to the Sun than Neptune. Some astronomers believe that Pluto and its moon, than Neptune. Some astronomers believe that Pluto and its moon, Charon, are comets captured by the Sun’s gravity from the area of Charon, are comets captured by the Sun’s gravity from the area of debris on the outer edge of the solar system called the Kuiper Belt.debris on the outer edge of the solar system called the Kuiper Belt.

Asteroids and CometsAsteroids and Comets

Asteroids are rocky or metallic bodies that Asteroids are rocky or metallic bodies that travel through spacetravel through space

They may range in size from a few meters They may range in size from a few meters across to over 1000 km wideacross to over 1000 km wide

Comets consist of balls of ice and rock Comets consist of balls of ice and rock that travel in long elliptical orbits around that travel in long elliptical orbits around the Sunthe Sun

As the comet nears the Sun, it heats up As the comet nears the Sun, it heats up and boils, releasing gas in a tail that can and boils, releasing gas in a tail that can be millions of kilometers longbe millions of kilometers long

1.5 – Describing the Position of 1.5 – Describing the Position of Objects in SpaceObjects in Space

We describe the position of objects by using the We describe the position of objects by using the measurements known as measurements known as azimuth azimuth and and altitudealtitude

The azimuth describes the compass heading to The azimuth describes the compass heading to the object (North is 0the object (North is 0oo))

The altitude describes the angle of the object The altitude describes the angle of the object relative to the horizonrelative to the horizon

These measurements must also have a time These measurements must also have a time associated with them, as the stars move as the associated with them, as the stars move as the Earth rotatesEarth rotates

Note that azimuth is measured from North in a clockwise direction

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