Astronomy • Astronomy is the science that studies the universe • Astronomy deals with the proper2es of objects in space and the laws under which the universe operates • The Greeks were the first to study the stars & use philosophical arguments to explain natural events
Earth • Earth is one of nine planets & many smaller bodies that orbit the sun • The sun is part of our larger galaxy, the Milky Way • Scien2sts used to think that they Earth was the center of the universe, but we now know that is not true • Scien2sts also thought that the Earth was flat....
Geocentric • The Greeks believed in a geocentric view: they thought the Earth was a sphere that stayed mo2onless at the center of the universe • In the geocentric model, the moon, sun, and known planets (Mercury, Venus, Mars, and Jupiter) orbit Earth
Heliocentric • In a heliocentric model, the sun is the center of the universe; Earth & other planets orbit the sun • Greek scien2st, Aristarchus, developed this theory • Although mathema2cal evidence supported this theory, the earth-‐centered or geocentric model dominated Western thought for nearly 2000 years
Ptolemaic • Claudius Ptolemy was a Greek astronomer who presented a model of the universe known as the Ptolemaic system • In the model, the planets move in circular orbits around a mo2onless Earth • Developed retrograde mo9on: the apparent westward mo2on of the planets with respect to the stars
Modern astronomy • Nicolaus Copernicus (Polish – Middle ages): concluded that Earth was a planet and proposed a model of the solar system with the sun at the center • Tycho Brahe (Danish – 1600) Observed the planets & made more accurate predic2ons, esp. of Mars, using instruments • Johannes Kepler (Brahe’s mentee) discovered three laws of planetary mo2on
Kepler’s laws • Using Brahe’s calcula2ons, Kepler determined that Mar’s orbit is not a perfect circle but rather an oval-‐shaped path called an ellipse • Also no2ced that as Mars approached the sun, its speed increased & slowed down as it moved away from the sun
Kepler’s laws
① The path of each planet around the sun is an ellipse, with the sun at one focus – the other focus is symmetrically located at the opposite end of the ellipse (law of Ellipses) ② Each planet revolves so that an imaginary line connec2ng it to the sun sweeps over equal areas in equal 2me intervals – planets move more quickly near the sun & slower farther from the sun (law of Equal Areas) ③ The length of 2me it takes a planet to orbit the sun is propor2onal to its distance from the sun (the law of Harmonies)
Astronomical units • When measuring these distances, scien2sts use astronomical units (AU) • The average distance between Earth and the sun is about 150 million kilometers
Galileo Galilei
• Greatest Italian scien2st of the Renaissance • Most important contribu2ons were his descrip2ons of the behavior of moving objects • Galileo constructed his own telescope that magnified objects three 2mes the size seen by the unaided eye
Galileo Galilei
• Contribu2ons/Discoveries
1. Four satellites (moons) orbi2ng Jupiter (therefore, Earth was not the only center of mo2on) 2. Planets are circular disks and are Earth-‐like 3. Venus has phases just like the moon – so Venus must orbit the sun 4. The moon’s surface is not smooth 5. The sun has sun spots (dark regions)
Sir Isaac Newton
• The first scien2st to formulate and test the law of universal gravita9on • According the Newton, every body in the universe ahracts every other body with a force that is directly propor2onal to their masses and inversely propor2onal to the square of the distance between their centers of mass • Gravita9onal force decreases with distance • Greater the mass, greater the gravita9onal force
Sir Isaac Newton
• The mass of an object is the total about of maher it contains • Mass is NOT the same as weight • Weight is a measure of the force of gravity ac2ng on an object • Weight is expressed in newtons (N) • Supported Kepler’s theory of ellip2cal orbits
The motion of the Earth
• The two main mo2ons of the Earth are rota2on and revolu2on
– Rota9on is the turning or spinning of a body on its axis – Revolu9on is the mo2on of a body, such as a planet or moon, along a path around some point in space
• How long is Earth rota2on? 24 hours • How long is Earth’s revolu2on? 365 days
revolution • Earth’s average distance from the sun is about 150 million kilometers • Because Earth’s orbit is an ellipse (an oval) its distance from the sun varies • At perihelion, Earth is closest to the sun & occurs on about Jan. 3rd each year (winter for us) • At aphelion, Earth is farthest from the sun & occurs about July 4th (summer for us) • Earth is closest to the sun in Jan. & farthest away in July
Perihelion & Aphelion
• At perihelion, Earth is closest to the sun & occurs on about Jan. 3rd each year (winter for us) • At aphelion, Earth is farthest from the sun & occurs about July 4th (summer for us)
What about the seasons? • Earth’s axis of rota9on is 9lted about 23.5 degrees, which allows for our seasons
Earth’s Axial Tilt
• During summer in the northern hemisphere, Earth’s axis is 2lted so that Earth’s north pole is 2lted towards the Sun (farthest away from the sun) – The northern hemisphere thus experiences more sunlight & warmth • During the winter, the northern hemisphere is 2lted away from the sun and is colder (closer to the sun)
Solstice & Equinox • A sols9ce is a day when Earth’s rota2on axis is the most toward or away from the Sun • An equinox is a day when Earth’s rota2onal axis is leaning along Earth’s orbit, neither toward or away from the Sun
Solstice & Equinox
Seasons on Earth: NH
• It may be opposite than you think: • In the N.H., summer is when the earth is farthest away from the sun but IS 2lted towards it • In the N.H., winter is when the Earth is closest to the sun but IS 2lted away
Seasons on Earth: SH
• However, it’s different in the Southern Hemisphere & can make its season more severe An image of much of the Southern • When the earth is far Hemisphere from Antarc2ca away from the sun, the • Fewer land masses & S.H. is also 2lted away more water (80%) • When the earth is close • South pole is colder than the North pole to the sun, the S.H. is • Water helps regulate also 2lted closer the temperature
Precession
• Precession is the slight movement, over a period of 26,000 years, of Earth’s axis
Precession
• Precession is a very slow movement o Over a 26,000 year cycle, the Earth’s axis traces a circle in the sky o The difference in Earth’s 2lt is very slight & doesn’t really affect the seasons but we will not no2ce in our life 2me
Nutation • Nuta9on is a rocking, swaying, or nodding mo2on in the axis of rota2on • In the case of Earth, the principal sources of 2dal force are the Sun and Moon, which con2nuously change loca2on rela2ve to each other & cause nuta2on in Earth's axis • The largest component of Earth's nuta2on has a period of 18.6 years
Nutation
• Nuta9on is a rocking, swaying, or nodding mo2on in the axis of rota2on during precession
Earth and the Moon • Earth has one natural satellite, the moon – A natural satellite, or moon, is a celes2al body that orbits another body, e.g. a planet, which is called its primary
• The moon orbits Earth in about one month – Perigee: the point when the moon is closest to Earth – Apogee: the point when the moon is farthest from Earth
Earth and the Moon • At perigee, the moon appears larger (because it’s closer) • At perigee, the 2des can be higher or greater varia2ons in high & low 2de due to more gravita9onal pull
Phases of the Moon • On a monthly basis, we observe the phases of the moon as a change in the amount of the moon that appears lit • Lunar phases are a result of... the mo9on of the moon and the sunlight that is reflected from its surface
Phases of the Moon
• Half of the moon is light at all 2mes, but we can’t always see that • The % of the bright side that is visible depends on the loca9on of the moon with respect to the sun and Earth o When the moon lies between the sun and Earth, none of its bright side faces Earth (new moon) o When the moon lies on the side of Earth opposite of the sun, all of its bright side shows (full moon)
Solar Eclipse
• Early Greeks realized that eclipses are simply shadow effects • When the moon moves directly between the Earth and the sun, it casts a dark shadow on Earth producing a solar eclipse – Occurs during the new moon phase (not every 2me)
Lunar Eclipse
• When the moon moves within Earth’s shadow (Earth is between the sun & moon), it produces a lunar eclipse – Occurs during the full moon phases (not every 2me) – The moon appear reddish because of red light waves/ sunlight that is filtered & refracted (being bent) through our atmosphere
The Earth’s Moon • The Earth has hundreds of man-‐made satellites orbi2ng around it, but only ONE natural satellite – our moon • Our moon is prehy large (about ¼ the size of Earth, its parent planet) • Much of what we know about the moon is due to the Apollo moon missions – The 6 missions took place between 1969 and 1972
• The gravita2onal ahrac2on on the moon is 1/6 that of Earth – So if I weigh 150 lbs on Earth, I’ll only weigh 25 pounds on the moon!
Surface of the moon • The moon’s surface hasn’t really changed in the past 3 billion years because it doesn’t experience erosion like we do on Earth
• Why? Because the moon has no atmosphere or water, no wind, no moving plates nothing – The only thing that affects its appearance is 2ny par2cles from space that con2nuously bombard its surface (gradually smoothing the landscape)
Surface of the moon • The most obvious features of the lunar surface are craters: round depression in the surface of the moon • Most craters were produced by the impact of rapidly moving debris • Why doesn’t the Earth have as many craters as the moon? Our atmosphere creates friction that burns up most debris before it reaches the Earth’s surface
Earth’s Movement: Review rotates on its axis (24 hours) • The Earth _________
• The Earth _revolves ______ around the sun (365 days)
• The slight movement of Earth’s axis is called precession and occurs over a 26,000 year _________ period
• Earth only has one natural satellite, which is the ________ moon
Practice Exam ?s
1. Which statement describes the mo2on of Earth around the sun? a. The speed of Earth is constant regardless of its distance from the sun b. The speed of Earth is constant because the distance remains the same between Earth and the sun c. Speed increases the farther Earth is from the sun and decreases the closer it is to the sun d. Speed increases the closer Earth is to the sun and decreases the farther it is from the sun
Practice Exam ?s
2. If it is summer in the northern hemisphere, which statement is true? a. Earth has changed the 2lt of its axis by 20 degress due to its revolu2on b. It is winter in the southern hemisphere due to the 2lt of Earth’s axis c. It is summer in the southern hemisphere due to the 2lt of Earth’s axis d. Earth has reached its closest point to the sun due to its revolu2on
Summary • Summary should be @ least 5 sentences. • Include the words: rota9on, revolu9on, precession, nuta9on, perihelion, aphelion, moon, lunar phases • Rephrase ideas in your own words J
Oreo Moon Phase Lab • •
You will work with your table partner You will need: – 7 Oreos – A paper plate – A pen/Sharpie – A plas9c spoon/knife
Oreo Moon Phase Lab • • • •
Draw the sun on the right side of your plate Draw the earth in the center of the plate Open an Oreo and place the new moon and full moon Now complete the other moon phases from memory & label
Oreo Moon Phase Lab
Rotation & Revolution Review
Precession
• Precession is the slight movement, over a period of 26,000 years, of Earth’s axis • Precession: change in direc2on of the axis, but without any change in 2lt (23.5) • This changes the stars near (or not near) the Pole, but does not affect the seasons
Precession
•
•
•
At the present 2me, the axis points toward the bright star Polaris (the current North Star or pole star).
In about 13,000 years, the direc2on will shiw to point toward the star Vega and this will than become the pole star. The period of precession, the amount of 2me for the axis to complete one cycle, is 26,000 years.
Nutation • Nuta9on is a rocking, swaying, or nodding mo2on in the axis of rota2on • In the case of Earth, the principal sources of 2dal force are the Sun and Moon, which con2nuously change loca2on rela2ve to each other & cause nuta2on in Earth's axis • The largest component of Earth's nuta2on has a period of 18.6 years
Nutation
• Nuta9on is a rocking, swaying, or nodding mo2on in the axis of rota2on during precession
Barycenter • The barycenter is point in space around which two objects orbit
• For the Moon and Earth, that point is about 1000 miles (1700 km) beneath your feet, or about three-‐quarters of the way from the Earth’s center to its surface. • That means the Earth actually wobbles around a point deep in its interior, pulled around by the Moon
Barycenter • The barycenter is located closer to the... more massive object
Barycenter • So, the moon doesn’t just orbit the Earth – the Earth also orbits the moon
• Both the Earth & Moon orbit around their barycenter
Barycenter • The same thing happens for the Sun and all the planets. • We think of the Sun sixng s2ll in the center of the solar system while the planets whiz around. • But, in reality, the Sun is wobbling too, orbi2ng the barycenter of the solar system.
Barycenter
Barycenter • Can think of it like a see-‐saw • If we have the same mass, we can sit equal distance from the center of the see-‐saw • That point where we balance is like the barycenter • If you weigh 50 lbs and Sally Sue weighs 200 lbs, the Sally Sue will need to sit closer to the center in order to balance out the forces
Barycenter - seesaw • If we were to put the moon and the Earth on a huge see-‐saw, what would happen?
• In the situa2on above, what would we have to do to make the see-‐saw balanced?
Barycenter – The sun • The Sun is not sta2onary in our solar system • It actually moves as the planets tug on it, causing it to orbit the solar system's barycenter • The Sun never strays too far from the solar system barycenter
The sun - motion
• The sun, like other nearby stars, revolves around the Milky Way Galaxy • This trip around the galaxy takes about 226 millions years at speed reaching 250 km per second
The Galaxy - motion • The galaxies themselves are also in mo2on • The Milky Way Galaxy is presently approaching one of it’s nearest galac2c neighbors, the Andromeda Galaxy • The mo2ons of Earth are many & complex and it’s speed through space is very great
Our Solar System • The sun is the center of a huge rota2ng system of planets, their satellites, and many smaller bodies • An es2mated 99.85 percent of our solar system is made up of the mass of our sun • The planets collec2vely make up most of the remaining 0.15 percent
Our Solar System • An es2mated 99.85% of our solar system is made up of the mass of our sun
• Can you name all of the planets in order from the sun?
Our Planets • • • • • • • • •
My: Mercury Very: Venus Eager: Earth Mother: Mars Just: Jupiter Served: Saturn Us: Uranus Nachos: Neptune *Lihle Pluto!*
Our Planets - Mercury • Guided by the sun’s gravita2onal force, each planet moves in an ellip2cal orbit, and all travel in the same direc2on • The nearest planet to the sun, Mercury, has the fastest orbit at 48 km/s • It also has the shortest period of revolu2on at 88 days (compared to our 365)
Our Planets - Neptune
• In contrast, the farthest planet from the sun, Neptune, has an orbital speed of 5 km/s and takes 165 years to make 1 revolu2on around the sun – the longest of any planet
Earth’s & Moon • The Earth has one natural satellite, the moon • The moon affects much life on Earth, including the 9des
Earth’s Tides
• Tides are daily changes in the eleva2on of the ocean surface • Tides were not well explained un2l Sir Isaac Newton applied the law of gravita9on to them • Newton showed that there is a mutual ahrac2ve force between two bodies, as between Earth and the moon (gravity) • Ocean 9des result from the gravita9onal a`rac9on exerted upon Earth by the..... moon and to a lesser extent by the sun
Earth’s Tides (moon & sun) • The primary body that influences the 2des is the moon • The moon makes run complete revolu2on around the Earth every 29½ days • The sun can also influence the 2des • The sun is far larger than the moon, but because it is farther away, its effect is considerably less – The sun’s 2de-‐genera2ng effect is only about 46% of the moon’s
Earth’s Tides
• So, the force that produces 2des is _gravity _____ • Gravity is the force that ahracts Earth & the moon to each other • On the side of the Earth closest to the moon, the force of the moon’s gravity is greater & water is pulled in the direc2on of the moon and produces a 9dal bulge
Earth’s Tides
• Iner9a is the tendency of an object to resist a change in mo2on (at rest, stay at rest...in mo2on, stay in mo2on in @ same speed & in the given direc2on)
Tidal Bulges & Rotation
• Because the posi2on of the moon changes only slightly during a single day, the 2dal bulges remain in place while Earth rotates “through them” • If you stand in the ocean for 24 hours, Earth will rotate you through alterna2ng areas of high & low water • As you are carried into the bulge, water rises & then you experience the troughs in between
Tides & The Sun
• Most places experience 2 high 2des & 2 low 2des each day • Now, even though the sun is farther away than the moon, it s2ll has a lihle effect on the 2des • The sun produces smaller 2dal bulges • When the moon & sun are aligned, their forces combine and the 9des are larger! (high high 9des & lower low 9des)
Spring & Neap Tides
Spring Tides
• The 9dal range is the difference in height between successive high & low 2des • Spring 9des are 2des that have the greatest 2dal range to due the alignment of the Earth-‐moon-‐sun system • Occurs during both new moon & full moon
Neap Tides
• Neap 9des occur when the 2dal range is much less – Occurs when the moon is at 1st quarter & 3rd (last) quarter – The gravita2onal forces of the sun & the moon are at right angles – Their forces then par2ally offset each other & the 2dal range is LESS
Neap Tides
• Neap 9des occur when the 2dal range is much less
Practice Exam ? 1. How does a straight alignment between Earth, the sun, and the moon impact the 2des on Earth? a. It produces the greatest change in high & low 2des b. It produces the least change in high & low 2des c. It produces semidiurnal 2des d. It produces diurnal 2des
Just in case you want to know..
• A diurnal 9de pahern is characterized by a single high 2de & a single low 2de each 2dal day (occurs @ the gulf of Mexico) • A semidiurnal 9de exhibits 2 high 2des & 2 low 2des each 2dal day (Atlan2c coast of the US)
Stop & Jot --- think about it • What would happen if there was no moon?
• With the Moon no longer there, the oceans of the world become much calmer. The Sun s2ll has an effect on them, so surfers wouldn’t be completely devoid of waves. But the oceans would largely become serene. • The loss of the Moon directly affects the Earth’s orbit, rota2on and wobble. Without the Moon to act as a stabiliser, the Earth begins to wobble more and more, sending our seasons into turmoil and changing our orbit around the Sun from slightly ellip2cal to massively ellip2cal. We now swing around the Sun in a wild, unstable, fluctua2ng orbit.
Earth Quick facts & Size
• average distance of 92,955,820 miles (149,597,890 km) • 3rd planet from the sun • Formed about 4.5-‐4.6 billion years ago • Only planet known to sustain life • At the equator, Earth's circumference is 24,901.55 miles (40,075.16 km) • Earth's diameter slightly smaller at the poles o At poles: 7,899.80 miles (12,713.5 km) o At Equator: 7,926.28 miles (12,756.1 km)
Earth’s Shape – not a sphere • Earth's circumference and diameter differ because its shape is classified as an oblate spheroid or ellipsoid, instead of a true sphere • This means that instead of being of equal circumference in all areas, the poles are squished, resul2ng in a bulge at the equator, and thus a larger circumference and diameter there
Earth’s Shape – centrifugal force • Because Earth rotates, this sphere is distorted by the centrifugal force • This is the force that causes objects to move outward away from the center of gravity • Therefore, as the Earth rotates, centrifugal force is greatest at the equator so it causes a slight outward bulge there • Thus, that region (equator) has a larger circumference and diameter
Happy Wednesday September 3rd 2014 Direc9ons: For your catalyst, answer the ques2on: How does our moon affect our 2des? Today’s Objec9ve: EEn.1.1.2 Explain how
the Earth’s rota2on and revolu2on about the Sun affect its shape and is related to seasons and 2des..
Practice Exam ?s
1. Which statement describes the mo2on of Earth around the sun? a. The speed of Earth is constant regardless of its distance from the sun b. The speed of Earth is constant because the distance remains the same between Earth and the sun c. Speed increases the farther Earth is from the sun and decreases the closer it is to the sun d. Speed increases the closer Earth is to the sun and decreases the farther it is from the sun
Practice Exam ?s
2. If it is summer in the northern hemisphere, which statement is true? a. Earth has changed the 2lt of its axis by 20 degress due to its revolu2on b. It is winter in the southern hemisphere due to the 2lt of Earth’s axis c. It is summer in the southern hemisphere due to the 2lt of Earth’s axis d. Earth has reached its closest point to the sun due to its revolu2on
Our Galaxy
• Galaxies are groups of stars, dust, and gases held together by gravity • Our galaxy is call the _Milky _________ Way • Is our galaxy @ the center of the universe? Probably not – forest analogy ______________________________ • There are billions are galaxies in the universe, each containing hundreds of billions of stars
Our Galaxy
• Galaxies are groups of stars, dust, and gases held together
Earth & The Sun
• So, in the Milky Way, we have our Earth and the Sun • Like we’ve learned, the Earth _rotates ________ on its axis every 24 hours and revolves around the sun every ________ 365 days • We know that when the Earth is farthest away from the sun, the northern hemisphere summer (Aphelion) experiences __________ • When the Earth is close to the sun, it is 2lted away and experiences _winter ______
Earth’s Revolution: Facts
• The speed of our orbit around the sun is 108,000 km/h • The planet travels 940 million km during one orbit • The Earth is never the same distance from the Sun from day to day
More about the Seasons
• The seasons are caused by a combina2on of two factors – The Earth’s axial 2lt – Its distance from the Sun during the orbital period • When we experience summer in the NH, people experience winter in the SH and vice versa
Solstice & Equinox
More about the ellipse
• The shape of Earth’s orbit isn’t quite a perfect circle • It is more like a “stretched out” circle or an oval. • Mathema2cians and astronomers call this shape an _ellipse ______
What’s a galaxy? (Review) • A galaxy is a collec2on of billions of stars • Our galaxy is spiral shaped • The name for our galaxy is the Milky Way • Our galaxy is full of billions of stars • A star is a large ball of gas held together by gravity
Energy production in stars • Most of the energy produced in stars results from nuclear fusion • Energy is defined as the ability to do work – Work is a transfer of energy (applying a force to move an object in the direc2on of the force)
• Energy is can travel in the form of waves (which we will see on the electromagne2c spectrum)
Energy production in stars • Most of the energy produced in stars results from nuclear fusion • Nuclear fusion is the combina9on of the nuclei of smaller elements to form the nuclei of larger elements • The sun converts hydrogen into helium • Nuclear fusion can only occur at extremely high temperatures & high pressure condi2ons like those found in star interiors
More about stars • Luminosity of a star measures how bright it would be • The SUN is an average-‐sized star • Stars originate from clouds of gas & dust • Gravity causes these gas & dust clouds to clump up • When the mass becomes large enough, gravita2onal contrac2on results in high enough temps. & pressure to start nuclear fusion
Fusion vs fission
• Like the stars, the sun also produces energy by nuclear fusion • What’s the difference in fusion & fission? – Fusion • Par2cles “fuse” together to create energy • Found on the sun & stars – Fission • Par2cles split to create energy • Found in nuclear reactors splixng atoms to create energy
Nuclear fission • Fission: the splixng of an atomic nucleus into two smaller pieces • In nuclear fission, tremendous amounts of energy can be produced from very small amounts of mass
Nuclear fission • One reac2on leads to a series of others • In a chain reac9on, neutrons released during the splixng of an ini2al nucleus trigger a series of nuclear fissions
• In order to sustain the series, each nucleus that is split must produce on neutron that causes the fission of another nucleus
Nuclear fission • Cri9cal mass is the smallest possible mass of a fissionable material that can sustain a chain rxn • Nuclear power plants generate about 20% of the electricity in the U.S. • In a power plant, controlled fission of uranium-‐235 occurs in a vessel called a fission reactor
Nuclear fusion • Fusion is process in which the nuclei of two atoms combine to form a larger nucleus • Like fission, some of the reactant mass is converted into energy • The sun and other stars are powered by the fusion of hydrogen into helium
Nuclear fusion • Requires extremely high temperatures • At these temperatures, maher exists as plasma • Plasma is a state of maher in which atoms have been stripped of their electrons
Nuclear fusion • May one day be an efficient and clean source of energy
Scien2sts are face with 2 main problems when designing a fusion reactor: Need to achieve very high temperatures to start the rxn
Must contain the plasma
Fusion vs fission ____________ combining of two or more atoms into a larger one
_________ splitting of an atom into two smaller ones
Occurs in stars, like the_____ sun Doesn’t normally occur in nature
high temperature and Cri9cal mass of the substance ______ plasma are required and high-‐speed neutrons are Energy released is 3-‐4 9mes greater than the energy released by fission
not used as a source of _____ energy
required Energy released is a million 9mes greater than that released in chemical rxns Used to power nuclear power plants & generate electricity __________
Sun – Fusion – Energy • Solar energy can be changed into chemical energy through photosynthesis • Plants use sunlight to produce sugar through the ac2ons of the chlorophyll • Chemical formula:
§ 6H2O + 6CO2 -‐-‐-‐-‐> C6H12O6+ 6O2
Photosynthesis
What’s Radiation?
• So, the sun’s energy is created through fusion of hydrogen & helium • The sun’s energy reaches the Earth through the process of radia9on • Radia9on is the transfer of energy by waves traveling through space (a medium is not required)
Solar Radiation on Earth
• Approximately about 40% of solar radia2on is reflected back into space • The remaining 60% is the driving force of all life on Earth • UV (ultraviolet) radia2on affects the Earth both posi2vely & nega2vely
How do we measure UV radiation? • We use the UV Index Scale & radia2on is reported on the scale of 1-‐11+ • People should take special care when the UV index is 5-‐6 or higher
UV radiation & the E. Spectrum • UV radia2on has shorter wavelengths & higher frequencies than visible light • Humans cannot see UV rays, but some insects, like bumblebees can!
Pros & Cons of solar radiation
• Pros:
– The Earth receives a huge amount of energy – If we converted to usable energy -‐-‐-‐ just 0.2% of the solar radia2on that falls on our na2on, we would meet the energy demand of the en2re United States – Helps plants grow & warms the Earth
• Cons: – May cause skin cancer, burns, wrinkles etc. – Can adversely affect animal popula2ons
Pros & Cons of solar radiation
Solar Radiation on Earth
• Intensity of solar radia2on varies with... la9tude, 9me of day, & the path through atmospheric gases
Solar Radiation on Earth
• The Earth receives solar radia2on unequally over its surface • The intensity per unit area of surface is greatest at the equator • The intensity is lowest at the polar regions Yellow pixels show the highest levels of radia2on at the surface, red and pink hues are intermediate values, and white indicates lihle or no UV exposure.
Our Ozone Layer
• The ozone layer is a thin shield high up in the sky that protects life on Earth from the sun’s UV rays • In the 1980s, scien2sts began finding the ozone being depleted allowing more UV radia2on to reach Earth’s surface
What’s wrong with the ozone? • Decreases levels of ozone in the atmosphere will allow more UV radia9on to reach the surface • UV radia2on is known to adversely affect growth & reproduc2on in organisms & increase risk of skin cancer and cataracts
What’s the UN Montreal Protocol? • Thanks for the UN Montreal Protocol, the produc2on & consump2on of en2re groups of harmful ozone-‐deple2ng chemical has been successfully phased out in developed countries & the same process is now ell under way in developing countries • The Montreal Protocol on Substances that Deplete the Ozone Layer (full name) was designed to reduce the produc2on & consump2on of ozone deple2ng substances to reduce their abundance in the atmosphere & protect Earth’s ozone layer
What’s the UN Montreal Protocol? • The original Montreal Protocol was agreed on 16 September 1987 and entered into force on 1 January 1989.
Other dangerous chemicals • Awer 20 years of protec2ng the ozone layer with a new genera2on of chemicals, governments are now having to confront the fact that these ozone-‐friendly subs2tutes for chlorofluorocarbons (CFCs) also happen to be greenhouse gases that contribute to global warming.
Solar Oven Project
• Use the supplies (aluminum foil, pizza box, saran wrap, glue, wooden kabob s2ck to build your solar oven • There is not a “right” design – use your knowledge of solar radia2on • We will place in the sun & measure the changing temperature & observe the condi2on of the smores
jeopardylabs.com/play/unit-‐1-‐astronomy.
Happy Tuesday! September 8 2015 th
Today’s agenda: • • • •
review solar radiation & photosynthesis Complete study guide Make 10 flashcards Test tomorrow!
Solar radiation • The Sun’s energy reaches the Earth via _____________ radia9on (waves through space) • The Sun’s rays are called _UV ___ rays and are essen2al to life on Earth • Plants use sunlight to produce food through a process called _photosynthesis _____________ Light energy 6
CO2
+
Carbon dioxide
6
H2O Water
C6H12O6 PHOTOSYNTHESIS
Glucose
+
6
O2
Oxygen gas
Solar radiation fusion occurs on the sun • Nuclear ________ • H + H = He + a lot of energy • Solar radia2on decreases with distance • Our distance from the sun control how much solar energy we get from it • Several things can happen to that incoming energy: reflec9on, refrac9on, sca`ering, & absorp9on
The sun
Seasons
• The Earth’s ____________ rotation (spinning on its axis) along with its axial _tilt __ allows for different seasons: summer, winter, fall, spring • Depending on the region, different amounts of solar energy strike the Earth at various 2mes of the year • The equator gets the _most ____ & the poles get the ________ least • Distance from the equator and the intensity of solar radia9on have a direct effect on seasonal changes
Earth’s Tides Review
• Tides are daily changes in the eleva2on of the ocean surface • When the moon, Earth, & Sun are aligned, __________ SPRING 2des occur • When the moon & Sun form a right angle NEAP 2des occur with the Earth, _______
WATCH CRASH COURSE