Earth Science: Astronomy

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Unit 7. Earth Science: Astronomy . Bell Ringer Activity: Get out a clean sheet of paper.

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## Earth Science: Astronomy

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Unit 7

### Earth Science: Astronomy

Bell Ringer Activity: Get out a clean sheet of paper.
• You have 5 minutes from the time the bell rings to read the article at your table. At the end of 5 minutes you will answer questions about the article. You will have 3 minutes to answer the questions. Please use complete sentences, be neat and complete.
Questions
• 1. Would it take more fuel to launch a rocket from Maine or North Carolina? Why?
• 2. Compare the spin of the Earth at the poles with the spin of the Earth at the Equator.
• 3. The Moon does not have an equatorial bulge. Considering the cause of the equatorial bulge, what can you hypothesize about the Moon’s rotation?
• 1. Would it take more fuel to launch a rocket from Maine or North Carolina? Why? It would take more fuel to launch from Maine. The Earth’s gravitational pull is greater in Maine because it does not bulge like the equator making it closer to the center of the Earth. There is also less momentum in Maine because it is spinning slower.
• 2. Compare the spin of the Earth at the poles with the spin of the Earth at the Equator. The spin is slower at the Poles than the Equator because the circumference is smaller at the Poles. The equator is where the Earth’s rotation is greatest, therefore, the spin is faster.
• 3. The Moon does not have an equatorial bulge. Considering the cause of the equatorial bulge, what can you hypothesize about the Moon’s rotation? The Moon does not rotate very fast. (It takes about a month for it to spin on its axis one time.)
• 1.5 x 1011 meters or 1.5 x 108 km
• 93 million miles
• C. Light Year – the distance light travels in a year.
• How far is a light year? Light travels at
• 186,000 miles/second. There are
• 60 seconds in a minute. There are
• 60 minutes in an hour. There are
• 24 hours in a day. There are
• 365 days in a year. Use a calculator to figure the distance of a light year. ___________________ miles
The Nebular Hypothesis

Everything formed in the same place at the same time: ~4.5 billion years ago.

Solar system was formed in the gravitational collapse of a giant cloud of gas and dust, known as the solar nebula.

Initial stages

The Solar System is thought to have started out as a giant gas cloud, composed mainly of hydrogen and helium, but also containing some heavier elements including ice and metals.

Under its own gravitational attraction, it collapses.

Accretion Disk formation

As a gas cloud collapses, it begins to spin more quickly.

The centrifugal force of this rotation flattens it out into a rotating disk with a protostar at the center.

The nebula is hot because of gravitational energy released by the collapse, and when the protostar ignites at the centre it produces more heat. So there is a strong temperature gradient across the disk: the temperature gets hotter towards the center.

Milky Way Galaxy
• This is the galaxy that Earth is in.
• Large spiral galaxy whose disk is about 100,000 light years wide.
• Contains more than 100 billion stars.
Galaxy Tour
• https://www.e-education.psu.edu/astro801/content/l10_p4.html
D. Constellations – groups of star patterns.
• 1. There are 88 constellations that are official.
• 2. Asterisms – small group of stars, which are less formally defined.
II. The Earth
• A. The Earth rotates on its axis.
• Proof:
• 1. Bulging shape
• 2.Wind Patterns
• 3. Foucault pendulum
• http://sortingoutscience.net/2008/07/15/the-scientific-tourist-29-the-foucault-pendulum/

C. Precession – the slow change in the direction of Earth’s axis of rotation. One cycle takes approx. 26,000 years. This does not change the seasons.

• This changes the stars near the poles.
• North Stars:
• 1. Thuban
• 2. Polaris (current)
• 3. Vega
D. Nutation- wobbling around the processional axis.
• This is caused by the Moon.
• Its period is 18.6 years.
• It causes slight seasonal effects.
E. Seasons
• 1. Caused by the Earth’s tilt of 23 ½ degrees.
• 2. The Sun is higher in the sky in the summer and lower in winter.
• 3. We are closer to the Sun in January and farther away in July.
• 4. Equinox – when the Sun’s path crosses the Celestial Equator. There are 12 hours of light and 12 hours of night.
• a. Vernal Equinox – occurs around March 21; the Sun is going North. It is spring.

b. Autumnal Equinox – the Sun is going South around Sept. 23 = Fall.

• 5. Solstice – when the Sun reaches its farthest point North and 6 months later its farthest point South.
• a. Summer Solstice – June 21, North = longest day.
• b. Winter Solstice – Dec. 22, South = shortest day.
F. The Tides
• http://www.pbs.org/wgbh/nova/earth/what-causes-the-tides.html
• 1. (In your notes write a summary of what the animation presented.)
Think/Pair/Share

2. The gravitational pull of the Moon and inertial force (outward directed force) cause tides.

• 3. The Moon and the Earth both rotate around their center of gravity (barycenter).
• 4. Spring tide – when the Earth, the Moon and the Sun are in a straight line. This is during New Moon and Full Moon. The high tides are higher and the low tides are lower because of the combined gravitational force.

5. Neap tide – During the moon's quarter phases the Sun and Moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). Neap tides occur during quarter moons.

• (http://home.hiwaay.net/~krcool/Astro/moon/moontides/)
Bill Nye: Exploring Space (23)
III. Earth’s Motion Through Space
• A. The Earth rotates on its axis every 24 hours.
• B. The Earth revolves around the Sun every 365.25 days.
C. Kepler’s Laws of Planetary Motion
• 1. Kepler’s 1st Law - Planets travel in ellipses around the Sun, with the Sun at one focus.
• http://www.astro.illinois.edu/projects/data/KeplersLaws/

2. Kepler’s 2nd Law

• A line connecting the Sun to a planet sweeps out equal areas in equal amounts of time.
• http://www.walter-fendt.de/ph14e/keplerlaw2.htm

3. Kepler’s 3rd Law

• P2 = d3
• http://www.physics.sjsu.edu/Tomley/Kepler3.html
D. Barycenter
• http://spaceplace.nasa.gov/barycenter/
Barycenter
• Barycenter - the point about which two celestial bodies revolve around. Essentially, it is the center of mass or center of gravity of the two bodies if you can think of the two bodies acting as one.
• When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that lies outside the center of the primary (the larger body).
Barycenter continued
• The Sun is not stationary 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.

E. Motion

• The Earth revolves around the Sun.
• The Sun (and everything in the Solar System) is revolving around the Milky Way Galaxy.
• The Milk Way Galaxy is revolving around a cluster of galaxies.
• Our cluster of galaxies is revolving around our supercluster of clusters of galaxies.
• Our supercluster is revolving around the universe.
• This motion has been detected using Doppler Shift data.
F. Origin of motion
• “The solar nebula model says that the solar system formed out of an eastward rotation interstellar cloud about 5 billion years ago. The nebula contracted in the Sun surrounded by a spinning disk where the planets formed.”
• ( Astronomy by Dinah L. Moche)
IV. The Sun’s Energy
• A. The Sun is a star.
• 1. It is a medium sized star.
• 2. It is a medium temperature star.
B. Nuclear Reactions
• 1. Two types of nuclear reactions
• a. Fission Reactions – a large nucleus splits into 2 or more smaller nuclei.

Nuclear power plants and nuclear bombs are examples of fission.

2. Nuclear Fusion – the combining of 2 or more nuclei into a larger nucleus.

• Example: The Sun
Hydrogen Fusion
• The Sun fuses together 4 hydrogen nuclei to make 1 helium nucleus. The 1 helium nucleus has less mass than the 4 hydrogen nuclei. The difference in mass is changed into energy.
• 1) The Sun’s transfers its energy to the Earth by electromagnetic radiation.
• 2) The Longest Wavelength - Radio
• Microwaves
• Infrared
• Visible
• Ultraviolet
• X-rays
• Shortest Wavelength - Gamma
• 1 rem received in a short period or over a long period is safe—we don’t expect observable health effects.
• 10 rem received in a short period or over a long period is safe—we don’t expect immediate observable health effects, although your chances of getting cancer might be very slightly increased.
• 100 rem received in a short time can cause observable health effects from which your body will likely recover, and 100 rem received in a short time or over many years will increase your chances of getting cancer.
• 1,000 rem in a short or long period of time will cause immediately observable health effects and is likely to cause death.
• “Most ozone is concentrated in the stratosphere, at about 25 km in altitude, and is considered to be ‘good ozone.’In this region, ozone acts as a shield to protect Earth's surface by absorbing harmful ultraviolet radiation. Without this shield, we would be more susceptible to skin cancer, cataracts, and impaired immune systems.”

2. Earth’s Magnetic Field –

• a. The Earth is protected from the solar wind, a stream of energetic charged particles emanating from the Sun, by its magnetic field, which deflects most of the charged particles. These particles would destroy the ozone layer.
• b. Causes of Earth’s magnetic field
• 1) Outer Core is molten Iron

2) Earth rotates on its axis (rapidly)

F. The Sun – Essential to life
• 1. The Sun is the Earth’s primary energy source.
• a. Sunlight reaching the Earth can heat the land, ocean, and atmosphere. Some of that sunlight is reflected back to space by the surface, clouds, or ice. Much of the sunlight that reaches Earth is absorbed and warms the planet. (http://beyondweather.ehe.osu.edu/issue/the-sun-and-earths-climate/the-sun-earth%E2%80%99s-primary-energy-source#ConceptA)

b. Photosynthesis – the changing of the Sun’s energy into stored chemical energy.

• Light + 6H20 + 6CO2

C6H12O6 + 6O2

Light + Water + Carbon glucose + oxygen

Plants and algae, which use photosynthesis, form the basis of the food chain.

E. Differential Heating
• Differential heating refers to the difference in how land and water surfaces absorb heat. Water has a higher capacity for storing heat than does land surfaces.
• The degree and direction of the differential heating between land and sea is determined by the amount of solar energy reaching the earths surface.