Earth’s rotation and revolution Asteroids, meteoroids and comets

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Earth’s rotation and revolution Asteroids, meteoroids and comets

How do we know how big the Earth is? Watch https://www.ted.com/talks/how_simple_ideas_lead_to_scientific_discoveries https://www.ted.com/talks/how_simple_ideas_lead_to_scientific_discoveries starts at 1:13 to 4:06 Alexandria: links Greece and Egypt 40,075 km actual Earth’s circumference Eratoshenes’s calculation: 40233.6 km 2piR = C= 40233.6  R= 6263 km TODAY WE MEASURE 6371 km

Earth= 4.54 billion years old First life 3.8 billion-year-old Age of universe: 13.7 bya Mass = 5.97E24 kg; Earth is 76x heavier than Moon Moon mass= 7.345 × 1022 kg Sun mass =1.99E30 kg = 333,000 x Earth’s mass Earth- Moon distance: 384,400 km Methods: http://ncseprojects.org/evolution/science/how-old-is-earth Rocks in the 4-5 Ga range may be dated by measuring ratios of isotopes of uranium/lead, rubidium/strontium, potassium/argon, argon/argon, and neodymium/samarium. One way to judge the reliability of a radiometric measurement is to compare the results of different measurement techniques for the same sample. Pretty much the solar system was formed 4.5 bya then Homo sapiens: 200 000 years ago How old is the sun? how do we know https://www.youtube.com/watch?v=bD0SpfHy__o  dating technique with Rb First star: ~ 200 mill years after big bang

Earth’s axis of rotation Is 23.5o tilted Earth rotates eastward toward the Sun SUN Good video to recap: http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/astronomy_space/activity/ https://www.youtube.com/watch?v=9n04SEzuvXo https://www.youtube.com/watch?v=l64YwNl1wr0 https://www.youtube.com/watch?v=9n04SEzuvXo Recap: http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/astronomy_space/activity/

How rotation differs from revolution? The turning of an object around an imaginary axis running through it E.g. Earth’s rotation takes 24 hrs The rotation of an object around an external axis (e.g. another object) E.g. Earth’s revolution around the Sun is 365.24 days Leap year anyone? https://www.youtube.com/watch?v=cDed5eXmngE

Watch: MIT video https://www.youtube.com/watch?v=Pgq0LThW7QA When it is summer in the northern hemisphere, it is winter in the southern hemisphere. Why? Watch: MIT video https://www.youtube.com/watch?v=Pgq0LThW7QA

If the Earth weren’t tilted on its axis, there would be no season Reason for seasons Answer: because of Earth’s tilt In summer months: Northern hemisphere toward the Sun In winter months: Northern hemisphere away from Sun The opposite happens to Southern hemisphere http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/astronomy_space/activity/ Satellites that orbit Earth, including the moon, do not always stay the same distance from Earth. Sometimes they are closer, and at other times they are farther away. The closest point a satellite comes to Earth is called its perigee. The farthest point is the apogee. For planets, the point in their orbit closest to the sun is perihelion. The farthest point is called aphelion. Earth reaches its aphelion during summer in the Northern Hemisphere. The time it takes a satellite to make one full orbit is called its period. For example, Earth has an orbital period of one year. The inclination is the angle the orbital plane makes when compared with Earth's equator. If the Earth weren’t tilted on its axis, there would be no season

Asteroids Small, rocky objects that never formed into planets They also orbit the Sun Most found in the asteroid belt between Mars and Jupiter Some can have their own satellite/moon Bill Nye- Can we prevent the next impact by an asteroid? https://www.youtube.com/watch?v=Agdvt9M3NJA Ida Dactyl

Piece of rock moving through space Meteoroid Meteor Meteorite Piece of rock moving through space a burning meteoroid as it enters the Earth’s atmosphere a fragment of a meteor fallen to earth. http://www.space.com/15353-meteor-showers-facts-shooting-stars-skywatching-sdcmp.html 1st video to 2:25 min

A- Metorite B- Meteroid C- Meteor D- Asteroid What do we call a rock that is…? ____Found between Mars and Jupiter? ____Travelling through space ____Burnt up in Earth’s atmosphere ____the space rock that reaches Earth’s crust A- Metorite B- Meteroid C- Meteor D- Asteroid

Shooting stars Meteor Shower are actually not stars but meteors as they burn up in Earth’s atmosphere leaving behind trails Occurs when Earth passes into the path of debris left behind by a comet These debris burn up in Earth’s atm. creating streaks of light in the sky http://coolcosmos.ipac.caltech.edu/ask/256-What-is-a-meteor-shower- As a comet travels close to the Sun, it heats up and part of the comet vaporizes. After a comet has orbited the Sun many times, a lot of small pieces of the comet are left along the comet's path. A meteor shower happens when Earth passes through the path of a comet. When this happens, the bits of comet debris, most no larger than a grain of sand, create streaks of light in the night sky as they burn up in Earth's atmosphere. Bits of debris which enter Earth's atmosphere are called meteors. On any night, there are several small meteors which shoot across the sky. However, during a meteor shower, tens to hundreds of meteors can be seen each hour. Many of these meteor showers can be predicted and occur at the same time each year. https://www.youtube.com/watch?v=IKLEd2iffD0 (Ha!)

Pingualuit meteor crater in Quebec

Comets Objects made of dust, ice, rock, and gas The Sun’s wind pushes gases and particles away from the comet creating a tail A comet has 2 tails: dust tail and gas tail https://www.youtube.com/watch?v=C8zV1xiGqf4

End

Solstices Occur on June 21 and Dec 21 Solstice occurs when the Sun shine directly on one of the two tropics because the tilt of the Earth’s axis reaches its maximum angle compared to the Sun During the June (summer) Solstice the rays of the Sun shine directly on the Tropic of Cancer; longest day During the December (Winter) Solstice the Sun’s rays shine on the Tropic of Capricorn; longest night

Equinox As the Earth moves around its orbit, it reaches two points during the year where the tilt of its axis causes it to be straight relative to the Sun. Thus, the Sun will shine directly on the equator on Mar 20 and Sep 22