Inertia An object in motion will stay in motion until a force acts against it. The more Mass an object has, the more Inertia. The harder it is to start/stop it. Unless you stop it, a planet will keep flying through space forever.

Gravity A force that pulls objects towards each other. Gravity pulls the Moon towards the Earth. Strength of gravity depends on the Masses and Distance between the objects.

Comets -Chunks of ice & space dust flying through space -in an elliptical orbit around the sun -that goes in and out of our solar system -can be seen for weeks or months -can have a tail that points away from the sun

“On April 20, 2007, the comet (Encke) had just dipped inside the orbit of Mercury, perilously close to the sun, when a solar eruption struck and literally tore the comet's tail off. This surely has happened to comets before, but for the first time in history a spacecraft was watching. NASA's STEREO-A probe recorded a fantastic movie of the collision. “

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This image of the Hale-Bopp comet was taken on March 7, The comet is currently as far away from the Sun as our Earth is (1 astronomical unit). The yellow lines show where the comet has extensive outbursts of dust from its center or nucleus. This is very unusual because comets normally don't spew out this much dust at this distance. The image was taken by H Fukushima, M Takata, and D Kinshita. National Astronomical Observatory of Japan

Asteroids Large Chunks of Rock floating in space. Not spherical (ball-shaped like a planet). Most orbit the Sun between Mars & Jupiter – Asteroid Belt 26 asteroids are 200 Km long! Most more than 100 Km long!

Most is empty space. Put all the asteroids together, they would still be smaller than Earth’s Moon. About 40,000 asteroids are more than ½ mile long!

Stoney asteroid 243 Ida and its satellite Dactyl (more information and orbit).243Idainformationorbit

Meteoroid Small chunks of Rocks & Metals that float around in space Broken off from asteroids, planets or comets

Meteors Meteoroids that are pulled in by E’s gravity Burn up when hit E’s atmosphere We see as “shooting stars” – Meteor Showers Can be seen for only a few seconds

A detailed shot of a meteor, taken during the Leonid meteor shower in mid- November. Image Showing Meteors of the Leonid Meteor Shower, taken from Space. s/meteors/index.html

Meteorite Meteoroid that does not burn up all the way. Hits the E’s surface. Very small, hits very fast. Most hit water, some land – causes craters Craters on Moon – from Meteorites

The Barringer Impact Crater in Arizona, USA. Note that it is 1.2km in diameter and has a maximum depth of 183 meters. It was created by a meteorite of 40 meters in diameter impacting at a speed of 11 km/second.

Meteoroid – rock still in space (Android in space) Meteor – rock that burns up in Earth’s atmosphere (OR it could burn up) Meteorite – rock that lands on Earth (“Are you alright?”)

CometsTale/com.htmlhttp://cse.ssl.berkeley.edu/SegwayEd/lessons/ CometsTale/com.html Comet Game ometstale/frame_gallery.htmlhttp://cse.ssl.berkeley.edu/SegwayEd/lessons/c ometstale/frame_gallery.html Comet history pics