Location: United States
Big blue marble or pale blue dot, the earth rotates on its axis as it revolves around the sun in 365 1/4 days.
Earth's axis is titled at a 23 1/2 degree angle, and this causes the seasons. When the United States tilts toward the sun, we have summer. Six months later, when the U.S. tilts away from the sun, we have winter.
Earth's atmosphere is 21% oxygen and 77% nitrogen. It contains water vapor and carbon dioxide gas. Plants create oxygen. The atmosphere protects us from the sun's harmful rays (such as X-rays) and provides a stable temperature so that life can exist.
Water covers 70% of the earth. If our planet were closer to or farther from the sun, liquid water could not exist and you would not be reading this. Water shapes the earth's crust of which the Grand Canyon is an obvious example. Icecaps exist at the North and South Poles.
Water evaporates to form clouds. Clouds are droplets of water that turn into rain. Heat from the sun causes air to expand and move, creating wind. Weather satellites orbit the earth, keeping track of hurricanes.
The earth has a magnetic field because of its iron core.
Solar and lunar eclipses occur when the earth, moon and sun line up. Both the moon and the earth cast shadows into space. A solar eclipse occurs when the moon's shadow falls on the earth. A lunar eclipse occurs when the moon moves into the earth's shadow. Lunar eclipses are visible everywhere on the night side of Earth.
Three things that are not real are moonlight, sunsets and sunrises. What we call moonlight is sunlight reflecting off the moon.
The earth rotates in and out of its own shadow to produce the illusion of the sun setting and rising. The sun is stationary relative to the earth. Yet, our language reflects the Ptolemaic idea rather than Copernicus's heliocentric reality. The spinning earth makes the sun appear to set and rise. What we call night is simply the earth's shadow. The edge of the shadow is seen in the east at twilight as a curved band of darkness on the atmosphere.
Night, or Earth's shadow, is always there. Different parts of the planet turn into it during a 24 hour period. Half of the earth always faces its shadow. Half is always illuminated. Any location on the moon spends two weeks in the moon's shadow.
Half of the celestial sphere is visible from any spot on Earth. The earth's bulk blocks the other half. Celestial objects appear to move in curved tracks as the earth spins.
In summer, we are in that part of Earth's orbit fartherest from the sun but tilted toward it. In winter, we are in that part of Earth's orbit closest to the sun but tilted away from it. The reverse applies to the Southern Hemisphere.
The sun does not burn in the way we normally think of something burning. When a piece of paper or a piece of wood burns, only the electrons are changed. When nuclear fusion occurs in the sun, it changes the very nature of its elements.
Light is radiation, energy traveling through space. Stars and galaxies make both visible and invisible light. Radio waves, infrared radiation and X-rays are invisible light. The Hubble Space Telescope detects visible light. The Spitzer ST detects infrared.
The HST and Spitzer along with Chandra and Compton comprised NASA's Great Observatories Program. Chandra studies X-Rays, and Compton studied gamma-rays until it was deorbited due to a failed gyroscope. These four telescopes have imaged objects using the entire electromagnetic spectrum.
The Very Large Array VLA in New Mexico is a radio telescope. Huge dishes are used to receive faint radio waves. Radio waves have the longest wavelengths.
Black hole notes...
A black hole is a star so massive that it collapsed under its own gravity. Astronomers enjoy repeating that not even light can escape from a black hole. The escape velocity on earth is 24,850 miles per hour. Nothing travels faster than light at 186,000 miles per second, and the escape velocity from a black hole exceeds even the speed of light. What goes in, stays in! Sort of like what happens in Vegas, stays in Vegas! A massive star's collapse is so drastic that only its gravitational field remains. With gravity so powerful, time slows down and ultimately stops. At the center of a black hole is a singularity. A singularity is a size-less point of infinite density. A collapsed star's mass disappears into a singularity as a black hole becomes a bottomless funnel.
Cygnus X-1 is a black hole, a source of X-rays in the constellation Cygnus. Astronomers found it while studying binary stars with an X-ray telescope launched in 1970. Black holes are at the centers of galaxies and may have been responsible for the formation of galaxies.
Stephen Hawking thinks there could be "wormholes" at the center of black holes leading to other universes.
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JIM COLYER "GIRL ALBUM"