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Chapter 18
Studying Space
Astronomy: The Original Science
•Astronomy: The study of the universe
•Year: The time required for the Earth to orbit once around the sun.
•Month: (roughly) The amount of time required for the moon to orbit
once around the Earth.
•Day: The time required for the Earth to rotate once on its axis.
Early Astronomy
Early astronomers only had oral histories to learn from. Almost
everything they knew came from what they could discover with their
eyes and minds.
•Ptolemy: He thought that the Earth was at the center of the universe
and that the other planets and the sun revolved around the Earth.
Although later proven incorrect, it was a popular theory for 1,500
years in Europe.
•Copernicus: 1543 published a new theory. His theory was that the
Sun was the center of the universe.
•Tycho Brahe: Created large tools which recorded very precise
observations of the planets and the stars that helped future
astronomers.
•Johannes Kepler: Brahe’s assistant, confirmed that the planets
revolves around the Sun in an elliptical orbit, and stated 3 laws of
planetary motion that are still used today.
•Galileo: One of the first people to use a telescope to observe
objects in space.
•Isaac Newton: 1687 he showed that all objects in the universe
attract each other through gravitational force.
Modern Astronomy
•Edwin Hubble: 1924 He proved that other galaxies existed beyond
the edge of the Milky Way.
•Today larger, better telescopes and computers have helped
answer many questions, but new technologies have presented new
questions that were unthinkable even 10 years ago.
Telescopes
•Telescope: is an instrument that gathers electromagnetic radiation
from objects in space and concentrates it for better observation.
Optical Telescope:
•Most common type of telescope
•Collects visible light and focuses it on a focal point
•Has 2 lenses
•Refracting Telescope: Has an objective lens that bends light that
passes through it and focuses the light to magnified by an eye
piece. Has 2 limitations that make this the unlikely choice for most
professional astronomers.
•Reflecting Telescope: Uses a curved mirror, the larger the mirror
allows more light reflected. Flaws in the glass so not affect the light,
and the mirrors can focus all color of light.
•Electromagnetic Spectrum:
–1852 James Clerk Maxwell proved that visible light is part of the
electromagnetic spectrum.
–Each color of light is a different wavelength of electromagnetic
radiation.
–Humans can only see visible light, the rest of the spectrum is invisible
to the human eye.
–The earth’s atmosphere blocks most of the invisible radiation like a
protective shield.
–Radio waves, microwaves, infrared, visible and some ultraviolet light
can pass through the atmosphere.
Nonoptical Telescopes:
•Used to study invisible radiation
Radio Telescopes:
•Detect radio waves
•Scientists can get more detailed images if they link radio telescopes
together.
•Working together, they can scretch 30km across
Mapping Stars
•Constellations are sections of the sky that contain recognizable star
patterns.
•Constellations help organize the sky.
•Constellations move in the depending on the season of the year.
•You can use an ASTROLABE to locate objects in the sky. To so, you
must understand zenith, altitude, and horizon.
–Zenith is the point in the sky directly above an observe on Earth
–Altitude is the angle between an object in the sky and the horizon.
–Horizon is the line where the sky and the Earth appear to meet.
Light Year
•Stars are so far away, the a new unit of measure was created-a light
year is a unit of measure equal to 9.46 trillion kilometers!
•This is the distance that light travels in 1 year.
The Doppler Effect
•If a light source, such as a star or galaxy, is moving quickly away
from an observer, the light emitted looks redder than it normally
does. This effect is called redshift.
•If the light source is moving quickly toward the observer, the light
appears bluer than normaly. This effect is called blueshift.
The Universe is EXPANDING
•Scientists believe that galaxies are rapidly moving apart which
means that the universe is expanding.
Words to KNOW 