22-1 Flashcards
(35 cards)
what is astronomy?
the science that studies the universe; deals with properties of objects in space
what was the “Golden Age” of early astronomy? what did they use and develop?
Early Greeks used philosophy and observations to study the sky. They used astrolabes to find the positions of the sun and stars and developed basic geometry and trigonometry.
what did aristotle conclude? how did he know that?
that the earth was spherical, because if the Earth was flat, the shadow cast on the moon by Earth would be a straight line but saw a curved shadow,
what is the first evidence of a round earth?
Early sailors noticed top of the ship first as ship approaches from a distance, as ships move over curved Earth they see lower portions
what is the second evidence of a round earth?
Sailors noticed the night’s sky changed as one sailed from equator to poles; North Star appeared higher in the sky the farther north they went.
what is the third evidence of a round earth?
Space probes and satellites provide images from space showing Earth is a sphere
who was erastosthenes? what did he observe and reason?
first to calculate size of Earth; observed that the noonday sun was 7° higher in one city than another on the same day. he reasoned that Earth’s full circle (360°) must be about 50 times the distance between the two cities
what is the geocentric model?
Earth is at the center of the universe. The Sun, Moon, and planets move in circles around it, and stars are in a larger sphere that turns slowly. Only the Sun, Moon, and five planets move, the rest stay fixed.
what is a planet?
“wonderer”; moving objects in the night sky
what is the heliocentric model? who found it and what did he conclude about the sun and moon?
sun is the center model of the universe. By aristarchus but not popular, copernicus promoted. Earth just another planet revolving around the sun. aristarchus found that the sun is much farther than the moon and much larger than Earth
what is the ptolemic system?
Ptolemy improved the geocentric model, planets move in cicular motions around Earth, usually moving east but sometimes seeming to stop and go backward.
what is retrogade motion? was it correct?
Earth is lapping faster than Mars, when it begins to pass Mars it creates the illusion that Mars is stopping then moving backwards, which is the apparent movement.
What key idea defines modern astronomy?
The discovery that the universe is governed by natural laws.
who was nicolaus copernicus? what model did he believe?
stated that Earth is a planet with sun at the center of a solar system. Movement of planets and stars due to rotation of Earth, earth not motionless
who was tycho brahe? what did he see, persuade, and make?
saw solar eclipse and persuaded king to build observatory. Made precise observations of Mars, assistant was Johannes Kepler
What do convection currents in Earth’s mantle cause, and how do magnetic fields protect us?
Convection currents move tectonic plates and create magnetic fields, which trap charged solar particles and protect Earth from space radiation.
Why doesn’t a compass point exactly to geographic North? What is geographic north pole and magnetic north pole?
It aligns with Earth’s magnetic field, which is about 11.5° off from the rotational axis. geographic north pole is the exact surface location that never changes, magnetic north pole is the point is where the magnetic flow is happening so it is always changing
what did johannes kepler do?
continued research after Brahe died, major conclusions about planet orbits are referred to as Kepler’s three laws
what is Kepler’s first law?
Discovered shapes of planet orbits to be elliptical (oval) not circular
what is Kepler’s second law?
Calculated that the sun is not at the center but is offset from the center
what is Kepler’s third law?
Planets travel at different speeds in their orbits around the sun. Planets closest to sun travel faster than further away so outer planets take longer to orbit and travel further
what are astronomical units used for?
used to measure distances of solar system
what are the five observations that support Copernicus’s heliocentric view of the universe?
- Noticed that four moons of Jupiter went around it, so not everything in the sky revolves around Earth
- Discovered that planets are circular disks, not stars
- noticed Venus went through phases like the Moon, proves it orbits the Sun. looks smallest when farthest from Earth
- Discovered moon’s surface was not smooth, had mountains/craters/plains
- Discovered sun had sunspots, showed that sun was not perfect, tracking them allowed to estimate rotational period
what did galileo galilei use?
telescopes (tube with two lenses at opposite ends), Galileo built improved versions to find evidences that support ideas of Copernicus
