Astronomy 33

What did Tycho Brahe see in the sky that convinced him that the heavenly firmament was not as unchanging/perfect as previously believed?

supernova comet

What were three of Tycho Brahe's reasons for believing his model had to be right?

he observed a supernova (exploding star) which disappeared after 18 months--conclusion the heavens are not unchanging he observed a comet--which proved that not everything is non-changing and not everything is a circular motion. he measured the movement of planets and stars: couldn't find the parallax, conclusion: the earth is at the center of the universe unmoving.

What does the word "Planet" mean in Greek?

Wanderer

State Kepler's 3 laws of Planetary Motion

(1) All planets move about the Sun in elliptical orbits, having the Sun as one of the foci. (2) A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time. (3) The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun.

Identify two conclusions Galileo drew from his observation of sunspots (dark spots) on the sun.

-sun spots are slower near the edge of the sun and faster in the center -sunspots move and change their shape

What year did Galileo make his first telescope?

1609

What is the difference between a heliocentric model of the solar system and a geocentric model?

A heliocentric model states that the sun is in the center of the universe while geocentric states the earth is the center

Were Aristotle's predictions of heavenly motion quantitative or qualitative?

Aristotle's predictions were qualitative because it did not have any quantitative predictions of motion, e.g where and when to find planets.

What was Tycho Brahe's model of the solar system?

Brahe proposed a model of the solar system to explain Galileo's observation that Venus has phases without making it necessary for Earth to be moving. His model had all the planets except Earth orbiting around the Sun, but then the Sun orbited around the Earth.

What is the Copernican theory of the universe?

Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths modified by epicycles and at uniform speeds.

How did the Copernican theory explain retrograde motion?

Copernicus didn't like the fact that the Ptolemaic model had big epicycles to explain the retrograde motions of the planets. He knew that this could be explained instead by having the Earth also moving around the Sun.

Why was Galileo sent to exile in Siena?

He was found guilty of heresy.

Where is it when Earth is traveling the fastest?

In January, when it is closest to the Sun.

What is the significance of Galileo's observations of the phases of Venus?

It proved that Venus moved around the Sun.

What was the date the last time Earth was at perihelion?

January 3rd

How did Kepler deviate from the beliefs of Aristotle and Copernicus in his first law?

Johannes Kepler came up with his first law in 1618 which says that every planet moves in an ellipse with the Sun at one focus (an ellipse has two of these). It differs from earlier theories, which were not bad, just complicated, that the planets move in a system of circles. There would be a circle for the main orbit, then another small circle to allow for the fact that each planet is sometimes closer to the Sun or further away than normal, then another small circle to allow for the inclination of the orbit to the ecliptic, and so on.

State Kepler's three laws of planetary motion.

Kepler's three laws of planetary motion can be stated as follows: (1) All planets move about the Sun in elliptical orbits, having the Sun as one of the foci. (2) A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time.

What is parallax? How would you demonstrate parallax with your own eyes?

Parallax is the shift in position of an object caused by your own motion. If you look at an object and cover first one eye then the other, the object will appear to be changing position.

What is perihelion? aphelion?

Perihelion is when the Earth is closest to the sun, while Aphelion is the furthest away.

What are the characteristics of Aristotle's picture of the heavens?

Planets moved and were carried on spheres like a mechanical clock mechanism. Earth resided at the center Outermost sphere was the "prime mover" Moon, Sun, Planets carried on inner spheres 55 spheres in all were necessary for the giant clockwork.

When did Aristarchus of Samos propose his heliocentric model? Why wasn't it accepted at that time?

That the sun was the center of the universe and we orbited it and it wasn't accepted because it went against the science of the time

What key factor kept the Copernican theory from being widely accepted at first?

The key factor was that Copernicus proposed a heliocentric system (sun at the center) and the Roman Catholic Church had decided that the earth was the center of the universe (geocentric system) and that any contrary opinions about that was false.

How is an astronomical unit (A.U.) defined?

The mean distance between the Earth and the Sun.

Tycho Brahe constructed an observatory in Denmark with the most accurate pretelescopic observing instruments ever designed. What was the precision of his measurements?

The precision of his measurements was 1 minute of arc, which means a unit of angular measurement equal to 1/60 of one degree.

Whose data did Johannes Kepler analyze to arrive at his three laws of planetary motion?

Tycho Brahe