Download HW1-6

HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
RQ 4: Why did Copernicus have to keep small epicycles in his
model?
Copernicus was still committed to uniform circular motion. The
real motion of planets are elliptical, but he used a combination
of a circle on a circle to try to create an ellipse.
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
RQ 4: Why did Copernicus have to keep small epicycles in his
model?
Copernicus was still committed to uniform circular motion. The
real motion of planets are elliptical, but he used a combination
of a circle on a circle to try to create an ellipse.
RQ 5: When Tycho observed the new star of 1572, he could
detect no parallax. Why did that undermine belief in the
Ptolemaic system?
The Ptolemaic system followed Aristotle’s assertion that all
changeable objects must be earthly. Since this star just
suddenly appeared, the old system said it must be earthly
(under the sphere of the moon).
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
RQ 4: Why did Copernicus have to keep small epicycles in his
model?
Copernicus was still committed to uniform circular motion. The
real motion of planets are elliptical, but he used a combination
of a circle on a circle to try to create an ellipse.
RQ 5: When Tycho observed the new star of 1572, he could
detect no parallax. Why did that undermine belief in the
Ptolemaic system?
The Ptolemaic system followed Aristotle’s assertion that all
changeable objects must be earthly. Since this star just
suddenly appeared, the old system said it must be earthly
(under the sphere of the moon).
Tycho’s observations indicated that the star could not be close. If
it were close, it would have shifted (parallax).
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
RQ 7: How do the first two of Kepler’s three laws overthrow one of
the basic beliefs of classical astronomy?
The first law says that planets move in ellipses, not in circles.
The second law says that planets speed up when near the Sun
and slow down when far from the Sun.
Uniform circular motion is
contradicted by elliptical
motion that changes
speed.
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
RQ 7: How do the first two of Kepler’s three laws overthrow one of
the basic beliefs of classical astronomy?
The first law says that planets move in ellipses, not in circles.
The second law says that planets speed up when near the Sun
and slow down when far from the Sun.
Supp. 6: How did Ptolemy explain retrograde motion? How did
Copernicus explain it differently?
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
RQ 7: How do the first two of Kepler’s three laws overthrow one of
the basic beliefs of classical astronomy?
The first law says that planets move in ellipses, not in circles.
The second law says that planets speed up when near the Sun
and slow down when far from the Sun.
Supp. 6: How did Ptolemy explain retrograde motion? How did
Copernicus explain it differently?
Ptolemy explained retrograde motion by putting the planets on
epicycles. As they went around the Earth, they would
sometimes move forward and sometimes move backwards.
Copernicus didn’t need epicycles to explain retrograde motion.
The fact that the Earth is moving faster than superior planets
naturally explains retrograde motion.
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
Supp. 7: Kepler rejected Tycho’s theoretical work. What
part of Tycho’s work was absolutely crucial for
Kepler’s development of his three laws?
Kepler didn’t need Tycho’s theoretical work.
HW1-6: (76) RQ 4, 5, 7;
Supp. Q’s 6 & 7
Supp. 7: Kepler rejected Tycho’s theoretical work. What
part of Tycho’s work was absolutely crucial for
Kepler’s development of his three laws?
Kepler didn’t need Tycho’s theoretical work.
Kepler did need Tycho’s data. Kepler needed Tycho’s
detailed records of planetary positions in order to have
adequate tests of his theories.