AST201 midterm Flashcards
who was Fritz Zwicky?
a swiss astronomer that discovered ‘missing mass’ in galaxy clusters during the 1930’s.
who was vera rubin?
an astronomer that observed how stars in the outer reaches of the galaxy moved. she realized that stellar orbital speed increased with distance from center of the galaxy
what was rubin’s original hypothesis, and what was it based on?
according to Newton’s law of gravity, stars should orbit faster closer to the center of the galaxy and slower away. this turned out to be false.
newton’s first law of motion:
objects in motion remain in motion unless acted upon by an external force.
newton’s second law of motion:
the change in speed is equal to the applied force divided by the mass of the object. a=f/m
newton’s third law of motion:
for every applied force, there is an equal and opposite reaction. the ball pushes on you as hard as you push on it.
who is charles bolton?
he studied blue giant star cygnus in 1971, determining it was in a binary orbit with an unseen object of about 155 solar masses. cygnus x-1 was the first widely accepted stellar mass black hole.
the supermassive black hole at the middle of the milky way is
Sagittarius A
what did cecelia payne do?
she used spectrography to find out the composition of the sun
what did edward pickering do?
he created the harvard astronomical computers.
who was williamina fleming?
she was a harvard astronomical computer and created the henry draper catalogue.
who was henrietta swan?
she was a harvard astronomical computer and discovered the cepheid variable star period-luminosity relationship.
who was annie jump cannon?
a harvard astronomical computer that formed the OBAFGKM sequence by analyzing stellar spectra with her own eyes.
what is the OBADGM system called?
morgan keenan system
percentages of the universe:
ordinary matter: 4.9%
dark matter: 26.8%
dark energy: 68.3%
define ‘invariance of light’
the concept that all light rays travel at the same speed, regardless of outside factors, independent of frame of reference.
why is einstein’s theory of special relativity special?
because it only deals with cases where the reference frames move at constant speeds
what is einsteins theory of special relativity?
that all laws of physics are the same in all reference frames that move at constant speeds
if two clocks are synced and one stays on earth and the other is put on an airplane, which will have passed through less time?
the one on the airplane
moving clocks…
run slow
what is relativistic speed?
the speed at which the effects of special relativity can be felt
how many forces?
four
what are the four forces?
electromagnetism, gravity, weak nuclear force, strong nuclear force
electromagnetism:
carrier particle: photon. range: infinite.
