Chapter 1.3
notes
· -How
is earth moving in our solar system?
Contrary to our
perception, we are not “sitting still”
We are moving with the
earth in several ways, and at surprisingly fast speeds.
· -Earth
orbits the sun once a year….
At an average distance of
1 AU= 150 million km
With earth’s axis tilted
by 23.5 degrees.
And rotates in the same
direction it orbits, counter-clockwise as viewed from above the North Pole.
· -Our
sun moves randomly relative to the other stars in the local solar
neighborhood….
At typical relative
speeds of more than 70,000 km/hr
But stars are so far away
that we cannot easily notice their motion and it orbits the glaxy every 230
millions years.
· -More
detailed study of the Milky Way’s rotation reveals on of the greatest mysteries
in astronomy.
· -Most
of milky way’s light comes from disk and bulge but most of the mass is halo.
· -How
do galaxies move within the universe?
Galaxies are carried
along with the expansion of the universe.
· -Hubble
discovered that…..
All galaxies outside our
local group are moving away from us.
The more distant the
galaxy, the faster it is racing away
Conclusion: we live in an
expanding universe
· -We
are never standing still.
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