P7 Page 9 and 10 Flashcards
What was the Curtis-Shapely debate?
In 1920’s, there was a debate about the size of structure of the universe. Through telescopes people saw faint,fuzzy objects that they called nebulae- they argued what they were.
Why would you see a strip of stars if you looked up into the sky?
Because we have a see view of one of the disks of the Milky Way.
What was Shapley’s argument?
1) Shapley believed the Universe was one gigantic galaxy.
2) He reckoned the sun and solar system were far from the centre of galaxy.(right)
3) believed nebulae were huge clouds of gas and dust, believed clouds were part of the Milky Way.
What was Curtis’s argument?
1) The universe was made up from many galaxies
2) He thought our galaxy was smaller than Shapley suggested.
3) The spiral nebulae were other distant galaxies, completely separate from the Milky Way.
4) The sun at or very near the centre of the Milky Way.
Who was right form the Curtis-Shapley debate?
1) Shapley was right that the solar system is far form the centre of our galaxy.
2) Curtis was right that many galaxies made up the universe.
3) Curtis was also right about spiral nebulae.
How did Hubble prove Curtis was right about the Universe?
Huble calculated the distance to the Andromeda nebula by working out the distance to the Cepheid variable within it, using the
relationship between their brightness and pulse frequency.
He found to was 2.5 million light years away-much further than any stars in our galaxy.
What is redshift?
When a galaxy is moving away the wavelength of light from it changes, it becomes redder.
What is the pattern between the distance of a galaxy and its speed?
The further away it is, the faster it moves away form us.
What is the Big Bang theory?
That the whole universe expanded from a single point, which could be explained by an initial explosion millions of years ago that started off the expansion.
Speed of recession =
Km/s
= Hubble constant(km/s per Mpc) x distance (km or Mpc)
What is the Hubble constant?
70km/s per Mpc
