Models of the universe from Aristotle to Newton - HOW DID EACH VIEW THE STRUCTURE OF THE UNIVERSE?

What is the current scientific thinking about the structure of the universe?

Chronicle of the 20th Century (Space Exploration) Intro; War of the Worlds Soundtrack

2. The first minutes of the universe released energy which changed to matter, forming stars

and galaxies• What are quarks?

• What is the structure of the atom; features of subatomic particles?

• How did Hubble discover an expanding Universe? Who’s Friedmann?

• What are the stages of the ‘Big Bang’ theory? Energy? Matter?

WHICH SET OF SPECTRAL LINES ARE RED SHIFTED - GREEN OR YELLOW?

Big Bang

Cosmic ‘atom’undergoesBig Bang

Expanding universeis a ‘soup’ of quarks

then protons,neutrons & electrons

Gases coalesceto form stars and planets

Cooling and expansion leads

to atoms

Stars gatherto form galaxies

Extremeenergy

concentration

Energy transforming into matter.

Energy dominantover matter

E>m

K.E decreasing,matter

dominantm>E

Increasedgravitational

attraction led tolumpy gas cloud

Stars attractedby gravity

3. Stars have a limited life span and may explode to form

supernovas

Recall the inverse square Law, relate intrinsic luminosity,distance and brightness

LUMINOUS STARS MAY APPEAR LESS BRIGHT WHEN FAR AWAY

LESS LUMINOUS STARS MAY APPEAR BRIGHT BECAUSE THEY ARE CLOSER

I = 1/rI = 1/r 2

LUMINOUS STARS MAY APPEAR LESS BRIGHT WHEN FAR AWAY

LESS LUMINOUS STARS MAY APPEAR BRIGHT BECAUSE THEY ARE CLOSER

Temperature•Ionised Hydrogen means there are no absorption lines in O and B stars (hot)(20000+ K). At lower than 10000K, Balmer absorption lines are produced, so Hydrogen absorption is a maximum in A2 stars

•Different elements produce strong absorption lines at different temperatures. Therefore, observing the strong absorption lines for elements indicates the temperature

•Using Wien’s Law we can calculate the surface temperature from the wavelength of maximum intensity

Practical Activity 13.2Jacaranda text

or heat pencil lead (use safety glasses!)

Hertzsprung-Russell diagram

Luminosity (incr.) vs colour or temperature(decr.)Where are red giants, white dwarfs, main sequence?

Energy sources of starsNuclear energy

Fission - atoms split apart e.g. reactor, bomb, but NOT STARSFusion - atoms joined together (extremely high temp needed) - STARS!!What happens in a red giant, white dwarf, main sequence star?

Three Types of Emissions from Radioactive Sources

Emissions from radioactive sources were initially called rays and included alpha, beta, and gamma rays. The properties of these rays were mysteriously different.

Alpha rays (+ve), could be bent by a magnetic field, and were easily stopped by a sheet of paper.

Beta rays (-ve), could be bent in the opposite direction by a magnetic field, and could penetrate paper but be stopped by an aluminium shield.

Gamma rays (neutral), were not deflected by a magnetic field, and penetrated both paper and aluminium, but could be stopped by a heavy shield of concrete or lead.

Alpha rays (generally called alpha particles) are the slow-moving nuclei of helium atoms.

Beta rays (generally called beta particles) are electrons.

Gamma ray,like all electromagnetic waves, can also be thought of as particles called photons.

IONIZATION:

ALPHA IS MOST IONIZING

GAMMA IS LEAST IONIZING