The Universe

Edwin Hubble & Spectra The composition of stars: hydrogen and helium How do we know?: light is analyzed from the stars with a spectroscope A spectroscope is an instrument that produces a pattern of colours and lines called a spectrum from a narrow beam of light A German optician, Joseph von Fraunhofer first analyzed our Sun and found that its light produced a pattern which was later determined ot be made mostly of hydrogen and helium

Hubble & the Doppler Effect He studied distant galaxies and their spectra What he noticed: –The spectral lines were slightly displaced from normal positions (Doppler Effect) –The Doppler effect is the change in frequency of a light source due to its motion relative to an observer (also relates to sound waves)

The Doppler Effect

Red shift & Blue shift Long waves of light associate with red spectral lines Short waves link with blue spectral lines What does this all mean? –An object moving away from an observer is lengthened-moves to the red (red-shifted) –An object moving towards an observer has shortened wave lengths-move to the blue (blue- shifted)

Electromagnetic spectrum

How does this relate to the Universe? Hubble found that most galaxies had red- shifted (meaning…) They are moving away from the observer This means that the universe is expanding In honour of this discovery: the first large space telescope was named after Hubble

Red-shift & distance from Earth A relationship exists, where the speed of the galaxy (determined by its red-shift) is directly proportional to the distance of the galaxy from Earth The outward motion happened at once and the galaxies that move twice as fast are twice the distance away This relationship is called Hubble Law, and when graphed the slope of the line is the Hubble constant

Hubble Law H 0 = /- 3.1 (km/sec)/Mpc The galaxy appears to be moving 160 thousand miles per hour faster for every 3.3 light-years away from Earth

The Big Bang Theory Cosmologist observe that at some time in the distant past the universe was extremely compact, small and unimaginably dense. Modern satellites can look back in time almost to the very beginning (approx. 14 billion years Most cosmologist believe the beginning occurred in the Big Bang

The Theory The universe began expanding with unimaginable violence from a hot and incredibly dense state to its present state. A British scientist-Hoyle coined the phrase-Big Bang

The Supporting Evidence Distance-Redshift relationship, Hubble Constant Cosmic microwave background (CMB) radiation-radiation left over from the Big Bang –Initially the universe was very hot, filled with gamma rays at short wave lengths. As the universe expanded the wavelengths expanded from gamma rays to visible rays –Today astronomers observe that CMB radiation has a wavelength of 1.07 mm (the microwave spectrum)

More on the Radiation A scientist predicted that the CMB radiation had cooled to -269 degrees Celsius In American scientists accidentally discovered microwave noise produced by the radiation left over from the big bang. It read a temperature of -270 degrees Celsius--very close to the prediction 2 satellites were lauched to read the radiation from space, COBE (Cosmic Background Explorer) and WMAP (Wilkinson Microwave Anisotopy Probe) The data gathered from both supported eachother and supported the Big Bang Theory

The Images COBE Blue is colder, yellow red is warmer WMAP

A young universe-the images captured by the satellites COBE and WMAP show a young universe at about 0.002% its present age. At this time it was very small, yet from our point of view it seems a huge shell that surrounds us. We see it in all directions as red-shifted when in fact it was still really small What does it mean?

How does this make sense The light from our Sun take 8 minutes to reach us-that means the sunlight we see existed 8 minutes ago The closest star is 4 light-years away-that means we see star light as it was 4 years ago The galaxies are 10 billion light years away- showing us what the galaxy was 10 billion years ago Remember-the universe formed 14 billion years ago

Homework AFbRAI Pg. 371 # 1-4 Pg. 376 # 1-7 Activity on Page 365 and Activity on Pg 366