Unit 3: Let There Be Light NSCI 110, Origins of the Cosmos Regent University
PowerPoint Overview ▪ Hubble’s Redshift Law ▪ The Doppler Effect ▪ Age of Universe from Hubble’s redshift ▪ Georges Lemaitre & Einstein ▪ Pope’s reaction and then Georges’ Response ▪ Getting scooped on the CMB ▪ Reactions to the CMB
Redshift and Measuring Stars /
The Doppler Effect of Light ▪ – The Trumpeter on a Moving Car ▪ We do not notice this effect with light because most visible objects do not move fast enough to detect a change (with our eyes) – 𝑓𝑓 = 1 + Δ𝑣𝑣 𝑐𝑐 𝑓𝑓 0 ▪ f is the observed frequency ▪ Δ𝑣𝑣 is the velocity of the receiver relative to the source (it is positive when they are moving towards each other and negative when they are moving away) ▪ c is the speed of the wave (for the trumpet it would be the speed of sound… for a star it would be the speed of light) ▪ 𝑓𝑓 0 is the emitted frequency of the source
The Trumpet Math▪The Trumpet Player looked like he was playing a ‘C’–This wave has a frequency of 261.33 Hz–The speed of sound is 768 MPH, the car was driving at roughly 35 MPH–What did the observer hear as the car was driving towards him?
Starlight Red/Blue Shifts Each Element Produces a Unique Set of Spectral Lines
More Than Just Hydrogen
More Than Just Hydrogen
Redshift + Star Distances = New Law?
A 2015 Update The Hubble diagram of galaxies [distance vs. redshift (velocity)] from a large combined SNIa distance- indicator sample The black line (that fits the data so well) represents the d ( z ) relation expected for the current cosmology (a flat universe with mass density 30% and cosmological constant 70%) and a Hubble Constant of H o = 70 km/s/Mpc. This goes from z = 0.01 (or 140 million light years) to z = 1 (7,000 million light years)
Redshift and Measuring Stars / z = 0.14 corresponds to a distance of 1.8 billion light years
Hubble’s Law ▪ 𝑣𝑣 = 𝐻𝐻 0 𝑑𝑑 – Where v is the speed of the galaxy, d is the distance to the galaxy and H 0 is Hubble’s constant—H 0 would have to have dimensions of inverse time – If H 0 is a measure of how fast objects are moving away, at some point in the past they were touching ▪ If I told you my average speed to Richmond was 90 MPH and I find myself 98 Miles away, we know I left Regent ~1.09 hours ago – From this 2015 paper we see they model H o = 70 km/s/Mpc~ 2.3 x 10 -18 s – 1 𝑀𝑀 0 = 4.4 𝑥𝑥 10 17 𝑠𝑠 ~ 13.8 𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑠𝑠
3 Types of Redshifts ▪ Largest Effect: – The Universe’s Expansion ▪ Only seen in closer galaxies: – Movement of galaxies relative to each other (a galaxy moving towards us can have a ‘blueshift’ ▪ Tiny Effect: – A Gravitational Redshift—light can be shifted itself from the massive gravity in a galaxy – Einstein’s Theory of GR again predicts this – “It agrees exactly with the measurements of this effect”—Dr. Radek Wojtak in 2011 upon seeing new SDSS data
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- Summer '18
- Dr. Marshall Bowles
- Big Bang, Redshift, Hubble's law, CMB, Georges Lemaître