NSCI110_Unit 3_The CMB(1).pdf - Unit 3 Let There Be Light...

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