Chapter 12 Flashcards
(50 cards)
How was the conclusion reached that the early universe was hot?
If the universe was cool, then everything would have ended up as Helium
What was predicted by Gamow?
light from long distances away will not be visible but instead will be redshifted
What does the fusion of two helium nuclei produce?
The unstable isotope Beryllium
This promptly decays back into 2 nuclei
What is the stability gap?
The issue of getting over the hump of creating Beryllium.
When Beryllium is formed, it decays. How can this give way to any other element?
How can helium be converted to carbon?
Through the Triple Alpha Process
How does the triple alpha process work?
Though Beryllium is unstable, there will be some of it present that can capture helium nuclei at high temperatures and densities. This will form Carbon
Where was Carbon formed?
Stars. The early universe never had sufficiently high densities or temperatures to make Carbon
What is responsible for all elements heavier than carbon?
Stars (up to Iron formed in the actual lifetime of the stars, the rest are made in type 1a supernovae)
How does CMB prove that the Big Bang happened?
CMB was a natural outcome of the Big Bang but it did not logically follow from the steady state theory
What happens to the state of the universe the further back in time you go?
The universe gets denser and hotter
What is the radiation era?
The first several thousand years of the Earth’s existence where radiation dominated over matter
What is radiation pressure?
The buffeting of photons
EG comets tails point away from the sun because they are buffeted by the Suns photons
When does a pressure force arise?
When the energy contained in a volume is able to exert a net force on a surface
What effect des pressure have on the rate of expansion of the universe?
It decelerates the rate of expansion
This is because it is stress (energy) which participates in gravity
How can you create matter?
Matter can be create from energy as denoted in e=mc^2
What is the state of thermal equilibrium?
The state where all photons have the same energy
At a sufficient temperature, what can happen when two photons collide?
They create a particle and its antiparticle
How hot approximately does the temperature need to be to make a particle and an antiparticle?
10^13 K
What happens when an antiparticle and a particle are created?
The particle and the antiparticle annihilate each other
If the particle and the antiparticle destroy each other, how are we in a matter dominated world now?
There is a tiny bit of leftover matter when the particle and the antiparticle react. This accumulated over time
What is the ultimate goal of particle physics?
To find a ‘theory of everything’
What is the Theory of Everything?
A theory that encompasses all particles and forces, showing them to be manifestations of an underlying simplicity
What is the weakest fundamental force?
Gravity
What is the Planck time?
The earliest time that our modern physics can explain
