Physics as a Creation Myth II: the nightmare continues

Probably due to Geoffrey Clayton LSU

The Story so far

Ingredients for a creation myth:

Our Scales

  • Hence the "critical density" ρ₀ ~ 9 x 10-27 kg m-3 ~ 5 Hydrogen Atoms m-3
  • we use
    \color{red}{ \Omega = \frac{\rho }{{\rho _0 }}}
  • Ω > 1 Universe come to nasty end in ~ 50 x 109 yr.
  • Ω = 1 Universe expansion slows down asymptotically : "critical universe"
  • Ω < 1₀ Universe expands forever

6) Things were so much simpler back then

It is believed that the first nine inhabitants who had descended from the skies were sexless and sinless and lived on a kind of flavoured earth. Their appetites grew and when they took to eating a sort of huskless rice which cooked itself they became gross and heavy, developed sex and after it crime because they had to work for a living Kachin Myth

Cosmic Microwave Background Radiation

Early universe must have been very simple: there can have been no stars or galaxies.
Have to get above atmosphere and point away from Milky Way

Subsequent values came from balloon flights:

Finally COBE (Cosmic Background Explorer: 2006 Nobel Prize for Mather and Smoot) launched 1990:

Note the perfect Black Body curve.

Where does it come from?

Photon freezeout:

More exactly: can calculate
If we are moving through CMBR we would expect to see it "warmer" in front and "colder" behind.
  • Blue ↔2.721 Kelvin
  • Red ↔2.729 Kelvin
Quantatively:
So need a new satellite: WMAP

So what is this Dark Matter?

a) What the hell? i.e. what is the dark matter?

b) Why the hell? i.e. why is Ω~1 (after all it could be anything?)

What the hell:

  1. Brown dwarfs
  2. Hydrogen gas
  3. Jupiters
  4. Hydrogen rain
  5. Low surface brightness galaxies
  6. Maxi Black holes
  7. Mini Black holes
  8. Neutrinos
  9. He H +
  10. Modified 1/r² law
  11. Axions
  12. Weakly Interacting Massive Particles (WIMPS)
  13. Magnetic Monopoles
  14. Majorons
  15. Photinos
  16. E8 shadow matter
  17. Cosmic Strings
Which is it? We don't know! However, all of the above have problems.
The Generic Candidates for Dark Matter :
  1. Baryonic (BDM): (we use this as shorthand for "ordinary matter") maybe in some odd form e.g. rocks
  2. Hot (HDM) light particles e.g. ν's
  3. Cold (CDM): heavy (usually) particles e.g. WIMPs
The Bullet Cluster
Combination of lensing (blue) and X-rays (red) in the bullet cluster:
Strong evidence for non-interacting dark matter:
  • X-ray emitting material is gas, so gets stopped in collision
  • dark matter gets carried along

What the hell:

WIMPS

Seem like the best bet.... Generically behave like very heavy neutrinos.
In solid, nucleus will recoil and transfer energy to lattice, flipping superconductor or sending off ballistic phonons. DEAP (Kevin Graham): will use 1 tonne of liquid argon.

Where did the galaxies come from?

There is confirmation of the general CDM/WIMP picture from the microwave background measurements:
Hence Scenario
face face face face face
Can simulate structure formation with (massive) n-body codes (n = 107 gravitating objects): on the large (super-cluster) scale. Note that we get a sort of stringy structure, which looks like what we observe
Or on scales of galaxies.

{Performed at the National Center for Supercomputer Applications by Andrey Kravtsov (The University of Chicago) and Anatoly Klypin (New Mexico State University).

Why the hell?

b) Why the hell? i.e. why is Ω~1 (after all it could be anything?)

At any time, critical density is given by
\color{red}{ \rho _0 = \frac{{3H^2 }}{{8\pi G}}}
and
\color{red}{ \Omega {\rm{ = }}\frac{\rho }{{\rho _0 }} = \frac{{{\rm{actual\_density}}}}{{{\rm{critical\_density}}}}}
\color{red}{ \Omega \left( t \right) = 1 + \left( {1 - \frac{1}{{\Omega _0 }}} \right)a^2 }
  • If Ω < 1, then it decreases away from 1.
  • If Ω > 1, then it increases away from 1.
  • If Ω = 1, then it stays 1 forever
This is the "flatness problem"
Since we measure Ω now ≈ .1...this means that at the time of the BB, Ω ≈ 1 - 10-60

i.e. Ω = 1 is an unstable critical point.

If the universe started out at 10-44 s with (say) Ω = 3, it would last ≈ 10-35 s (!!!!)

Dark Energy

And just when you thought it was safe to go out at night....

Luminosity distance "standard candle"

If Luminosity is known, then we can get the distance:
Type 1a Supernovae Mv = -20 allows us to measure out to 3000Mpc
  • Obviously the universe is slowing down (decelerating).
  • Hence importance of 1a supernovae: since we know luminosity, we can get Ωmatter directly.
  • Unfortunately it doesn't work .....
Only way we can get this to work is to add an accelerating component to the universe: something that adds energy as the universe expands

CFHT

Canada-France Hawaii Telescope (CFHT)

SuperNova Legacy Survey

(U of T and others) now provides best data from CFHT

What can dark energy be?

List of all well-motivated models for dark energy
However, there are major problems (what, more?).

Note in Passing

There have been 3 scientific revolutions, all devastating for man's dignity.

Statutory Warnings

All of this depends on the assumption that type 1a SN are always the same at 4x109 Lo, even at z = .5. Effect disappears if some (unknown) effect reduces L by 30%

Anthropic Priniciple

Warning: for the rest of this course, you are on the hairy edge of science!

Relatively small number of parameters describe universe
Parameter Value Definition Measured Comments
G 6.673x10-11 Grav. const Lab
c 2.998x108 Speed of Light Lab
α 1/137 Strength fo EM coupling Lab
mec2 511 keV Electron mass Lab
mPc2 937 MeV Proton mass Lab
mnc2 939 MeV neutron mass Lab
H0 70±7 km s-1Mpc-1 Hubbles constant Hubble
TCMBR 2.726K CMBR temp COBE/WMAP
ΩB .03±.01 Nucleon density WMAP, nucleosynthesis Baryon density
Ωγ & ν 3.4x10-5 CMBR + BBN Uncertainty due to ρc, assumes mν = 0
Ωdm .26±.02 CDM density Spirals/Galaxy clusters
ΩΛ 0.74 Curvature energy Sn 1a
Ω0 1.01±.02 Total energy

Anthropic Principle:

We've missed a few constants, but there are enough here so you can design a "Build Your own Universe" kit
e.g.How old is the universe?
e.g. Could the forces in nature be any different?
e.g How Dense is the Universe?
Anthropic arguments extend all the way from the physical constants and the masses and charges of the fundamental particles, to the gross properties of the universe...

7) So what happened before?

Then was not non-existent nor existent
There was no realm of air, no sky beyond,
What covered in and where? and what gave shelter?
Who verily knows and who can here declare it
Whence it was born and whence came this creation
He, the first origin of creation,
whether he formed it all or did not form it.
He verily knows it, or perhaps he knows not.
The Rig Veda X.129 (Hindu)

Note a hidden assumption in all of this:

Superstrings and the like:

We have seen that gravity curves space: in a sense, this is going to a larger number of dimensions.

And so finally

8) What a beautiful story!