We have now understood (?) most of the basic ideas: however there are a number of very speculative ideas which may be confirmed over the next few years.....
A sampling......
F = GM₁M₂
R²
modifed by GR gives us
No known conflicts between GR and experiment, so maybe we should quit while we are ahead .........Are we sure this is correct?
One tiny experimental problem:
| Anomalous acceleration of Pioneer 10 and 11 Note this does not seem to be distance dependent | |
| "Our previous analyses of radio Doppler and ranging data from distant spacecraft
The extended Pioneer 10 data set spans 3 January 1987 to 22 July 1998. [For Pioneer 11 the shorter span goes from 5 January 1987 to the time of loss of coherent data on 1 October 1990.] With these data sets and more detailed studies of all the systematics, we now give a result, of aP = (8.74 ±1.33) x 10-10 ms-2. Lets hope it goes away! |
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And God said " Let us make man in our own image, after Our likeness, and let them have dominion....over all the earth
Genesis I.26
Not only is this the best of all possible worlds, it is the only observable, of all possible, universes.
Weak Anthropic Principle:
We see the universe the way we do because locally it is suitable for our existence
Strong Anthropic Principle:
The laws of the universe are such that it can become self-aware
Logical Anthropic Principle (Carter, 1974)
...all properties of the universe must be consistent with the presence of intelligent beings.Methodological Anthropic Principle
...the 'fine-tuning' is only apparent, not fundamental.Teleological Anthropic Principle (Barrow and Tipler)
...the universe is habitable SO THAT intelligent life can evolve.Extremely Strong Anthropic Principle:
The universe exists to produce ...PHYSICISTS!
e.g.How old is the universe?
Physicists are made of carbon, Carbon is not made in the big bang. The universe cannot become self-aware until the first stars have completed their life-cycle.
Age of Universe > 1 Billion years
e.g. Could the forces in nature be any different?
Nuclei exist because of subtle balances between (1) Repulsive Electric Force, and (2) Attractive Nuclear Force
For heavy nuclei, (1) overwhelms (2), so they are unstable.
If the electromagnetic force were 10% stronger
Then no nuclei except hydrogen would exist,
so no chemistry
so no biology
so ...NO PHYSICISTS!
If the electromagnetic force were 10% weaker
Then the di-proton is stable,
nuclei form too easily
Stars burn too fast
No time to evolve Intelligent Life...NO PHYSICISTS!
e.g How Dense is the Universe?
Low Density (e.g., Ωi < 1-10-60)
Universe Expands too fast
no Galaxies
no stars
no planets ...NO PHYSICISTS!
High Density
Universe forms clumps
But collapses back to Big Crunch much too early
No time to evolve life ...NO PHYSICISTS!
Gravitational Constant: G -> 1.000001G
Stars form, burn more quickly
Planets develop
Insufficient time for evolution of life ...NO PHYSICISTS!
The 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...
But the Goldilocks Universe:
Critical Density Ω = ρ/ρc = 1
Just lumpy enough to make galaxies
and hence stars
And ...PHYSICISTS!
Is this a reasonable scientific theory?
The anthropic principle gives little or no room for making predictions, upon which to conduct tests. The teleological principle verges on theism.
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)
What happened before the Big Bang?
There is a special hell reserved for people who ask that question.
George Gamow
Cannot conserve energy (or more precisely, entropy increases every bounce).
2nd Law of Thermodynamics leads to: For a closed system (eg the universe?), entropy (degree of disorder) always increases towards a maximum, and energy always decreases towards a minimum. Referred to as the 'heat death of the universe'.
Is the universe a closed system?
Quantum mechanics tells us that you don't need to conserve energy, provided you don't do it for very long...
ΔE Δt > h/2π Heisenberg's uncertainty principle: |
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If you borrow no energy, you can do it for an infinite time (!)
If the energies exactly cancel, then you can create universe ex nihilo!
Why does the universe get created?
Universes tend to happen from time to time!
Any part of our universe could achieve the conditions required to trigger inflation. Hence it could give rise to a new "daughter universe". ...Our Big Bang is only for our region of the universe...
Which takes us to...
Many systems in physics show "spontaneously broken symmetry"
e.g. a ferromagnet is made up of electron spins which can point:
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What actually happens is a bit more complicated: if you take, eg, a slab of Fe and cool it, different parts will choose different magnetic dipole directions.
These are domains: you can make them all the same by (e.g.) putting the slab in a magnetic field.
Theories of matter work in a somewhat similar way: we can have (e.g.) the size of the electromagnetic coupling chosen differently in different parts of space (actually, it's usually a phase factor: q = qeiφ) This can't be seen as long as it varies smoothly from one point in space to another
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However if the universe starts off very hot, these are arranged randomly. When the universe cools, bits of space can be trapped with different values.
There are three possible structures:
Monopoles behave like extremely massive particles (and hence could be related to dark matter). Domain walls vanish in most models
Cosmic strings are the most interesting, since they behave like infinitely thin, long loops of string with a mass of 1020 kg/m, maybe mass equal to unification energy.
How would we see them? What would they do? and talking of strings....................
We have seen that gravity curves space: in a sense, this is going to a larger number of dimensions.
| Kalusza-Klein showed that one could include E-M along with gravity by adding a fifth dimension, but making it compact |  |
To include all the other forces in nature (strong and weak) we need to go to a 10-dimensional space.
You hadn't noticed that the universe is 10-D tsk-tsk.......
6 of the dimensions are compact (R ≈ 10-33 m), and can be multiply-connected (i.e. can be toroidal or dough-nut shaped).
All particles (quarks, photons, electrons.....) are 2-D strings in this 10-D space.
For the first 10-38 s the universe contained....
Nothing! No forces, no particles! Nada!
Then the extra dimensions curled up and became compact => Forces => Particles => Atoms => ...PHYSICISTS!
| Sakharov (1985) suggested that the rules of physics need not be the same in going from one universe to the next: (e.g.) the electromagnetic coupling could be set arbitrarily in the first 10-30 s |  |
And so finally
8) What a beautiful story!
In the beginning, God created the heaven and the earth. And the earth was without form, and void; and God realised that this was not a very good way to start, so God said, Let there be a reinitialisation, and because God was God, he was able to start over.
In the beginning, God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the spirit of God moved upon the face of the waters.
And God said, Let there be light, but God had forgotten to create electromagnetic interactions, so there was no light, so God said, Let there be a reinitialisation, and because God was God, he was able to start over.
In the beginning, God created the heaven and the earth. And the earth was without form, and void; but this time God decided to leave himself plenty of room for manoeuvre, so he created the heaven and the earth to have ten dimensions.
But then God realised that this was a very complicated way to run a universe, so God said, Let there be a reinitialisation, and because God was God, he was able to sta.....
But God had forgotten shlosha hefsaydim v'ato bachutz, which being translated means Three strikes and you are out, so God was stuck with the Universe.
So the Spirit of God moved through the heaven and on the earth and commanded that the extra dimensions should curl up on themselves, and become compact. And God looked upon it, and saw that while it was not actually good, it was better than it might have been, because at least he had light.
The First book of Moses, called Genesis, (erratum)