... If the universe is expanding
The universe is expanding.
then it must have a beginning.
It has a beginning.
If you follow it backwards in time, then any object must come to a boundary of space time.
We are not able to follow any "object" - whatever this is - backward in time.
You cannot continue that history indefinitely.
If natural history would be endless it should be no problem to see this.
This is still true even if a universe has periods of contraction.
This theory is proven to be wrong physically since a very long time meanwhile. The reason why it is wrong has to do with entropy.
It still has to have a beginning if expansion over weights the contraction. Physicists have been uncomfortable with the idea
¿Uncomfortable? What's that in natural science?
of a beginning since the work of Friedman
Friedman - who is Friedman?
which showed that the solutions of Einstein's equation showed that the universe had a beginning.
Ah - the cosmological constant Einsteins chose to nullify the expansion of the universe. That's why you speak about Friedman. Friedman was right that the universe was dynamic - but this "knew" Einstein before too, because he had corrected this result (="Meine größte Eselei"). It was Georges Lemaitres - who was - I'm sure you do not like to hear this - a priest of the holy catholic church, who combined a dynamic universe with the Law of Hubble and the redshift of the starlight and found the "big bang" which he had called "primeval atom" - (German: "Uratom" - a very nice word).
The problem with a cyclical universe is with the 2nd Law of Thermodynamics. If it is a periodic universe then the entropy will increase with each cycle. The 2nd Law of Thermodynamics is a fundamental law of nature which tells us that entropy can only increase or stay the same. Entropy can never decrease.
Exactly.
Which means that in a finite amount of time, a finite system will reach a maximum state of disorder which is called thermal equilibrium and then it will stay in that state. A cyclical universe cannot avoid this problem.
It is possible for matter to have a beginning.
I would say it is impossible for matter to have a beginning - the only reason why it's not impossible is the existence of matter. But meanwhile learned even the bumblebees to fly with the help of the laws of aerodynamics.
In a closed universe the gravitational energy which is always negative exactly compensates the positive energy of matter.
Or not.
So the energy of a closed universe is always zero.
That's why we are not existing and in every point of the universe could exist an endless number of universes.
So nothing prevents this universe from being spontaneously created.
If it has no energy because if the sum of energy = 0 then it is not existing.
Because the net energy is always zero.
Which net?
The positive energy of matter is balanced by the negative energy of the gravity of that matter which is the space time curvature of that matter.
The geometry of the space-time is flat. Why?
There is no conservation law that prevents the formation of such a universe.
The only problem is that you don't have any space, time and energy or matter. You have mathematics. But mathematics is only a special form of rationality. So 'you' say "
in the beginning was rationality". I guess I understand a little better now, why Professor Zeilinger said once it looks like "In the beginning was the word". (Word =Logos)
Only to make this clear again. Quantum mechanics is only physics of this universe here since it is existing.
if something is not forbidden by conservation laws, then it necessarily happens with some non-zero probability.
That's bullshit. We don't see other universes - nor do you know wherein this universes should exist nor what the uterus of this universes would be. And if our universe bears universes as a result of the own quantum mechanics then we should be able to find out that we are pregnant and/or mothers.
So a closed universe can spontaneously appear - through the laws of quantum mechanics - out of nothing. And in fact there is an elegant mathematical description which describes this process and shows that a tiny closed universe having very high energy can spontaneously pop into existence and immediately start to expand and cool. In this description, the same laws that describe the evolution of the universe also describe the appearance of the universe which means that the laws were in place before the universe itself.
I would say you speak bullshit on a high level of bullshit, that's all. "Evolution" is for example a natural law, which needs biological organisms. I doubt about that this word "evolution" has only a little to do with this what happens when fundamental forces freeze out. The biological evolution needs a genetic structure. And we know in this context only the universality of the gene code of all life on planet Earth. And we do not even understand this structures really, but we kill the life of our planet.