Strange

I'm not sure it does. Although, I don't suppose GR is valid for black holes with sizes approaching the Planck length. (Which would be about 27 micrograms.)

The Schwarzschild radius is defined by: [math]r_s = \frac{2 G M}{c^2}[/math] The mass of the black hole was 53 solar masses: https://www.sciencealert.com/new-ligo-virgo-gravitational-waves-neutron-stars-space-news-sept-2017 Plugging that In to the equation gives 157km: http://xaonon.dyndns.org/hawking/

What do you mean by "smallest size"? A black hole's radius is proportional to its mass. For example, the black hole resulting from the recently detected gravitational waves had a radius of about 157 km.

I would say a black hole is defined by the event horizon not by the (probably non-existent) singularity. That is where it becomes black and hole-like.

Depends on the definition of "arbitrary" I suppose. Day and year are arbitrary in the sense of not having any universal meaning (unlike, say, Planck units). But are not arbitrary in that they are based on obvious things going on in the world around us. But they could also be considered arbitrary because they don't have constant values. Of course, subdivisions of the day, such as hours and seconds (and the number of hyperfine transitions of a caesium atom) are arbitrary in both senses.

I'm sure people understand them. That is probably why they disagree with them.

It is, as far as I know, the news website for the AAAS so I guess it should be reasonably reliable as a source of science news. (But I don't know much about the AAAS, either.)

Is breaking the rules a sin? God may forgive you but I'm not so sure about the moderators. Reported.

You have already admitted that there are several classes of models that don't include an origin. The only reason I picked up on this is because I think that focussing on the origin (which we all agree that we know nothing about, and may not even exist) does not help the OP understand how the universe could be infinite or, even, larger than the observable universe. While it is, of course, possible for an infinite universe to arise from a singularity, that is a hard concept to get across. So it seems simpler, to me, to focus on the evolution of the universe from one that was always bigger than our observable universe. This entire side-discussion seems unnecessary.

You implied that the only alternative was a cyclic model. Sorry if I misunderstood that.

That comment ("idiots") was absolutely not aimed at you - just people who pop up on science forums who present their half-baked ideas as new "theories". Anyway, the alternatives to dark matter as some form of matter are various modifications of our theories of gravity: MOND is the best known: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics But there are others: https://en.wikipedia.org/wiki/Alternatives_to_general_relativity, https://en.wikipedia.org/wiki/Erik_Verlinde#Emergent_gravity_and_the_dark_universe, https://en.wikipedia.org/wiki/Dark_matter#Alternative_theories, http://backreaction.blogspot.it/2016/10/what-if-dark-matter-is-not-particle.html, https://arxiv.org/abs/1204.5571, and on and on

I just posted a model which is neither cyclic nor has an origin.

One is the Milne model: https://en.wikipedia.org/wiki/Milne_model And, not surprisingly, it doesn't behave the same as the universe we live in! (as ours is full of matter) And I'm not sure it could ever have applicability, but they are useful ways of exploring the limits of the theory. One problem with GR is that there are few exact (mathematically solvable) solutions to the equations and those that do exist are approximations (e.g. the ever popular Scharzschild black hole describes an eternal unchanging object in an otherwise empty universe. But that is a good enough approximation for many purposes.

This article might help explain it: https://www.forbes.com/sites/quora/2017/03/07/the-big-bang-was-not-a-single-point-in-time

https://briankoberlein.com/2015/02/10/beginning/

Here is one example of a model where the universe does not have a beginning: Quantum equation predicts universe has no beginning

I have given you a +1 for a wacky idea. This sounds like the sort of thing Randall might try in his What If series: https://what-if.xkcd.com/archive/ (in fact, I'm surprised he hasn't).

I think it is pretty clear it does. It says "the universe expanded from a very high density and high temperature state"; not that the universe was created or originated from ... And it says "from the earliest known periods" not "from an origin". But it goes on to say "Physicists are undecided whether this means the universe began from a singularity, or that current knowledge is insufficient to describe the universe at that time." As the model cannot go back that far, the model cannot describe the origin.

The trouble is, the problem with resolving QM and GR is a mathematical one. Without mathematics behind your idea, we can't say whether it would help or not. (And I don't have a clue what your idea is! :))

"The Big Bang theory is the prevailing cosmological model for the universe[1] from the earliest known periods through its subsequent large-scale evolution.[2][3][4] The model describes how the universe expanded from a very high density and high temperature state,[5][6] " https://en.wikipedia.org/wiki/Big_Bang (Sadly, almost all popular descriptions agree with you.)

Well, this makes a change from the (related) "there's no time without movement". It seems fundamentally mistaken. For example, we can produce solutions to the Einstein Field Equations to describe universes with no matter or energy. We can then model how space evolves over time in such a universe. So it seems that matter may be necessary to measure time but not for time to exist. But as we live in a universe full of matter, it seems kind of moot. Any question about the (ultimate) nature of anything is, by definition, philosophical. The "handmaiden of Matter" is very poetical, but doesn't really tell us anything scientifically useful.

Except we can't. The Big Bang model only goes back to a point where there is a hot, dense state (a quark-gluon plasma). Our current physics doesn't allow us to go further back than that. There are several models where that is not the case (even apart from the cyclic one). The Big Bang model describes an evolving (expanding and cooling universe) not an "origin".

Except, of course, it would. For example, the reason that sickle cell disease still exists is because it confers some resistance to malaria. On that note: http://www.bbc.com/news/health-41386849 (BBC: "DNA surgery on embryos removes disease")

There is no evidence that the universe has an origin. If the "origin" were infinite in extent then the universe could be infinite. If you "wind the clock back" on an infinite universe it can become zero sized in finite time.

This may be a key point that BB is missing. You can increase the energy of a classical wave by increasing the amplitude, without changing the frequency. Or you can split the wave into waves of the same frequency but lower amplitude. You cannot increase the amplitude of a photon. Its energy is solely determined by frequency. I found this slightly confusing so I'm not sure it will help BB!