Recent content by Bandersnatch

Present-time events at that comoving distance are indeed unobservable, but those having occurred there very early on - are. So there is a sense in which the statement is correct, and that sense is, I believe, the basis for how the size of the observable universe is conventionally defined.

What I mean here is that as time moves forward, each subsequent light cone expands, with its apex moving up along the time axis, and its basis covering more of the distance axis. Like so and The largest possible light cone has the apex at the top of the diagram, in the limit of the infinite...

The particle horizon is the mirror image of our past light cone. That's the currently observable universe, and what you're focusing on. I don't think there's any disagreement here. The past light cone, as can be seen on the conformal graph, is bounded by the event horizon, which is the maximum...

Sure. The base of the past light cone of the farthest signals we currently observe is larger in comoving extent than current size of the event horizon. But it wasn't at emission of those signals. There's no contradiction, just comparing different times. If you compare where the EH intersects...

I too hate the cheese disease.

Unless you mean something trivial, like how many galaxies we have pictures of, then that's pretty much what it is. It's the extent of the base of our past light cone. Also synonymous with the particle horizon. That's the standard nomenclature, no? For observable in principle, we have event horizon.

As was mentioned above, the observable universe is not of a fixed size. The farthest radiation received today - the CMB - arrives from beyond what was the observable universe yesterday, and will tomorrow arrive from beyond our observable universe right now. You don't need new technology to probe...

Yes. Not only is this all correct, it's the starting point for the development of relativistic view of gravity. You start by asking -what- is so special about gravity that it makes all parts of a system accelerate at the same rate, locally at least. It's not true of other forces, after all...

'photons detected' The linked paper explains this in detail.

To answer this directly - sure. If you don't have to worry about fuel. You could even walk out of a gravity well at a snails' pace, if you had a really long ladder. Escape velocity is for when you have to give your rocket one good push at some point in your launch - typically at the start - and...

What would even be a standard for credible detection here? 3 events? 10? When would they start calling Stockholm?

I remain nonplussed about these devices. The automation of the observation process is so extensive that I don't quite get the difference between this, and going outside with a planetarium app on your smartphone, to look at pictures uploaded from the HST. Other than the missing 1k in your...

More or less. In this context it's specifically an idealised 'Fermi gas', so non-interacting. You can read more about this on Wikipedia, along with maybe an article on 'degenerate matter'. But I'd much rather recommend you study that book I indicated earlier, as it should - as far as I remember...

Can you please always cite the source you're referring to? As you say, there are no atoms as such in the core, just ionised nuclei and electron gas. The source might be talking about the degenerate electron gas becoming relativistic as the electrons are forced into higher energy levels, which...

As was suggested above, these requirements are somewhat contradictory. But I'll suggest something nonetheless. Go to Open Library, and search for Dina Prialnik's 'An introduction to the theory of stellar structure and evolution'. You can borrow it for free from there. It's an undergraduate...