Coming black hole collision -- help me to understand this NYT article

@nottelling - Yes, I understood the question you were asking about ambiguity in language, and Lergnom gave the right answer. I just thought it was interesting (to me at least) to mention some of the deeper related issues about space and time. Please feel free to ignore it if you aren’t interested.

I shouldn’t have put words in your mouth when I said you just wanted to know what humans on Earth would observe. But Einstein and others taught us that when we are confused it is good to focus on actual empirical facts like what an astronomer on Earth observes when they look through a telescope. By saying the answer is “100,000 years from now, astronomers on Earth expect to see the collision”, I hoped to give a useful, meaningful answer that was also scientifically rigorous.

Never said that “past” or “future” were meaningless - in fact, I think I said the opposite. What I said was scientifically meaningless was saying that event A occurs at an earlier time than event B.

Some events are in my past, other events are in my future, and some are neither. That’s what Einstein figured out. The collision event, when/if it occurs, happens to be in the “neither” category relative to us. And that’s what makes the distinction between past/future/neither, and earlier/later time relevant in this case.

One thing that may interest you - one of the original reasons why they invented the theory of inflation was that scientists are careful about this distinction that I’ve been talking about. (See this article, especially about causal contact).

Scientists have the expertise to know when they can meaningfully talk about the “past” and “future”. There’s an enormous scientific context that they bring to bear when they use everyday words in a technical sense. When they observed the microwave background they were definitely making an observation of our past.

I’m almost sure we can not rule anything out for the reasons I’ve been talking about. The event simply hasn’t happened yet from our perspective, so there’s no way we can make any inferences from the event since it hasn’t happened yet. That’s why I’ve been harping on making sure that the phrase “3.4999 billion years ago” doesn’t create its own set of confusions.

If the collision triggered a “new inflation”, then in 100,000 years we would see the collision and then the galaxies would “wink out” because they would “recede faster than the speed of light” from us. Then we’d all be dead in the very next instant as the boundary of the new bubble universe hits us. But we wouldn’t see any evidence until then since the inflation itself would move through our “normal” spacetime at the speed of light. Honestly, I’m not 100% sure about the inflation stuff since I’m certainly not an expert, but this is my understanding. I’m sure about normal non-inflation effects.

@al2simon – Thanks! I didn’t mean to suggest that I didn’t find your thoughts interesting; I did, enormously so!! I was just trying to clarify the nature of my question.

On the “inflation” point, I was trying to think of an example of something where the effects would be felt simultaneously across the universe without regard to distance or the speed of light, which, in my dim understanding, the original inflation of the universe was. I know I’m garbling this. It was meant to be a hypothetical example where the effects of the event would be felt faster than the speed of light all over the universe. Another far-fetched example would be that we could rule out the possibility that this event – (collision of two black holes) – caused/ will cause/ has caused the immediate and simultaneous destruction of the universe because we are still here. (Im not suggesting anyone would think such a thing would happen; it is just a hypothetical to show why theoretically past and future could have some meaning in this context.)

I talked briefly about the issue of “instantaneous” transmission. This is a real topic. As I noted, in Newtonian views, the effect of a change would be instantaneous but then we now know that this isn’t the way it works. The actual discussions about “instantaneous” have for some decades revolved more around quantum entanglement issues, which is only for very small things. I actually spent a few minutes trying to put this issue in very basic words - starting with Bell’s Theorem - but I gave up and deleted it. If you’re interested, look up EPR (Einstein-Podolsky-Rosen) and then Bell’s Theorem. The great phrase is “spooky action at-a-distance”, which is real (unless you’re a real diehard) but not for big stuff. EPR was Einstein et al’s attempt to define that spooky action as a problem and Bell basically said uh-uh it’s real. All experiments seem to verify Bell but the problem is it appears you can’t make a completely airtight, no other possibility experiment.

“Inflation” only occurred during the early universe and lasted from something like 10^-36 seconds to 10^-32 seconds after “The Big Bang” - with Jim Parsons as Sheldon! -

“The Big Bang is the theory that posits that the universe continuously expands so out of its original dense, hot state, which was characterized by high amounts of free-roaming electrons, protons and photons. After a cooling period, protons and electrons began to mix together to form hydrogen atoms that allowed light to travel through space”

In other words, the whole universe was in a hot dense state when nearly 14 billion years ago expansion started - wait! The earth began to cool, the autotrophs began to drool, Neanderthals developed tools …

(Thus ends my knowledge in this area!)