I have a question about the nature of the big bang and the universe. I’ve read a lot of popular science and cosmology and, having an English degree, I obviously have limits. My question may have been answered in my readings but not explicitly enough for my understanding.
So here goes: Until a few years ago I thought that the big bang was an event which occurred in the universe, causing the initial, explosive distribution of all of the material stuff. Since then I’ve been getting the impression that that assumption is incorrect and that the big bang, rather than being the explosive distribution of stuff in the universe, is actually the explosive start of the universe itself.
So in the former of the two beliefs, an analogy would be a tiny collection of matter in a giant space called the universe, in which the matter is distributed. The latter case would be analogous to the universe itself (and its matter (and everything else, including light and time)) being a small “rubbery”, stretchy ball which explosively starts to expand.
Are there any physicists or cosmologists who can clarify this for me?
Although the “explosion” thing is a metaphor rather than an accurate description of what happened. Inflation is not an explosion, from what I’ve understood from previous threads about this.
The phrase “Big Bang” itself must be some sort of metaphor. If this “Big Bang” happened (as current consensus holds it did) and there was nobody there to hear it (as certainly there wasn’t), did it actually go “Bang”?
Well, I don’t know if I’ve ever been whooshed this hard in my life, but yes, the “Big Bang” was intended only as a striking image by Fred Hoyle (a proponent of the rival Steady State theory) to differentiate the two theories. No one has ever claimed there was an actual, unable-to-propagate-because-of-vacuum-which-didn’t-exist-anyway-until-after-the-universe-came-into-being noise.
I just want to point out that the “Big Bang” was first proposed by Monseigneur Georges Henri Joseph Édouard Lemaître, – a Catholic priest. I don’t understand what issue has made the OP post “not religious”. Has something happened that I missed?
He was a priest who was also a scientist, and like most Catholic treatments of such there is a time and place for each but they do not need to make reference to each other. The OP is implying that the question isn’t asking about the Big Bang in any belief systems but as a scientific phenomenon. The mechanics of the event rather than whether it happened.
Hoyle claimed that his name wasn’t meant to be pejorative, but no, he wasn’t a proponent of the scientific theory.
Can someone explain why this is thought to be true, regarding time? I’ve seen posters write things like “It’s meaningless to ask what occurred before the Big Bang – it’s like asking what’s north of the north pole!”
But why is that said about time? Why this mystical assertion that time didn’t exist? Why couldn’t there have been events prior to the big bang?
Thanks for the responses everyone! Regarding vertizontal’s question about time, I believe that it’s because time is as much a part of the stuff of the universe as anything else. The fact that time is relative is wrapped up in this. (Physics-literate folks please feel free to correct me)
Disclaimer: I don’t come at any of this with a math-and-physics based understanding of it. I’m just an omnivorous reader who read Stephen Hawking’s book.
I think gravity is the important part.
Gravity, as you’ve probably heard, distorts light, and that’s just the tip of the proverbial iceberg; gravity actually distorts space and time.
Rethink of the Big Bang as something like the avenues of manhattan. They run parallel to each other, and perpendicular to the streets as you head towards the southern tip, but as you get really close to the tip, the island gets a whole lot skinnier; the avenues on the east side and on the west side converge, bending towards each other, so they’re no longer parallel and they actually get closer and closer to being parallel with the streets. Eventually they bend INTO each other. If you continued driving “downtown” / “south”, you would not end up in the water, nor would you hit a wall (and make a “Big Bang”) so much as you cease making any appreciable headway towards a more-southerly direction. If you had no compass or map and only had a sense of continued travel (defined from the beginning of your journey as “downtown bound”) you would have no way of speaking of there being any coordinate “more downtown” than the place where it loops back. The markers you’ve using — the east-west streets you pass — just stop. Hawking, if I understand him correctly, is saying that time bends as a consequence of gravity, once things get (or, rather un-get, since we’re glancing backwards in time) really dense, in such a way that time as well as space converges.
We typically think of the Big Bang as unfolding in time where time is its usually linear thing, hence a SUDDEN out-of-nothing kablooie moment and rapid expansion. But with time also bent around the corner like that (like the avenues) it’s more like time is less and less perpendicular to space, more like both space and time gradually emerging from infinity and straightening out into a linear progression of time as we know it.
I’m not sure why it’s so much harder for some people to recognize that time didn’t exist before the BB when they don’t stumble anywhere near as much at space (not the stars, not the stuff IN space, but space itself) not existing before the BB.
I think this is an important point to get in order to understand the Big Bang:
“The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point.” http://www.astro.ucla.edu/~wright/infpoint.html
But isn’t the “observable” universe emphasized simply as a clarification that that’s all we can see of the red shift? In other words, if/as our detection methods become more powerful, can we not assume (unless proven otherwise) that as we see further we will still detect the same red shift on more distant galaxies?