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speach
2016-May-17, 11:28 PM
Now about 16.5 billion years ago there was the 'big bang', this was a singularity that started to expand. (as I can envision it) The universe started to expand then, and continues today. To my mind this how all the galaxies are moving away from each other. The result of this would be that some where were the 'big bang' started there would be not much at all maybe nothing. Have we any idea where this "hole" is? Over to you to shoot me down in flames!

PetersCreek
2016-May-18, 12:07 AM
Mainstream consensus puts the BB at about 13.8 billion years ago. It's also thought that the proto-Universe (for lack of a better word at the moment) was very hot and very dense but as far as I know, it's not thought to have been a singularity. And according to prevailing theory(ies) there is no one single place where the BB happened...there's no center (or "hole") that everything would be pushed away from. It's thought to have happened everywhere in the Universe...so everyone, everywhere sees other distant everywheres receding from them as if they were the center of the Universe.

Reality Check
2016-May-18, 12:23 AM
The balloon analogy is a good way to visualize this, speach. Think about a balloon that is only a surface so that it is invalid to refer to outside of it or inside of it. Mark some dots on the surface. Let distances on the balloon surface get larger (it expands). Select any point on the surface and all of the dots are receding from it. There is no center to the expansion and so no "hole".

pzkpfw
2016-May-18, 12:25 AM
(Edit: reality check beat me to the "submit" button, but I'll leave this here ...)


... The result of this would be that some where were the 'big bang' started there would be not much at all maybe nothing. Have we any idea where this "hole" is? ...

That imagines the BB as an "explosion" that happened in pre-existing space, flinging everything away from that central point. That isn't what science thinks occurred.

Instead, imagine dots drawn on a balloon. (Note that the surface of the balloon is the Universe; ignore the inside and outside of the balloon, that's not relevant to the analogy.)

Now the balloon starts expanding, all of the dots are getting further from each other. There's no "hole", there's no "centre" (or, all dots can consider themselves the "centre").

Noclevername
2016-May-18, 12:49 AM
The BB is when all of space started to expand. There is no center, no hole. The name "Big Bang" may make it sound like an explosion, but that's just an analogy, and not a very good one at that.

A better comparison is the rising raisin bread, where all raisins get further away from all other raisins regardless of where they are in the dough.

John Mendenhall
2016-May-18, 01:05 AM
Three good answers. All I can add is this link:

https://en.wikipedia.org/wiki/Big_Bang

cjameshuff
2016-May-18, 01:06 AM
The BB is when all of space started to expand. There is no center, no hole. The name "Big Bang" may make it sound like an explosion, but that's just an analogy, and not a very good one at that.

A better comparison is the rising raisin bread, where all raisins get further away from all other raisins regardless of where they are in the dough.

Better? It gives the misleading impression of an object with a central point and an outer boundary, which is close to the misunderstanding speach has. The balloon analogy doesn't have these weaknesses.

Noclevername
2016-May-18, 02:30 AM
Better? It gives the misleading impression of an object with a central point and an outer boundary, which is close to the misunderstanding speach has. The balloon analogy doesn't have these weaknesses.

It does, from my POV. If you can ignore the inside of the balloon, you can ignore the boundaries of the raisin bread. No analogy is going to be perfect.

01101001
2016-May-18, 02:34 AM
Did you abandon reading that Ask an Astronomer site? For instance: Can we find the place where the Big Bang happened? (http://curious.astro.cornell.edu/physics/the-theory-of-relativity/102-the-universe/cosmology-and-the-big-bang/the-big-bang/592-can-we-find-the-place-where-the-big-bang-happened-intermediate)


No, that little point of matter that was the Big Bang was not a little point of stuff inside an empty universe. It was, in fact, the entire observable universe. There was no "outside" of that point into which it could explode.

It started everywhere.

John Mendenhall
2016-May-18, 02:46 AM
Better? It gives the misleading impression of an object with a central point and an outer boundary, which is close to the misunderstanding speach has. The balloon analogy doesn't have these weaknesses.

It's a good 3-D example, all you have to do is assume infinite dough. :doh:

Noclevername
2016-May-18, 02:48 AM
"First, assume a spherical raisin bread..."

ShinAce
2016-May-18, 03:10 AM
First, assume the galaxies are moving away from each other. Since expansion was slowing down for a few billion years and is now accelerating, you have to accept that all galaxies everywhere can begin to slow down, only to later speed up. Then you need to assume we are at the center based on deep space photos.

Second, assume the galaxies are not moving. Then the only way to get distances to change is to have space expand. As long as space expands everywhere the same, then everyone looking out would see themselves at the center. Either you say there is no center, or there are an infinite number of them. Pick one.

speach
2016-May-18, 07:04 AM
Now this thought may get move to "against the mainstream". And according to prevailing theory(ies) there is no one single place where the BB happened...there's no center (or "hole") that everything would be pushed away from. It's thought to have happened everywhere in the Universe...so everyone, everywhere sees other distant everywheres receding from them as if they were the center of the Universe.Peterscreek So the proto-universe consisted of a form of matter that we know nothing about. Then only at the BB did it form into what we recognize as the matter we see?
I think the balloon analogy is very misleading the raisins in dough is much better, dots on the surface of a balloon, which I've been told before to imagine leads to the assumption that there is a central hole.
[I]"First, assume a spherical raisin bread..."[I]Noclevername Why does the universe need to be spherical? Yes it fits with what we know about gravitational attraction, But.

Noclevername
2016-May-18, 08:17 AM
[I]"First, assume a spherical raisin bread..."[I]Noclevername Why does the universe need to be spherical? Yes it fits with what we know about gravitational attraction, But.

No, that was a joke. In science, especially in physics, you often deal with simplified scenarios for convenience. The prototypical example being a joke about a "spherical cow (https://en.wikipedia.org/wiki/Spherical_cow)".

Sorry for the confusion.

Swift
2016-May-18, 01:56 PM
<snip>
So the proto-universe consisted of a form of matter that we know nothing about. Then only at the BB did it form into what we recognize as the matter we see?

It would be a stretch to even say it was a form of matter, since it was a "form" that consisted of all matter, energy, all the physical forces... everything. Physics has no description for what existed at time zero, or in the early universe (what is called "the Planck epoch") and lasted from zero till about 10-43 seconds.

It wasn't till the Hadron epoch (10-6 seconds) that it cooled enough for protons and neutrons to form and atoms didn't start to form till about 3 minutes.

Good wikipedia article about the chronology (https://en.wikipedia.org/wiki/Chronology_of_the_universe)

John Mendenhall
2016-May-18, 04:12 PM
Now this thought may get move to "against the mainstream". And according to prevailing theory(ies) there is no one single place where the BB happened...there's no center (or "hole") that everything would be pushed away from. It's thought to have happened everywhere in the Universe...so everyone, everywhere sees other distant everywheres receding from them as if they were the center of the Universe.Peterscreek So the proto-universe consisted of a form of matter that we know nothing about. Then only at the BB did it form into what we recognize as the matter we see?
I think the balloon analogy is very misleading the raisins in dough is much better, dots on the surface of a balloon, which I've been told before to imagine leads to the assumption that there is a central hole.
[I]"First, assume a spherical raisin bread..."[I]Noclevername Why does the universe need to be spherical? Yes it fits with what we know about gravitational attraction, But.

I think you are still hung up on the idea of a point location for the BB. Forget it. Instead think of the BB as fantastically dense and fantastically hot, and consisting of everything to produce what we see today, and probably a lot more. The Universe, and by implication the BB, appears to be without bound.

Notice that I have carefully avoided the word 'infinite', which if IIRC, means 'without bound' in Greek, but in English is tied to too many people's hot button. The UT publisher, Fraser, of all people, gets it correct dead on, IMHO. Please, gentle folk, don't derail this thread with a side discussion. Just listen to Fraser,he's only got about a jillion videos.

Noclevername
2016-May-18, 06:25 PM
So the proto-universe consisted of a form of matter that we know nothing about. Then only at the BB did it form into what we recognize as the matter we see?

We have no idea if there was a proto-universe or what it may have been like. BB Theory only covers running backwards the expansion we see in spacetime today to a time when all of existence was smooshed together. Get that model too close to the beginning of time, and the physics of all our models acts differently than the known physical laws we observe today. And we can't tell if the actual physics changed, or if it's just a flaw in our ability to conceive of what happened.

speach
2016-May-18, 10:59 PM
Thanks to all, think I'm starting to get it. The BB wasn't an explosion as in a stick of TNT, It was really a change really from some thing to the matter, energy, everthing we know to day, and it wasn't from a point but everywhere at once?

Noclevername
2016-May-18, 11:23 PM
Thanks to all, think I'm starting to get it. The BB wasn't an explosion as in a stick of TNT, It was really a change really from some thing to the matter, energy, everthing we know to day, and it wasn't from a point but everywhere at once?

Basically, except that we don't know if the "something" that changed into "our universe and everything in it including all time and space", might have been "nothing at all". Which is as big a change as there is.

See what I meant about the physics being different? Nothing into something is impossible in our present universe.

Reality Check
2016-May-19, 12:53 AM
I think the balloon analogy is very misleading the raisins in dough is much better, dots on the surface of a balloon, which I've been told before to imagine leads to the assumption that there is a central hole.
All analogies are misleading to some extent, speach. They become better when the misleading parts are emphasized, e.g. the balloon has no interior or exterior and that the "raisins in dough (http://cmb.physics.wisc.edu/pub/tutorial/hubble.html)" has no exterior.

DaCaptain
2017-Jan-01, 05:56 PM
I'm getting stuck on the expanding universe theory. To me an expanding universe has to expand into something and that there's a direction to the expansion. But if the universe is infinite in size is it really expanding? Or is it more likely that it's shifting around. Which means there are eddies and currents within the universe that we haven't identified yet. That thing we call the big bang is really one of these many currents.

Noclevername
2017-Jan-03, 04:50 AM
Nope, no direction. Everything seems to be evenly getting further apart from everything else.

Think of it not as the Universe expanding "outward", but as all spacetime everywhere foaming up and taking stuff with it. (Without, needless to say, bubbles).

John Mendenhall
2017-Jan-03, 06:21 AM
Thanks to all, think I'm starting to get it. The BB wasn't an explosion as in a stick of TNT, It was really a change really from some thing to the matter, energy, everthing we know to day, and it wasn't from a point but everywhere at once?

Bingo ! You got it.

PetersCreek
2017-Jan-03, 08:18 AM
Which means there are eddies and currents within the universe that we haven't identified yet. That thing we call the big bang is really one of these many currents.

DaCaptain,

This is the Q&A forum where one may get mainstream answers to questions. Please do not argue against those answers or make against-the-mainstream assertions.

Strange
2017-Jan-03, 09:14 AM
I'm getting stuck on the expanding universe theory. To me an expanding universe has to expand into something and that there's a direction to the expansion.

This is where the "balloon analogy" comes in. If you think about the points on the surface of the balloon (note that is important to remember we are only talking about the 2D surface as an analogy for 3D space) then you can see that every point on the surface gets further away from all the others as the balloon expands. There is no overall direction (apart from "away" from every point).


But if the universe is infinite in size is it really expanding?

Think of the number line: 0,1,2,3,... to infinity. If you double all the numbers (0,2,4,6,...) then they are twice as far apart, but the line is still infinitely long. It don't need to expand "into" anything.

You could think of it as decreasing density, if that is easier.

Cougar
2017-Jan-03, 01:25 PM
It wasn't till the Hadron epoch (10-6 seconds) that it cooled enough for protons and neutrons to form and atoms didn't start to form till about 3 minutes.
Good wikipedia article about the chronology (https://en.wikipedia.org/wiki/Chronology_of_the_universe)

I think it's better to say, like the chronology indicates, that protons and neutrons were bound into atomic nuclei between 10 sec - 1000 sec. But it was still too hot for these nuclei to capture and hold onto any electrons. It took another 380,000 years for the expanding universe to cool to around 4000 K and to allow neutral-charged atoms to 'form' out of the charged soup of protons and electrons.