Please explain the statement "the big bang happened everywhere at once"

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  • #51
this discussion about the big bang happening everywhere at once because its a mater of time not space. implies the universe is everywhere at its beginning it kind of puts expansion into question as opposed to redistribution of what's in the universe.
 
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  • #52
dragoneyes001 said:
it kind of puts expansion into question as opposed to redistribution of what's in the universe.

What do you mean by this? "Expansion" of the universe has a precise technical meaning (and that meaning matches what we observe). What does "redistribution" mean?
 
  • #53
we observe expansion of the mater within the universe (everything getting further apart from everything) but what makes us sure the universe is not static and the mater is simply expanding within a pre-existing space however big or infinite
 
  • #54
dragoneyes001 said:
what makes us sure the universe is not static and the mater is simply expanding within a pre-existing space however big or infinite

We know the universe is not static because "static" also has a precise technical meaning, and it does not match what we observe for the universe as a whole. If the universe were static, there would be some worldline we could follow through spacetime along which physical quantities of interest (such as the average density of matter) would not change. But there isn't; no matter what path we choose through spacetime, all of the key physical quantities that describe the universe as a whole change with time. That means the universe is not static.
 
  • #55
there's no way that all the observable matter can be moving within a pre existing space?
 
  • #56
dragoneyes001 said:
there's no way that all the observable matter can be moving within a pre existing space?

If we go by models that are consistent with GR, no; the only GR models we have that match observations do not have a "pre-existing space" into which the universe expands. ("Eternal inflation" models complicate this somewhat, but what I've said is still basically true, AFAIK, with them as well.)

Even if we put aside that theoretical fact, how would we tell, physically, that there is a "pre-existing space" into which the universe is expanding? How would we observe it?
 
  • #57
if its a void into which everything we can observe is expanding within. there wouldn't be a way of observing it as an it. the only effect it has is being there to allow expansion within its boundaries if it has any

not trying to be contrary just trying to grasp why we're sure the universe is limited to what we can observe of it.
 
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  • #58
dragoneyes001 said:
the only effect it has is being there to allow expansion within its boundaries if it has any

Why is it necessary for that? Why must there be something extraneous to the universe "to allow expansion"?

dragoneyes001 said:
just trying to grasp why we're sure the universe is limited to what we can observe of it.

Who said we're sure of that? According to our best current model of the universe, it is spatially infinite, so what we can observe of it is certainly not all there is according to that model. We may end up having to modify the model based on future observations, but even if we do, I don't think any physicists are advocating picking models based on the assumption that the universe is limited to what we can observe of it.

However, saying that there is more to the universe than what we can observe is not, by any means, the same as saying there is some pre-existing "space" into which the universe is expanding. There doesn't have to be any such thing for our current model (including its prediction that the universe is spatially infinite) to be valid.
 
  • #59
dragoneyes001 said:
there's no way that all the observable matter can be moving within a pre existing space?
No. That would mean that there is an empty space outside of what contains all the matter/galaxies in the universe. That would make the universe have a center of gravity/mass toward which everything would be attracted and, I assume you mean, a center from which the expansion is occurring. This would be observable in the motion and distribution of galaxies. As would the "edge" of this expansion if it existed and was inside our horizon.
...just trying to grasp why we're sure the universe is limited to what we can observe of it.
That's not part of the theory either. In fact, it is near certain that we cannot see all of the universe. Since a lot of your questions are based on mistaken beliefs about what the Big Bang Theory says, it would be helpful if you read-up on it some. It may correct many of these misunderstandings more easily. The wiki on the Big Bang and its children have a lot of this information. For example, there is an entire wiki on "the observable universe", which discusses why what we observe isn't all that there is and why we don't know if the universe is finite or infinite:
http://en.wikipedia.org/wiki/Observable_universe#The_universe_versus_the_observable_universe
 
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  • #60
Take a tiny ball for an example, then inflate it, where would the tiny ball geographically be in the new,large ball? It would be the large ball so the geographical location would be defined as everywhere. The Universe began as an infinitely dense and infinetly small point in space time (if it existed). Any events before the Big Bang would not affect it and would therefore be undefined.
 
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  • #61
Quds Akbar said:
The Universe began as an infinitely dense and infinetly small point ...
No, it did NOT and that in fact is the point of this thread. You should read threads before you reply.
 
  • #62
If space did not exist before the Big Bang but it exists now does that mean it is made/composed of something? what is it ? Is space a "field" just like electric, magnetic , gravitational and Higgs field ?
 
  • #63
Monsterboy said:
If space did not exist before the Big Bang but it exists now does that mean it is made/composed of something? what is it ? Is space a "field" just like electric, magnetic , gravitational and Higgs field ?
This is a somewhat contentious subject, but the consensus is that space is not "something" tangible, it is just a framework in which things happen and descriptions such as "stretches", "bend", "curves", etc. are a description of the geometry of space-time, not a literal description of space.

Whether anything existed before the Big Bang Singularity is another subject of debate but the "Big Bang Theory" has no comment on it, being just a description of how the universe has evolved since one Plank Time after the singularity.
 
  • #64
Do you know what a field is, what it means, and what it is not? An issue here on PF is naivete of space, time, dimensionality, proof, falisifiability. Many of our correspondents are un-read in the topic upon which they are commenting.
 
  • #65
Doug Huffman said:
Many of our correspondents are un-read in the topic upon which they are commenting.
So ? Is there any rule that only those people who have a background in the subject should comment on it ? I ask questions out of curiosity and anybody who knows better can answer or correct me.
 
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  • #66
Edit: It seems that there were some incorrect statements in my post, so I've removed it.
 
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  • #67
jack476 said:
My understanding:

Start with the concept that locations in space are separated not just by a measure of distance but also a length of time, the time needed for a phenomenon to propagate from one location to another. So if an object one light year away changes color from blue to red, then I can't know about it for one year, because that signal takes a year to reach me, and it is impossible for me to know about it before that time. Thus, I am not just one light-year away from it in space, but also one year away from the object in time.

So let's say I have a hypothetical infinitely long measuring tape, and I were to try and measure the distance between where I'm sitting now and the edge of the universe. What I'd see from my own position is that, as the other end of the tape gets closer and closer to the edge, it begins to compress so that the marks on the tape become closer and closer together, until eventually the distance between two marks is infinitesimal, that is, infinitely small. This represents space becoming smaller and smaller as I go further away from myself in distance, and therefore am measuring space as it was further back in time. The term "singularity" in this sense refers to this asymptotic decay: it couldn't have been 0, but it was infinitely small, but infinitely small is not 0. In theory, we can say that there was a "big bang" that happened about 13.7 billion years ago because that's when there is an asymptote in those calculations, ie, a "singularity" at -13.7 billion years. And so far, experiment agrees with theory.

And the reason we can say it happened everywhere at once is that the above is true no matter where I try to measure from.
There are a couple of flaws to this post, the post serious being that it is predicated on their being an "edge" to the universe. There isn't.
Second, I'm not clear just what you're saying about the tape measure, but if I DO understand what you are saying, it is incorrect as well.
 
  • #68
phinds said:
There are a couple of flaws to this post, the post serious being that it is predicated on their being an "edge" to the universe. There isn't.
Second, I'm not clear just what you're saying about the tape measure, but if I DO understand what you are saying, it is incorrect as well.
Okay. Could you explain please?
 
  • #69
jack476 said:
Okay. Could you explain please?
No edge means just that. No edge. An edge implies a center and a center implies a preferred frame of reference and we know empirically that such does not exist.

Your statement about the ruler seems to imply that a MEASURE of distance changes over distance and/or time but that is false. The distance between things in the early universe was less than it is now, but the MEASURE of distance has not changed.
 
  • #70
phinds said:
No edge means just that. No edge. An edge implies a center and a center implies a preferred frame of reference and we know empirically that such does not exist.

Yes, but I meant that if you look out far enough, don't you see things as they were in the past? So from the perspective of some observer, if you looked out far enough, wouldn't you eventually see space becoming infinitely compressed to a point where you can't see any further?

Your statement about the ruler seems to imply that a MEASURE of distance changes over distance and/or time but that is false. The distance between things in the early universe was less than it is now, but the MEASURE of distance has not changed.

Because space was smaller, and the marks on the ruler that are further away from the observer from the perspective of the observer would start to appear closer and closer together, right? I'm not saying that the measurements are changing, but if there is a mile-long segment of the ruler far away from the observer with a length locally of one mile, to an observer far away won't it look smaller because space itself was smaller?
 
  • #71
jack476 said:
Yes, but I meant that if you look out far enough, don't you see things as they were in the past? So from the perspective of some observer, if you looked out far enough, wouldn't you eventually see space becoming infinitely compressed to a point where you can't see any further?
Yes that's correct, but it does not change the measure of distance so your example with the rule is ill-stated at best.
Because space was smaller, and the marks on the ruler that are further away from the observer from the perspective of the observer would start to appear closer and closer together, right? I'm not saying that the measurements are changing, but if there is a mile-long segment of the ruler far away from the observer with a length locally of one mile, to an observer far away won't it look smaller because space itself was smaller?
Yes, but again, I interpreted it as meaning that the size of the ruler shrank. I don't see what other meaningful interpretation can be put on your original statement.

It sounds to me like you understand what's happening but chose a poor way to describe it.
 
  • #72
phinds said:
It sounds to me like you understand what's happening but chose a poor way to describe it.

Yea, that happens to me a lot. It's kind of a problem for me. Sorry :/
 
  • #73
Doug Huffman said:
Do you know what a field is, what it means, and what it is not? An issue here on PF is naivete of space, time, dimensionality, proof, falisifiability. Many of our correspondents are un-read in the topic upon which they are commenting.
the same could have been said of the people proposing that the world was round and not the center of the universe by the scholars of the day before they tortured and imprisoned the detractors of those current beliefs. falsification is usually by people trying to protect their position not by people trying to ask about a subject. over history many advances in our current understanding of the sciences as well as advances in technology come from people outside of the very specialties they advanced because they brought fresh perspectives with them.
 
  • #74
dragoneyes001 said:
the same could have been said of the people proposing that the world was round and not the center of the universe by the scholars of the day before they tortured and imprisoned the detractors of those current beliefs. falsification is usually by people trying to protect their position not by people trying to ask about a subject. over history many advances in our current understanding of the sciences as well as advances in technology come from people outside of the very specialties they advanced because they brought fresh perspectives with them.
Say your car breaks down and a guy starts telling you it's the fault of the carburator being clogged, or the alternator outputting too high a voltage, and says he thinks he can fix it. However, when asked he can't explain what these parts are or do, nor point to where they are. In fact, you're pretty sure he called the radiator a fuel tank. Would you leave your car to the guy or ask a professional mechanic to fix it for you?

The myth of the outsider revolutionising a field is very tempting to fall for, as it feeds on the thirst for fame and glory every single one of us have harboured at some time in their lives. It's about being the underappreciated underdog that shows all those stuck-up arrogant eggheads that he was right and they were wrong (and gets all the girs/guys, presumably).

In reality, that never happens. All the "outsiders" that ended up changing the scientific paradigm weren't random people off the street, willy-nilly arranging words whose meaning they don't understand - they were all learned in the subject and knew what they were talking about. Yes, the fresh perspective is important, but that usually translates to people making major breakthroughs early in their careers - often in their twenties - simply as soon as they managed to absorb all the prerequisite knowledge.

As for being tortured for saying the Earth was round:
1.You're probably referring to the Catholic Church and Holy Inquisition - an organisation claiming access to infallible truths which is more or less the opposite of science.
2.Even they never did that. That the Earth was round was known among learned men at least since Eratosthenes. The moral of the story: ignorance is not a virtue and empty mind does not equal open mind.
 
  • #75
dragoneyes001 said:
the same could have been said of the people proposing that the world was round and not the center of the universe by the scholars of the day before they tortured and imprisoned the detractors of those current beliefs. falsification is usually by people trying to protect their position not by people trying to ask about a subject. over history many advances in our current understanding of the sciences as well as advances in technology come from people outside of the very specialties they advanced because they brought fresh perspectives with them.

http://rationalwiki.org/wiki/Galileo_gambit

Now, that's a pretty dangerous argument to make. Yes, people need to be cautious of credentialism and experts should be willing to engage with the perspectives and knowledge of non-experts, like scientists who need to consult with engineers when putting together equipment. There is also some truth to the argument that some important historical discoveries were made by non-experts in science. However, that has more to do with the fact that science as a profession didn't really exist until the 19th century century and it was by necessity an amateur-ish pursuit.

Furthermore, while many famous scientists from history were not "experts", that does not mean they were not educated or knowledgeable, it just meant that they did not have as much to go on as scientists do today. They worked just as hard and just as diligently, and that is why they were ultimately vindicated, not because they were rebels showing up the tyranny of the establishment.
 
  • #76
who said they did it to rebel? both examples were of the then educated refusing to accept any deviation from the current sciences as they saw it. yes the church was the culprit so to speak but at the time education was limited to people of the faith and strictly guarded to stay that way.

yes an incompetent in any field is still incompetent. yet doctors which undergo a lengthy education by trade are just as likely to be wrong about a problems cause as a Certified mechanic is even with ten times the amount of technology helping the diagnosis for the doctors. the difference is the doctor has a much better chance that his/her mistake will cost a life.not that a bad mechanic can't end up killing a driver too just less likely to.
specialization does not make a person infallible.
there is always the possibility that what's believed to be true today can be overturned tomorrow.
one of you is saying that scientific advancement truly only ages from the 19th century I beg to differ GREATLY! you'd have to completely ignore the advances in all the forms of building dating back thousands of years and all the native herbology worldwide plus all the other tools humanity developed long before the 19th century to actually believe that. yes you can say understanding the way the shape of a wing creates lift when it passes through the air helps with making planes but I'm pretty sure at the time of the Wright brs. none of those teams trying to be first to fly had that information and they still managed to get airborne.
 
  • #77
All, the sub-thread in the last few posts is getting off topic, and also getting close to being a discussion of philosophy, not physics. Please keep things on topic. Thanks!
 
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  • #78
PeterDonis said:
All, the sub-thread in the last few posts is getting off topic, and also getting close to being a discussion of philosophy, not physics. Please keep things on topic. Thanks!
The argument in last few posts started with my question , it had nothing to do with rebelling with established scientific knowledge or Galileo' gambit or whatever, it was just a simple question , anybody who lacks the patience to respond to questions asked by amateurs should refrain from answering.
 
  • #79
Monsterboy said:
The argument in last few posts started with my question

Has your question been answered? phinds responded to it.
 
  • #80
PeterDonis said:
Has your question been answered? phinds responded to it.
Phinds did say it is not very clear what space is , so there is no point asking more questions on it.
 
  • #81
I read a neat theory on how our universe is like a balloon; however it can save itself from popping by retracting back in. The theory went on how the universe expands from a small scale (big bangs) and contracts from a large scale (end of a universe).

So, in theory, there could have been a whole different universe before the big bang, but was compressed to one single point after it fell in on itself.
 
  • #82
phinds said:
No, it did NOT and that in fact is the point of this thread. You should read threads before you reply.
According to Stephen Hawking'd book, A Brief History of Time, the Universe is expanding and the expansion is accelerating. So if time ran backwards then the Universe would have begun in an infinitely small and infinitely dense point, and it did. The Big Bang theory states that the Universe began in a singularity, you should read the book, it's a good one.
 
  • #83
Quds Akbar said:
According to Stephen Hawking'd book, A Brief History of Time, the Universe is expanding and the expansion is accelerating. So if time ran backwards then the Universe would have begun in an infinitely small and infinitely dense point, and it did. The Big Bang theory states that the Universe began in a singularity, you should read the book, it's a good one.
I have read the book. Your analysis is not correct.

The universe started in a hot dense state. "Singularity" does not mean a point in space.

Also, if your analysis were correct, it would emphatically dictate that there is a center from which the expansion started and that in turn would imply a preferred frame of reference. We know empirically that neither one exists.
 
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  • #84
William Donald said:
I read a neat theory on how our universe is like a balloon; however it can save itself from popping by retracting back in.

Please give a reference.
 
  • #85
William Donald said:
I read a neat theory on how our universe is like a balloon; however it can save itself from popping by retracting back in. The theory went on how the universe expands from a small scale (big bangs) and contracts from a large scale (end of a universe).

So, in theory, there could have been a whole different universe before the big bang, but was compressed to one single point after it fell in on itself.
The bouncing universe theory is disputed or even rejected.
http://www.nature.com/nature/journal/v302/n5908/abs/302505a0.html
 
  • #86
It was a Documentry uploaded on YouTube on space-time, now slices, and time dilation. I watched it many many months ago. I defiantly wouldn't remember how to find it. Sorry
 
  • #87
William Donald said:
It was a Documentry uploaded on YouTube on space-time, now slices, and time dilation.

Even if you could find it, it probably wouldn't be a good reference. Please check out the PF guidelines for acceptable sources on this page:

https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/

Generally, a good reference is either a peer-reviewed scientific paper or a standard textbook. Lots of "documentaries" that appear on TV, even when they have reputable scientists in them, are not good references for discussion here, because they gloss over a lot of details and fine points that, while they may not be interesting to a general lay audience, are critical if you actually want to learn about the underlying physics, as opposed to just saying "wow, neat!" and moving on without delving any further.
 
  • #88
PeterDonis said:
Even if you could find it, it probably wouldn't be a good reference. Please check out the PF guidelines for acceptable sources on this page:

https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/

Generally, a good reference is either a peer-reviewed scientific paper or a standard textbook. Lots of "documentaries" that appear on TV, even when they have reputable scientists in them, are not good references for discussion here, because they gloss over a lot of details and fine points that, while they may not be interesting to a general lay audience, are critical if you actually want to learn about the underlying physics, as opposed to just saying "wow, neat!" and moving on without delving any further.
Sorry for that. I thought since a theory is basically just an idea, it wouldn't matter. I didn't say it was a fact. I just mentioned it, because it relates to the original post. Feel free to delete it or something.
 
  • #89
William Donald said:
Sorry for that. I thought since a theory is basically just an idea, it wouldn't matter. I didn't say it was a fact. I just mentioned it, because it relates to the original post. Feel free to delete it or something.
Did you know, the word "theory" has got a diametrically different meaning in science than it has in everyday usage, which is the source of many a confusion (sometimes intentionally sown; e.g.: "evolution is just a theory!"
headbanger-gif.gif
).
In common usage it means conjecture, speculation. A guess.
In the scientific context it's a hypothesis that passed rigorous testing. It is actually on the same level as "a fact".

On PF the latter meaning is assumed. Especially since speculative ideas are not allowed.
 
  • #90
just a further question about the above. what he describes was a reviewed theory which was disputed or rejected. correct? so wouldn't that be actually discussing a "theory" and not simple speculation are we to never discuss subjects that have been rejected even unknowingly?
 
  • #91
dragoneyes001 said:
just a further question about the above. what he describes was a reviewed theory which was disputed or rejected. correct? so wouldn't that be actually discussing a "theory" and not simple speculation are we to never discuss subjects that have been rejected even unknowingly?
According to the guidelines:
Non-mainstream theories:
Generally, in the forums we do not allow the following:
Attempts to promote or resuscitate theories that have been discredited or superseded (e.g. Lorentz ether theory); this does not exclude discussion of those theories in a purely historical context
https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/
 
  • #92
what i meant by unknowingly is not knowing the theory has been rejected/refuted.
 
  • #93
dragoneyes001 said:
what i meant by unknowingly is not knowing the theory has been rejected/refuted.
What are you arguing about? Nobody got in infractions on this, it was simply pointed out that the "theory" he mentioned does not fit the forum guidelines. If one doesn't know that a theory is inappropriate to discuss here because of the guidelines, does that then make it appropriate just because one didn't know?
 
  • #94
why would you call asking for clarification arguing?

to answer your question: does it make them wrong or in breach of the guide lines if they didn't know the theory was refuted and did not promote it as fact but inquired if it was a valid theory?
 
  • #95
dragoneyes001 said:
why would you call asking for clarification arguing?
Fair enough. OK, to clarity: the fact that one does not know that a theory is inappropriate makes it (marginally) OK to have posted it but one should expect to be called on it by the mods (and possibly by other nitpickers like me) and possibly to have the post deleted.
 
  • #96
i think you posted before i edited the above post please scroll up so there is no confusion.
 
  • #97
dragoneyes001 said:
why would you call asking for clarification arguing?

to answer your question: does it make them wrong or in breach of the guide lines if they didn't know the theory was refuted and did not promote it as fact but inquired if it was a valid theory?
It puts them in breach of the guidelines, exactly as one would be held liable for breaking a law. Ignorance of the law is no excuse. Now, if it's clearly an innocent breach, it's not likely to elicit anything more than having it pointed out that it is inappropriate, which is exactly what happened in this case.

We do occasionally have folks who insist on continuing to promote inappropriate theories but they don't generally last long unless they are willing to see the error of their ways.
 
  • #98
thank you that's all i was asking.
 
  • #99
dragoneyes001 said:
thank you that's all i was asking.
Yeah, sorry if I got a bit snippy. Greg pays me to do that because by setting such a bad example, I make all the mods look good.:p
 
  • #100
now to get back to the subject at hand is there a layman's way of explaining the universe was in a" hot dense state"
 

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