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KurtLudwig
Does space expand only at the outer edges of the universe? What is the mechanism that creates more space particles? Is the huge volume of outer space pulling our universe apart? Please enlighten or comment. Kurt Ludwig
You should Google "metric expansion".KurtLudwig said:Does space expand only at the outer edges of the universe? What is the mechanism that creates more space particles? Is the huge volume of outer space pulling our universe apart? Please enlighten or comment. Kurt Ludwig
To add a little to jbriggs444's response, the expansion of space means that the distances between objects in the universe are getting larger. Galaxies today are further from one another than they were billions of years ago.KurtLudwig said:Does space expand only at the outer edges of the universe? What is the mechanism that creates more space particles? Is the huge volume of outer space pulling our universe apart? Please enlighten or comment. Kurt Ludwig
Galaxies are getting further from one another due to metric expansion of space, due to dark energy, or due to both (or both are the same thing?)kimbyd said:To add a little to jbriggs444's response, the expansion of space means that the distances between objects in the universe are getting larger. Galaxies today are further from one another than they were billions of years ago.
rootone said:The whole Universe is the entirety of space and time, there is nothing outside which it expands in to.
Our observable part of the Universe is expanding.
Other parts of the whole Universe not observable to us may also be expanding, I think the jury is still out on that one.
windy miller said:There seems to be something problematic about this answer. you have defined "the universe" as the entirety of space and time. So of course you get the answer the the universe isn't expanding into some other space/time. But this just seems like a tautology, only telling us about how words have been defined and not about any objective reality. One could define the universe in a different way and indeed cosmologists that speak of a multiverse must define it in a different terms if the multiverse is to make sense. of course there are different types of multiverses that have been considered, for example the multiverse of eternal inflation or the suggestions that our universe is embedded in higher dimensional membrane. Who knows maybe our space time is embedded in some other object that we have not even thought of yet. i think its fine to say we don't require that the universe be expanding into anything else, but that's not the same as saying with confidence that it isn't.
Metric expansion. Dark energy impacts how the expansion changes over time, but isn't a root cause of the expansion in any reasonable sense of the word.Delta² said:Galaxies are getting further from one another due to metric expansion of space, due to dark energy, or due to both (or both are the same thing?)
windy miller said:you have defined "the universe" as the entirety of space and time
windy miller said:i think its fine to say we don't require that the universe be expanding into anything else, but that's not the same as saying with confidence that it isn't.
What you're proposing is much more than the multiverse or M theory.windy miller said:Im sorry but I don't agree with you. The evidential demand is on the person making the claim not on the person who refuses to accept it. I am not claiming there is something beyond our familiar space-time. The multiverse or M theory may or may not be true,. But if you claim there isn't then then you need to show the evidence Saying the models doesn't require it isn't the same as saying as was a said "there is nothing outside which it expands in to.". That is a positive claim that requires evidence to support it. There is no evidence for life on Europa but that doesn't make the statement " there is no life on Eurpoa" a justifiable one.
windy miller said:if you claim there isn't then then you need to show the evidence
windy miller said:There is no evidence for life on Europa but that doesn't make the statement " there is no life on Eurpoa" a justifiable one.
Yes Peter i read your post. Did you read mine? Science may not make statements of certainty , but individual scientists and forum members do and they are not always justified in making them. I was responding to this comment ""there is nothing outside which it expands in to.". Where is there any hint of doubt in this statement? It could have been phrased as we have nor reason to think there is anything its expanding input, or our current modes don't require it to expand into , or we have no evidence of something its expanding into, something like that I would have no objections to these comments . But that isn't what was said. Please read other peoples posts before you accuse them of not reading yours,PeterDonis said:I didn't claim "there isn't". I said there is no evidence for it. Which is precisely what you are asking for: evidence. So I already have given you what you say you want. Did you even read my previous posts?
Not if you intend the claim as a statement of certainty. But science does not make statements of certainty. It only makes statements about what our best current evidence says. Having no evidence for life on Europa does make the statement "we have no evidence for life on Europa, therefore our best current model does not include it" justifiable. And that's precisely the kind of statement I made about our best current models of the universe. So again, did you even read my previous posts?
windy miller said:I was responding to this comment ""there is nothing outside which it expands in to.".
windy miller said:Please read other peoples posts before you accuse them of not reading yours,
windy miller said:As far as I can see lots of cosmologists says things like "the universe isn't expanding into anything" without the slightest caveat that they don't really know this to be the case.
windy miller said:Lots of cosmologists say the universe began with a big bang
PeterDonis said:I won't try to justify what cosmologists say in pop science articles, videos, etc., because I think scientists in general are too careless in such venues. But in textbooks or peer-reviewed papers, cosmologists are (and should be) more careful. Statements in such sources are always made in the context of some model or set of models.
In textbooks and peer-reviewed papers, the term "big bang" has a particular technical meaning, and statements about it are made accordingly. We do know, based on many different lines of evidence, that the earliest state of the universe of which we have good evidence, which is what the term "big bang" properly refers to in textbooks and peer-reviewed papers, was a very hot, very dense, rapidly expanding state. That is what a statement using the term "big bang" refers to, properly interpreted, and statements about it are not speculation or hypothesis, they are based on evidence.
If you can find textbooks or peer-reviewed papers that use the term "big bang" differently, and that go beyond what is justified by our best current models and evidence, feel free to give specific references. But I strongly suspect that your statements are based on pop science sources, not textbooks or peer-reviewed papers. The fix for that problem is simple: don't try to learn actual science from pop science sources. That's why PF has rules about acceptable sources.
windy miller said:these two institutions web sites I don't think should be classified as "pop science". Perhaps you disagree
windy miller said:The very first article i found when i put in a search for peer reviewed articles on the age of the universe was this one
windy miller said:Science is communicated by scientists and i think it not an uncommon feature for cosmologists in general to overstep the mark in what we can be really confident of when we are talking about such grand statement as the entirely of all physical existence.
KurtLudwig said:The distance between galaxies is increasing
KurtLudwig said:no space is added or created
KurtLudwig said:Where are they all headed to? Space must be somehow expanding!
KurtLudwig said:Is space a field?
KurtLudwig said:I have been attempting to read textbooks on quantum mechanics and the standard model
KurtLudwig said:After having read too many "pop science" books I tend to believe the following, without any proof at this time: In physics, at exceedingly small dimensions everything turns digital, including space.
KurtLudwig said:Is anyone conducting an experiment to find out if space is "granular"?
KurtLudwig said:Time is just a convenience to be used in calculus. Time is the count of the number of cycles, such as in a mechanical pendulum clock or a vibrating crystal in a digital watch.
It can appear that way if quantum mechanics is true. which seems seems very likely.KurtLudwig said:find out if space is "granular"?
Yes, as long as the galaxies are not in local clusters, which are bound systems and do not expandKurtLudwig said:1. The distance between galaxies is increasing
Corrrect, yet no space is added or created
They are not "headed" anywhere, except apart. Where are they all headed to?
No, space is just geometry, not a thing that can be streched. Re-read "metric expansion"Space must be somehow expanding!
Bounds systems such as galactic clusters, galaxies, solar systems, planets, you, atoms, etc do not expand.Yet our Earth and solar system are not getting any bigger or further apart, at least not to my knowledge. Please explain.
No, space is just geometry2. Is space a field?
There are particles IN it, along w/ planets, stars, etc.If space is a field then there must be "particles" associated with it.
There is no reason to believe this. Please avoid personal speculation. It MAY in fact be true but there is not currently any evidence for it.3. After having read too many "pop science" books I tend to believe the following, without any proof at this time: In physics, at exceedingly small dimensions everything turns digital, including space
It is very much an open area of discussion in physics. I don't know about experiments; I don't think we can measure things small enough. If things ARE granular, it is believe that the granularity will be on the order of Planck measurements or smaller and right now, the Planck Length is TWENTY ORDERS OF MAGNITUDE below our ability to measure things.. Is anyone conducting an experiment to find out if space is "granular"?
That's a reasonable way of looking at it.4. Time is just a convenience to be used in calculus. Time is the count of the number of cycles, such as in a mechanical pendulum clock or a vibrating crystal in a digital watch.
Do you have any refereed citations that connect quantum mechanics to the necessity that space and time are granular? I do not believe any such exists.rootone said:It can appear that way if quantum mechanics is true.
phinds said:... Bounds systems such as galactic clusters, galaxies, solar systems, planets, you, atoms, etc do not expand...
DanMP said:Why exactly? And how is established the upper "limit" (galactic clusters?)?
PeroK said:... on the scale of the solar system, the expansion of space has a tiny, negligible effect...
I was, I suppose, unclear when I said there was no expansion. What I should have said was that there is no ONGOING expansion. Whatever effect DE has on bound systems is already built into their orbits/conditions. Also, DE on the scale of atoms, for example, is REALLY negligible. Possibly a rounding error somewhere around the 20th decimal place.DanMP said:So phinds was wrong/inaccurate, as I thought. Thank you.
DanMP said:This expansion of the Universe is derived mainly from the redshift of all distant galaxies, right? What reasons do we have (other than the absence of a good, overall acceptable, model) to reject the ideea that this redshift (or at least a part of it) is caused by / related to the distance that light has to "travel"?
PeroK said:Why would the travel time of light induce a redshift?
DanMP said:I can't answer this question now/here, that's why I specified "other than the absence of a good, overall acceptable, model" ... so please focus on other reasons to reject the idea.
PeroK said:That's as good a reason as I can think of!
PeroK said:Actually, once you understand the concept of an expanding universe, it's not so problematic as popular science would have you believe. ...
DanMP said:Maybe, but to explain dark energy is problematic, as far as I understand ...