"Really, the fundamental, ultimate mystery -- the only thing you need to know to understand the deepest metaphysical secrets -- is this: that for every outside there is an inside and for every inside there is an outside, and although they are different, they go together." -Alan Watts
We've talked, recently, about the scale of the Universe, and trust me, it's huge.
Filled with hundreds of billions of giant, Milky Way-sized galaxies,
each of which contains nearly a trillion stars,
the whole thing is really, really big. And, after nearly 14 billion years of expansion since the big bang, the part of the Universe we can see -- the observable Universe -- is 93 billion light years across!
But there's more Universe outside of what we see. Based on our best theories of how our Universe got here -- the theory of inflation -- we might be inclined to ask just how big the entire thing is!
After all, inflation takes some initial region of space, and regardless of its initial shape, size, or conditions, stretches it, and causes it to expand at an exponential rate!
This takes any initial Universe and makes it huge! Not just billions of times larger than it was initially, but googols upon googols of times larger! It stretches it flat, it makes it uniform, and even sows the seeds of what will someday grow into the stars and galaxies that fill our Universe today!
Well, let's think about what inflation does. This super-rapid, exponential expansion causes the spacetime of the Universe to stretch flat, but also to expand to a much larger volume than it previously occupied.
That's what inflation is. But how does inflation happen? To the best of our (admittedly limited, and highly theoretical) knowledge, the Universe inflates when it's full of what we call vacuum energy.
But being full of vacuum energy is unstable, and the when the Universe slips down into a more stable state (like sliding down this hill in the picture above), that energy gets transformed into matter, antimatter and radiation, and gives us the hot big bang, and our modern Universe.
But there's something else we need to think about here. The Universe, at a fundamental level, does all the weird things that quantum mechanics lets it do. And one of the most bizarre things about quantum mechanics is that if you take something like, say, an electron, and you put it somewhere (like in an orbit, below), when you look again at a later time, it isn't going to be in the same place!
In physics language, we say that the quantum state spreads out over time! Now, here's where it gets really bizarre. We're going to put all three of these things together.
- The Universe is inflating, or expanding exponentially. This means we're making "new space" at an ever-increasing rate. After one unit of time (t), we have one unit of space (V). After 2t, we have 4V. After 3t, we have 16V, and after 4t, we have 256V. In other words, we are making lots and lots of new space very quickly, at an ever increasing rate.
- The average vacuum energy is decreasing as we "slide down the hill."
- But, the actual vacuum energy in any volume of space, V, has to deal with the fact that the wave-packet is spreading out!
So we've got a race happening: the average energy is trying to slide down the hill, but in some of these areas of space, the spreading of this wave-packet pushes us up the hill instead of down it!
When we put all three of these things together, what we get is the concept known as eternal inflation. The big idea is that what we call "our Universe" is just one place -- which we can only see a part of -- where we've successfully slid down the hill. But the vast majority of the "true" Universe, outside of our little pocket, is still inflating, and still expanding exponentially!
Based on what we currently think about inflation, this means that the Universe is at least 10^(1030) times the size of our observable Universe! And good luck living long enough to even write that number down. Thanks to Rob Knop for making me think about this, and isn't that a mind-blowing thing to think about? All that we know, see, and observe is just one tiny region that slid down that hill fast enough to end inflation, but most of it just keeps on inflating forever and ever. Aren't we the lucky ones?!
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With inflation and expansion occuring in the Universe, is there a way to represent how much inflation occurs in a given human lifetime?
The Universe is 14 billion years old and has expanded to 93 billion light years, and continues to expand due to inflation of the Universe.
Could you create a statistical chart, even though the values would change for the size of the expansion, say for example:
Age Universe Current Size
0 93 billion light years
1 95 billion light years
2 99 billion light years
3 107 billion light years
And how would that mathematically be expressed, to calculate for the expansion rate that is occuring on the outer edges of Universe?
The reason why these questions are asked, is to develop a conceptual lens that any reader could grasp the size of the expansion within a human lifetime. Even with unknown variables. Granted most individuals can grasp binary numbering system: 0, 1, 2, 4, 8, 16, 32.., would the expansion be simular?
Does each island universe have its own physical laws? What happens if one intersects another? Who's laws win out?
Inflation is a just so story.
My head hurts now.
You state in the final paragraph that, "All that we know, see, and observe is just one tiny region that slid down that hill fast enough to end inflation...." How does this square with the observations that, outside our closest neighboring galaxies, everything we can see is moving away from us at an accelerating rate?
Just saw the BBC Horizon documentary What Happened Before the Big Bang, it has a very nice discussion of this and competing ideas, highly recommended.
However, a plethora of questions sprang to my mind:
-How does eternal inflation deal with the ultimate beginning? Is it eternal in a sense that it has inflated forever in the past as well?
-Doesn't that cause problems with issues of scale? I mean if you roll back the film, shouldn't you hit the Planck scale quite soon?
-Or is the starting point already infinitely large is space, and thus whatever expansion happens, it just becomes larger and larger but still infinite?
-Has anybody really thought about these things (not just related to eternal inflation) in terms of cardinalities?
Thanks for the great blog, been lurking around for quite some time now. I chose to study nanoscience instead of cosmology, but I've kept an avid interest in the current issues and you have been very helpful :)
How does this square with the observations that, outside our closest neighboring galaxies, everything we can see is moving away from us at an accelerating rate?
Expansion is still occurring in the observable universe but this is of orders of magnitude different than the primordial inflation in the first moments of the Big Bang.
If only we could tap into the energy in that infinitely expanding space. We'd be gods!
"Just so story"? Not really:
Unless you consider any theory with a subset of testable predictions that haven't been tested yet a "just so story".
I consider any far fetched narrative with no experimental support beyond what it was invented to explain a just so story.
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to Al @10, maybe you could look up "Evidence for cosmic inflation" on google. it's not hard to do, just the effort of typing and hitting the enter key.
'Just-so story' (from Rudyard Kipling, originally) is a dog-whistle phrase which signals opposition to the evolutionary view of life. It is possible that its use by a poster on this thread indicates that the writer has a religious objection to a variety of scientific notions, & has lumped 'the multiverse' in with 'Darwinism' as just another materialist lie, meant to subvert the central position of humanity in a universe run by Yahweh. Or I could be totally wrong.
Or, we'd end up becoming chronically bored dilletantes.
Is this continual inflation based on a purely 3D universe?
Or are there hypotheses/theories that add more dimensions?
@12 I did google it and I fail to see any evidence, can you be more specific? What experimental evidence is there for inflation? And as I said relative isotropy and homogeneity of space do not count as they were the reason inflation was invented in the first place.
All there is are some CMB measurements which support some models of inflation and rule out others. Well that's hardly supporting evidence. It would be if we had specific predictions before CMB were measured and if disagreement could rule out inflation but that is not the case.
Personally I much prefer unexplained observations then dubious speculations which purport to explain them. Extraordinary claims require extraordinary evidence, when it comes to inflation we don't even have ordinary evidence.
And no, it has nothing to do with religion.
The power spectrum of anisotropies in the cosmic microwave background are regarded as key experimental evidence for inflation: http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation#Prim…
If the expanding space had a start point, then I don't think the future expansion is 'infinite', or 'eternal'. At any point along the expansion, you can look back and count a finite number. You cannot have one-way infinity. The same way you cannot 'reach' infinity via 1, 2, 3, ... Unless there is an infinite past with no start-point (which is beyond my comprehension), then we are talking about very big numbers, but not infinity. I think.
I have always found it interesting how we humans live in our bounded worlds and how the universe around us could potentially be unbounded. I guess it's because we see the bounds of things in our everyday lives. The pencil has a beginning and an end. The road, the planet, the sphere of the sun...
It boggles my mind to think of the possibility that we live in an infinite universe that stretches for ever in all directions. Perhaps it's more comfortable to think of a finite universe but the question of what exists outside the bounds can be more frightening. Is it possible that 'nothingness' is a 'thing' just like 'this'?
When I want to feel better centered when my life starts to runaway with me I think of the fact that I could be so less significant than a quark in the flea on the back of a dog standing on the planet Earth orbiting the sun. For some that frightens them but for me it encourages me to step out and try new things and really puts things in perspective. After all, what do I have to lose?
Still though, I find the idea of cosmology and astronomy strangely compelling, almost an obsession...
Huh? These sentences contradict each other. As you yourself said in the first sentence, the CMB measurements support some models of inflation and rule out others. I. e., we had "specific predictions before CMB were measured", although you dispute that in your last sentence! And obviously, if the CMB measurements can rule out some models, they also could have ruled out all models - but they didn't! So, why isn't this evidence for inflation?
Al, Ptolemy's model staid around for millennia, people kept adding little circles and what nots to make the model fit the observation, until Kepler came up with the "if we use ellipses that heliocentric model becomes real easy", and down went Ptolemy. It's only been 40 years on the Standard model, and already we have inflation, dark matter and dark energy. We're just waiting for Kepler jr. to have the epiphany to simplify it all back down.
@Jerry m. Weike:
That's not correct: the observable part of the universe has expanded to about 93 billion light years; the whole universe is much larger (if the hypothesis of external inflation is true), as Ethan explained above. And the expansion of the observable part of the universe has nothing to do with inflation.
Yes, it's possible to create such a chart, and you can even do it yourself! Right now, the expansion of the universe occurs almost exponentially (the real relationsship is more complicated, but an exponential gives an approximation which is already quite good): The size of the universe increases by about 7% per billion years. (but the size of the observable universe is a different matter - for that, the calculation is more complicated)
"Unless you consider any theory with a subset of testable predictions that haven't been tested yet a "just so story"."
If they haven't been tested yet, I'd have to agree with Al; untill proven otherwise.
@Craig wikipedia? Come on!
@8 @14 It also makes for a great spaceship engine (cf ND-001 Nadesico). Still no FTL, though.
I love that first graphic. I'll have to think about the rest.
effing far out
Any not-excessively-unreadable-to-those-in-science-who-aren't-physicists sources on this? Most of the papers on inflation I can find appear to be littered with Greek letters and equations that I have yet to take enough math to comprehend.
All there is are some CMB measurements which support some models of inflation and rule out others.
Never forget that "No X" (or "X=0") also counts as a "Model of X", as a general principle. And in order to differentiate between different models of X, you need some kind of positive measurement, and that in itself is evidence against "No X".
Al's definition of "just so story" in #10 is wrong. A "just so story" is a circular narrative that is unfalsifiable in principle. If it is even theoretically falsifiable, it is a legitimate scientific hypothesis, regardless of how easily it would be to falsify practically (or whether or not it has already been falsified.)
Is "the Universe" = "Our universe" or "the Multiverse"?
"the Universe is at least 10^(1030) times the size of our observable Universe!" Is this great unobservability more hypothetically necessary than angels?
When is extrapolations towards infinity an exact science?
Does point 1 + 2 + 3 = Multiverse suggests a new "science" called Multi-cosmology??: the study of physical hypothesis concerning all things unobservable (e.g. the eternally inflating false vacuum, Dirac's infinite sea of negative energy particles, island universes, baby universes, and of course the super-hypothetical-particle the "inflaton").
According to Multi-cosmologists:
---Are some island universes totally antimatter?
---How many spatial and temporal dimensions compose the Multiverse?
---Is the Multiverse part of a MULTI-(Multiverse) which is part of a MULTI-(MULTI-(multiverse) and so on and so forth?
---Is our observable universe inside the Multiverse of outside it? According to Alan Watts, of course.
Universe is at least 10^(10^30) times the size of our observable Universe!
This is mind-numbing...fascinating really.
Not so. Steve Gould used the phrase, borrowed from Kipling, as a stand in for any empirically unverified adaptationist explanation for some observed feature of an organism. Employing this phrase implies no general opposition to evolution but only to the uncritical construction of explanations for why some assumed adaptation must've been selected for, rather. The adaptationist explanation may well be correct but it must stand as a 'just-so story' until some objective evidence either verifies or refutes it.
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If only we could tap into the energy in that infinitely expanding space. We'd be gods!
Unf., it's in a high entropy state. Sort of like trying to light a cigarette with an ice cube.
And now for inflation explained with less FOX news style ("super fast") right here:
So this is what happens when we continue to blow up increasingly small vectors of space? For some reason it reminds me of chewing on an oyster, it just keeps getting bigger. I really like the photos, etc., particularly the grainy pattern looking cream of wheat stuff which appears between the deep galaxies. Food analogies? Perhaps it is that the vacuum I feel is ultimately in the black hole of my stomach at this point.
Yes, I'll take the time to vote as per the previous posting (vote early and often).
So, 1500 years are "millenia"? Can't you get at least a fact right which is so easy?
Another easy fact which you get wrong: as far as I know, Ptolemy's model was not in any way changed or added on in those 1500 years.
And here you ignore the slight difference that inflation, dark matter and dark energy all make testable predictions (and that some of which already had been tested!), whereas Ptolemy's epicycles were totally ad hoc and did in most cases not lead to new predictions (and in the few places where they did, the observations contradicting these predictions essentially were simply ignored).
We're just waiting for Kepler jr. to have the epiphany to simplify it all back down.
I will be happy in my ignorance. Time is a ray and our measurement of its segments is based on our own subjective cycles; it has a starting point but no end. Space is infinitesimal. What matter we can see a/o measure kicked off at the big bang but is not the whole of it, i.e., we are just in one corner of the infinity of space - perhaps spreading out to interact with other matter we cannot yet see, which may have begun with its own big bang, perhaps doomed by gravity to collapse again awaiting the next big bang. The idea that the universe is bounded seems fantasy but I am stuck in my own definition of what the universe is. Until someone can find a way to enlighten me, as much trust as I put in the ability of scientists to work out these things, I'll have to suffice myself with my own ignorance as stated above.
Does this theory of permanent inflation suggest that the actual distance between objects in space increases at this same rate? More specifically does the sun-earth, earth-mars etc. distance increse at the same rate? If so, is this taken into account when computing the travel time necessary for the planned Mars mission for example?
lgrooney, please look up the word infinitesimal. I don't think you want to say that the universe is very, very small.
Yes, Helen, infinite. Thanks for the catch.
OK, maybe I'm just sleepy, or maybe just exposing my innocence here, but I'm having some difficulty with the concept of the universe being just 14 billion years old but 93 billion light years in diameter.
If we're starting from a Big Bang, and stuff moved outward at about the speed of light for 14 billion years, wouldn't that give us a diameter of 28 billion light years?
Is there something basic I'm missing or do I need a degree in astrophysics for this?
Ermm...I'm not a physisict, rather an interested reasonably well-read layperson. I'm trying to understand this race between the vacuum energy slide down vs the wave packet pushing up. Vacuum energy must have been pretty big, compared to electron's, because that's what decomposed into the primary particle bits like bosons and--what's the other, muons?--that later became protons and electrons. So how can the electron's wave packet spreading (and thereby getting weaker--wider but lower) win against the vacuum energy. Inflation drives down vacuum energy density (same energy spread over greater volume), but presumably the same is happening with the electron wave packet?
I don't know the orders of magnitudes involved, but this suggests to me that while the electron wave packet might win sometimes, it would be really quite rare. So I'm wondering why it the non-inflationary miniverse that would be rare, rather than the norm?
As far as you know is not very far apparently. It most certainly was fiddled with and adjusted in all sorts of ways many times over that period (there are lots and lots of parameters in the model that could be, and were adjusted, quite apart from adding more epicycles).
Ptolemy's model most certainly did make predictions, just the same sort of predictions that Kepler's model made, i.e., it predicted where each planet would be in the sky at specific future dates, and the model survived because, most of the time, there predictions proved correct within the limits of observational accuracy available in the ancient and medieval worlds. On the occasions when the predictions and the observable positions had drifted noticeably out of sync, the model was adjusted (as noted above) to correct it. It was falsified only when much more accurate observational data became available (thanks to Tycho Brahe's compulsiveness, and the fact that he had massive financial support from the astrology mad king of Denmark), and Kepler to realized that no system based on circular orbits (even a heliocentric one, like Copernicus', and no matter how many epicycles, eccentric points and equants you used, or however you adjusted the parameters) could be made to fit Tycho's data.
Furthermore, Ptolemy's epicycles were not ad hoc in any relevant sense of that expression, they were built into his theory, which was the first to provide a theoretical basis for making reasonably accurate astronomical predictions, from the start. "Ad hoc" does not really have any meaning as applied to the initial formation of a theory. "Ad hoc" refers to additions and adjustments made to a theory after it has been shown not to fit the facts in its original form. This happens to nearly all theories to some degree, and even quite major ad hoc elaborations sometimes turn out to be right (Pauli's postulation of the neutrino is a good example, also, the prediction of the existence of Neptune from observed deviations of Uranus from its predicted orbit), but too many big ad hoc elaborations, that make a theory a lot messier than it was before, certainly ought to worry people, and inflation, dark matter and dark energy are big, messy, ad hoc elaborations to the basic Big Bang model. It has all the marks of a typical degenerating research program (in Lakatos' sense). That does not prove it is wrong, or that inflation, dark matter and dark energy are not real, and I quite understand that the model, with these ad hoc adjustments, is by far the best explanation of the known facts that anyone has come up with so far, but from a perspective informed by the history of science, things do not look good.
I agree with Mu. I think we are (most probably) waiting on the next Kepler.
(That does not mean giving up on the current model and waiting for inspiration to strike someone, however. Kepler only arrived at his ellipse model because he spent years fiddling around with epicycles, eccentric points and equants, trying to get them to fit Tycho's data, until he understood the issues so well that his mind was prepared to see why ellipses were better.)
To elaborate my final (parenthetical) point, Ethan (and other who work actively at trying to make the current models work better) may have an outside chance of one day becoming cosmology's new Kepler, but I, and other interested outside observers of the field, certainly don't.
"... the question whether the universe is spatially finite or not seems to me decidedly a pregnant question in the sense of practical geometry. I do not even consider it impossible that this question will be answered before long by astronomy. ... Experience alone can finally decide which of the two possibilities is realised in nature."
That was Albert Einstein in Sidelights on Relativity, an address delivered in 1920.
@Nigel: First, I don't think that pointing out that 1500 years is not "millenia" is "trivial nitpicking". Second, I'd like to see some evidence for your claim that the parameters of Ptolemy's model were "fiddled with" over time.
But it also made predictions about e. g. the sizes of objects in the sky - and these didn't match the observations. For example, in order to predict the position of the moon in the sky, you needed to use a different set of parameters than in order to predict its size in the sky.
That was my point, of which you are apparently unaware... (source: biography of Copernicus in "Spektrum der Wissenschaft")
Additionally, you ignore the point that the model did not make any new predictions. The epicycles were introduced in order to describe the motions (and the sizes) of the planets on the sky - and that was all the model could do: predict the motions (and the sizes) of the planets on the sky. The epicycles didn't lead to any predictions of anything additional to the things which they were introduced for. That was my point - which you apparently missed...
That's simply wrong mathematically. By using enough epicycles etc., one can describe any curve one likes to any desired accuracy. Kepler only realized that a description using ellipses was much simpler than one using epicycles etc., not that using them was not possible!
They were introduced, as the famous quote says, in order to "save the phenomena". If that's not "ad hoc", I don't know what is!
Well, then you have a different understanding of "ad hoc" than me.
For inflation, I tend to agree - but for dark matter and dark energy, I don't. The latter two are absolutely natural extensions of the theory; they are in no way "big", "messy" or "ad hoc". Dark matter is simply matter which doesn't interact electromagnetically - it's perfectly natural to assume that such stuff exists (we even know already examples for that: neutrinos; and essentially every extension of the Standard Model of Particle Physics predicts the existence of more such particles!). And Dark Energy can also be interpreted simply as the vacuum energy; that such a vacuum energy should exist has also been predicted by Quantum Field Theory for decades; the "only" problem is calculating its magnitude.
@adam: Only things which are not gravitationally bound to each other participate in the cosmic expansion. I.e. the distance between Earth and Mars etc. stays the same, the size of the Earth stays the same, the size of the Milky Way stays the same etc. Cosmic expansion is only visible on really huge objects/distances, on the order of tens of millions of light years.
@Michael J. McFadden: You are really missing something quite basic - namely your assumption that
is wrong. First, it makes little sense to speak of "outward" here: the universe does not expand away from a single point into already existing space; rather, space itself expands, and nothing is "outside" of it. Second, this expansion does not happen at the speed of light: the "radius" of the universe (if it even makes sense to speak of that) can increase at any arbitrary speed, it is not limited by the speed of light (and no, that does not contradict Special Relativity).
@Nigel: Oh, and you forgot to consider that the idea of Dark Matter didn't even come from cosmology - there were two other observations which led to its postulation (rotation curves of galaxies and motions of galaxies in galaxy clusters); so this idea was already around and simply incorporated into cosmology, not "ad hoc" introduced to it.
Bjoern, thanks for pointing out that 1500 years is not milenia, I will be more precise in my choice of units next time.
And you utterly missed the point on the fact that what we're doing with the standard model is exactly the same what astronomers did for thousands of years (taking the fact that earth centered models are older than Ptolemy); fitting increasingly better observations in the basic framework of the model without daring to look at the basis of the model itself.
I have no idea if the world is really as complex as the standard model suggests, or if we're missing a vital point (my Kepler reference). But in any other scientific branch, if you're insisting to use the same model for 40 years, and by now the total energy content is 20 times as much as it was when you introduced that model, people are going to doubt the fundamentals of the model. Especially if you're adding lots of new energy to the model without explaining why this error didn't show in the original model.
Then again, maybe it's really semantics. Maybe to the few who can really follow the mathematics it's clear that the introduction of dark matter completely invalidated the original big bang model, and just the failure to make that clear to the general public leads to the hodgepodge of a description we see today.
Err, no - as I already pointed out (at least two times now already), using epicycles etc. to describe the motions etc. of the planets was done only in order to describe the motions etc. of the planets, it did not lead to any new predictions. In contrast, adding dark matter and dark energy to the Big Bang Theory lead to several new predictions, some of which already have been confirmed.
(BTW: by "standard model", you here probably mean the standard model of cosmology, not the standard model of particle physics - right?)
And you also ignore the point that the idea of dark matter did not even come from cosmology, but that there was already evidence for it from other parts of astronomy.
And you also ignore the point that from the standpoint of particle physics and quantum field theory, one should even expect the existence of dark matter and dark energy.
Err, you mean like Newtonian mechanics, which has been around for 300 years now and is still used for almost all mechanical applications? Or like Maxwell's equations, which have been around for almost 150 years now, and are still used for almost all electrodynamical applications? etc. You get the point?
Pardon? What are you talking about? Do you really want to claim that when the Big Bang theory was first introduced, people thought that the density is only 5% of the critical density, or what???
Err, because the measurements only recently (in the last 10-15 years) became precise enough that one could detect that?!? Did you really miss all the hype in 1998 when Perlmutter et al. were first able to detect the presence of cosmic acceleration?!?
That's simply hogwash. The Big Bang theory always incorporated matter (dark or not is essentially unimportant to the relevant equations!); the only thing which has been uncertain for years (and which has been pinned down only in the last decade) was the density (respectively amount) of that matter.
@Al: the post and many of the comments mention what seems like a giant piece of evidence, the fact that the size of the observed universe in light years far exceeds the time elapsed since 'the Big Bang'. As I understand it inflation makes sense of this apparently absurd result, and we didn't know it when inflationary theory began. (People who actually know the topic, feel free to correct me here.)
@hf: No, the fact that the observable universe is larger than the time elapsed since the Big Bang multiplied by light speed is not due to inflation. It's due to normal expansion of the universe, and there is nothing "absurd" about that.
Mu & Nigel, Nice comments keep up your critical skepticism.
Bjoern, As always, informed rebuttals. I assume "normal expansion of the universe" means "dark energy" means "Einstein's cosmological constant".
If our universe is not flat Euclidean as most cosmologists assume; then one "creates" pseudo-forces and hence their pseudo-accelerations (e.g. dark energy).
Interpreting the Hubble redshift phenomenon as due to an "actual velocity" leads to the big bang idea of an expanding universe due to an "ad hoc" inflationary force.
Hubble cautioned (Einstein agreed); the Hubble redshift phenomenon always should be attributed to an "apparent velocity"; thus the "apparent expansion" of our visible universe, the "apparent big bang" and "apparent inflation".
But modern cosmologist are so beyond calling any unknown an "apparent"; they assert a specific hypothetical (e.g. "inflationary force", "dark energy", "dark matter").
LHC will support or rebut (i.e. null experiment) hypotheses of these "apparent" stuff.
I expect null experiments on dark matter, dark energy, and inflation; meaning no required new particles will be found (e.g. thus we need reconsider the detailed general relativistic calculations that obviate need "for dark matter halos in the total galactic composition" http://xxx.lanl.gov/PS_cache/astro-ph/pdf/0507/0507619v1.pdf
@OKThen: Thomas, is that you?
No, these are not equivalent. "Normal expansion" could mean "expansion with dark energy etc.", but it could also mean "expansion with only usual matter and energy". That doesn't change the argument.
Err, that's not simply "assumed", that's a conclusion from the data!
How does that follow?
What on Earth do you mean with "actual velocity" and with "inflationary force"? (both aren't terms which cosmologists usually use, although you imply otherwise) And how does the second follow from the first?
And what's that supposed to mean?
As already pointed out, as far as I know, no cosmologists talks about an "inflationary force". And I don't understand your problems with the other two terms: dark energy acts like an energy, but can't be detected directly; hence it's sensible to call it "dark energy". Same for dark matter.
That we already have several pieces of evidence pointing to the existence of all these things doesn't bother you...?
Even if that paper were right (and according to Ethan, it isn't - although he unfortunately still has not explained in detail why), there are nevertheless still several other pieces of evidence for the existence of dark matter.
So "normal expansion" is not yet defined. OK.
Euclidean space is not an expanding inflationary space; so what means you "that's a conclusion from the data!"
Psuedo forces arise from a non-inertial reference. If universe is not spatially Euclidean; then cosmic measurements introduce non-inertial components, i.e. pseudo forces.
Google ("inflationary force") to see meaning in Wiki.
Google ("actual velocity" Hubble) to see Steven Weinberg's meaning.
Google ("apparent velocity" Hubble) to see Hubble's meaning.
Inconclusive evidence points to a mystery to be solved; yes maybe a dark bandit stole the energy and matter.
Energy and matter are apparently missing; either "dark matter" and "dark energy" will be found (e.g. LHC), or something is wrong with our current physics assumptions.
Ethan's view is the current accepted view. No argument.
"Dark matter", "dark energy", and "inflaton" (Google) are not yet found; their status is like Michelson Morley's aether wind, i.e. theoretically supported (1887) but not yet found.
I simply wanted to point out that this isn't a unique feature of inflation, but also happens for other, more "mundane" types of expansion, like e. g. the expansion going on right now.
Sorry, I don't know what exactly this is supposed to mean. Additionally, could you please stop writing "inflationary" if you don't mean inflation, but only ordinary expansion?
Well, cosmologists try to fit the data to models, and one parameter of the models is the total density - or rather the ratio of the total to the so-called critical density. And the measurements show that this parameter is very close to the value for a flat space - indistinguishable from that value. See e. g. here for some graphs showing that:
Well, that's clear (if you add the word "frame").
Sorry, I don't see how that should follow.
We were talking about cosmologists using that term, not about Wikipedia. (especially not a Wikipedia article which says right at the top "This article needs attention from an expert on the subject."!)
Google does not seem to give any relevant pages for me here. Why don't you simply provide a link?
This yields e.g. the following statement by Hubble:
I don't see any problem with that statement. In cosmology, redshift is usually not considered as being due to velocity (Doppler shift), but due to the expansion of the universe directly: as the universe expands, wavelengths get stretched. (and yes, I noticed that according to that webpage, Hubble thought that the universe was stationary - unfortunately, the webpage was unable to explain what Hubble thought about the real cause of the redshift then...)
I'm at a loss to understand what this is supposed to mean. What "inconclusive evidence" are you talking about?
I'm not sure what exactly you mean with "theoretically supported" - but do you really want to deny that there is observational evidence for the existence of dark matter and dakr energy?
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"do you really want to deny that there is observational evidence for the existence of dark matter and dark energy?"
"More is unknown than is known... The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data."
Evidence for dark energy is sufficient to suggest a mystery; but not enough to assert that a particular hypothesis is correct. ditto: dark matter and inflation.
I did not know that the term "inflationary force" is cosmologically incorrect; I assume "inflaton particle" and "inflationary field" are still OK.
Quite a bit of discussion on this one... Glad to see that this blog has a ton of interest, and that the readers are passionate!!
Err, that's essentially what all cosmologists are saying: it's quite certain that dark matter and something like dark energy exists - but we don't know what it is, there are several competing hypotheses for that. Similar for inflation: there are also several competing hypotheses.
I wouldn't say that's outright "incorrect", merely a rather strange and unclear way to state that; as I mentioned, I know of no cosmologists using that term. And yes, there latter two terms are usual ones in cosmology.
Is there an end for the Universe ??? ...........
So how big is the entirety of our universe? I don't really care about the size of the multiverse.
Very interesting post. But how do you arrive at the lower limit of "10^(10^30) times the size of the observable universe" ?
"According to the theory of cosmic inflation and its founder, Alan Guth, if it is assumed that inflation began about 10â37 seconds after the Big Bang, then with the plausible assumption that the size of the universe at this time was approximately equal to the speed of light times its age, that would suggest that at present the entire universe's size is at least 1023 times larger than the size of the observable universe"
something is wrong here...
if the observable universe is apprx.say 14 billion LY then Non-obserbavle universe is Trillion trillion trillion.......times bigger than the observable universe. If whole people in the world run same as speed of the light for 1000 trillion yrs then if u calculate total distance is x LY but still non-observable universe will not end as per my theory.
With a universe this big, how am I supposed to take anything in front of me seriously?
"If only we could tap into the energy in that infinitely expanding space. We’d be gods!".. ...and IF we had invented the whole beautiful, complex, mind-blowing thing to begin with, we would be the ONE TRUE GOD.
As I read all the estimations of the billions of years (time) and lightyears (space), I was wondering when the Eternal (beyound time and space) would show up... and sure enough! And why? Because nothing that exists as (and in) time and space can be explained without it.
for all the brain power taking place here none of you wizards will ever step further into the universe than a monkey did 50 years ago......
Given an infinite amount of time and assuming other universes in multiverse are similar to ours, wouldn't we expect one of the other universes in a multiverse to have collided with our universe? As far as I know, we've seen no evidence of this having occurred.
Dark energy is a misnomer or deceptive (as bad as "Big Bang" which was not "big" nor was there any "bang"). What is involved is a negative PRESSURE not energy. Energy, according to E = mc³, has mass and General Relativity still says mass (energy) ATTRACTS mass. Just as Newton's laws were shown to have limitations, like don't use if GM/(Rc³) is too close to 1. Einstein's Relativities, have limitations too, like stay away from centers of black holes and huge energies involved with "Big Bangs". The inflation theory can not arise from Einstein's theories. Einstein's theories would not allow the huge energy involved to spread out but stay tightly bound by a huge gravitational attraction.
"wouldn’t we expect one of the other universes in a multiverse to have collided with our universe? "
Since the condition you gave was "Given an infinite amount of time" and an infinite amount of time hasn't completed, we can still be waiting for it.
You are correct, the condition I gave of an infinite amount of time was a poor choice of words. I was thinking in terms of an infinite amount of time that has occurred in the past outside of our universe. Maybe a better way to phrase the question is: Is the probability that another universe in a multiverse would collide with our universe exactly the same at all points in time in the lifespan of our universe? Or maybe even: As time passes, does the probability of a another universe colliding with our universe increase?
"I was thinking in terms of an infinite amount of time that has occurred in the past outside of our universe"
Still "infinite" turns up, so you're still going to have to find the right expression.
And something outside would be just as "infinite" in size, therefore the chance of "collision" still has a better chance of being "zero" than any other number.
And there's no way for infinity to pass, so how can the "past" you posit be "infinitely long ago"?
That's why these things are discussed in mathematics, where they have the words (mathematical procedures) to do so, consenting some axioms required.
Your statements, however, are getting an awful lot like the Brane Theories. Check those out with a google search.
"As time passes, does the probability of a another universe colliding with our universe increase?"
There is no reason why a fair coin's chance of getting a tails result should change with each toss of the coin. The chance, no matter how often a heads and only heads turns up, remains 50:50.
I never finished high school but I join the us navy at 18 to see the world and I did.I married my childhood sweetheart and have two great kids that went to collage and have done very well in life.I was a real good hvac mechanic and made a good living.so I am no dummy.I think the universe goes on in all directions and there is no end to it.it may meet other universes that also have no end until it meets other universes.this goes on and on forever with no end.don't be surprised if this high school drop out is wright and all the collage grads who think they have it wright are wrong ? but we all know we will never no.so like my father said to me son enjoy life because when your dead your dead for a long time.god bless the USA. and all good people on earth.
"I think the universe goes on in all directions and there is no end to it"
Do you have a REASON to think that? Have you tested whether your reason is correct?
After all I may believe that every ensign in the US Navy is a brainless grunt (I don't, picking this example to bring it home to you) but since I've never known anyone in the US Navy and have never tested the idea that I am right against evidence, my believing all US Navy personnel are brainless grunts is not the proof of its truth.
(PS the USA isn't blessed by God, the founders knew what happens when you have a theocracy and calling blessings from some god down on your country is one marker for a theocratic country, such as Iran)
PPS your spelling indicates you dropped out before high school, or at least never got anything out of it. Claiming to be right based solely on your say-so, you need to display characteristics to never be wrong. You have failed this.
Lots of insights and interesting comments above, some of them well beyond my comprehension but none the less I'd appreciate it if you guys would lift the veil so to speak regarding the shape of the universe and a couple of other points.
First of they say that the universe is flat, yet in near every depiction of the universe it's shown as a sphere.
Is that because the diameter of the sphere is so big that the segment of it that we can observe has such a large radius that it seems to be flat ?
Other than that, if the universe is 3D and expanding is it expanding in all 3 planes ? or is our onion skin becoming thinner ?
Add to that, they say that it all started with the big bang, some sort of explosion, but could the expansion of the singularity have been caused by the influence of another universe, some physical entity ? something pulling the singularity apart, something that still has a pull powerful enough to expand the universe ?
re #1, yes.
re #2, it's not posed in a question that means anything. The trite answer is no, but it really depends on what you're thinking of *in detail* and this isn't the place for that.
re #3, the name big bang was made up by the detractors to make the newcomer idea look silly. It stuck. So don't think it was a big explosion. Just a point in time when there was no feasible universe (too small to be differentiated, therefore not what we could understand as being a universe) that changed.
Universe has no specific shape. It is not flat at all.
You can think billions of years but so far you will not be able to finalize what is the shape of the Universe?
Hopefully somebody got the answer.
Our body is a 3 Dimension Physical body and our mind is still a 2 dimension representation of the world as you can imagine and visualize. I think in order to understand a little bit further like 4 Dimension space (multiverse and beyond) that we live in we need a 4 dimension body with a 3 dimension brain and thus we will all be clear and understand all of these. Take this can you imagine a 4 dimension cube in your mind. You cannot.
"Hopefully somebody got the answer."
Since you insist "Universe has no specific shape", then nobody can get the answer.
Who does try to understand the universe and all its secrets? Is he/she/it real? When we find about the entity who wants to understand universe, universe itself bares open all its secrets?
The Universe is real. It's where I keep all my stuff.
And I'm one of several entities who wants to understand it. So far all it's bared is cheek...
I have given the answer already for the shape of Universe and according to my theory it is final answer.
If people are satisfied with this answer then do you like to insist them to learn more?
If my answer is not correct then they can reject it and give new answer. All respective peoples are most welcome to write the correct answer with logic.
Note: I have spent a lot of time before I declare regarding the Shape of Universe.
I think you need to work out what "an answer" means, MM. You're having problems noticing that you haven't given an answer.
How can we be so assured that dark energy and dark matter really exist? Yes, both theories fit well into our current understanding, but neither has been affirmed with any kind of conclusive evidence. In a universe (multiverse) that many scientists suggest could be multi-dimensional, beyond the 4 that we are familiar with, it seems possible to me that the excess gravity postulated to be caused by dark matter and the inflationary force that we think of as dark energy may not even originate from within what we think of as our universe. In other words there may be no particles to be found here that we can prove are responsible for these phenomena. Just speculating.....
"How can we be so assured that dark energy and dark matter really exist?"
How assured do you think we should be?
"may not even originate from within what we think of as our universe."
How assured should we be of this, compared to the assurance that DM/DE exists?
See, we have a gradation of "assurance" and DE/DM are currently explanations of what the difference between the expected and observed system does from our understanding and what we can verify to be there.
Currently their actions ACT like matter and negative energy. Any alternative would have to ACT the same way, even if it were "positive energy being syphoned off to another universe".
Speculations are fine.
What's not so fine is starting off with a guarded attack on other, better supported, speculations so you can shoehorn your speculation in as "coeval" with the better evidenced one.
However, this is a non-sequitur for this thread and there are ones for the evidence of dark matter and dark energy to place this on.
Well, duh - Ethan, the TRUE size of our unobservable Universe is a mind-blowing thing to just think about! What the world calls our observable/unobservable Universe is TRULY the 2nd heaven... pick up and read a Bible, for God's sake! At the rate mankind keeps sinning, the One True holy God has to place some distance between us and Him. This explains why the “true” Universe, outside of our little pocket, is still inflating, and still expanding exponentially! Again, be less worldly and pick up and read a Bible, for God's sake! John
my head hurts
What a thrill it would be to wake up one day to discover we are living inside a black hole !
after reading and analyising the above data and comments on inflation and the mind boggling universe would it not be safe to acknowledge the words found at isaiah 40: 26 of jehovah who is stretching out the heaven like a fine gauze and controlling their expansion just as a skilled scientist would deal with his apparatus and at the same time monitor and evaluate his experiment. logically if the expansion is going on at calculatable rates then is it not logical that the observations are also being monitored. why coz an unmonitored experiment does not give rise to logical results but error and disorder, infact the expansion of the universe is orderly and the forces stable on the inside. conclusively i invite you to give credit to the one who created everything jehovah God and he is still creating more please read revelations 4:11
When religious kooks overcompensate for their insecurities about the the size of the universe and our insignificant place in it, out comes the Bible quotes and the God bullshit so they can attempt to feel in control and self important once again.
LTM, have you ever overcompensated based on the insecurity you have about the size of something you hold personal (and umm physical)?
Nope, Raggie, and what is your obsession with gay sex and men's penis size?
I have been saying this for years. I also believe that it is many orders of magnitude older than the 13.5 to 13.8 billion years old that is now accepted.