“The creation of something new is not accomplished by the intellect but by the play instinct acting from inner necessity. The creative mind plays with the objects it loves.” -Carl Jung

13.8 billion years ago, the Universe as we know it came into existence. Today, the part we can observe is 46 billion light years in radius, having grown tremendously thanks to the expansion of the Universe. But if we extrapolate that backwards, we find that the Universe couldn’t have been infinitely small at the moment of its birth, but rather was a finite size at all finite times.

The size of the Universe (y-axis) versus the age of the Universe (x-axis) on logarithmic scales. Some size and time milestones are marked, as appropriate. Image credit: E. Siegel.

The size of the Universe (y-axis) versus the age of the Universe (x-axis) on logarithmic scales. Some size and time milestones are marked, as appropriate. Image credit: E. Siegel.

We know an awful lot about the moment the Universe can first be described by the hot Big Bang thanks to the last 50 years of modern cosmology. People used to think the Universe could be contained in a volume no bigger than a marble, or that the part accessible to us could have been the size of the Solar System at birth. No more!

Hospital Corpsmen 3rd Class Tarren C. Windham kicks a soccer ball with an Iraqi child. That soccer ball is approximately the size of the Universe we see today at the moment of its birth. Image credit: U.S. Marine Corps photo by Gunnery Sgt. Chago Zapata.

Hospital Corpsmen 3rd Class Tarren C. Windham kicks a soccer ball with an Iraqi child. That soccer ball is approximately the size of the Universe we see today at the moment of its birth. Image credit: U.S. Marine Corps photo by Gunnery Sgt. Chago Zapata.

Between the size of a soccer ball and a skyscraper-filled city block is the only range left, and the more we learn about inflation, the smaller that range will get. Find out the science behind it today!

Comments

  1. #1 Wow
    March 24, 2017

    As big as the entire universe. Duh.

  2. #2 Wow
    March 24, 2017

    PS Hey, look, no infinity….

  3. #3 Carl
    USA
    March 24, 2017

    No matter when or where, you can’t see / reach the “edge”. The speed of light creates the walls that forever box us in.

    Now to read the article!

  4. #4 Jonathan
    March 24, 2017

    Here’s what’s not very clear to me: if I understand correctly, the 17cm – 168m range you gave is for the size of the universe* at the last instant of inflation–in other words at the boundary between an inflationary phase (which could have lasted any length of “time”) and the hot big bang phase. Reaching back further into the inflationary phase, you say that somewhere between 10^-30 and 10^-35 seconds are “accessible” to us. In which sense is this period of time “accessible”, and how does the size of the universe* at the final instant of inflation depend on exactly how far back into the inflationary phase we can “access”?

    Maybe I have misunderstood and the diameter quoted is for the size when there was still 10^-30 or 10^-35 seconds of inflation remaining (hence the range). But in that case, what is special about that particular moment, which is not the beginning nor the end of the inflationary period?

    Also (*): since the part of the universe that we are discussing is somewhat arbitrarily bounded (it is the extent of the part that happens to have been in our light cone either now or earlier the universe’s history), why is the soccer ball or city block size actually meaningful enough to be plucked out? In all likelihood, that soccer ball was surrounded by similar stuff to itself, with no soccer-ball-sized boundary; not to mention, a tiny fraction of a second earlier the same stuff would have occupied a still smaller volume.

  5. #5 Wow
    March 24, 2017

    “Now to read the article!”

    Or read it first.

  6. #6 Wow
    March 24, 2017

    “In which sense is this period of time “accessible””

    The planck time is ~10^-35s and it’s IMPOSSIBLE to determine any event more accurately than that. So there is absolutely no way to determine the difference, no way for there to BE a difference between t=0 and t=10^-35s. That period is unavailable because there’s no way for those two times to be different.

    Remember the zero point energy thing? The planck time is the same as the chronology version of the zero point energy.

    Before 10^-30s there’s no known reason for it to be unable to determine what happened, but the energies are beyond what we can safely extrapolate from our experimental results. So we’d be guessing, in an informed sense, but still guessing.

  7. #7 Jonathan
    March 24, 2017

    I’m not sure you’re talking about the same inflation model as Ethan. In the traditional model, “the universe begins” at t=0 (the Big Bang singularity), quickly enters an inflationary phase that lasts 10^-thirtysomething seconds, then inflation ceases. But in the inflation model I think Ethan is talking about, inflation was going on for an indeterminate period before ending. I don’t think there is a special t=0 to be singled out before inflation ends. The period Ethan writes about, whose duration is somewhere between 10^-35s to 10^-30s, is the last portion of the inflationary period (the part we are mysteriously “connected to” in his phrase), but there is no word about inflation’s beginning. Inflation can even be past-eternal in some models.

    For sure your t=0 can’t correspond to the Big Bang in the model Ethan is talking about, because Ethan’s Big Bang occurs at the *end* of inflation. From what he writes, inflation was going on for who-knows-how-long before the Big Bang, there is a short final period of inflation that is “accesible”, and depending on how far back we can probe into that period, the universe’s size at the end of inflation is between a soccer ball and a city block. Here’s what he writes: “But if we’re talking about the observable Universe, and we know we’re only able to access somewhere between the last 10^-30 and 10^-35 seconds of inflation before the Big Bang happens, then we know the observable Universe is between 17 centimeters (for the 10^-35 second version) and 168 meters (for the 10^-30 second version) in size at the start of the hot, dense state we call the Big Bang.” And so part of my difficulty in understanding is that it’s not clear why the extent we can probe back into the inflationary period (whether it’s 10^-35 or 10^-30s before the Big Bang, call it t=B) should affect the size of the universe at t=B. Thanks.

  8. #8 Michael Mooney
    March 24, 2017

    The title premise assumes that there was a “moment of creation”… with no consideration of what existed before that or how it all came into existence “in the first place”… say in an eternally cyclical model.

    I agree with Jonathan (#4) that the size (at what micro-second?…) is an arbitrary choice. I think it is a demonstration of math expertise without empirical knowledge (like SR “knowledge” of shrinking objects. Check week #152 comments… still not answered.)

    Hawking had the cosmic origin as the primordial singularity, a point of no volume and infinity mass density. One must point out that a point has no volume to contain anything, let alone all the mass in the universe. This is not just “counter-intuitive,” it’s totally ” insane”( out of touch with “reality”) regardless of being the most famous physicist since Einstein.

  9. #9 Wow
    March 24, 2017

    ““the universe begins” at t=0 (the Big Bang singularity),”

    But there’s absolutely no difference in time between t=0 and t=10^-35s. They are the same time, just as anything less than a planck length away from another point is the same place.

    Therefore there’s no way to get to t=0 just like there’s no way to get to E=0, it’s always, for physics, e=h-bar.

    Zero point time like there’s zero point energy.

    Science cannot make any prediction at t=0 that is different from t=10^-35s. To physics, there is no difference, and to claim something about t=0 or even how it elapsed to get to t=10^-35. There’s no elapse.

    “because Ethan’s Big Bang occurs at the *end* of inflation”

    No, it does not. The Big Bang is before inflation. Inflation happens many plank times later. But there’s no way to make a claim about the elapse of time of planck time length.

    It’s Big Bang, “some unphysical time later (planck time)”, the earliest it’s possible for physics to remain applicable, then inflation, then much much later disassociation then the last of the big bang remnant visible as the CMB today.

  10. #10 Wow
    March 24, 2017

    “The title premise assumes that there was a “moment of creation””

    It does not. There are many solutions that do not get to a moment of creation. Only one goes through the origin at t=0, a “moment of creation”.

    And that’s irrespective of the impossiblity of science to find anything about events “before” planck time.

    Oddly enough, that includes the difference before t=”planck time” that it was “really” 10^-35s earlier. There was a post Ethan did on the indeterminacy of time before the earliest physically possible claim of time. E.g, just as a theoretical idea, what if the constants that define the planck constant change by many orders of magnitude, either bigger or smaller? Then that first instant doesn’t last as long as it would in the laws currently would define it.

  11. #11 Wow
    March 24, 2017

    “hat the size (at what micro-second?…) ”

    The first one. The first elapsed microsecond. 10^29 plank times later. For which the difference between that and the origin is ten parts in one quintillion. Pretty small.

  12. #12 Wow
    March 24, 2017

    Oh, I was using the order of magnitude for planck length. Deduct another order of 8 because you divvy by the speed of light. 10^-43s, et al.

  13. #13 Bob
    United States
    March 24, 2017

    I have what may be a really stupid question. . .if the universe extends 46.1 billion light years in every direction from Earth (taken from the full article), doesn’t that imply Earth is at the center (also implying the universe is spherical)?

  14. #14 John
    Baltimore
    March 24, 2017

    A very enjoyable read!

  15. #15 Wow
    March 24, 2017

    Good grief.

  16. #16 John
    Baltimore
    March 24, 2017

    Oh dear.

  17. #17 Jonathan
    March 25, 2017

    I wrote: “because Ethan’s Big Bang occurs at the *end* of inflation” and Wow replied: “No, it does not. The Big Bang is before inflation. Inflation happens many plank times later.”

    Now I’m positive you are not referring to the same model of inflation as Ethan is describing. Please could you read carefully what I quoted from Ethan’s article: “But if we’re talking about the observable Universe, and we know we’re only able to access somewhere between the last 10^-30 and 10^-35 seconds of inflation BEFORE THE BIG BANG HAPPENS [emphasis added], then we know the observable Universe is between 17 centimeters (for the 10^-35 second version) and 168 meters (for the 10^-30 second version) in size at the start of the hot, dense state we call the Big Bang.”

    This is very clear that Ethan is discussing an inflationary model without a Big Bang singularity that initiates anything. Instead what Ethan calls the “hot Big Bang” begins at the *end* of inflation. I think these competing models of inflation not being resolved properly leads to some confusion. For my part I always used to think that inflation followed the Big Bang, and the sequence of events was: Big Bang -> inflation begins -> inflation stops/the current mode of universe expansion begins. But in a more modern (?) model there is an unspecified beginning, and I can’t figure out what is special about the last portion of the inflationary period and why its length determines the size of the universe at the end of inflation. How does the length of the last portion of inflation–the portion “accessible” to us–influence the size of the universe at its end, given that the inflationary period was longer than the portion accessible to us?

  18. #18 Naked Bunny with a Whip
    March 25, 2017

    A refresher on what Ethan means by “the Big Bang”.

  19. #19 Wow
    March 25, 2017

    “Now I’m positive you are not referring to the same model of inflation as Ethan is describing.”

    No. The interpretation you are supplying is yours.

    Of course, Ethan could clear it up, but hes not involving himself here, is he.

    And so we go round in circles, each having read a different meaning, and both having to read minds to do it when the mind thinking it is sitting silent and letting the pointless round-and-round continue….

  20. #20 Wow
    March 25, 2017

    “This is very clear that Ethan is discussing an inflationary model without a Big Bang singularity”

    And stop reading me saying there was a big bang singularity. I haven’t. YOU supplied that then assigned to me, it appears.

    “But in a more modern (?) model there is an unspecified beginning”

    That still doesn’t say there’s a big bang AFTER (or even during) the inflationary period. It appears that you have been making that claim yourself alone.

    “I can’t figure out what is special about the last portion of the inflationary period and why its length determines the size of the universe at the end of inflation”

    This was not your original question, though.

    “In which sense is this period of time “accessible””

    Was your original question I was answering.

    Yet again you either read something not there then supplied it as the words of someone else, or you’re whiffing those goalposts about.

    What is the problem with the answer to your original query? If none, then we’re done here. I’m not particularly interested in debating or informing someone who doesn’t know what they want to know but inquire anyway.

  21. #21 John
    Baltimore
    March 25, 2017

    @ #17 Jonathan,

    “… what Ethan calls the “hot Big Bang” begins at the *end* of inflation …”

    http://scienceblogs.com/startswithabang/2010/01/12/q-a-did-inflation-happen-befor/

    Last paragraph.

  22. #22 Wow
    March 25, 2017

    Good grief, you actually posted something that was actually relevant and informative rather than empty chinny stroking.

    Will wonders never cease.

    ‘course the medium post indicates there was no big bang. Partly because the original intent of the name big bang no longer applies. Bunny already added that.

    But goodness me, when it comes to actually posting something to make be wrong, you suddenly find information to be available and don’t want to post empty meaningless noise!

  23. #23 Wow
    March 25, 2017

    Here’s some information too.

    http://www.physicsoftheuniverse.com/topics_bigbang_timeline.html

    i kinda keep to the original intent, as modified by reality, since the original Big Bang name was intended all along to ridicule this in the face of steady state theory as being some sort of creationist back door.

    Science shouldn’t care whether a priest or creationist comes up with an idea, it should only care if the explanation words better than competing explanations.

    One of many reasons why science isn’t a reason, nor cult, nor even a clique of elites.

  24. #24 John
    Baltimore
    March 25, 2017

    Some other time perhaps …

  25. #25 Wow
    March 25, 2017

    …explanation works better….

  26. #26 Wow
    March 25, 2017

    Really? Interesting that it will be some other time, and then only maybe.

  27. #27 Jonathan
    March 25, 2017

    Wow wrote: “Yet again you either read something not there then supplied it as the words of someone else, or you’re whiffing those goalposts about. What is the problem with the answer to your original query? If none, then we’re done here. I’m not particularly interested in debating or informing someone who doesn’t know what they want to know but inquire anyway.”

    Wow, the irritation in your response suggests you believe it’s unreasonable to follow up to the question I asked, even though your answer was completely incompatible with Ethan’s post. You wrote that inflation happens after the big bang, I pointed out where Ethan wrote about inflation happening before the big bang, and so your answer was clearly premised on a different model than Ethan was using. And yet you tell me you’ve already answered the question, and that it can only be an absence of good faith that makes me keep asking; the implication from your tone is that I’m an idiot. Look, what you write here in your last answer is so clearly incompatible with what Ethan wrote:

    “That still doesn’t say there’s a big bang AFTER (or even during) the inflationary period. It appears that you have been making that claim yourself alone.”

    Ethan’s writings are clear that what he refers to here as the Big Bang happens after the inflationary period. I even quoted it, twice, in my comments so it would be clear; I didn’t make that up just to troll here. And yet, from seeing you at work with other posters, I know there is zero chance that you will acknowledge being wrong. You post too much, too carelessly, and too angrily, for it to be worthwhile to try to turn a conversation with you into anything helpful.

    Lastly you wrote this: “This was not your original question, though. “In which sense is this period of time “accessible”” Was your original question I was answering.” –yes, that was part of my original comment, but it went on to ask more. Understanding in which sense this part of the inflationary period is accessible is a preliminary to the main question, which I rephrase here below. Could you please not reply to me any more? Your replies are less than helpful. In any case, you say you’re interested in continuing the discussion with someone like me. If your intention was to be helpful then thank you, but it’s not working.

    For anyone else or for Ethan, the question is: we are given a model of inflation in which, going backwards in time, we have time T, which is the end of inflation and the beginning of the current phase of expansion; before that is time S, which is the earliest “accessible” point of the inflationary period; before that is *perhaps* a point R which is the beginning of the inflationary period (but in past-eternal models of inflation there is no point R). We are interested in the size of the currently visible universe at time T. Ethan says: if time S is 10^-35s before time T, then the universe’s size at time T was that of a soccer ball. If time S is 10^-30s before time T, then the universe’s size at time T was that of a city block. The question is: what has the duration between time S and time T got to do with the size at time T? However long the accessible duration of inflation turns out to be, inflation had been going on for longer than the interval S-T.

    That’s as clear as I can make it!

  28. #28 Wow
    March 25, 2017

    “the irritation in your response suggests you believe it’s unreasonable to follow up to the question”

    The incivility of not saying that your query was answered and instead write, and I quote:

    “I’m not sure you’re talking about the same inflation model as Ethan”

    Which certainly implies that your question was not answered is precisely the incivility you were so dead set against and nowhere is an acknowledgement the answer you were for had arrived.

  29. #29 Jonathan
    March 25, 2017

    Wow, I wrote that I didn’t think you were referring to the same model as Ethan, because it seemed to me that that meant your partial response to the questions I asked was inoperative. Now, it turns out to have been correct that you weren’t referring to the same model used for the calculations I asked about, and so instead of saying “I’m not sure you’re referring to the same model”, I could have more plainly said “You’re talking about something different”. Or do you still think that your answer, which was premissed on a determinate period of time between an initial big bang and the end of an inflationary period, could possibly be a good answer to a question that was about calculations made in an inflationary model with no determinate beginning to inflation? I ask again: why should the depth to which we can access an inflationary period affect the size of the universe at the end of that inflationary period?

  30. #30 Wow
    March 25, 2017

    And you didn’t say “Oh, right, I see. OK, but now this is what I don’t get….”.

    But, hey, go wait for Ethan to talk and then tell him what you think is different between our models.

  31. #31 Michael Mooney
    March 25, 2017

    I never thought i would be quoting Wow here, but I agree with this from #19: “Of course, Ethan could clear it up, but hes not involving himself here, is he.
    And so we go round in circles, each having read a different meaning, and both having to read minds to do it when the mind thinking it is sitting silent and letting the pointless round-and-round continue….”

    The same applies to both the origin of the universe (“What was there before that?”) and the length contraction debate which he started, obscured, and now refuses to address, let alone try to resolve. I think it’s just the “famous physicist” syndrome… like when they become too popular and busy to clean up their messes. (Forget about it! On to the next popular subject!) This is the last I have to say about that. Enjoy your fame, Ethan. Or maybe you could designate a “Starts With A Big Bang” physicist friend to resolve the stuff you abandon.

  32. #32 Jonathan
    March 25, 2017

    Ok. I sincerely acknowledge that there was a partial answer in that you pointed out that accessibility of a certain portion of the inflationary period is due to the energy scales involved. To be honest, though, it doesn’t help that much. I don’t believe that accelerator physics can give an insight into physics during an inflationary regime. And it doesn’t help to understand why the extent to which we can access a portion of the inflationary period affects the size of the universe at the end of that inflationary period.

    I also thank you for explaining that the Planck length plays a role, but in fact I don’t believe that has much to do with anything. You talked about the fraction of a second between t=0 and t=10^-35s being of the order of magnitude of the Planck duration and thus inaccessible. But this is irrelevant; there is no t=0 in the model Ethan was referring to.

  33. #33 Wow
    March 25, 2017

    “What was there before that?”

    “Before” doesn’t exist before time.

    “But this is irrelevant; there is no t=0”

    There isn’t in mine either. It is identical to t=10^-43s. No t=0.

  34. #34 dean
    March 26, 2017

    Michael, you’ve demonstrated multiple times that you do t like many parts of physics because you don’t understand it and don’t like what you think it says. Bring stupid conspiracy “famous physicists” theories into things doesn’t help at all.

  35. #35 Michael Mooney
    March 26, 2017

    Dean, I understand that SR is the physics of observational differences (from relativistic frames of reference) and that there is no physics of shrinking physical objects in the macro-world beyond atomic physics, in spite of SR’s claims. No one here, including Ethan will address that, other than his admission (one time) regarding the latter, “We don’t think so,” but length contraction between stars is still “real”… with no explanation of the difference.

    I also understand that it is no different than belief in magic or religious myth to make claims about “In the beginning…” there was nothing and then everything in the universe magically manifest in either a “point with no volume” (Hawking’s singularity) or a ball of whatever “stuff” and size.

    Objective realism is the world view that the cosmos exists in and of itself, independent of observational frames, and that it did not magically manifest out of nothing at “the beginning of time.”
    I welcome scientific and philosophical dialogue on the above without personal attacks.

  36. #36 Wow
    March 26, 2017

    “and that it did not magically manifest out of nothing at “the beginning of time.””

    Well we welcome the “objective realism” treatments of the origin of the universe, then.

    It has to do better than the standard model…

  37. #37 Wow
    March 26, 2017

    “without personal attacks.”

    Remember, doesn’t know what they are, but thinks they will stop people saying things he doesn’t want to hear.

    Plus when HE does it, since it doesn’t upset him, isn’t “personal attack”.

    IOW:

    Dean: “crackpot site” == “personal attack!”

    Mooney: ” true SR believers” == “Just fair description!”

  38. #38 Wow
    March 26, 2017

    “and that there is no physics of shrinking physical objects in the macro-world beyond atomic physics”

    Wrong.

    But you’re sticking to SL’s “option a” when it’s been answered and shown you are wrong, and why.

  39. #39 dean
    United States
    March 26, 2017

    “Dean, I understand that SR is the physics of observational differences (from relativistic frames of reference) and that there is no physics of shrinking physical objects in the macro-world beyond atomic physics,”

    Clearly, you don’t – or you don’t want to, because the results of the physics violates your “common sense” view of the universe.

    Your continued reference to “the cosmos exists in and of itself, independent of observational frames” indicates that you may have mastered some of the math — which is a tentative statement, since none of your rebuttals have been based on anything mathematical — without understanding the ideas behind them.

    And, these are not personal attacks – these are observations based on your behavior.

  40. #40 bill wesley
    san diego california
    April 1, 2017

    Objective analysis can accommodate any concept, for example if we accept the idea that celestial bodies are mounted on concentric transparent spheres we can construct all kinds of objective mathematical means to justify what we observe based on that concept. Once we have fine tuned the concept to fit the observed facts we can claim the facts verify the concept.

    Often the basic concept itself is arrived at by intuition, for example the basic inutitive notion that all matter is attracted matter (Newtonian gravitation) is intuitive, math is used to precisely define this intuitive concept to see if it fits the facts

    Different intuitive concepts can fit the same facts, for example the intuitive concept that all matter attracts space rather than other matter (general relativity) covers all the same facts as the intuitive concept that all matter attracts other matter. The intuitive concept that all matter attracts space was discovered to cover some additional facts not covered by the intuitive concept that all matter attracts other matter so the second concept of General relativity won out.

    This does not mean General Relativity is the end of the line, if it is not able to cover all the facts that is a sign there may be a another intuitive concept that will succeed where it fails, and indeed it does not cover all the facts

    The danger in science is to focus on observation and math at the expense of reconsidering intuitive concepts. Intuition is treated as “unscientific” but the greatest minds in science always proceed from intuitive insight initially.

    Without arguing all the details the cosmological model presented herein does not seem intuitively correct , it looks like the product of outdated concepts carried beyond their logical shelf life by minds which are brilliant at rationalizing even the most absurd conundrums but which are not capable of using intuitive insight to over come them. Intuitive conjecture is often ridiculed, it takes near immunity to social pressure for an individual to treat it as insight.

    Excessive Intelligence does not usually break an intellectual log jam, it is usually broken by the kind of reckless intellectual bravery that few can afford to manifest, the current cosmological model very much looks for all the world like the modern version of epicyclic theory.

  41. […] How big was the Universe at the moment of its creation? (Synopsis) [Starts With A Bang] […]

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