“What is wild cannot be bought or sold, borrowed or copied. It is. Unmistakeable, unforgettable, unshamable, elemental as earth and ice, water, fire and air, a quintessence, pure spirit, resolving into no constituents.” –Jay Griffiths

When you think about the frontiers of scientific knowledge — on the border between what’s known and what’s unknown — you have the phenomena that we know exist, yet that we can’t fully explain. This includes the matter-antimatter asymmetry, the inflationary origin of our Universe, dark matter and dark energy, among others. Yet two of these, inflation and dark energy, have an awful lot in common.

Image credit: Bock et al. (2006, astro-ph/0604101); modifications by me.

Image credit: Bock et al. (2006, astro-ph/0604101); modifications by me.

Are the expansive forces of inflation and dark energy related in some way?
It seems very strange that there should be 2 different forces that cause the universe to expand.

So goes today’s Ask Ethan question. Are dark energy and inflation related? There’s a whole class of models devoted to the study that they might be, but we have yet to have evidence come in, one way or the other.

Image credit: NASA / GSFC.

Image credit: NASA / GSFC.

Come right up to the frontiers of what is and what might be on today’s Ask Ethan!

Comments

  1. #1 Ragtag Media
    September 26, 2015

    “The early Universe’s inflationary period lasted for an indeterminate amount of time — possibly as short as 10^-33 seconds, possibly as long as near-infinite”

    How do you go from 10-33 to near Infinite time frame, what am I missing here.
    Anyone?

  2. #2 Wow
    September 26, 2015

    How do you go from 10-33 to near Infinite time frame, what am I missing here.

    The word indeterminate.

    Before a certain point, the laws of physics we know aren’t known to apply. Unification of forces may result in a very different model working. Including time’s progression.

  3. #3 Ragtag Media
    September 26, 2015

    Thanks peter breath, that really helps. I already had that from my Bible. Ya know chapter 1 verse 1 “In The beginning”.

    Heck wowzer your a preacher of another color..LOL

    No, you don’t just go from time it took for Inflation being a power of 10 of the plank time scale to infinity.

  4. #4 Ragtag Media
    September 26, 2015

    I could have gotten as much from see_no_fuk_all.. Wowzer.
    Now please give me a better “scientific” explanation other that just “indeterminate”.
    TIA

  5. #5 Ken
    September 26, 2015

    Ragtag: The inflation stopped (at least in our region of the universe). We do not know how long it had been going on before that; maybe a very short time, maybe a very long time.

  6. #6 Ragtag Media
    September 26, 2015

    Thanks Ken, that clarify’s it a bit better.

  7. #7 Narad
    September 27, 2015

    The inflation stopped (at least in our region of the universe).

    Beg pardon?

    We do not know how long it had been going on before that; maybe a very short time, maybe a very long time.

    Are you attempting to make a statement about the number of e-folding times for slow-roll inflation?

  8. #8 Wow
    September 27, 2015

    “Thanks peter breath, that really helps. I already had that from my Bible. Ya know chapter 1 verse 1 “In The beginning”.”

    Ya, the bible is no more reliable an account than Lord of The Rings, which ALSO has “in the begining”.

    But you asked a somewhat reasonable question so I answered it.

    However, you don’t WANT an answer from me, you just want to pick a fight.

    When whine (or have one of your creotard mates do it by proxy) about how I’m mean and aggressive to all people.

  9. #9 Ragtag Media
    September 27, 2015

    “However, you don’t WANT an answer from me, you just want to pick a fight.”
    Nobody needs to pick a fight with you deary all they have to do is ask a question and in your knee jerk mind they’re Jaqing off.

    You didn’t answer it you just hand waved with a “who knows” nobody…..

    Let’s try again then. ” The early Universe’s” see that, EARLY means around the beginning and Ken says this is in reference to our region of the universe.
    So did this inflation start from a beginning at around the Plank scale and time?
    Like in this tool where you can scale all the way down:
    http://htwins.net/scale2/
    0.00000000001 Yoctometers Is this the “Beginning” of Inflation?

  10. #10 Wow
    September 27, 2015

    “You didn’t answer it”

    Yes I did. The answer I gave was no different to the one Ken gave you, yet you thanked him for it.

  11. #11 Ken
    September 27, 2015

    Narad @7: Per Vilenkin, Steinhardt, Guth, etc. I am agnostic about whether eternal inflation is correct (as I understand it, you kind of have to be – if it is still happening, it’s way outside the part of the universe we can observe).

  12. #12 Carl
    USA
    September 28, 2015

    Like Ragtag Media, I was struck by the “indeterminate amount of time […] possibly as long as near-infinite” phrasing. But what puzzled me most was how it related to the next bullet, where the “early inflationary state was incredibly rapid”.

    “Rapid” is a rate, which depends on time. If time was indeterminate, how do we know the initial inflation was rapid? If we know it was rapid, can’t we bound the amount of time?

  13. #13 Ken
    September 28, 2015

    Carl @12: Rapid is deduced from the observable effects, such as the uniformity of the cosmic background radiation. Or maybe that should be required by the observed effects; a slower inflation would produce non-uniformities that we don’t see.

    The problem with bounding the time is that we don’t know how big the universe is. We know how big the part we can see is, but the whole thing might be much, much larger.

  14. #14 Michael Kelsey
    SLAC National Accelerator Laboratory
    September 28, 2015

    @Carl #12: Ken (#13) is correct about the inference for rapid inflation based on the observed uniformity of the CMB, as well as its nearly scale-invariant structure.

    You do raise a reasonable question for a non-expert: Since rate is distance/time, how do we know “rapid” if we don’t know the total time? Couldn’t inflation simply have been going on for a really, really long time, but slowly?

    Answering that means digging into the mechanics of what happens _during_ inflation (which Ethan has covered in several past blogs). Specifically, the effect of inflation on quantum fluctuations. Those fluctuations happen all the time, and inflation is what is able to “inflate” them to the macroscopic size needed to seed density variations for large scale structure.

    So what? These fluctuations happen randomly (duh :-), on time scales of around 10^-30-ish seconds, and length scales of 10^-30-ish meters (so within orders of magnitude of the Planck scales, and smaller by similar orders of magnitude than the strong nuclear force).

    Suppose inflation happens slowly, compared to the rate of those fluctuations. Then as a given “set” of fluctuations gets inflated larger, new random fluctuations get overlaid on top of them, washing out the variations. And that happens over and over again, so once inflation finally stops, you don’t actually have any “visible” inflated fluctuations to seed structure.

    On the other hand, if inflation is fast on the scale of the quantum fluctuations, then the last few “sets” get macroscopically huge so quickly that new ones are too tiny to wash them out. It is this part of how inflation functions which allows us to set a lower bound. Inflation had to proceed fast enough, that in something like 10^-33 seconds it could stretch a single quantum fluctuation up to a few microns (the visible Universe would have been about 1 mm across, and we see BAO peaks out to order 1000 or more), and do that _before_ any new quantum fluctuations could wash it out.

    I hope this answers your question, Carl.

  15. #15 Wow
    September 29, 2015

    “Rapid” is a rate, which depends on time. If time was indeterminate, how do we know the initial inflation was rapid?

    Yes, and the RAPID inflation took place in the inflationary period which is the point at which the “10^-33 seconds earlier” refers to.

    NOT the period BEFORE that.

  16. #16 Wow
    September 29, 2015

    Michael, you’re getting it wrong again. The RAPID is the inflationary period. The BEGINNING, t=0 time is 10^-33 seconds OR POSSIBLY MORE before that time.

    That is NOT the inflationary period. That’s the period during which we cannot make any physical inferences based on the physics we have here.

    Indeed the reason for the 10^-33 seconds is that there’s no way to put a “before” for any time interval less than that because it’s the smallest possible uncertainty in time, therefore any interval shorter would be co-incident.

    Inflation happened AFTER t=0 by some indeterminate time, but that time period after then, inflation was RAPID.

  17. #17 David L
    September 29, 2015

    @Wow: Michael, you’re getting it wrong again.

    I’m not following how your explanation makes his wrong. You seem to be saying the same thing unless you require “inflation” to be narowly defined as a property of our visible universe only. But surely inflation outside the region of what was to become our universe between t=10^-33 and t=start of “our” inflation can never be determined as any evidence it leaves will be in effects only visible on a scale larger than the visible universe? Which is the way I interpreted Michael’s post.

  18. #18 Carl
    USA
    September 29, 2015

    Thanks for trying to explain it! Here’s what I’m reading:

    Ken @13 says a “slower inflation” isn’t compatible with the smoothness we see.

    Michael @14 says “if inflation is fast” then there isn’t enough time for lumps to form (my crude terms, not his).

    In both cases, a slow expansion during the inflationary period is not compatible with what we observe. So – given the size of the universe – there is some upper bound on how long it took.

    Ethan says there isn’t any upper bound, so we have no idea how big the universe is (other than a lower bound, which is what we observe).

    I suppose those “big crunch” calculations that look at the entire Mass of the universe, must instead be looking at the Density? I’ve never heard it talked about that way, so I assumed they meant total mass.

    Wow @15,16 says the “RAPID inflation took place in the inflationary period”, and not before; that a tiny hot universe existed for an unknown time in some unnamed period before the inflationary period. That is not consistent with Ethan’s article, which only talks about the “inflationary period [which lasted] as long as near-infinite”.

  19. #19 Wow
    September 29, 2015

    “I’m not following how your explanation makes his wrong.”

    He’s explaining about what happened BEFORE inflation when the problem is inflation *which was later*.

  20. #20 Wow
    September 29, 2015

    “In both cases, a slow expansion during the inflationary period is not compatible with what we observe.”

    INCORRECT.

    And,indeed, David, why I said Michael got it wrong.

    The fast inflation happened 10^-33 seconds OR SOME INDETERMINATE DATE AFTER some precursive event.

    The inflation was fast AFTER that inflationary period started.

  21. #21 Michael Kelsey
    SLAC National Accelerator Laboratory
    September 29, 2015

    @Wow and Carl: Geez, I must have really been unclear in my comments. What I *thought* was doing was providing the justification for _why_ inflation has to be rapid. I wasn’t talking about “before” vs. “after” inflation at all.

    Rather I was contrasting a hypothetical “slow” inflation (which cannot produce the kind of seeds for structure we see in the CMB) compared to the actual “fast” inflation (which _can_ produce the seeds for structure we see).

    As Wow says, that fast inflation is what happened during _at least_ the 10^-33 seconds before it stopped and we got the hot Big Bang. Before that, inflation could have been going fast for a very long time, or a very short time, or anything in between.

    I am sorry for writing things in a confusing way.

  22. #22 Wow
    September 29, 2015

    “What I *thought* was doing was providing the justification for _why_ inflation has to be rapid. I wasn’t talking about “before” vs. “after” inflation at all. ”

    Well, what you were REPLYING to was asking how the inflation period could be considered fast if it took an indeterminate length of time.

    Here, again, since you seem to be slipping up on this reading thingy, is the origin of this thread:

    “Rapid” is a rate, which depends on time. If time was indeterminate, how do we know the initial inflation was rapid? If we know it was rapid, can’t we bound the amount of time?

    Which was prompted by Raggie’s post:

    “The early Universe’s inflationary period lasted for an indeterminate amount of time — possibly as short as 10^-33 seconds, possibly as long as near-infinite”

    How do you go from 10-33 to near Infinite time frame, what am I missing here.

  23. #23 Michael Kelsey
    SLAC National Accelerator Laboratory
    September 30, 2015

    @Wow #22: Oh, good! I didn’t misread the question, and I did answer it. Let’s take it in parts, and I won’t repeat the full reasoning; you can get that from my original response.

    “If time was indeterminate, how do we know the initial inflation was rapid?” It had to be rapid in order to inflate quantum fluctuations without having them washed out.

    “If we know it was rapid, [see above] can’t we bound the amount of time?” No, we can’t, because (as you, Wow, have also said) the rapid inflation itself wipes out any features of the preceding state.

  24. #24 Wow
    September 30, 2015

    Yes, Michael, but see Carl’s comment to see why your answer was wrong.

    It seemed to be telling him that we don’t know how fast it went because we don’t know how long it lasted.

    When that isn’t the point at all.

  25. #25 Dave Fogg
    Florida
    October 4, 2015

    To me dark matter is nothing more than a number we add to our equations to make the universe make sense to us. We can’t observe dark matter except through these equations. What if we have it all wrong.

    Many here will most likely think I am out of my mind, but please just give this some thought.

    Gravity, space and time may all be working together with one universally accepted concept inside out! Imagine that gravity is actually a repulsive force rather than attractive. We have always assumed gravity is a given attractive force, having never actually been explained WHY.

    I propose that space exerts a force and that beyond the limit of our universe no space exists. Beyond that is NOTHING.

    This force, I predict, exerts this force in all directions on any matter at any point in the universe. Gravity would result when two particles of matter intercept that force and negate an amount of the force provided by space between the two particles of matter resulting in a perceived attractive force.

    I know most of the people here are highly educated physicists and probably will disregard my ideas as crazy, but I believe this idea will allow for the abandonment of the idea of dark matter.

  26. #26 Wow
    October 5, 2015

    “To me dark matter is nothing more than a number we add to our equations to make the universe make sense to us”

    It acts like matter except it doesn’t interact by the electromagnetic forces. It’s not merely a number. It’s a thing. We just can’t describe that thing in the way we can with “normal” matter.

    “What if we have it all wrong.”

    Then we’ll find out by looking for what Dark Matter is. We certainly won’t find out by letting fear of being wrong stop us looking.

    “Imagine that gravity is actually a repulsive force rather than attractive. We have always assumed gravity is a given attractive force, having never actually been explained WHY. ”

    Because mass brings another mass closer to it. We can do measurements in the lab. And it doesn’t depend on distance to object only. It depends on the mass of the objects too, so your next “theory” is blown out of the water, since it predicts only distance matters.

    “I propose that space exerts a force and that beyond the limit of our universe no space exists. Beyond that is NOTHING.”

    I propose you write a paper for Nature on this and submit it for review. first,though, you’ll need to explain what this is doing to do away with dark matter.

    “I know most of the people here are highly educated physicists and probably will disregard my ideas as crazy”

    No, just massively undeveloped and unthought. It’s only crazy if you keep demanding that everyone take your WAG in its completely nebulous form and pretend it’s valid.

  27. #27 Wow
    October 5, 2015

    “That is not consistent with Ethan’s article, which only talks about the “inflationary period [which lasted] as long as near-infinite”.”

    Yes it is Carl.

    There was a period of superluminal inflation. BEFORE that was a period of nothing we can define with our known physics. That must have been at least one planck time before inflation started, but since our science doesn’t say what the hell happened before that point, we can’t say how long that period was.

    Simples.

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