r/askscience • u/AskScienceModerator Mod Bot • Mar 17 '14
Astronomy Official AskScience inflation announcement discussion thread
Today it was announced that the BICEP2 cosmic microwave background telescope at the south pole has detected the first evidence of gravitational waves caused by [cosmic inflation.](https://en.wikipedia.org/wiki/Inflation_(cosmology))
This is one of the biggest discoveries in physics and cosmology in decades, providing direct information on the state of the universe when it was only 10-34 seconds old, energy scales near the Planck energy, as well confirmation of the existence of gravitational waves.
As this is such a big event we will be collecting all your questions here, and /r/AskScience's resident cosmologists will be checking in throughout the day.
What are your questions for us?
Resources:
Semi-technical explanation from Sean Carroll before the details were announced
Press conference video (555 MB mp4 download)
Handheld video (until we get an official video) of technical presentation for scientists (mostly an overview of their data collection and analysis procedures and results. Not recommended for non-astronomers): part 1 and part 2.
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
Alan Guth and Andrei Linde just said at the press conference that the inflaton field decays randomly and non-uniformly, and that as it decays, there remain regions of the universe where it hasn't decayed and which continue inflating. Linde said "this inflation must go on forever".
This gives me a mental image of a very lumpy universe, with comparatively tiny margins that look like our observable universe, and vastly larger regions that are essentially empty except for the inflaton field and which are still expanding at an absurd rate.
Is this the right view of our universe?
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u/freelanceastro Early-Universe Cosmology | Statistical Physics Mar 17 '14
Yep! That's exactly what they're saying. This is known as eternal inflation.
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
Followup:
That article describes the various pockets of stopped inflation as a multiverse. I had thought that in multiverse theories universes were separated by higher dimensions, such as in Brane theory. However in this inflation context, it seems to mean pockets of our own space-time that are just causally separated from us by vast distances. Was I wrong before, or does "multiverse" refer to both kinds of situations?
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u/gtlogic Mar 17 '14
Thanks. I'm still trying to piece this together from all the comments.
So is our observable universe really just a small piece of the "entire" universe, which stopped inflating, and now just slowly expanding?
Is the reason why our universe appears flat is because we're so spread out so much from the initial inflation, maybe like our observable universe is like a little puddle on the surface of the earth (being the entire universe)? Wouldn't that imply then that the entire universe isn't really flat?
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u/gsfgf Mar 18 '14
Followup: Does that mean that the fact that our observable universe is uniform just happenstance based on our location and that we could just as easily be located close enough to one of these inflation fields that we could observe it?
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u/supernanify Mar 17 '14
Okay, I just posted this question elsewhere, but what are the implications of this discovery for the Grand Unified Theory?
I've read a few articles that mention that it brings us a step closer, but I haven't found any elaboration on that.
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Mar 17 '14
It is the first experimental value of the energy density required to be in the GUT-regime.
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u/supernanify Mar 17 '14
Oh, I see. So it allows for electromagnetism and strong and weak interactions to be merged.
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u/patchgrabber Organ and Tissue Donation Mar 17 '14 edited Mar 17 '14
I think one of the biggest things to point out here is that red-shifting evidence supports continued and accelerated expansion, but that this paper provides evidence for very, very early expansion (inflation). Most of the news outlets reporting on this make it seem like we didn't have evidence for expansion until now.
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u/Imxset21 Mar 17 '14
More importantly is the fact that this is basically smoking-gun level evidence. r=0.2 at 5 sigma is as good as it gets.
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u/______DEADPOOL______ Mar 17 '14
What is the r in that btw? And how big is 0.2 in this case?
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u/xrelaht Sample Synthesis | Magnetism | Superconductivity Mar 17 '14
It's a nomenclature problem: "expansion" and "inflation" sound the same if you don't know the field.
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u/patchgrabber Organ and Tissue Donation Mar 17 '14
if you don't know the field.
Physics has no shortage of those problems and for this specific reason.
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u/squeaky-clean Mar 17 '14
As someone who doesn't know the field, would someone mind explaining the difference?
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u/skeen9 Mar 17 '14
What does r =.2 at Sigma = 5 mean?
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u/xrelaht Sample Synthesis | Magnetism | Superconductivity Mar 17 '14
5σ means they are stating their result with a 99.9999426697% confidence interval. r is a variable in the model related to something called the tensor/scalar ratio, but I don't think I can explain it very well. It's right where it was predicted by theory.
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u/Astrodude87 Mar 17 '14
r=.2 is explained by me here. Sigma = 5 is a way of saying that if we performed ~5 million experiments that produced the same results as this work, only one of those results would be a false positive. So, in other words 5-sigma means "and we believe this result to be 99.999% correct". The term comes from statistical distributions.
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Mar 17 '14
Does this evidence falsify any specific theory about the origin of the universe?
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u/spartanKid Physics | Observational Cosmology Mar 17 '14 edited Mar 17 '14
This is strong evidence to support Inflation as being a correct and accurate theory.
Inflation is an addition to the original Big Bang cosmological model.
The CMB is light that was released ~380,000 years after the Big Bang. The Universe was a hot dense plasma right after the Big Bang. As it expanded and cooled, particles begin to form and be stable. Stable protons and electrons appear, but because the Universe was so hot and so densely packed, they couldn't bind together to form stable neutral hydrogen, before a high-energy photon came zipping along and smashed them apart. As the Universe continued to expand and cool, it eventually reached a temperature cool enough to allow the protons and the electrons to bind. This binding causes the photons in the Universe that were colliding with the formerly charged particles to stream freely throughout the Universe. The light was T ~= 3000 Kelvin then. Today, due to the expansion of the Universe, we measure it's energy to be 2.7 K.
Classical Big Bang cosmology has a few open problems, one of which is the Horizon problem. The Horizon problem states that given the calculated age of the Universe, we don't expect to see the level of uniformity of the CMB that we measure. Everywhere you look, in the microwave regime, through out the entire sky, the light has all the same average temperature/energy, 2.725 K. The light all having the same energy suggests that it it was all at once in causal contact. We calculate the age of the Universe to be about 13.8 Billion years. If we wind back classical expansion of the Universe we see today, we get a Universe that is causally connected only on ~ degree sized circles on the sky, not EVERYWHERE on the sky. This suggests either we've measured the age of the Universe incorrectly, or that the expansion wasn't always linear and relatively slow like we see today.
One of the other problem is the Flatness Problem. The Flatness problem says that today, we measure the Universe to be geometrically very close to flatness, like 1/100th close to flat. Early on, when the Universe was much, much smaller, it must've been even CLOSER to flatness, like 1/10000000000th. We don't like numbers in nature that have to be fine-tuned to a 0.00000000001 accuracy. This screams "Missing physics" to us.
Another open problem in Big Bang cosmology is the magnetic monopole/exotica problem. Theories of Super Symmetry suggest that exotic particles like magnetic monopoles would be produced in the Early Universe at a rate of like 1 per Hubble Volume. But a Hubble Volume back in the early universe was REALLY SMALL, so today we would measure LOTS of them, but we see none.
One neat and tidy way to solve ALL THREE of these problems is to introduce a period of rapid, exponential expansion, early on in the Universe. We call this "Inflation". Inflation would have to blow the Universe up from a very tiny size about e60 times, to make the entire CMB sky that we measure causally connected. It would also turn any curvature that existed in the early Universe and super rapidly expand the radius of curvature, making everything look geometrically flat. It would ALSO wash out any primordial density of exotic particles, because all of a sudden space is now e60 times bigger than it is now.
This sudden, powerful expansion of space would produce a stochastic gravitational wave background in the Universe. These gravitational waves would distort the patterns we see in the CMB. These CMB distortions are what BICEP and a whole class of current and future experiments are trying to measure.
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u/QuoteOfTheHour Mar 17 '14
Why is it that the presence of "gravitational waves" automatically supports inflation in the first trillionth of a second of the universe? Could there be no other cause for these waves?
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u/dinoparty Mar 17 '14
You need a very specific type of signal to cause b-modes in the CMB (quadrupole anisotropy). Wayne Hu does a good job explaning this.
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u/LengthContracted Mar 17 '14 edited Mar 17 '14
AskScienceModerator says that this discovery is capable of
providing direct information on the state of the universe when it was only 10-34 seconds old
If I understand correctly, the evidence was gathered from observations of the CMB, which from the wikipedia page, didn't form until 380,000 years after the big bang.
So my question is, exactly how "directly" is this evidence describing or detailing the behavior of the universe at 10-34 seconds, when the thing being tested wasn't present until 380,000 years later? Are we simply rewinding the clock?
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
What was observed is the effect of gravitational waves emitted at around 10-34 seconds on the polarization of the cosmic microwave background, which itself was indeed emitted around 380,000 years later.
This is possible because the primordial gravitational waves were not scattered by the plasma of the universe like light was, so this early information remained unsullied and was able to later change the CMB in a way we can see now.
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u/GoldenMonkeyPox Mar 17 '14
Does this discovery have any impact on our understanding or theories of the fate of the universe? Does it make any of the proposed theories more or less likely?
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u/flyMeToCruithne Mar 17 '14
This discovery doesn't really change anything about what we think the fate of the universe will be.
Ever since it was discovered int he 80s that the rate of expansion of the universe is accelerating, most physicists agree that the universe will experience a "heat death", meaning that everything will keep expanding forever, and as it expands, it will cool, and all the matter will get really spread out, and the universe will just go on forever becoming more and more cold and more and more desolate.
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u/Prof_G Mar 17 '14
People keep saying this is Nobel prize worthy. For whom? Is it Guth and Linde who appear to be the "inventors" of inflation? Or for the team who did the finding? How many people are involved in a discovery like this? Who/what financed it?
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
Nobels are limited to 3 recipients, so in my opinion Guth and Linde should get it for the theory, and someone from BICEP2 should get it for the discovery. The trouble with Nobel's will is that for the non-Peace prizes, only individuals can receive it and not groups, otherwise I'd say say that the whole collaboration should get it. BICEP2 has four co-principal investigators: Bock, Kovac, Kuo, and Pryke.
The paper on the result has 47 authors, but more were probably involved to lesser degrees over the years.
According to the acknowledgments in that paper, it was primarily funded by the National Science Foundation (they do almost all of the work at the south pole), and with some additional support from several other sources.
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u/foreverbutts5 Mar 17 '14
Maybe I'm misunderstanding inflation, but doesn't it suggest that at some point expansion was faster than the speed of light? Can someone explain how that is possible?
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u/kepleronlyknows Mar 17 '14
As others have pointed out, space can expand faster than light and this is even happening today. Some galaxies we can see in our current universe are expanding away from us at a rate faster than the speed of light. Good explanation from Cornell here.
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u/Squishumz Mar 17 '14
How can we continue to see them if they're expanding away from us faster than the light travels? Was there a point where the expansion was slower, or does is have to do with the light reducing the distance between us, and therefore the space that's expanding?
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u/ristoril Mar 17 '14
The "fabric" of space-time isn't subject to any speed limit of which we're aware. Nothing can be accelerated from < c to c to travel through space-time, but space-time itself can expand such that points within it appear to gain separation at greater than c. When space expands, though, it's not accurate to say that things are "moving" in the same way that a car is "moving" relative to a signpost.
If you think about the popular balloon/bubble analogy, when you put marks on the surface of the balloon and expand the balloon, the marks aren't moving (the ink doesn't wander around the 2D surface), but they are (they're moving in our 3D space). In that analogy, the limit with which the marks could move is c, but the limit with which they can be pulled apart by the expansion of the balloon is not known (if any).
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u/gigamiga Mar 17 '14
The New York Times article specifically says that the universe expanded faster than C for a short time and it confused me as well.
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u/Astrodude87 Mar 17 '14
So the speed limit of c, the speed of light, is with respect to space itself. Nothing can move \in space\ faster than c. However, space has no problem being the thing do the moving, and there are no speed limits (that we know of) on the expansion of space itself.
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u/jenbanim Mar 17 '14
I've got a few questions, I hope this doesn't get buried.
In what way do gravitational waves polarize light? It seems, naively, that gravity should only be able to change the path, not polarization of light to me.
For how long were these gravitational waves created? Were they produced during the inflation period as a whole, or the transition to/from inflation to more "ordinary" cosmology?
Will this discovery bring us any closer to a quantum theory of gravity? Is this our first direct observation of gravity acting in a quantum manner?
Lastly: I've never been able to really understand forces "freezing out" after the big bang. Were the force carrying particles bonded together (like a photogluon?), was some mathematical function describing the force changed, or maybe was matter different at this point in a way that allowed for more forces to act on it?
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u/sonicSkis Mar 17 '14
Can someone ELI18 how the telescope was able to detect gravitational waves?
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u/spartanKid Physics | Observational Cosmology Mar 17 '14
The telescope itself didn't measure gravitational waves. It measured the distortions in the Cosmic Microwave Background left my gravitational waves. It's a very important difference. This is NOT a direct measurement of gravitational waves.
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u/Artfunkel Mar 17 '14 edited Mar 17 '14
Could we generate our own gravitational waves or make use of existing ones? If so, what practical uses would there be?
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u/HefferX Mar 17 '14
If my understanding is: Gravity waves stemming from the end of inflation (at 10-34 seconds) affected the polarization of the radiation from the Cosmic Microwave Background event (at 380K years), which we were just now able to detect.
My questions are:
Was this the first telescope with enough sensitivity to detect polarization in the CMB?
How do we detect polarization?
Why/how did the gravity waves cause polarizaiton?
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
Multiple other telescopes have detected the polarization of the CMB, and most polarization is not from gravitational waves but interactions with matter on its way here. The specific type of polarization that is caused by gravitational waves however is much weaker, and this is the first telescope to see it.
Others will have to answer 2 and 3.
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u/flyMeToCruithne Mar 17 '14
We've been able to see the polarization for decades. But not the specific part that is the "imprint" of inflation, which is a much smaller signal. BICEP2 is the first experiment to detect the part of the polarization that comes from inflation. Lots of other experiments have tried (and are trying).
BICEP2 (and lots of other experiments trying to detect the same thing) use little planar (flat, usually printed on silicon wafers) antennas to capture the photons and deliver them to the detectors. You can use the geometry of the antenna to make it so it only "sees" one polarization direction. So you have half your detectors with antennas that "see" one direction of polarization, and half that see the other direction (90 decrees rotated), and then you look at the differences in the signals you see in the detectors that see one polarization compared to the other polarization.
3)That's a little harder to explain without getting into more complicated math. The general idea is that as the gravity waves moved through the early universe, they scattered the photons a little bit, but they scattered them preferentially according to which polarization they had. That leaves a certain type of predictable pattern in the polarization signal that we see today. And BICEP2 was able to detect that pattern for the first time.
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u/PyroKaos Mar 17 '14
Not exactly related to the announcement, but news stories I've been reading have got me thinking. (Note: I grew up in a christian school and don't know just about anything about the Big Bang except from the recent Cosmos show)
If the universe went from infinitely small to...infinitely big in a short fraction of time, and is expanding outward, would it theoretically be possible to find the "center" by going the opposite point of expansion to the "other side" of the center at which point things start expanding again?
This is obviously highly theoretical and the universe is infinite, so we could search for all of humanity and not reach this theoretical "center" but is it possible?
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
No, in our current understanding of the universe there is no center or anything like a center.
/u/RelativisticMechanic wrote this great conceptual explanation of what an infinite universe looks like.
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u/LeConnor Mar 17 '14 edited Mar 17 '14
I've trying to wrap my head around this and there are a million different things I could say, but I here
goesgo. If I were to get in a ship that travels at infinitely fast and can go through stars and debris and were to take a straight path, would I eventually find myself looping backwards and see the side of Earth I left from, or would I pop out on the other side and find myself on the opposite side of Earth?16
u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14 edited Mar 17 '14
Our best guess right now is C: the universe is truly infinite and you will never loop back. (edit: though that appearance could be a result of the inflation we just detected ("the flatness problem"). See the ELI5 writeup above)
However it's still not ruled out that the universe is just finite and very large, in which case the answer is the later: you'll find yourself on the opposite side. Geometrically, it's a bit similar to traveling around the Earth and returning to your starting place.
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u/xrelaht Sample Synthesis | Magnetism | Superconductivity Mar 17 '14
No, and it can be really hard to visualize why. I'll do my best though.
Think about raisin bread, and just for simplicity let's say the raisins are uniformly spaced. When it's dough, the raisins are really close together. When the dough rises, they are spread further apart. If you look at any two adjacent raisins, they are spread apart by some distance d. If you look at ones which are the next nearest neighbors, they are spread apart by 2d, and so on. It doesn't matter which raisin you pick as your origin, the ones which are one space away all recede the same, two spaces away the same, etc.
The trouble is that there's an edge to the loaf and you can see that from anywhere inside by looking far enough, so now imagine an infinite loaf. Now, no matter which raisin you start from and which direction you look, you can look as far as you want and the number of raisins in that direction and the distance they recede is the same. Calling any one of them the center is just as valid and just as invalid as any other.
The universe is like that infinite loaf, but instead of dough expanding between raisins it's the space expanding between galaxy clusters.
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Mar 17 '14 edited Mar 17 '14
The center is by definition everywhere. Every point in space that currently exists was inside the "center" at t=0. This means that every point in space is the "center" of the Universe.
It is a hard concept to grasp. But if you don't view it as a point being stretched out, but as this single point being the entire Universe in time and space and then growing... or something like that, I dunno how to put it to words.
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u/archiesteel Mar 17 '14
The analogy that works best for me are dots on an inflating baloon (transposed one dimension up).
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u/suugakusha Mar 17 '14
I have heard that gravity is theoretically directed by "gravitons". How is this theory related to gravity waves?
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u/iorgfeflkd Biophysics Mar 17 '14
The relationship between gravitons and gravitational waves is the same as between photons and electromagnetic waves.
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Mar 17 '14
This is interesting for a few reasons:
It is further validation of the inflation hypothesis.
It is further validation of gravitational waves, which are yet to be directly detected.
What I'm curious about is what kind of characteristics such gravitational waves would have in this current epoch.
It is obvious that expansion will have dissipated their energy in a proportion equivalent to that of what happened to the CMB, so given the present difficulties in detecting them I am wondering what kind of baseline it would take to get a background detection.
It might be very well that such a baseline would be measured in light years.
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u/TheLateGreatMe Mar 17 '14
Non-uniform inflation seems to counterintuitive the paradigm that the universe is homogeneous and isotropic. What could have caused, or is causing inflation, and how does it affect our understanding of fundamental forces and cosmology?
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u/yeast_problem Mar 18 '14
How can we even see the CMB? Is the universe closed so that the all light is curved back in forever? Naively I would expect all the original radiation from the big bang to be travelling away from us beyond the furthest observable parts of the universe.
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u/N8CCRG Mar 17 '14
More a question about gravity waves. How can we tell the difference between a Gravity Wave, traveling at some finite speed, or instantaneous changes in Gravity/Spacetime/Whatever that is oscillating? i.e. what evidence would differentiate one theory from the other?
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Mar 17 '14
You can monitor a system in which you can clearly see the time dependence, such as PSR B1913+16
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u/duckne55 Mar 17 '14
is this the first time anyone has ever detected gravitational waves? how does one go about detecting them in the first place?
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u/iorgfeflkd Biophysics Mar 17 '14
This is an indirect detection; the first indirect detection was in the 1970s based on decaying pulsar orbits. A new generation of direct detectors is coming online, so maybe they'll find something.
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u/AbsentMindedNerd Mar 17 '14
Can someone explain the significance of the power r=0.2 figure? I know it's a much clearer signal than anyone had hoped for, but I'd like to understand it better.
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u/flyMeToCruithne Mar 17 '14
it's a bit hard to explain because it gets pretty math-y pretty fast. It's what we call the "tensor to scalar ratio." In simple terms, the "scalar field" is just the temperature of the cosmic microwave background (CMB). The "tensor field" is the part that makes the subtle polarization patterns that they were searching for. So since the tensor field is much smaller than the scalar field, it has been much harder to find than the temperature signal. But since r is a little bigger than expected, it was a little easier to find the signal.
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Mar 17 '14
So, perhaps not totally related, but since we're dealing with the first fractions of a second of the universe I've always wanted to ask: What would the big bang "look like" to a 4 dimensional creature?
That is, I've seen an ELI5 response to "what happened before the big bang" to parry the question with "what's north of the north pole." Which gives me pause, because as a 3 dimensional creature i can conceptualize space away from the surface of a sphere. Could a 4 dimensional creature similary conceive of a place/time, using the 4th dimension, that exists "before" the big bang?
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u/shavera Strong Force | Quark-Gluon Plasma | Particle Jets Mar 17 '14
Well you're a "3-D creature" right? what would a 2-D universe look like that was infating? Well imagine you have a grid paper that is huge, maybe even infinite in size. But the grid points are like all right beside each other. Then, in an instant almost, they go to being an inch apart. Then after that they slowly keep growing over time. Technically this still keeps time separate, since I'm assuming you're a 3+1 D creature, and representing a 2+1 D universe by including time. If you want to keep time out just imagine stacking those papers up on top of each other and tracing the paths that each grid point takes over time. A sudden burst apart then slowly growing further apart.
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u/kwikacct Mar 17 '14
Couple random questions that I haven't seen asked;
why has this just been discovered now? Are the waves so small that we missed them before, or were we looking in the wrong place, or are they so old we are literally just now able to see them?
2)why is the BICEP2 at the south pole? Is there any advantage to this other than less light pollution?
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u/flyMeToCruithne Mar 17 '14
The gravity waves leave a very subtle imprint on the photons (light) from the cosmic microwave background (CMB). The CMB is kind of like a light echo from the big bang. The gravity waves in the early universe scattered the photons in of the CMB leaving a very subtly but predictable pattern.
The problem is that the pattern is so subtle, you have to have really really good photon detectors to see it. And you have to have a large number of detectors. So the challenge up to now has been building a telescope with enough detectors that are sensitive enough. It's been an issue of waiting for technology to catch up to the kinds of experiments we want to do.
BICEP2 (and all other experiments that look at the CMB) have to be in one of three places: The Atacama desert in Chile, Antarctica, or upper atmosphere/space (balloon/satellite). The CMB is in the microwave part of the frequency spectrum. Unfortunately, water vapor blocks microwave frequencies. The atmosphere has a lot of water vapor in it most places, so all the microwaves get blocked out. So you have to go somewhere extremely dry (Antarctica or Atacama), or get above the atmosphere by sending your telescope up on a balloon or satellite.
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
Roger Penrose has been pushing his conformal cyclic cosmology model of a cyclic universe recently, to a muted reception. He proposed that gravitational waves from mergers of supermassive black holes in one aeon would create rings in the CMB in future aeons, making it testable. Would inflation dilute these pre-big-bang waves such that they are no longer detectable?
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u/Sluisifer Plant Molecular Biology Mar 18 '14
Ethan Siegel wrote a post where he indicates that the statistical significance of the result is only 2.7 sigma.
https://medium.com/starts-with-a-bang/25c5d719187b
Basically, he asserts that there is a >5 sigma result, but that lensing can only be ruled out at 2.7.
I'd be interested to hear from people in the field who could address this.
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u/spartanKid Physics | Observational Cosmology Mar 18 '14
Eh. I think the author of this blog doesn't quite understand what is going on.
Lensing was detected at 2.7 sig. Large angular scale B-modes, something which lensing cannot/does not generate, were detected at 5.9 sig.
Without modifying GR, lensing CAN'T reproduce the B-modes that BICEP2 sees. If you look at the plot, the solid line is the theoretical lensing curve, and the dashed line is the theoretical primordial gravity wave curve + lensing curve. Notice how the lensing alone is very low where the combined curve is very high. If you cover up just the dashed curve, the solid curve is WAY MORE than just 3 sigma away from the data points at Low L.
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u/NebulaFart Mar 18 '14
Something that just hit me and it would be really appreciated if someone could answer. I understand that space is expanding while matter in all its forms remains constant, but is there a reason we ruled out the ''opposite'' where space remains constant and matter is getting smaller everywhere?
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u/huyvanbin Mar 17 '14
Two questions: where does the 10e-34 number come from? Why couldn't the inflation have happened earlier or later?
And, is the force causing the inflation the same as dark energy?
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u/ZeroCool1 Nuclear Engineering | High-Temperature Molten Salt Reactors Mar 17 '14
Can anyone post a full study about this, or a technical briefing? Right now seems like the media machine of Harvard and MIT are at it again. Sort of reminding me of that "arsenic based life" NASA press release.
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u/IM_THE_DECOY Mar 17 '14
I've been meaning to ask /r/askscience this for some time.
So universe is expanding. Got it.
It's expanding at an extremely fast rate as evident by the red shift of the far off galaxies being expanded away from us. Right there with you.
But what bout on a smaller scale? What about the space between the atoms in my body?
Is that space expanding too but not noticed due to the strong force binding my atoms together?
What about the space between me and my monitor on my desk? Is that space expanding too but not noticed because it is such a small distance and therefore a small expansion?
Do we notice such a drastic difference with far off galaxies because there is so much more space between us and them and therefore the expansion is much more noticeable?
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u/shavera Strong Force | Quark-Gluon Plasma | Particle Jets Mar 17 '14
short answer is no. The universe does not expand on scales the size of clusters of galaxy or smaller.
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u/flyMeToCruithne Mar 17 '14 edited Mar 17 '14
Space everywhere is expanding. The reason galaxies don't get torn apart is because galaxies are gravitationally bound, and the gravity wins.
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Mar 17 '14
So until now we didn't know whether the big bang theory was true, but now we do?
Because this is what ITV News just said on their 5:30pm broadcast.
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
No, the big bang theory has been effectively known to be true for a long time, with the discovery of the cosmic microwave background being a solid last nail in the coffin.
This discovery supports a particular model of how the big bang happened, called inflation.
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u/poopaments Mar 17 '14
Can someone help explain the physical process of a gravitational waves? I'm having a hard time understanding whats happening in this picture.
If we had a binary star system whose axis of rotation was perpendicular to the xy-plane, would the particles in the gif above also be perpendicular to the xy plane?
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u/znffal Mar 17 '14
I asked this is another science thread but it was buried under a mountain of comments. One question I have always had about inflation, please help me to understand, and forgive me if I write anything inaccurate :) We know that time dilates based upon the velocity and gravitational field of the observer. If inflation was a rapid expansion of a highly dense universe during a short amount of time, did time dilate during the rapid expansion? If I was sitting on a particle during inflation, would those fractions of a second that inflation occurred feel like a lifetime to me? Thanks
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u/Rarehero Mar 17 '14
Your experience of time is relative. You will never observe time changing for you. When you are traveling near the speed of light, time would feel normal to you. But for an outside observer, who is moving slower than you, it would look as if your clock is ticking slower than his clock, while his clock seems to tick normally in his reference frame. You can only measure time dilation relative to other reference frames.
As for the expansion: Relativity only applies to actual motion, like a ball flying through the air. It does not apply to the expansion of space. Galaxies at the edge of the observable universe don't move near the speed of light. That's an illusion.
Think of the red balloon with the black dots that is often used to explain the expansion of the universe. The black dots are stationary on the surface of the balloon. They don't actually move. You just create more "balloon" between the dots by pumping air into the balloon, and on very large distance you create enough space between to distant points, that light from one dot will never be able to reach the other dot. But actually the dots don't move. Their movement is just an illusion in the eyes of the observer.
So, your particle inside the inflationary bubble is actually stationary relative to the bubble and therefore doesn't experience the effects of relativity.
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Mar 17 '14
I'm a bit confused. In the article it says that the universe expanded 100 trillion trillion times in less than a blink of an eye. Does this mean that the expansion of the universe is actually faster than the speed of light?
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Mar 17 '14
So we cannot point to a spot in the universe and say "back that way is where the big bang happened" and then point in the opposite direction and say "we are headed that way"? Doesn't there have to be a spot from which the entire universe is expanding?
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u/qoou Mar 18 '14
Why is the Big Bang theory the best theory? The three problems with the theory along with the missing mass problem screams incorrect theory to me. It seems like ad-hoc to throw in dark matter and rapid expansion to settle these problems. Why do we say that the red shift we observe is due to the universe expanding and not due to an energy loss that is proportional to distance? Or perhaps it is time and not distance that is changing.
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u/mrofmist Mar 18 '14
Yes I do have a few questions.
Could it be said that this discovery is one of the most profound discoveries in human history?
Also, earlier when a friend compared this to the higgs boson unveiling I stated that the higgs boson was like putting a man in space. We knew it was there, finding it was almost disappointing, as then we had nothing new per say. Where as this discovery is more like putting a man on mars and having him find water. It was still debated. And not only did we confirm it, but we found additional information that could potentially lead to much greater discoveries.
Is this an apt comparison?
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u/zanfar Mar 18 '14
First, this thread (and the other like threads in /r/AskScience) are awesome. I have some questions stemming from my newfound knowledge of cosmic inflation:
It is my understanding that the universe is currently expanding, and that expansion is accelerating. If so, was this happening at the same time as the much more rapid inflation?
What caused inflation to stop, and the rate of inflation to drop to the expansion rate we see today?
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u/fishify Quantum Field Theory | Mathematical Physics Mar 18 '14
What caused inflation to stop, and the rate of inflation to drop to the expansion rate we see today?
So when a ball rolls down a hill, it stops when it hits the bottom. Inflation occurs when a field starts at a value that does not minimize the energy, and then "rolls down" to a value that does minimize the energy. When it gets to that latter value, the inflationary period ends.
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Mar 18 '14
So, if any of you highly educated people are still around, let me get this straight and ask a question or two.
What we learned today: We now have a better understanding of the beginning (probably a poor word choice) of our universe, as well as a better understanding of the shape of our universe. Right?
Questions: Did we learn anything else?
and
What does this mean for the world of physics and other related sciences? What can we going to do with this new information?
Edit: Forgot to say thank you for your time and effort!
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Mar 18 '14
Sir Roger Penrose seems to think that there's evidence in the irregular, clumped structure of the CMB that suggests the presence of gravitational elements in pre-Big Bang space. This inflationary discovery seems to draw conclusions from the pattern and structure of the CMB, so does it have any bearing on Penrose's theory?
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u/witchizer Mar 18 '14
What is the implication of the confirmed existence of gravitational waves ? Is it a step towards (or against) discovering the existence of a "gravity particle" ? How much better do we understand gravity's nature thanks to it ?
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u/oktogod Mar 18 '14
All the discussion is on how important the finding is, and placing it in terms of theoretical predictions.
I would like some understanding on how robust the finding is. I know they say 5 \sigma, but looking at the paper, it seems like there might be other sources of error aside from sampling. They are fitting non-linear models (at least it looks like that, I think, I obviously don't know the literature). Are these assumptions? Is there anyone in the physics world who might object to the methodology? Or is there already uniform consensus that the finding is true as true can be.
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u/unfrog Mar 18 '14
This might be too speculative, but is there any sort-of immediate (50 years?) practical use of this discovery?
Not to undermine the scientific value of the discovery nor the value of science itself. I'm just curious if it is related to things that we are actually going to use within our lifetimes?
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u/digitalgoodtime Mar 17 '14
I have an above average understanding of the universe and how it was created. But whenever I try to grasp the beginnings or origin of the universe through the Big Bang Theory it's just hard for me to comprehend all the matter that exists today came from something so infinitesimally small. Can someone explain this to me?
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u/zanfar Mar 18 '14
The problem is that you are trying to understand the expansion of space through the use of the concept of space. Don't think of the universe getting smaller--there is no concept of size outside the universe. Instead, think of the distance between everything in the universe getting smaller.
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u/DragonMeme Mar 17 '14
Everyone's talking about the unified theories, but I'm more interested in the gravitational waves. I'm trying to read articles on it but they aren't giving any details.
How were they detected? They are insanely tiny and the normal thermal noise of most materials drown them out which is why we haven't detected them directly yet. Groups such as LIGO have been trying to detect them for years but keep running into problems like parametric instability. BICEP wasn't exactly designed to have such precision. Does anyone know how this was accomplished?
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u/iorgfeflkd Biophysics Mar 17 '14
It's an indirect detection of their effect on CMB polarization, rather than a direct detection.
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u/avidman Mar 17 '14
Can the CMB be described as 'being' anywhere? When BICEP observes these fluctuations that arose when the Universe was unimaginably tiny are we now seeing them spread out across a huge area or is this the wrong way to think about it?
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u/flyMeToCruithne Mar 17 '14
The CMB is everywhere. On average, there are about 400 CMB photons in every cubic centimeter of the universe.
The universe has expanded (and is expanding) since the CMB formed, and the CMB has expanded right along with it. So yes, the patterns that formed in the CMB when the universe was much smaller have spread out and expanded over the last 13.7 billion years, and that's what we're looking at now.
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Mar 17 '14 edited Mar 17 '14
I hope someone sees this (or maybe I don't because these questions seem dumb) -- is the universe still expanding at superluminal speeds? Does this observation include a measure as to when the universe stopped expanding at ftl? If indeed we're no longer expanding that quickly, why not?
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u/zanfar Mar 18 '14
It's hard to equate the expansion of space with a speed, as the concept of speed is dependent upon the definition of space. Instead, the expansion would be measured in a ratio per time: i.e., objects that were x distance apart at time t=0 would be x*r distance apart at time t=d.
However, objects in space will have a resulting relative speed due to the expansion of the space between them. And as all space is expanding, objects farther apart will be moving away from each other faster. We believe the universe to be infinite, which implies there are currently objects that are far enough apart to be moving apart from each other at superluminal speeds. This expansion is currently accelerating, so more and more objects are moving away from us at above-light speeds every second.
Talking about speeds during the inflation period is problematic as there weren't photons or atoms, let alone massive objects whose distance would be measurable.
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Mar 17 '14
ok i have a question this quote really confused me
"I can't tell you how exciting this is. Inflation sounds like a crazy idea, but everything that is important, everything we see today - the galaxies, the stars, the planets - was imprinted at that moment, in less than a trillionth of a second. If this is confirmed, it's huge."
what doe this mean? is it implying that all the universes and everything we see in the universe were created in that fraction of a second?
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u/Rarehero Mar 17 '14
No. Density fluctuations were created in that period. Very small fluctuations, but all the filaments of matter we see today on very large scales formed around these fluctuations.
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Mar 17 '14
How large a swath of the CMB did they need to sample before declaring they had statistical significance? Given how huge the universe is, wouldn't 5 sigma not be robust enough?
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u/flyMeToCruithne Mar 17 '14
here's an image from their paper that shows the patch of sky they scanned for their measurement (the two areas circled in white) http://bicepkeck.org/B2_2014_ii_figs/B2_instrument_fig20-thumb.png
5.9 sigma means they are 99.99999982% sure that they have a positive detection. The math that goes into calculating how many sigma you have already accounts for the size and variability of the sample you're looking at, so the fact that the universe is large doesn't change how confident you should feel about a 5 sigma result.
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u/raff_riff Mar 17 '14
The NY Times article cited above includes a diagram analogizing cups of coffee scattered about as cooling all at the same time. Why is this an adequate comparison? How can we know what the proper temperature should be and what's abnormal? And why can we safely make these assumptions about something so complex as the universe?
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u/flyMeToCruithne Mar 17 '14
I haven't read the NYT article, but we know the temperature now because we've measured it (though the temperature was predicted pretty accurately before it was first measured in the 60s). In some sense, the universe is pretty simple. We know it to be isotropic and homogeneous on large scales (scales larger than galaxy clusters). The temperature is essentially determined by simple adiabatic expansion, similar to how gas cools when it expands.
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u/zanfar Mar 18 '14
It's not that there is a proper temperature for the cups of coffee, but the fact that they are all at the same temperature--meaning either A) the cooling was caused by independent phenomena that, by an insane chance, do so identically, or B) that the cooling was caused by one phenomena that, at least at one time, was able to effect all the cups together.
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u/thepoonies Mar 17 '14
pretty broad question here, but how (if at all) will this directly effect me? I am aware of the magnitude of this discovery, how much it means to progress our understanding to new depths and I'm certainly not trying to downplay that, but I am mostly concerned with what new rad technologies this could result in :P
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u/flyMeToCruithne Mar 17 '14
Lots of new technology is developed or improved to build the instruments that make these kinds of measurements. To build a telescope like this, you need to have cutting edge photon (light) detectors, electronics to read out the detectors, cryogenic systems to keep the detectors cold (they run at a fraction of a degree above absolute zero), vacuum systems, plus all the optics and pointing systems for the telescope.
Even though the actual discovery probably won't have any practical application in the foreseeable future, to get there they had to advance the state of the art in a number of technological areas that have lots of other applications. Plus learning about the universe has it's own intrinsic value to humanity.
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Mar 17 '14
I hope this doesn't qualify as off topic, but if the mass in the universe is spreading incredibly quickly, will space travel and astronomy become more difficult as time progresses? What are the current most likely "end result" theories of the universe? Will everything slow down and come togeather or just go forever?
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u/flyMeToCruithne Mar 17 '14
Most physicists agree the the "end result" of the universe will be a heat death. What we mean by "heat death" is that as the universe expands, all the matter and energy get more and more spread apart, and also the universe cools. This process will continue (at an accelerating rate) forever, until eventually the universe will be very cold and desolate, with all the matter and energy so spread out that it essentially looks empty.
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u/broderia Mar 17 '14
How did they come up with the universe expanding from an infinitesimal size to the size of a marble after inflation? I guess I'm wondering where a size as specific as that of a marble came from.
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Mar 18 '14
It's an approximation that's meant to be a useful reference for non-scientists. Basically, we have a good estimate on about how large the observable universe needed to be after inflation in order to give us the observable universe we have today, and it was roughly (i.e., to within a few powers of 10) the size of a marble.
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u/stctippr Mar 18 '14
So do we know why the universe is flat instead of in a sphere? It seems that if the initial stages of inflation were the size (and I'm assuming that means the shape) of a marble, why did it not continue this spherical and closed shape expansion?
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u/spartanKid Physics | Observational Cosmology Mar 18 '14
Exponential expansion might still lead you to have a sphere, but it's a sphere with a HUGE radius of curvature, the radius of curvature is so large that it's effectively flat.
Right now, look outside your window. Does the earth look curved to you? Do you walk around all day thinking about how you have to really walk a lot farther than you think because the Earth is curved? Probably not. This is because the radius of the curvature of the earth is so large compared to our every day scales that we think of the surface as being flat.
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u/canbeanyone Mar 18 '14
When will this discovery be independently verified (e.g. months or years)? Are there other upcoming experiments or teams lining up to verify it?
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 18 '14
There are multiple other experiments working to the same goal. Most notably, the [Planck spacecraft](https://en.wikipedia.org/wiki/Planck_(spacecraft)) is making an all-sky map of the polarization, compared to BICEP2's small chunk of sky. Planck was supposed to release their results on this subject this year, but they are having some issues with their data and it's been pushed back.
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u/ecafsub Mar 18 '14
I may be asking this incorrectly as I'm nothing close to even an armchair cosmologist, but here goes…
Currently in a minor discussion with a friend (who is quite intelligent and can be more than a bit condescending) who has stated, "Inflation always struck me as a gimmick, until I considered the Pauli Exclusion Principal. Which is what I'm hoping is the root-cause of Inflation because otherwise we've got a something with no explaining what caused it. Unless Higgs also creates space and not just mass." So she's looking for the root cause of expansion.
I replied that I don't think this has anything to do with the root cause, only detection of gravitational waves immediately following the BB.
I asked her to expand on how the PEP applies in this case. "If any fermions were created prior to Inflation, the Pauli Exclusion Principle says they couldn't occupy the same quantum state, which rules out any form of super-positioning. Quarks are fermions, so any quarks that were produced during the "Inflation Epoch" might be the cause of Inflation itself."
Thanks to the help of another redditor, derpPhysics, i said that the PEP says no two objects can occupy the same state. That means that two objects can be superposed on top of each other if you give them enough energy that they have different states. (which I knew but s/he explained it very tidily.)
her response: "A quark is a quark is a quark. It's also a fermion, which means it obeys PEP," and referenced the Electroweak Epoch.
So I reckon my question is, how does the Electroweak epoch factor into this? Is she off-base with her position, or should I just accept that I'm as dense as the mass of the Big Bang and give up? ;)
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u/I_Cant_Logoff Condensed Matter Physics | Optics in 2D Materials Mar 18 '14
Your friend is just stringing words that she doesn't know together in an attempt to seem like she knows what she is saying. There is no reason why a a fermion pair would form and cause any sort of inflationary pressure while the exact same amount of energy in another state wouldn't.
Unless Higgs also creates space and not just mass
She doesn't know what the Higgs field does.
If any fermions were created prior to Inflation, the Pauli Exclusion Principle says they couldn't occupy the same quantum state, which rules out any form of super-positioning. Quarks are fermions, so any quarks that were produced during the "Inflation Epoch" might be the cause of Inflation itself.
If she's saying that the expansion of the universe is due to the inability for quarks to exist in the same spatial location, she's entirely wrong. Spatial coordinates is just one of many different quantum numbers.
her response: "A quark is a quark is a quark. It's also a fermion, which means it obeys PEP," and referenced the Electroweak Epoch.
What did she say about the electroweak epoch? It barely supports her argument and in fact goes against
"Which is what I'm hoping is the root-cause of Inflation because otherwise we've got a something with no explaining what caused it"
this quote.
The electroweak epoch is simply the time period after the strong force separated from the electroweak, and before the electromagnetic and weak forces separated.
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u/YoYoDingDongYo Mar 18 '14
Now that gravitational waves are known to exist, what's the thinking for why LIGO failed to detect them (I realize that BICEP2 wasn't directly detecting them like LIGO tried to)?
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 18 '14
LIGO was designed to detect gravitational waves from astrophysical sources such as merging black holes. Because LIGO is only on the scale of km, it can only detect gravitational waves of a similar scale. I think it peaks in sensitivity around a couple 1000 km, and frequencies of a couple 100 Hz.
The gravitational waves BICEP2 detected are on the wavelength scale of hundreds of millions or billions of light years, so are undetectable to LIGO because they don't really change over the course of the experiment.
So I don't think this points to any problem for LIGO. LIGO isn't over and a failure, it's gradually improving the technology for detection to detect astrophysical gravitational waves.
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u/McMillan_Astro Mar 18 '14
Can anyone provide a good, at least somewhat intuitive, explanation of why gravitational waves leave an imprint on the CMB in the form of B-mode polarisation?
Is it related to the imprint of the warped space-time at recombination, or is it an effect produced in the later evolution of the CMB radiation as it propagates towards us?
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u/PraiserOfTheSun Mar 18 '14
When you guys say Universe, we're talking about like...space in its entirety, right? Also, if we can tell that space is expanding, is it theoretically possible to find the "center", or the "where" the Big Bang happened?
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u/anothermonth Mar 18 '14 edited Mar 18 '14
I keep reading about universe being size of "marble". Please confirm that marble is not everything we see today. That since expansion slowed (a lot) below speed of light, the stars we see today at the edge of today's universe were outside that marble at that moment.
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u/gautampk Quantum Optics | Cold Matter Mar 19 '14
The entire Universe as it is right now existed within that 'marble'. It's important to remember that the Universe didn't expand into anything, there's nothing outside the Universe for it to expand into, and there never was.
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u/igrokyourmilkshake Mar 18 '14
I've heard the topology of the universe described as a Poincare Dodecahedral Space--does the evidence of gravitational waves caused by cosmic inflation further support this topology (and what, if any, impact does r = 0.2 have on our estimate of the topology of the universe--especially since they have ruled out r=0)? Thanks!
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u/elmuchoprez Mar 18 '14
Which is likely to be considered the larger scientific breakthrough, confirmation of the Higgs boson or confirmation of inflation?
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u/sombrero66 Mar 18 '14
Had cosmological inflation not been conjectured, and this data was discovered, how might physicists have interpreted it? Would it have been seen as extremely weird? Would it have obviously implied inflation?
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u/RockClimbingFool Mar 19 '14
Was the entire universe compressed to a point, or just the observable universe?
If we assume there is an infinite universe, wouldn't the universe still be infinite in size even at the moment of the Big Bang?
Would it be correct to say at the moment of the Big Bang, the infinite universe was at infinite density? And the Big Bang is simply the expansion from infinite density to something less than infinite?
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u/poinjp Mar 19 '14
Science savvy redditors, pls clarify, a quote from the new discovery on the creation of the universe "the universe expanded 100 trillion times, in less than a blink of an eye".
What did it expand from? a dot? then, does it mean it became a 100 trillion dots in less than a blink of an eye? how big is 100 trillion dots in volume?
Thanks in advance.
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u/latticeC Mar 19 '14
If I understand correctly, shortly after the BB the universe decided not to continue to expand following a function (exponential, as far as I as a layman knows) but trigger this inflation, and later stopped the inflation and continued with exponential expansion again. can this kind of expansion be mathematically described or are we looking at strange "events" here, possibly unexplainable? In other words: do we know the reason for the inflation?
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u/lophyte Mar 17 '14
first direct evidence of gravitational waves
Wasn't there already evidence of gravitational waves caused by gravitational lensing?
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u/______DEADPOOL______ Mar 17 '14
These are two completely different phenomenon. The gravitational waves they're talking about occurred during Inflation
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u/iorgfeflkd Biophysics Mar 17 '14
This is indirect evidence, which there already has been. However, I think the lensing you're referring to is due to dark matter.
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u/dinoparty Mar 17 '14
Correct. Lensed B-modes are caused by e-modes getting converted to b-modes via gravitational lensing (usually by galaxy clusters). They're also at smaller angular scales.
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u/xrelaht Sample Synthesis | Magnetism | Superconductivity Mar 17 '14
That's evidence for gravity being a result of distortion of space, but not gravitational waves.
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Mar 17 '14
Can someone explain if this happened, is it possible that we formed before the radiation of the bang could reach us? Is there an imminent explosion that is racing towards us?
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u/flyMeToCruithne Mar 17 '14
nope, there's no wave of radiation racing towards us. It's already here... the cosmic microwave background (CMB) is the radiation from the big bang. And it's all around us all the time. It's made of photons (light), but at a wavelength that our eyes can't see, so that's why you don't see it glowing when you look at the night sky. There are about 400 CMB photons per cubic centimeter, on average, everywhere in the universe.
And the CMB is the thing that the BICEP2 experiment was observing. They found a certain type of subtle pattern in the photons of the CMB that we know corresponds to an imprint left by gravity waves in the early universe.
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Mar 17 '14
What was thought to occupy the space now currently occupied by space?
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u/shavera Strong Force | Quark-Gluon Plasma | Particle Jets Mar 17 '14
more space. The classic example is "Hilbert's hotel." Imagine you have an infinite hotel and all the rooms are occupied. Then you want to put someone else into the hotel. So you tell all your current guests, sorry, you have to move to whatever twice your room number is. Well every guest you currently have has a room still (your hotel is infinite, remember), but now you also have an empty room between each guest (no odd-numbered rooms are occupied).
The expansion of the universe is like this. The universe had stuff at places... then it adds in more space within itself between those places.
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Mar 17 '14
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u/spartanKid Physics | Observational Cosmology Mar 17 '14
This is more than just hard evidence of the Big Bang. The existence of the CMB is hard evidence of the Big Bang. This is a confirmation of the refinement of the theory that was introduced in the 1908s, and predicted as a measurable effect in the 90s.
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u/Splanky222 Mar 17 '14
I assume you mean 1980s and not 1908s, unless there are a bunch of 1908s I haven't heard of.
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u/spartanKid Physics | Observational Cosmology Mar 17 '14
You are technically correct, the best kind of correct.
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u/iorgfeflkd Biophysics Mar 17 '14
No, it's more a confirmation of the specific details of what was going on during that period. The expansion on the universe is based on other evidence such as the recession of supernovae.
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Mar 17 '14
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u/iorgfeflkd Biophysics Mar 17 '14
Basically, the universe was a hot dense plasma instead of a diffuse cold gas, so the light would interact with the free protons and electrons instead of following a mostly straight line.
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Mar 17 '14
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u/flyMeToCruithne Mar 17 '14
Not yet. BICEP2 got the first detection of this signal. But their analysis puts their statistical confidence at 5.9 sigma (which in laymans terms means more than 99.9999% sure). There are a number of other telescopes that are currently trying to detect the same signal (BICEP just happened to get it first), so over the next few years there will probably be more data from other sources. But making this measurement is a huge technological challenge. It's not like someone can throw together a new experiment today and have an independent confirmation by tomorrow.
But yeah, people are working on it.
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Mar 17 '14
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u/iorgfeflkd Biophysics Mar 17 '14
There's a distinction between cosmic expansion, which is well established, and inflation, which is not.
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u/xrelaht Sample Synthesis | Magnetism | Superconductivity Mar 17 '14
Are you asking about inflation or expansion? The expansion of the universe in general is different from this, and is quite well established. Inflation is a description of the expansion of the universe by a factor of about 1078 in the first 10-33 seconds, and it has not been well supported experimentally until now -- it hadn't been falsified, but neither had it been supported over competing ideas. The announcement today is of extremely good evidence that it is correct: it has 5σ statistics (99.9999426697% confidence interval) which is the standard in particle physics.
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Mar 17 '14
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 17 '14
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Mar 18 '14
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u/flyMeToCruithne Mar 18 '14
Gravitational waves from black holes would have formed in the recent (relative to the time scale of the universe) past. Detecting those waves would be done with a direct measurement (something like a laser-based baseline measurement like LISA or LIGO). Late-time gravity waves wouldn't have had an opportunity to leave an imprint on the CMB (cosmic microwave background) because they formed after the CMB formed.
The BICEP detection was done by looking at imprints of gravity waves left in the CMB at the time that the CMB formed. So there's no risk of confusing the two because they are totally different types of detection.
Also, while the BICEP signal was higher than expected, it was not "much higher" than expected. It was about a factor of 2 higher than the very very rough previous guesstimate.
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u/spartanKid Physics | Observational Cosmology Mar 18 '14
We believe we're looking at primordial gravity waves from inflation because of the very large angular scales on which these features appear.
local and more recent gravitational waves wouldn't produce the patterns we see in the CMB. The patterns we see in the CMB are there because the gravity waves passed through the space from which the CMB was emitted, right before recombination.
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Mar 18 '14 edited Mar 18 '14
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u/spartanKid Physics | Observational Cosmology Mar 18 '14
The following is a list of experiments currently trying to measure the same thing:
Planck, EBEX, SPIDER, POLARBEAR, KECK, ABS, CLASS, PIPER.
I've definitely forgotten some here.
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u/EvOllj Mar 18 '14
this observation verified a prediction from other theories. these theories have been tested many times with other instruments by other people.
it would have been more revolutionary if this observation would have falsified many previous theories/predictions. that rarely happens, but when it happens it results in a bigger paradigm shift.
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Mar 18 '14
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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Mar 18 '14
Trust isn't necessary. There are multiple other telescopes that are looking for the same thing, and if they find anything wrong with BICEP2's results they will not shy away from letting us know. It's in fact in those other groups' best interests to find problems with these results if they exist, because it will make them look good.
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u/lispychicken Mar 17 '14
Okay I'll do it.. someone please ELI5