
Gravity waves from Big Bang detected - tjaerv
http://www.scientificamerican.com/article/gravity-waves-cmb-b-mode-polarization/
======
Tarrosion
As an outsider (PhD student in a quantitative field, no relation to physics),
the experimental physics community really strikes me as a class act. High
standards for statistical significance, vigorously working to rule out mundane
explanations before publishing data, outlining which statistical tests will be
performed _before_ data is collected...I'm a fan.

"In fact, the researchers were so startled to see such a blaring signal in the
data that they held off on publishing it for more than a year, looking for all
possible alternative explanations for the pattern they found." That's pretty
amazing; as far as I can tell, such caution is less typical in e.g. the brain
sciences.

~~~
tibbon
The popular media really like to grab any neuroscience paper and twist the
hell out of it. Talk to most neuroscientists and they are much more
conservative in their leaps and jumps... in reality its moving slowly, but the
media wants to portray a Ray Kurzweil reading of every finding.

~~~
dragonwriter
> The popular media really like to grab any neuroscience paper and twist the
> hell out of it.

This is true, but a specialized case of the equally true:

"The popular media really like to grab any science paper and twist the hell
out of it."

Which is just a specialized case of the also equally true:

"The popular media really like to grab anything and twist the hell out of it."

~~~
andrewflnr
I can believe, however, that neuroscience gets it worse, because it has more
obvious applications in the lives of readers/viewers etc.

------
DangerousPie
They made a nice video of the researcher surprising Prof Linde with the news:
[http://www.youtube.com/watch?v=ZlfIVEy_YOA](http://www.youtube.com/watch?v=ZlfIVEy_YOA)

The reaction of the couple is great!

~~~
cromwellian
I love the humility, skepticism of belief Linde professes at the end. Despite
a deep desire to believe in the beautiful, he is well aware of how you can be
seduced into believing things because you want to, not because the universe is
that way.﻿

~~~
LeoNatan25
This is what separates the scientists from ... others.

~~~
Balgair
We can only wish that is true, we are all just humans in the end:

[http://www.economist.com/news/briefing/21588057-scientists-t...](http://www.economist.com/news/briefing/21588057-scientists-
think-science-self-correcting-alarming-degree-it-not-trouble)

Also, I vaguely remember a study in 'some journal' that looked at all it's P
values[0] and found an alarming number of them parked right at the limit of
acceptance (.05), more so than chance could assume. If anyone remembers this
study and can provide actual proof (not my terrible memory), I would be very
thankful.

[0][https://en.wikipedia.org/wiki/P-value](https://en.wikipedia.org/wiki/P-value)

~~~
betenoire
I don't think he's commenting on statistical analysis, but rather saying that
a scientist should follow the clues where ever it may take them, instead of
looking for the clues that will get them where they want to be. And of course
they fuck up, too.

------
swatkat
Guardian has a nice and simple article explaining gravity, gravitational wave,
and about this detection:

[http://www.theguardian.com/science/2014/mar/17/gravitational...](http://www.theguardian.com/science/2014/mar/17/gravitational-
waves-bicep-inflation-big-bang)

------
wozniacki
Here's an excellent explanation on cosmic inflation from Sean Carroll:

[http://www.preposterousuniverse.com/blog/2014/03/16/gravitat...](http://www.preposterousuniverse.com/blog/2014/03/16/gravitational-
waves-in-the-cosmic-microwave-background/)

~~~
mcguire
...which seems to be unreachable for me at the moment. I'll have to check it
out later. In the mean time....

Cosmic inflation has always bothered me. I just don't get it. I'm not a
physicist at all, though. I get _why_ it's postulated. (The uniformity of the
universe requires it to all be in close proximity and the time scales don't
have enough time for that part, IIUC.)

But the expansion of inflation is significantly faster than the speed of
light. What's up with that? I know, spacetime is expanding rather than things
moving within spacetime, but still, during inflation, this particle _here_ is
watching that particle _there_ recede at >> C. I doan geddit.

( _Grump._ )

~~~
GeneralMayhem
The way I understand it is that the problem is with the definition of
velocity. If you want to measure speed, you have to measure distance, which
eventually comes down to the magnitude of the vector between two points -
subtract the X's, subtract the Y's, subtract the Z's. Problem is, at cosmic
scales, expansion means that those two points aren't in the same reference
frame, because more space has appeared between them. You can try to measure
it, but by the time you do the axes themselves have stretched again. The two
X's can't be subtracted directly anymore, because they're on different
reference frames. You get a result of >>C only by assuming that the relevant
bits of space are relatively well-behaved Euclidean R^3, but that's not the
case.

------
slacka
So just to clarify, this is only the measurement of an artifact most likely
caused by gravity waves during the period of inflation. We still have not
directly measured gravity waves in our current universe, right? I think the
fact that gravity can't be measured is a subtle clue about one piece of the
puzzle for a unifying theory of everything.

~~~
andrelaszlo
I find this concept of "directly measuring" things confusing. My theoretical
knowledge is very weak though, maybe someone can explain.

It seems to me like we never measure things _directly_. For example: To
measure the temperature of something in everyday life, we use a tiny glass
cylinder filled with some kind of liquid. The liquid expands or contracts,
roughly linearly, because of the temperature exchange with its surroundings.
We then compare the current level of the liquid to a little ruler inscribed in
the cylinder, maybe the markings form a shape similar to "100°C". The photons
that bounce off this little ruler into our eyes causes impulses in some
neurons and so on and our brains compare the shape "100°C" to yet another
reference point, boiling water. It's hardly direct¤, in any sense of the word.

If we measure gravitational waves by observing "ripples in background
radiation"¤¤, isn't that kind of the same thing? I've seen several people here
mention that it's not "measured directly" \- does it mean something else in
this case?

¤ If you stick your hand into the boiling water to measure its temperature,
it's a bit more direct but not as accurate.

¤¤ I'm just a programmer, this is kind of how I understood it. :D

~~~
jessriedel
There's a good philosophy of science argument to be made that there's no
_precise_ and _discrete_ distinction between direct and indirect measurement.
In our model of the universe, there are always multiple physical steps that
link the phenomena under investigation to our conscious perception. Therefore,
any conclusions we draw from a perception are conditional on our confidence in
the entire causal chain performing reliably (e.g. a gravitational wave induces
a B-mode in the CMB, which propagates as a photon to our detectors, which
heats up a transition-edge sensor, which increases the resistivity of the
circuit, which flips a bit in the flash memory, which is read out to a
monitor, which emits photons to our eye, which change the nerves firing in our
brain). "Direct" measurements, then, are just ones that rely on a _small
number_ of _reliable_ inferences, while "indirect" measurements rely on a
_large number_ of _less reliable_ inferences.

Nonetheless, in practice there is a rather clear distinction which declares
"direct" measurements to be those that take place _locally_ (in space) using
_well-characterized_ equipment that we can (importantly) _manipulate_ , and
which is conditional only on physical laws which are very strongly
established. All other measurements are called "indirect", generally because
they are observational (i.e. no manipulation of the experimental parameters),
are conditional on tenuous ideas (i.e. naturalness arguments as indirect
evidence for supersymmetry), and/or involve intermediary systems that are not
well understood (e.g. galactic dynamics).

The classic example is dark matter detection. A detector built in your
laboratory that produces clear evidence of a local interaction between the
dark matter partice and the atoms composing the detector would be "direct
detection". Seeing an anomalous excess of gamma rays from the center of the
galaxy whose energy and distribution is consistent with some theories which
predict dark matter annihilation would be "indirect detection".

Naturally, direct measurements have a much larger impact on your Bayesian
credences than indirect ones. If someone says "I don't trust that indirect
measurement" they mean "one or more steps in the inference chain which
connects the phenomena to our perceptions is unreliable".

EDIT: Oh, it's worth replying more directly (ha!) to your comment by noting
that both pulsar slow downs

[https://en.wikipedia.org/wiki/Gravitational_wave#Using_pulsa...](https://en.wikipedia.org/wiki/Gravitational_wave#Using_pulsar_timing_arrays)

and the CMB measurements by BICEPS are indisputably indirect. Gravitational
wave detectors

[https://en.wikipedia.org/wiki/Gravitational_wave_detector](https://en.wikipedia.org/wiki/Gravitational_wave_detector)

like the LISA proposal

[https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...](https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna)

are direct.

------
sanxiyn
From the horse's mouth: [http://bicepkeck.org/](http://bicepkeck.org/)

------
sixothree
Nothing bugs me more than when a supposedly scientific magazine uses
thumbnails of important images without actually linking to the full size. I
just wanted to see the black lines in the image the article refers to.

~~~
d0mine
Google search by image
[http://www.google.com/insidesearch/features/images/searchbyi...](http://www.google.com/insidesearch/features/images/searchbyimage.html)
returns
[http://bicep.rc.fas.harvard.edu/bicep1_3yr/](http://bicep.rc.fas.harvard.edu/bicep1_3yr/)

------
yukichan
> The finding is direct proof of the theory of inflation, the idea that the
> universe expanded extremely quickly in the first fraction of a second after
> it was born.

Small nitpick, but wouldn't the use of the words "evidence for" instead of
"proof of" have been better? Not that I am in any way trying to take anything
away from the discovery. Just from a science perspective, the word "proof" has
always bugged me.

~~~
kremlin
It's kinda a pet peeve of mine as well, having to switch between 'proof'
meaning a conclusion that logically necessarily follow from premises, to proof
meaning "really strong evidence".

But, as harshreality was getting at, if we used 'proof' that strictly, nothing
outside of pure math and logic would be a 'proof'.

~~~
wfn
> But, as harshreality was getting at, if we used 'proof' that strictly,
> nothing outside of pure math and logic would be a 'proof'.

True that. But isn't that an important part of the scientific method (at least
in the karl-popper-scientific-method sense), and part of the point of science,
really? Strictly speaking, you can't prove anything using the scientific
method; only 'falsify' it (hence Popper's 'falsificationism', 'science as
falsification', etc.) To 'kinda-sorta-prove' something in science, you
formulate a null hypothesis, and then attempt to falsify it. But strictly
speaking, one is not able to 'prove' anything (only provide weak/strong
evidence for/against something.)

------
piratebroadcast
I'm very curious of how, if we now presume this to be true, if and how that
may effect the "Are we living in a simulation?" question.

~~~
benched
I think there exist potential implementations of virtualization that are not
detectable from inside the virtualization.

~~~
eru
Especially if you are willing to sacrifice speed.

------
sosuke
Is gravity a wave then, like light? I thought the jury was still out on that.

~~~
miralabs
Light is both a particle and a wave

~~~
gnaritas
Or, light is neither a particle nor a wave, but a distinct thing that seems to
behave like both under various circumstances.

~~~
lnanek2
There are some cases in quantum mechanics where you just have to accept that a
value can be two different things at once, not that is was really one thing.
Like it or not, superposition is a real thing, so it is inarguable that
assuming something has to have one value at any one time is wrong.

Wave-particle duality is a lot like that as well, where it is tough to come up
with some distinct thing that could possibly act like a particle, but still
diffract like a wave.

~~~
Double_Cast
> _where it is tough to come up with some distinct thing that could possibly
> act like a particle, but still diffract like a wave._

Armchairing here. But as I understood, objects in quantum-land are known as
"amplitudes in the complex plane". They behave like this all the time and
under all circumstances, and should be understood on their own terms. E.g.
squaring the height of pond ripples doesn't return a probability distribution.
The "sometimes it's a wave, but other times it's a particle" idea is a
historical artifact, like how humanity uses a base ten number system.

------
AnimalMuppet
> This pattern, basically a curling in the polarization, or orientation, of
> the light, can be created only by gravitational waves produced by inflation.

I call BS. "Within our current theories, this pattern can be created only
by..." would be a more accurate statement. The arrogance that "with this
theory, we understand it all" has been shot down over and over in the history
of science.

[Edit: tarrosion noted the caution of experimenters in making sure that the
data could not be caused by something else. This is appropriate, and it's good
that they have it. You now have one, and only one, theoretical explanation for
the data. But the statement in the article that I quoted is still a step too
far. It presumes that our existing theories are the only possible ones.]

~~~
carbocation
Usually publications are understood within the context of their field. It
would be exhausting to list each limitation of your field in every paper, and
the limitations are understood by the intended audience.

~~~
mcguire
A friend-of-a-friend has the "science religion"\---he seems to try to claim
that what we "know" now is the closest to absolute truth that we could
possibly get, and would therefore make the claim from the article with a
straight face. (He seems unfazed by comments that some new discovery tomorrow
might invalidate what we "know" now and seems to think that what we would
learn would simply be more absolutely true.)

Me, I'm of the opposite philosophy and understand that everything I think I
know now is probably wrong. It's just slightly not-as-wrong as last week.

~~~
Locke1689
On the whole of it, your friend is probably more correct than you are:

[http://chem.tufts.edu/answersinscience/relativityofwrong.htm](http://chem.tufts.edu/answersinscience/relativityofwrong.htm)

~~~
acqq
As an illustration, around 2200 years ago, 200 years before Jesus, a Greek
scientist actually _measured_ the curvature of Earth not moving from his
town(!) only by observing the shadow of the Sun and cleverly thinking, giving
the circumference as "50 times distance between Alexandria and Siena." He
didn't have the exact distance then, but knowing that distance today, he
measured the circumference of the Earth with the error of less than 0.2%.

[http://todaslascosasdeanthony.com/2012/07/03/eratosthenes-
ea...](http://todaslascosasdeanthony.com/2012/07/03/eratosthenes-earth-
circumference/)

150 years later, still before Jesus, another scientist, Posidonius, repeated
the experiment.

Most of the things we confirmed today survived a lot of checks. As Asimov
writes it's not that there's much "wrong" in what science knows today, it just
that is "incomplete" in the smaller (from the perspective of the common
experience) details.

~~~
mcguire
The difference to me is that "incomplete" means you are missing something:
more precise measurements, better calculations, more information. But that is
not necessarily the case. You may be able to measure the size of the Earth
relatively precisely, but if your theory puts that Earth at the center of the
universe, more measurements are going to do little but cause you headaches.

Take the ever-popular conflict between relativity and quantum mechanics. For
all intensive purposes [sic], I believe they both work out to about Newtonian
mechanics at scales I can easily observe and they both work very well for
their different appropriate tasks. But they don't mesh well together, which is
another requirement for science. "Incomplete" doesn't begin to describe that
situation because I suspect that whatever is going to unify both is going to
be as different from either as they are from classical physics.

[As an aside, I've seen Asimov's essay before and while I usually don't have a
problem with his writing, in this essay's case I can't get past the fact that
it is either very poorly written (if I'm feeling charitable) or a rather silly
ad hominem (if I'm not).]

~~~
acqq
My example is totally orthogonal to the subject of the position of the Earth
in the universe, I don't understand what can benefit from bringing the
confusion in the discussion.

Your other argument is what scientists are well aware of for decades, so it's
a good example of the science knowing its current limits, which again means
_we can 't be wrong_ if we know the exact limits. We have unmapped terrains
that span only first 1e−32 part of the first second! Can you even imagine how
small that time is? There were 1e49 such time intervals since then! What's
that when not a small "incompleteness" of our knowledge. That people who work
on that call it "a big thing to unify" doesn't change the fact that it's
something small to the vastness of the time we already cover with the present
equations.

------
encoderer
Reminds me of the way Einstein, not being an experimental physicist himself,
would conclude his famous papers with suggestions for experiments to confirm
them. Awesome for this research team to have the opportunity to confirm this
discovery in Linde's lifetime.

------
estebanrules
How would you folks rate the significance of this, let's say as far as
scientific discoveries / realizations go in the last 100 years? Yes, of course
this is completely subjective. I would say in the top three.

~~~
sanxiyn
Assuming it's real, I think it's up there with T ~ 3 K (cosmic microwave
background itself, Nobel 1978) and Λ > 0 (accelerating universe, Nobel 2011).

------
Hypx
A little bit of caution from here:
[http://profmattstrassler.com/2014/03/17/bicep2-new-
evidence-...](http://profmattstrassler.com/2014/03/17/bicep2-new-evidence-of-
cosmic-inflation/)

Very interesting result, potentially game-changing, but it also could be
nothing too. Wait for more experiments before we can say for sure.

~~~
trhway
interesting that BICEP2 polarization from gravitation waves as they describe
it [http://bicepkeck.org/faq.html](http://bicepkeck.org/faq.html):

"strong B-mode polarization at the much larger angular scales--2 to 4 degrees
on the sky--where lensing is a tiny effect but where inflationary
gravitational waves are expected to peak. "

is of about the same scale as 500 million light years period of Baryon
acoustic oscillations period (ie. baryonic (gravitating) matter density
period):

[http://en.wikipedia.org/wiki/Baryon_acoustic_oscillations#BA...](http://en.wikipedia.org/wiki/Baryon_acoustic_oscillations#BAO_Signal_in_the_Sloan_Digital_Sky_Survey)

------
yeukhon
Is this the same as graviton in string theory? Or could this be used to
further justify the existence of graviton?

~~~
acjohnson55
I'm not a physicist, but I would think the answer has to be yes, since
everything we know of with wave nature also has particle nature on some scale.
But I can't even imagine what kind of experiment would detect one.

Wikipedia has some interesting things to say about this:
[http://en.wikipedia.org/wiki/Graviton#Experimental_observati...](http://en.wikipedia.org/wiki/Graviton#Experimental_observation)

------
cellover
This page allowed me to have an idea of the concepts underlying this discovery
(CMB light, B-mode polarization):
[http://cosmology.berkeley.edu/~yuki/CMBpol/CMBpol.htm](http://cosmology.berkeley.edu/~yuki/CMBpol/CMBpol.htm)

------
platz
Interesting that they succeeded in detecting gravity waves where LIGO failed?

~~~
sanxiyn
They are using a different method. In their own words: "The presence of a
water wave can be detected by feeling its up-and-down motion or by taking a
picture of it. We are doing the latter." LIGO is doing the former.

[http://bicepkeck.org/faq.html](http://bicepkeck.org/faq.html)

------
snickell
Is there a way from this data to calculate the frequency of the wave(s)?
Bandwidth? Or otherwise characterize the signal that is causing the
polarization? Is that even a meaningful question in this case?

~~~
lutusp
Not really. What's being observed are remnant polarizations from gravitational
waves that had their effect long ago, under very different circumstances and
mass-energy densities.

What's interesting is that the present measurements can be interpreted as
evidence for gravitational waves to the exclusion of other explanations to a
high degree of certainty.

Until now, evidence for gravitational waves was rather indirect and
circumstantial, for example orbiting pulsars (very dense collapsed stars that
emit periodic radio pulses) were observed to slow their pulse repetition rate
over time in a way that suggested they were losing potential energy by
radiating gravitational waves. Unfortunately those waves could not be detected
directly.

In principle, a gravity wave could have nearly any frequency/wavelength
consistent with its source. The pulsars discussed above were thought to
produce gravitational waves of relatively high frequency / short wavelength,
proportional to their pulse repetition rates. A so-called "millisecond pulsar"
would have a possible gravitational wave frequency of one kilohertz and a
wavelength of 3 x 10^8 / f meters or 3,000,000 meters (3,000 kilometers).
That's hardly short compared to a radio broadcasting station's wavelength, but
for gravitational waves, it's remarkable.

------
watson
Another HN post from earlier today about the same discovery:
[https://news.ycombinator.com/item?id=7411341](https://news.ycombinator.com/item?id=7411341)

------
philip1209
They have evidence of gravity waves, but cannot prove causation (i.e. big
bang), right?

~~~
marcosdumay
We already have overhealming evidence of the Big Bang, this is yet more
evidence. But we have only a relatively small amount of evidence of Inflation
and gravitational waves, and this is evidence of both (even better, it's
evidence against several theories of Inflation - including the current
prefered ones).

Correlations are evidence of causation, and quite strong evidence if you foud
them because of a causal theory.

~~~
npizzolato
As someone who doesn't have a very good grasp of these things, can you explain
the difference between the Big Bang and inflation to me? It seems like the Big
Bang is the explosion of all matter that would be in our universe, and
inflation is the rapid expansion of the universe itself. And inflation is
believed to have taken place almost immediately after the Big Bang. Is that
sort of accurate?

~~~
wbhart
The Big Bang theory is not about the "explosion" of our universe from a point.

Firstly, the universe may have always been infinite in size. It's just that
every small piece of that infinite universe has been expanding since about 14
billion years ago.

Secondly, "explosion" is a misnomer. The universe is expanding, not exploding.

As a theory, the Big Bang theory makes various predictions, such as the cosmic
microwave background radiation, the relative abundance of elements in the
universe and of course the expansion of the universe.

But it doesn't predict that the universe will be the same in all directions.
There just isn't time for energy fluctuations to have evened themselves out
due to the transfer of energy from hot spots to cold spots. That process can
only happen at the speed of light (energy is transferred at the speed of
light).

Because of the way space is expanding, the speed two points move away from
each other depends on how far apart they are. Thus, very distant points on
opposite sides of the sky are actually moving apart faster than the speed of
light. What this implies is that there's no way they can have had time to
reach thermal equilibrium (i.e. have reached the same temperature)!

But satellite observations tell us the observable universe is very nearly the
same temperature in every direction!

The problem is resolved by the Theory of Inflation. This is a time of
exceedingly(!!) rapid expansion which occurred before the time described by
the Big Bang theory (remember the Big Bang theory is not about the "explosion"
of the universe from a point, but about the subsequent expansion of the
universe _after_ inflation).

The reason inflation solves the problem is that a very, very tiny region of
space (subatomic scale) expanded exceedingly rapidly in a tiny fraction of a
second, smoothing out any temperature fluctuations. What we see as our
observable universe is just the temperature fluctuations in a subatomic sized
piece of universe from before inflation happened.

After that tiny fraction of a second, inflation stopped, and normal Big Bang
physics took over.

Moreover, inflation explains the formation of galaxies. Tiny quantum
fluctuations became the seeds of galaxies, clusters, superclusters and giant
strings of clusters that make up our universe today.

Note that almost everything written in the current Slashdot summary of the
breakthrough is completely wrong!

------
OOvsuOO
Wow.. that's sweet but really come on only supporting mavericks OS. And
already.. if you have a iPad the notes app automatically synchronizes with the
mail server (I use web based email service mostly.) I didn't even set it up or
should I say allow the iPad to do so.

~~~
splawn
Gravity waves work fine for me under ubuntu.

------
3327
Just 5 sigma confidence...

------
namelezz
Congratulation!

------
kimonos
Interesting info! Thanks for sharing!

------
notastartup
can someone explain the significance of this, for those that are not familiar
with this area?

