Gravitational Waves???

[Dave2042]

Big news apparently due to be announced Monday (currently just a well-circulated rumor).

The good people at the Harvard Smithsonian Center for Astrophysics seem to have detected primordial gravitational waves from the big bang.

(This is not quite the same thing as direct detection via the LIGO detector www.ligo.caltech.edu, but still very exciting.)

Here's the Guardian's take on it.

http://www.theguardian.com/science/2014/mar/14/gravitational-waves-big-bang-universe-bicep

[Astro_Bot]

That is pretty interesting and amazing if it's true.

Thanks for posting.

[SkyViking]

That would be fantastic, looking forward to the announcement!

[mr bruess]

Gravitational Waves are extremely difficult to detect.They are one of the last or final predictions of Einsteins theory to be confirmed.
All experiments to date have failed to detect it.

[madbadgalaxyman]

I still remain unconvinced about the idea that reliable information about the nature of the universe can be obtained, in the sense of "information very likely to be true", from the analysis of the microwave background which is said to be a relic of the big bang.

If you observe a pattern in the background radiation and then you come up with a model to account for it; why not come up with another model which accounts for the radiation, or another one, or another one....(and so on, and so on, till you have created a billion different models, all of them equally likely to be true)
As we know, theorists are very good at coming up with multiple models, all of which they swear are true.
Only problem is, observations usually disprove most of them.

Could the study of the distribution and polarization of the microwave background radiation be a bit like gazing at the clouds and seeing patterns in them?
Yeah, we observe patterns, but can we really interpret them and say what they imply about the cosmos?

We have plenty of "cosmology fanatics" in IIS....so I would like to know if they think that the current interpretations of the microwave background are mere hypotheses which could easily be disproven when further facts come to light?!?

Cosmologists seem to be people who adopt the manner and tone of "true believers"; why do they seem to be unable to adopt a skeptical tone in relation to their theories?

[sjastro]

Hello Robert,



On the contrary the patterns in the CMB were theoretical predictions. So rather the model being built up around existing observation, the model predicted structures that were later supported by observation.

A case in point is the B-mode polarization (http://physicsworld.com/cws/article/news/2013/jul/25/b-mode-polarization-spotted-in-cosmic-microwave-background) discovered in the CMB last year.
The B-mode polarization is caused by both gravitational waves and gravitational lensing hence there is indirect evidence of primordial gravitational waves even prior to the latest information.

We now have two separate tests that may point to the existence of gravitational waves.

The case for gravitational waves is falling nicely into place.
Primordial gravitational waves are a prediction of combining curved space into Quantum mechanics, primordial gravitational waves were predicted to create structures in the CMB and finally technologies were developed to put the theory to the test.



Newton's theory of gravity wasn't disproven because it couldn't explain Mercury's orbit, a feature that is accounted for in General Relativity. It means that Newton's theory is incomplete.
Mainstream scientific theories fall into that category, theories never become truths or facts. As technologies improve as new tests are developed or existing tests are performed at greater precision, we may find the existing theory to be more incomplete instead of being wrong.
There are no viable theoretical alternatives, plasma cosmology cannot explain the CMB structures. Many alternative explanations are so bizarre they fall into the category of pseudoscience or conspiracy theories.
For example one theory suggests the CMB is nothing more than microwave radiation emitted from the Earth's oceans. The trouble with this theory is the Earth's atmosphere is largely opaque to most microwave radiation, in fact the most common frequency in the CMB should be completely blocked off by the atmosphere!
Another theory suggests a faulty antenna design in which case the CMB is nothing more but noise. Unfortunately for this there have been two separate American and one European probe each with ever improving technologies for background detection.



I'm sure on a personal level some cosmologists might have this attitude as would some microbiologists, particles physicists, palaeontologists or from any scientific discipline.
I doubt however its an exclusive province amongst cosmologists.

Regards

Steven

[xelasnave]

Hi everyone
I often feel like Robert I confess.
But I see what Steven suggests. One must present a possitive outlook on your projects chance of coming off with a big payoff. A gravity wave is ripple in space time I think does it mean the gravity constant changes as the wave passes. Any ideas as to what is happening at a quantum level a serge of gravitons for example.
Alex

[nebulosity.]

Very true what you are saying, and I'm glad to see that some other people are realising this as well, see here... (http://www.cosmologystatement.org/)

[mr bruess]

Newton's theory of gravity assumed that space and time were fixed or absolute and that gravity was a force.Einstein showed that space and time were not absolute and that it can be distorted in the presence of a massive body like the earth and sun.
Einstein identified the property of spacetime which is responsible for gravity is its curvature. Space and time in Einstein's universe are no longer flat (as implicitly assumed by Newton) but can pushed and pulled, stretched and warped by matter. Gravity feels strongest where spacetime is most curved, and it vanishes where spacetime is flat. This is the core of Einstein's theory of general relativity, which is often summed up in words as follows: "matter tells spacetime how to curve, and curved spacetime tells matter how to move"

[sjastro]

Alex,

Generally the properties of space time are static and time constant. The curvature of space time for example will not change. However GR predicts that changes in space time will create gravitational waves.
Examples when space time is non static are the gravitational collapse of non spherical bodies or the decaying orbit of two massive bodies orbiting around a barycentre.

Primordial gravitational waves are somewhat different. They are believed to be a direct consequence of inflation. Inflation is caused by the transition of the Universe from a higher to lower vacuum state. Scientists found that vacuum fluctuations during inflation would result in space time being non static.
Hence the search for primordial gravitational waves becomes a test for inflation.

This is a rare example where GR and Quantum field theory work in "harmony".

Regards

Steven

[sjastro]

This "statement" crops up frequently on crackpot sites, is misleading and technically inaccurate about the Big Bang.

Sean Carroll (http://preposterousuniverse.blogspot.com.a u/2004/05/doubt-and-dissent-are-not-tolerated.html) gives an accurate account of the letter.

Regards

Steven

[nebulosity.]

"Crackpot" "Misleading" "Technically inaccurate" "Religious"... just because it doesn't support the big bang!

Isn't this exactly what Robert it talking about?



Anyway, such is life. Will be interesting to see what they come up with :lol:

[xelasnave]

Thanks Steven exellent explanation. Thanks.
Alex

[Dave2042]

Hi Robert.

While I think Steven's responses generally cover my feelings on this, I'd add one more point.

I think a lot of what people see of cosmology/astrophysics from the 'outside' (including fairly knowledgeable amateurs) is more a reflection of what science journalists think will generate clicks or sell paper than what is actually going on in the field. I also think that sometimes it is driven by journalists' misunderstandings.

My recollection of my brief time on the 'inside' is that most day-to-day activity is actually spent doing fairly mundane work which serves the important but unexciting purpose of confirming and incrementally advancing our understanding of things within the existing accepted framework of our theories.

Of course, scientists take time out from this to speculate about wilder possibilities, since this:


keeps one's mind open;
can throw an interesting light on the standard stuff;
might turn out to produce the Next Big Thing (and a Nobel prize); and
is fun.

Unfortunately there seems to be a tendency for this stuff to be grabbed hold of in the press and presented as if it were representative of the mainstream activity in the field, which it's not.



A good recent example was Hawkings recent pre-print on black holes. This was a fairly high-level musing on some of the problems of applying quantum mechanics to black holes, and floated the idea that the event horizon might not be the sharply-defined impermeable barrier that is implied in GR. To put it in context:


the paper was not peer-reviewed;
Hawking acknowledged that a proper resolution of the matter would require a reconciliation of GR and QM, which still looks a long way off;
the general macroscopic behaviour of a black hole would not be changed from our current picture, only some very specific long-term and extreme behaviour; and
The paper was very clearly off the mainstream and speculative, and did not seem to present itself as otherwise.

But this wound up in the press as 'Hawking proves black holes don't exist'.


As far as I can tell, most GR research is devoted to:


Trying to build ever more sensitive detectors in the hope of directly detecting gravitational waves;
developing better mathematical techniques for solving the field equations; and
Making lots of observations to collect relevant data; and
Seeing how the data fits our theories and models.

but this is all a bit too dull to write stories about.

[sjastro]

"Crackpot", "Misleading", "Technically inaccurate" is exactly what the statement is.
The critique of the Big Bang Theory is based on strawman arguments rather than facts.

The very first sentence highlights this.



The effects of dark matter and dark energy are observed through the
rotation curves of galaxies, the escape velocity of individual galaxies in clusters and type Ia supernova standard candles for calculating distances respectively. Now we have the possibility that primordial gravitational waves are the observed effects of inflation.

As to the causes of inflation, dark matter and dark energy, this takes it out of the field of cosmology into particle physics.

Then there is this pearler.....



So much for what has been stated so far in this thread..........

Regards

Steven

[xelasnave]

I agree with Dave as to laymen getting a corrupted view due to media sensationalism. I cringe at headlines about black holes being the gateway to time travel for an example. However scientists are complicite else something would have been done to correct.... sensationalism cant be bad as it may even help funding prospects.
I dont like the big bang because I believe it is a religious concept..it accounts for creation...opps sorry it accounts for what happened after the first split second of time. I dont like the assumption that expansion can be reverse ectrapolated such that we arrive at a point of infinite density. I dont like the concept of inflation becausr I can not believe space can grow from zip to all there is in such a short time. But what I think is irrelevent
Thats not a problem.Being called a crack pot has never worried me. I see a theory like a boat if it floats it is a boat and any repairs still leaves it a boat. Until it sinks it rrmains s boat and its sinking will not erase the many days it sailed without sinking..Big bamg is similar ..it floats it may need repair but at the present it seems to work very well. Inflation was introduced to solve a big bang problem buI wpulf like to ser a big bang model with a different solution.
If we cant find any signature for inflation can we scrape it and get a step more believable.

[xelasnave]

Sorry for the mistakes I am using my phone and it is a pain to use and editing more so..My point is if no gravity waves will inflation be rejected
Alex

[Dave2042]

Here it is.

http://www.cfa.harvard.edu/news/2014-05

[sjastro]

It is being hailed as one of the greatest scientific discoveries in history.

Perhaps it's a bit premature.
The next step is for the POLARBEAR (http://physicalsciences.ucsd.edu/news/2012/polarbear.html) scope in Chile to confirm the discovery.
Also polarized images of the CMB from the Planck satellite will come in October.

Regards

Steven

[avandonk]

I could use the same logically fallacious arguments to show that every bodies everyday experiences are just not real.

One example.

Human visual colour does not exist, as it is merely the ratio's of three different sets of cones in your eyes that have different spectral sensitivities that are then interpreted by the human brain to give a sensation/illusion of colour.

Does this mean that colour does not exist? Yes! All you humans just believe this nonsense figment of your imagination.

It is just a delusional belief system that you all adhere to apart from the totally colour blind.

To get back to this extraordinary result of detecting 'gravitational waves'. It is more the detection of gravitational fluctuations due to quantum fluctuations at a time of 'inflation' in a very early Universe about the size of a grape?



I am waiting for the string theorists take on this.

Bert

[colinmlegg]

5 sigma, r=0.2 +- 0.05 :)

https://www.youtube.com/watch?v=ZlfIVEy_YOA

[sjastro]

You are not detecting gravitational fluctuations. Gravity and gravitational waves are very different animals. In GR gravity is a fictitious force and observer dependent, gravitational waves are ripples in space time and have a quadrupole symmetry. If you put test particles in the way of an approaching gravitational wave, particles orientated in one direction of the wave where they are pulled together, will at 90 degrees be pulled apart.
It is this property of gravitational waves which results in the polarization of photons has led to the discovery.

Regards

Steven

[avandonk]

Thanks for that clarification Steven.

I had it totally wrong!

Bert

[Shiraz]

Crikey - first Higgs and now inflation. It is tremendously exciting to be around to see all this happening.

[sn1987a]

I can remember when they announced they found the W and Z Bosons many Shubs and Zulls knew what it was to be roasted in the depths of the Sloar that day I can tell you!

[Astro_Bot]

Enter the twilight zone .... I just watched Ghostbusters two nights ago (Sunday)! :abduct:

[Shiraz]

just watched the ABC news - naah nobody interested in a huge advance in physics. Sigh!

[mr bruess]

once again Einstein is proven right in that Gravitational Waves do exist.

[sn1987a]

Yeah you'd think that the discovery of b-mode polarization imprinted on the CMB by primordial quantum gravitational waves thus proving inflation in the first micro nano femto second of the big bang would be up there with " where the heck is MH 370?" :P

[colinmlegg]

Not to mention the trivial news that we probably live in a bubble universe, bobbing around in an infinite sea of other bubbles. not very newsworthy... ;)