The BICEP2/Planck joint analysis is out. Evidence for "B-mode" polarized light in the Cosmic Microwave Background NOT confirmed. Too much interstellar dust in our galaxy - which can produce the same effect. Too bad. I don't know if there is a way around this dust problem with future instruments.

 

(As I understand it, inflation -- the extreme expansion of the very early universe -- is theorized to produced gravitational waves. These in turn would produce a swirling B-mode polarization in the Cosmic Microwave Background. This is what the BICEP2 telescope in the South Pole was looking for.)

 

Link: http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_gravitational_waves_remain_elusive

Will have to read up on that. Good spot - thanks

The BICEP2/Planck joint analysis is out. Evidence for "B-mode" polarized light in the Cosmic Microwave Background NOT confirmed. Too much interstellar dust in our galaxy - which can produce the same effect. Too bad. I don't know if there is a way around this dust problem with future instruments.

 

(As I understand it, inflation -- the extreme expansion of the very early universe -- is theorized to produced gravitational waves. These in turn would produce a swirling B-mode polarization in the Cosmic Microwave Background. This is what the BICEP2 telescope in the South Pole was looking for.)

 

Link: http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_gravitational_waves_remain_elusive

I watched this on horizon yesterday, Planck analysis saying it was nearly 75-100% certain to be dust,

 

But if there are gravitational waves, wouldnt the dust only highlight these waves?

We use smoke to see aerodynamics in a wind tunnel/or dyes in water to see currents, surely the dust would show up these waves better than without dust?

I watched this on horizon yesterday, Planck analysis saying it was nearly 75-100% certain to be dust,

 

But if there are gravitational waves, wouldnt the dust only highlight these waves?

We use smoke to see aerodynamics in a wind tunnel/or dyes in water to see currents, surely the dust would show up these waves better than without dust?

 

This is a bit beyond my paygrade - but: No, I think not. The Gravitational waves are not still there ( I guess they would be attenuated to nothing and not in the right place); we were looking for the fossil evidence of past gravitational waves in the polarisation of the CMBR which is very ancient (just a few hundred thousand years after BB) - the dust however is very recent in comparison (ie the gravitational waves would gone before the dust was around).

 

FYG - we cannot directly detect gravitational waves yet - we have tried and failed a few times; they are just too damned hard to resolve from the noise. But we are very good at detecting light and other EMR - so we look at the Cosmic Microwave Background and measure polarisation patterns. It was predicted that the squashing and stretching of space that is a gravitational wave (specifically that from the BB) would leave very specific patterns of polarisation - which BICEP2 claimed to have identified.

This Caltech article on gravitational waves is illuminating, but what is the Strain parameter in the vertical axis of the gaph?

strain is the fractional difference in displacement of two similar masses ( separated by a small distance in the direction of the wave) due to the passing of the gravitational wave - ie it is the net distortion due to the passage of a gravitational wave.

 

if you have a field of free floating test objects perpendicular to the direction of the propagation of the wave:

a. take the central point

b. as the wave passes then objects will move towards/away from central point

c. the ratio of distance moved / distance from central point is the "strain"

d. (actually twice the ratio - but who is counting?)

strain is the fractional difference in displacement of two similar masses ( separated by a small distance in the direction of the wave) due to the passing of the gravitational wave - ie it is the net distortion due to the passage of a gravitational wave.

 

if you have a field of free floating test objects perpendicular to the direction of the propagation of the wave:

a. take the central point

b. as the wave passes then objects will move towards/away from central point

c. the ratio of distance moved / distance from central point is the "strain"

d. (actually twice the ratio - but who is counting?)

Yep. Got it. Thanks.