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View Full Version : WMAP - science or bologna, how the heck did they do it?



efanton
2015-Nov-03, 08:05 AM
I find it incredible that the WMAP results were so accurate, and even more surprising that they match EXACTLY with no deviation whatsoever from what was expected through theory.

This is not a conspiracy post, nor a denial post
If it was done then its an unbelievable achievement, but a little thought will tell you that this experiment had so many factors that could interfere with the results to the point that even the slightest error in construction or design would make the results totally useless
Why do I question the WMAP results? Because I want to know exactly how they did it.

for instance:

The matching of results against theory is so amazing that if a typical printed circuit board had been used on the satellite its electronic noise would probably be more than enough to screw the experiment the second it was switched on.
How did they manage to eliminate totally the electronic noise of the satellite?

As the WMAP results ended up with a range in temperatures of so small (blue 2.721 Kelvin, and red 2.729 Kelvin) how was this achieved?
think about this seriously, they had to get an instrument to measure such low temperatures fractions of a degree above absolute zero without the heat from the satellite, the electronics or indeed the heat from the sun affecting the measurement and for that measurement to be accurate to within a thousandth of a degree.
How did they manage to get accurate measurements to within a thousandth of a degree without the latent heat from the satellite, the electronics or indeed the heat from the sun affecting the measurement?

WMAP was designed to measure the background radiation of the universe. Hubble's deep field images have proven that there is no void, or empty lines of sight in space. WMAP's mission was to measure the background but no matter which way it was pointing it would be measuring radiation created and emitted by stars and galaxies.
How was the radiation emitted from stars and galaxies eliminated or removed from the results?

I would really love to know how they did it.
To me personally I find the fact they they could actually get these measurements more amazing than the actuals experiments results themselves

Jeff Root
2015-Nov-03, 12:34 PM
Hubble's deep field images have proven that there
is no void, or empty lines of sight in space.
What would you say is the predominant color of the
Hubble deep field images? I see mostly black.
Something like 95% black.

-- Jeff, in Minneapolis

Cougar
2015-Nov-03, 12:43 PM
I would really love to know how they did it.

For the complete answer, you'll probably have to go back and get your PhD.

But to give you some idea, from NASA's WMAP Observatory page (http://map.gsfc.nasa.gov/mission/observatory.html)....



The WMAP instrument consists of a set of passively cooled microwave radiometers (connected to radiator panels with metal straps) with 1.4 x 1.6 meter diameter primary reflectors to provide the desired angular resolution. Measuring the temperature of the microwave sky to an accuracy of one millionth of a degree requires careful attention to possible sources of systematic errors. The avoidance of systematic measurement errors drove the design of WMAP:





The instrument has five frequency bands from 22 to 90 GHz to facilitate separation of galactic foreground signals from the cosmic background radiation.








WMAP is a differential experiment: if you would like to know whether one piece of wood is longer than another, it is better to put the pieces directly next to each other than to measure them separately with a ruler. WMAP measures the temperature difference between two points in the sky rather than measuring absolute temperatures.








An orbit about the Sun-Earth L2 libration point that provides for a very stable thermal environment and near 100% observing efficiency since the Sun, Earth, and Moon are always behind the instrument's field of view.








A scan strategy that rapidly covers the sky and allows for a comparison of many sky pixels on many time scales.




Especially note point 2.

Noclevername
2015-Nov-03, 01:01 PM
What would you say is the predominant color of the
Hubble deep field images? I see mostly black.
Something like 95% black.

-- Jeff, in Minneapolis

What frequencies are you using?

ToSeek
2015-Nov-03, 03:24 PM
Title edited slightly to change a slightly dubious word.

[antoniseb] Same here.

Jeff Root
2015-Nov-03, 05:09 PM
What frequencies are you using?
450 nm, 606 nm, and 814 nm. Blue, orange, and infrared.

I had just read those numbers this morning, but I didn't
type them from memory. :)

-- Jeff, in Minneapolis

Shaula
2015-Nov-03, 05:30 PM
You could try http://planck.caltech.edu/publications2013Results.html as a starter. This is for the newer, more sensitive Planck system but much of the basic processing is the same and they often reference the older experiment or papers relating to it. The first ten papers have a lot of detail about the instrument and processing.

Reality Check
2015-Nov-03, 11:55 PM
WMAP was designed to measure the background radiation of the universe. Hubble's deep field images have proven that there is no void, or empty lines of sight in space. WMAP's mission was to measure the background but no matter which way it was pointing it would be measuring radiation created and emitted by stars and galaxies.
How was the radiation emitted from stars and galaxies eliminated or removed from the results?
The short answer is by measuring the radiation emitted from stars and galaxies and removing it.
Longer:
We do not have to worry about microwave sources in Hubble's deep field images - the galaxies are too far away for the amount of microwaves to be detected. That "radiation created and emitted by stars and galaxies" you worry about cannot be measured.
We do have to worry about nearer galaxies that emit detectable microwave radiation.
We do have to worry about a really close galaxy and its microwave radiation - the Milky Way.
Max Tegmark's CMB data analysis center (http://space.mit.edu/home/tegmark/cmb/pipeline.html) gives an overview of the entire data analysis pipeline (but is only current to 1999).
The Jodrell Bank Centre for Astrophysics (http://www.jodrellbank.manchester.ac.uk/research/cosmos/foregrounds.html) is involved in measuring foregrounds to be removed from CMB data.

WayneFrancis
2015-Nov-04, 03:01 AM
...

WMAP was designed to measure the background radiation of the universe. Hubble's deep field images have proven that there is no void, or empty lines of sight in space. WMAP's mission was to measure the background but no matter which way it was pointing it would be measuring radiation created and emitted by stars and galaxies.
How was the radiation emitted from stars and galaxies eliminated or removed from the results?
...

Actually no. There are lots of empty lines of sight.
See all the black in this image of the Hubble Ultra Deep View? Almost all that black stuff is where there is nothing between us and the surface of last scattering, CMBR.

http://imgsrc.hubblesite.org/hu/db/images/hs-2012-37-a-web.jpg

efanton
2015-Nov-16, 12:47 AM
thank you Reality Check. the most sensible answer that actually gave me the links required to get the information I was looking for
Also thanks to Shaula

My concern about these experiments is that any data that needs modifying opens up the opportunity to achieve the results you expect. This is especially concerning when the dealing in minuscule variations.
Further reading has put my mind at rest regarding the WMAP results

George
2015-Nov-19, 09:05 PM
As the WMAP results ended up with a range in temperatures of so small (blue 2.721 Kelvin, and red 2.729 Kelvin) how was this achieved? This temperature is easily found after getting the spectral energy distribution (SED) -- energy across the various wavelengths. The peak energy (Planck temperature) has the temperature you state and is in the microwave band. It is a little different than using a thermometer.

It was predicted that the SED would be seen as almost a perfect black body, and it is, which was another reason the CMBR was so powerful in making the BBT prominent over the one competing theory (Steady State).



How did they manage to get accurate measurements to within a thousandth of a degree without the latent heat from the satellite, the electronics or indeed the heat from the sun affecting the measurement? What can't astronomers do?!! [observationally]:)


WMAP was designed to measure the background radiation of the universe. Hubble's deep field images have proven that there is no void, or empty lines of sight in space. WMAP's mission was to measure the background but no matter which way it was pointing it would be measuring radiation created and emitted by stars and galaxies. The gaps are very important since BBT also needed to explain Olber's paradox - light everywhere due to an infinite universe with infinite no. of stars.


How was the radiation emitted from stars and galaxies eliminated or removed from the results? Carefully! ;)

George
2015-Nov-19, 09:13 PM
thank you Reality Check. the most sensible answer that actually gave me the links required to get the information I was looking for
Also thanks to Shaula

My concern about these experiments is that any data that needs modifying opens up the opportunity to achieve the results you expect. This is especially concerning when the dealing in minuscule variations.
Further reading has put my mind at rest regarding the WMAP results The great power of science is found in its self-correction. If one knows other scientists will test each claim with subsequent studies, why would one risk error and embarrassment to meet wishful thinking needs? [Not being a scientist, I too often ignore this important intrinsic element.]