I've been out of town and haven't gotten around to responding to this
yet. Here's a quick take on it.

On 6/21/2007 5:00 PM, bibhasde wrote:
>
>
> Earlier I posted a link to my site alleging science fraud by the
> physics establishment.


[snip]

> (http://www.geocities.com/bibhasde/blackbody.html

[snip]

I don't claim to have sufficient expertise to comment on everything,
though I think I understand what is going on a great deal better than
the author of this posting. First of all, if you think you have a
legitimate criticism, you should spend less time talking about grand
conspiracies and more time discussing the details of the problem. I had
to wade through pages and pages of poorly-formatted html before I could
get to the meat of the claim.

It is quite extraordinary that you seem to be attributing the discovery
of the black body radiation to COBE. The black body spectrum had
already been measured several times by different experimenters, and it
was known to be very close to an ideal black body before COBE was launched.

The assertion of the author is that if we want to give FIRAS credit for
measuring this spectrum very precisely, we must claim that the Winston
cone's performance must be precisely known as a function of frequency
and angle. (He also talks about area, time, and solid angle, which is
slightly confused, but this is beside the point). In this he is mistaken.

In principle, to completely understand a detector, you need only map its
preformance as a function of angle and frequency. This can be done, for
example, by placing a point source of a particular frequency at various
locations, and then measuring the response of the detector. It is NOT
necessary to know the area of the detector, or to precisely calculate
the efficiency of any given component. You simply measure the
performance of the complete instrument. The author is confused in
suggesting that you need to know how each component performs - all that
matters is how the whole object performs.

In addition, for this measurement, the response as a function of angle
is not relevant. Since the source we are measuring (the cosmic
background radiation) is presumed to be nearly independent of angle,
there is no need to measure the angular dependance. All you need to do
is measure the frequency dependence integrated over solid angle.

Now, if you THINK you have a perfect black body, and you are planning to
compare the spectrum to a black body, all you need to do is put a black
body in front of your detector, and vary its temperature, and then
compare the experimental spectrum you get with the various black body
reference spectra. If you have a perfect match with one of the
reference spectra, then it looks an awful lot like a black body, and it
probably is one.

Of course, there is still the issue of how well you can measure its
dependance on frequency. This can be tested by placing a known
monochromatic source in front of the detector, and simply measure what
frequency distribution is measured by the detector. This was presumably
done as well.

With these two types of measurements, you are in excellent shape to
measure the cosmic background radiation and will have a good idea of
what the spectrum is like. The author's claims that you have to
accurately measure every step of the process is incorrect.

I will note, as a conclusion, that though FIRAS' measurements are
important (for example, it completely annihilated a paper I was trying
to get published at the time), it is NOT the most important discovery of
COBE. This was done by DMR, which discovered that there are slight
temperature variations in different directions.

Eric Carlson