Re: HISTORY: Dyson Shells

Robert J. Bradbury (
Wed, 25 Aug 1999 15:05:59 -0700 (PDT)

On Wed, 25 Aug 1999, Amara Graps wrote:

> It seems that you left some observations out. The following is
> from Anders' Dyson sphere FAQ.

I am aware of Anders' list, my comments as follows:
> DATE: 1980
> COMMENTS: Search for IR excess due to Dyson spheres around solar
> type stars. Target stars were chosen because too faint for
> spectral type.

As I mentioned & tried to show in my letter -- Dyson sphere will not be seen around visible stars. So, this search was doomed from the start.

> DATE: 1984
> COMMENTS: Lack of fluctuations in 3K background radiation on
> angular scales of 10**-2 Strd. rules out optically thick Dyson
> spheres radiating more than 1 solar luminosity within 100 pc.

This is better. But 100 pc out isn't very far (~300 ly). The "logical" thing for SI's is to put the spheres far away from sources of nasty radiation (i.e. the galaxy core or black holes) as well as to use the smallest stars possible (both for decreasing communication delays and extending longevity). Contrast this with the 400 billion objects by the est. by the Gravitational Microlensing oberservations, in the halo, at 0.3-0.5 Msun -- They are many, far away and should be faint. Slysh may understand some components of the problem since he is very aware of Kardashev's perspective. Fundamentally the problem is that he does not have the instrumentation required for detection.

> DATE: 1987
> COMMENTS: Remote observation (by VLA staff) of IRAS source near
> galactic center to determine if source could be nearby Dyson sphere.
> Source confirmed as OH/IR star.

Clearly looking at a star. The fundamental problem with Dyson shells is that they should be *very* difficult to see in the visible. So, so long as astronomers/SETI people keep looking at "visible" stars, they will keep coming up empty handed. At least they started with an IRAS source which is the right way to go. The problem is that the resolution of the IRAS data isn't very high and the frequency bands only give you barely enough information to make temperature estimates. Kardashev's subsequent work (not in Ander's list) does list a number of unusual features in the distribution of IRAS detectable objects around the galaxy. Since one would expect extragalactical sourcs to have a uniform distribution, it would seem that they are detecting galactic assymetries. I list this as a possible point of interest in my Matrioshka Brain paper.

Re: sources

I have almost all of the sources mentioned converted and available in a (private) HTML database related to this this work. There is very little that has been done in the astronomical community of which I am unaware (only for example unpublished studies with negative results).