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Ask Dr. SETI ®

Chapter 3: Philosophy

Dark Matter Frequencies

Dear Dr. SETI:
From what I've read, you are searching for a signal using the natural frequency of Hydrogen at 1420MHz, since that is most abundant element in the Universe, and therefore a likely transmission frequency for a signal. However, according to the latest theories of Dark Matter and Dark Energy, it appears that baryonic matter constitutes only 4% of the known Universe. This implies that there must be more abundant substances than Hydrogen atoms, yet to be discovered.

By extension of the logic of searching for signals on the natural frequency on the most abundant substance in space: if that substance is not Hydrogen, but rather the main constituent particle of Dark Matter, would it be feasible to search for signals on this new (sub-atomic) particle's natural frequency, as a more likely source of transmission than Hydrogen?

Grant (Australia)

The Doctor Responds:
Your logic is unassailable, Grant. But, there is a problem:

Dark matter is, by its very nature, a mystery. It is invisible to us. We can only infer its existence by its apparent interaction with baryonic matter. We don't know exactly what it is. Therefore, we don't know what its emission frequencies might be. In fact, we don't even know if it emits at all (if it did, after all, then it wouldn't be dark matter!) So, at what frequency do we search, for signals aligned with invisible emissions from unknown substances? We just don't know!

Baryonic matter, on the other hand, is visible to us, in the radio spectrum, by the emission lines related to its various atomic transitions. We presume that it is visible to our cosmic companions as well, and that they too can observe its various emission lines. Thus, baryonic matter (such as Hydrogen) produces electromagnetic signposts. Trying to read invisible signs is difficult, even if you do know for sure that they exist.

The problem of calibrating upon hypothesized, invisible emissions from unknown, dark matter is analogous to searching for the so-called Zeta Waves which Philip Morrison hypothesized, as discussed at the end of this previous column. But, when such emissions become visible to us, you can be sure we'll search in their neighborhood.

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