It was largely irrelevant to the thread where it originally appeared, but I think it is also largely wrong. I am pretty damn sure that we can detect all frequencies below the light spectrum at least down to the ELF radio spectrum - we might have problems with weak signals but not lowish frequencies. Admittedly you need a landmass as the detector (like a peninsular or a subcontinent), but it is technically feasible to detect an ELF signal.Are you saying there is no limit below which we cannot detect light ? That's just plain wrong. Our instruments are not infinitly sensitive. Already we have to cool the detectors to very low temperatures.
Problems with detecting frequencies below ELF (below 1 hertz for example) would have nothing to do with the temperature of the detectors and more to do with the size of the detectors.
Is this wrong?
I don't think there is any transmitter in the universe that is moving fast enough to cause doppler shift down to below ELF, is there?