Days on Tau Ceti f: 15 — Report #17 recorded in the lake cave.

After two days of waiting, my detector vibrated and I saw a pair of creatures enter the cave. Bipeds. I could not react; I simply stayed and watched. Now they have left, taking some of the fish.

Bipeds. In a certain sense it is a historic moment, but also a little disappointing. Sometimes I wonder whether this planet is truly unrelated to Earth in some way. Most of the vegetation and animals I have seen bear some resemblance to those that exist on Earth. The atmosphere, the climate, atmospheric pressure, gravity, rotation period, the water cycle — all of it is so similar to Earth that sometimes I feel as though I am merely on a new, undiscovered continent, not as far from home as I really am. I think I forget that I am several light-years from Earth, on a mission to discover the source of the message we received years ago.

In any case, I am going to wait a little longer before leaving here. I will follow those creatures from a distance to see where they are headed. Were they the ones who produced those columns of smoke I saw from the mountain? What will I do if they find me? I have no idea of the language they use; I heard a couple of sounds when they came in, but nothing concrete. It was so dark that I tried not to show myself at all. I could only think: can they see in the dark? I have no idea how they might react, and all I know of them amounts to the few minutes when they came in, took the fish, and left. I did not even manage to see whether they were wearing clothes or what color they were. I have no basis for any conclusions.

To a certain extent I am afraid of what might happen. What if they react badly and kill me. Perhaps not.

In any case, I am going to move to the entrance of the cave now. The rain has eased greatly and has practically stopped. From here I can see they are in a boat made of tree trunks. They are wearing clothes and have a greenish-brown color. Nothing supernatural.

They are heading in an easterly direction. I will have to walk around the lake, and I hope not to lose sight of them. And like everything else I have seen here, they are moving very slowly.

Could it be that their perception is equally slow? How would I appear to a being who arrives and moves far faster than them? Is their communication also this slow? In any case, I am making my way to avoid losing them. I just need to gather my things and I will be on my way.

One more thing I have been meaning to record. During the nights in the cave I left the radio receiver running passively, and I picked up something unexpected — faint signals from somewhere to the east, near where those constructions are. Not random noise. There is a clear pattern in the phase shifts. I have tried AM and FM demodulation with no result, and FSK gave me nothing but garbage. Whatever encoding they use, it is more sophisticated than I expected from what I have seen. I think it may be some form of phase shift keying — PSK — but I cannot confirm this without better equipment. I cannot decode any of it. I do not even know if it is communication, or something else entirely.

What I can measure is the phase offset of the carrier itself — 78.5 degrees. I do not know if that means anything. I noted it anyway.