Continuing the discussion about yelling to aliens at *Cato Unbound*, I ask:

Regarding a choice to yell on purpose, there are two key relevant parameters: a value ratio, and a chance ratio.

The *value ratio* divides the loss we would suffer if exterminated by aliens by the gain we would achieve if friendly aliens were to send us helpful info. I’d guess this ratio is at least one thousand. The *probability* ratio divides the chance that yelling induces an alien to send helpful info by the chance that yelling induces an alien to destroy us. I’d guess this ratio is less than one hundred.

If we can neglect our cost or value regarding the yelling process, then we need only compare these ratios. If the value ratio is larger than the chance ratio, yelling is a bad idea. If the value ratio is smaller than the chance ratio, yelling is a good idea. Since I estimate the value ratio to be larger than the chance ratio, I estimate yelling to be a bad idea. If you disagree with me, I want to hear your best estimates for these ratios. (more)

What are your estimates?

My value ratio is close to 1:1. My reasoning:

1. With sufficiently advanced medical technology I will be able to live at least ~10^34 years.2. The utility increment of living 10^34 years instead of 10^2 years (call it w) is much higher in absolute value than the utility decrement of dying now (call it -1). 3. I expect a ~50% chance that we'll achieve escape velocity in time for myself, or via cryogenics. Hence, my current expected future utility is ~w/24. If aliens come and help us, technology will improve massively, including technology to help us live longer. Hence my utility will be ~w.5. If aliens kill us my utility will be ~0.

The 100 million years figure shouldn't matter if the probability of extinction of all life isn't too high (if so much as a subterranean tardigrade survives you can have a wide variety of complex life again within 100 million years).

I think there are 3 plausible explanations. They're not there (or at least not in range), they think getting here is too costly/not interesting enough (note that on a small scale they may send scientific probes without us ever knowing) and finally the third, least plausible, but most optimistic one: one of the alien civilizations is "protecting" us (they may do this passively, with us simply being located inside or behind their defensive perimeter).