We seem to be 3-1 here on the key issue of yelling to aliens, with Vakoch opposing the rest of us. So I’ll make this one comment here on this subject, and then turn my attention to topics where I disagree with Brin and Barkow.
In the ordinary Pascal’s wager, God is said to greatly reward those who believe in him and do what he favors. The rewards are so huge that even those who assign only a small chance to God existing are wise to try to make themselves believe.
A standard response is to point out that a great many different Gods might exist, each of whom favor different actions. If you have little idea of which Gods exist or of what acts they favor, then there is little point in taking their rewards into account. You might as well just ignore them.
Douglas Vakoch seems to me to suggest an aliens version of Pascal’s Wager. He suggests that aliens might be near and already know we are here, but refuse to talk to us until we send the first message. But once we do talk first, they’ll send us lots of useful info. So even if we think the chances are slim that any aliens are around, the rewards would be so huge that we might as well take the chance.
The standard response mentioned above to the ordinary Pascal’s Wager also seems appropriate for this variation - there are many other possible kinds of aliens. For example, there may be aliens who will only shower us with valuable info if we show ourselves to be rational by keeping quiet for a long while before yelling. Or maybe there are aliens with a strong sense of status who will destroy us for being uppity by speaking louder than our status justifies.
Surely it is not enough to simply point out the possibility of good outcomes from yelling. We must also consider the relative chances and values of good and bad outcomes. 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.
To those who think aliens must already know we are here, consider a three-parameter family of possible aliens. Aliens could vary by distance, by listening intensity, and by listening luck. Aliens that are closer, listen intensely, and are lucky already know about us. But aliens that are distant, listen little, and are unlucky do not.
While there are aliens in this parameter space who must already know we are here, or who will know when our signals reach them, there are also points in this space holding aliens who would not know of us if we did not yell. So it all comes down the the distribution of aliens over this parameter space. About which we are substantially uncertain. So I can’t see how one could plausibly be confident that no aliens would learn of us via our yelling.