关于观测河外文明的可能性：自我指示假设的预测
On the Likelihood of Observing Extragalactic Civilizations: Predictions from the Self-Indication Assumption
摘要：
在星系间规模上扩张资源的雄心勃勃的文明可以从宇宙学距离上观察到，但我们看到的可能性有多大？问题归结为估计宇宙中这些东西的出现率-一个根本不确定的量。尽管存在这种先前的不确定性，但人因因素引起了贝叶斯更新，从而产生了预测。自抽样假设（SSA），一个学校的人择概率，以前曾被用于这一目的。在这里，我们从另一个学校，自我指示假设（SIA）的预测，并指出其特点。SIA倾向于扩张型生命的出现率更高，但我们在当前宇宙时间的存在意味着这样的生命不可能太常见（否则我们的银河系早就被占领了）。这种组合将我们先前巨大的不确定性压缩到几个数量级。背景宇宙学的细节消失了，我们得到了一些明确的结论。例如，如果技术的限制允许一个文明以$v$的速度扩张，那么在我们过去的光锥上至少可以看到一个扩张的宇宙文明的概率是$1-\frac{v^3}{c^3}$。我们还展示了如何从一个假设的全天空调查，检测“$n$“扩展文明（$n \geq 0$）的结果更新SIA估计，并计算宇宙中生命的最终程度。
英文摘要：
Ambitious civilizations that expand for resources at an intergalactic scale could be observable from a cosmological distance, but how likely is one to be visible to us? The question comes down to estimating the appearance rate of such things in the cosmos --- a radically uncertain quantity. Despite this prior uncertainty, anthropic considerations give rise to Bayesian updates, and thus predictions. The Self-Sampling Assumption (SSA), a school of anthropic probability, has previously been used for this purpose. Here, we derive predictions from the alternative school, the Self-Indication Assumption (SIA), and point out its features. SIA favors a higher appearance rate of expansionistic life, but our existence at the present cosmic time means that such life cannot be too common (else our galaxy would long ago have been overrun). This combination squeezes our vast prior uncertainty into a few orders of magnitude. Details of the background cosmology fall out, and we are left with some stark conclusions. E.g. if the limits to technology allow a civilization to expand at speed $v$, the probability of at least one expanding cosmological civilization being visible on our past light cone is $1-\frac{v^3}{c^3}$. We also show how the SIA estimate can be updated from the results of a hypothetical full-sky survey that detects "$n$" expanding civilizations (for $n \geq 0$), and calculate the implied final extent of life in the universe.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
