Cost–benefit analysis of space exploration: Some ethical considerations

Humanity faces many important decisions about space exploration. A major but controversial decision-making paradigm is cost–benefit analysis (CBA). This paper discusses some ethical considerations in CBA that are important to decision making about space exploration, including how we define costs and benefits; space exploration's non-market value; the standing of future humans and of extraterrestrials; and the role of discounting in evaluating long-term space exploration projects.     

Limits on interstellar messages

Despite the fact that major efforts have been expended on passive searches for extraterrestrial signals, few deliberate “transmissions” to potential alien recipients have occurred. These have generally taken the form of simple graphics depicting such things as our appearance, location, and biological construction. In this paper, we consider (a) the fundamental technical and astronomical limitations to interstellar messaging—in other words, how many “bits” could any society reasonably send, and (b) what might be a likely transmission strategy. These considerations suggest approaches for SETI programs, as well as giving insight into the types of messages we might construct for eventual replies to received signals.     

我与道教

到2006年．我已历18载学习传统中医。通过在美国和中国的学习．我已于2003年获得了中国河南大学授予的医学博士学位．在中国的数次旅行中．我来到青城山并沉浸于这座被誉为道教发源地名山的壮丽与秀美之中。就在这里的道观中．我遇到我的道教师傅张明心．她无私地开始教授我一些基础知识．并引导我最终树立自己生活的方向。     

Efficiency in SETI

While modern SETI experiments are often highly sensitive, reaching detection limits of 10^?25 W/m² Hz in the radio, interstellar distances imply that if extraterrestrial societies are using isotropic or broad-beamed transmitters, the power requirements for their emissions are enormous. Indeed, isotropic transmissions to the entire Galaxy, sufficiently intense to be detectable by our current searches, would consume power comparable to the stellar insolation of an Earth-size planet.In this paper we consider how knowledge can be traded for power, and how, and to what degree, astronomical accuracy can reduce the energy costs of a comprehensive transmission program by putative extraterrestrials. Indeed, an exploration of how far this trade-off might be taken suggests that extraterrestrial transmitting strategies of civilizations only modestly more advanced than our own would be, as are our SETI receiving experiments, inexpensive enough to allow multiple efforts. We explore the consequences this supposition has for our SETI listening experiments.