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Imagining and Planning Interstellar Exploration

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"If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare”: A review

What can we say about the possible appearance and spread of civilizations in the Milky Way? There are many ways of approaching the question, but in today’s essay, Dave Moore focuses on a recent paper from Robin Hanson and colleagues, one that has broad implications for SETI. A regular contributor to Centauri Dreams, Dave was born and raised in New Zealand,...

A Habitable Exomoon Target List

Are there limits on how big a moon can be to orbit a given planet? All we have to work with, in the absence of confirmed exomoons, are the satellites of our Solar System’s planets, and here we see what appears to be a correlation between a planet’s mass and the mass of its moons. At least up to a point – we’ll get to that point in a moment. But consider:...

Dyson Spheres: The White Dwarf Factor

I often think of Dyson structures around stars as surprisingly benign places, probably motivated by encountering Larry Niven’s wonderful Ringworld when it was first published by Ballantine in 1970. I was reading it in an old house in Iowa on a windy night and thought to start with a chapter or two, but found myself so enthralled that it wasn’t until...

Habitability: Look to Younger Worlds

A liquid water-defined habitable zone is a way of establishing parameters for life as we know it around other stars, and with this in mind, scientists study the amount of stellar radiation a planet receives as one factor in making the assessment. But of course, not everything in a habitable zone is necessarily habitable, as our decidedly uninhabitable...

Free-Floating Planets as Interstellar Arks

We haven’t found any technosignatures among the stars, but the field is young and our observational tools are improving steadily. It’s worth asking how likely an advanced civilization will be to produce the kind of technosignature we usually discuss. A Dyson swarm should produce evidence for its existence in the infrared, but not all advanced technologies...

Attack of the Carbon Units

“The timescales for technological advance are but an instant compared to the timescales of the Darwinian natural selection that led to humanity’s emergence — and (more relevantly) they are less than a millionth of the vast expanses of cosmic time lying ahead.” — Martin Rees, On the Future: Prospects for Humanity (2018). by Henry Cordova This bulletin...

Toward Kardashev Type I

It seems a good time to re-examine the venerable Kardashev scale marking how technological civilizations develop. After all, I drop Nikolai Kardashev’s name into articles on a regular basis, and we routinely discuss whether a SETI detection might be of a particular Kardashev type. The Russian astronomer first proposed the scale in 1964 at the storied...

Interstellar Implications of the Electric Sail

Not long ago we looked at Greg Matloff’s paper on von Neumann probes, which made the case that even if self-reproducing probes were sent out only once every half million years (when a close stellar encounter occurs), there would be close to 70 billion systems occupied by such probes within a scant 18 million years. Matloff now considers interstellar...

Europa’s Double Ridges: Implications for a Habitable Ocean

I’m always interested in studies that cut across conventional boundaries, capturing new insights by applying data from what had appeared, at first glance, to be unrelated disciplines. Thus the news that the ice shell of Europa may turn out to be far more dynamic than we have previously considered is interesting in itself, given the implications for...

Good News for a Gravitational Focus Mission

We’ve talked about the ongoing work at the Jet Propulsion Society on the Sun’s gravitational focus at some length, most recently in JPL Work on a Gravitational Lensing Mission, where I looked at Slava Turyshev and team’s Phase II report to the NASA Innovative Advanced Concepts office. The team is now deep into the work on their Phase III NIAC study,...

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