Radio and optical SETI look for evidence of extraterrestrial civilizations even though we have no evidence that such exist. The search is eminently worthwhile and opens up the ancillary question: How would a transmitting civilization produce a signal strong enough for us to detect it at interstellar distances? Beacons of various kinds have been considered and search strategies honed to find them. But we’ve also begun to consider new approaches to SETI, such as detecting technosignatures in our astronomical data (Dyson spheres, etc.). To this mix we can now add a consideration of gravitational ..read more

The propulsion technology the human characters conceive in the Netflix version of Liu Cixin’s novel The Three Body Problem clearly has roots in the ideas we’ve been kicking around lately. I should clarify that I’m talking about the American version of the novel, which Netflix titles ‘3 Body Problem,’ and not the Chinese 30-part series, which is also becoming available. In the last two posts, I’ve gone through various runway concepts, in which a spacecraft is driven forward by nuclear explosions along its route of flight. We’ve also looked at pellet options, where macroscopic pellets are fired ..read more

Fusion runways remind me of the propulsion methods using pellets that have been suggested over the years in the literature. Before the runway concept emerged, the idea of firing pellets at a departing spacecraft was developed by Clifford Singer. Aware of the limitations of chemical propulsion, Singer first studied charged particle beams but quickly realized that the spread of the beam as it travels bedevils the concept. A stream of macro-pellets, each several grams in size, would offer a better collimated ‘beam’ that would vaporize to create a hot plasma thrust when it reaches the spacecraft ..read more

You never know when a new interstellar propulsion concept is going to pop up. Some of us have been kicking around fusion runway ideas, motivated by Netflix’s streaming presentation of the Liu Cixin novel The Three Body Problem. There Earth is faced with invasion from an extraterrestrial civilization, but with centuries to solve the problem because it will take that long for the fleet to arrive. Faced with the need to get as much information as possible about the invaders, scientists desperately search for a way to get human technology up to 0.012 percent of lightspeed to intercept the fleet ..read more

Eugene Parker, after whom the Parker Solar Probe was named, seems to have been the first to have accurately predicted the stream of particles emitted by the Sun that forms the ‘solar wind.’ Parker made the call in a 1958 paper, when solar sailing was just being noised about for the first time, so it wouldn’t have struck him that the term was a bit incautious. Today, when solar sailing is operational, people often assume the solar wind drives solar sails, when in fact the operating principle for solar sails is the momentum generated by photons, which are themselves massless. But streaming parti ..read more

Don’t you love the way the cosmos keeps us from getting too comfortable with our ideas? The Hubble Constant (H0), which tells us about the rate of expansion of the universe, is still a hot issue because observations from both the Hubble Space Telescope and JWST don’t tally with what the European Space Agency’s Planck mission concluded from its data on the Cosmic Microwave Background (CMB). How exactly do we fine tune the standard model of cosmology to make sense of this? The so-called Hubble Tension is hardly the only issue raised by the acquisition of new and better data, although it may be t ..read more

Just a few weeks ago I wrote about stellar interactions, taking note of a concept advanced by scientists including Ben Zuckerman and Greg Matloff that such stars would make for easier interstellar travel. After all, if a star in its rotation around the Milky Way closes to within half a light year of the Sun, it’s a more feasible destination than Alpha Centauri. Of course, you have to wait for the star to come around, and that takes time. Zuckerman (UCLA), working with Bradley Hansen, has written about the possibility that close encounters are when a civilization will attempt such voyages. I ha ..read more

We’re a species that likes to leave evidence of itself in new places. In Greenland, for example, the Kingittorsuaq runestone, dating from the 14th Century, offers inscriptions that help chart Norse exploration of the region. The oldest inscription at New Mexico’s El Morro dates from 1605, though many explorers left their names and stories on the cliffs there. Apollo 11’s plaque, with its “We came in peace for all mankind” is justly famous, as are the Golden Records of the two Voyagers and the Pioneer plaques, even if the latter were dogged with controversy at the time of their unveiling. Imag ..read more

If individual star systems show us a wide variety of formation scenarios – and we just examined recent ESO work on circumstellar disks in different star-forming regions – the variety in galaxy evolution is even more spectacular. I’m reminded here of an unusual find when my uncle Roland died unexpectedly and I became his executor. Clearing out his house preparatory to sale, I discovered a series of astronomy photographs that he had blown up to huge scale. An image of M31, the great spiral of Andromeda, was fully six feet long and gorgeously mounted. I remembered nights as a child when he would ..read more

Planet formation is a fascinating subtopic of the exoplanet hunt, and it may just have produced the first exoplanet detection in data that go back as far back as 1981, though the event in question has never been confirmed as being caused by a planet. I learned this through a paper sent me recently by Jean Schneider (Observatoire de Paris), who along with colleague Danielle Briot wrote about the early days of transit searches in a chapter for the Handbook of Exoplanets (Springer, 2018). I want to dig deeper into that chapter in a later post, but for now, I note that the planet Beta Pictoris b ..read more