Tag: astronomy

Hycean Worlds

Hycean worlds are hot mini-Neptunes with hydrogen-rich atmospheres and vast oceans on their surfaces. The heat and the pressure wouldn’t be very inviting to us humans, but it’s possible that some forms of life might find it idyllic. these worlds can be up to 2.6x the width of Earth, up to 10 Earth masses, and temperatures in their atmospheres could reach 200 °C. However, conditions in their oceans might be more comfortable. They’re likely to be common too, nestled in between the smaller, rockier Super-Earths and the gaseous, larger mini-Neptunes. Hycean planets could be one of the most promising places to look for signs of life. Not only because they’re common, but biomarkers of life, such as methyl chloride and dimethyl sulphide, could be readily spotted in their atmospheres

Galactic Settlement

The simulation depicts the expansion of a technological civilization through the Milky Way, created along lines previously described in the literature. What we are looking at is the transition between a Kardashev Type II civilization, and a Type III, which has spread throughout the galaxy. This might be a fast process considering the motions of stars themselves, which would overcome the inertia of slower growing settlements and boost expansion rates. Issues like starship capabilities and the lifetime of colonies come into play, but the striking thing is how fast galactic settlement occurs and how the motions of stars factor into the settlement wave. The parameters are everything, and they’re interesting:

  • Ships are launched no more frequently than every 100 ka;
  • Technology persists in a given settlement for 100 ma before dying out;
  • Ship range is 10 light years.
  • Ship speeds are 10 km/s; Voyager-class speeds.
  • The simulation covers 1 ga

Light sphere argument

If we’re to have an experience remotely like the human one, then we have to be relatively close to the beginning of time—since 100s of billions of years from now, the universe will likely be dominated by near-light-speed expanding spheres of intelligence, and a little upstart civilization like ours would no longer stand a chance. I.e., even though our existence is down to some lucky accidents, and even though those same accidents probably recur throughout the cosmos, we shouldn’t yet see any of the other accidents, since if we did see them, it would already be nearly too late for us.

if we want human-originated sentience to spread across the universe, then the sooner we get started the better! Just like Bill Gates in 1975, we should expect that there will soon be competitors out there. Indeed, there are likely competitors out there “already” (where “already” means, let’s say, in the rest frame of the cosmic microwave background)—it’s just that the light from them hasn’t yet reached us. So if we want to determine our own cosmic destiny, rather than having post-singularity extraterrestrials determine it for us, then it’s way past time to get our act together as a species. We might have only a few 100M more years to do so.

and here’s the preprint

Biggest EMP in 10 ka

Today, such a superflare would be civilization-ending.

In the year 774 AD, an enormously powerful blast of matter and energy from space slammed into Earth. Nothing like it had been felt on this planet for 10 ka. A mix of high-energy light and hugely accelerated subatomic particles, when this wave impacted Earth it changed our atmospheric chemistry enough to be measured centuries later. Such an event happening today would be catastrophic. It could take out numerous satellites — the particles and high-energy radiation can short out even hardened electronics — and cause widespread blackouts. Those could take a long time to fix, since the bigger transformers used by power grids cannot be mass-produced.

2022-01-29: An even bigger EMP happened in 9125 BP. It was 2x bigger than the 774 AD one.

Primordial Magnetism

One possibility is that cosmic magnetism is primordial, tracing all the way back to the birth of the universe. In that case, weak magnetism should exist everywhere, even in the “voids” of the cosmic web — the very darkest, emptiest regions of the universe. The omnipresent magnetism would have seeded the stronger fields that blossomed in galaxies and clusters.

Solar System Black Hole

A possible alternative is to probe the gravitational field of this object using small, laser-launched spacecraft, like the ones envisioned in the Breakthrough Starshot project. With a velocity of 0.001c, such spacecraft can reach Planet 9 10 years after launch and can discover it if they can report timing measurements accurate to 10^-5 seconds back to Earth.