Goodbye, Cassini

I met Cassini in 1996 at JPL before it departed for Saturn. For 20 years I have cheered its mission. That mission is over, and Cassini’s watch has ended.

I posted this six years ago here at haibane, but it’s worth reposting in salute: an incredible compilation of a flyby of the Saturnian system:

5.6k Saturn Cassini Photographic Animation from stephen v2 on Vimeo.

We Just Got Our ’30s Sci-Fi Plots Back

By now, you’ve heard that seven – count ’em, seven – terrestrial planets have been discovered orbiting the ultra-cool M8 star Trappist-1.  According to the paper that the research team released yesterday, all of them could potentially have liquid water on their surfaces, although only three are judged to be good candidates: the authors’ model considers it likely that the three innermost planets have succumbed to a runaway greenhouse effect and that the outermost is too cold.  But that still leaves three potentially habitable planets in a single system.

Those three – Trappist-1e, 1f and 1g – range from .62  to 1.34 estimated Earth masses, and as one would expect from a red-dwarf system, they’re  tidally locked and orbit close to their star with periods of 6 to 12 days.  Their orbits are also very close to each other.  The distance between the orbits of 1e and 1f is .009 AUs – about 830,000 miles – and 1f passes within 750,000 miles of 1g.  This is a system that, even according to its discoverers, shouldn’t exist – their model gives it only an 8.1 percent chance of surviving for a billion years – but as they point out, it obviously does.

There are many more fascinating details about the Trappist-1 system and still more that we have yet to learn.  The discoverers hope that further research, and the launch of the James Webb space telescope next year, will enable them to confirm the details of the planets’ atmospheres and possibly look for biological signatures.  But in the meantime, for those of us who write SF, the discovery of the Trappist-1 system means this: we just got our pulp-era plots back.

We’ve all read stories from the heady days of the 1930s in which the intrepid heroes travel to Mars or Venus in a few days, take off their space suits, breathe the air, encounter exotic life forms and interact with non-human societies.  As we learned more about our solar system, that all got taken away.  The jungles of Venus and the canals of Barsoom have long since been relegated to the realm of nostalgia, and if we want aliens in our stories, we have to cross impossible interstellar distances to find them.

But now, there’s a system where all that can happen!  Three habitable worlds with orbits less than a million miles apart, Hohmann transfers that can be done in a few weeks with inspired 1950s tech – we’ve got the ingredients for interplanetary travel that’s almost as easy as pulp writers imagined it.  And a citizen of Trappist-1f might actually find that Old Venus jungle world one planet in and an arid Old Mars one planet out, and generations of its people could watch their neighbors’ fields and cities grow and dream of one day visiting them.  All we need to do to make pulp stories into hard SF again is move them 40 light years.

All right, we’d need to do a little more than that.  The planets are tidally locked – and with zero eccentricity, they don’t have libration-generated twilight zones – so we’d need to model the day-side and night-side weather.  We’d need to account for the tidal and geological effects of so many worlds so close together, and the atmosphere had better have plenty of ozone to protect against UV and X-ray emissions.  But none of those constraints are deal-breakers, and within them, Weinbaum-punk is suddenly acceptable.

That may not last, of course.  By this time next year, the research team might have found that the Trappist-1 planets have reducing atmospheres or that there’s insufficient protection from stellar radiation or that some other factor makes pulp SF as impossible in that system as in our own.  But right now, it’s wide open to stories of the imagination.  We’ve found one spot in the universe where it’s the Golden Age all over again.

Stargazing at Sandstone Peak

I went stargazing last night at Sandstone Peak in Malibu with my friend Huzaifa – here are some of the post-processed long-exposure shots he took:

Huzaifa has two scopes, and a local named Bob showed up with his own rig. All together, we viewed Saturn’s rings, Jupiter’s moons and bands, and Mars, not to mention a few Messier globular clusters, an open cluster in Hercules, and Berenice’s Comb.

Here’s the location – the ocean was due south, and offered the darkest skies, though we left around midnight, well before the bulk of the Milky Way rose. The western sky was a slightly contaminated by glow from Oxnard. Due east was pretty poor due to light from Thousand Oaks and the Valley beyond. The bulk of Los Angeles proper was southeast and too far away to really interfere, however. For a site only 30 min from home, this was an absolutely superb location, especially for the southeastern sky. See:

“Blood moon” lunar eclipse as seen from Madison, WI

Photos of the blood moon eclipse of April 15th 2014, taken at 3:00 am using a Canon G5:

IMG_8057IMG_8048

No tripod, unfortunately. But well worth the interrupt in sleep. The window in the cloud cover was perfect! Magnificent!

UPDATE – great writeup from EarthSky on why Mars was so close to the moon, and a nice illustration from Classical Astronomy page on Facebook that matches the picture – the blue star to the lower right is Spica and Mars is the bright red spot on the upper right.

eclipse-mars-spica-Classical-Astronomy

Debating Dyson spheres

a wonderfully geeky debate is unfolding about the practicality of Dyson Spheres. Or rather, a subset type called a Dyson Swarm. George Dvorsky begins by breaking the problem down into 5 steps:

  1. Get energy
  2. Mine Mercury
  3. Get materials into orbit
  4. Make solar collectors
  5. Extract energy

The idea is to build the entire swarm in iterative steps and not all at once. We would only need to build a small section of the Dyson sphere to provide the energy requirements for the rest of the project. Thus, construction efficiency will increase over time as the project progresses. “We could do it now,” says Armstrong. It’s just a question of materials and automation.

Alex Knapp takes issue with the idea that step 1 could provide enough energy to execute step 2, with an assist from an astronomer:

“Dismantling Mercury, just to start, will take 2 x 10^30 Joules, or an amount of energy 100 billion times the US annual energy consumption,” he said. “[Dvorsky] kinda glosses over that point. And how long until his solar collectors gather that much energy back, and we’re in the black?”

I did the math to figure that out. Dvorsky’s assumption is that the first stage of the Dyson Sphere will consist of one square kilometer, with the solar collectors operating at about 1/3 efficiency – meaning that 1/3 of the energy it collects from the Sun can be turned into useful work.

At one AU – which is the distance of the orbit of the Earth, the Sun emits 1.4 x 10^3 J/sec per square meter. That’s 1.4 x 10^9 J/sec per square kilometer. At one-third efficiency, that’s 4.67 x 10^8 J/sec for the entire Dyson sphere. That sounds like a lot, right? But here’s the thing – if you work it out, it will take 4.28 x 10^28 seconds for the solar collectors to obtain the energy needed to dismantle Mercury.

That’s about 120 trillion years.

I’m not sure that this is correct. From the way I understood Dvorsky’s argument, the five steps are iterative, not linear. In other words, the first solar panel wouldn’t need to collect *all* the energy to dismantle Mercury, but rather as more panels are built their increased surface area would help fund the energy of future mining and construction.

However, the numbers don’t quite add up. Here’s my code in SpeQ:


sun = 1.4e9 W/km2
sun = 1.4 GW/km²

AU = 149597870.700 km
AU = 149.5978707 Gm

' surface of dyson sphere
areaDyson = 4*Pi*(AU^2)
areaDyson = 281229.379159805 Gm²

areaDyson2 = 6.9e13 km2
areaDyson2 = 69 Gm²

' solar power efficiency
eff = 0.3
eff = 0.3

' energy absorbed W
energy = sun*areaDyson2*eff
energy = 28.98 ZW

'total energy to dismantle mercury (J)
totE = 2e30 J
totE = 2e6 YJ

' time to dismantle mercury (sec)
tt = totE / energy
tt = 69.013112491 Ms

AddUnit(Years, 3600*24*365 seconds)
Unit Years created

' years
Convert(tt, Years)
Ans = 2.188391441 Years

So, I am getting 2.9 x 10^22 W, not 4.67 x 10^8 as Knapp does. So instead of 120 trillion years, it only takes 2.2 years to get the power we need to dismantle Mercury.

Of course with the incremental approach of iteration you don’t have access to all of that energy at once. But it certainly seems feasible in principle – the engineering issues however are really the show stopper. I don’t see any of this happening until we are actually able to travel around teh solar system using something other than chemical reactions for thrust. Let’s focus on building a real VASIMIR drive first, rather than counting our dyson spheres before they hatch.

Incidentally, Dvorsky points to this lecture titled “von Neumann probes, Dyson spheres, exploratory engineering and the Fermi paradox” by Oxford physicist Stuart Armstrong for the initial idea. It’s worth watching:

UPDATE: Stuart Armstrong himself replies to Knapp’s comment thread:

My suggestion was never a practical idea for solving current energy problems – it was connected with the Fermi Paradox, showing how little effort would be required on a cosmic scale to start colonizing the entire universe.
[…]
Even though it’s not short term practical, the plan isn’t fanciful. Solar power is about 3.8×10^26 Watts. The gravitational binding energy of Mercury is about 1.80 ×10^30 Joules, so if we go at about 1/3 efficiency, it would take about 5 hours to take Mercury apart from scratch. And there is enough material in Mercury to dyson nearly the whole sun (using a Dyson swarm, rather than a rigid sphere), in Mercury orbit (moving it up to Earth orbit would be pointless).

So the questions are:

1) Can we get the whole process started in the first place? (not yet)

2) Can we automate the whole process? (not yet)

3) And can we automate the whole process well enough to get a proper feedback loop (where the solar captors we build send their energy to Mercury to continue the mining that builds more solar captors, etc…)? (maybe not possible)

If we get that feedback loop, then exponential growth will allow us to disassemble Mercury in pretty trivial amounts of time. If not, it will take considerably longer.

APOD got screwed

I was very eager to see the latest APOD, a timelapse video of the night sky where every frame was digitally rotated to make the sky seem stationary and the earth rotate. Unfortunately, the video was served with a copyright takedown notice by one Nicolas Fabian Bustos Vargas, who appears to be a PhD at the Chilean observatory in question. Here’s the video linked from APOD and here’s the claimant’s video channel at YouTube, where the raw footage is from.

It seems that Bustos took the original video and Jose Francisco, another astronomer and “visual artist” processed the footage to make the video linked from APOD, without permission. APOD and its users are caught in the middle, and it’s a shame.