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:
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:
Get materials into orbit
Make solar collectors
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. â€œWe could do it now,â€ says Armstrong. Itâ€™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:
â€œDismantling Mercury, just to start, will take 2 x 10^30 Joules, or an amount of energy 100 billion times the US annual energy consumption,â€ he said. â€œ[Dvorsky] kinda glosses over that point. And how long until his solar collectors gather that much energy back, and weâ€™re in the black?â€
I did the math to figure that out. Dvorskyâ€™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 â€“ meaning that 1/3 of the energy it collects from the Sun can be turned into useful work.
At one AU â€“ which is the distance of the orbit of the Earth, the Sun emits 1.4 x 10^3 J/sec per square meter. Thatâ€™s 1.4 x 10^9 J/sec per square kilometer. At one-third efficiency, thatâ€™s 4.67 x 10^8 J/sec for the entire Dyson sphere. That sounds like a lot, right? But hereâ€™s the thing â€“ 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.
Thatâ€™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:
' 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
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 â€“ 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 itâ€™s not short term practical, the plan isnâ€™t fanciful. Solar power is about 3.8Ã—10^26 Watts. The gravitational binding energy of Mercury is about 1.80 Ã—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, etcâ€¦)? (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.
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.
(UPDATE: credit due, via Mark. Who acounts for a disturbingly large number of my “neato lookit” posts of late.)
This is incredible – a digital compilation of images from the Cassini probe, no CGI or animation, assembled into incredible breathtaking flybys of the Saturn system. The best part os the third, final sequence where we flyby Titan, Mimas, pass thru the ring-plane, and swoop past Enceladus.
I’ve a photo of me from 1996 as a visitor to JPL (where my friend’s dad worked) in front of the Cassini heat shield. I really need to dig that up… Let’s also remember that the controversy about Cassini being nuclear powered was totally bogus, and use that as a data point for why nuclear power is not the ultimate bugaboo that people assume it to be after the still-unfolding tradegy and disaster in Japan.
I was totally mesmerized by the APOD a few weeks ago:
There are two kinds of antiquity here – one cosmic, the other human. Of course the age of the foreground is insignificant compared to the age of the background, but I confess to being more viscerally awed by the former.
I think it’s impossible to really relate to things beyond human timescales. The idea of something being “ancient” has no meaning if it predates our human comprehension. The Neanderthals disappeared 30,000 years ago, which is probably really the farthest back we can reflect on. When we start talking about human forebears of 100,000 years ago and more, it becomes more abstract – that’s why it’s no coincidence that the Battlestar Galactica series finale set the events 150,000 years ago, well beyond even the reach of mythological narrative.