Creating the EHT was a formidable challenge which required upgrading and connecting a worldwide network of eight pre-existing telescopes deployed at a variety of challenging high-altitude sites. These locations included volcanoes in Hawai`i and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.
The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3 mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a sidewalk café in Paris.
50 years ago on Christmas Eve (Dec 24, 1968), the astronauts aboard Apollo 8 took an amazing series of photos of the rising earth behind the limb of the moon, while in orbit. The first photo was black and white, and subsequent ones (with the earth having risen farther from the moon horizon) were color, and now with some digital magic, these are combined into one image. Glorious.
“Oh my God, look at that picture over there! There’s the Earth comin’ up. Wow, is that pretty!” — Astronaut Bill Anders, Apollo 8
a large international team of researchers is weighing in with another vote for comet. The argument, says the team, is based on the odd behavior of ‘Oumuamua, which appears to have been accelerating away from the Sun.
The researchers then modeled an additional, non-gravitational effect based on ‘Oumuamua’s distance from the Sun. If the Sun was having an additional influence on its motion, then this should be able to compensate for it. It worked, in that an additional acceleration based on distance from the Sun could get ‘Oumuamua’s calculated motion to better match the observations. Quite a bit better, in fact, as the authors say that their modified equation “corresponds to a formal detection of non-gravitational acceleration with a significance of about 30?.” Typically, only five sigma is needed to call something a discovery.
Kudos to John Timmer for playing this one straight. I would not have been able to resist.
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.
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.