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Archive for the ‘Astronomy’ Category
There is a sub-branch of the study of dynamic systems called Catastrophy Theory. Despite the name, it doesn’t deal with earthquakes and tsunamis. Instead, it deals with situations in which perturbed dynamic systems don’t revert when the perturbation is reversed (OK, yes, earthquakes and tsunamis can do that). Raising the price of public transport might well trigger a drop in ridership. Returning the price to the original value might not cause ridership to return to its previous high.
Similarly, Chaos Theory talks about basins of attraction. A chaotic system will tend to move unpredictably within one region, or basin, but if it stumbles upon the right path it might well flip over into a different basin, whereupon it will start moving unpredictably within that one. Attempting to retrace the steps most likely won’t return you to the previous basin because of, you know, chaos. One of the concerns about climate change is that we might drive the Earth’s climate into a new basin of attraction, one that is stable, but inimical to human civilization.
Both of these have some of the attributes of a one-way function. Chaos Theory because finding your way back is so hard, Catastrophe Theory because retracing your steps brings you somewhere else. Think of being on the edge of an overhanging cliff. If you walk towards the cliff long enough, you fall over the edge. If you turn around, once you hit bottom, and walk back the way you came, you don’t end up on top of the cliff, you end up underneath the overhang. Returning to the top requires that you walk the long way around.
Getting hit by a modest sized asteroid is like that. Or a comet.
Over on Next Big Future is a chart showing the threat posed by various sizes of asteroids, should they hit the Earth. Imperial College, London, has a handy calculator, plus a 2.5MB pdf document, providing a little more detail. The ICL simulator is quite a bit more sanguine than is NBF. Their description of a 500m diameter asteroid impact reads like a largish nuclear warhead strike, while NBF considers it a civilization-ending event. Let’s agree that nobody is sure how big of an asteroid strike is needed to cause civilization to collapse, and that we can only guess at the likelihood of that happening within the lifetime of our current civilization. That’s not the problem.
The problem is this. Modern civilization is a one-time event. If it goes away, it isn’t coming back.
Think of what a civilization-ending impact might be like. If a sufficiently large asteroid (or comet) hits in the Pacific Ocean — the most likely event — everything on the Pacific Rim disappears in the super-tsunami. Or maybe it lands in Siberia (the last two did), so we get world-wide firestorms. Wheatever happens, the materials thrown into the atmosphere will likely give us two or five or ten years of nuclear winter. Everybody starves. Well, everybody in First World Europe and Asia and North America. Equatorial peoples are the most likely to survive. Even if there are enclaves in the First World, they’re not likely to include a particularly wide range of technology skills — they’ll be tinkerers, not engineers. I’m not going to go into detail because that’s not what I want to discuss. I’m assuming an impact big enough to destroy all but a fraction of modern civilization while allowing a biggish chunk of humanity to survive. How big of a rock is that? You decide. You want more detail? Read Niven and Pournelle‘s 1977 book Lucifer’s Hammer, then turn it up to eleven.
The question is, what happens when the majority of the survivors of a global catastrophe get knocked back to at best an early 18th Century mode of existence (and at worst an early 8th Century mode), mitigated by a dwindling cache of manufactured goods and a vague memory of what is possible? It took us 250 years to go from the technology of colonial America to our current 21st Century position. Can we do it again? In 250 years? Not likely.
You see, modern civilization is energy intensive. Cheap energy intensive. Which means petrochemicals. The reason it’s so hard for us to give up our oil dependency is that oil is the only resource that checks all the boxes for energy density, transportability, and so forth — here’s a pair of comparison tables from Do The Math.
More to the point, the movement from a society dependent on 18th Century technology to one that wears 21st Century technology on its wrist requires an enormous amount of energy. So, solar panels can provide energy, but where do we get the energy to go from steam engines to a wafer fab for solar cells? Access to today’s coal resources requires the ability to dig tunnels a thousand feet beneath the ground, or to remove the top thousand feet off a mountain. Most of today’s sources of oil now require high-tech methods to access and process them. Can you spell deep ocean drilling? Hydraulic fracturing? Cyclic steam stimulation? Combustion overhead gravity drainage? The few remaining sources of post-impact easy oil are likely to be used up heating the homes and powering the cars of third-world locals, until those resources are also gone. I’d be off on a rant about the last peasants using the last of the oil, if I weren’t pretty sure that at the same time the last Americans and last Europeans weren’t burning the last books, to keep from freezing.
This is not even a rant about our using all the pre-impact oil. That’s a sunk cost. We thought we had good reasons for doing what we did, at the time we did it, and now we are where we are. This is a warning that we only get one shot at creating a viable space-based civilization, one that’s independent of planetary resources, and dispersed enough to keep us safe from the real dinosaur-killer rocks that are out there. I’m not the first to raise this issue. I think that Niven and Pournelle actually did that, thirty or forty years ago. I’m just taking advantage of recent events to casually drop the idea into our Thanksgiving dinner conversations.
Went out to watch the Perseid meteor shower. I unthinkingly set up my deck chair directly underneath a cloud, and no amount of switching its position did anything to improve the view. Pity that. I had my catcher’s mitt and everything.
So, tonight is May Eve, when bonfires are burned, and maybe witches also. Walpurgis Night is, of course, a Christianized version of Beltane, the Celtic celebration of the start of summer, when bonfires were burned and people and cattle walked between them for purification, and witches would dance all sky-clad (or sometimes they would dance in shifts, because there wasn’t room for all of them). Tomorrow is May Day, dear to a certain generation as the date for large displays of new equipment in Red Square. It’s also, depending on how the moon tends, the first day of Ðrimilcemonað, the month that Anglo-Saxon cows had to be milked three times a day.
This month, on the second of May, 2013, the moon is a waning Last Quarter Moon. If you go out at sunrise and stand on the Earth’s terminator, you can look up at the Moon’s terminator. This means the Moon is directly ahead of us in our orbit, which means that where the Moon is, is where the Earth will be, three hours later.
Patrick Moore was, in his day, the most famous amateur astronomer in England, if not the world. We lived in England in the early 70’s, the heyday for the US space program. Whenever something interesting was happening, Moore was the man the BBC would turn to to describe it all to us. He died yesterday, aged 89.
In a NYT article, by way of Boing Boing, columnist Errol Morris, asks for your opinion on a statement by David Deutsch about the asteroid threat to Earth:
…we live in an era of unprecedented safety: the twenty-first century is the first ever moment when we have known how to defend ourselves from such impacts.
It’s interesting, in that the survey asks not only for your opinion, but your level of confidence in that opinion.
I’ve given my opinion, and I’ll talk about it here, in a follow-on essay, in a couple of days. That will give you time to vote, and it will separate this entry from all possibility of spoilers.
As I said in more detail in my last post, we have arranged a performance by Solar Eclipse, on tour for one day only, Asia, Pacific, and the US. However, the situation looks bad for the NENW performance (scheduled for 5:30PM), with extensive cloud cover threatened. And it turned out to be true.
The cloud cover remained until nightfall, and the satellite image wasn’t much help.
In honor of Eliza Doolittle Day, Sunday, the 20th of May, we are staging an annular eclipse of the Sun. In the NENW it will start about 5:30PM. This description, from the LA Times, is pretty good. Here’s a simulation for Washington State (the full page lists all the states…worth listing)
Easiest setup for viewing is
[–box with white paper…..cardboard with pinhole–|…..O sun
you, looking this way <…
The pinhole projects the image of the sun on the paper. The longer the distance twixt cardboard and paper the bigger, and dimmer, the image.
It's safe, because you are looking towards the box and away from the sun. Don't look at the sun directly, you'll put somebody's eye out.
Back in 1964, RAND scientist Stephen H. Dole wrote a book titled “Habitable Planets for Man“. In it, he made a serious effort to first, define what was needed for a planet to be habitable, and second, to estimate the number of stars that might actually support such planets. Today, we had our first good test of his ideas. (more…)
That’s “After Litha”. The Anglo-Saxons — who spoke Old English (although they probably didn’t call it that) — occupied and ruled Britain from about 449 to 1066. They used a solar/lunar calendar, which does not work well with the passage of the months of the modern calendar (although Bede mapped them that way). Two of their ‘months’ were doubled: Aere Yule/Aefter Yule fell on either side of their Yule festival, sometime around the end of December (or the winter solstice, or Christmas). Aere Litha/Aeftera Litha came six months later, close to the end of June/beginning of July. Since it is likely that the Angles and the Saxons and the Jutes (oh, my) started a month at the first crescent of the new moon, this year we might expect Aeftera Litha to begin on the 1st or 2d of July. Just in case you were wondering, next month, August, is Wéodmónaþ, or Weed Month. Since the seasons of England are much like those of the coastal NorthWest, all of my Portland reader can take comfort in knowing that others have had the same problems.
Anglo-Saxon history is a topic for another post, but I’ll just note that you can get an idea of the scale of their achievement by adding a thousand years to an A-S date, to map it into more modern history. So they arrived in England at the invite of Vortigern in 449 (->1449 almost fifty years before Columbus) and were destroyed in the Battle of Hastings in 1066 (->2066, over fifty years from now). This country has a way to go before we better their record.
Having just gotten on an add pictures jag (thanks Kurt), I decided to test if, besides being aesthetic, they’d encourage people to read something they might not otherwise. In the best tradition of science, I thought I’d run a quick experiment. My hypothesis, H1, was that people would be entranced by the pretty pictures, and click on the link while in a trance state. My null hypothesis, H0, was that it wouldn’t make a difference, since nobody reads this blog anyway, except a few of my friends (Hi Sandy), and HOTD fans.
I decided to use my AAVSO post (scroll down two, past Three Wolves). I originally put it up on March 24th, and over the course of the next week it got exactly two views. Should be really easy to measure growth from that baseline. So I found the picture that went with the blog post that inspired me, and updated the article to include it on the main page, right above the “Read the rest of this entry” link. Then I sat back to let the data roll in.
Result one week later: two more views. No change.
Now, no change is the assumed state of the world. Most things we do don’t really change the world, not even within our own restricted circle. If we are to accept a hypothesis as coming from a good model, we have to demonstrate that our action made a difference. In this case, it didn’t, at least, not within the parameters of our experiment. I am reminded of two aphorisms from my youth:
1. Intelligence is our last defense against wishful thinking. Replace Intelligence with Statistics and you have something applicable to the wider world. In passing, I would note that Intelligence is capitalized for more reasons than just starting a sentence. I am talking about the formal discipline.
2. How badly you want something to be true has absolutely no impact on whether it is true or not. You build your model, you draw your hypothesis, you run your test. The universe tells you if you got it right.
Google and I, we don’t either of us have a source for the above quotes.
Or not. Depending on which rule you use. You see, according to the latest reinterpretation, most seasons have only three full moons (early, mid, and late). This will be the third full moon of four this Autumn, and so is called a ‘blue moon’ so that the fourth and last full moon of Autumn this year (which beats Winter in the door by 15 hours) can still be called the Late Autumn Moon.
So far, all the sources and commentaries appear to be based on 20th Century US sources (yes, they claim ancient monastic traditions, but, as the reporters for the Anlgo-Saxon Chronicle used to say: Vellum, or it never happened).
Not the game, the real thing. Full moon at Autumnal Equinox. Here is a writeup. It’s tonight, Wednesday, so get out there and look. Note that we are only a couple nights past the closest approach of Jupiter to Earth in about 40 years, so that bright star next to the moon is pretty much as big as it gets.
In the modern recreation of our supposed Celtic past (and who doesn’t yearn to be Irish?) this is the festival called Mabon, and for the Japanese, it is しゅうぶんのひ. In the Anglo-Saxon lunar calendar, this full moon would probably signal the boundary between Wéodmónaþ (weed month) and Háligmónaþ (holy month)*.
We haven’t had a hummer at the feeder for a full week now, so I guess it’s time to bring them in.
*This is a correction, I was at the wrong month boundary.
Tonight is a first quarter, or waxing moon. As seen from Earth, it’s a half moon, and thereby hangs a tale.
When you look at a half moon, one that looks like this: D , you are looking at the sunrise line, or terminator. Yes, you can see the terminator if you look at a crescent moon, or a gibbous moon, but it’s only when you are directly over the sunrise line that you see that kind of a half moon. When you look at the moon at your local sunset (about 19:00 PDT in the Summer) you are standing on the sunset line of the Earth, also called the terminator. If you think about it, the only way this can happen is if the moon is directly behind the Earth in its orbit around the Sun. Go do a drawing. you have the moon and the Earth in line, like this: o O –> with the arrow indicating the movement of the Earth in its orbit. To complete the picture, the Sun would be off the top of the page, and the bottom half of those circles would be dark.
Now, the Earth travels about 29.6km/sec in its orbit around the sun. And the moon, on average, is 382,500 from the Earth. (Bear with me here, the math is almost over). So, the Earth covers the Earth-Moon distance in about 3.5hours.
That means that when you look at a First Quarter Moon, at sunset, you are looking at the very spot in space that the Earth was at, 3.5 hours ago. In the morning, should you be up early enough to see a Last Quarter Moon at local sunrise, you will be looking at the very spot in space where the Earth will be about the time you sit down for your pre-luncheon snack.
Go out tomorrow evening and try it.
Updated to make timeless.