I’ve been rereading Coming of Age in America, by Edgar Z. Friedenberg, which I first read in the 1960s. It’s a sociological and political study of the culture of American high schools back in the day, based on high school students’ reactions to fictional vignettes, but unlike a lot of sociological literature, it’s written with style and a wry sense of humor; for example, the fictional high school that the author used in his research instruments is called “LeMoyen High School,” which is a clever joke. I didn’t understand all of it when I first read it (I was in my teens then); rereading it, I’ve seen some surprisingly sophisticated content, especially in the final two fictional scenarios.
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I realised I have not posted any updates here for a while. Finished The October Man, the last novella of the Rivers of London series, and I did really enjoy the change of scenery, now everything taking place in western Germany instead of the UK, with the German branch of “magical police” being involved. Really liked the Winter and Sommer coupling solving the case in the wineries of the Mosel.
Now I decided to save some money (for games) and I booked the next book of The Witcher on my to-do list, Baptism of Fire. Early days, but like all of Sapkowski’s book, it is far from disappointing.
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Just finished this. Read about 2/3 of it in the past week. Very good stuff - a nice twist on recognisable fantasy tropes. Enough familiarity that there’s a solid base to work from and it’s not loading you down with nonsense worldbuilding that gets in the way of the story. But there’s enough originality that it doesn’t feel cliche or just a retread of something that’s been better done before.
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Having a little spare money, I’ve picked up something I’ve wanted to have for years: James Madison’s notes on the constitutional convention, taken during the actual meetings. These are interesting because they show how the convention got to the system we have, often considering several other arrangements before settling on the present one; and because some of those proposals could be the starting point for alternate histories. And also, it lets me see the part played by men whose names are scarcely remembered now except by historians, but who made important contributions to the debates, such as James Wilson and George Mason.
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I’ve just been pointed to Hitler’s Uranium Club, the transcripts of recordings of captured German physicists at the end of WWII. Dense, but I think it’ll be well worth it…
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I have been reading SOONish, a book of futurological speculations by Dr Kelly Weinersmith and Zach Weinersmith. I’m giving up on the book halfway through the first substantive chapter because I have been irked by several poor and misleading explanations and have now hit a definitely false statement. If I find the work in error when it is reiterating a subject that I know about, how can I trust it when it tells me something that I don’t know?
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That’s one reason why I don’t engage much with most journalism any more: any time I’ve read a report about a thing I’ve been involved in or a subject I know something about, it has been substantively wrong (not just in details, but giving an incorrect impression of what happened overall). (The other is that I find it very depressing, and while I don’t suffer from clinically significant levels of that, I have a much better life if I avoid things that I know will make me unhappy.)
I didn’t spot any actual errors in the book and given Zach’s comments elsewhere they’d probably be glad to know about them.
I just finished the third Rivers of London book, Whispers Underground. I’d say it’s a return to form after a weaker second entry for the series. So I’m in for the next book now.
Didn’t manage to get through The Goblin Emperor before semester started back though, so it’ll now be on hold for awhile 
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Discussing space elevators, they state that “Once you reach 300 miles up you’re in Low Earth Orbit, like most satellites”. But LEO is a trajectory, not an altitude, and at altitude 300 miles on a space elevator you’re about 8 km/sec too slow to be in LEO.
A big issue with a space elevator is that you can’t get off much below GEO without needing a lot of tedious and expensive rocketry when you do. But any plausible climber is going to take a long time to reach GEO.
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I’m no expert, but wouldn’t a more charitable interpretation be that 300 miles up is a typical altitude for a LEO trajectory of many satellites?
It’s sloppy, and incorrect when read literally, so I think that’s fair enough. (But then I don’t regard suborbital hops like SS1 or the early Mercury flights as “being in space”, which isn’t logically defensible.)
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Maybe. But I’m not reading the book to judge the authors, I’m reading it to learn things that I don’t know. When I come to a chapter about something that I don’t already know I won’t know when I have to interpret charitably, and I won’t know how to do so.
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I have just read Zach Weinersmith’s Shakespeare’s Sonnets Abridged Beyond the Point of Usefulness, which I enjoyed. Each sonnet is epitomised by a couplet in an appropriate meter, sweeping away the excess of pointless beauty and cleverness. Bravo!
I suppose I understand the concern, but I know nothing about earth orbits and it seems to me that LEO couldn’t possibly be referring to the space elevator itself, otherwise there wouldn’t be any difference between LEO and GEO. Right? I can understand the intended meaning regardless of slightly sloppy editing so it just doesn’t seem like something I would write off the rest of the book for. But I appreciate my expectations and requirements are different.
It is a common misunderstanding that “LEO” means “at this particular height”, rather than “at this particular height and velocity”.
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So, a quick aside if you will all indulge me: I have a degree in physics and worked at a private R&D firm for 12 years. One of my responsibilities while at said business was helping design satellite components… so I never did the rocketry calculations myself, but we did work with NASA and JPL and all that stuff, so I am pretty comfortable with orbital stuff.
Last week, I had to call my father (a better physicist than I am) to discuss Geosynchronous Orbits. For those of you unaware, a Geosync orbit is a very particular height (36,000 km) in which an object rotates at exactly the same speed as the Earth rotates underneath it.
But here’s the thing: as mentioned by Roger mentions, orbits are height+velocity. Ergo, there should be a closer orbit which works with a lower velocity, and a higher orbit at higher velocity, both of which would rotate at the same speed as the Earth.
But.
The higher orbit at higher velocity will reach an escape velocity (ie: it’s moving too fast for the Earth to continue to hold it in place), and the lower velocity at a lower orbit will degrade (the Earth will pull it out of orbit). Fascinatingly, the equations prove this is mass independent! It doesn’t matter* how heavy the object you put in orbit, it has exactly one height to be at exactly geosynch.
Blew my mind. Also resulted in me having to adjust my novel to compensate. 
Anyway. Back to your regularly scheduled discussion.
*Obviously, sufficiently large masses will start to drag the Earth into orbit around it, and since there is exactly one distance that the orbit holds, any object with size will have portions of it too far from the orbit and some that are too close so you will still need to correct the orbit eventually.
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Well, not exactly.
In a circular orbit, v = sqrt(GM/r) (G = gravitational constant, M = mass of Earth, r = radius of orbit, v = tangential velocity). (The higher you are, the slower you go.)
The orbital period is the time taken (at speed v) to traverse the circumference of the circle (2π.r) that is the orbital path. T = 2π.r/sqrt(GM/r) or to simplify T = 2πsqrt(r³/GM). (The higher you are, the much longer you take.)
So if we want to set our orbital period to be 24 hours, so that we can hover above a point on the Earth’s equator, there is only one altitude where it’ll work. Nothing to do with escape velocities or orbital decay; even being a little bit off that altitude will give you progressively accumulating drift. (In reality, random perturbations will get you some of this anyway, which is why you need an ongoing ability to manoeuvre even for a comsat that’s meant to stay in the same place.)
Happy to go into more detail elsewhere if you’d find it helpful. But note that the geostationary orbit is over the equator, and if you want to see the thing from high latitudes you run into problems. The Soviets developed satellites in so-called Molniya orbits, highly elliptical 12-hour (ish) orbits where the satellite sits high in the sky over the place you care about (so it’s moving relatively slowly and you can point an antenna at it), then swoops low round the other side of the Earth.
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I think what you are saying and what Marx is saying are corollary propositions.
You are saying that in a circular orbit at radius r, you will have a certain orbital speed; and that at geosynchronous altitude R, that orbital speed will be precisely that needed to complete an orbit in 24 h. If you are at a lower altitude, your orbital speed will be higher, and also the circumference will be less; if you are at a higher altitude, your orbital speed will be lower, and also the circumference will be greater. So at lower altitude you will take less than 24 h to complete an orbit, and at higher altitude you will take more.
But that is assuming that you are in a circular orbit.
Suppose you ARE at a higher altitude, but you don’t stay at circular speed; instead you increase your speed, perhaps even sufficiently to be (approximately) geosynchronous. That combination of altitude and speed does define a possible orbit. But it won’t be a circular orbit. As you increase speed, the orbit will become an increasingly eccentric ellipse. If speed reaches SQRT(2) times circular speed, it will become a parabola: You will never return to your initial altitude—that is, you’ll be at escape velocity. And that is what Marx is describing. His account is oversimplified in that it doesn’t take into account the range of speeds between circular speed C and SQRT (2) x C where you have an eccentric orbit; but the basic approach of looking at the need for higher speeds for geosynchronicity is perfectly consistent with what you’re saying.
(I’m happy for him, by the way, that he got to see the beauty of the physical analysis. As Pope said,
Nature and nature’s laws lay hid in night.
God said, Let Newton be! and all was light.)
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The conclusion is the same (“if you aren’t at the right altitude you can’t do geosync”) but I felt that the analysis of the reasons why could lead one astray.
It did not last: the devil, shouting “Ho,
Let Einstein be,” restored the status quo.
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Funny enough, this seemed obvious to me, especially considering the lower orbit option. To be geosynchronous, it would have to have a lower velocity, but that would then invalidate the possibility of maintaining an orbit, as the pull of gravity would bring it down. And the same goes for a higher altitude/higher velocity model, but escaping Earth’s pull in this case.
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