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  1. #1
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    Errors in Death from the Skies

    I'll leave it to the BA to start the thread List of errors and typos II, after we vet them.

    Page 53: In the footnote, after discussing the fact that the Earth's North Pole is actually a south magnetic pole (that's why a magnet north pole points North), he says:
    And oh--it gets worse still: the poles on a bar magnet are actually labeled for the pole they attract.
    That's just not true, except as noted for the earth's poles. This could be just an instance of that confusion. But he goes on:
    So the pole labeled "N" on a bar magnet actually tries to point to another magnet's north pole (it "seeks" the north pole), so the pole labeled "N" is actually the south pole.
    So, that's clearly wrong.
    Confused yet? Yeah, like magnetisim isn't already hard enough to understand.
    Gotta agree there

    I also object to the section heading on the bottom of page 29: "Comet What May" -- that's just wrong!

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    I want this book.

    Pending my having the opportunity to read the book, I'm not sure he's wrong on the magnet pole stuff. Perhaps what the BA meant was that the N-labeled pole on a magnet seeks the actual north pole of another magnet (which might be labeled 'S').

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    Quote Originally Posted by geonuc View Post
    Pending my having the opportunity to read the book, I'm not sure he's wrong on the magnet pole stuff. Perhaps what the BA meant was that the N-labeled pole on a magnet seeks the actual north pole of another magnet (which might be labeled 'S').
    Doesn't matter because the north pole on magnets is labeled N. Most of them anyway.

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    I take--2 steps forward
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  5. #5
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    Wow...if that's the only error (so far) it must be a decent book! If only that were true for every science textbook out there!

    Must...get...one...

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    It's a very good book. Highly recommended.

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    so is the north pole the equivalent of a north pole on an ordinary magnet?
    And the the N on a compass is really the south of its own magnet(ie th compass magnet)

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    Wikipedia: North Magnetic Pole

    In physics, all magnets have two poles that are distinguished by the direction of the magnetic flux. In principle these poles could be labelled in any way; for example, as "+" and "−", or "A" and "B". However, based on the early use of magnets in compasses they were named the "north pole" ("N") and the "south pole" ("S"), with the north pole being the pole that pointed north. When it was later understood that opposite poles attract, a terminological dilemma arose: the Earth's North Magnetic Pole and the pole of the magnet that was attracted to it could not have the same polarity. By convention, the "north pole" of a magnet remained defined as the one attracted to the Earth's North Magnetic Pole, and by this definition the Earth's North Magnetic Pole is physically a magnetic south pole. Conversely, the Earth's South Magnetic Pole is physically a magnetic north pole.
    Wikipedia: Paula Abdul

    [...] and "Opposites Attract".
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
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    I learned (probably back in grade school) that the "N" on a magnet stood for "north-seeking pole", and "S" stood for "south-seeking" pole. That pretty much keeps it all straight in my mind.
    I may have many faults, but being wrong ain't one of them. - Jimmy Hoffa

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    Quote Originally Posted by Extravoice View Post
    I learned (probably back in grade school) that the "N" on a magnet stood for "north-seeking pole", and "S" stood for "south-seeking" pole. That pretty much keeps it all straight in my mind.
    Yes, that's a development that probably has contributed to the confusion. The north pole of a magnet seeks the North Pole of the Earth--but that means that the North Pole of the Earth is a south magnetic pole. In other words, the North Pole of the Earth would be labeled "S" if it were a bar magnet. That explains the nomenclature, though.

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    There was a thread about the nomenclature for magnetic poles in General Science.

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    On Page 7, when describing what it would be like to be too close to an asteroid impact:

    "Every tree was casting two distinct shadows"

    Haven't we learned from the moon hoax debacle that if there are two light sources shining form different directions, then there will be two weak shadows and a strong distinct shadow only where they overlap?

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    I've finished the book, and I predict that it will soon become a must-have on the talk show circuit. Phil, gird your loins, and lay in a supply of puns and pithy bon mots, I think you're going to get your chance at Colbert. But, back to the OT.


    Page 36, DFTS; it says a million Earths would be needed to fill the Sun's volume, which is a good swag since the Sun is a bit more than a hundred times the diameter. However, down the page, it says 300 Earths would fit inside Jupiter. That's true, but Jupiter has eleven times the diameter of the Earth, so more than four times that many would also fit. The mass of Jupiter is about 300 times the mass of the Earth, maybe that figure slipped in there somehow.

    Page 73, DFTS; it says "Using laws of physics established by the astronomer and mathematician Johannes Kepler in the seventeenth century, astronomers could determine the masses of the stars in binaries, ..." Determine masses? Shouldn't that be the laws of Newton?


    Quibbles

    Page 145, DFTS; in a footnote, it says "tidal force" is a misnomer, because it is "not a force, but a change in force." I'm not clear what distinction is being made there.

    Page 205, DFTS; describes the red giant Sun swollen to 100 times its present radius. It mentions that the gravity at the surface will be less than 1 percent of Earth gravity.
    the Sun's luminosity increases by 2,400 times. Any square inch of Sun will be blasting out 2,400 times as much radiation as it did before the Sun swelled up. This light has momentum that it can transfer to a particle on the surface, giving it an upward kick.
    The square inches are measured at the current radius, I guess, before and after. By the time it gets to the surface of the red giant, the radiation per square inch will be 1/10,000 of that, right? But, wouldn't luminosity be related to the surface?

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    Page 120:
    "But GRBs are beamed. Their luminosity does not decrease as rapidly with distance [as compared to supernovas]". Surely the intensity of a GRB beam falls with the square of the distance, just as the light from supernovae does. The difference lie in the initial focusing of energy in one direction.


    Phil tells us not to worry about black holes, because they are so far away, but I would worry about Cygnus X-1, which is at 6500 light-years on page 150 and has approached to a mere 1600 light-years on the next page.

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    Quote Originally Posted by drhex View Post
    Phil tells us not to worry about black holes, because they are so far away, but I would worry about Cygnus X-1, which is at 6500 light-years on page 150 and has approached to a mere 1600 light-years on the next page.
    It just missed us on page 152.

    But good catch, going back to look at that I caught my only grammar glitch (p.149): "a 7-solar mass star would have been be easy to detect." Normally, when I read for pleasure (and I did), my grammar tolerance is set at 11.


    Other Quibbles:

    Page 18, DFTS; "This striking discontinuity, called the K-T boundary (unfortunately, the term C-T was already being used by archaeologists)..." That may be true, I dunno, at the time I thought CT scans were still known as CAT scans. The K stands for Cretaceous because it starts with a K in German, and C stands for Cambrian, I think.

    Page 199, DFTS: in the footnote: "Other factors in the Earth's temperature include its distance from the Sun, its ability to shed heat (radiating it away at night), and even how rapidly it rotates." Wouldn't it radiate away during the daytime as well?

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    Quote Originally Posted by hhEb09'1 View Post
    Page 18, DFTS; "This striking discontinuity, called the K-T boundary (unfortunately, the term C-T was already being used by archaeologists)..." That may be true, I dunno, at the time I thought CT scans were still known as CAT scans. The K stands for Cretaceous because it starts with a K in German, and C stands for Cambrian, I think.
    I'd heard that too (about CT already being used {though it was geologists, not archeologists - for one thing there are no archaeological remains before about 100-125,000 y.a.}), and had also heard about Cretaceous starting with K in German... but after a number of Google searches, it turns out we're all wrong.

    The K is for Kreide, chalk, which described the layers of the first identified sediments. In fact if you look at these results, there's a number of references to the Jura-Kreide boundary and the Kreide-Tertiar boundary.

    <--- checks off "learn something new" box on todays to-do list

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    Quote Originally Posted by hhEb09'1 View Post
    Page 205, DFTS; describes the red giant Sun swollen to 100 times its present radius. It mentions that the gravity at the surface will be less than 1 percent of Earth gravity.The square inches are measured at the current radius, I guess, before and after. By the time it gets to the surface of the red giant, the radiation per square inch will be 1/10,000 of that, right? But, wouldn't luminosity be related to the surface?
    If the Sun is 100 times bigger, it area will be 100 x 100 = 10,000 times bigger than today. However, on page 204 it says the luminosity will be 2,400 times as great. That means each square inch will be (2,400)/(10,000) or roughly 1/4 as luminous as today.

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    Quote Originally Posted by Ze_Kraggash View Post
    If the Sun is 100 times bigger, it area will be 100 x 100 = 10,000 times bigger than today. However, on page 204 it says the luminosity will be 2,400 times as great. That means each square inch will be (2,400)/(10,000) or roughly 1/4 as luminous as today.
    Yes, I think that was the point I was trying to make. I'll have to go back to the book to remember the context...

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    Remember that Luminosity per square inch varies with temperature to the fourth power, following the Stefan-Boltzmann law. The red giant sun will have a cooler surface temperature than its current temperature, and so the luminosity per square inch will be less then than it is now.

  20. #20
    The only problem I have is I do not have it yet, ordered it through JREF. Hopefully I can get in contact with them tomorrow about.(Having some minor tech problems at the moment.)
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    How does the math for mass losses due to stellar wind work for the sun?

    Page 217, as the sun goes into its second giant phase
    "..the stellar wind will be back with a vengeance. It lost 28 percent or so of its original mass the first go-round; this time it loses more than 60 percent of what is left."

    So, originally 100 units of mass, then down to 72 after the first giant phase and then losing another 0.60 * 72 = 43 units, meaning 72 - 43 = only 29 units left. Add to that losses due to production of light. How can the remaining core then have "about half the mass of the original sun" [page 218] ?

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    I have to say that a north magnet points to the north pole necessitating that one of those two north poles is actually a "south" magnet makes perfect sense, but is something I've never even considered before.

    At least now I know which one is a misnomer (and knowing is half the battle! GO JOE!)

  23. #23
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    On more nitpick in DFTS, in the table on page 299:

    Phil lists nearby supernovas, nearby GRBs aimed at us and wandering black holes as "not preventable" while an Alien Attack is preventable if we colonize the galaxy first. Well, if we colonize the galaxy first, then we can survive the three first events (even though we still couldn't <i>prevent</i> them, so Phil is right after all.)

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    In the cosmic blowtorch chapter (GRB's), Phil describes a scenario involving a GRB from Eta Carinae, which is 7500 light-years from Earth. He says that the flood of subatomic particles would arrive "hours" after the gamma ray burst. Gamma rays travel at the speed of light and if the particles show up mere hours later, they must be travelling at about 0.9999998 times light speed (I assumed 10 hours later). Is that right? Seems high for something with mass.

    In the supernova chapter, he states that particles will be blasted out at "many thousands of miles per second".

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    LHC accelerates protons to 99.999999% of lightspeed, according to wikipedia.

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    Errata:

    pg. 50: The solar corona is millions, not billions, of degrees.

    pg. 53: The footnote on magnetism is wrong. Either the Earth's "N" pole is a magnetic S pole, or the "N" pole on a magnet is a S pole. Can't have both. The first is usual, in my experience.

    pg. 218: A white dwarf doesn't shine at "thousands of times the luminosity of the present-day Sun". Even at a temperature like the one mentioned, its luminosity would be about 1 solar luminosity (its surface brightness would be thousands of times higher, though).

    pg. 221: white dwarfs don't cool to invisibility after a few million years. I believe standard estimates have them still hotter than the Sun (photosphere) after a billion years. ("Invisibility" is relative, of course - even an O star is invisible at 5 Gpc - but there is no substantial change in luminosity after only a few million years.)

    pg. 244: first full paragraph, I think it should say that the galaxy's magnetic field is good at deflecting intergalactic cosmic rays, not galactic.

    pg. 272: The Grand Unification Epoch involved the unification of the strong and electroweak forces - it didn't include gravity.

    Response to some other posts:

    geonuc: Astrophysical objects like quasars and GRBs regularly accelerate particles to ultrarelativistic speeds. The neutrinos from SN1987A arrived before the light, even though they were emitted only hours earlier. (This supernova was about 150,000 light years away.)

    hhEb09'1: Radiation energy loss depends on the difference in effective temperatures of the planet and of the sky. During the day, the sky is hot, during night, it is not (although hotter with cloud cover than without). Thus, it gets colder at night, and colder in winter due to longer nights and lower sky temperatures during the day.

    The tidal force distinction has to due with the fact that "tidal force" isn't a fundamental force, it's simply the result of gravity (the actual force) being different in two spots. Calling it a tidal force is just a convenient shorthand.

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    I haven't gotten the book yet. I am most impressed with the cover's hi-res image of Betelgeuse. That is Betelgeuse, right?, or is it Antares?
    We know time flies, we just can't see its wings.

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    I thought the Sun might nearly reach our orbit, thus it would be closer to a 90 deg. arc in diameter.
    We know time flies, we just can't see its wings.

  29. #29
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    Quote Originally Posted by George View Post
    I thought the Sun might nearly reach our orbit, thus it would be closer to a 90 deg. arc in diameter.
    That would be 180 degrees.

    But DFTS is talking about a specific point in the solar evolution, rather than any ultimate result. It goes into a lot of gory details along the way. Everyone should have a copy.

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    Oops. Yes, of course, 180 deg at noon.

    I wonder if the Sun is not an orange giant at 60 degrees?
    We know time flies, we just can't see its wings.

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