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The Bad Astronomer
2002-Apr-16, 04:44 PM
Folks:

The list below contains the errors and typos that I know about in the book. A lot of those have already been talked about on this board, and some I found on my own.

If you know of any more, please add them to this thread. If/when we go to a second printing, I want to make sure I can correct as much as possible. BROAD HINT: hurry. /phpBB/images/smiles/icon_wink.gif


Bad Bad Astronomy:
Errors to fix in the second printing


1) Page 5, pp1, typo: “Their home on the web is one of the most populat sites on the planet.”

Change to: “popular”

2) Page 16, pp1, error: “… the yolk is really the embryo of the chicken, and shouldn’t get jostled too much…”

Change to “… the yolk is the embryo’s food, and shouldn’t get jostled too much.”

3) Page 29, pp4, typo: “…people think is a really long time…”

Change to “…people think it’s a really long time…”

4) Page 44, diagram, error: change diagram comment from “at noon” to “Sun high in sky”, and change “sunset” to “Sun on horizon”

5) Page 49, pp4, error: “…amounts to only a 4-degree Celsius (roughly 6 degrees Fahrenheit)…”

Change to “…amounts to only a 4-degree Celsius (roughly 7 degrees Fahrenheit)…”

6) Page 49, pp4, error: “…Maine, where the seasonal change in temperature is more like 30 degrees Celsius (80 degrees Fahrenheit)…”

Change to “…Maine, where the seasonal change in temperature is more like 44
degrees Celsius (80 degrees Fahrenheit)…”

7) Page 99, pp4,error: “…Einstein won his Noble prize for this work and not his much later work on relativity.”

Change to “…Einstein won his Noble prize for this work and not his work on
relativity.”

/phpBB/images/smiles/icon_cool.gif Page 127, pp2, typo : “Nascar”

Change to “NASCAR” (it’s an acronym)

9) Page 129, pp3, error : “Even though it outweighs the Moon by a factor of 25,000…”

Change to “Even though it has 25,000 times the Moon’s mass…”

10) Page 134, pp3, error : “…can be as high as 100 kilometers per second (80 miles per second)…”

Change to “…can be as high as 100 kilometers per second (60 miles per
second)…”

11) Page 137, pp3, error : “In every movie or television program I have ever seen, without exception, small meteorites….”

Change to “In practically every movie and television program I have ever seen,
small meteorites…”

12) Page 144, pp1, typo : “Curtis Shapely”

Change to “Harlow Shapley”
Note: last name was spelled incorrectly and first name was wrong.
Also, remove entry for “Curtis Shapely” in index, and add this reference to
“Harlow Shapley”

13) Page 160, pp4, error : “In 1957 the United States…”

Change to “In 1958, the United States…”

14) Page 163, pp4, error : “…dealing with the landing of the LEM, the odd-looking contraption…”

Change to “… dealing with the landing of the Lunar Module (or LM), the odd-looking contraption…”

15) Page 163, pp4, error: “LEM”

Change to “LM” in both instances

16) Page 165, pp2, error: “LEM”

Change to “LM” in both instances

17) Page 167, pp1 and pp2, error : “LEM”

Change to “LM” in both instances

18) Page 168, pp4 and pp5, error : “LEM”

Change to “LM” in both instances

19) Page 176, pp1, error : “…to those by the ancient Greek, Pliny the Elder.”

Change to “… to those by the ancient Roman, Pliny the Elder.”

20) Page 192, pp2, error: “That friction takes energy away from the Earth-Moon system, slowing the gears a bit. In the end, that energy comes from the energy of the Moon’s orbit. As that energy is sucked out by the Earth’s oceans, the Moon slows in its orbit, and as it slows it pulls farther away.”

Change to “That friction takes energy away from the Earth, slowing its rotation,
and gives it to the Moon in the form of orbital energy. When the orbital energy of
an object is increased, it moves into a higher orbit, so the Moon’s increased
orbital energy means the Moon moves away from the Earth. The increased
distance also means The Moon slows its orbital speed as well.”

21) Page 212, subheading, typo : “The fault lies not in the stars, but in ourselves.”

Change to “The Fault lies not in our stars, but in ourselves.”
Have someone please check this with a definitive source; I have now seen it written both ways!

22) Page 248, pp2, error : “…the average distance between them was 1 kilometer (0.8 miles)”

Change to “… the average distance between them was 1 kilometer (0.6 miles)”

23) Page 251, top line, error : “…when Australopithecus afarensis was the most highly evolved creature on the planet.”

Change to “… when Australopithecus afarensis was the most intelligent primate
on the planet.”

24) Page 270, index, error : “LEM module”

Change to “Lunar Module (LM)”
Also, there are references to the LM on pages 163, 165, 167, and 168. Page 168
was left off of the index.

The Bad Astronomer
2002-Apr-16, 04:45 PM
Heh. The way I listed them, Number 8 got translated by the board into a smilie. /phpBB/images/smiles/icon_cool.gif

Silas
2002-Apr-16, 05:12 PM
Here is at least one version of Julius Caesar that says it the way I learned it... "...not in our stars..."

http://tech-two.mit.edu/Shakespeare/julius_caesar/full.html

I've been trying to find versions that say it the other way... "...not in the stars..."

Silas

ToSeek
2002-Apr-16, 05:43 PM
Change to “…Einstein won his Noble prize for this work and not his work on
relativity.”

Change to "...Einstein won his Nobel prize for this work and not his work on
relativity.”

ToSeek
2002-Apr-16, 05:44 PM
I think in the index Wolsey/Woosley is spelled "Wooslsey". Maybe they were trying to make everybody happy.

The Bad Astronomer
2002-Apr-16, 06:52 PM
Nobel: d'oh!

The index spells it "Woolsley". Sigh.

Keep 'em, coming!

GrapesOfWrath
2002-Apr-16, 07:06 PM
On 2002-04-16 12:44, The Bad Astronomer 21) Page 212, subheading, typo : “The fault lies not in the stars, but in ourselves.”

Change to “The Fault lies not in our stars, but in ourselves.”
Have someone please check this with a definitive source; I have now seen it written both ways!

I found this folio facsimile page (http://perseus.mpiwg-berlin.mpg.de/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.03.0018&query=head%3D%2331) (use kk2r in the goto box, lines 14-15 on page 111), which has it
"The fault (deere Brutus) is not in our Starres,
but in our Selves, that we are underlings."

Most of the versions I've seen include "dear Brutus," but that's probably not important--as even the folio edition has it in parentheses.


Are you still mulling over the thing about the precession and the calendar (http://www.badastronomy.com/phpBB/viewtopic.php?topic=710&forum=9&1)? I'm pretty sure that's wrong.

Also, I think I gave enough good reasons in this thread (http://www.badastronomy.com/phpBB/viewtopic.php?topic=670&forum=9&start=13) that on p.70, ""The time of high and low tides changes every day by about a half hour," should read "The time of each high and low tide is later every day by about an hour."

The Bad Astronomer
2002-Apr-16, 07:25 PM
On 2002-04-16 15:06, GrapesOfWrath wrote:

Are you still mulling over the thing about the precession and the calendar (http://www.badastronomy.com/phpBB/viewtopic.php?topic=710&forum=9&1)? I'm pretty sure that's wrong.



Yes, I just need to confirm that.




Also, I think I gave enough good reasons in this thread (http://www.badastronomy.com/phpBB/viewtopic.php?topic=670&forum=9&start=13) that on p.70, ""The time of high and low tides changes every day by about a half hour," should read "The time of each high and low tide is later every day by about an hour."



I reread that section, and I think I am right, but it needs to be more clear. I've noted that and I'll add it to the list. Thanks.

GrapesOfWrath
2002-Apr-17, 10:57 AM
On 2002-04-16 15:25, The Bad Astronomer wrote:
I reread that section, and I think I am right, but it needs to be more clear. I've noted that and I'll add it to the list.

What will the new phrasing be?

It's also complicated by the fact that not all places on Earth experience two tides per day. That is not just a consequence of coastal geometry--for instance, if the Earth were perpendicular to the ecliptic, and the moon also orbited in the ecliptic, the tidal effect at the North and South poles would be constant, and there'd be no tides there at all.

The Bad Aviator
2002-Apr-17, 02:58 PM
I have one really big aviation nitpik for you. On page 248 you said "Tilting the wings of the plane helps direct thrust to the side, turning the plane." This is wrong. Wings do not tilt, and the force that turns an airplane is its horizontal component of lift, not thrust.

Subsonic aircraft bank via control surfaces called ailerons. These are located on the back of wing near the tip. When you turn your control wheel or stick to the left for instance, the right aileron will drop down, increasing lift on the right wing, and left aileron will rise up, decreasing lift on the left wing. This imbalance of forces causes the aircraft to roll to the left. When the aircraft is banked, its lift is no longer directed straight up, it is at an angle, with a vertical and horizontal component. The horizontal component turns the aircraft, while the vertical component keeps the aircraft in the air. Because the vertical has decreased, the pilot must pull back on the wheel or stick, to increase pitch, and increase the total amount of lift, or the airplane will sink. Supersonic aircraft work in a similiar way, except they don't have ailerons on their wings. They have what is known as stabilators, which are horizontal stabilators (those little "wings" on the tail) which can tilt. To turn left, the left stabilator is tilted up, and right one down. Thrust has nothing to do with either case.

There are some aircraft that have thrust vectoring, such as the F-22. While it gives an airplane a huge advantage in maneuverability, thrust vectoring will not turn an airplane.

I hope this little nitpik of mine isn't taken that badly. I DID enjoy your book, and I can't wait for Bad Astronomy The Sequel.

johnwitts
2002-Apr-17, 07:59 PM
Ah, but what causes lift? There must be a thrust somewhere.

The Bad Aviator
2002-Apr-18, 05:25 PM
Lift is caused my a pressure difference between the top and bottom of the wings.

Wiley
2002-Apr-18, 05:34 PM
On 2002-04-17 10:58, The Bad Aviator wrote:
I have one really big aviation nitpik for you.


Speaking of nitpiks, how can a nit be big? /phpBB/images/smiles/icon_smile.gif

And welcome to the BABB, Bad Aviator.

johnwitts
2002-Apr-18, 07:59 PM
Lift is caused my a pressure difference between the top and bottom of the wings.

...which causes a thrust upwards?

James
2002-Apr-19, 02:47 AM
On 2002-04-18 15:59, johnwitts wrote:
Lift is caused my a pressure difference between the top and bottom of the wings.

...which causes a thrust upwards?


Yep.

Example: Picture two air molecules, one on top of another, right in front of a semi-circle with the flat side facing down. The top air molecule will take longer to travel over the curved surface, right? Because it takes longer, there's less pressure above the semi-circle, or, in the case of an airplane, the wing, than there is below it, which produces lift, or thrust upwards. Thrust is just the movement of the plane through the air.

Donnie B.
2002-Apr-19, 11:20 PM
Actually, James, as I understand it, it's not that it takes the top molecule longer, but that it is forced to move faster; and faster-moving air is lower in pressure than slower-moving air (all else being equal). It's the venturi effect.

However, there's another factor in play, which is often downplayed: the angle of attack. A wing gets lift by displacing air molecules downward... the same effect as when you stick your hand out the window of a moving car and slant the palm upward. Many types of planes get a large fraction of their lift from this mechanism. Some wings are actually symmetrical (no difference in the top and bottom contour).

But I agree with the original nit: the BA was a bit too concise in his description.

(Corrected grammar)

<font size=-1>[ This Message was edited by: Donnie B. on 2002-04-19 19:21 ]</font>

Silas
2002-Apr-21, 12:20 AM
re aircraft thrust/lift, there was a recent dialogue on this in the letters column of Scientific American. Kind of fun, as everyone is, in essence, saying the same thing...differently...

Aircraft get their *unique* thrust from the Venturi effect. Here's the thing: have a friend drive a car along the freeway. Sit in the passenger seat and put your hand out, into the windstream. Tilt your hand at various angles. There is one specific "magic" angle at which your hand is yanked upward. At lower angles, there's some lift. At higher angles, there's quite a lot of lift. But at the one specific angle where the Venturi effect is maximized, there's one WHALE of a lot of lift!

So, yeah, sure, airplanes could fly with wings at 45 degrees up. You'd need a blortload of thrust, but they would fly. But when you set your wings at that "magic" angle, you can fly with much, much less thrust.

*All* lift is supplied by a downward movement of air. But efficient and effective and economical lift is an artifact of the Venturi effect.

Anybody here done any sailing? It's been said that the wind doesn't "push" against the sail, but that it "pulls" around the convex curve of the sail. Another Venturi effect. You could have a perfectly flat, perfectly stiff sail, against which the wind would push. You'd make some progress. But someone with a canvas sail that is bellied to just the right degree will race ahead of you and leave you bobbing in his wake.

Heh... Who says there's no such thing as a free launch?

Silas

Chuck
2002-Apr-22, 04:13 AM
Last word on page 142:

"The sun rose at 6:30 this morning" is less accurate that saying "From my fixed location on the surface of the spherical Earth, the horizon moved below the apparent position of the sun at 6:30 this morning."

"that" should probably be "than".

Chuck
2002-Apr-23, 03:06 PM
Page 213, end of last full paragraph:

For astrology to sell, buyers must not seek out the fundamental principles behind it, because if they do they see that there is none.

Probably should be:

...there are none.

Wiley
2002-Apr-23, 04:40 PM
I gonna have to agree with Chuck on this. "is" is the verb for "none" which can either be singular or plural, depending on context. However "none" refers to "fundamental principles" which is plural.

Score one nitpik for Chuck! /phpBB/images/smiles/icon_smile.gif

GrapesOfWrath
2002-Apr-23, 06:29 PM
I'm disagreeing. I think either is acceptable. In fact, the traditional "rule" is that none is singular.

If the phrase had said "because if they do they see that there is one", then "is" would be correct, right? The antecedent is ambiguous, just as is the number of the word "none".

SeanF
2002-Apr-23, 06:48 PM
I think I'm going to have to go along with GoW on this one (gasp!). The verb for "none" doesn't have to match up with "principles" in this situation - it's independent.

Having said that, I do think "are none" sounds better. After all doesn't ending "Ten Little Indians" with ". . . and then there was none" seem awkward? /phpBB/images/smiles/icon_smile.gif

Wiley
2002-Apr-23, 09:12 PM
On 2002-04-23 14:48, SeanF wrote:
I think I'm going to have to go along with GoW on this one (gasp!). The verb for "none" doesn't have to match up with "principles" in this situation - it's independent.


In my previous post I may have implied I feel more strongly about this than I actually do.

I think either is correct but the plural is preferred. It really doesn't matter that mush. So regardless of what Strunk & White and others pundits may prefer, I shan't lose sleep over this.

Donnie B.
2002-Apr-23, 11:39 PM
In that sentence, "none" is a pronoun standing in for "no principles". "are none" is correct.

-- DB, the son of an English teacher

Wiley
2002-Apr-23, 11:54 PM
On 2002-04-23 19:39, Donnie B. wrote:
In that sentence, "none" is a pronoun standing in for "no principles". "are none" is correct.

-- DB, the son of an English teacher


/phpBB/images/smiles/icon_razz.gif

(And no, I'm not mature. /phpBB/images/smiles/icon_smile.gif)

Roy Batty
2002-Apr-23, 11:57 PM
I think are sounds better.

Gosh, if we're reduced to this there can't be that many more nitpicks? /phpBB/images/smiles/icon_smile.gif

_________________
N6MAA10816

<font size=-1>[ This Message was edited by: Roy Batty on 2002-04-23 19:59 ]</font>

Andrew
2002-Apr-24, 12:17 AM
How about this:

"because if they do they see that there aren't any."

Chuck
2002-Apr-24, 03:38 PM
Let's start a new thread for each sentence in the book in which to discuss how to phrase them better.

Silas
2002-Apr-24, 03:50 PM
On 2002-04-24 11:38, Chuck wrote:
Let's start a new thread for each sentence in the book in which to discuss how to phrase them better.



"...how to phrase them best."
(or "...how best to phrase them.")

It's fun, actually; there are BBSs for grammar perfectionists!

Silas

BADad
2002-Apr-25, 12:54 AM
Page 216 - line 11
"consistant" should be "consistent".

GrapesOfWrath
2002-Apr-25, 06:39 PM
Well, as long as we have the tide issue still open, I'd like to mention another fine point. On page 73, the book mentions that the tidal force of the Earth on the moon is 80 times that of the moon on the Earth. That is a result of the Earth being 80 times larger than the moon.

However, it depends upon what is meant by tidal force. Usually, it means the difference in gravitational force from one side of a body to the other. In that sense, it acts like the derivative of gravity, so it is proportional to the inverse third power of distance.

That is also proportional to the diameter of the body being acted upon. So, the tidal force on small bodies (like humans, or even large lakes) is vanishingly small. Since the moon has a quarter of the diameter of the Earth, the tidal force of the Earth on the moon is only 80/4 times the tidal force of the moon on the Earth.

Lord General MB
2002-May-27, 01:43 AM
On page 138 at the bottom, it is written:

"...(compare that to the largest nuclear bomb ever built, which had a yield of about 100 megatons)."

This is techincally incurrect.

The largest bomb ever built had a yield of 50 megatons (the Soviet, "Czar Bomba"). That same bomb, when planned, was set for a yield of 100, yes, but wasn't built to that standard. She topped off as a triple stager, yielding a mighty impressive 50 megatons- so powerful that when exploded, in Siberiria, she broke windows in Finland.

<font size=-1>[ This Message was edited by: Lord General MB on 2002-05-26 21:45 ]</font>

Irishman
2002-Jun-12, 06:35 AM
The Bad Aviator said:

Wings do not tilt, and the force that turns an airplane is its horizontal component of lift, not thrust.

johnwitts said:

Ah, but what causes lift? There must be a thrust somewhere.

John, when speaking of airplanes, the terms "lift" and "thrust" have specific meanings. While lift is a force, it is not thrust. Lift is the force on the wings that keeps the plane in the air. Thrust is the force of the engine (propeller, jet) pushing the plane through the air. This is the technical context that The Bad Aviator is using, and why he is correcting the BA.

Weight and drag are the other two components of the equations.

johnwitts
2002-Jun-13, 12:20 AM
But aren't props just wings going round and round? A bit like helicopter rotors are big propellers turned 90 deg?

Irishman
2002-Jun-13, 09:11 AM
Yes, and no.

Propellers do have an airfoil profile in order to push air. But that does not make them a wing. Wings give lift, propellers give "push", or thrust.

Helicopter rotors are a lot more complex than just a propeller aimed up. They have lots of controls to stabilize the rotors and adjust the blade angles to provide the controlled lift, to steer, etc.

Look, we're talking about technical terminology as precise as "force", "acceleration", or "theory". "Thrust" has a specific meaning - the propulsion of the plane. If you want to talk about other pushes on different parts of the plane, refer to them as forces. It's the terminology of physics.

GrapesOfWrath
2002-Jun-14, 11:17 AM
On 2002-06-13 05:11, Irishman wrote:
Look, we're talking about technical terminology as precise as "force", "acceleration", or "theory".

Theory has a precise definition?

ZaphodBeeblebrox
2002-Jun-14, 11:21 AM
On 2002-06-14 07:17, GrapesOfWrath wrote:


On 2002-06-13 05:11, Irishman wrote:
Look, we're talking about technical terminology as precise as "force", "acceleration", or "theory".

Theory has a precise definition?


Yeah, it's when you're not quite Drunk enough to be making an Hypothesis, but still Pickled Enough, to be in an Altered State, of Consciousness!

mik sawicki
2002-Jul-04, 05:55 AM
On 2002-04-18 13:25, The Bad Aviator wrote:
Lift is caused my a pressure difference between the top and bottom of the wings.


This is a very common misconception. While indeed there's a pressure difference between the top and the bottom of the wing, the result is a very small lift force that's only a small fraction of what's needed to balance the force of gravity pulling the plane down.
Essentially a plane flies because the wing pushes the air down (action), and the reaction force is the air pushing the wing up. See excellent web page "How the airplanes fly" at
http://www.allstar.fiu.edu/aero/airflylvl3.htm

to see what's wrong with popular Bernoulli folklor.

GrapesOfWrath
2002-Jul-18, 11:17 AM
On 2002-07-04 01:55, mik sawicki wrote:
While indeed there's a pressure difference between the top and the bottom of the wing, the result is a very small lift force that's only a small fraction of what's needed to balance the force of gravity pulling the plane down.
Essentially a plane flies because the wing pushes the air down (action), and the reaction force is the air pushing the wing up.

You know, if I didn't know any better, I might call that "pushes the air down" a "pressure". :)

SeanF
2002-Jul-18, 02:06 PM
On 2002-07-18 07:17, GrapesOfWrath wrote:
You know, if I didn't know any better, I might call that "pushes the air down" a "pressure". /phpBB/images/smiles/icon_smile.gif


Yeah, but you call that centrifugal effect a "force", too, so what do you know? /phpBB/images/smiles/icon_wink.gif

Dana_Mix
2002-Aug-17, 09:42 PM
On page 126 the Bad Astronomer wrote, referring to the May 2000 planetary alignment, "Just a few months into the new century we had to deal with yet another instance of the shadow of our primitave need to blame the skies." The new century began with 2001. By the same reasoning that the second term of a president's reign begins with year 5, or the second week in the month begins with day 8.

http://aa.usno.navy.mil/faq/docs/millennium.html
Dana

<font size=-1>[ This Message was edited by: Dana_Mix on 2002-08-17 17:45 ]</font>

The Bad Astronomer
2002-Aug-18, 12:00 AM
Holy mackeral! That's a very good catch, and I am very embarrassed by that one.

The third printing is already at the publishers (they were backordered 1500 copies out of 4000!), so I'll have to get that one in for the fourth. Thanks!

GrapesOfWrath
2002-Aug-18, 05:14 AM
On 2002-08-17 17:42, Dana_Mix wrote:
The new century began with 2001.

Not everybody agrees with that. In fact, I'm going out on a limb and say that most people don't agree with that. The USNO site is strictly opinion, when it comes to the millennium, and is not official.

I'm hoping that this does not turn into an interminable debate on the subject. Perhaps we should start a new thread--and I think it should be only new info not already presented at the USNO site that Dana_Mix linked.


By the same reasoning that the second term of a president's reign begins with year 5, or the second week in the month begins with day 8.

But. The second year does begin with year 5, and the second week with day 8. Did you mean year 6 and day 9?

Phobos
2002-Aug-18, 07:36 AM
Consider the sentences "There are no apple in my basket" and "There is no apple in my basket". To me the first is correct and the second is faulty. The application of the word "no" has the same meaning as the word "none" in the sentence under discussion so I would go with the word "are".

Phobos

Donnie B.
2002-Aug-18, 05:01 PM
On the date-of-the-millennium question, the late Steven Jay Gould related an interesting story.

He discussed the issue with a savant, who could barely tie his shoelaces but was a whiz at dates -- telling you the day of the week for an arbitrary date in the year 8726, and the like.

Gould asked this fellow when the 21st century started. He answered without hesitation, "January 1st, 2000. The first century only had 99 years."

Not definitive, of course, but it's an interesting perspective!

GrapesOfWrath
2002-Aug-18, 06:56 PM
Phobos, I think you're talking about the discussion at the bottom of page one of this thread?



On 2002-08-18 01:14, GrapesOfWrath wrote:
Perhaps we should start a new thread

Donnie B., I responded in the thread Horse that wouldn't die (http://www.badastronomy.com/phpBB/viewtopic.php?topic=2019&forum=9&0).

Silas
2002-Aug-18, 10:52 PM
On 2002-08-18 03:36, Phobos wrote:
Consider the sentences "There are no apple in my basket" and "There is no apple in my basket". To me the first is correct and the second is faulty. The application of the word "no" has the same meaning as the word "none" in the sentence under discussion so I would go with the word "are".

Phobos


By convention, if nothing else, the following sentences are correct in modern English: "There are no apples in my basket" and "There is no apple in my basket."

I think it's called "agreement of number."

It's the same as if you were to say "There are two apples in my basket" or "There is one apple in my basket." The number has to agree. "Are" applies to the plural "apples" and "is" applies to the singular "apple."

Um...

Or am I beating a dead horse?

Anyway, the sentence "There are no apple in my basket" is a violation of the rules of standard formal English as understood at this space-time coordinate.

Silas

GrapesOfWrath
2002-Aug-19, 12:42 AM
On 2002-08-18 18:52, Silas wrote:
Anyway, the sentence "There are no apple in my basket" is a violation of the rules of standard formal English as understood at this space-time coordinate.

Whoa, didn't even catch that the first time. Phobos, are you really saying that "There are no apple in my basket" is correct, and that is not just a misprint (maybe it should be "there are no apples in my basket)?

Dana_Mix
2002-Aug-19, 11:40 PM
On 2002-08-18 01:14, GrapesOfWrath wrote:


On 2002-08-17 17:42, Dana_Mix wrote:
The new century began with 2001.

Not everybody agrees with that. In fact, I'm going out on a limb and say that most people don't agree with that. The USNO site is strictly opinion, when it comes to the millennium, and is not official.

I'm hoping that this does not turn into an interminable debate on the subject. Perhaps we should start a new thread--and I think it should be only new info not already presented at the USNO site that Dana_Mix linked.


By the same reasoning that the second term of a president's reign begins with year 5, or the second week in the month begins with day 8.

But. The second year does begin with year 5, and the second week with day 8. Did you mean year 6 and day 9?


The second week begins with day 8 and a president's second term with year 5, as I said.

Most people think the new century began with AD 2000. But science sites, encyclopedias, and government sites are right. http://dir.yahoo.com/Science/Measurements_and_Units/Time/Actual_Start_of_the_Third_Millennium/

The first century began AD 1. The second began with AD 101, and the 21st with AD 2001.

but I'll be happy to debate it.

best regards,

Dana

GrapesOfWrath
2002-Aug-20, 12:02 PM
On 2002-08-19 19:40, Dana_Mix wrote:
Most people think the new century began with AD 2000. But science sites, encyclopedias, and government sites are right.

It's a matter of opinion, only. There can't be a wrong or a right.

Dana_Mix
2002-Aug-29, 01:42 AM
On p 37 of "Bad Astronomy" it says "There are 51120977 square kilometers of it, give or take a kilometer or two..." Shouldn't that be a "square kilometer or two...

Great book.

best regards,

Dana

GENIUS'02
2002-Aug-31, 07:51 AM
On 2002-08-18 03:36, Phobos wrote:
Consider the sentences "There are no apple in my basket" and "There is no apple in my basket". To me the first is correct and the second is faulty. The application of the word "no" has the same meaning as the word "none" in the sentence under discussion so I would go with the word "are".

Phobos


question, are you talking in plural or singular? if plural then an 's' must be added to apple, and the first one becomes the better of the two sentances.
if it is singular then the first sentance is an awful sentance thus the second sentance is the better one by default.

GENIUS'02
2002-Aug-31, 08:08 AM
i'd like to note that scientists are never renowned for their english ability, and i would have thought that any publishers would have atleast four proof-readers two to simply read how the english goes together, and flows, and the other two to check the scientific side of things.

any writer will admit that the mind works quicker than the hand and they just want to put their ideas onto paper and upon re reading the written work they will miss things that shouldn't be missed but it is natural human nature for us to miss things, thats is why we get outside people to do the proof-reading. and thats just the english.

and so i congratulate BA on his book for having so few errors in his book, of which most appear to be mis-phrased sentances. so congratulations BA and i look forward to reading your book. (persuming i get it for my 17'th b'day next week)

chris

The Bad Astronomer
2002-Aug-31, 06:35 PM
Thanks Chris! I hope you like it, and, of course, happy birthday. /phpBB/images/smiles/icon_wink.gif

I am a scientist, but also a writer, and I try to write well. My grammar can be a bit awkward sometimes, but my wife's grammar is excellent. She always finds my subject/predicate mismatches. Also, there were a number of editors between me and the final book, yet some mistakes in grammar, typos and the like still got through. Oh well. Hopefully the fourth printing of the book will be as close to perfect as possible. I still have some errors to correct.

nayland
2002-Sep-20, 02:22 AM
[quote]

Aircraft get their *unique* thrust from the Venturi effect.

Really?

I thought that it was Bernouli's principle
"Pressure of a fluid is least where velocity is greatest."

Venturi effect is what causes a downdraft of air into a carb. or into the vent pipes on a hot tub/spa... no?

Kaptain K
2002-Sep-20, 09:37 AM
On 2002-09-19 22:22, nayland wrote:
[quote]

Aircraft get their *unique* thrust from the Venturi effect.

Really?

I thought that it was Bernouli's principle
"Pressure of a fluid is least where velocity is greatest."

Venturi effect is what causes a downdraft of air into a carb. or into the vent pipes on a hot tub/spa... no?
The Venturi effect is a practical application of Bernouli's principle.

KarenS
2002-Sep-28, 10:31 PM
A question about "feeling" gravity. In BA, The Gravity of the Situation, p 68, you wrote in one paragraph:

To see this, think about astronauts on board the sapce station. They float freely, as if there is no gravity. In fact, they feel gravity almost as strongly as we do here on the surface of the Earth;

In another paragraph on the same page you wrote:

An astronaut standing on a scale in the space station would measure her weight as zero because she is falling around hte center of the earth. Gravity affects her, but she cannot feel it.

I think this may be too nit-picky, but that almost sounds like you're contradicting yourself with respect to whether someone in orbit feels gravity. What you're trying to get across is pretty clear (the force of gravity is present, but is not perceived), but I'm still not sure if you consider it correct to say that astronauts in orbit don't *feel* gravity. I don't want to be responsible for passing along Bad Astronomy myself.

AstroMike
2002-Sep-28, 11:08 PM
On page 181 near the top, it says:
We now know the surface of Venus has an incredibly high temperature, over 900° Celsius (1,600° Fahrenheit),

That seems too high for me Phil. The surface temperature of Venus, as I'm aware of it, is only as high as 900°F (480° C)

Anyway, enjoying the rest of the book very well. /phpBB/images/smiles/icon_smile.gif

GrapesOfWrath
2002-Sep-29, 12:08 AM
On 2002-09-28 19:08, AstroMike wrote:
That seems too high for me Phil. The surface temperature of Venus, as I'm aware of it, is only as high as 900°F (480° C)

That's certainly what they say at Views of the Solar System (http://www.planetscapes.com/solar/eng/venus.htm) and this NASA page (http://vesuvius.jsc.nasa.gov/er/seh/venus.html), and Nine Planets (http://www.nineplanets.org/venus.html) says 740° K. Nice catch.

David Hall
2002-Sep-29, 01:58 AM
On 2002-09-28 18:31, KarenS wrote:

I think this may be too nit-picky, but that almost sounds like you're contradicting yourself with respect to whether someone in orbit feels gravity. What you're trying to get across is pretty clear (the force of gravity is present, but is not perceived), but I'm still not sure if you consider it correct to say that astronauts in orbit don't *feel* gravity. I don't want to be responsible for passing along Bad Astronomy myself.


Maybe a little bit nitpicky, but it's a good point. The problem is that the BA uses the word "feel" in two different contexts. The astronauts don't feel gravity, as in sense it, but they do feel gravity, as in "have a passive experience of" it.

Yes, it is a bit confusing. I think the second one should be changed to "they experience gravity almost as strongly as we do" just to be a bit clearer.

GrapesOfWrath
2002-Sep-29, 03:07 PM
On 2002-09-28 21:58, David Hall wrote:
Yes, it is a bit confusing. I think the second one should be changed to "they experience gravity almost as strongly as we do" just to be a bit clearer.
Did you mean the first one? The first one in KarenS's post? That's the one that uses "they" instead of "her" (I just checked, and their order in the book is the same as in KarenS's post.)

And I think "feel" should be reserved for the case where the person has a physical sensation associated with the experience, as opposed to a lack of sensation--so it'd make sense to use "feel" in the second one, not the first.

David Hall
2002-Sep-29, 03:46 PM
I meant the second one in my post. Of course I agree with you. I just wanted to confirm what Karen was saying and got it a bit turned around.

KarenS
2002-Sep-30, 02:38 PM
The beauty of English is that it's so flexible, but that's what also gets us into trouble.

I guess I'd like to see something like "the force of graity is acting on..." the folks in orbit. That also takes out any human element--the gravity is acting on inanimate objects that don't have sensations as well.

Travis
2002-Oct-20, 10:07 PM
Considering all of the posts here about grammar, I'm very surprised that nobody has noticed a very fundamental technical error.

On pg 65:"The Earth has a lot more mass than I do... so it pulls on me a lot harder than I do on it."

Not only does this statement violate Newton's third law (action-reaction) which is taught in high schools, but it shows a misunderstanding of (Newtonian) gravity.

Newton's law of universal gravitation:
F=(G*m1*m2)/r^2
Gravitational force is proportional to the product of the masses of TWO objects, so you can't talk about gravitational force without
talking about a pair.

You exert exactly the same force on the earth as it exerts on you.

The Bad Astronomer
2002-Oct-20, 11:11 PM
This has been corrected in later printings. I was trying to simplify the situation, and wound up oversimplifying it. The forces are equal, of course, but the accelerations are different. I was talking about accelerations in that statement, but (over)simplified it to just "pulling". Since it's confusing to people who know better, I changed it in the later printings.

kipfisher
2002-Nov-30, 09:30 PM
On 2002-04-16 12:44, The Bad Astronomer wrote:
Folks:

The list below contains the errors and typos that I know about in the book. A lot of those have already been talked about on this board, and some I found on my own.

If you know of any more, please add them to this thread.


You would do well to consider linguistic history in your discussion of the "DARK SIDE OF THE MOON" ON PP. 31 - 33. Long ago, the word "dark" referred to anything unseen. Astronomers of the time called the unseen side of the moon the "dark side of the moon." They did not imagine that the dark side was never in sunlight.

This usage of the word "dark" survived into the 19th century when people in England spoke of "darkest Africa." They did not imagine that any part of Africa never received sunlight. The reference was to the part of Africa about which Europeans knew almost nothing. It was hidden, unseen, "dark."

The usage lives today in the jargon of live theater. If a play is presented every night of the week except Monday, then the theater is said to be "dark on Monday."

To be sure, the change in the meaning of the word "dark" has led to a pervasive piece of bad astronomy in modern times. However, your discussion of this piece of bad astronomy would benefit greatly from an acknowledgement of its source.

Kip Fisher

ToSeek
2002-Dec-03, 05:43 PM
On 2002-11-30 16:30, kipfisher wrote:

The usage lives today in the jargon of live theater. If a play is presented every night of the week except Monday, then the theater is said to be "dark on Monday."


That's because they don't turn the lights on. /phpBB/images/smiles/icon_wink.gif

GrapesOfWrath
2002-Dec-03, 06:07 PM
I knew you'd say that.

Kaptain K
2002-Dec-03, 06:28 PM
I knew you'd say that.

jokergirl
2002-Dec-15, 06:58 PM
i just got the book from amazon. great job! i love it! (geek girl talking /phpBB/images/smiles/icon_wink.gif )

on page 100, last paragraph: "Which stars looks white?"
should be "look white" (plural).

I also didn't quite get the BA's "Twinkle twinkle" rhyme, but then I'm no native speaker, so maybe it's just me. still, I would be happy if anyone cared to explain?

/phpBB/images/smiles/icon_wink.gif

GrapesOfWrath
2002-Dec-19, 07:56 PM
On 2002-12-15 13:58, jokergirl wrote:
I also didn't quite get the BA's "Twinkle twinkle" rhyme, but then I'm no native speaker, so maybe it's just me. still, I would be happy if anyone cared to explain?
I missed this a while back. The BA sorta explains the situation on that page 89, and the top of page 90. "Seeing", to an astronomer, is a condition of the atmosphere. Even though the sky may be clear of clouds, it can be so turbulent that even the planets twinkle--and such conditions make for poor astronomy viewing.

maryellenandtom
2003-Jan-22, 02:41 PM
A couple of items to consider for future editions.

EGGS
A double hit of Bad Biology right on the first page of Chapter 1 (p. 11)!

First, you say that eggs have a "calcium shell". It isn't calcium, it's calcium carbonate (American Egg Board (http://www.aeb.org)). You get it right on p.15 "has calcium carbonate deposited", but wrong again on p.15 "calcium comes out" and p.16 "calcium bumps".
This was briefly discussed in another thread in this forum. (10 page excerpt at the Wiley website) (http://www.badastronomy.com/phpBB/viewtopic.php?topic=669&forum=9) The BA said:


We say you need calcium for your bones, but really we mean calcium carbonate. So it's not so much sloppy as it is a shortcut, almost an expression. I don't think using it in this context is incorrect.

Bones and eggs contain calcium but aren't made of calcium. And bones are primarily calcium phosphate, not calcium carbonate. The calcium content of calcium carbonate is about 40%. I know most people don't recognize the difference between calcium mineral and calcium metal. I still think you should say it right at the first occurrence, if not every time.
By the way, the American Egg Board website mentions equinox standing in their egg trivia.

Second, genus names should be capitalized, as in Gallus domesticus. (See the Columbia Encyclopedia (http://www.bartleby.com/65/) under "classification"). You have gallus (lowercase) on p.11.

FLOUR
In discussing moon dust in Chapter 17 (p.165), you state "Flour is incredibly dry." This isn't true - flour is about 12% water, almost as much as raisins! USDA National Nutrient Database (http://www.nal.usda.gov/fnic/foodcomp/index.html)). This has significance since you make such a big deal about the absolute dryness of lunar soil.
The activity of water in foods can be surprising. We see food all the time, so we think we understand it, but we're often wrong (not unlike the sky). A better example may be powdered sugar, at 0.3% water. Granulated sugar and salt have less even water, but they are crystalline rather than powdered, so don't exhibit moon-dust-like behavior.



<font size=-1>[ This Message was edited by: maryellenandtom on 2003-01-22 09:43 ]</font>

The Bad Astronomer
2003-Jan-22, 08:39 PM
On 2003-01-22 09:41, maryellenandtom wrote:
A couple of items to consider for future editions.

First, you say that eggs have a "calcium shell". It isn't calcium, it's calcium carbonate

Yes, and I should have been more careful. I'll add this to the list of corrections for the fifth edition, if we ever get to it.



Second, genus names should be capitalized, as in Gallus domesticus.


I looked into that (by looking up some genus names!) and copied what they did. I'll have to look up the proper way to do this, just as a back up.



FLOUR
In discussing moon dust in Chapter 17 (p.165), you state "Flour is incredibly dry." This isn't true - flour is about 12% water, almost as much as raisins!

That's amazing! I'll look into this as well. Thanks for your comments!

GrapesOfWrath
2003-Jan-23, 04:18 AM
On 2003-01-22 09:41, maryellenandtom wrote:
flour is about 12% water, almost as much as raisins! USDA National Nutrient Database (http://www.nal.usda.gov/fnic/foodcomp/index.html)).

Type flour into their search engine (http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl), click on Wheat flour, white, all-purpose, enriched, bleached, then click report.

The Bad Aviator
2003-Feb-04, 11:44 PM
So Mr. Plait, do all of us who offered suggestions get a free autographed copy of the latest edition?

kilopi
2003-Feb-05, 03:28 AM
The BA addressed the autograph situation in this thread (http://www.badastronomy.com/phpBB/viewtopic.php?topic=764&forum=9).

NASA Fan
2003-Sep-19, 02:14 AM
p 16, last paragraph, (3 lines from the bottom)

...it's all about the equinox, they telwl me.

should be ...they tell me.

This was in the 5th. edition, so yes you made it that far--congratulations.

The Bad Astronomer
2003-Sep-19, 02:54 AM
Yegads. That typo is not in the second printing!

They added a typo to my book! :o

The Supreme Canuck
2003-Sep-19, 03:26 AM
I think I smell a conspiracy...

Eroica
2003-Sep-23, 03:45 PM
p 89, line 3: "music by Wolfgang Amadeus Mozart"

Actually the music is from an anonymous French folksong, Ah, vous dirai-je, Maman. Mozart did write a set of piano variations on the tune, though.

Apologies if this has already been dealt with, but with a username like Eroica I just couldn't let this one go uncorrected.

Candy
2004-Oct-17, 05:26 AM
p 16, last paragraph, (3 lines from the bottom)

...it's all about the equinox, they telwl me.

should be ...they tell me.

This was in the 5th. edition, so yes you made it that far--congratulations. Hate to bump a thread, but I just found this! :lol: It's a good thing I did a search of the BABB. I almost started a new thread.

frenat
2004-Oct-24, 01:14 AM
In the index entry for Jupiter Effect, the it list the page as 151 and it should instead be 131.

mickal555
2005-Jan-12, 11:33 PM
On 2002-07-18 07:17, GrapesOfWrath wrote:
You know, if I didn't know any better, I might call that "pushes the air down" a "pressure". &lt;IMG SRC="/phpBB/images/smiles/icon_smile.gif">


Yeah, but you call that centrifugal effect a "force", too, so what do you know? &lt;IMG SRC="/phpBB/images/smiles/icon_wink.gif">


speaking of which

On padge
249
Thats called centifical force, and it would on a spaceship, too.

edition 5? or six is the number part of IBSN(6) or below it(5)
I um hmm....

ZaphodBeeblebrox
2005-Jan-13, 03:16 AM
On 2002-07-18 07:17, GrapesOfWrath wrote:
You know, if I didn't know any better, I might call that "pushes the air down" a "pressure". &lt;IMG SRC="/phpBB/images/smiles/icon_smile.gif">


Yeah, but you call that centrifugal effect a "force", too, so what do you know? &lt;IMG SRC="/phpBB/images/smiles/icon_wink.gif">


speaking of which

On padge
249
Thats called centifical force, and it would on a spaceship, too.

edition 5? or six is the number part of IBSN(6) or below it(5)
I um hmm....

Whoa ...

Have you, Been Studying Hubbish?

mickal555
2005-Jan-13, 03:19 AM
On 2002-07-18 07:17, GrapesOfWrath wrote:
You know, if I didn't know any better, I might call that "pushes the air down" a "pressure". &lt;IMG SRC="/phpBB/images/smiles/icon_smile.gif">


Yeah, but you call that centrifugal effect a "force", too, so what do you know? &lt;IMG SRC="/phpBB/images/smiles/icon_wink.gif">


Speaking of which On padge 249 of Bad astronmy (edition 5 I think? or six, is the number part of IBSN(6)? or the one below it(5)? anyway on to the mistake:
Quote "Thats called centifical force, and it would on a spaceship, too."

force
I um hmm....

Whoa ...

Have you, Been Studying Hubbish?
As a matter of fact Yes I have and I can now mostly understand him.
And no I havn't attemted it and the above post isn't an attempt.
I'll redo it in my above quote

Gezz in my first fair dinkum redo it did look HUb' ish uh oh.....


Speaking of which On padge 249 of Bad astronmy
{edition 5? or six is the number part of IBSN(6) or below it(5)}
Quote "Thats called centifical force, and it would on a spaceship, too."

force
I um hmm....

ZaphodBeeblebrox
2005-Jan-13, 05:26 AM
On 2002-07-18 07:17, GrapesOfWrath wrote:
You know, if I didn't know any better, I might call that "pushes the air down" a "pressure". &lt;IMG SRC="/phpBB/images/smiles/icon_smile.gif">


Yeah, but you call that centrifugal effect a "force", too, so what do you know? &lt;IMG SRC="/phpBB/images/smiles/icon_wink.gif">


Speaking of which On padge 249 of Bad astronmy (edition 5 I think? or six, is the number part of IBSN(6)? or the one below it(5)? anyway on to the mistake:
Quote "Thats called centifical force, and it would on a spaceship, too."

force
I um hmm....

Whoa ...

Have you, Been Studying Hubbish?
As a matter of fact Yes I have and I can now mostly understand him.
And no I havn't attemted it and the above post isn't an attempt.
I'll redo it in my above quote

Gezz in my first fair dinkum redo it did look HUb' ish uh oh.....


Speaking of which On padge 249 of Bad astronmy
{edition 5? or six is the number part of IBSN(6) or below it(5)}
Quote "Thats called centifical force, and it would on a spaceship, too."

force
I um hmm....

Whoa ....

Stream of Conciousness ...

irony
2005-Sep-23, 03:28 AM
This may have been mentioned already, but Cardinal Wolsey is quoted very much out of context. What he said was a bit less emphatic, something like: "be careful what you put in his head, because you will never get it out". And 'his' is 'Henry VIII's. Wolsey was talking about a particular individual, not humanity in general.

Marlayna
2005-Dec-24, 06:42 PM
Hi all. Long time no see :P

I read the book very recently, and I have a few things to point out, which are not typos.

First, the mother of all nitpickers: page 37, it should of course read "...give or take a square kilometre or two..."

I know, I know :P

Second, the second or so paragraph on page 98. Would it really complicate the explanation to use the right term here (plasma)? You keep calling it "gas", implying it's made of atoms. I think you oversimplified this bit for no good reason.

OK, this wasn't technically a mistake.

Third comes a real actual error. Page 177, second paragraph. *long breathy sigh* Where do I begin? You got it all mixed up. Minerva was a Roman goddess, not a Greek one. Her Greek equivalent was Athena, the goddess of knowledge. Athena/Minerva were never associated with the planet Venus. Venus is the Roman equivalent of Aphrodite, the goddess of beauty. Venus was named after her because it's so beautiful. Athena was indeed born out of Zeus's head, fully grown and fully armed, but that has nothing to do with Aphrodite; Aphrodite was created when Zeus's sperm fell in the ocean.

But maybe it was Velikovsky who got it wrong in the first place.

grant hutchison
2006-Jan-02, 01:29 AM
Page 213, end of last full paragraph:

For astrology to sell, buyers must not seek out the fundamental principles behind it, because if they do they see that there is none.

Probably should be:

...there are none.Well...
I'm bored and the phrase still appears in my edition.
I think the problem is that "... is none" is grammatically correct (since the verb to be is applied to the singular none), but it's a sudden change to singular from the previous plural "... fundamental principles ...".
So it's what the Fowler brothers would call an "infelicitous construction".
Replace it with the logically and grammatically equivalent: "For astrology to sell, buyers must not seek out the fundamental principles behind it, because if they do they see that there isn't one" and you get the same lurching sensation at the end, even though the sentence is entirely logical.
Since it evidently makes several folks here feel as uneasy as I do, I'd suggest "... that there aren't any" is the way to go, since any agrees in number with principles, whereas none doesn't.

Grant Hutchison

The Bad Astronomer
2006-Jan-02, 02:10 AM
Marlayna-- stars are plasma, of course, but it's still gas. They're made of atoms, just ionized ones. And not all the atoms are fully ionized!

As far as Minerva goes, that part caused me some grief. When I read Velikovsky's book, I laughed, thinking that Minerva wasn't associated with Venus, Aphrodite was, as you point out. Turns out, the planet Venus was associated with Minerva, I think early in mythological history. That surprised me. I have this in my notes somewhere, but I'm not sure where.

I'm scratching my head over the Greek/Roman thing. I remember clearly correcting that error. Now I don't know why it's there.

SeanF
2006-Jan-04, 08:01 PM
Page 213, end of last full paragraph:

For astrology to sell, buyers must not seek out the fundamental principles behind it, because if they do they see that there is none.

Probably should be:

...there are none.
Well...
I'm bored and the phrase still appears in my edition.
I think the problem is that "... is none" is grammatically correct (since the verb to be is applied to the singular none), but it's a sudden change to singular from the previous plural "... fundamental principles ...".
So it's what the Fowler brothers would call an "infelicitous construction".
Replace it with the logically and grammatically equivalent: "For astrology to sell, buyers must not seek out the fundamental principles behind it, because if they do they see that there isn't one" and you get the same lurching sensation at the end, even though the sentence is entirely logical.
Since it evidently makes several folks here feel as uneasy as I do, I'd suggest "... that there aren't any" is the way to go, since any agrees in number with principles, whereas none doesn't.

Grant Hutchison
"None" is not arbitrarily singular, it can be plural as well. It depends on context.

In this case, it probably should be "are none," because the implied concept is "there are not any principles" as opposed to "there is not one principle" (or even "there is not any principle," for that matter).

Which calls to mind that "any" isn't arbitrarily plural, either - "Are there any water in the well?" isn't right, is it? :D

grant hutchison
2006-Jan-04, 08:42 PM
"None" is not arbitrarily singular ...I didn't say that it was; just that "is none" is grammatically correct usage. The singular also has the force of etymology behind it, since it comes to us from Old English meaning "not one". With this in mind, many folk are still a little leery of giving "none" an outing in plural form, and I suspect the BA has this in mind when he sticks to the singular - it gives enough of a jolt on reading to suggest that it's deliberate policy rather than accident, but of course I may be wrong.


In this case, it probably should be "are none," because the implied concept is "there are not any principles" as opposed to "there is not one principle" (or even "there is not any principle," for that matter).Fair enough, if you're comfortable with "are none". Some people don't like to use it (I'm one of those), and some still see it as an illiterate usage (I'm not one of those). And when you're writing for a wide audience you do tend to fret a bit about such things, since you'd rather the reader concentrated on your content rather than your grammar. So my suggestion is to just bail out of the infelicitous mix of singular and plural, and recast the sentence so that no-one can take exception to it.


Which calls to mind that "any" isn't arbitrarily plural, either - "Are there any water in the well?" isn't right, is it? :DI didn't say that, either. Just that "aren't any" is an unexceptionable construction that gets you out of a stylistic bind.

My point is only this: if the grammar is open to interpretation and argument, you're probably better just rewriting the sentence. Sorry if anyone thought I was being grammatically proscriptive.

Grant Hutchison

TheBlackCat
2006-Feb-22, 10:16 PM
Alright, I do not know if this has been dealt with in later editions (I have a first edition). I found a pretty significant error, though.

On page 101, near the end of chapter 10, the book is talking about the reason stars appear white. The book says this is because it is too dark for the color-sensetive cones to operate and the rods that are still operating cannot differentiate color. Although it is true that rods can only see black and white and it is true that they are active well below the light intensity where the frequency-sensetive cones no longer operate, it is not and cannot be the reason stars appear white. It is a very commonly-told myth that is believed by many people, but it is still wrong.

Want proof? Look right at a star. Do you see it? Then you are not using your rods. You can roughly break the retina into three sections: the fovea, the optic disk, and everything else. The optic disk is where the neurons and blood vessels from the retina leave the eye, this has no receptors and thus you are blind there. The majority of your retina is like what most people think of when they think of the retina: a mix of rods and cones (far more rods than cones, incidentally). The fovea is the center part of the eye, it is in the center of your visual field and what you are using when you look right at something.

The fovea is important because it is the region where your visual acuity is the greatest. Try a simple experiment. Grab a book, any book. Now, hold it so the distance between the book and your face is a foot or less (you don't need to be that exact). Focus your vision on a word at the very center of a page of text. Now, without moving your eyes, try reading text on either side, above and below where your eye is focused. How far you can you read? Not very far. The actual area where your visual acuity is good enough to identify any sort of detail, the fovea is very small, with a diameter of about 10 degrees of your entire visual area. The fovealo, with the highest acuity (the sort you probably need to read at that distance), is much smaller yet.

So what does this have to do with seeing stars as white? Well, there are a number of problems with rods when you compare them to cones. Cones have superior properties in every way compared to rods. They are better as seeing fast changes, they are better at seeing small details, they can handle much higher light intensities before they shut down (in fact, unlike rods, you will go blind before your cones shut down). The only advantage rods have is that they are sensitive to light intensities far below the minimum threshold for cones. For this reason, rods in the fovea would greatly reduce your visual acuity right where you need it most. That gets us to the problem: the fovea has no rods whatsoever. It only has cones. Rods are only found in the area outside the fovea. If you look right at something, you are using your fovea and thus cannot be using rods. In extreme dark your fovea is literally blind, if you want to see something in that sort of condition you are much better off focusing your eyes a little bit to the side, above, or below what you want to see. So when you are looking at a star, you are using your cones not your rods.

Here is an image showing this:
http://www.phys.ufl.edu/~avery/course/3400/vision/rod_cone_distribution2.jpg
(all images are hosted by the University of Flordia, a large state university, although these exact same pictures appear in my Quantitative Physiology notes on vision. This conforms to the rules on hotlinking images)

Most people don't realize this, but the minimum threshold for cones is actually very low. Starlight, although approaching the threshold for cones, is still well within the level cones can detect (from the figure I am looking at starlight appears to be almost an order of magnitude, 10x, above the cone threshold). Moonlight is several orders of magnitude above the threshold for cones, and is actually closer to the point where rods start getting overwhelmed by too much light and shut down.

The real reason is more complicated, but I will explain it as I understand it (you will want to confirm this). The issue with cones is that cones do not detect color. Cones actually have a broad range of color sensitivity. There are three cones, each one possessing a single type of pigment molecule with a different frequency sensitivity. They each are sensitive to a wavelength range of several hundred nanometers (the entire human visual range is around 300-400 nanometers, depending on what book you are using). However, over their range their response to a particular frequency changes. You can see that below:

http://www.phys.ufl.edu/~avery/course/3400/vision/rod_cone_sensitivity.gif

The black curve is rods, and the other three are the three types of cones. As you can see, they have a peak sensitivity at some frequency and their sensitivity drops off on either side (the image show absorbance, but for a large number of photons this is proportional to the output of each receptor at a given frequency). Note that when you look at a given sensitivity, it crosses each receptor's curve twice. All the nervous system knows is each receptor's output. However, the same output of a given receptor can be triggered by two different frequencies. By looking at the output from a single receptor type it is impossible to tell which frequency is present. However, notice how the sensitivities overlap? This is the key. Although a pair of frequencies stimulating the L receptor (the red one with a peak at longer wavelengths) might trigger the same output in that receptor, those same two frequencies triggering the M receptor (the green one with a medium peak sensitivity) will trigger two completely different outputs. So by comparing the response from different types of receptors with overlapping frequency sensitivities allows two colors that would be indistinguishable to one receptor to be differentiated. This is why people with color blindness have problems, they are missing one or more receptors so much of this overlap is lost and their ability to tell apart certain frequencies is thus also lost.

This brings us to stars. The reason this sensitivity system works is due to the absorbance and stochastic (i.e. random) nature of the pigments that actually detect the light. Given a photon impact, a pigment molecule may or may not actually get triggered. The chance of it getting triggered is proportional to its absorbance at that frequency. The more the absorbance, the more likely the pigment is to respond to a given photon. An individual pigment molecule's response is all-or-nothing. Either it gets triggered or it doesn't. At high light levels with a very large number of photons the random nature of the pigment molecules gets averaged over a huge number of photons and a huge number of pigment molecules, so the absorbance (which is basically a probability in this case) is, within measurable limits, proportional to the sensitivity of the pigment molecule at that frequency (this is called “the law of very large numbers”, and comes into play when doing many trials of an experiment to determine the actual probability of an event occurring). The problem is when there are very few photons. There are simply not enough photons triggering a given receptor to get a good measure of the spectral content of the light. The random nature of the pigment changes overwhelms the normal frequency sensitivity, the exact same group of photons hitting the exact same receptor could trigger very different responses due to the randomness of the pigment responses. What is more, starlight inherently contains a broad range of frequencies. A given receptor will not get very many photons, and which of the available frequencies a given photon has is entirely random. This means that at different points of time the exact same receptor looking at the exact same star will get a significantly different distribution of photon frequencies. This all comes together so that there is not enough information in the receptor activity for the cortex to be able to determine what color the starlight is. Due to various properties of the retina and central nervous system this input gets perceived as white.

01101001
2006-Feb-23, 04:48 AM
The book says this is because it is too dark for the color-sensetive cones to operate and the rods that are still operating cannot differentiate color.
Do you not use averted vision to view dim stars?

Wikipedia: Eye (http://en.wikipedia.org/wiki/Eye)


Its requirement for high intensity light does cause problems for astronomers, as they cannot see dim stars, or other objects, using central vision because the light from these is not enough to stimulate cone cells. Because cone cells are all that exist directly in the fovea, astronomers have to look at stars through the "corner of their eyes" (averted vision) where rods also exist, and where the light is sufficient to stimulate cells, allowing the individual to observe distant stars.

What does the passage in question say, anyway? (I don't own a copy. I'm a bad person.) Does it say color cannot be seen for any stars or for most stars? I think I can tell the difference in bright stars, say Sirius's blue versus Betelgeuse's red, so I'd be surprised if the passage addressed all stars.

grant hutchison
2006-Feb-24, 11:49 PM
Want proof? Look right at a star. Do you see it? Then you are not using your rods.But once your eye has dark-adapted, you no longer fix using your fovea. The point of fixation is shifted 2&#186; from the edge of the fovea after ten minutes adaptation, but drifts back to 1&#186; from the edge of the fovea after an hour of adaptation (reference Y. le Grand's classic Light, Colour and Vision). So you do have rods available at the point of fixation when you are star-gazing. Your highest rod density is at about 20&#186; from the fovea, however (as your diagram shows), so consciously averting your gaze by this amount does improve your sensitivity for very dim stars.

Starlight, although approaching the threshold for cones, is still well within the level cones can detect (from the figure I am looking at starlight appears to be almost an order of magnitude, 10x, above the cone threshold).Can you clarify, here? Visible stars have an approximately 1000-fold variation in brightness.* Phil Plait writes specifically about dim stars: "So, while a dim star may be bright enough for your rods to detect, allowing you to see the star, it may not be bright enough to trip your cones, and so you see no color."
So is the reference you're consulting talking about the retina's ability to detect a point source of some specified magnitude (with a luminance figure in cd/m&#178;), or the very different matter of the retina's ability to see by starlight (with a figure for illuminance, given in lux)? If it is the luminance figure, can you let us know that it applies to the visual threshold for stars, about (or dimmer than) mag 6?
(Illuminance from a starlit sky is a more commonly available figure that does touch the bottom of the cone threshold, but isn't relevant to seeing individual stars.)

Grant Hutchison

Edit:
*Not counting the sun!

kiless
2006-Sep-21, 06:00 AM
Dear BA,

My apologies to fellow forum members if this implies a familiarity or expectation that the BA himself will answer - if needed I'll do an email instead rather than cluttering up the board.

The question is from a student in regards to possible contradictions in the book (in particular, page 162) and the BA website under the Apollo Moonlanding Hoax, url is: http://www.badastronomy.com/bad/tv/foxapollo.html). Admittedly the site is dated from 2001 and the book is dated 2002.

In the book, he states that 'to minimise the risk they put the Apollo spacecraft along a trajectory that only nicked the very inside of the inner belt, exposing the astronauts to as little dangerous radiation as possible. They spent more time in the outer belts, but there the radiation isn't as high. the metal walls of the spacecraft protected the astronauts from the worst of it. Also, contrary to popular belief, you don't need lead shielding to protect yourself from the radiation. There are different kinds of radiation; alpha particles, for example, are just fast-moving helium nuclei that can be stopped by normal window glass.'

On the website it says:

Good: Kaysing's exact words in the program are ``Any human being traveling through the van Allen belt would have been rendered either extremely ill or actually killed by the radiation within a short time thereof.''

This is complete and utter nonsense. The van Allen belts are regions above the Earth's surface where the Earth's magnetic field has trapped particles of the solar wind. An unprotected man would indeed get a lethal dose of radiation, if he stayed there long enough (our emphasis)

Question is: Therefore, did they stay in the outer belts longer than the inner belts or did they pass through it very quickly?

Thank you very much for any help - my student Bec is using this for a skepticism report for the WA Skeptics Awards where she is surveying belief in the Apollo Moon Hoax and seeing if what Michael Shermer says about belief in 'weird things' is true across age and education levels.

Again, if this is an inappropriate question for this particular section, we can email. Thanks.

The Bad Astronomer
2006-Sep-21, 08:59 PM
Kiless-- they were in the belts for just a few minutes. Inner, outer, it doesn't matter. Since they weren't in them for long, they didn't get a lethal dose of radiation. Elevated levels, yes,; lethal, no.

If you sat in the belts long enough, you'd die from radiation, but that would take hours or days, so it wasn't a concern for Apollo.

As I like to tell people: of course the van Allen belts are deadly-- there's no air in them!

kiless
2006-Sep-22, 06:04 AM
Kiless-- they were in the belts for just a few minutes. Inner, outer, it doesn't matter. Since they weren't in them for long, they didn't get a lethal dose of radiation. Elevated levels, yes,; lethal, no.

If you sat in the belts long enough, you'd die from radiation, but that would take hours or days, so it wasn't a concern for Apollo.

As I like to tell people: of course the van Allen belts are deadly-- there's no air in them!

Thank you very much - she will cite this in the assignment she's doing and we hope to send you a copy. Her task is called 'Apollo 11 Moon Landing Hoax' and is for the WA Skeptics Awards.

*P.S - she's standing next to me as I write this and we're both very appreciative!*

darius
2007-Apr-30, 10:12 PM
At least, I think it's the 7th. Got it from Amazon a couple of months ago, and on the copyright page the numbers show "10 9 8 7". To my understanding that's 7th printing. I question it because BA mentioned on the blog recently that it just went into the 6th printing (he mentioned this after I bought it, here (http://www.badastronomy.com/bablog/2007/04/08/big-announcement-part-1-my-next-book)).

Regardless, I found some typos while reading the book. I only see two of them previously mentioned (and both are still there).

pg 16, three lines from bottom - "telwl" should be "tell"

pg 80, 2nd paragraph from bottom, first line - "causes" should be "cause"

pg 173, sentence before break - should be "it was a triumph" instead of "it was triumph"

pg 259, last line of paragraph about Carl Sagan: "can be easily be applied" - should be either "can easily be applied" or "can be easily applied"

pg 213, end of last full paragraph: "is none" should be "are none". I see that's been mentioned several times, and there is disagreement, but there is a rule here: pronouns must agree with the quantity of the noun they replace. "None" is a pronoun that can be singular or plural (in contrast to common belief that it can only be singular; this belief is ahistorical) but in this case is plural (as "none" is referring to "fundamental principles").

Great book in spite of a few typos (and trust me, I find a lot more in most books; I also don't usually bother to notify anyone). I look forward to reading the next BA book!

aroman
2007-Dec-19, 06:50 PM
Great book. I recently read it and thought it was excellent, and I've recommended it to others. I did, however, notice one thing that I feel compelled to correct.

In the Hubble Shoots the Moon section of the Hubble Space Telescope Misconceptions chapter, it is stated that the Moon moves too rapidly for Hubble to track. It is also stated that the Moon observations that Hubble did in 1999 were accomplished by "ambushing" the Moon i.e. using a fixed telescope pointing at just the right time to snap a short exposure as the Moon was passing through the field of view. Both of these statements are incorrect.

The Moon does not move too quickly for Hubble to track, and it was tracking during the 1999 observations. (I was heavily involved in implementing those and other Hubble observations of the Moon.) While it is true that Hubble's ability to track the Moon is limited, the issue is not that the Moon moves too quickly. The issue is that Hubble can track a moving target only in a straight line and only at a constant rate. On the short time scale of an individual Hubble observation, a constant rate linear track works well for almost all bodies in the solar system. However, the apparent motion of the Moon as seen from Hubble varies significantly in both rate and direction - even on a very short time scale. When Hubble tracks the Moon, it is trying to match a constant rate to the Moon's varying rate while at the same time trying to match a straight line to the Moon's curved path.

The result is that some smearing of the observation is inevitable. However, by tracking the Moon as best as Hubble can, the smear will, in most cases, be less than what would result from even a very short exposure using the "ambush" observing strategy.

For more details about Hubble's capabilities for observing the Moon, take a look at this User Information Report (http://www.stsci.edu/hst/HST_overview/documents/uir/UIR-2007-01) which was written to inform astronomers who may be considering lunar observations using Hubble.

Tony Roman
Space Telescope Science Institute

The Bad Astronomer
2007-Dec-20, 04:17 AM
Tony, thanks for that update! I actually talked to someone about this when I wrote the book (and I cannot remember who now; it's been several years) and used what they said. I'm glad to get the scoop from you.

I worked on some of those observations; specifically the STIS spectra of the Lunar Prospector impact. Unfortunately, they didn't work out. I was so into getting that data, and was bitterly disappointed when I saw them. Sigh.