"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?

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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.

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.

I 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

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:

(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:



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.

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Do you not use averted vision to view dim stars?

Wikipedia: Eye

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.

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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 ...

But once your eye has dark-adapted, you no longer fix using your fovea. The point of fixation is shifted 2º from the edge of the fovea after ten minutes adaptation, but drifts back to 1º 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 20º from the fovea, however (as your diagram shows), so consciously averting your gaze by this amount does improve your sensitivity for very dim stars.
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/m²), 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!

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.

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!

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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!*

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).

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!

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 which was written to inform astronomers who may be considering lunar observations using Hubble.

Tony Roman
Space Telescope Science Institute

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.

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