mik sawicki
2003-Feb-06, 10:19 PM
This is an excellent and very much needed book, and I sure hope it will sell well.
I spotted some minor problems that I think might need Phil's attention.
Here's the list of 32 items that I think need revisions.
Regards
Mik Sawicki
1. Page 23, 11-th line from the bottom:
"But if they are fired north,…"
Add "on the northern hemisphere"
2. Page 23, third line from the bottom:
"Lets say you are driving a car north at 100 kph (60 mph) in Wiscasset, Maine. The Coriolis effect deflects you…"
A car is not a good example, as the minute Coriolis acceleration there (0.0014 m/s^2) translates for a 1000 kg car into a Coriolis force of 1.4 N (about 0.3 lb). This force can't deflect the car to the right, since it is too small to overcome the sideways force of static friction between tires and the road, that prevents the tires from skidding sideways. This frictional force will easily peak to the value of some 5,000 N -10,000 N before onset of skidding (on a dry roadway).
So I'd suggest something like: "Imagine you rolled a bowling ball on a perfect wooden floor at 100 kph north…" Or "Let's say a hockey puck is sliding north on a perfect frozen lake… "
A bowling ball can roll sideways under the Coriolis force, and it will. The puck is already sliding, so it will deflect under the Coriolis force as well.
3. Page 23, bottom line, continuation of the same sentence:
"…by the teeny amount of 3 millimeters"
According to my calculations, it's about 0.7 mm, even more teeny.
4. Page 24, second line, continuation:
"10 meters (33 feet)"
I got 9 km (kilometers), i.e. about 1000 times more, a reasonable result, considering that in 1 hour you'd move 100 km north, and if you imagine an air molecule moving as a 100 km/h wind near a low pressure system, then this air molecule gets deflected much more than 10 meters over a distance of 100 km - as weather maps on The Weather Channel prove, when you check a curvature of a wind in a vicinity of a low system.
5. Page 29, 11 line from the top:
"No wonder no one could measure it until recently".
It all depends on what one means by "recently".
Back in 1676, Ole Römer, determined it to be about 125,000 miles per second, about
three-quarters of the correct value of 186,300 miles per second, not to good a result.
Then in 1728, astronomer James Bradley found the speed of light to be 185,000 miles per second, with an accuracy of about one percent.
Around 1850 in France, two rivals, Fizeau and Foucault, determined the speed of light with an accuracy of about +/-1,000 miles per second.
Then Albert Michelson in 1877, using Fizeau and Foucault method got 186,355 miles per second, +/- 30 miles per second.
Then in 1931, using new apparatus, he got the speed of light as 299,774 km/s with an average deviation of 11 km/s from the mean.
6. Page 35, line 3 from the top:
"0.00000000001 centimeters"
To many zeroes following the decimal point! (remove two, or say meters instead of centimeters.)
7. Page 37, first line:
"The Earth is a big place. There are 511,209,977 square kilometers of it, give or take a kilometer or two…"
I think this is both an unreasonable accuracy (9 significant figures?) and precision (+/- 1 km).Besides, it's not clear to me what is it meant here - a surface of a land plus the surface of all oceans, or a total surface that would be revealed after draining all oceans? Also, in case of land, is it an actual surface, or a surface as projected onto a two-dimensional map? I doubt that anybody ever calculated the precise area of all the slopes of all these deep and complicated valleys in Himalayas etc. to get a result within +/- 1 sq. km precision as the quoted number implicitly suggests.
Then, if this is a result of some mathematical calculation, was the p number taken to be 3.141592654, as required by the implied precision, or perhaps rounded of to 3.14 ?
For example, if one keeps the 10 digit precision on the p number and use the formula for the surface area of a perfect sphere, the area quoted above corresponds to the radius of the sphere R = 6378.15000 km, i.e. the radius has to be known with a precision of +/- 1 cm. This does not make much sense, as tidal/atmospheric etc. effects change the radius much more than that, and Earth is not nearly a perfect sphere anyway. If an average radius of 6378.15 km was used, then the surface of a perfect sphere would be 511,210 thousands sq. km
In any case, Earth is not a perfect sphere and the best estimate I'm aware of is 510,101 thousands of square kilometers (six significant figures).
8. Page 42.
The problem is with the picture. Since the blue light has a wavelength of some 400 nm, and red about 700 nm, the scattering of blue light is about (700/40)^4 = 9.4 times more effective than that of red light. Moreover, red photons do not scatter much to begin with, and average number of scatterings per red photon is much less than 1. So the average number of scatterings per blue photon is much less than 9.4, and in reality is actually quite close to 1 (single scattering). Yet the picture shows a blue photon that scattered 33 times! The picture needs to be redrawn to show blue photon scattering only once.
9. Page 44.
The problem is with the picture. Perhaps a footnote is needed, explaining that the thickness of the atmosphere is vastly exaggerated in comparison to the Earth's size. (Earth appears to have a radius of 1.25 inch, so the atmosphere (troposphere) should be about 0.003 inch thin!
10. Page 45, line 2 from the top:
"The air bends the light up,…"
The air bends the light down, but our mind does not know it and assumes that the arriving light did not get bent, and hence arrived from a direction at which it entered the eye, i.e. pointing above the horizon.
11. Page 49, line 4 from the top:
Copernicus published his idea in 1543.
12. Page 49, line 7 from bottom:
"…change in distance over the course of the seasons amounts to only a 4-degree Celsius … change in temperature."
Check this number. There are conflicting opinions. Some claim that a Summer in Australia is hotter than Summer in northern hemisphere, but some people claim the opposite.
"Averaged over the globe, sunlight falling on Earth in January [at perihelion] is about 7% more intense than it is in July [at aphelion]," says Roy Spencer of the Global Hydrology and Climate Center in Huntsville, AL." The fact that the northern hemisphere of Earth has more land, while the southern hemisphere has more water, tends to moderate the impact of differences in sunlight between perihelion and aphelion.
Sunlight raises the temperature of continents more than it does oceans. (In other words, land has a lower heat capacity than water.) In July (aphelion) the land-crowded northern half of our planet is tilted toward the Sun. Aphelion sunlight is a little weaker than sunlight at other times of the year, but it nevertheless does a good job warming the continents. In fact, say climate scientists, northern Summer in July when the Sun is more distant than usual is a bit warmer than its southern counterpart in January."
See: http://science.nasa.gov/headlines/y2001/ast04jan_1.htm?list117398
Actually, you make a similar comment on the top of the Page 54, so there's inconsistency between what's on the Page 54 and the 4 degrees C on page 49.
13. Page 52, Figure Caption.
I'd say: "Summer in northern hemisphere and winter in southern hemisphere. In the northern hemisphere, the Sun is higher in the sky. Its light is more concentrated on the Earth's surface there. At the same time, Sun is lower in the southern hemisphere, and the light gets spread out there, heating the Earth less efficiently."
14. Page 66, line 12 from the bottom:
"6 percent"
I've got 7%
15. Page 70, line 12 from top:
"The time of high and low tides changes every day by about a half hour"
Your explanation and calculation are correct, but the wording of the conclusion is a bit confusing. I'd say the morning tide tomorrow will be about 50 minutes later than the morning tide today, etc.
16. Page 73, line 5 from the top in the first paragraph;
"Tides on the Moon are 80 times…"
About 20 times, since diameter of the Moon is about 4 times smaller than Earth's diameter.
17. Page 79, line 20 from the top.
"The air bends the light up,"
See # 10 above.
18. Page 130, line 20 from the top:
"Moon has 20,000 times the tidal force of all the other planets"
It is perhaps worthwhile to add that the tidal force of all the other planets is mostly due to Venus alone, as the tidal force due to Venus is almost 9 times bigger than that generated by Jupiter. Many people think that it's Jupiter that contributes most to the tidal force of all the other planets!
19. Page 167, line 10 from the top:'
"He grabbed a rock weighing roughly a kilogram (two pounds)"
A kilogram is a unit of mass, not weight. A mass of one kilogram weighs about two pounds on Earth's surface, but only one-third of one pound on Moon's surface. Since the sentence refers to what happened on the Moon surface, this needs to be rewritten.
20. Page 178, line 1 through line 11.
"flung outwards by Jupiter's rapid rotation in the same way that a dog shakes its body to spray off water after a bath.
(…)
Jupiter would slow his own rotation every time this happened,"
Not necessarily. If Jupiter had shed some mass from the surface radially outward, it's rotational speed would have not changed. It's just a conservation of angular momentum. Imagine a merry-go-round with a dude riding on a rim. If the dude jumps off pushing away from the platform, the rotational speed of the platform is not affected. (You seem to hint at this on page 198).
On the other hand, if Jupiter ejected a mass radially out from the inside, than the conservation of the angular momentum dictates that its rotational speed would indeed have decreased. But then the dog analogy does not really apply here.
21. Page 181, the last paragraph:
"Worse, the tides from Venus on the Earth would be huge, kilometers high"
Better! Since Venus would be inside the Roche radius of Earth, the tidal force produced by Earth would be stronger than Venus own gravity and the Venus would disintegrate. And Earth would be inside Venus' Roche limit as well, so Earth would disintegrate too, and Velikovsky wouldn't be around to push his bunk.
22. Page 193, first line:
"Something caused this cloud to collapse"
Why not gravity? The Universe probably started as a lumpy, non-uniform mass distribution, so lumpier areas contracted faster than other.
23. Page 193, line 6 from the top:
"flattened due to centrifugal force and friction"
I'd prefer not to use a concept of centrifugal force, as it requires a prior explanation what a noninertial frame of reference is etc. I'd say due to" inertia and friction", or perhaps "due to angular momentum conservation and friction".
24. Page 214, 3-rd paragraph:
"Mars' gravitational influence on the Earth drops by a factor of more than 50 from one side of the sun to the other"
I've got a factor of about 23.
25. Page 214, 4-th paragraph:
"…the Moon has a gravitational effect on the Earth and you that is more than 50 times the combined gravity of planets".
This is correct, but you could push a limit a bit more: According to my calculations Moon's gravity is about 65 times stronger than combined gravity of all other planets even when they are all at the same time at their closest distances from the Earth, and how often does that happen!
26. Page 247, line 13:
"If some atom is sitting around minding its own business and another one comes along moving faster than sound, the first atom is surprised by it. It's literally shocked: it didn't know what was coming. When this happens to a lot of material it's called a shock wave."
I have a problem with that, since for example a speed of sound in air at room temperature (20 degrees C) is about 343 m/s, yet individual molecules comprising air move much faster. O2 molecule has a speed of 480 m/s, N2 molecule 513 m/s and H2O molecule 640 m/s, yet they do not produce a shock wave, obviously.
27. Page 249, line 11:
"This is called the centripetal force,"
This is called inertia. The car accelerates to the left, but the tendency of a passenger is to continue in a straight line. The centripetal force is a force pulling the car towards the center, which on a flat road is provided by a static friction between the roadway and tires. Likewise, for a rock whirled on a string, the centripetal force is provided by the string that pulls towards the center, etc.
"So, if a pilot flying the spaceship banks during the turn, the centripetal force is directed back, pushing the pilot harder against the seat."
Again, the centripetal force is towards the center of the turn. If the spaceship is not banked, the centripetal force on a pilot is provided by a harness (there's no friction, unless his pants are made from Velcro). If he banks the ship, the seat is pushing him at right angle to the seat, and a component of that push towards the center of the turn acts together with his harness and a friction force now present to provide the centripetal force.
28. Page 251, line 12 from top:
"…the nearest planet (is) about 25 million miles away"
The nearest planet periodically comes as close as 25 million miles.
29. Page 251, line 13 from top:
"…the nearest star to the Sun, Alpha Centauri"
The nearest star is Proxima Centauri at 4.22 light years, c.f. page 29, line23. Alpha and Beta Centauri are at 4.35 light years.
30. Page 252, line 3 from the top:
"…Oort cloud, the cometary halo that is almost a light year across."
Do you mean here the inner diameter of the Oort cloud, outer diameter, or its thickness?
Inner diameter is some 0.7 light year, outer diameter is about 3 light years, and thickness, indeed, about 1 light year.
31. Page 252, line 5 from the top:
"…a trillion kilometers from the heat and fierce gravity of the Sun"
An uninitiated reader might erroneously conclude that Sun's gravity does reach there!
32. Page 253, line 13 from the top:
"…even distant Pluto is 8,000 times closer"
Due to large eccentricity of Pluto's orbit, Pluto is between 5330 and 9330 (on average 6780) times closer to Earth than Proxima Centauri.
I spotted some minor problems that I think might need Phil's attention.
Here's the list of 32 items that I think need revisions.
Regards
Mik Sawicki
1. Page 23, 11-th line from the bottom:
"But if they are fired north,…"
Add "on the northern hemisphere"
2. Page 23, third line from the bottom:
"Lets say you are driving a car north at 100 kph (60 mph) in Wiscasset, Maine. The Coriolis effect deflects you…"
A car is not a good example, as the minute Coriolis acceleration there (0.0014 m/s^2) translates for a 1000 kg car into a Coriolis force of 1.4 N (about 0.3 lb). This force can't deflect the car to the right, since it is too small to overcome the sideways force of static friction between tires and the road, that prevents the tires from skidding sideways. This frictional force will easily peak to the value of some 5,000 N -10,000 N before onset of skidding (on a dry roadway).
So I'd suggest something like: "Imagine you rolled a bowling ball on a perfect wooden floor at 100 kph north…" Or "Let's say a hockey puck is sliding north on a perfect frozen lake… "
A bowling ball can roll sideways under the Coriolis force, and it will. The puck is already sliding, so it will deflect under the Coriolis force as well.
3. Page 23, bottom line, continuation of the same sentence:
"…by the teeny amount of 3 millimeters"
According to my calculations, it's about 0.7 mm, even more teeny.
4. Page 24, second line, continuation:
"10 meters (33 feet)"
I got 9 km (kilometers), i.e. about 1000 times more, a reasonable result, considering that in 1 hour you'd move 100 km north, and if you imagine an air molecule moving as a 100 km/h wind near a low pressure system, then this air molecule gets deflected much more than 10 meters over a distance of 100 km - as weather maps on The Weather Channel prove, when you check a curvature of a wind in a vicinity of a low system.
5. Page 29, 11 line from the top:
"No wonder no one could measure it until recently".
It all depends on what one means by "recently".
Back in 1676, Ole Römer, determined it to be about 125,000 miles per second, about
three-quarters of the correct value of 186,300 miles per second, not to good a result.
Then in 1728, astronomer James Bradley found the speed of light to be 185,000 miles per second, with an accuracy of about one percent.
Around 1850 in France, two rivals, Fizeau and Foucault, determined the speed of light with an accuracy of about +/-1,000 miles per second.
Then Albert Michelson in 1877, using Fizeau and Foucault method got 186,355 miles per second, +/- 30 miles per second.
Then in 1931, using new apparatus, he got the speed of light as 299,774 km/s with an average deviation of 11 km/s from the mean.
6. Page 35, line 3 from the top:
"0.00000000001 centimeters"
To many zeroes following the decimal point! (remove two, or say meters instead of centimeters.)
7. Page 37, first line:
"The Earth is a big place. There are 511,209,977 square kilometers of it, give or take a kilometer or two…"
I think this is both an unreasonable accuracy (9 significant figures?) and precision (+/- 1 km).Besides, it's not clear to me what is it meant here - a surface of a land plus the surface of all oceans, or a total surface that would be revealed after draining all oceans? Also, in case of land, is it an actual surface, or a surface as projected onto a two-dimensional map? I doubt that anybody ever calculated the precise area of all the slopes of all these deep and complicated valleys in Himalayas etc. to get a result within +/- 1 sq. km precision as the quoted number implicitly suggests.
Then, if this is a result of some mathematical calculation, was the p number taken to be 3.141592654, as required by the implied precision, or perhaps rounded of to 3.14 ?
For example, if one keeps the 10 digit precision on the p number and use the formula for the surface area of a perfect sphere, the area quoted above corresponds to the radius of the sphere R = 6378.15000 km, i.e. the radius has to be known with a precision of +/- 1 cm. This does not make much sense, as tidal/atmospheric etc. effects change the radius much more than that, and Earth is not nearly a perfect sphere anyway. If an average radius of 6378.15 km was used, then the surface of a perfect sphere would be 511,210 thousands sq. km
In any case, Earth is not a perfect sphere and the best estimate I'm aware of is 510,101 thousands of square kilometers (six significant figures).
8. Page 42.
The problem is with the picture. Since the blue light has a wavelength of some 400 nm, and red about 700 nm, the scattering of blue light is about (700/40)^4 = 9.4 times more effective than that of red light. Moreover, red photons do not scatter much to begin with, and average number of scatterings per red photon is much less than 1. So the average number of scatterings per blue photon is much less than 9.4, and in reality is actually quite close to 1 (single scattering). Yet the picture shows a blue photon that scattered 33 times! The picture needs to be redrawn to show blue photon scattering only once.
9. Page 44.
The problem is with the picture. Perhaps a footnote is needed, explaining that the thickness of the atmosphere is vastly exaggerated in comparison to the Earth's size. (Earth appears to have a radius of 1.25 inch, so the atmosphere (troposphere) should be about 0.003 inch thin!
10. Page 45, line 2 from the top:
"The air bends the light up,…"
The air bends the light down, but our mind does not know it and assumes that the arriving light did not get bent, and hence arrived from a direction at which it entered the eye, i.e. pointing above the horizon.
11. Page 49, line 4 from the top:
Copernicus published his idea in 1543.
12. Page 49, line 7 from bottom:
"…change in distance over the course of the seasons amounts to only a 4-degree Celsius … change in temperature."
Check this number. There are conflicting opinions. Some claim that a Summer in Australia is hotter than Summer in northern hemisphere, but some people claim the opposite.
"Averaged over the globe, sunlight falling on Earth in January [at perihelion] is about 7% more intense than it is in July [at aphelion]," says Roy Spencer of the Global Hydrology and Climate Center in Huntsville, AL." The fact that the northern hemisphere of Earth has more land, while the southern hemisphere has more water, tends to moderate the impact of differences in sunlight between perihelion and aphelion.
Sunlight raises the temperature of continents more than it does oceans. (In other words, land has a lower heat capacity than water.) In July (aphelion) the land-crowded northern half of our planet is tilted toward the Sun. Aphelion sunlight is a little weaker than sunlight at other times of the year, but it nevertheless does a good job warming the continents. In fact, say climate scientists, northern Summer in July when the Sun is more distant than usual is a bit warmer than its southern counterpart in January."
See: http://science.nasa.gov/headlines/y2001/ast04jan_1.htm?list117398
Actually, you make a similar comment on the top of the Page 54, so there's inconsistency between what's on the Page 54 and the 4 degrees C on page 49.
13. Page 52, Figure Caption.
I'd say: "Summer in northern hemisphere and winter in southern hemisphere. In the northern hemisphere, the Sun is higher in the sky. Its light is more concentrated on the Earth's surface there. At the same time, Sun is lower in the southern hemisphere, and the light gets spread out there, heating the Earth less efficiently."
14. Page 66, line 12 from the bottom:
"6 percent"
I've got 7%
15. Page 70, line 12 from top:
"The time of high and low tides changes every day by about a half hour"
Your explanation and calculation are correct, but the wording of the conclusion is a bit confusing. I'd say the morning tide tomorrow will be about 50 minutes later than the morning tide today, etc.
16. Page 73, line 5 from the top in the first paragraph;
"Tides on the Moon are 80 times…"
About 20 times, since diameter of the Moon is about 4 times smaller than Earth's diameter.
17. Page 79, line 20 from the top.
"The air bends the light up,"
See # 10 above.
18. Page 130, line 20 from the top:
"Moon has 20,000 times the tidal force of all the other planets"
It is perhaps worthwhile to add that the tidal force of all the other planets is mostly due to Venus alone, as the tidal force due to Venus is almost 9 times bigger than that generated by Jupiter. Many people think that it's Jupiter that contributes most to the tidal force of all the other planets!
19. Page 167, line 10 from the top:'
"He grabbed a rock weighing roughly a kilogram (two pounds)"
A kilogram is a unit of mass, not weight. A mass of one kilogram weighs about two pounds on Earth's surface, but only one-third of one pound on Moon's surface. Since the sentence refers to what happened on the Moon surface, this needs to be rewritten.
20. Page 178, line 1 through line 11.
"flung outwards by Jupiter's rapid rotation in the same way that a dog shakes its body to spray off water after a bath.
(…)
Jupiter would slow his own rotation every time this happened,"
Not necessarily. If Jupiter had shed some mass from the surface radially outward, it's rotational speed would have not changed. It's just a conservation of angular momentum. Imagine a merry-go-round with a dude riding on a rim. If the dude jumps off pushing away from the platform, the rotational speed of the platform is not affected. (You seem to hint at this on page 198).
On the other hand, if Jupiter ejected a mass radially out from the inside, than the conservation of the angular momentum dictates that its rotational speed would indeed have decreased. But then the dog analogy does not really apply here.
21. Page 181, the last paragraph:
"Worse, the tides from Venus on the Earth would be huge, kilometers high"
Better! Since Venus would be inside the Roche radius of Earth, the tidal force produced by Earth would be stronger than Venus own gravity and the Venus would disintegrate. And Earth would be inside Venus' Roche limit as well, so Earth would disintegrate too, and Velikovsky wouldn't be around to push his bunk.
22. Page 193, first line:
"Something caused this cloud to collapse"
Why not gravity? The Universe probably started as a lumpy, non-uniform mass distribution, so lumpier areas contracted faster than other.
23. Page 193, line 6 from the top:
"flattened due to centrifugal force and friction"
I'd prefer not to use a concept of centrifugal force, as it requires a prior explanation what a noninertial frame of reference is etc. I'd say due to" inertia and friction", or perhaps "due to angular momentum conservation and friction".
24. Page 214, 3-rd paragraph:
"Mars' gravitational influence on the Earth drops by a factor of more than 50 from one side of the sun to the other"
I've got a factor of about 23.
25. Page 214, 4-th paragraph:
"…the Moon has a gravitational effect on the Earth and you that is more than 50 times the combined gravity of planets".
This is correct, but you could push a limit a bit more: According to my calculations Moon's gravity is about 65 times stronger than combined gravity of all other planets even when they are all at the same time at their closest distances from the Earth, and how often does that happen!
26. Page 247, line 13:
"If some atom is sitting around minding its own business and another one comes along moving faster than sound, the first atom is surprised by it. It's literally shocked: it didn't know what was coming. When this happens to a lot of material it's called a shock wave."
I have a problem with that, since for example a speed of sound in air at room temperature (20 degrees C) is about 343 m/s, yet individual molecules comprising air move much faster. O2 molecule has a speed of 480 m/s, N2 molecule 513 m/s and H2O molecule 640 m/s, yet they do not produce a shock wave, obviously.
27. Page 249, line 11:
"This is called the centripetal force,"
This is called inertia. The car accelerates to the left, but the tendency of a passenger is to continue in a straight line. The centripetal force is a force pulling the car towards the center, which on a flat road is provided by a static friction between the roadway and tires. Likewise, for a rock whirled on a string, the centripetal force is provided by the string that pulls towards the center, etc.
"So, if a pilot flying the spaceship banks during the turn, the centripetal force is directed back, pushing the pilot harder against the seat."
Again, the centripetal force is towards the center of the turn. If the spaceship is not banked, the centripetal force on a pilot is provided by a harness (there's no friction, unless his pants are made from Velcro). If he banks the ship, the seat is pushing him at right angle to the seat, and a component of that push towards the center of the turn acts together with his harness and a friction force now present to provide the centripetal force.
28. Page 251, line 12 from top:
"…the nearest planet (is) about 25 million miles away"
The nearest planet periodically comes as close as 25 million miles.
29. Page 251, line 13 from top:
"…the nearest star to the Sun, Alpha Centauri"
The nearest star is Proxima Centauri at 4.22 light years, c.f. page 29, line23. Alpha and Beta Centauri are at 4.35 light years.
30. Page 252, line 3 from the top:
"…Oort cloud, the cometary halo that is almost a light year across."
Do you mean here the inner diameter of the Oort cloud, outer diameter, or its thickness?
Inner diameter is some 0.7 light year, outer diameter is about 3 light years, and thickness, indeed, about 1 light year.
31. Page 252, line 5 from the top:
"…a trillion kilometers from the heat and fierce gravity of the Sun"
An uninitiated reader might erroneously conclude that Sun's gravity does reach there!
32. Page 253, line 13 from the top:
"…even distant Pluto is 8,000 times closer"
Due to large eccentricity of Pluto's orbit, Pluto is between 5330 and 9330 (on average 6780) times closer to Earth than Proxima Centauri.