Silly but in spots hilarious, this is the latest Bad Lip Reading of clips from the NFL:
Link: http://youtu.be/OTRmyXX6ipU
by 
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Link: http://youtu.be/OTRmyXX6ipU
by Link: http://youtu.be/OTRmyXX6ipU
by Self-explanatory and only 20 seconds long.
Link: http://youtu.be/wtmI1FvRkek
This reminds me of the time I was trying to figure out why an LED flashlight would not light up and for some reason thought it would make sense to look directly into it while I worked the switch.
by British evolutionary biologist Richard Dawkins, who has also written books critical of religion, reads some of the charming emails he has received from offended believers. Be aware that many of these letters are from apparent professing Christians who haven’t quite got the hang of their religion. That is, the language may be offensive to those repelled by four-letter words, let alone bad grammar, usage, and spelling. On the other hand, the whole thing is rather hilarious.
Link: http://youtu.be/gW7607YiBso
Curiously, several correspondents seem to believe either that Dawkins is gay or that suggesting someone is gay is just about the worst thing one can say accuse them of. As it happens, he isn’t, and he’s married to artist, writer, and actress Lalla Ward, whom some may remember as co-starring on Doctor Who with Tom Baker, to whom she was also married for a while.
by As with my earlier post (link) about color subsampling, this is another essay about video technology that I expect to be of limited interest (though oddly enough that previous post is one of the more frequently viewed ones on this site).
If don’t particularly care how things worked in the analog world, you can skip the first part of this.
Analog interlacing
When broadcast electronic television was first introduced in the 1930s, engineers needed to deal with a number of problems simultaneously:
- Transmitting enough pictures per second to create an illusion of motion and to minimize visible flickering.
- Transmitting enough scan lines per picture and enough detail per scan line to produce a clear image.
- Transmitting no more cycles per second than absolutely necessary, so as to allow more TV channels in the available part of the broadcast spectrum.
More detail per scan line, more scan lines per picture, and more pictures per second all require more cycles per second, so obviously something had to give.
And the problem was worse than you might think. The minimum number of pictures per second needed to support an illusion of smooth motion (provided the speed of the motion isn’t too drastic) is about 16, though for compatibility with sound motion pictures it should ideally be 24 or some multiple of that.
However, to keep flicker from being visible, you need a minimum of about 50 pictures per second. (This varies from person to person and with the level of ambient light.) The earliest movies, shown at about 16 frames per second to save film, had awful flickering (which led to calling movies “flickers” or “the flicks,” which we still do today, though most audience members probably don’t know why). For a while Thomas Edison advocated making the frame rate much higher, but a cheaper solution was to interrupt the projector’s light beam two or three times per frame with a two- or three-blade spinning shutter, effectively flashing each picture onto the screen two or three times.
With early television, though, there was no way to store a picture inside the set and display it multiple times. In fact, for decades analog television consisted not of a series of images but rather a continuous spot of varying brightness scanned across the face of a cathode ray tube, leaving a trail of rapidly fading scan lines, and visible as pictures only because of our eyes’ persistence of vision.
Since the receiver and transmitter needed to be in perfect synchronization, there was a lot to be said (especially in the early days) for basing the scanning frequency on that of AC current — 60 Hertz (cycles per second) in North America and 50 in Europe, the two regions where broadcasting began. If you scan the screen 50 or 60 times per second, you need to somehow limit the detail in each scan if you want to hold down bandwidth.
The clever solution was to use a small number of scan lines per picture, but shift successive pictures up or down vertically by half a scan line, so that the scan lines in successive pictures “interlace.” This effectively allows the camera to capture and the eye to see about 40 percent more vertical detail out of the continuing stream of pictures than would be visible in any one of them.
To make this work, each picture (which in interlaced television is called a “field”) contained 242.5 scan lines in the American NTSC system or 287.5 in the European PAL. (For our purposes, SECAM is practically the same as PAL.)
I know, at first blush it seems downright bizarre to have fields with so-many-and-a-half scan lines, but that’s actually what makes the interlacing work! If the first scan line of a picture starts at the left edge, the last line in the picture is abruptly interrupted halfway across, and the top line of the next picture starts halfway across at the top. You can see a nifty picture illustrating the idea on David Stringer’s site (link).
That illustration, and with most others meant to describe how analog scanning works, shows the scan lines as very narrow. In reality, scanning is less like drawing lines with a sharp pencil than like painting with a flat brush. In a perfect analog television set, the scanning spot is tall enough that the scan lines of a field just touch each other, leaving no gaps. The scan lines of the next field don’t fill in the breaks in the previous field as diagrams and even some descriptions imply, because ideally there are no breaks to fill in.
Or to use another painting analogy, scanning a television screen is not like painting a wall with stripes and leaving gaps between them to fill in with the second coat; it’s more like painting a wall with horizontal stripes that just touch each other, then going back and painting a second coat of horizontal stripes, but this time positioning the paint roller so that its center rolls along the boundary between the stripes of the previous coat.
There are a couple of reasons for this, but the main one is to avoid a source of potential flicker. Suppose some very narrow bright bit of horizontal detail (or even a tiny dot) exists somewhere in the picture. If you left Venetian-blind gaps between scan lines when you captured the video, then that bright detail might appear in half the fields but fall into the gap in the other half. That means it would show up on the screen only every other field, flashing on and off at 25 or 30 times per second, slow enough for the resulting flickering (called “line twitter”) to be noticeable. If there are no gaps in the picture, that problem doesn’t exist.
In live television you can cut from one camera to another at any instant in time because the scanning for all the cameras is locked in perfect synchronization with a master sync generator (“genlock”). In analog switching there’s nothing wrong or even remarkable about cutting partway down a field. But consider what would happen if the cameras were not in sync: You might cut from the end of a scan line near the top of the picture from one camera to the middle of a scan line 2/3 down on the other camera. This would produce a noticeable glitch on the screen.
The same problem exists for editing analog videotape, except that it’s even worse because of the way the signal is physically laid out on the tape in diagonal stripes (something done in pretty much all tape-based video recording systems to avoid having a ludicrously high linear tape speed). This makes it necessary to cut between fields, and there’s even a restriction on that: You can’t edit it such a way that an upper field is followed immediately by another upper field or a lower field by another lower one. The up-down-up-down march of fields has to be maintained to prevent glitches on the screen.
That means you have to cut consistently, either always between a lower field and an upper one, or always between an upper field and a lower one. This choice is called “field dominance,” and if you’re ever cursed with having to use a tape-base linear editing system you may even have a switch that lets you exercise your own preference rather than the manufacturer’s.
Since it takes a pair of fields to complete a full lower-upper or upper-lower cycle, for many purposes (not just editing but even simply describing the details of the analog television signal) it makes sense to treat a pair of fields as a unit, termed a “frame.” (But keep in mind that in interlaced television, a “frame” is really two successive pictures.)
You may recall hearing that NTSC has 525 scan lines per frame. Half of 525 is 262.5, but didn’t I just say than an NTSC field has 242.5 scan lines? Yeah, I sort of did, and that’s because I left something out: It takes a tiny bit of time to reset the vertical sweep to start drawing the next field at the top of the screen, so each field includes 20 “scan lines” (or more precisely, cycles of the horizontal oscillator) that don’t really scan anything.
Similarly, in the 625-line PAL system, the vertical blanking interval (as it’s called) takes 25 scan lines per field.
Converting analog video to digital
Remember that an analog field either ends halfway through the bottom scan line or starts halfway through the top one. Since a PAL field has 287.5 scan lines, a frame has a total of 574 full scan lines plus two half lines. To capture them all, digital PAL video has 576 pixel rows per frame.
Similarly, a frame of NTSC analog video has a total of 484 full scan lines and plus two more half-lines, and the original digital standard for NTSC prescribed frames with 486 pixel rows. However, for purposes of compression, it’s helpful to make the number of pixel rows a multiple of 16. Since television sets are normally set to overscan (that is, the picture is little bit larger that the part we see), in practice most NTSC digital video discards a few analog scan lines and uses just 480 pixel rows.
Digital Interlacing
Digital interlacing serves the same purpose as analog interlacing: allowing higher effective vertical resolution for a given number of scan lines per field. In addition, it makes it simpler to convert interlaced analog video to digital.
As far as I know, there are only three interlaced digital formats in actual use:
- 480i (compatible with NTSC),
- 576i (PAL), and
- 1080i (“full” HD, or not quite).
The “i” suffix stands for “interlaced” (duh). Note, incidentally, that the number before the “i” or “p” is always the number of lines (pixel rows) per frame, not per field, even in the case of interlaced video.
Non-interlaced video is usually given a “p” suffix, as in 480p, 576p, 720p, and 1080p. (There’s no 720i in current use that I’m aware of.) The “p” stands for “progressive,” but it strikes me as a bit of a misnomer. “Progressive” ought to mean that the picture is scanned one line after another, but that’s true of all video when captured with “rolling shutter” CMOS chips or the old tube-based imagers, whereas CCDs and “global shutter” CMOS chips capture all the pixels at once, whether shooting interlaced or “progressive.” Be that as it may, we appear to be stuck with using “progressive” (and the “p” suffix) to mean “non-interlaced.”
A single 1080i field contains 540 rows of 1920 pixels per row. As with analog video, a pair of successive fields are termed a “frame,” but there’s more to it than just treating them as a unit for purposes of editing. A 1080i digital frame holds a full array of 1920×1080 pixels (just like a 1080p “progressive” frame), with the odd-numbered rows supplied by one field of the pair and the even-numbered ones by the other. You might suppose that’s how the video is captured and shown on the screen as well, but it’s not, or at least it’s not supposed to be.
To belabor the point, remember that interlaced video is a series of fields. Fields are paired together to make frames for purposes of storage and editing, but the fields are still separate pictures. When you shoot or view interlaced video, you’re capturing or seeing 50 or 60 pictures per second.
The standard in NTSC countries (North America, Japan, South Korea, Taiwan, the Philippines, parts of South America (including Brazil where the standard is confusingly called PAL-M), and a few other places) is 60 pictures (fields) per second. The rest of the world uses 50 fields per second. You will often see this referred to as 60i or 50i, or sometimes combined with the number of pixel rows per frame into a single designation such as 1080i60.
To be precise, NTSC runs at slightly less than 60 fields per second. For arcane technical reasons the introduction of color in the 1950s required slowing the field rate by a factor of 1000/1001, to about 59.9400599401 fields per second, which for obvious reasons is usually rounded to 59.94 or just plain 60.
When you watch interlaced digital video, your television set needs to extract the two fields from each frame and show them to you one after the other — preferably in the correct order! If you watch interlaced video on a computer screen you might sometimes see it displayed as if it were progressive. That is, you see not a field at a time but a frame at a time, with the two fields interwoven. If there’s motion in the frame you get what looks like the teeth of a comb. To avoid that you need to use a video player designed to handle interlaced video, or else the video has to be “de-interlaced” or turned into progressive video. Doing a good job of that requires some fairly sophisticated software.
Material originally shot on film or non-interlaced video at 24 fps is sometimes converted to 60i, a process referred to for historical reasons as “telecine.” Some smart players, hardware and software, can “de-telecine” this 60i video back to 24p.)
As explained in more detail in the section on analog interlacing, it’s not true (as some descriptions of interlacing suggest) that the scan lines of a field have gaps between them, like looking through a Venetian blind. In fact, the 540 rows are expanded into 1080 for viewing, either by doubling or (ideally) by interpolating new rows to fill what would otherwise be gaps.
Roughly the same thing happens when shooting interlaced video with a digital camera: The imager captures a full 1080p picture, then each pair of rows is averaged together to reduce it down to 540 scan lines.
If you always paired the same two rows with a given scan line, you wouldn’t have interlacing, just video with half the vertical resolution. So instead, successive fields alternate how the pixel rows are combined. That is, in one field, the rows are paired odd-even and in the next field even-odd. (What about a row left over at the top or bottom? Typically there are some extra rows on imaging chips so nobody is left without a dance partner. Or the unpaired row can just stand by itself; it’s not likely you’d notice. With many televisions you don’t seen the full raster anyway, which you can blame on those dang historical reasons that keep cropping up.)
That’s basically it. There are still complications, of course, many of them having to do with the way compression works, but that, as they say, is beyond the scope of this discussion.
The main thing to know about interlacing is not to use it unless you have a very good reason. As a rule DSLRs don’t even give you the option of shooting interlaced. For most purposes 24p is the best choice since most movies are still shot that way (whether on film or digitally) and pretty much any video delivery medium from broadcast to disk to Internet streaming is capable of handling 24p.
On the other hand, some video cameras (especially older ones) force you to shoot interlaced, and old video may come to you in interlaced form. Though there are exceptions (mainly in broadcast television), you will usually want to de-interlace interlaced video, not least because it looks awful when viewed on the Internet. If the material was originally shot on film and converted to interlaced video you may alternatively need to de-telecine. Doing a good job of either requires decent software. A good free option is the open-source Handbrake (link), which features both de-telecine and a smart de-interlacing filter called “decomb.” For high-end de-interlacing I’ve heard good things about FieldsKit from RE:Vision (link) but never used it myself.
(In an earlier version of this post I wrote “VLC” when I meant “Handbrake.” Sorry about that. They’re both free and both worth getting, since they have different but overlapping purposes. Consider making a donation to the developers to encourage them to keep updating the products.)
I hope this has been useful for somebody, and as always I welcome comments and corrections telling me how wrong I am. (I’ve already revised this post multiple to correct various misstatements I managed to catch myself on second and third reading, not to mention lots of typos. I hope I haven’t left in anything too serious.)
by How would Mars, Venus, Neptune, Uranus, Jupiter, and Saturn look from the Earth’s surface if they were as far away as we are from the Moon?
Link: http://youtu.be/usYC_Z36rHw
For details, including a concise explanation of how it was made, click on the link above.
Mercury is omitted because it’s only a bit bigger than the Moon and with its cratered surface it would look a lot like the Moon. The Earth would look like Venus except a little dimmer and much more colorful and interesting. (The surface of Venus is hidden beneath an almost featureless cloud layer.)
by [Updated to add a second clip.]
As you’ve no doubt heard, Fox New finally apologized several times for its credulous interview with terrorism “expert” Steven Emerson, who claimed that Birmingham, the second largest city in England, is under the control of radical Muslims and that non-Muslims do not dare enter. (See for example this item from Britain’s Independent newspaper.) In reality, Birmingham does have a relatively large Muslim population, but it’s only about 22 percent of the population.
Emerson had already rather abjectly apologized several days before, calling his false claims inexcusable. This isn’t the first time Emerson has been off the mark, as another article (link) in The Independent pointed out. Among other things, in 2013 he claimed to have inside knowledge that a Saudi carried out the Boston Marathon bombings (the accused bombers turned out to be Chechens) and in 1995 he told CBS News that the Oklahoma City bombing was characteristic of Middle Eastern terrorism (it was carried out by anti-government Americans). Twitter users responded with the #FoxNewFacts hashtag making up their parody Fox News items, but best single remark I saw was from James Gleave (@jamesgleave1), who wrote, “The Fox News guy has apologised and called the city of Birmingham ‘beautiful’. The guy can’t get anything right, can he?”
Fox News also apologized for a different interview with a different “expert,” Nolan Peterson, who made similar suggestions about areas of Paris. A French comedy news show called Le Petit Journal did a report on this, sending brave journalists into the areas in question to ask residents if their areas were really like Iraq and Afghanistan, as Peterson alleged:
Of course, Fox News has never been noted for factual accuracy, but that hasn’t kept them from being the highest-rate news channel on cable in the U.S.
Here’s another clip from the same program, this one showing a couple of pretend Fox News reporters in a panic when they see that their taxi driver has a “Muslim beard” and that couscous is sold openly. The intro is in French but the “reporters” themselves speak imitation American English, so you shouldn’t have any trouble understanding them.
by The Berkeley Earth project (link), a scientific organization founded by global warming skeptics and devoted to independent analysis of global temperature data, agrees with the Japan Meteorological Agency and with NASA and NOAA in the U.S. that the year 2014 was likely the warmest since reliable records began in 1850.
Their report on 2014 (link to PDF) is careful to note that taking into account the statistical margin of error, it is not completely certain that 2014 was warmer that the next warmest years, 2005 and 2010. The overall pattern still seems clear, however.
(As astronomer Phil Plait noted in a blog post I mentioned yesterday [link], NASA’s calculations also show a large enough margin of error to allow for the possibility that 2005 or 2010 was as warm or warmer, though NOAA’s results, computed slightly differently, show 2014 as definitely the hottest.)
The Berkeley Earth Surface Temperature (BEST) project, as Berkeley Earth was originally known, was founded in early 2010 by Richard A. Muller, a physicist, and his daughter Elizabeth Muller, a consultant on energy policy and managing partner of Global Shale, a company involved in shale gas exploration and hydraulic fracturing (“fracking”). At the time, Richard Muller agreed with other global warming skeptics (few of them scientists) that the historical global temperature series assembled by climatologists weren’t entirely reliable owing to such potential sources of error as the supposed urban heat island effect. Hence the BEST team set about creating a massive, independent global temperature database intended to correct what they perceived as possible or probable flaws in previous research.
The project was funded with grants from a variety of sources, with the most controversial one being the Charles G. Koch Foundation. Charles Koch and his brother David, whose large fortunes are derived from fossil fuels, are widely known for disputing the reality of global warming and also for making huge political donations in support of conservative candidates. However, according to Muller, the foundation’s grant came with no restrictions or interference.
In 2011, when BEST had not yet published conclusions, Muller assured The Guardian newspaper (link), that “We are bringing the spirit of science back to a subject that has become too argumentative and too contentious. We are an independent, non-political, non-partisan group. We will gather the data, do the analysis, present the results and make all of it available. There will be no spin, whatever we find.” And this appears to be exactly what they did.
In June 2012, Muller wrote an op-ed for The New York Times (link) that began,
Call me a converted skeptic. Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.
My total turnaround, in such a short time, is the result of careful and objective analysis by the Berkeley Earth Surface Temperature project, which I founded with my daughter Elizabeth. Our results show that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases.
These findings are stronger than those of the Intergovernmental Panel on Climate Change, the United Nations group that defines the scientific and diplomatic consensus on global warming. In its 2007 report, the I.P.C.C. concluded only that most of the warming of the prior 50 years could be attributed to humans. It was possible, according to the I.P.C.C. consensus statement, that the warming before 1956 could be because of changes in solar activity, and that even a substantial part of the more recent warming could be natural.
Our Berkeley Earth approach used sophisticated statistical methods developed largely by our lead scientist, Robert Rohde, which allowed us to determine earth land temperature much further back in time. We carefully studied issues raised by skeptics: biases from urban heating (we duplicated our results using rural data alone), from data selection (prior groups selected fewer than 20 percent of the available temperature stations; we used virtually 100 percent), from poor station quality (we separately analyzed good stations and poor ones) and from human intervention and data adjustment (our work is completely automated and hands-off). In our papers we demonstrate that none of these potentially troublesome effects unduly biased our conclusions.
It should be noted that Muller still holds views somewhat outside the scientific mainstream on some aspects of global warming and the consequences of the resulting climate change. But skepticism is an important part of science, and when skeptics independently investigate a phenomenon and replicate earlier results, that makes those results that much more convincing.
Update: For a short video from an interview with Muller describing the work and the conclusions, see this more recent post.
by The U.S. National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration (NOAA) have announce that the year 2014 was the warmest on record (link).
This is in keeping with an analysis already published by the Japan Meteorological Agency, as I mentioned in an earlier post (link).
The ten hottest years on record go back only to the late 1990s. In contrast, Earth hasn’t had a record-setting cold year in more than a century.
Here’s a video from NASA summarizing their results:
Link: http://youtu.be/-ilg75uJZZU
Astronomer Phil Plait as a post about this on his Bad Astronomy blog (link). He makes the same point I did in a post January 8 (link), namely that there was no El Niño in 2014 to explain anomalous warming. (In contrast, an unusually strong El Niño was a contributing factor in 1998, the hottest year of the 20th century.)
by The Falcon 9 rocket from the private SpaceX corporation recently delivered another Dragon capsule full of supplies and experiments to the International Space Station. But this time SpaceX tried something new: a very preliminary test of a system intended to permit the eventual recovery of the rocket’s first stage so that it can be refurbished and reused, something that would save a lot of money.
SpaceX said well in advance that the attempt probably wouldn’t succeed on the first try, but it came remarkably close: The first stage, steering itself, managed to find the target recovery barge and even touch down on its deck, but the steering fins ran out of hydraulic fluid, and the rocket came down hard at an angle and crashed — rather spectacularly in fact. If you want to hear the accompanying sound effects, click on the speaker icon at the bottom of the video to unmute, but you might want to turn your volume down for your first viewing.
As Phil Plait writes on his Bad Astronomy blog (link), it’s very misleading to call this a “failure,” and it’s great that SpaceX founder Elon Musk has a sense of humor about it, sending the following Tweets
@ID_AA_Carmack Full RUD (rapid unscheduled disassembly) event. Ship is fine minor repairs. Exciting day! pic.twitter.com/tIEctHFKHG
— Elon Musk (@elonmusk) January 16, 2015
Next rocket landing on drone ship in 2 to 3 weeks w way more hydraulic fluid. At least it shd explode for a diff reason.
— Elon Musk (@elonmusk) January 16, 2015
by This is yet another one you might have seen already, albeit in possibly abbreviated or confused form. It’s a mix of hilarious and appalling.
QVC is a television shopping channel based in the U.S. (I could describe it in more detail, but I can’t stand to. Besides, there’s a pretty good explanation of it in the first clip below.) This particular program features fashion designer Isaac Mizrahi and host Jane Treacy. At one point Treacy is talking about a particular piece of fashion and suggests the fabric pattern looks like the Earth seen from a bazillion miles away, as from “the planet Moon.” She quickly corrects herself, saying that the Moon is not a planet after all.
Mizrahi disagrees, asserting that it is too a planet, but Treacy maintains she’s pretty sure it isn’t. It’s most likely a star, she says, because, you know, the Sun is a star, and also she remembers learning the names of the planets in school, “and there was Uranus, there was Saturn, and the one with the rings,” and she’s pretty sure the Moon wasn’t on the list.
Mizrahi asked someone called “Chunky” to “Google the Moon,” and eventually someone off-camera announces that the Moon is a “natural satellite.” I’m not sure whether this was the result of Googling the Moon or perhaps someone on the technical crew was not an idiot, but there you have a pretty good response, not that it seemed to be much help.
Meanwhile, a fashion model can be seen near the right of the screen covering her face with her hands.
The first video below is from MSNBC’s Rachel Maddow Show. Maddow (who has a doctorate from Oxford) finds the whole thing hysterical and possibly one of the best moments in television history, so she gives it rather too long a setup. But if you skip past the first two minutes, you can see the QVC clip pretty much without interruption. If you want a more abbreviated version, see second video further down.
Link: http://youtu.be/s_5j1mVE8Sk
The second clip is from ABC. It shows a few key moments of the QVC discussion followed by a quick interview with someone at the Griffith Observatory followed by some reasonably bright kids and unreasonably dim adults. Then the reporter, apparently terrified of being thought a nerd for actually remembering anything he learned in grade school, jokes about not having known himself what the Moon was. (What is it about this country that even a basic level of knowledge treated as something shameful or embarrassing?)
Link: http://youtu.be/xGoZZvfEd6A
If you’re wondering how people illiterate in science can not only be elected to Congress but appointed to head committees focusing on science and technology (see this earlier post), here’s part of the reason why.
Incidentally, thinking of the Moon as a “planet” isn’t entirely unreasonable. While the International Astronomical Union wouldn’t call it that, our Moon (3475 kilometers in diameter) isn’t much smaller than the planet Mercury (4880 km) and is a lot bigger than former planet Pluto (estimated to be about 2300 km). Also, the Moon’s diameter is about 1/4 that of Earth’s, and no other moon in the solar system is remotely as large in comparison with its associated planet. The Earth-Moon system has sometimes even been referred to as a “double planet.” A star, on the other hand, is a glowing ball of plasma, a different sort of thing altogether.
Update: Astronomer Phil Plait just published a post (link) on his Bad Astronomy blog this that’s a little more forgiving than I am.
He also makes a good point about humans’ tendency to want sharply defined categories when the boundaries in practice are often fuzzier. In more or less the same vein, it occurred to me a long time ago that it might make sense to classify gas giant planets (Jupiter, Saturn, Uranus, Neptune, and their like in other solar systems) separately from the much smaller rocky planets (Mercury, Venus, Earth, and Mars). There’s some arbitrariness in deciding what to group with what. But as Plait emphasizes, our rocky, stable Moon is vastly different from a star.
by