Space: Stars, Solar Systems, Galaxies, and Such

I had been mulling over making a post on this topic when I saw this story in my Facebook newsfeed.  A new galaxy, tiny and dim, has been discovered orbiting our own.  That was a fascinating piece of news, and it confirmed my intention to write about the topic of space.  More specifically, I want to discuss how the structure or layout of space seems to be widely misunderstood, even by some writers of science fiction.  In this regard, this post is a sort of follow up to this one and this one.  Thus, let us now boldly go into space and see what we’ll find there!

Since October 4th, 1957, with the launching of the Soviet satellite Sputnik 1, the first artificial satellite to be sent by humans into Earth orbit, we have lived in the Space Age.  Press coverage of space and space travel seemed wall-to-wall throughout the 1960’s and into the early 70’s.  Space figured largely in pop culture, too, with the 60’s giving us Star Trek and the monumental 2001:  A Space Odyssey.  With time, the allure wore thin and the extraordinary became humdrum.  Still, over sixty years later, we are more deeply connected to the inventions of the space program than ever before.  Cell phone signals, Internet transmissions, and GPS all depend on satellites to function.  Many of us get satellite TV as a matter of course.  There has even been a resurgence of interest in space in both pop culture and reality.  In the former, the Star Wars and Star Trek franchises, after periods of dormancy, have re-started.  In the latter, Elon Musk is making plans for manned travel to Mars, while various government sources have spoken of returning to the moon and of founding a military “space force”.

Given all this, one would assume a certain amount of science literacy regarding space.  Certainly in the beginning of the Space Age, there was a strong push towards what we’d now call STEM (science, technology, engineering, and mathematics) education, out of fear of the head start of the Soviet Union in space.  With space more integrated into our lives than ever, a permanent international space station in orbit, and the aforementioned space exploration plans, it would seem more imperative than ever that we have a good grasp of science and terminology of space.  Most particularly, one would expect such science literacy from the writers of science fiction, which is perhaps the most characteristic genre of our age.  Alas, that seems to be far from the case.  Thus, along the lines of previous posts of mine which detail areas in which sf writers often fall short, I want in this post to look at some of the basics of space.

To start with, in speaking of space, we have–well, space.  It’s hard for us to grasp, but the vast majority of space has very little in it.  The typical density of interstellar space, for example, is about one atom per cubic centimeter.  A cubic centimeter is about the size of a sugar cube or a die (one of a pair of dice, for those who don’t know the singular form!).  In some areas of space, the density can be as low as 0.1 atoms per cc (cubic centimeter).  That means one atom for every ten cc’s (imagine ten sugar cubes or dice stacked in a tower–one atom in all that space they take up).  Now by way of comparison–a sugar cube has about 2.437×1045 molecules of sugar (each molecule of sugar contains 45 atoms, so the number of atoms would be forty-five times higher; but at this magnitude, we won’t worry about that).  This means 2,437,000,000,000,000,000,000,000,000,000,000,000,000,000,000 molecules!  This number, by the way, is two quattuordecillion, four hundred thirty-seven tredecillion!  To put it another way, it is two billion, four hundred thirty-seven million billion billion billion billion.  To put it  yet another way, this number is a thousand billion billion more than the estimated number of stars in the entire observable universe!  Compare such a gigantic number for the number of molecules in a mere sugar cube with the count of a single atom in the same volume of interstellar space.  Space is indeed very nearly empty!

Within that emptiness, though, there are various different structures of various sizes. These, by the way, are where would-be sf writers often tend to get things wrong–sometimes very much wrong.  The lowest level of actual structure is the solar system.  A solar system is any star–such as our own sun–and the various objects orbiting it as a result of its gravitational attraction.  This would include planets, dwarf planets, asteroids, comets, dust, and so on.  Solar systems will vary in size according to the star in question of course, larger stars having stronger gravitational fields, and smaller ones having weaker fields.  Our own solar system is estimated to have a diameter (depending on the exact definition and estimate) of between fourteen and twenty-three billion miles.  To give an idea of just how big this is, the greatest speed ever achieved by any human beings throughout history was approximately twenty-five thousand miles per hour for a brief period when the damaged Apollo 13 capsule was returning to Earth.  This is so fast that you could circle the whole globe in less than a single hour.  Even at that speed, though, which has never been duplicated, it would take about a hundred three years to cross from one edge of the solar system to the other!

That’s the other thing people don’t understand about space besides its emptiness–they don’t get its vastness.  Even the distances in our own solar system–that which contains the closest things to us in the universe–are far beyond any normal human scale.  Outside our own solar system, distances are even less comprehensible.  The nearest soar system to our own, the Alpha Centauri system, is 4.37 light-years from us–that is, at the speed of light, which is 186,282 miles per second (which would get you to the moon in just above two seconds), it would take four years, four months, and two weeks (approximately) to get there.  Now, at the aforementioned 25,000 miles per hour, the fastest speed at which humans have moved to date, it would take about one hundred fourteen thousand years to get to Alpha Centauri!  No wonder, in the original TV version of Lost in Space, the Robinsons were in suspended animation!

A quick aside.  Until fairly recently, it was debated whether most stars actually had a solar system surrounding them, or if our sun was anomalous in this respect.  From what we understood about stellar formation, it seemed highly likely that most starts did form planets; but there was no way of knowing; and it’s bad to generalize from a single data point, to wit, us.  With improved technology, though, this debate has been laid to rest.  The first confirmed discovery of an “exoplanet”–a planet of a sun other than our own–occurred in 1988.  As of July 2018, there has been a total of 3797 confirmed exoplanets.  The general consensus now is that solar systems are far and away the rule, not the exception.

The next level of structure in space is the galaxy.  “Galaxy” was originally a proper noun, referring to our own galaxy.  The faint, whitish band that we can see in the sky, which is part of our galaxy, was fancied by the Greeks to be “milky” in appearance, and was believed in myth to be milk spurted from the breast of Hera–hence “galaxias” (γαλαξίας), “milky”; hence our own Milky Way.  Now “galaxy” has become a common noun, referring to any large, oval collection of stars such as our own Milky Way.  Our own galaxy is average sized, being about one hundred thousand light-years in diameter, and containing one hundred to four hundred billion stars (depending on estimates).  At the Apollo 13 speed of 25,000 miles per hour, it would take 2.6 billion years–about half the age of Earth–to cross the Milky Way.  Thus, it is obvious that a Galactic Empire, such as that of the Star Wars franchise, or of Isaac Asimov’s Foundation series, would require forms of transportation and communication unimaginably far beyond anything we can conceive of at the present (to say nothing of needing some kind of major workaround of physical laws that, as currently understood, would make such an empire impossible).

Smaller clouds (nebulae), galaxies, and galaxy-like structures (as mentioned in the first paragraph above) may orbit “full-sized” galaxies.  The Magellanic Clouds, for example are dwarf galaxies orbiting our own at a distance of 160,000 to 200,000 light years.

The next level of organization, and the largest that is usually discussed is a galaxy group–that is, a group of galaxies relatively close to each other, held in proximity by gravitational attraction.  The possibility of larger groupings–groups of groups, so to speak–has been suggested, but to the best of my knowledge, never widely accepted.  Our galaxy belongs to what is not surprisingly referred to as the “Local Group”, consisting of fifty-four galaxies, dwarf galaxies, and satellite galaxies.  The nearest member of the group to us, discounting our satellite galaxies, is the Andromeda Galaxy, which is about 2.5 million light years from us.  The diameter of the Local Group is about 10 million light years.  Once more going at 25,000 miles per hour, it would take sixty-five billion years–sixteen times the age of Earth and five times the age of the entire universe–to get to the Andromeda Galaxy, and two-hundred sixty billion years–about twenty times the age of the universe–to cross the Local Group from one end to the other.  And this is the Local Group!

This is an overview of the various spatial entities–solar systems, galaxies, dwarf galaxies, satellite galaxies, and galactic groups–that we see in space.  In the heyday of pulp magazines and black-and-white serials–Buck Rogers, Flash Gordon, and such–there was no concern for scientific accuracy.  They were portraying cool adventures in space–who cared about all the science stuff?  Science fiction literature gradually matured, and most stories written after the Second World War at least attempted a modicum of accuracy and mainly avoided howlers.  As has long been the case, it took awhile for developments in literature to be reflected in cinema.  By the time you got to the late 1960’s, Star Trek had its space terminology and science–imaginary and otherwise–amazingly accurate.  Aside from the psychedelic coda, representing aliens far advanced over us, the seminal 2001:  A Space Odyssey contained some of the most scientifically accurate scenes ever filmed.  In fact, fifty years later, it is still one of the most scientifically accurate movies of all time.

Most major franchises since then have managed to be fairly accurate.  Star Wars takes place within a single galaxy, with the implication that other galaxies are out of reach.  To have a galaxy-wide empire is not exactly plausible–even Star Trek didn’t do that, with the size of the galaxy becoming a plot point in different ways in Deep Space Nine and Voyager.  Still, at least Star Wars managed to make it not insanely implausible.  It was, for example, pointed out in A New Hope that T.I.E. fighters were short-range (although Luke’s X-Wing fighter, presumably equivalent to a T.I.E. fighter, somewhat implausibly seems capable of interstellar flight in The Empire Strikes Back).  The issue of distance is addressed, with interstellar flight being accomplished with hyper-drive.  There is even a proper understanding of solar systems, with the thug in the Mos Eisley cantina in the first movie telling Luke that he has the death sentence on “twelve systems”.  Nice touch!  Of course, it’s cancelled by Han Solo’s misuse of “parsec” as a unit of time rather than of distance, but nothing’s perfect.  Actually, this is made up for by the accurate implication of time dilation, which is necessary to explain the timeline of The Empire Strikes Back; but I’ll save that for a separate future post.

The science was never much alluded to, and was in fact a bit vague, in the original version of Battlestar Galactica.  The remake, though, was much better.  It even adopted Isaac Asimov’s concept of making discrete “jumps” through hyperspace, rather than continuous flight through it, as in Star Wars.  The jump model is somewhat more plausible, in my mind.  The various iterations of the Star Trek franchise have relied increasingly on technobabble, said babble becoming increasingly baroque and opaque.  The J. J. Abrams reboot movies have had less technobabble, but less science, too.  Ah, well–how the mighty have fallen.  I have not yet seen Discovery, so I cannot comment on it, though a couple of things I’ve heard make me raise my eyebrows a bit.

The only significant sf show that I’m aware of that took place in multiple galaxies without misunderstanding what a galaxy is was the 2000-2005 TV series AndromedaThe series is explicit that the Commonwealth–a literally intergalactic confederation–exists in the Milky Way, Triangulum, and the eponymous Andromeda galaxies.  Ships travel the gigantic distances involved through the Slipstream–the Andromeda universe’s equivalent of hyperspace.  I’ve complained in the past about sf stories that use the term “intergalactic” without seeming to understand what that means–that is, between galaxies, or from one galaxy to another.  In such cases, the intended meaning seemed to be “intragalactic” (within one galaxy), or better yet, just “galactic”.  Andromeda is the only franchise I know of that used the term “intergalactic” properly and which also gave a rationale as to how such a Commonwealth could work.

Thus, for the major sf franchises, the science, by and large, is fairly accurate.  One glaring exception is the Netflix reboot of Lost in Space.  In the course of the series, it is made clear that the Jupiter 2 uses liquid fuel.  This is as part of a plot device in which the crew is racing against time to defeat parasitic worm-like space creatures who feed on the ship’s fuel reserves.  Yeah, sounds like something from a schlocky 50’s movie–sigh.  Anyway, there is no possible way that an interstellar craft would use liquid fuel in chemical rocket engines. Consider–it would take six thousand pounds of typical liquid fuel to accelerate a one pound payload to a mere 0.1 of the speed of light–poky, by interstellar standards, but probably the slowest you’d want to go.  I can’t find any specs on the ship from the series reboot.  However, from watching the series, I assume the Jupiter 2 is about fifty feet in diameter and about thirty feet tall, which gives a volume of about 60,000 cubic feet.  The teensy little Apollo lunar landing modules had a volume of 235 cubic feet and a weight of 36,000 pounds.  Assuming the Jupiter 2‘s dimensions are in proportion to those of the lunar module–probably a wrong assumption, but we’ll go with it–we get about 900,000 pounds (450 tons).  That seems like a low estimate, but as I said, we’ll go with it.  That means that to accelerate the Jupiter 2 to one tenth of lightspeed, you’d need 5.4 million pounds of fuel, or almost 800,000 gallons.  This would require storage space of 108,000 cubic feet–almost double the whole volume of the ship itself, as we calculated above!

My wife suggested that the Jupiter ships were short-range, as they seem to be carried in berths on a lager transport.  That’s fair.  Still, that won’t work.  The Jupiter 2 is shown lifting off from a planet and breaking free from its gravity.  That takes lots of fuel.  The Space Shuttle weighed about 4.5 million pounds (much more than the above estimate for the Jupiter 2, which indicates that my estimate was ridiculously conservative), and to launch into Earth orbit required a total of about 3.8 million pounds of fuel–that’s what the huge tank and side boosters were for.  If the ratio of fuel to ship mass were the same, the Jupiter 2 would need 756,000 pounds of fuel–more than that, since it could break orbit.  This would occupy around 15,000 cubic feet, around a fourth of the entire capacity of the ship.  That’s only for breaking orbit once–no extra amount for safety, no maneuvering, no landing, no nothing.  Also, given the comparison with the space shuttle, it seems my estimates were insanely optimistic, and I suspect at least an order of magnitude more of fuel–far more than the ship could carry–would be necessary.

Issues such as this are the reason that no serious proposal for interstellar travel involves liquid fuel (or even solid fuel) rockets of the type existing spacecraft use.  All serious proposals for interstellar flight assume some form of nuclear fusion, ultralight ships with solar sails driven by solar particles or powerful lasers, or, more speculatively, matter-antimatter annihilation.  Solar sails would probably not be workable for manned spacecraft; and whether fusion or matter-antimatter engines will ever be practical (or in the latter case, even possible) is currently unknown.  Even with nuclear fusion, the amount of fuel, in the form of hydrogen, that would need to be carried onboard would still be immense.  This is why some have proposed plans, such as the Bussard ramjet, to collect hydrogen from space.  Matter-antimatter engines could actually produce sufficient energy from quantities of matter and antimatter small enough to actually carry onboard, given the extremely high amount of energy released by matter-antimatter annihilation.  Whether antimatter could be found or produced in sufficient quantities and in an economical fashion, and if so, whether workable matter-antimatter engines could actually be built, is unknown.

To their credit, most of the franchises we’ve discussed have tried to be accurate–both Star Trek in its various forms and Andromeda have ships powered by matter-antimatter engines–or have avoided the issue of power altogether (as with Star Wars).  I would have thought that Lost in Space could have done a little better.  Anyway, to put this all into perspective, courtesy of here, accelerating one ton to one-tenth of the speed of light requires at least 125 terawatt-hours; and world energy consumption 2008 was 143,851 terawatt-hours.  Don’t worry about the units–you don’t have to know what a “terawatt-hour” is.  Note the point:  To get a single ton accelerated to a mere one-tenth of lightspeed would take an amount of energy equivalent to 125 divided by 143,851 times one hundred, or roughly 0.1 percent of Earth’s yearly energy use.  That might not seem impressive; but the above-mentioned Space Shuttle’s weight in tons is 2250.  Thus, to accelerate a Space Shuttle to ten percent of the speed of light, you’d need 2250 times 0.1, or  225 percent of Earth’s power consumption.  That is, to accelerate a Space Shuttle to a paltry tenth of the speed of light would take two and a quarter times the entire yearly energy consumption of our whole planet.  Of course, when you got to the end of the journey, you’d have to decelerate, which would require the same amount of energy again.  Liquid fuel is not going to cut it!

I’ve complained before about some schlocky sci-fi romances I’ve read lately.  Two seemed very fuzzy on just what a galaxy is.  None had any concept of how long space travel takes (to be fair, that’s true from some of the more prestigious movies and series I’ve mentioned above, at times).  One had the alien protagonist originate from a planet two galaxies over from ours.  Two galaxies over.  That would be millions of light years.  The alien protagonist’s people at one point–apparently, as the text isn’t clear–teleport to Earth all the way from their own planet.  Despite this, which indicates a technology that it is no exaggeration to call godlike, the aliens’ culture still uses spaceships.  That would be like us still maintaining the Pony Express!  Further, a plot point is that an asteroid from the Earth system is going eventually to crash into the aliens’ planet–which is millions of light years away.  At subluminal (slower-than-light) speeds (and it’s clear from the story that the asteroid is knocked out of orbit by Earthlings with conventional technology, and thus at way subluminal speeds), the sun and the aliens’ sun would have long since burned out and the two civilizations died out or moved to some other planet before the asteroid was anywhere near the alien world.

I realize it might be swatting flies with a cannon to be complaining about scientific errors–even egregious ones–in a schlocky romance (or for that matter, even in Star Wars–it’s just an adventure movie, so who cares if George Lucas knew what a “parsec” was?).  On the other hand, as I pointed out earlier in this post, science plays a bigger role in our daily lives than ever before.  Not everyone has to be an Einstein, of course; but one would expect we’d have a little understanding of square one, basic concepts in science.  Despite this, we have the anti-vaccination movement; a resurgence of Flat-Earthism; the contention that the moon landings were faked; 9/11 Trutherism (the assertion that the Twin Towers were blown up by sinister but nebulous government forces as part of an inside job); and any number of other cockamamie notions floating around and sometimes even given a modicum of respect. Sometimes it’s enough to make one–at least, someone of my generation–despair.  As I’ve discussed before, there was a time when science popularization was a noble endeavor, and people actually respected scientists and cared, at least to some extent, about actually learning, even if only a bit, about science.  It is true that science is now in a bit of crisis, with replicability, a crucial component of the scientific method, seemingly becoming ever scarcer.  Still, we shouldn’t throw out the baby with the bathwater.  As with all human endeavors, science is flawed and imperfect.  Certainly, as a religious person, I agree with the criticism leveled by many against our culture that it is too scientistic–that is, that it considers as true or relevant or important only that which can be demonstrated by the scientific method.  As I hope (but don’t assume) is obvious, such a view is a non-starter.  Nevertheless, the scientific method is one of the most powerful methods the human race has ever developed in its quest for truth; and to reject it tout court is as ridiculous and unwarranted as assuming that one is a brain in a vat!

So in summation:

  1. No matter what your station in life, or what your profession or ability, learn at least a little bit of science.
  2. If you write science fiction literature in any way, shape, or form, even if it’s schlocky romance, learn even more science, and do your homework!  Believe me on this–the fans will know!
  3. In sf, an error here or there, or some well-developed imaginary science, is OK.  Stupid, elementary errors (at least for those of us writing in the 21st Century) are not.

So, in conclusion–if you want to write fantastic literature, but don’t like or understand science, and aren’t motivated to learn some, then write fantasy!  ‘Nuff said!

Part of the series “Reviews, Views, and Culture, Pop and Otherwise“.

Also part of the series “Science and Technology“.




Posted on 06/07/2018, in science, science fiction, space and tagged , , , , , , , , , , , , , , , . Bookmark the permalink. 4 Comments.

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