In a place without time
there is no story to tell,
all persons, places,
firm and free,
transfixed and stubborn
in the silent still.
That which would move
does not flinch a fiber,
those who would try
cannot move a muscle,
particles that spin and bounce
do neither in their torpor,
rusted through the core,
the rust can creep no more.
Motion needs time
to step through its dance.
Time needs motion
until the clock stops.
Think of one,
you’ve set them both
a distant goal.
This thing popped into being while I was reading the sixth “brief lesson” in Carlo Rovelli’s Seven Brief Lessons on Physics. That sixth lesson is titled “Probability, Time, and the Heat of Black Holes.” The tiny thing I’ve presented above addresses the unimaginable and, thus, is a paradox.
Which is briefer – Planck time divided by infinity or its inverse?
As I write this soon-to-be-anachronistic piece, it is already the “new year” in various places around the world. For instance, in Hong Kong it is 12:04 A.M on Sunday while it is only 11:04 AM Saturday here (east coast U.S. time).
The truth is far more complicated and far more interesting to consider.
First of all, there is the notion of sidereal time—time relative to a fixed star‘s position. It is used by astronomers, who cannot rely on our own sun’s position as our positional relationship to it is not fixed. As a matter of fact, starting in the 19th century it was noticed that the “fixed stars” are not fixed either. They are just distant enough that they are far more fixed than our local star seems to be. All sorts of calculations can be sorted out to use a non-fixed distant star or bright astronomical object as relatively fixed, but I neither understand these calculations nor would you (I suspect) find them particularly interesting. So, the bottom line is sidereal time is in constant change here on earth. If I am standing shoulder-to-shoulder with you, we are in different sidereal times. Sidereal time has no respect for time zones. Time zones are useful in that it would be a nightmare to discuss the time it actually is if we were not to bunch time together in chunks like we do.
Second, time is not really measured in chunks like hours, minutes, and seconds. One really has to consider the fastest event in the universe to consider time more accurately, if not more usefully. The shortest time is the calculated Planck time, which is 5.39×10-44 seconds (in other words there are 1.9×1043 tP in one second—roughly 2 followed by 43 “zeros”—an incomprehensibly large number of events on the “standard human time scale (SHTS).” It is the amount of time it takes for a photon in a vacuum to pass through a Planck length, which is also very brief, distance-wise.
The thing about Planck time is that it is a time derived from a physical standard calculated by Planck, so although useful for physicists, there’s something a little incestuous about the whole business. Various elements have layers of electrons probabilistically scooting around their nuclei at mind-bending rates of speed, while also changing their quantum energy levels from their lowest energy levels (aka ground states) to a variety of higher energy levels. These electronic transitions have been studied and are variously known to behave themselves in very dutiful ways. As they are in constant motion between energy levels and motion takes time, even on the atomic scale, the distances and times are very tiny. Cesium atoms, for instance, experiences 9,192,631,770(±some variation) transitions between energy levels per second. The atomic clocks based on this cesium transition are so accurate that they are calculated to lose only 1 second in 100,000,000 years (one hundred million years!) or so.
Part of the work that scientists do is involved in never being satisfied with a “good enough” answer; they are always looking for increased, accuracy, precision, measurement stability, always looking for a more refined “truth” than that which has been understood before. If you were a professional runner, for instance, and you just achieved a personal best, you would not go home, pop open a bucket of ice cream and settle in for the rest of your life. The next time you ran, you would try to better your personal best. Same with scientists, except the standards are set by nature and the tools we have to achieve better outcomes are constantly in the process of improvement.
Cesium has been the standard for measuring seconds for some years now but has just been displaced from its throne by an ytterbium-based atomic clock that “ticks” 518,000,000,000,000 (518 trillion) atomic events per human second. This allows a crazy level of stability that makes the mere 9 billion mark previously set by the cesium atomic clocks seem like sundials. The following video is a National Institute of Standards and Technology scientist discussing this improvement on video, along with explanatory text.
If all of this weren’t disconcerting enough for you, these atomic clock scientists have found that time varies with altitude as well. In experiments using aluminum atom atomic clocks, they have been able to demonstrate that these variations in time have an effect with each foot of elevation, meaning that our feet are in a different time zone that our heads (does this explain clumsiness? it’s at least a better excuse than “I can’t walk and chew gum at the same time!”). Over a 79-year lifespan, the difference would only amount to about 90 billionths of a second, but it is there all the same.
The whole point is that while we usher in the new year, we might give pause to remember that what we are celebrating is a not entirely accurate astronomical event. The earth has orbited around our sun for the past 365 days and will start that process again. In the meantime, sidereal time and atomic time—and Planck time for that matter—are all moving at rates that we can’t even comprehend unless we’re practicing the science of measuring—and improving—on atomic clocks and the electronic quantum transitions that are involved. From a practical standpoint, the next time you look at a second hand on a clock or watch a minute pass, consider the atom and all the changes it has gone through in that time. Consider that, as the earth rotates and precesses on its axis each day, we are each in our very own time zone. In fact, various parts of our bodies are in various time zones, particularly if you’re measuring our relatively enormous selves in Planck lengths.
So, Happy New Year! We have orbited our sun at the rate of 67,000 miles per hour—or if that seems too fast to you, let’s just say 19 miles per second—over the past roughly 365.256 days and yet, knowing these underlying facts, we will all count down to midnight in the enormously large seconds increments “ten-nine-eight-seven-six-five-four-three-two-one-happy-new-year!” and 6.144 hours later, the new orbit of the earth around the sun will start.
I am a trusting person. The good news is that there is much to trust in our daily lives.
I trust that sometimes around the time I wake the sun will have risen—or will soon rise—in the east. I trust that the weather will vary during the day and although I may be oblivious to it the weather will vary during the night as well. I trust that a year will pass in a series of days and those days will pass in a series of hours, minutes, and seconds. I trust that time will not reverse in this process and I will become older, not younger. I trust that seasons will bring changes to how the world appears, at least in my part of a large planet full of differences.
I trust that I survive each day because the invisible stuff that surrounds me contains oxygen and that some of this oxygen ends up bound to my hemoglobin and myoglobin proteins and will end up servicing core and peripheral functions of my body. I have never seen an oxygen or any other gas molecule per se but I have seen hemoglobin data modeled out using physical probes and understand that hemoglobin is transported in red blood cells (aka erythrocytes), which I have seen through photomicrography recorded by others. I trust that when I drink and eat a whole series of enzymatic processes will turn the foods and beverages into energy, some used immediately, some stored for a nomadic existence that has long ceased to be relevant for many. Some of what was once delicious will cause me to get up when I don’t want to get up and do things which are among the least dignified activities any of us will perform on a regular basis. On the other hand, we have no choice, so why complain?
I trust that most of the people I see on any given day will behave themselves within acceptable parameters… except when some of them are driving, at which time this subset will take actions that they are told by the motor vehicle and people licensing authority are not acceptable… yet they do these things anyway. You’ve probably seen them do these things wherever you are and you may see them do worse things that I shudder to even imagine. I trust that, while most of the people I see are behaving appropriately somewhere, someone is not doing all that well in this regard. Oh, and that the “someone” to whom I refer is accompanied by others who are also not behaving. These behaviors take place in all towns, cities, and countries and by all people, regardless of wealth (presence or absence thereof), country of origin, employment status, religion, ethnicity, gender. Both well-intentioned behavior and its opposite are aspects of human existence. While other creatures on our planet do violence to each other on occasion, we are the only species that participates in violence and its correlates so pervasively and still find a way to live with each other (for the most part).
Sometimes, I look up a word before starting in on it. It seems to have roots back to the early state of languages called Proto-Indo-European (aka PIE (not π)). For a phenomenal map of what languages are derived from which others, please go to the site provided under the following version:
I’m just going to drag something over from the Wiktionary page to get into how trust is linked to some very fundamental human values:
“Protection,” “confidence,” “help,” “be firm, hard, solid.” This is what we associate with the meaning, although we don’t necessarily think through that the word is from Old Norse and Middle English, or that it is related of “confidence” and thus to the Latin fides, which meant trust, faith, and belief and is responsible for fidelity and bona fides. Interestingly, the Wiktionary page also points the reader to derivation of the words “true” and “tree.” “True” seems explicitly related; one wonders if the concept of trust and truth both came from an appreciation for the confidence, help, protection, firm, hard, solid virtues of houses built from the readily available (far more then than now) tree.
It is also interesting that the ideas of faith and belief are concepts that grew simultaneously with the concept of trust. I wonder, though, whether these meant something far more alike to trust when they were conceived than they do now.
While I trust in all of the experiential, reliable events that I cited in the first couple of paragraphs (with some elaboration from the sciences, admittedly), I do not need to have faith in them or believe them to be true. They simply are trustworthy and true. When I listen to politicians tell us to have faith in them or believe in them, I start wondering where I left my wallet and whether my bank has secured the accounts against hacking. I understand why they want my belief but I will give it when their actions measure up to their words. I will believe them when I trust them but I will not trust them until I believe that they have achieved what they promised.
It is also interesting that the word “truss” meaning a structure that supports or stiffens a building is phonetically related to “trust,” as that is the function it is intended to convey to the building. It makes the building, no longer made of trees, one that you can have confidence in entering. Your faith will not be tested, your belief shattered. Well, unless the weather gets really bad. And I trust that it will on some days.
The 1,000 “like” road marker disappearing in the rear view mirror…
The WP auto-post function just told me that I have accumulated 1,000 “likes,” which are all because the imaginary “you” have been appreciating what I’ve been pouring forth since June 22nd. It hasn’t been four months yet and I have so many “likes!” Who knew?!?
I’ve logged 87 posts (one was a repeat, so doesn’t really count and one was a reblog in respect for a new WordPress-induced friend) in 111 days, meaning that I’ve hit about 78% of the days between start and present. Not bad. Could be better. Let’s see if I can pick up the slack.
This border is gradual and becomes more real as any of us ascend into our atmosphere. While the troposphere contains ~80% of our air (which is a mix of gases as faithful readers already know), the stratosphere holds a mere 19% or so. As we leave sea level and go up mountains, there is less air, therefore less pressure exerted by the air upon us. By the time we get around to climbing Mount Everest, there is so little oxygen left in the lower pressures of atmosphere experienced at that altitude that climbers must bring their own. On the other hand, it gets much colder as we climb so there are two good reasons to remain close to flat land: (1) decreasing air and (2) decreasing temperature. This is all graphed out in the Pressure scale helpfully included in the following:
As a little imagination game, imagine that your roommate and/or spouse (depending on years of commitment) has just cracked open a rotten egg in your kitchen. The spreading smell represents earth’s atmosphere and you want to get as far away from that particular atmosphere as possible. The farther you remove yourself, the less the smell and (for purposes of this analogy only) the less atmosphere there is. Although you can’t really smell air, you can experience its absence quite profoundly (caution: side-effects may include a light-headed feeling, confusion, dizziness, shortness of breath, and death).
2. The air we can breathe and the earth we cannot.
While sea level and much mountain air is pleasant to breathe, inhaling earth of any kind results in clogged oral and nasal passages. If attempts to breathe earth are continued, bronchi and alveoli may become non-functional leading to a lack of air and at least some of the side-effects mentioned above. Do not breathe earth. While it is good for plants to stick their snouts deep within a nice chunk of earth, particularly when it is enriched with supplements, we must insist that you do not attempt to replicate their behavior. While a diagram of the earth coming into contact with air is not very exciting, there are many important processes that happen between the various solid surfaces, natural and human-made, and the air. Here’s a nice diagram of how the stuff we put into the atmosphere comes back for visits:
3. The air we can breathe and the water we cannot.
You would think this boundary is as boring as the one between the air and the earth and you would be incorrect. The atmosphere and bodies of water of significant size have a very dynamic interaction. This incredible time-lapse map of global oceanic currents (courtesy the nice people at NASA) shows their beauty, dynamism, local and transglobal effects, their overall complexity:
But these are only the surface manifestations of phenomena that reach into the clouds and oceanic depths as well. The following video, produced by NASA using data from a number of their satellites and narrated by Liam Neeson, starts with an explanation of how the earth is protected and affected from the sun’s energy output by the magnetosphere.
Chances are that you may have missed the thermodynamic heat pump that powers circulation in our oceans. It is called thermohaline (“temperature-salt”) circulation or conveyor belt. As surface water is warmed by the sun at the equator it is swept north and south toward the icy poles. There it is cooled. As cold salt water is denser than the warm variety, it sinks as it approaches the poles and is swept along the ocean’s floor back towards the equator and elsewhere around the globe. Given the complexity of the currents and circulation, it is thought that it may take up to 1,000 years for one unit of water (let’s say a cubic kilometer) to circulate back to its point of origin.
4. The water we cannot breathe and the earth we cannot breathe.
This is not our realm. We belong walking along the surface of the earth, breathing the atmosphere and drinking the purer forms of water. We must take our atmosphere with us when we move into the water or earth.
Our takeaway lesson? While you can only breathe the air portions of this very real barrier between the air and water or between earth and water, the effects that air, earth, and water have on each other is astonishingly complex and persistently in motion. Without this perpetual motion going on between the three of them, there would be no weather and no recycling of the gaseous and aqueous realms so necessary for us to live.
The fifth border is imaginary—human-made—compared to the four above. Here is one way of picturing it:
All these countries, all these governments, all these people divided up by imaginary lines cut into the earth and bleeding the blood of its citizens. Why do some people want to go elsewhere? Why are “violations” of these imaginary lines fraught with so much emotion, so much passion, so much need?
Here’s another way of looking at these imaginary lines:
At one end of the spectrum of net national incomes, we have Malawi, a country that is full of nice people who through no fault of their own barely scrape through a year on virtually nothing… and that’s the AVERAGE income! At the other end, we have Qatar, Monaco, the Scandinavian countries, some others (the names aren’t as important as the concept here). The average net national income across all countries is around $45,000/year.
The reasons the imaginary boundaries are important is that people who have governments that don’t work in the interests of the families who live there want to leave and find opportunity elsewhere, which makes their destinations nervous—probably for some good reasons. The destinations of choice all seem better from a distance as the people who want to leave their countries are doing fairly poorly. As more people arrive at their destinations, it is likely that the quality of life in that country will be overwhelmed by newly arrived citizens—and the existing citizens who were already doing poorly and will see a deterioration in their quality of life. On the other hand, the people who leave their countries of origin leave behind many family members, the culture and geography they know and appreciate, their way of doing things, which may have been that way for millennia and are much loved.
The solutions are not easy. I propose the following:
The countries that are not doing well by their citizens must determine why there are disparities in quality of life and correct them so that anyone who wishes can make a one-to-one comparison between their lives at home and their imagined lives elsewhere.
This will often mean that the people who are doing the best in those countries must find ways to share their success with more of their citizens. As it is often the case that wealth from natural resources, agriculture, etc., are harvested by the poor and enjoyed by those who are already comfortable, that seems to be an appropriate basis for sharing. Do corporations and governments own the natural resources of any particular country? I would think all citizens of the planet “own” them equally and that the corporations and governments are only there to ensure equitable distribution of them and any profits that arise from manufacturing.
The countries that are doing well must find ways to channel resources to the countries who are not. These resources must find their ways first to the people who need them the most. Once inequities in education, nutrition, safety, health, domicile and baseline income are addressed, more generalized issues (e.g. governmental corruption) must be addressed as well.
This kind of change is needed. The earth—on its own—figures it all out in spite of the various environmental disasters we keep visiting upon it. Now, we the people must figure out how to stop killing each other—or passively allowing each other to be killed—and work through the inequities that we allow to exist between us.
It is easy to come up with arguments that refute these positions: political, religious, racial, gender, class, family history, income, etc. It is better to stop arguing and get to solutions. We are all one thing and that thing is the human species. Let’s solve our problems so we can all stop with the stupidity.
Confabler nominated me for a Sunshine Blogger Award!
My distant, yet close friend Confabler has nominated me for the Shiny Shiny Sunshine Award. I love her imagination and sense of whimsy; she lets her muse du jour lead and she follows. There’s a wonderful freedom to that which is (1) difficult to allow in the rational process of “writing” and (2) enjoyable to find.
1. If you were to choose an insect that would take over the world after human extinction, who would that be?
It sort of depends on our route to extinction. If it involved an epidemic, the population of flies might see a giant uptick. This would be a good one:
If it is a slow process, then I nominate the Japanese Rhinoceros beetle because it would be awesome if creatures with such improbably fashioned protuberances were to be the alpha species (Megasoma and Titan beetles would be acceptable alternatives):
If our extinction took all other terrestrial life along for the ride, I would like to see this enormous isopod (a relative of our terrestrial roly-polies) rule the seas (note inclusion of actual human hands for sense of scale):
2. How old were you when you first read Harry Potter? And your favorite author of course?
I was pretty old when I read my only Harry Potter book (the first one). I didn’t enjoy it enough to complete the series, although I’ve seen all the films and enjoyed them well enough. In the period I read that first one, I was typically reading a lot of history and didn’t find that it was a good use of my time. When I was really young, I read the Classics Illustrated versions of novels, which were quite good at introducing a curious young mind to the wonders of literature without having to do the work (sort of illustrated CliffsNotes (I didn’t use these in school though), if you will). When I was a little older, I read Robert E. Howard, Sax Rohmer, John Carter of Mars, H. Rider Haggard, Stanley Weinbaum, George McDonald fantasies, etc.
My favorite author is Gabriel Garcia Marquez for One Hundred Years of Solitude and Love in the Time of Cholera. His writing is so rich, amusing, full of simple wisdom and abundant humanity it is hard to believe he was just a human being writing about the lives he saw playing out around him. I literally would read some passages and have to put the book down as if I had just sipped the richest chocolate elixir in the world and needed to savor it until I sipped again. His Spanish-to-English translators did a good job in getting it right; Gregory Rabassa (OHYoS translator) was even praised by Garcia Marques himself!
3. If you were invisible what is the craziest thing that you would do?
Here’s an odd one: Go and hang around bigots, transcribe their conversations, and publish them for the world to see how terrible people speak when they think no one is listening (but, oh yeah, we have the internet so this already happens). If I could walk through things, which seems fair since I’m invisible, I would go around seeing what it felt like to do that—see if there were different textures to different things on the inside than on their surface.
4.what food makes you feel like a hungry hyena?
This has changed so much over time! These days, I don’t get this kind of urge anymore. In my early adult (late teen?) years… ICE CREAM!!!!
5. A song that makes you dream?
Gymnopedie #1 by Erik Satie
6. Have you ever planted a tree?
Yes. Unasked but answered: quite a few!
7. Choose your man: superman/ Spiderman/ iron man and if he was your best friend one thing that you would make him do?
Can I choose Supergirl? If I can, I would have her take me around to various places in the world, build shelters so I could stay there and visit free, then whisk me off to the next place on “our” list (she would be enjoying the sight-seeing with me, of course! What kind of boor do you think I am?!?!).
8.How much time do you spend in front of the mirror everyday?
As little as possible, which involves shaving and brushing my teeth. I find that shaving my teeth first helps with the brushing.
9.why you started blogging and tell us about the post enjoyed the most making.
I was having a bunch of conversations with people who did not seem to understand the wonderful humility of learning and doing science and wanted to see how well I could write about how science is a discipline that can assist us all in not leaning out too far over our skis (getting ahead of ourselves and pretending we know stuff we don’t). Blogging has become so much more than that since my first post on June 22, 2016, and I have had so much fun writing fiction and revisiting some poetry I wrote several decades ago (and finding them easier to “fix” than I remembered).
I’m not sure which of my posts I enjoyed the most. They’re all my children so I like them all? I probably like the odd bits of fiction that I had no idea were inside me when I woke up and then found them on the page looking up at me. I like The Big Day of these. Of the science posts, I like The Mess: Parts 1 & 2 and the Appendix 1 items best (maybe). Of the historical pieces, I like Risk Management. Of the life pieces, I like Building Blocks the best. Anyone who reads this is encouraged to make up their own mind; I am hopelessly biased.
10. Which social media platform are you addicted to (including WordPress)?
I don’t do much social media except WordPress. I don’t like Facebook at all and deleted my account. WordPress is addicting but in a very healthy way! You get to create something and share it with new friends from all over the world. That’s a great addiction have.
Now the rules:
1.thank the person that nominated you.
Thank you, Confabler. You are a true virtual friend, and I don’t mean that in any Pokemon way either!
2. Answer the questions from your nominator.
3. Nominate fellow bloggers you follow.
Hereinafter lie the following nominees in no particular order (order, of course, being an illusion):
Confabler – it would be completely wrong not to boomerang this thing back at her; how could I like what she writes and like that she nominated me but ignore why we share interests at all?
November_child – in her poetry, every word is judiciously considered for its various meanings and the images they stir and she makes great short stories that are deep and playful and serious all at the same time
anonymouslyautistic – for doing an AMAZING job of writing about this misunderstood spectrum of living – and for inviting others who share her interest to contribute
English Lit Geek – because she searches the web and her library for poems that communicate her inner soul to us all out here in the ‘sphere and I appreciate this!
Wiser Daily – because this guy writes REALLY well about every single subject he wraps his mind around, because he is not a scientist but writes extremely clearly about science, because he is just a damned good writer!
Breathmath – because they are doing an astonishingly serious job of trying to get the world to see the beauty in mathematics
Sheryl – because she’s written a book, is working on others, has great tips for doing the same, and kindly visits my offerings fairly often
The Nexus – because he writes REALLY well about physics and does a great job of doing what I set out to do, whether I’m doing it on any given day or not
The Biology Yak – because she is passionate about biology and shares her passion in every word on every topic she chooses
afternoonifiedlady – even though I have no idea what it is to be an afternoonifiedlady, I love her rants about living with and without her ex and trying to wrestle with notions of romance – she is very witty and amusingly pissed off!
There are loads of naturally occurring and synthetically created organic molecules (usually compounds composed of carbon and hydrogen but often containing other elements as well). As chemists got busy discovering these substances, they also started coming up with ways to name them in increasingly systematic ways. Very early in an organic chemistry course (or very late in a general chemistry course), students learn that organic chemistry is as much a language course as a science course. Bright students with good language skills figure this out and apply the grammar and syntax accordingly; bright math students sometimes wonder what the heck happened? The way chemical compounds are named is called nomenclature, which means (oddly enough) “name calling” from Latin roots. Before the end of any organic course, some portion of the class usually gets quite busy calling names, although not those of the organic compounds they’ve come to despise (silly students! Succumb! Breathe in that fresh and unusual knowledge!). The professors bear the brunt of the name calling, although teaching assistants and anyone else nearby will do nicely. I probably fell in love with organic chemistry when I realized the nomenclature was systematic and could be applied logically rather than learned by rote memorization. And then there is the rich, rich symbolic language that goes along with the words! So spare and simple! So full of endless possibilities!
Anyway, among the structural idiosyncracies posed by increasingly insightful physical and chemical tests chemists developed was that some organic compounds contained single carbon-to-carbon bonds, some contained shorter double carbon-to-carbon bonds, and some others contained triple bonds between carbons, which were shorter than either of the other two types. Typically, carbon requires four bonds to other elements (carbon, hydrogen, oxygen, nitrogen, sulfur, etc.). When there was a double bond between carbons, the two carbons with the double bond between them only needed another two bonds—a total of three bonds instead of four. When the two carbons had a double bond, the other elements on either side of the double bond were sort of locked in place by the relative rigidity of that double bond (triple bonds are even more rigid). If there were only two carbons in the molecule and each of the carbons were bonded to two hydrogens as well as each other, there was no problem in naming that little nugget. It was called “ethene.” Just to give you something to relate this to, if you take off one of those hydrogen “H” atoms and put on an hydroxyl “OH” bit, this little guy magically becomes ethanol, fuel of dreams, liver-pillager, starter of fights and trips to the ER.
When the chemical moieties are something other than hydrogens, the naming game gets a touch more difficult. For instance, if we are presented with a four-carbon compound that has a double bond between the second and third carbons, it would generally go by the name “but-2-ene” or the arguably simpler 2-butene (there is a global chemistry naming organization called the International Union for Pure and Applied Chemistry (IUPAC) that gets together and sorts this stuff out; but-2-ene is their preference and they have a really colorful website, so let’s go with their approach, which I also adopted with “ethene,” although “ethanol” is the IUPAC name for ethyl alcohol). Here’s but-2-ene:
Oops! But that’s TWO molecules. Yes it is. The thing with that rigid double bond is that once a molecule has one, and there are a sufficient number of carbons or other sufficiently complicated moieties hanging off one end of the double bond or the other, there are two possibilities. The top symbol represents the cis- form, by which it is meant that the two methyl groups (each CH3– group is known as a “methyl” group) are on the same “side” of the double bond as each other (by the way, the double bond makes all of four of the carbons lie in the same plane as each other, so it is essentially a “flat” molecule, although the hydrogens on the methyl groups sort of spoil that by spreading out in their typical tetrahedral patterns). The bottom symbol represents the trans– form, by which it is meant that the two methyl groups are on different “sides” of the double bond. They are two different molecules with different physical properties: cis-but-2-ene boils at 3.7°C, while trans-but-2-ene boils at 1°C (they melt at -138.9°C and -105°C, respectively—a pretty huge difference in melting points for two molecules with exactly the same chemical formula (C4H8)).
For a more three-dimensional look at the difference between cis– and trans-but-2-ene, take a look at the following pages, which allow you to rotate molecular models of these distinct chemicals and shows their “flatness” better than the structures shown above:
That naming convention worked just fine… until more complicated substituents were inevitably discovered mucking up the nice cis- and trans- simplicity. As an example, let’s look at 1-bromo-2-chloro-2-fluoro-1-iodoethene:
The way this new rule works is that we must take into account the atomic masses of the ethene substituents (ethene (we’ve met before) being that two-carbon-double-bonded bit in the middle of all these halogens (e.g. F, Cl, Br, and I)). Let’s rank these halogens in decreasing atomic mass: iodine (~127 daltons or amu), bromine (~80 amu), chlorine (~35.5 amu), and fluorine (19 amu); (in science, the tilde (~) is used to mean “approximately). The rule is this: if the moieties with the highest atomic masses are on the same side (not the same end, mind you!) of the double bond, then they are “together” or “zusammen,” the German word for “together.” If the highest amu moieties are on different sides of the double bond, they are opposite or “entgegen.” It would be sort of laborious and annoying to spell out “zusammen” and “entgegen” prefixed to every molecule for which this naming convention applies, so instead the letters “Z” and “E” are used. This means compound 9 (above) is named (E)-1-bromo-2-chloro-2-fluoro-1-iodoethene, while compound 10 is named (Z)-1-bromo-2-chloro-2-fluoro-1-iodoethene.
If you’d like to know who to thank for this naming convention, make sure you give credit to R.S. Cahn, C.K. Ingold, and V. Prelog, without whom the Cahn-Ingold-Prelog Rule would not exist. It can be applied in an equivalent manner to any compound in which conformational isomers around a double bond raises some ambiguity about nomenclature. Here is one last picture that shows you how it might apply to other substituents around a double bond:
And, by the way, the Germans (responsible for the words zusammen and entgegen) call the letter “Z” “tzett,” which is close to how those English-speakers on the other side of the pond (i.e. the British, but also Australians, Kiwis, and for that matter, Canadians, who are just across the Great Lake ponds) say it – “Zed.”
If you want to know a bit more, listen to the dulcet tones of Sal Khan as he goes through a few more examples.
Special thanks to my German tutor November Child, who writes excellent poetry and had no idea I was writing about this today.