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Hoo-ray! Earliest sunset today.

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Hoo-ray! Earliest sunset today.

Old 12-09-20, 10:33 AM
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conspiratemus1
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Hoo-ray! Earliest sunset today.

Yes, from mow until the summer solstice, the sun will be up in the evening a little longer every day. The shortest day is not until 21 Dec. but owing to the elliptical nature of the earth’s orbit, the apparent movement of the sun gets enough out of kilter with the clocks this time of year that the clock timing of sunrise, noon, and sunset gets shifted. By Christmas, you will notice the afternoon sun definitely lasting longer.

The downside for those who have to get up early is that latest sunrise doesn’t occur until about 10 Jan. So those post-New Year commutes make for awfully dark mornings.

This “time-shifting” has nothing to do with the seasons per se. It’s just the orientation of the ellipse happens to make the effect strongest in that portion of the orbit that we call December. “The equation of time.”​​​​​​
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Old 12-09-20, 10:39 AM
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This should not be allowed.
they need to pass a law to protect our daylight. 😉
oh yea, Florida already tried that.
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Old 12-09-20, 10:55 AM
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Originally Posted by conspiratemus1 View Post
Yes, from mow until the summer solstice, the sun will be up in the evening a little longer every day. The shortest day is not until 21 Dec. but owing to the elliptical nature of the earth’s orbit, the apparent movement of the sun gets enough out of kilter with the clocks this time of year that the clock timing of sunrise, noon, and sunset gets shifted. By Christmas, you will notice the afternoon sun definitely lasting longer.

The downside for those who have to get up early is that latest sunrise doesn’t occur until about 10 Jan. So those post-New Year commutes make for awfully dark mornings.

This “time-shifting” has nothing to do with the seasons per se. It’s just the orientation of the ellipse happens to make the effect strongest in that portion of the orbit that we call December. “The equation of time.”​​​​​​
I thought I was the only one who knew or cared about this. I always get a small glimmer of hope when we have our earliest sunset, which now happens at about 4:08 in my neck of the woods.
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Old 12-09-20, 11:04 AM
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Originally Posted by conspiratemus1 View Post
Yes, from mow until the summer solstice, the sun will be up in the evening a little longer every day. The shortest day is not until 21 Dec. but owing to the elliptical nature of the earth’s orbit, the apparent movement of the sun gets enough out of kilter with the clocks this time of year that the clock timing of sunrise, noon, and sunset gets shifted. By Christmas, you will notice the afternoon sun definitely lasting longer.

The downside for those who have to get up early is that latest sunrise doesn’t occur until about 10 Jan. So those post-New Year commutes make for awfully dark mornings.

This “time-shifting” has nothing to do with the seasons per se. It’s just the orientation of the ellipse happens to make the effect strongest in that portion of the orbit that we call December. “The equation of time.”​​​​​​

I just read this and processed barely any of it. Pretty sure I am intrigued enough to do a deep dive on this after work though. The shortest day isnt on the date that is always known as the shortest day?!?! School failed me again!!!!
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Old 12-09-20, 11:47 AM
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I need to shift my days around. I get the urge to go outside right before sunset. I should go out and ride at sunrise or so.
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Old 12-09-20, 12:27 PM
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Originally Posted by conspiratemus1 View Post
Yes, from mow until the summer solstice, the sun will be up in the evening a little longer every day. The shortest day is not until 21 Dec. but owing to the elliptical nature of the earth’s orbit, the apparent movement of the sun gets enough out of kilter with the clocks this time of year that the clock timing of sunrise, noon, and sunset gets shifted. By Christmas, you will notice the afternoon sun definitely lasting longer.

The downside for those who have to get up early is that latest sunrise doesn’t occur until about 10 Jan. So those post-New Year commutes make for awfully dark mornings.

This “time-shifting” has nothing to do with the seasons per se. It’s just the orientation of the ellipse happens to make the effect strongest in that portion of the orbit that we call December. “The equation of time.”​​​​​​
Is it just us bike commuters that pay this sort of attention to the times of the sunrise and sunset?
I had to ride east in the morning and always tried to adjust my start time to reduce the chance of riding into the sunrise.
The ride home was after peak traffic, so I got to just enjoy the sunsets. Not a bad way to unwind after a day of work!

Back in the early days of the internet, I downloaded a table of sunrises and sunsets from the Naval Observatory's website. I put it into a spreadsheet and plotted it out. That was when it became very obvious that the latest sunrise did not occur at the same time as the earliest sunset. It makes sense that the elliptical orbit accounts for the non-sinusoidal shape of the sunrise/sunset curves, but it's still not clear how that accounts for the different days for latest sunrise and earliest sunset. Maybe there is a video somewhere that explains this in detail??

Steve in Peoria
(I also have a Casio watch that calculates sunrise and sunset time! )
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Old 12-09-20, 12:39 PM
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Back when I was employed, commuting to and from work was my favorite part(s) of the day.
All four seasons, too. Never bothered me. Always enjoyed the ride.
Been keeping up the routine during furlough. Actually tripled my time in the saddle.
But now that I got nowhere to get to and nothing to do when I get there, I notice the cold and the dark a LOT more lol.
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Old 12-09-20, 12:51 PM
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Originally Posted by mstateglfr View Post
I just read this and processed barely any of it. Pretty sure I am intrigued enough to do a deep dive on this after work though. The shortest day isnt on the date that is always known as the shortest day?!?! School failed me again!!!!
Look up analemma.on Wikipedia -- it's that figure eight thingie some globes have over the vast expanse of the south Pacific

I am at latitude 33N -- we hit our earliest sunset on Dec 2 and 3.
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Old 12-09-20, 04:29 PM
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I think you have a couple of days to go if you're still in Canada, conspiratemus1

Here in the DFW, we had our earliest sunset on Dec. 3.

https://earthsky.org/earth/winter-so...d-late-sunrise
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Old 12-09-20, 05:00 PM
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Originally Posted by steelbikeguy View Post
Is it just us bike commuters that pay this sort of attention to the times of the sunrise and sunset?
I had to ride east in the morning and always tried to adjust my start time to reduce the chance of riding into the sunrise.
The ride home was after peak traffic, so I got to just enjoy the sunsets. Not a bad way to unwind after a day of work!

Back in the early days of the internet, I downloaded a table of sunrises and sunsets from the Naval Observatory's website. I put it into a spreadsheet and plotted it out. That was when it became very obvious that the latest sunrise did not occur at the same time as the earliest sunset. It makes sense that the elliptical orbit accounts for the non-sinusoidal shape of the sunrise/sunset curves, but it's still not clear how that accounts for the different days for latest sunrise and earliest sunset. Maybe there is a video somewhere that explains this in detail??

Steve in Peoria
(I also have a Casio watch that calculates sunrise and sunset time! )
Yes, the Naval Observatory table is what I used also. Kept it pinned up to my bulletin board at work to estimate how dark it would be when I got off the train and unlocked my bike. Night-time lights are different from day-time, especially since I had a "dark zone" of 2 km where there were no streetlights and no traffic. Lovely under a full moon with snow on the ground and lights off. (Don't tell my wife...)

As per John E, the analemma explains it, and check out the really cool composite photos where one of the exposures (the first, presumably) captures a solar eclipse! The two lobes of the figure 8 are not symmetric, owing to the eccentricity of the earth's orbit.
Originally Posted by steelbikeguy View Post
. . .but it's still not clear how that accounts for the different days for latest sunrise and earliest sunset. Maybe there is a video somewhere that explains this in detail??. . .
Fundamentally, the sun is a good calendar (once you figure out Leap Year) but not a very good clock because it runs fast or slow, depending on time of year. The effect is an artefact of imposing an invariant clock time on a wandering timepiece.
The key to understanding is recognizing that any body moving in an elliptical orbit speeds up and slows down during its orbital journey (conservation of angular momentum). When it is close to the centre of mass located at one focus of the ellipse (which can be taken to be the centre of the sun even though it's not quite), it moves faster. This is what the earth is doing right now, 4 January being perihelion. As it swings around and gets farther away, it slows down until 4 July, then it starts accelerating again. These dates are pure coincidence (other than being six months apart by necessity) and have no relation to the seasons. Once you recall that the earth's orbital velocity it not constant but varies predictably through the year, you can see how solar noon will not occur at the same clock time every day and not all days are 24 hours long. Rather, the error will accumulate progressively, then start correcting so that the solar day is, on average over the course of the year, its familiar 24 hours. Since sunrise and sunset are keyed to the noon mid-point of the sun's apparent journey across the sky, these times will vary as well when measured by an invariant clock. If you have a sundial, you have to add or substract minutes each day to make it agree with a mechanical clock. If you didn't correct it for "elliptical variation", you would see earliest sunset and latest sunrise and the lowest noon sun all on 21 December, equidistant from solar noon. Someone a few minutes of longitude away, also with an uncorrected sundial, would see the same thing, but the two of you would see them at slightly different times. And both of you would be late or early for your appointments which are regulated by clock time. By coincidence, the maximal variation from clock time occurs in the dark months of November and December when we are most attuned to them.

I think this is important because:
Everyone 'knows" that Copernicus and Gallileo proved the earth revolves around the sun. But they didn't, really. The honour belong to Johannes Kepler and Sir Isaac Newton.
The recognition that the planets (and the satellites of planets) move in ellipses (although some, like Venus. are very close to perfect circles) was a fundamental achievement in working out planetary mechanics. It drove the final nail into the coffin of the dogma of a stationary Earth at the centre of the universe. Copernicus had the heretically counterintuitive idea that the planets revolved around the sun in circular orbits, true. It didn't predict the observed apparent movements of the heavens any better than the astrologers could do using the Ptolemaic view of complex circles within circles of an unseen celestial machine cranked by who-knows-what?. Great simplification made this conceptual leap attractive but really it was just a shift in mathematical frame of reference. Nothing about the earth-centered view was disproven by Copernicus's formulation. Even Gallileo's observation that the four moons of Jupiter* he could see with his telescope were clearly revolving around Jupiter and not around the earth could be explained away as a special case of the Devil trying to tempt us, with his evil instruments and fake news, to test our faith. Indeed, the very careful later telescopic observations by Tycho Brahe, an earth-centrist, showed discrepancies in the position of planets predicted by the heliocentric circle model, a "Gotcha!" which called the very idea into question and seemed to vindicate the Church. Johannes Kepler's incalculable gift to science was to recognize that in those discrepancies lay the foundation of a new theory: when he fitted the planets to elliptical orbits, the discrepancies were resolved (at the limits available in the day.). Then it was for Newton to develop the theory of gravitation (aided by calculus) to propose a mechanism for what made it all work....which scientists are still working on to this day.

I just think it's gratifying that you can use simple observations (aided by timepieces not available until recently in human development, say, mid-18th Century) to take a step toward understanding the true nature of the heavens. (To make an analemma you have to observe the sun at exactly the same clock time every day, a meaningless concept before the naval chronometer.) I'm not embarrassed to say I am profoundly moved by this.
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* If you've never done so, I urge you to go out with a pair of ordinary binoculars some clear night that Jupiter is visible and look for the Galilean satellites. You can see them from a city street, you don't need a super dark sky, although no moon makes it easier. Steady the binoculars against a telephone pole or the roof of a car. One or two moons are easy to see and you can verify that you don't always see all of them -- sometimes they are behind the planet, or sitting on top of it where Jupiter's light obscures the satellite as seen with 7X binoculars. (Galileo was able to describe the passage of the moons across the face of Jupiter with his 30X? telescope before they went around the back.) This simple exercise with very basic equipment should fill you with a sense of wonder that you can make an observation about the nature of the universe that was absolutely inaccessible to all humans who had ever lived up to that moment.
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Old 12-09-20, 05:06 PM
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Originally Posted by capt_velo View Post
I think you have a couple of days to go if you're still in Canada, conspiratemus1

Here in the DFW, we had our earliest sunset on Dec. 3.

https://earthsky.org/earth/winter-so...d-late-sunrise
Fair enough. The tables I was using had a period of about 10 days where the sunset and sunrise didn't change within a resolution of one minute. So I took the midpoint day as close enough for government work.. And I didn't compare for other places, other than to notice that both hemispheres experience it near the December solstice regardless of whether it's winter or summer locally. At the June solstice, it's bang on.
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Old 12-09-20, 05:18 PM
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Pics or it didn't happen.




All this talk about sunsets, and not one shot? Not even with some gorgeous C&V bike in the frame? Is this still a bike forum?
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Old 12-09-20, 06:16 PM
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I didn't mention this earlier, but the equation of time is a sore subject with me. I once wrote a fairly long article about it for Yankee Magazine--they assigned the piece to me, for some reason. This was probably sometime in the early 90s. In addition to some other research, I spent an hour on the phone with an expert from the US Naval Observatory in Washington, and thought I understood it all. Based on my copious notes, I wrote the article, which appeared in the magazine some months later.

A few days after the article came out, I got a call from my editor there, a nice guy named Tim Clark. He said that they'd received a letter from someone claiming that my explanation was completely, ludicrously wrong. "What do you think?" he asked me. "Is the guy just a crank?"
I replied that I was pretty confident about my research, and that the writer probably was a crank. "Okay," Tim said.

A few days later, I got another call from Tim, saying, in essence, okay, we have a whole pile of those letters now--I think we have a problem.

Holy crap! I wrote back to Tim and told him I'd figure out where I'd gone wrong and write a correction and send it in for them to run in the letters column. "Nah," he said, "don't worry, I'll take care of it."

The next month, the magazine ran a selection of the letters taking me to task for being a moron. At the end of them, Tim added a little editor's note in italics, thusly: This is why we usually don't assign these kinds of articles to English majors.

Man, talk about getting thrown under the bus! It hurt, especially because I never was an English major. I briefly considered writing a sharp note pointing out that I did not, in fact, have a college degree of any kind, but then thought the better of it.

At least I deserved to get thrown under the bus. The whole thing was actually kind of a useful learning experience about incorrectly interpreting information in light of what you mistakenly think you already know, and piling error on top of error.

Of course, I still do that pretty often--but maybe not quite often as I might have.

EDIT: After reading back a couple of posts, I can see that I should have subcontracted that story to conspiratemus1.
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Old 12-09-20, 06:38 PM
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Coincidentally, I bike commuted to the office today, which has become uncommon lately due to Covid, and the time of year. I was cognizant of the sun setting at 4:20pm (41.63 deg. N here) but was able to put in 8 hours, barely, before quitting, and yet arrive home before darkness. Glad to know it gets better from here on.
Thanks to those with the explanations about analemma (ouch, too close to ****enema! ). I was aware of the asynchronicity between earliest sunset, latest sunrise, and shortest daylight day, and suspected something like that was up, but never got around to looking into it. I also assumed that the figure 8 on the globe was the key, but never tried to decipher it.
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Old 12-09-20, 06:59 PM
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This far north, the sun is so low in the sky, it really doesn't matter the exact minute of sun-up and sun-down = it is not even strong enough to evap the dew on a clear day.

Time to 'moss out'.
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Old 12-09-20, 07:07 PM
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Originally Posted by conspiratemus1 View Post
....
As per John E, the analemma explains it, and check out the really cool composite photos where one of the exposures (the first, presumably) captures a solar eclipse! The two lobes of the figure 8 are not symmetric, owing to the eccentricity of the earth's orbit.
........

I just think it's gratifying that you can use simple observations (aided by timepieces not available until recently in human development, say, mid-18th Century) to take a step toward understanding the true nature of the heavens. (To make an analemma you have to observe the sun at exactly the same clock time every day, a meaningless concept before the naval chronometer.) I'm not embarrassed to say I am profoundly moved by this.
ah yes... the key word is "analemma".
A friend had introduced it to me, but I'd forgotten about it. The wikipedia page is helpful to me... https://en.wikipedia.org/wiki/Analemma
The page on "mean solar time" helps too.
If I understand correctly, the time when the sun is at the center of its travel from east to west would normally be considered noon, but due to the varying speed caused by the elliptical orbit, it will occur a bit earlier or later than a mechanical clock would predict.
As others have noted too, it's nice to understand the weird figure 8 that would be printed on globes, back when people still had globes.

Steve in Peoria
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Old 12-09-20, 07:16 PM
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Originally Posted by BFisher View Post
Pics or it didn't happen.
All this talk about sunsets, and not one shot? Not even with some gorgeous C&V bike in the frame? Is this still a bike forum?
good point!
Since I was talking about bike commuting and the importance of knowing the sunrise and sunset times, let me offer a shot of my last day of bike commuting (very shortly before retiring).
It was taken at 7:21am, on Dec 11th, looking eastwards towards the rising sun....
I was just about to lock up the bike and go inside.



Steve in Peoria
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Old 12-09-20, 08:38 PM
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It was 50 in Chicago, so I went out mid-afternoon. Noticed the 4:20 sunset. Good that the darkness pushed me home - I had a work call at 4:30. Cycling clothes, no video
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Old 12-09-20, 09:12 PM
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Old 12-09-20, 09:16 PM
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thanks for the explanation...

I've noticed the effect over the years but have always focused on my dislike of the 21st being the first day of winter. I hate winter. And worse, I was born on it!
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Old 12-09-20, 10:09 PM
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Originally Posted by conspiratemus1 View Post
Yes, from mow until the summer solstice, the sun will be up in the evening a little longer every day. The shortest day is not until 21 Dec. but owing to the elliptical nature of the earth’s orbit, the apparent movement of the sun gets enough out of kilter with the clocks this time of year that the clock timing of sunrise, noon, and sunset gets shifted. By Christmas, you will notice the afternoon sun definitely lasting longer.

The downside for those who have to get up early is that latest sunrise doesn’t occur until about 10 Jan. So those post-New Year commutes make for awfully dark mornings.

This “time-shifting” has nothing to do with the seasons per se. It’s just the orientation of the ellipse happens to make the effect strongest in that portion of the orbit that we call December. “The equation of time.”​​​​​​
Great post. I always hate the media's declaration of the seasons.

Our earliest sunset is in progress:

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Old 12-09-20, 10:23 PM
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Originally Posted by steelbikeguy View Post
ah yes... the key word is "analemma".
If I understand correctly, the time when the sun is at the center of its travel from east to west would normally be considered noon, but due to the varying speed caused by the elliptical orbit, it will occur a bit earlier or later than a mechanical clock would predict.
As others have noted too, it's nice to understand the weird figure 8 that would be printed on globes, back when people still had globes.

Steve in Peoria
Everyone should own a globe. I pored over mine when I was a kid. Africa is enormously bigger than Canada and Greenland. It is useful today for Europe to visualize that an ICBM launched from North Korea could hit Munich (if it had the range) in less time than it would take to reach Chicago. Only on a globe can you see this. I'm getting one for my grand-daughter as soon as she's old enough. Two-and-a-half is still a bit young.

As described in https://en.wikipedia.org/wiki/Longitude_by_chronometer, the Equation of Time (which is what an analemma depicts graphically) must be consulted to correct local determinations of noon when using a marine chronometer to calculate longitude at sea, a feat previously considered impossible. This was especially so for long voyages of exploration to the South Seas (where the analemma lives on globes to this day!) Controlling scurvy and finding the longitude made the British Empire possible. Dava Sobel's book, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is highly recommended.

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Old 12-10-20, 10:35 AM
  #23  
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Originally Posted by jonwvara View Post
I didn't mention this earlier, but the equation of time is a sore subject with me. I once wrote a fairly long article about it for Yankee Magazine . . ..
Thanks for sharing this painful story, John.
I think the editor treated you in a detestably shabby manner. In no way did you deserve to be thrown under the bus publicly. The editor ought to have taken responsibility for your article at two occasions. First he should have done his own fact-checking before running it. Editors are supposed to have Rolodexes full of people they can call up for a second pair of eyes. Then he could have said, “Uh, John, I think you’re a little off base here...” and saved you both, and the magazine, a lot of embarrassment.

Second, he should have manned up about the critical letters and admitted that he made a mistake personally in running the article as written, without publicly humiliating you for it. There are face-saving ways to do this, even if it’s just the wishy-washy “Mistakes were made...”. But better would have been, “Yankee Magazine acknowledges responsibility and regrets its errors.”

Early in the pandemic, The Lancet ran an article that appeared to debunk anti-malarial drugs in treating Covid-19. Within days it was clear that the authors had invented their findings using imaginary data and the journal had to apologize to its readers for its negligence in editorial oversight. The findings were literally too good to be true. Sure, the study’s authors were bad guys but the journal didn’t get off the hook just by saying, “Oh, well, we got scammed, tra la, tra la...”. It goes to the heart of their scientific credibility and integrity.

I do hope your writing career recovered and thrived from that learning experience. (And here I’ll feel a little silly if you turn out to be a Pulitzer or Nobel winner unbeknownst to me.)

-Les
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Old 12-10-20, 11:17 AM
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6:54am, leaving on my 9 mile commute:



Picture taken with this thread in mind.

I'm in that odd group of people that are working from work. I was going in only 2-3 days/week per our COVID protocols, which were changed slightly recently and some people are allowed in 5 days/week (I'm one of them). My riding mileage has really dipped this year, now that I'm back on a regular schedule it's getting back to normal. Heck, my bike ride in is the one part of my day that is exactly like the before times, so I really appreciate it now. Like others have said, knowing that the morning light will be coming a bit earlier every day now is something to look forward to. Right now any little thing to look forward to is welcome, and for that I thank the OP.
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Old 12-10-20, 11:40 AM
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Originally Posted by conspiratemus1 View Post
...science...
I find this kind of thing fascinating. At the risk of derailleuring the thread, do you have any thoughts regarding something like the Hafele–Keating experiment?
I say we all ride bikes really fast eastward. Immortality!
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