#41: - Why Your Day is a Day Long - Eating at Planetary Restaurants - & 2 More Stories
TGT 2/15/23: AAS: Why Earth's Day HAS to be 24 Hours Long; Evening Sky is a Planetary Traffic Jam; Restaurants and Bars with Planetary Names for the February Holidays; MSU Shooting
Cover Photo - Yes, Days Are Getting Longer, But Not As Long As They Could Have Been!
In This Issue:
Cover Photo — Yes, Days are Getting Longer But Not As Long As They Could Have Been!
Welcome to Issue 41!
AAS: Why is Our Day a Day Long? (Cover Story)
Sky Planning Calendar —
* Moon-Gazing - Moon and Planets Meeting Everywhere!
* Observing—Plan-et - Venus, Jupiter and Mars Have the Whole Show
* Border Crossings
* For the FutureAstronomy in Everyday Life - Eating and Clubbing at the Planets
Highlights of Issues 45 and 46 of The Classroom Astronomer Newsletter-Inbox Magazine
Commentary on Michigan State Shooting
Welcome to The Galactic Times Newsletter-Inbox Magazine #41 !
February is ending, and while it is the shortest month (and the nights are still longer than the day light), the Earth’s DAY is as long as it has every been! Why? Blame the Sun. In fact, thank it, or our days would be DAYS long.
The final parts of the evening planet show are in progress. The Moon is busy these two weeks passing by the planets one by one, and the bright planets are all passing each other, or nearly about to. Comet ZTF is fading away but at least it is in an easy place and time to go find it!
Two holidays are upon us, one just past, one coming up. And a bar fits the bill for both! See our Astronomy in Everyday Life column to see where it is.
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Publisher — Dr. Larry Krumenaker Email: newsletter@thegalactictimes.com
AAS: Why is Our Day a Day Long?
Yeah, I know. Some days seem to take forever and some days don’t have enough hours. Astronomically, in our solar system, days can last for DAYS! Or not.
The shortest planetary day is Jupiter’s, which lasts less than ten Earth hours. At the other extreme is Venus. Watch a star come into view twice and you’ll wait 243 Earth days, longer than its year.
Now, for most planetary worlds, one need not be too careful in how you measure the day. There are two kinds of days, a sidereal day and the synodic, or solar, day. The former is how long it takes to see a star come back to the same place in the sky due to rotation of the world. The latter is the same idea but it includes the effect of the planet’s revolution around the Sun, which adds or subtracts time from the sidereal rate. For fast spinners like Jupiter, Saturn, Mars or Earth, the differences are only minutes, or even seconds. The difference in the sidereal and synodic rates for Earth is only about four minutes, the solar day being the longer. For slow spinners, though, you have to be very specific when you say “day”. Venus’s actual rotation, measured against the stars, IS slow, but how soon between Sunrises? That’s 116.75 days, assuming you could see the Sun in the first place in Venus’ thick as mud atmosphere, but I digress.
It is because Venus rotates backwards and slowly that both types of days are long. But why are the days of all the worlds so divergent? Various reasons. Why is our day 24 hours? Random chance? Nope.
Whatever started the Earth spinning is unknown though it almost certainly has to do with the early time in the primordial nebula and the results of whatever collisions that took place in the Earth’s formation period. All those would set the early Earth a-spinning. The record of the rate of spinning, however, that far back is lost. But we do have the record in the rocks going back at least a billion years. And for that time-frame, the rotation has been relatively constant. Why? Blame the Moon, in part.
We know that the Moon’s orbit isn’t totally steady. It precesses and wobbles and its distance and ellipticity changes over time. We also know it has been with us for more than that one billion years. We know that its gravity causes tides on us, with high tides and low tides roughly every 11-12 hours apart. Tides cause friction, which should dissipate our rotational angular momentum, thus slow us down and make our days longer. The geological data indicates….not.
At an American Astronomical Society plenary talk Prof. Norman Murray discussed rotational history research, in a humorous fashion, on why the Earth spins as it does. He showed that the hours in the day have varied over time, from 14 to 24 per day, and the months from 24 to 32 days per. So why hasn’t the Moon caused us to have a rotation rate that has dropped to zero or at least to a period that perhaps matches the lunar orbital rate so that, like the Moon’s face always facing Earth, we are locked so that one Earth-side is facing the Moon?
The answer is tides. But not the tides you are thinking of.
There are also tides from the Sun, but the gravitational tides from that aren’t very strong. It is not those tides that concern us either. It is the tides from the Sun that are caused by the Sun’s heat. Thermal tides. As the atmosphere heats up, atmospheric pressure goes down. As gravity pulls on the air molecules, this actually gets ahead of the water tides, and thus adds angular momentum into the system.
These thermal tides began most strongly about 2 billion years ago, when the Earth’s temperature was about 40-degrees C and the Sun was dimmer, and there was more Carbon Dioxide in the air and less Oxygen. In fact, the atmosphere alone, a gas, has a resonance point of about 11.4 hours, give or take, as does the atmospheric tides, which head westwards as oceanic, gravitational tides head eastward. The two together caused a resonance that allowed the Earth to rotate at twice this, or 22.8 hours, a day. (See the Cover Photo).
Around 3 billion years ago, our day was about 16 hours. Since then, the days have gotten longer but with a periodicity of a half billion years of variation where it gains and loses 2 hours from its then-current average. It went to 22 hours, dropped to 18, rose back to 22 about half a billion years ago, stayed steady there for a while and then rose back up some more. Right now, the day is 24 and possibly getting longer.
Just a thought….if there is global warming, won’t that FURTHER increase our angular momentum and shorten our days a little?
What is the future? That’s to be seen…..but thank the Sun it is ONLY 24 hours. Otherwise the Moon would have given us a year with only 12 days in it……
Sky Planning Calendar
Moon-Gazing
Moon passages by a star, planet or deep sky object are a good way to find a planet or other object if you’ve never located it before.
February 18 A dawn conjunction between the Moon and Mercury; at the closest the planet is 4-degrees north of Luna but here in the US that gap is 7-degrees.
February 19 Perigee and New Moon for West Coast and Pacific Rim folks…
February 20 …New Moon for Central and Eastern US, and Europeans.
February 21 Find Neptune 2-degrees above the thin evening crescent Moon, if you are really lucky and have a telescope….but you’ll have better luck finding Venus 2-degrees above the Moon ten hours later (Pacific Rim people see it that close but in the US, it is farther apart but still quite picturesque!).
February 22 The Moon gets even closer to Jupiter, 1.2-degrees, tonight!
February 25 Find Uranus 1.3-degrees South of the fat crescent Moon, the last occultation of the planet this year but only if you are near the Arctic.
February 27 First Quarter Moon, just after midnight. Mars gets covered up by the Moon just before or about midnight for Northeastern Asia and FAR northern Arctic regions (Greenland, Faroe Islands, etc), otherwise 1.1-degrees away from the Moon tonight and into the 28th.
Observing---Plan-et
Mercury has been having a good viewing session in the dawn but that’s drawing to a close. By the 20th, it rises only 40 minutes before the Sun and by month’s end it rises only 20 minutes earlier than Sol, pretty much lost in the glare.
Venus, by month’s end, will set about an hour into the evening darkness. It gets passed by the Moon, the 21st-22nd. Venus is approaching its second major planetary conjunction, with Jupiter, in March. Mars will be next.
Jupiter is ending its show in spectacular fashion, heading towards a brilliant double-planet rendez-vous with Venus, just after February ends. It has a nice meeting with the Moon on the 22nd.
Finally, there’s Mars, bright and red in Taurus. Of all the planets, it commands the sky most of the night. By end of February it nearly matches Aldebaran nearby. The Moon passes close by the planet on the 27th for North Americans.
Saturn is taking a break.
Comet ‘ZTF’
The winter comet C/2022 E3 (ZTF) has faded below naked eye limits after reaching (depending on who you ask) a peak of 5.4 or 4.9-magnitude. Yours truly observed it several times, last on February 12 when some rain finally cleared out. It was barely visible in 7x50s in slight light pollution, and in a 1986-vintage CometCatcher wide-field low-power telescope it appeared as an unresolved bright ‘globular cluster’.
The chart below shows you where to hunt for it as it fades out in Taurus and to the west side of Orion….
And Further Afield….
This is a good time of year to watch the eclipses of Algol, the Demon Star, high in the sky in Perseus. But for these two weeks there are no evening eclipses.
Border Crossings
Short overlap between astronomy and astrology—the Sun enters Aquarius on the 16th for real. The horoscopes have it there from before that until the 18th. Then it goes Fish(ing). The Sun doesn’t get THERE until March 12….
For the Future
Brilliant meeting between Jupiter and Venus, just one-half degree apart for the Asian side of the world so best for the Americas the evenings of the 1st and 2nd. That same day Mercury and Saturn have a dawn conjunction but THAT needs a telescope and accurate coordinates and probably not worth the bother.
Astronomy in Everyday Life
Perfect for Valentine’s Day OR Fat Tuesday!
Caught this mentioned in a New York Times article on New Orleans. Now I have a reason for a spring field trip. Anybody know any other planetary named bars or restaurants? I knew of one in Atlanta, many years ago, but I discovered it is long gone now….
The Classroom Astronomer Newsletter-Inbox Magazine #45 and #46 Highlights!
In This Issue (#45, Paid Post):
Cover Photo - Ring of Fire
Welcome to Issue 45!
Deeper Looks - AAS: School-Sized Radio Telescopy
Connections to the Sky -
- Replicating a 1930s Experiment the Modern Way—Animals and Eclipses
- A Funding Opportunity from NASAAstronomical Teachniques - What Can You Learn With a Ring of Fire?
The Galactic Times Newsletter-Inbox Magazine Issue #41 Highlights
In This Issue (#46, Free Post):
Cover Photo - Challenges with The Upcoming Two Solar Eclipses
Welcome to Issue 46!
Astronomical Teachniques & Connections to the Sky (AAS Solar Eclipse Sessions) -
- Prices on Solar Galileoscopes Revealed
- Solar Eclipse Things to Talk About
- How Many Will See The Eclipse?
- Guides Available
- The Eclipse at Your Library
- Live Streaming The EclipseShooting at Michigan State University
I don’t normally bring in political commentary here but this one hurts. In my academic history, I earned an M.A.T. degree in Planetarium Education there, a now-defunct program centered at Michigan State University’s renown Abrams Planetarium, back in the 1970’s. I use their Sky Calendar for reference. I also earned my first teaching certificate there, and my first experiences teaching in schools were in East Lansing. So February 13th’s shooting on the campus really hits home. MSU led me from pure science into education, and immediately afterwards into my moving out of the North.
In my life as a long-time freelance science and astronomy journalist as well as a long-time astronomy and science educator, I have had the unlucky experience of seeing and experiencing far too many violent events. My first one happened even before that, as an undergraduate, with literally a gun in the stomach at my fraternity house during a break-in. How I survived that and stopped the guy from getting any further into his robbery still surprises me and my brothers. I have never been in the military, law enforcement, or government agencies, yet I have witnessed several terrorist and military events firsthand as well as bank robberies and such. I have just been too often in the wrong place at the wrong time, but not as wrong as those I knew who were there and didn’t get survive them.
So forgive me if you don’t like what I say here but if you happen to think that this MSU shooting is a tragedy but see no reason why America has to give up its guns, then I suggest you either go fight in a place like Ukraine or re-enlist in the Army Reserve. THERE IS NO REASON FOR PEOPLE TO DIE IN CLASSROOMS OR ANY OTHER CIVILIAN ENDEAVOR BECAUSE OF GUNS. The idea that good guys with guns are there to put holes in bad guys with guns has as much statistical significance as craters on the Moon with water compared to the number of other holes in the Moon’s surface are a valid reason to go the Moon. There are other good reasons to go to the Moon. Water ice in holes isn’t one of them. We have since learned the shooter had a history of violence with guns and STILL was able to get one.
Just because in 1790 some guys said we should be allowed to have muskets to defend against invading British, Spanish, French or Indians doesn’t mean the thought is valid in 2023. Sorry, this isn’t 1790 anymore, I don’t think we’re going to having musket-waving Brits, Frenchies, Spaniards or Native Americans invading us, and today’s Chinese or Russians are more likely to use missiles that even AR-15s won’t stop. In 1790 Blacks were slaves and worth 2/3rds a White man, and women weren’t worth anything—they couldn’t vote. We changed both (at least, legally). We can change this. We HAVE to change this.
When children can’t control themselves, we take away their things. We don’t seem to be capable of controlling ourselves with guns. They should be taken away until we do. Yeah, some people do know how to handle guns; we can find ways to accommodate that—other countries do—but having three hundred million guns readily available to anybody today just isn’t good.
I’ve personally seen enough gun deaths. I don’t need to see more, and neither does this nation. If you don’t like my thoughts on this, well, you can feel as free to choose to unsubscribe from this free newsletter as much as most of you feel free not to use your credit cards and get a paid subscription to The Galactic Times InDepth or The Classroom Astronomer newsletters. I choose to say ENOUGH OF GUNS and to say freely to you that the Universe doesn’t care about whether you live or die. But I do.
Dr. Larry Krumenaker
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