Thursday, December 21, 2023

Friday, September 29, 2023

Happy Friday

Where has September gone?

This is a view of the Sandia Mountains in Albuquerque, New Mexico. It was the last place I lived that had an autumn to remember: beautiful colors, cooler days and nights, and barely a hint of winter.  Autumn there seemed to last until spring, at least compared to northern Michigan.  Allen and I moved to Albuquerque in October 1995, leaving Petoskey in a snowstorm and arriving on a warm and sunny afternoon.  We soon found a house and began to plant a garden, knowing that things would grow year-round.  Yes, we had cold weather during the months that the calendar said it was winter, but the days were sunny, snowfall a rarity, and when it did, we had passive snow removal: the sun.  In the six years I lived there, it never got below zero.  It rarely went below freezing during the day.

One of my fondest autumn memories was the roasted chiles that were sold from vendors parked in the corner of supermarket parking lots.  They tasted great on everything, and the smoke smelled like cheap pot.  Or so I was told.

We do get autumn here in Florida.  The daylight is shorter and the humidity drops, the rainy season tapers off, and it feels a lot like a nice summer day in northern Michigan.  But we don’t get the spectacular color of the trees.

Wherever you are, I hope you take the time to enjoy the change of seasons, however it shows itself.

Saturday, September 23, 2023

September Equinox

Here comes autumn to the Northern Hemisphere; spring to the Southern.  Here in Florida, it means… not much.  But it occurs at 2:50 a.m. EDT nevertheless.  And it does strange things to the moon’s appearance.

The September equinox is here, and it does strange things to the Moon.

Throughout the year, the moonrise happens about 50 minutes later each day, on average, around the Full Moon phase. But if you look at our moonrise times for September, you’ll notice that the day-to-day interval is much shorter around this time of the year for Northern Hemisphere locations: about 25 minutes for New York and under 10 minutes for places at higher latitudes, like Edinburgh in the UK.

This has to do with Earth’s axial tilt. At the September equinox, the North Pole is tilted away from the Moon during the First Quarter Moon phase and toward the Moon during the Third Quarter.

For Northern Hemisphere dwellers, this means the Moon goes from rising unusually late (and setting early) at the First Quarter to rising unusually early (and setting late) at the Third Quarter.

This effect is greatest around the Full Moon, the phase at the midpoint between the Third and First Quarters, making for exceptionally short intervals between moonrises. In Edinburgh, the Full Moon on September 29 will rise at 19:04 (7:04 pm)—just 7 minutes later than the previous day.

All this may seem quite inconsequential for us today—but this warping effect has informed one of the best-known traditional Full Moon names still in use today: the Harvest Moon.

So, where’s the connection?

Imagine you’re a 19th-century farmer trying to bring in the harvest before the frost sets in. In some years, it can be a race against time, so you want to be able to keep harvesting even after dark.

This is where the Moon comes in: just as the Sun sets, the second-brightest object in the sky makes its way across the horizon, illuminating your crops and making your life a whole lot easier.

That’s why the Harvest Moon was defined as the Full Moon closest to the equinox in September. All other traditional Full Moon names are related to specific months—for example, the Strawberry Moon is the Full Moon in June. The Harvest Moon, on the other hand, can happen in September or October, depending on its proximity to the equinox.

Funnily enough, just about two weeks after the Full Harvest Moon brightens up our night sky, the New Moon will darken the day sky in some parts of the world: on October 14, an annular solar eclipse will sweep across the Americas, plunging everyone and everything in its path into relative darkness.

“Oh, shine on, shine on Harvest Moon…”

Wednesday, June 21, 2023

Monday, March 20, 2023

March Equinox

Spring arrives in the Northern Hemisphere at 5:24 p.m. Eastern Time today, all things being equal.

Because the earth is a spheroid, not a perfect sphere, the hours of equal daylight and sunlight, known to meteorologists as “equilux,” was last week, on March 16, here in Florida.

As far as I’m concerned, we’re getting more daylight, and I like that.

Wednesday, December 21, 2022

December Solstice

Winter arrives in the northern hemisphere today at 4:48 p.m. ET here in Miami.  It is the day with the shortest amount of daylight, but at 4:49, it starts lengthening until next June.

But the times they are a-changin’, according to Time-and-Date:

The December solstice—when the North Pole is at its maximum tilt away from the Sun—is the shortest day of the year in the Northern Hemisphere. It can fall on December 20, 21, 22, or 23.

This year it falls on December 21 or 22, depending on your time zone. In New York City, the daylength (the amount of time between sunrise and sunset) will be 9 hours, 15 minutes, and 17 seconds.

But did you know the length of the shortest day is increasing by a few seconds each century? It is also fluctuating in an 18.6-year pattern linked to the orbit of the Moon.


The reason for this is that the Earth’s tilt is slowly decreasing, as part of a repeating cycle that lasts 40,000 years or so.

Today the Earth’s tilt is about 23.4°. But roughly 10,000 years ago it was around 24.2°, while 10,000 years from now it will be about 22.6°.

This small decrease in the tilt of the planet reduces the maximum tilt of the North Pole away from the Sun. This has the effect of making both the shortest and longest days of the year less extreme.

Eventually, the Earth’s tilt will begin increasing once more, and the year’s shortest day will start to become shorter again.

A degree here, a degree there…

And to those of you in the southern hemisphere, enjoy the summer while it lasts.

Friday, October 21, 2022

Happy Friday

The dry season — what passes for winter — has arrived in South Florida.  It’s cooler outside than inside, and the humidity level is down to tolerable.  This is what will bring the snowbirds here.  It’s also the middle of the frantic campaign season and the negative ads from both sides are rampaging through the TV screens, which makes me grateful for TiVo and various streaming services.

At any rate, enjoy the change of seasons.

“The Dinghy Beach” by Marguerite Cassidy (1919-2005)

Tuesday, June 21, 2022

June Solstice

Summer begins in the northern hemisphere at 5:13 a.m. here in Miami with the June solstice.  It means the beginning of winter in the southern hemisphere.

As you’ll remember from Grade 8 Earth Science class, summer is short for latitudes farther north and south, but they get more daylight during the summer months.  After ten days in Alaska, last night was the first time I’d seen full dark at night since June 9.

Sunday, March 20, 2022

Wednesday, December 22, 2021

Winter Moon

I took this view of the moon in the northwest sky over Miami yesterday morning as the harbinger of the approaching winter.  The location of the moon in the sky is where the sun will be in six months.  The sun and the moon trade off as the seasons change: as the sun moves north, the moon moves south relative to our point of view on Earth.

Tuesday, December 21, 2021

Sunday, November 7, 2021

Sunday Reading

That Time Again — David Policansky in the Washington Post on the shifting time debate.

It’s that time of the year again. We change the clocks back and we whine about it.

What might be done to improve things? Well, before we can talk about possible improvements, let’s review the rules pertaining to changing the clocks and their benefits and drawbacks.

We start observing standard time on the first Sunday in November, according to the Uniform Time Act of 1966 and some amendments. This week, we turn the clock back an hour Sunday morning. Then, on the second Sunday in March, we will go back to Daylight Saving Time.

Not everyone does it, because the act allows states not to observe Daylight Saving Time. Of the states, only Arizona and Hawaii don’t observe Daylight Saving Time (although parts of the Navajo Nation in Arizona do). A state cannot stay on Daylight Saving Time, however; the best it can do is appeal to the Department of Transportation to be moved to a different time zone, which could have the same effect.

To state the obvious, Daylight Saving Time doesn’t save time and it doesn’t save daylight. In fact, the problems associated with wanting to switch the clocks stem from the fact that there just isn’t enough daylight to go around in the winter. That problem is more acute the farther one is from the equator. In Miami, on the winter solstice (the shortest day of the year), the sun rises at 7:03 a.m. and sets at 5:35 p.m., while in Fairbanks the times are 10:58 a.m. and 2:40 p.m. (both standard time). Most of us live at less-extreme latitudes, so let’s look at Washington: Here the sun rises at 7:24 a.m. on the shortest day and sets at 4:50 p.m.

But north and south aren’t the only factors that affect daylight: our position in the time zone also can have a large effect. Let’s compare Indianapolis, in the far western end of the Eastern time zone, with Boston, at the far eastern end. At the winter solstice, the sun rises at 8:02 a.m. in Indianapolis and sets at 5:23 p.m., while in Boston the times are 7:10 a.m. and 4:14 p.m. You really notice the dark winter afternoons in Boston and you really notice the dark winter mornings in Indianapolis.

Now let’s look at some proposed solutions.

Several states have passed or are considering laws that put them on permanent Daylight Saving Time, and several senators of both parties have proposed similar legislation in Congress. That might be acceptable if you live in Boston (or Chicago, at the far eastern end of the Central time zone), but the good people of Indianapolis would not see the sun rise until after 9 a.m. for a few weeks in the winter. I don’t think they would like that.

Lawmakers consider keeping daylight saving time year-round.

Another possibility is to stay on standard time all year, but then you have those dark afternoons in Boston and Chicago, and furthermore, on standard time the sun would rise at 4:06 a.m. in Boston in June, which means you’d have to get up by 3 a.m. to do anything at sunrise.

As an aside, due to peculiarities of the tilt of the Earth’s axis and its orbit, we lose far more daylight in the mornings at mid-latitudes after the beginning of standard time than we lose in the afternoons as the days continue to shorten. The switch to standard time is on the latest possible date this year, but the latest sunrise (in early January) in Washington is still 42 minutes later than it will be on Sunday, while the earliest sunrise (in early December) is only 11 minutes earlier than Sunday’s.

So what is to be done? Well, the people of Fairbanks show that it is possible to adjust to very early sunsets or very late sunrises. There just isn’t much advantage in shifting daylight around when you have only three hours and forty-two minutes of it on the shortest day. But in the Lower 48, in the mid-latitudes where most of us live, we complain.

So why not just live with whatever the geographic cards have dealt us with respect to time changes? Well, switching the clocks is a royal pain, and some of us hate doing it. But it’s not only inconvenient; myriad studies show small but significant increases in stroke, heart attack and other diseases and in death rates after changing the clocks, particularly after the spring forward change. Other studies have shown increased risk of accidents after the spring time change.

But Daylight Saving Time reduces energy consumption, doesn’t it? Well, that’s doubtful, too, and if it does save energy, the amount is very small at best.

So I am not optimistic that this nutty business of changing clocks, which became widespread only a little more than 100 years ago, will be going away soon.

My guess is that opposition to the proposed federal legislation to adopt permanent Daylight Saving Time in the United States will make it difficult to pass. Another option, to allow each state to choose whether to adopt permanent daylight or standard time, would result in chaos and is thus also improbable. Moreover, these arguments are not new; they are as old as Daylight Saving Time itself. So prepare to do some whining, and above all, make sure you get enough sleep.

The author, David Policansky, is a retired scientist who previously served as associate director of the Board on Environmental Studies and Toxicology at the National Research Council.

Doonesbury — To the rescue.

Wednesday, September 22, 2021

Sunday, June 20, 2021

June Solstice

This year it occurs at 11:32 pm EDT/7:32 pm AKDT, where I am now.  It signals the longest period of daylight in the Northern Hemisphere, and the beginning of the inexorable trek to the shortest in December.

Saturday, March 20, 2021

Tuesday, September 22, 2020

Saturday, June 20, 2020

Thursday, March 19, 2020

Vernal Equinox

Spring arrives in the Northern Hemisphere at 11:48 p.m. EDT.  It’s the earliest equinox in 124 years.

Most years, the spring equinox falls between March 20 and 22. But for those in the United States, not this year. In fact, reports that the March 19 equinox is earlier than any in the past 124 years.

Perhaps the early equinox is fitting in a year during which springlike weather arrived weeks in advance in many parts of Lower 48. The USA National Phenology Network, which tracks the timing of plants, reported that trees were leafing up to three to four weeks early in many parts of the southern and eastern United States due to the mild weather, starting in February.

Saturday, December 21, 2019