StarDate

That’s the introduction to a radio play based on a story by Isaac Asimov, one of the most influential science-fiction writers ever — and one of the busiest. He wrote or edited 500 books and thousands of short stories and magazine articles.

Asimov was born 100 years ago today, in Russia. His family emigrated to the United States when he was three.

During World War II, Asimov worked as a civilian chemist for the Navy. Afterward, he earned a PhD in biochemistry, and joined the faculty of Boston University — a position he held for decades. He discovered, though, that he preferred writing to research. He published his first short story in 1939, and his first novel in 1950.

Asimov is best known for his three laws of robotics, and for the “Foundation” series — stories that chronicled the fall of a galactic empire and the start of another.

Asimov didn’t limit himself to science fiction, though. He also wrote mysteries and other fiction. And in the 1960s he turned mostly to science fact, with forays into history, religion, and even Shakespeare.

Asimov died in 1992. But his fellow scientists have named an asteroid and a crater on Mars in his honor — tributes to an author who transported millions of readers to the stars.

Script by Damond Benningfield

Thanks to William Shakespeare, Julius Caesar is forever linked with the calendar in the public mind. In the dramatization of Caesar’s life, a soothsayer warns him to “beware the ides of March” — the date on which Caesar was assassinated.

And today, we’re linked to Caesar by the calendar itself. He’s responsible for the basic calendar system we use today.

Before Caesar’s reform, the Roman calendar was a complete mess. The months didn’t match the cycle of seasons. Extra weeks were sometimes added between months, but they didn’t solve the problem. By Caesar’s time, the calendar and the seasons were way out of sync.

So Caesar asked the astronomer Sisogenes to help reform the calendar. Sisogenes recommended adding 67 days to the year that’s known today as 46 B.C. That would bring it into alignment with the seasons. He then outlined a year whose 12 months added up to 365 days. An extra day was added every fourth February to stay in time with the seasons.

The calendar was tweaked a bit over the following few years, and a change in the leap year was made many centuries later. Even so, the modern calendar is pretty much the one outlined by Sisogenes.

The Romans had a different way of numbering the days of the month, though. The middle of the month was known as the “ides,” while the start of the month was the “kalends.” So today is the kalends of January — the first day of a new year in a calendar made possible by Julius Caesar.

Script by Damond Benningfield

New York celebrated New Year’s Eve of 1904 with a bang — a fireworks display atop the brand-new offices of the New York Times. The show was repeated over the following couple of years. By 1907, though, the fireworks had been banned. So the Times came up with a new lightshow: a 700-pound ball of iron and wood festooned with a hundred 25-watt bulbs. It dropped to the bottom of a long pole at midnight — marking the arrival of 1908.

The New York time ball is much more elaborate now — it weighs six tons, and consists of more than 30,000 LED lights and 2700 crystal triangles. Yet it’s continuing a tradition that began in the early 19th century — marking time by dropping a ball.

The first time balls were set up in England. They provided the precise time to ship’s navigators. The navigators needed to know the correct time to plot their longitude. Many time balls were operated by observatories, which determined the time by plotting the Sun’s highest point in the sky.

The first American time ball was at the U.S. Naval Observatory, at Washington, D.C., in 1845. A few years later, the observatory began sending the time to New York via telegraph. There, a time ball atop the Western Union building dropped at noon.

Time balls were operated well into the 20th century — until their function was replaced by radio. But New York’s time ball continues to drop — beginning its journey at 11:59 p.m. and ending at midnight.

Script by Damond Benningfield

Observatories of the 19th century didn’t receive government funding. They relied mainly on private donors, although they sometimes had to get creative to pay the bills. The Cincinnati Observatory, for example, sold time — for a thousand dollars a year.

The observatory was one of many that operated a time ball. The ball was placed on a pole atop the dome. The ball was dropped at precisely noon — allowing businesses and individuals to synchronize their clocks.

Observatories provided the service because they had special instruments that allowed them to calculate the precise time of local noon — the moment the Sun was highest in the sky. That made them perfect timekeepers.

Time balls were first used in England. Ship’s navigators needed to know the time to plot their longitude — their east-west position on the globe. To do that, though, they had to have a reference point — a point where they knew the exact longitude and the correct time.

So a young officer in the royal navy suggested a time ball. The ball would be dropped from a high point at a specific time. Navigators aboard ship could observe the drop by telescope, and use the time to set their chronometers.

The first time ball was in Portsmouth, in 1829. An additional time ball was set up atop the Royal Observatory at Greenwich in 1833. The ball was dropped at precisely 1 p.m. And it still operates today — keeping time for all to see.

More about time balls tomorrow.

Script by Damond Benningfield

Like Bruce Wayne and Tony Stark, the star El Nath has a dual identity. It’s the second-brightest star of Taurus, the bull. But it’s also the second-brightest star of Auriga the charioteer.

Officially, the star belongs to Taurus, so it’s also known as Beta Tauri. And the name “El Nath” means “the butting one.” That’s a reference to the star’s position at the tip of the bull’s horn. But the star also is part of the classical connect-the-dots pattern that outlines Auriga.

When those constellations were first drawn, thousands of years ago, no one was too concerned about which star belonged to which constellation. So it was no problem for a star to perform double duty.

In the early 1900s, though, astronomers decided it was time to bring a little order to the chaos in the constellations. They designated 88 official constellations, and gave each one precise borders. Under this arrangement, El Nath assumed permanent status as a member of Taurus. Yet it’s still part of the classical outline of Auriga — maintaining its dual identity.

There’s one other interesting tidbit about El Nath’s position. The star stands opposite the direction of the center of the Milky Way. So as you look toward the star, you’re looking into the Milky Way’s thinly settled outer precincts — and the intergalactic space beyond.

El Nath is in the east as night falls. The star is well to the left or lower left of Taurus’s brightest star, Aldebaran, the bull’s orange eye.

Script by Damond Benningfield

Venus is a world you wouldn’t want to visit. Surface temperatures are hot enough to melt lead. The atmospheric pressure is equal to being almost two-thirds of a mile deep in Earth’s oceans. And the atmosphere is made almost entirely of carbon dioxide. Paradise it’s not.

Research over the last few decades, though, suggests that Venus could have been much more pleasant when it was young — perhaps pleasant enough for life. A study reported this fall, for example, suggests that temperatures could have remained comfortable for two billion years or longer.

The study built on observations by orbiting spacecraft. The probes found that Venus once had a lot of water on its surface. The study simulated conditions with different amounts of water — from damp soil to a global ocean. It also considered the amount of energy Venus received from the Sun, and other factors.

The conclusion was that Venus could have maintained surface temperatures of about 70 to 110 degrees Fahrenheit. That’s much warmer than modern-day Earth, but fairly comfortable for life. And that environment could have been maintained until less than a billion years ago, when molten rock began to repave the surface. So if life ever appeared on Venus, it could have had a comfortable home for a long time.

Venus is climbing higher into the evening sky. It’s the brilliant “evening star.” It’s just above the crescent Moon tonight, and a bit farther to the lower right of the Moon tomorrow night.

Script by Damond Benningfield

Our solar system sits on the edge. It’s at the inner edge of a spiral arm — a curving blade of stars and gas that wraps around the center of the Milky Way Galaxy. It’s known as the Orion Arm because it includes many of Orion’s brilliant stars.

The stars and gas clouds of the Milky Way form a wide, flat disk. Hot young stars, which are born in big clouds of gas and dust, outline curving spiral arms. So from afar, the galaxy would look like a cosmic pinwheel spinning through space.

We can’t see the spiral structure directly, though, because we’re inside the disk. But astronomers can get a rough outline of the spiral arms by using radio telescopes, which map giant clouds of gas throughout the disk.

Those observations suggest that the Milky Way has two major spiral arms, which wrap all the way around the galaxy, plus a few smaller ones.

That includes the Orion Arm. Until recently, it wasn’t really considered an “arm” at all. Instead, it was called a “spur” — a fairly short streamer between two larger arms. But a study a few years ago found that it’s about 20,000 light-years long — long enough to be a spiral arm. Our solar system sits near the arm’s inner edge.

And Orion is entering prime time now. The constellation is in good view by about 7 o’clock. Look for a short line of three stars pointing up from the east-southeastern horizon, flanked by a couple of much brighter stars — some of the more prominent members of the Orion Arm.

Script by Damond Benningfield

The Northern Cross stands in the northwest this evening, with the “shaft” aiming roughly toward the horizon. If you have clear, dark skies, you might notice that the cross is embedded in the glow of the Milky Way. This hazy band of light outlines the disk of our home galaxy, which is also known as the Milky Way.

Many of the details about the disk are unclear. That’s mainly because we’re inside it, so we can’t see its overall structure. It’s like trying to map a forest if you’re stuck at a single spot inside it — you get a nice view of the nearby trees, but everything else is hidden.

Several tools allow astronomers to see the forest through the trees. Radio telescopes can map giant clouds of gas throughout the galaxy. Infrared telescopes can see stars that are otherwise hidden behind clouds of dust.

Other telescopes can see stars and star clusters outside the disk. Plotting their motions helps astronomers deduce what’s happening in the disk.

Most studies have said the disk is about a hundred thousand light-years in diameter, and an average of about one thousand light-years thick. The numbers published in recent years, though, challenge that model. A study in 2015 put the diameter at 150,000 light-years. And one in 2018 gave a diameter of up to 200,000 light-years.

So astronomers are still trying to map out the true size of our galactic home: the Milky Way.

We’ll talk about our place in the galaxy tomorrow.

Script by Damond Benningfield

The Sun and Moon offer much of the eastern hemisphere a nice holiday treat tomorrow: a solar eclipse. The Moon will pass directly across the face of the Sun. Along a narrow path, that’ll create a brilliant “ring of fire.” Outside that path, it’ll be a partial eclipse.

This is called an annular eclipse. The Moon won’t completely block the Sun. Instead, it’ll leave a thin ring of sunlight around the Moon.

One reason is that Earth is near its closest point to the Sun now, so the Sun is a slightly larger target than average. As a result, the Moon is not quite big enough to cover the Sun’s disk. At most, it’ll cover 94 percent of the Sun. The exposed ring of sunlight is still too bright to look at. But enough of the Sun will be covered to make the sky look dusky, and to drop the temperature by several degrees.

The eclipse gets under way this evening on American clocks, but at sunrise on the 26th for the eastern hemisphere.

The path of the annular eclipse will be about 75 miles wide. The eclipse will begin over the Arabian Peninsula, cross the southern tip of India, and pass over the city of Singapore. The only American territory to see it will be the island of Guam, in the western Pacific Ocean, near the end of the eclipse.

Most of Asia and half of Australia will see a partial eclipse — the Moon will cover part of the Sun. And those of us in the western hemisphere can catch it on the web — a ring of fire in eastern skies.

Script by Damond Benningfield

Although it won’t happen until the day after Christmas, a NASA spacecraft is ready to give something to the planet Venus: a bit of its orbital energy. That will allow the craft to move closer to its target: the Sun.

Parker Solar Probe is designed to study the Sun’s hot but thin outer atmosphere, known as the corona. It’ll also study the solar wind, and the Sun’s complex magnetic field.

To do all of that, though, it has to get close to the Sun, which is harder than you might think. It has to cancel out Earth’s orbital speed and fall toward the Sun, but not into it.

In fact, Parker will spend seven years reaching its target distance from the Sun. It’ll orbit the Sun 24 times over that period, and make a total of seven passes by Venus.

Those encounters allow the craft to refine its orbit. It transfers some of its orbital momentum to the planet, so it will drop closer to the Sun on each pass. In its current orbit, it takes 150 days to circle the Sun. After its Thursday encounter with Venus, though, the orbital period will drop to 130 days.

Parker Solar Probe has already passed closer to the Sun than any other craft — about 15 million miles. That’s about half the previous record. That’s allowing it to probe regions around the Sun that no one has seen before.

But that record is only the first of many. Parker Solar Probe will reach its target distance from the Sun in 2025 — less than four million miles from the surface of our star.

Script by Damond Benningfield