January 31 - First U.S. Satellite!

 Posted on January 31, 2021

This is an update of my post published on January 31, 2010:

Explorer 1

On this date in 1958, Explorer 1 was launched, becoming the first satellite launched by the United States.

The Soviet Union's successful launch of Sputnik 1 in October of 1957 shocked Americans, and the U.S. was in a hurry to match the feat. The Jupiter C rocket had already been developed, and Pasadena's Jet Propulsion Laboratory was directed to design and build the “payload” (the instruments or equipment) to be carried into Earth orbit by that rocket.

JPL completed the assigned jo
b in less than three months!

The main instrument aboard Explorer 1 was a cosmic ray detector. The experiment on this satellite and another one launched two months later led to the discovery of the belts of charged particles trapped by Earth's magnetic field, called the Van Allen Belts after the experiment's designer.

Van Allen belts

Explorer 1 made its last transmission back to Earth in May of the year it was launched, but it continued to circle the globe more than 58,000 times before orbital decay caused it to burn up in the atmosphere in 1970.

Orbital Decay (or, should our satellites be brushing longer and flossing more?)

When a satellite is in a low orbit around Earth, it may be slowed by “drag” from the Earth's atmosphere. This sets up a positive feedback loop:

The increased “drag” or friction from the atmosphere causes the satellite to reduce in speed.
Decreased speed causes the satellite to fall to a lower altitude above Earth.
A lower altitude means that the atmosphere the satellite encounters is denser (more molecules of gases per cubic foot).
The denser atmosphere causes even more friction.
Which causes even less speed.
Which causes an even greater fall in altitude.
Which means that the satellite is orbiting in even denser atmosphere.
And so on.
And so forth.

Eventually, the orbit is so low and the atmosphere so thick, the satellite encounters a lot of friction and burns up.

Orbital decay can affect, not only satellites, but also space stations, space shuttles, and even the Hubble telescope. The International Space Station regularly needs orbital boosts to fight against orbital decay.

International Space Station

Most satellites orbit our globe high enough that they encounter no atmospheric drag and therefore no orbital decay due to friction.

Instruments on Mars

JPL has had a lot of opportunity to design experiments for a variety of space exploration vehicles. In January 2010 we got some news about one of JPL's programs, the Mars Rover Program.

The bad news was that Spirit, one of the two rovers currently on Mars, had not been able to be UN-stuck from the soft sand that had trapped it since May 1, 2009. The scientists decided to stop attempting to move it but hoped that it would be able to do more science from its "stuck" position. (That didn't really happen, though; Spirit sent its last message to Earth in March, 2010.)

The good news was, Spirit and the Mars Rover Program had already been incredibly successful! As astronomer Phil Plait explained at his excellent blog “Bad Astronomy” (available here on Discover Magazine):


Spirit and Opportunity “had a planned operational lifetime of 90 days. “That was in January 2004. “In other words, Spirit has been on Mars for over 2200 days, and even counting when it first got stuck, it still ran well for more than 20 times its nominal lifespan. Cars these days have a standard warranty for 7 years; how’d you like yours to run for 140 years?

So for me, while this news is not great, it has to be put in context: Spirit is one of the most successful NASA missions of all time. And its sister, Opportunity, is still running like a champ. I hope I’ll be doing as well when I’m 1400 years old.

Opportunity continued to function until mid-2018!!! That was about 55 times longer than its original hoped-for mission!!!



Experiments on Earth

  • Here is a hands-on experiment on the same topic.
  • NASA has a page for anyone who wants to spot the International Space Station in orbit.
  • Here's another NASA site. This one focuses on Mars, with games and other activities. Very fun!

Also on this date:

Street Children's Day

January 30 - Happy Birthday, Thomas Rolfe

Posted on January 30, 2021

This is an update of my January 30, 2010, post:

Who the heck was Thomas Rolfe?

Thomas Rolfe was born on this day in 1615 to a very famous mother: Pocahontas.

(Here is a portrait that is supposed to be a picture of Pocahontas and Thomas.)

At the time of her son's birth, Pocahontas was called Rebecca Rolfe, because she had converted to Christianity, taken an English “first” name, and married Englishman John Rolfe. Many people, including Native American people, say that Pocahontas was actually forced to marry Rolfe and was basically kidnapped when taken to England. I think it's likely she was forced to convert to Christianity, too.

I definitely did not realize, until doing research for this piece, that Pocahontas wasn't her real name. Her formal names were Matoaka and Amonute. I read two totally different accounts of the name Pocahontas: one source claimed that Pocahontas was a childhood nickname that meant something like “rambunctious," and another source claimed that Pocahontas was the name of Matoaka's mother and meant "laughing and joyous." Apparently Matoaka's mother died in childbirth, and her father was so grief-stricken that he bonded with his baby by using the name of the dearly departed. 

Pocahontas's father, Wahunsunacawh, was the paramount chief of the Powhatan people who lived in what is now Virginia near England's first successful colony, Jamestown.

Pocahontas is most famous for saving the life of colonist John Smith. But the incident may never have happened (we only know about it from Smith's retelling many years later), and even if it did happen, most references to the incident in popular culture are mythologized. For example, there is no evidence that Smith and Pocahontas fell in love—indeed, Smith wrote that she was only “tenne” (10) years old when she saved his life.

Whatever happened (or did not happen) in the Pocahontas-John Smith encounter, it is clear that this Powhatan princess befriended the English settlers in Jamestown and eventually, as mentioned, married one of them. In 1616 John Rolfe took his wife and son to London, where Pocahontas met King James and other society folk, interacted
 with John Smith (who had returned to England in 1609 after being injured in the New World), and sadly died at age 21, probably of a disease, just as the family was getting ready to return back to North America.

Pocahontas's son Thomas Rolfe grew up in England, and he married and had a daughter. Through this daughter, Anne Rolfe, Pocahontas and Thomas have descendants who live in England. In 1635 Thomas returned to the New World. There he remarried and had a second daughter, Jane Rolfe. Through this daughter, Pocahontas and Thomas have had many descendants in America, including two former first ladies, Edith Bolling Galt Wilson and Nancy Reagan.

National Geographic Kids has an interactive adventure about John Smith and Jamestown with lots of info and several mini-games.

Check out four very different portraits of Pocahontas:

Many people are most aware of Pocahontas because of the Disney animated movie. Of course, no one expects a Disney movie to be accurate history, but people who don't know better probably think that at least some of the broad strokes of the tale are true. However, they aren't.
She just doesn't look like a 10-year-old girl,
does she?

I ran across several items on the internet in which Native Americans complained about the inaccuracy and mythology of the Disney version of the Pocahontas story. Here's one,
and here is another.

January 29 - Happy Birthday, Lawrence Hargrave

Posted on January 29, 2021

This is an update of the post published on January 29, 2010:

Born in England in 1850, Lawrence Hargrave immigrated with his family to Australia. A teen when he arrived “down under,” Hargrave eagerly accepted positions on ships and thus helped explore Australia and nearby places.

He failed the test required to graduate from his school and instead became an engineering apprentice; as an engineer he continued to go on explo
ratory expeditions. Later he settled in Sydney and became an assistant astronomical observer at the Sydney Observatory.

When Hargrave's father died and Hargrave came into his inheritance, he resigned from the observatory position and gave the rest of his life to research work. He invented many devices but never applied for a patent on any of them. He did not need the money, but he also very much believed in the idea of scientists publishing their work for all humankind to elaborate on and benefit from.

Hargrave particularly worked on flying machines and made major contributions in knowledge about flight stability and the shape of wings and propeller blades. He also worked on the rotary engine, and his ideas were used by many early aircraft until around 1920.

Hargrave is most associated with box kites; this invention was used to experiment with lift and drag (he himself went on flights, lifted by his kites), and box kites were later used for weather measurements and were used as the basis for gliders and airplanes.

Hargrave was a very good experimenter and made beautiful models. He certainly contributed to the sum of human knowledge (his main goal) but was more widely respected for his contributions after his death than during his life.

Words of Wisdom

Hargrave said, “The flying machine of the future will not be born fully fledged and capable of a flight for 1000 miles or so. Like everything else it must be evolved gradually. The first difficulty is to get a thing that will fly at all. When this is made, a full description should be published as an aid to others.”

Hargrave might not have guessed at the shape
of aircraft of the future, but he did have a practical
view about how aircraft would evolve, each inventor
standing on the shoulders of those before them.

Wisdom Without Words

Hargrave was once asked to give a lecture, and he admitted that teaching and lecturing were not in his skill set. Indeed, he was known as a man of few words.

Still, Hargrave was too modest—he showed himself very capable of teaching when he spent afternoons working with kids to build and fly box kites. He also donated all of his models to museums, explaining that they were “knowledge without words.”

Celebrate Hargrave

  • Fly a kite.
Maybe even a box kite! Blue Sky Lark has a website with a picture of Hargrave's original design (box kites are 
also called “cellular kites”) and many other forms elaborated from his ideas.


  • Build a model. Local hobby shops and toy stores usually sell a variety of models to put together and paint. Or go online for help, such as this website.