Original image
Library of Congress

15 Highlights from Carl Sagan's Archive

Original image
Library of Congress

Recently, the Library of Congress acquired and began to digitize The Seth MacFarlane Collection of the Carl Sagan and Ann Druyan Archive, a compilation of the personal papers, books, and correspondence of noted astrophysicist Carl Sagan. Through more than a dozen books, as well as his groundbreaking 1980 television series Cosmos: A Personal Voyage—soon to be remade in March featuring equally awesome astrophysicist Neil deGrasse Tyson—Sagan used his wondrous spirit to urge people to look at the planet and our place in the universe in different, dynamic ways. Here are a few awesome things we found in the collection.

1. Home Movies of a Young Sagan

The video above shows a series of silent home movies, starting off with the young Sagan joking around while playing piano. Other clips—with appearances by his mother Rachel, his father Samuel, and his younger sister Carol—show Sagan horseback riding, on vacation, and documenting a family trip to the zoo.

2. The Evolution of Interstellar Space Flight

This wonderful drawing was created by pre-teen Sagan, and is a collage of proposed newspaper headlines from the future. One headline boasts of technological developments like atomic space ships that can travel 5 miles per second, while another imagined advertisement promotes “Interstellar Spacelines," encouraging people to travel to and inhabit a planet in another solar system called "Altair 8."

3. Wawawhack, the Rahway High School student newspaper, Vol. VI, No. 5.

This issue of Wawawhack, the Rahway High School student newspaper, contains a student spotlight section describing Sagan's accomplishments as a high schooler. “If you wish to gain information concerning anything,” the article says, “go to Carl Sagan.” The short piece also describes his ambition to become an astronomer when he grows up, lists his hobbies as reading and playing basketball, labels his pet peeve as “lettuce sandwiches,” and names his favorite song—“My Foolish Heart, the title song from the film adaptation of the JD Salinger short story “Uncle Wiggly in Connecticut.”

4. The sounds of Earth

This is Sagan’s personal copy of the gold-plated copper record disc that NASA produced in 1977 to accompany the Voyager 1 & 2 spacecraft into interstellar space for potential alien civilizations to discover. The disc includes 115 images of Earth cultures, natural sounds, music, and spoken greetings in 55 languages. The phrase “To the makers of music—all worlds, all times” is etched around the center of both sides. Also found in the archive is a 1986 birthday greeting to Chuck Berry by Sagan and his eventual wife Ann Druyan (Berry’s song “Johnny B. Goode” was included on the record), and a thank-you letter to famed ethnomusicologist Alan Lomax for helping compile the music for the disc.

5. The Pale Blue Dot

Sagan dictated many of his science-related thoughts and much of his official correspondence. This 4-minute audio recording is the abstract for his 1994 book, Pale Blue Dot, and ponders the primary concepts gained from the famous “Pale Blue Dot” photo taken, at Sagan's request, more than 4 billion miles from earth by the Voyage 1 spacecraft in 1990. “Consider that dot,” said Sagan, “That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” The archive also includes the second of 20 drafts of Sagan’s book.

6. Diagram of all space and time

This diagram, drawn by Sagan in 1985, represents all of space and time. The X-axis illustrates past and future time, while the Y-axis illustrates scale from the minute size of electrons to the distance to the “M31” or Andromeda Galaxy. Note the relative size of the small box that represents the “Realm of Direct Human Experience” to the huge space given to the realms of Quantum Physics and Special Relativity, and also the ominously titled “Forbidden Zone.”

7. Jovian radio organisms

Throughout his later career, Sagan would keep a file composed of initial concepts for writing projects that piqued his interest that he called his “Ideas Riding” file—a play on the phrase “Ideas Writing.” In this one-page document, the astrophysicist contemplates the “very speculative idea” that large plantlike organisms on Jupiter could communicate using radio waves like “a vast sing-along or the noise leakage from an immense cocktail party.” Pretty trippy. Other documents from this file include everything from notes on the nature of the clouds on Venus to an observation about how whale songs sound like cello music to asking “why are clouds white?”

8. Briefing notes for President Carter and Vice President Walter Mondale

This handwritten note—on Watergate Hotel stationery—was used for a presentation by Sagan to brief then-President Jimmy Carter and Vice President Walter Mondale on concepts like the origin of life; the Voyager record; “cosmic catastrophes” like pulsars, quasars, and black holes; and CETI, or ”communication with extraterrestrial intelligence.”

9. Letter to Brown University Admissions Office

This college recommendation letter was written by Sagan and sent to the admissions office of Brown University, endorsing a student named David Grinspoon for admission to the school. Sagan declares that Grinspoon “would rank in the upper one percent of the students in my introductory astronomy course at Cornell,” and notes that the young student is an “accomplished tennis and guitar player.” Grinspoon would eventually attend Brown, and would even get a second recommendation letter from Sagan—also in the collection—when he was trying to get into graduate school at the University of Arizona. Additional correspondence between the two includes a letter Sagan wrote to the undergrad asking him to help him find an astronomy book written by sci-fi author H.P. Lovecraft.

10. Viking Lander images of the surface of Mars

These photographs are Sagan’s personal copies of the images sent back to earth from the Viking lander in 1977. Sagan was obsessed with the Red Planet, and the collection also includes a photo of Sagan with a model of the lander taken in Death Valley, California.

11. Idea for Contact video game

Sagan wasn’t content working in just literature, academia, or television. In this document, he chews over how to create a video game that could teach astronomy “in a context as exciting as most violent video games.” The premise of the video game would involve creating a young galactic civilization “in order to help it before it destroys itself—which most of them generally do.” Ever the optimist, Sagan also considered how the video game could be a tie-in to his novel Contact, which would be published in 1985. The collection also includes a dictated first draft of chapter three and a full draft of the novel.

12. Candidate list of Why? books

Sagan connected with so many people thanks to his knack for making audiences easily understand some pretty difficult scientific concepts. This list from later in his life contains about 150 potential titles for a series of instructional books for children called “Why?” Some examples include “How High is the Sky?”, “Why Don’t I Feel the Earth Spin?”, “If a Baby Was Raised by Mutes, What Language Would it Speak?”, “Could there be an Undiscovered Number Between 1 and 2?”, and “Why is it Warm in Summer?”

13. Scientists tithe time to science education

Anticipating the contemporary lack of funding and support for potentially costly scientific endeavors, Sagan proposed that scientists themselves should donate ten percent of their time towards public education in science. As a way for these scientists to contribute to a better public understanding of science, Sagan suggests they should write articles in local newspapers, give public lectures, and hold open houses at observatories.

14. Lecture notes

Though he was the most high profile astrophysicist of his time, Sagan was still a university professor with coursework, exams, and research papers to assign. The collection give us a little look into just what it might have been like to be enrolled in—or to teach—one of his classes.

One document for the “Astronomy 490” course he taught at Cornell in the '80s features lecture notes written by Sagan himself, which encourage students to push their critical thinking between “what feels good versus what is true,” and explains that the course will follow the logical idiom “Post hoc ergo propter hoc.” One of the course’s final exams features an essay question asking students to describe the ways culture may change in the years following a major event involving UFOs, while another asks students to create a thought experiment for or against sun sign astrology.

For his 1965 “Astronomy 170” course at Harvard, his lecture notes outline topics such as the possibility of life on Mars and his desire to spend class time contemplating Saturn’s rings.

15. Correspondence between Sagan and a young Neil deGrasse Tyson

Perhaps my favorite discovery in the collection is a series of correspondence between Sagan—who was at the height of his popularity—and a young Neil deGrasse Tyson, an astrophysicist who has now taken over Sagan’s mantle in bringing popular science to the masses.

The banter starts with a letter from Sagan to Tyson—who was a senior at The Bronx High School of Science at the time—inviting the young man to visit him at Cornell and praising his decision to major in physics. Following their meeting and some time later, Tyson responds to Sagan informing him he has decided to attend Harvard because they have a larger astronomy department, to which Sagan cheekily responds that he’s sure Tyson has “not made a serious error in going there rather than Cornell.”

The formal friendship gives way to casual communication when Tyson send Sagan a letter about his first year as an undergrad at Harvard, and how he sublet an apartment in Cambridge for the summer so he could work full time at the Center for Astrophysics until school started up again. The pièce de résistance is a letter Tyson sent Sagan asking him how he would go about finding a publisher for turning a series of Q&A articles he wrote into a full-length book. The message includes a newspaper clipping about Tyson to remind Sagan of his accomplishments. It also features Tyson wearing a particularly goofy, but great astronomy-themed t-shirt.

The digitized collection is only in the preliminary stages, and the entirety of the documents from Sagan’s estate numbers in the hundreds more. If you’re as much of a Sagan fan—or science geek—as I am, let’s hope they put them online sooner rather than later.

Can't get enough Sagan? Check out this awesome print in the mental_floss store!

Original image
iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
Original image
iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

Original image
Library of Congress
10 Facts About the Tomb of the Unknown Soldier
May 29, 2017
Original image
Library of Congress

On Veterans Day, 1921, President Warren G. Harding presided over an interment ceremony at Arlington National Cemetery for an unknown soldier who died during World War I. Since then, three more soldiers have been added to the Tomb of the Unknowns (also known as the Tomb of the Unknown Soldier) memorial—and one has been disinterred. Below, a few things you might not know about the historic site and the rituals that surround it.


Wikimedia Commons // Public Domain

To ensure a truly random selection, four unknown soldiers were exhumed from four different WWI American cemeteries in France. U.S. Army Sgt. Edward F. Younger, who was wounded in combat and received the Distinguished Service Medal, was chosen to select a soldier for burial at the Tomb of the Unknowns in Arlington. After the four identical caskets were lined up for his inspection, Younger chose the third casket from the left by placing a spray of white roses on it. The chosen soldier was transported to the U.S. on the USS Olympia, while the other three were reburied at Meuse Argonne American Cemetery in France.


One had served in the European Theater and the other served in the Pacific Theater. The Navy’s only active-duty Medal of Honor recipient, Hospitalman 1st Class William R. Charette, chose one of the identical caskets to go on to Arlington. The other was given a burial at sea.


WikimediaCommons // Public Domain

The soldiers were disinterred from the National Cemetery of the Pacific in Hawaii. This time, Army Master Sgt. Ned Lyle was the one to choose the casket. Along with the unknown soldier from WWII, the unknown Korean War soldier lay in the Capitol Rotunda from May 28 to May 30, 1958.


Medal of Honor recipient U.S. Marine Corps Sgt. Maj. Allan Jay Kellogg, Jr., selected the Vietnam War representative during a ceremony at Pearl Harbor.


Wikipedia // Public Domain

Thanks to advances in mitochondrial DNA testing, scientists were eventually able to identify the remains of the Vietnam War soldier. On May 14, 1998, the remains were exhumed and tested, revealing the “unknown” soldier to be Air Force 1st Lt. Michael Joseph Blassie (pictured). Blassie was shot down near An Loc, Vietnam, in 1972. After his identification, Blassie’s family had him moved to Jefferson Barracks National Cemetery in St. Louis. Instead of adding another unknown soldier to the Vietnam War crypt, the crypt cover has been replaced with one bearing the inscription, “Honoring and Keeping Faith with America’s Missing Servicemen, 1958-1975.”


The Tomb was designed by architect Lorimer Rich and sculptor Thomas Hudson Jones, but the actual carving was done by the Piccirilli Brothers. Even if you don’t know them, you know their work: The brothers carved the 19-foot statue of Abraham Lincoln for the Lincoln Memorial, the lions outside of the New York Public Library, the Maine Monument in Central Park, the DuPont Circle Fountain in D.C., and much more.


Tomb Guards come from the 3rd U.S. Infantry Regiment "The Old Guard". Serving the U.S. since 1784, the Old Guard is the oldest active infantry unit in the military. They keep watch over the memorial every minute of every day, including when the cemetery is closed and in inclement weather.


Members of the Old Guard must apply for the position. If chosen, the applicant goes through an intense training period, in which they must pass tests on weapons, ceremonial steps, cadence, military bearing, uniform preparation, and orders. Although military members are known for their neat uniforms, it’s said that the Tomb Guards have the highest standards of them all. A knowledge test quizzes applicants on their memorization—including punctuation—of 35 pages on the history of the Tomb. Once they’re selected, Guards “walk the mat” in front of the Tomb for anywhere from 30 minutes to two hours, depending on the time of year and time of day. They work in 24-hour shifts, however, and when they aren’t walking the mat, they’re in the living quarters beneath it. This gives the sentinels time to complete training and prepare their uniforms, which can take up to eight hours.


The Tomb Guard badge is the least awarded badge in the Army, and the second least awarded badge in the overall military. (The first is the astronaut badge.) Tomb Guards are held to the highest standards of behavior, and can have their badge taken away for any action on or off duty that could bring disrespect to the Tomb. And that’s for the entire lifetime of the Tomb Guard, even well after his or her guarding duty is over. For the record, it seems that Tomb Guards are rarely female—only three women have held the post.


Everything the guards do is a series of 21, which alludes to the 21-gun salute. According to

The Sentinel does not execute an about face, rather they stop on the 21st step, then turn and face the Tomb for 21 seconds. They then turn to face back down the mat, change the weapon to the outside shoulder, mentally count off 21 seconds, then step off for another 21 step walk down the mat. They face the Tomb at each end of the 21 step walk for 21 seconds. The Sentinel then repeats this over and over until the Guard Change ceremony begins.