by David M. Schwartz
the amazing, engaging, math exponent
A light year is not a year that has gone on a diet. It is not a year that’s been trimmed to 300 days. It’s not a year spent under high-wattage lamps. A light year isn’t any kind of year.
A light year is a distance. It is a vast distance; the distance light travels in a year. To appreciate a light year, you have to understand how fast light travels.
The speed of light is truly mind-boggling: 186,000 miles per . . . second. That’s “per second,” not “per hour.” In one tick-tock second, light travels a distance of 186,000 miles. If it could go in circles, it could travel around the earth more than seven times in just one second! But light travels in straight lines, not in circles. Imagine something traveling that fast in a straight line—not for a second, not for a minute, not for an hour, not for a day, but for an entire year. The distance it goes in that year is called a light year.
A light year is a convenient unit of measure when distances are enormous. You could talk about the same distances in miles. It's about 5,878,499,810,000 (5 trillion, 878 billion, 499 million, 810 thousand ) of them. But these measurements are so large that they are unwieldy. It's much easier to just name that enormous distance with two simple words: a "light year."
The star closest to our solar system is Proxima Centauri. Some of the light that leaves Proxima Centauri goes to Earth, cruising along at 186,000 miles per second. At that speed, light takes about 4.2 years to get to Earth from Proxima Centauri So how far away is Proxima Centauri? It is 4.2 light years away.
To give you an idea of how far that is, imagine going to Proxima Centauri in a spaceship traveling at the speed of the space shuttle — about ten miles per second. (That’s much faster than airplanes can fly.) You would get there in about 70,000 years.
Our Sun is much closer than Proxima Centauri. It is 93 million miles away. There is another way to refer to the distance from the earth to the Sun. Light leaving the Sun takes about eight minutes to get to Earth, so we say the Sun is eight “light minutes” away. If you traveled at the speed of light, you could get there in eight minutes. Have a nice trip!
© David M. Schwartz, 2014
David Schwartz has been fascinated by big numbers and big distances ever since he was a little boy riding his bicycle, wondering “How long would it take for me to ride to Proxima Centauri, 4.2 light years away?” He wrote about light years in his math alphabet book G Is for Googol.
David is a member of iNK’s Authors on Call. He can visit in your classroom via interactive video conferencing. Learn more here.
MLA 8 Citation
Schwartz, David M. "What Is a Light Year?" Nonfiction Minute, iNK Think Tank, 14 Sept. 2017, www.nonfictionminute.org/the-nonfiction-minute/what-is-a-light-year.
Do you ever feel spaced-out before you take a test? Yes or no, let’s go!
1. TRUE or FALSE?
It’s possible for a spacecraft to fly from Earth to Venus, to Mars, back to Earth, then to Saturn, out to Pluto, back to Jupiter, and come home to Earth on one tank of fuel.
2. It’s possible for a spacecraft to fly all over the solar system on one tank of fuel because of:
a. the sling-shot effect
b. gravity assist
d. all of the above
e. none of the above
The sling-shot effect, also known as a swing-by or gravity assist, is used to accelerate a spacecraft. Acceleration means to change the speed and/or the direction of a moving body. A spacecraft that is speeding up, slowing down, or following a curved path is accelerating.
Gravity accelerates objects everywhere in the Universe. When you ride your bike up a hill it takes a lot of effort to make it to the top because the Earth is massive compared to you, and gravity pulls you toward its center. When you coast down the other side, gravity is your friend!
Spacecraft can use the gravity of a planet to accelerate. Picture a spacecraft falling toward a planet. The spacecraft will crash unless it steers away.
3. As a spacecraft accelerates toward a planet, the motion of the planet is also affected by the gravity exerted by:
a. the spacecraft
b. the Sun
c. cosmic rays
d. both (a) and (b)
e. both (b) and (c)
f. all of the above
g. none of the above
All bodies in space, no matter how big or small, exert gravity on each other. Planets stay in orbit around the sun because of gravity. A planet is also affected by the tiny mass of a spacecraft. Gravity assist was used to increase the speed of Voyager 1 by 36,000 mph on its swing by Jupiter, which sling shot it to Saturn. And Jupiter slowed down infinitesimally, at a rate of 12 inches per one trillion years.
4. The person who discovered the math for using gravity assist to accelerate a spacecraft from planet to planet to planet…was:
a. Aristotle (384 B.C. to 322 B.C)
b. Galileo (1564-1642)
c. Sir Isaac Newton (1643-1727)
d. Katherine Johnson (1918- )
e. Michael Minovitch (1936- )
END OF TEST!
DON’T STOP WORKING.
GO TO THE LIBRARY TO FIND THE ANSWERS.
In this drawing a spacecraft gets an assist from Jupiter as it "slingshots" toward Saturn. Image courtesy of NASA/JPL
Voyager 1 and Voyager 2 used gravity assist to fly by the outer planets. Image courtesy of NASA
The twin Voyagers have no people on board on their interstellar journey, but carry The Golden Record, which contains messages, music, and pictures from Earth. Image courtesy of NASA/Alexandra Siy
In case you didn't make it to the library: In 1961, UCLA graduate student Michael Minovitch used math and the new IBM 7090-7094 computers to invent gravity assist trajectories for space flight. Used with permission of Michael Minovitch
Alexandra Siy's Voyager's Greatest Hits tells the story of the twin space probes that traveled to Jupiter, Saturn, Uranus, and Neptune, a journey beyond our solar system into interstellar space, where no probe has ventured before. Siy tells the fascinating story of how the Voyager probes work, where the probes have been and what they’ve seen, and what they carry on board.
Alexandra Siy is also a member of Authors on Call. You can bring her to your classroom via interactive videoconferencing and learn more from her and ask her questions. To find out more go here.
MLA 8 Citation
Siy, Alexandra. "Spaced Out." Nonfiction Minute, iNK Think Tank, 2 May 2018,
The Explainer General
Most disasters are a cascade: small failures and minor circumstances, one leading to another, blossom into a cataclysm. On January 16, 1919, a cascade of tremendous size was poised above Boston’s North End.
The weather was one factor: unusually warm for winter.
Purity Distilling Company fermented and distilled molasses to make rum and alcohol. The 18th Amendment to the United States Constitution, prohibiting sales of alcoholic beverages, was due to be passed the very next day. This may have prompted Purity to collect as much molasses as possible.
The enormous tank holding the molasses was about 50 feet tall and 90 feet in diameter, holding 2,300,000 gallons. It was poorly built of thin steel painted brown to hide its leaks. Local families often collected some of the dripping molasses to sweeten their food. The unseasonably warm temperature quickly rose from 2° F (-16.7° C) to 40° F (4.4° C), expanding the liquid, and natural fermentation produced CO2 increasing tank pressure.
Just after noon, North End families felt the ground shake and heard a sound like a machine gun— the tank’s rivets popping out. The big tank exploded, sending a 25-foot wall of molasses roaring down the hill toward Commercial Street at about 35 miles an hour. In front of the molasses went a blast of air that blew some folks off their porches and tumbled others along the street like rag dolls. Homes and buildings were destroyed, smashed from their foundations. Horses pulling wagons were swept away. The steel girders of the Boston Elevated Railway were buckled, knocking a rail-car off the tracks.
Twenty-one people were killed and more than a hundred were injured. Many were saved by Massachusetts Maritime Academy cadets who rushed off their docked training vessel and plunged into the brown goo to rescue people. It’s difficult to know how many dogs, cats and horses died.
As you can imagine, the clean-up was awful. Firehoses from hydrants and harbor fireboats washed away as much as possible. Boston Harbor was brown for months. Sightseers tracked the goo back to homes, into hotels, onto pay-phones and onto doorknobs. Everything Bostonians touched was sticky for months.
Some say that on a hot summer day along the North End’s docks, the sickly sweet smell of molasses lingers. Bostonians can smile at the Great Molasses Flood now, but in January of 1919, that cascade of disasters was deadly serious.
Jan Adkins is an author, an illustrator, and a superb storyteller. Read about him on his Amazon page. He is also a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.
MLA 8 Citation
Adkins, Jan. "The Great Boston Molasses Flood: How Can a Tragedy Sound Funny?"
Nonfiction Minute, iNK Think Tank, 19 Jan. 2018,
Celebrating the History of Science
and the Science behind History
During the Renaissance, French kings and queens built many palaces, in an area known as the Loire Valley. The royal family would travel from palace to palace to get away from Paris, the way you might head to a lake house. The Loire Valley is not very close to Paris. It’s about 110 miles from Paris to the palace of Chambord, for instance. I wondered how long it took sixteenth century travelers to make this journey—and why there were so many palaces.
First, the distance. Under the best of conditions (good roads, decent weather, level ground), humans can walk four miles per hour over long distances. Horses can’t do much better–maybe five mph—but a lot less if they’re pulling something or if roads are in awful condition. A horse can canter at 20 mph, but it can only do that for six to eight miles at a time, after which it will slow down and walk, or stop completely. So it would have taken a long time to get from place to place. Under the best conditions, a journey from Paris to Chambord would have taken three weeks.
But in fact, it took a lot longer than that. Because in the sixteenth century, the royal court didn’t just hop on a horse and head to their country home. They took everything and everyone with them, loading all the stuff onto the backs of horses and mules.
When Catherine de Medici was queen of France, she traveled with her ladies and gentlemen, foreign ambassadors, pet bears, servants, retainers, attendants, apothecaries, astrologists, tutors, musicians, cooking pots, food, clothing, portable triumphal arches, wall hangings, and furniture.
And the reason there were so many palaces is simply that the court in Renaissance times –thousands of people–had to move around from estate to estate so as to find new hunting grounds. Once they’d exhausted the food supply in the area, they moved on to the next estate. Also, the sanitation was dreadful. After thousands of people had taken up residence in and around a great estate for a few weeks, filth piled up, and with it, stench and disease.
The royal procession could be miles long. When Catherine de Medici’s court packed up and left for a new palace, the beginning of the royal caravan sometimes entered a town before those traveling at the back of it had left the last one.
Sara Albee's recent book is Why'd They Wear That?, published by National Geographic in 2015. Get ready to chuckle your way through centuries of fashion dos and don'ts! In this humorous and approachable narrative, you will learn about outrageous, politically-perilous, funky, disgusting, regrettable, and life-threatening creations people have worn throughout the course of human history, all the way up to the present day. For more information, click here.
MLA 8 Citation
Albee, Sarah. "Renaissance Road Trips." Nonfiction Minute, iNK Think Tank, www.nonfictionminute.org/the-nonfiction-minute/renaissance-road-trips.