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
Where am I? This was a cruel question for sailors before John Harrison.
In 1707 a fleet of British warships mistook their location and sailed onto the rocky Scilly Islands. Two thousand men drowned. The Royal Navy offered a prize of £20,000 (3 to 4 million dollars in today’s money) for anyone who could provide a way for ships to find their position.
North and south latitude wasn’t the problem. Tables gave the positions of the sun, moon and stars above or below the equator. Navigators could use a sextant (it measures angles between the ocean horizon and a celestial body) to find a ship’s position north or south. But the only way of knowing your position on the spinning earth, east or west, is to know what time it is, within seconds, at the Royal Observatory at Greenwich, England—0° longitude.
Sailors needed a seagoing clock!
Clocks in the 1700’s were slow or fast by several minutes a week. Not good enough. And they measured seconds with a pendulum, which wouldn’t work on a rocking, rolling ship.
John Harrison was a fine carpenter who became fascinated by accurate timekeeping. He built big clocks for houses, barns and churches. Bit by bit he made them more accurate. He set out to win the longitude prize.
He invented ways for a clock to compensate for temperature, so they wouldn’t run slower when it got warmer. He invented a nearly frictionless escapement (the mechanism that “counts” the tick-tocks with the clock’s hands). He overcame the pendulum problem with pivoted “dumbells” that rocked back and forth with springs.
Harrison worked for five years to construct the large and beautiful Sea Clock #1. In 1736 Harrison and his clock took a trip on HMS Centurion to Lisbon, Portugal, and back. Harrison was terribly seasick. His clock was not. It was a great success.
But the Royal Navy wouldn’t award the prize. It dithered for the next 37 years. Harrison worked on, making his sea clocks smaller and more accurate. In 1761 he sent his son William on a trial run with Sea Watch #1 to Jamaica and back. The smaller clock worked beautifully. The Navy kept dithering.
Not until Harrison was 80 years old was part of the prize awarded to him. He died three years later but he knew that he had changed the world, solving one of our most important, most perplexing problems: where are we?
An important part of Jan Adkins' considerable output is books of non-fiction for young people, his special audience. He also writes humor and feature articles for several magazines. He has illustrated most of his books and contributes illustrations to dozens of mainstream magazines, especially on marine and technical subjects. Have a look at his Wooden Ship: The Building of a Wooden Sailing Vessel in 1870, a chronicle of a fictional whale ship describing and illustrating the details of her building from design to launching.
Jan Adkins is 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. "Tick Tock: A Carpenter Solves an Ocean Riddle." Nonfiction Minute,
iNK Think Tank, 19 Mar. 2018, www.nonfictionminute.org/
“It is at these times you realize the blessing of a good, thick skirt,” said Mary Kingsley after she crashed into a cleverly concealed leopard pit lined with twelve-inch ivory spikes.
The year was 1895, the place Equatorial West Africa, and the spunky lady saved, thanks to her observance to the dress code of the day, was a young Englishwoman collecting species of fish and beetles for the British Museum.
Mary Kingsley was the daughter of a physician who spent most of his time traveling. Although she received no formal education (reserved for her brother Charles), Mary learned to read, becoming fascinated with subjects such as science, exploration and piracy.
At one point she was granted permission to teach herself German, but only after she could iron a shirt properly. Mary learned chemistry, experimented with gunpowder and electricity, and became engrossed by the intricacies of plumbing. After years of caring for her invalid mother, in 1892 both her parents died. With the small inheritance left to her came the fulfillment of a dream: to explore West Africa.
When Mary crashed into the leopard pit, she was traveling in what was then the French Congo, getting to know the Fangs, reportedly a tribe of cannibals. Traveling by canoe, she was once marooned in a crocodile-infested lagoon. When one tried to climb aboard, she was there with a paddle, ready to “fetch him a clip on the snout.”
After two trips, she wrote a book called Travels in West Africa. She became a sought-after lecturer and celebrity. In public appearances she was both funny and serious, peppering her narrative with jokes, often at her own expense, but also being critical of the way the British had steamrolled into the African continent, with little regard for its ancient cultures.
In 1900 she sailed to Africa for the third time, responding to an urgent call for nurses in South Africa, where war was underway. Assigned to a hospital where hundreds of soldiers were dying from a raging epidemic, she became ill herself, and died two months later. She was buried at sea with military honor.
In her book, she remembers: “Indeed, much as I have enjoyed life in Africa, I do not think I ever enjoyed it to the full as I did when dropping down the Rembwe… Ah me! Give me a West African river and a canoe for sheer pleasure.”
Rave reviews for Roxie Munro's book Market Maze:
"A great way to introduce kids to their foods' origins and to prepare them for a greenmarket visit of their own." Kirkus (Starred review!) excerpt.
"From a parent’s or teacher’s point of view, here’s a good way for kids to gain the visual discrimination skills needed for reading, while they learn about the sources of food at their local farmers’ markets. For kids, though, the combination of mazes and hidden objects is just plain fun. It’s a winning combination." Booklist review excerpt.
Roxie Munro is a member of iNK's Authors on Call so you can meet her face-to-race through interactive videoconferencing. Learn more about her programs here.
MLA 8 Citation
Munro, Roxie. "Mary Kingsley." Nonfiction Minute, iNK Think Tank, 15 Mar. 2018,