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.
Stories that Surprise and Inspire
When musicians play a lively tune, they often find themselves spontaneously tapping their toes and moving about to the pulsing beat. But when Ellen Ochoa played her flute at work one day in 1993, she couldn’t be spontaneous at all. If she hadn’t made careful plans, she could have been blown about the room, just by playing one long note on her flute. That’s because she was an astronaut working on the U.S. Space Shuttle as it circled Earth more than a hundred miles out in space.
Gravity is so weak far out in space that astronauts—and any of their gear that isn’t fastened down—will float about inside a space craft. Blowing air into her flute could have created enough force to actually send Ochoa zipping about the space shuttle cabin. So, to keep herself in place as she played, she had to slip her feet into strong loops attached to the floor.
Dr. Ochoa, now the director of NASA’s Johnson Space Center, was the first U.S. astronaut to bring a flute on a space mission, but she wasn’t the first to make music in space. Nearly thirty years earlier, in December 1965, two astronauts onboard the Gemini 6 space craft played a musical joke on mission control officials down on Earth. Those astronauts—Walter M. Schirra, Jr., and Thomas P. Stafford—told mission control that they saw an unusual object near their spaceship, a satellite perhaps, moving from North to South. They said they would try to pick up some sound from this mysterious object. Then they used the harmonica and bells they had secretly brought with them on that December mission to surprise folks listening down below by playing “Jingle Bells.”
In recent years, other astronauts have brought musical instruments on space missions to help lift their spirits, especially those who spend many months on the International Space Station. Like Dr. Ochoa, these astronaut musicians have to make adjustments, such as using a bungee cord to attach an electronic piano keyboard to a pianist’s leg.
Some astronauts have composed music in space, including Canadian Chris Hadfield. On May 6, 2013, he sang the song he wrote—called “I.S.S. (Is Somebody Singing)”—in a live TV broadcast from the space station as thousands of Canadian schoolchildren sang along with him down on Earth. Click here for a recording of that space-to-Earth performance
Learning to play an instrument can be fun and, at times, frustrating. Amy Nathan's lively book helps young people cope with the difficulties involved in learning a new instrument and remaining dedicated to playing and practicing. Teens from renowned music programs - including the Juilliard School's Pre-College Program and Boston University's Tanglewood Institute - join pro musicians in offering practical answers to questions from what instrument to play to where the musical road may lead. For more information, click here.
MLA 8 Citation
Nathan, Amy. "Music That's Out of This World." Nonfiction Minute, iNK Think
Tank, 11 May 2018, www.nonfictionminute.org/the-nonfiction-minute/
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,