Sound Space

August 2022 Science Snacks Newsletter

by Marianne Dyson

No one can hear you scream in space.

They can’t hear you laugh or cough or clap your hands, either.

Sound is defined as vibrations that travel through a gas, liquid, or solid (e.g. the floor of the apartment upstairs) that is heard when those vibrations “shake” the eardrum of a person or animal.

cell phone
Sound is a vibration that travels through a gas, liquid, or solid. Play a song or video on your cell phone and hold your finger near one of the speakers (look for the row of holes at the bottom shown in the photo) to feel the air vibrating. Marianne Dyson photo, 2022.

So despite the loud booms of spacecraft exploding in movies, explosions in space are silent. However, secondary sound effects may be heard. Debris striking a hull or window of a spacecraft might cause a vibration inside that generates sound. Astronauts onboard the space shuttle reported hearing loud bangs as the metal structure of the vehicle shook during jet firings. A spacewalker banging on the hatch could be heard by those inside. Would touching helmets together work? Probably not much, considering the thickness of the glass, but combined with lip reading, it might help!

But wait—people on the ground talk to astronauts in space all the time. How can they do that?

Radio waves are not sound waves. Radio is a band of electromagnetic waves of a frequency between 3 kilohertz to 300 gigahertz [NASA reference]. Radio, just like visible light and x-rays and other frequencies of electromagnetic waves, travels at the speed of light in a vacuum.

Humans cannot hear radio waves directly. (Human eyes “see” electromagnetic waves in the visible light 1015 Hz range.) But clever humans have learned how to convert the energy in a radio wave into vibrations that create sound waves that human and animal ears can sense.

Humans can generally hear sound waves between 12 Hz and 20 KHz. [Reference] Other animals such as dogs, cats, and especially bats can hear higher frequencies, and some, including whales, much lower frequencies than humans. [Reference]

The way an astronaut communicates with Mission Control is to speak into a microphone that converts the vibrations in the air made by her voice into radio waves. Those waves are (after being converted to the proper frequency and chopped into bits for transmission by a computer) sent through the vacuum of space, the atmosphere of Earth, and to a receiver on the ground that distributes the waves to the various devices that convert the radio waves back into sound such as flight controller headsets, someone’s cell phone, or amplified speaker boxes in school auditoriums. A response likewise is converted to radio and back into sounds that the astronaut hears in her headset or through a speaker in a spacecraft or spacesuit.

author wearing headset
Noise-canceling headsets (shown worn by the author) convert radio to sound while protecting the wearer from hearing loss. Frequent exposure to loud sounds (more than 60 min. above 60% volume/day) or to sounds greater than 165 decibels (a gunshot at close range), can cause permanent damage to the inner ear. [Reference] Marianne Dyson photo, 2022.

But even at the speed of light, it takes time for the signals to travel back and forth in space—so be prepared for a time lag between questions and answers. As I noted in a previous blog, this time lag almost caused us to hang up on an astronaut who called our house from space!

Because aircraft and spacecraft cockpits are noisy, some sounds, like “d” and “t” are hard to distinguish from each other, especially considering various accents. To avoid confusion, the aviation and space community employ an aviation alphabet to spell out each letter of a word. So instead of spelling out “dot” as “dee oh tee” which might sound like DoD or tot or even pot, in aviation/space speak, it is “Delta Oscar Tango.”

I hope your brain enjoyed this science snack. In case you didn’t hear, that’s Sierra November Alpha Charlie Kilo!

Writing and Speaking About Space

I’m happy to announce I have a short story, “The Power of Apollo (16)” and science article in the September/October 2022 issue of Analog Science Fiction and Fact Magazine (and my name is on the cover!). Single print copies can be found at bookstores and newsstands. Electronic subscriptions are available via Amazon.

Want to live in space? Listen to the Big Picture Science podcast (also broadcast on NPR Science Fridays), “Building a Space Colony.” I’m quoted during the first segment which is followed by a segment with Author Emily St. John Mandel and another with John Adams of Biosphere 2.

Texas friends: I hope to see you at FenCon in Dallas September 16-18, 2022. Stop by my autograph table to get signed copies of Shuttle Mission Control, Fly Me to the Moon, A Passion for Space, and my newest children’s title, Up in Space. Autographed books can also be ordered through Thank you for your support!

Blue Fire in Space

Marianne Dyson, October 2021

As the holiday season approaches, many of us decorate our tables with candles. If we did that in space, they would burn round and blue, not pointy and yellow. Why?

Candle flames heat the air around them. The hot air rises because it is less dense and thus weighs less than cold air. This air movement shapes a candle flame into a cone with a point at the top (see photo). Flames are blue at the base where they are hottest, and yellow above because as the hot air rises it takes some of the unburned wax with it in the form of smoke and soot.

Flames on Earth are cone shaped and blue at the base and yellow at the top because heated air rises. Marianne Dyson photo, 2021.

In space, hot and cold air weigh the same: nothing. Heated air just expands outward in a sphere. Because the air doesn

Space Tourism Takes Off

Marianne Dyson, June 2021

Space tourism is finally getting off the ground. For young people interested in STEM careers, the future is full of stars. And space tourism might lead to some cool jobs on the ground as well.

It has now been 20 years since Dennis Tito paid $20 million to the Russians to spend a week on the ISS. Six more wealthy fliers, including the first woman (Anousheh Ansari) bought flights through 2009. No

Apollo 11, a view from Summer Camp

Marianne Dyson, July 2019

I was a teenager at summer camp when Apollo 11 astronauts Neil Armstrong and Buzz Aldrin landed on the Moon 50 years ago this month. Below is the story of that day as recorded in my memoir.

Marianne and "Red" in 1969 at Rambling Acres. Photo courtesy Marianne Dyson

Marianne and “Red” in 1969 at Rambling Acres. Photo courtesy Marianne Dyson

Begin excerpt from A Passion for Space copyright Marianne Dyson–

July 20, 1969, Ohio

“Girls! Girls!” someone hollered from outside the big red barn. I was at Rambling Acres Horseback-Riding Camp, near Canton, Ohio. “Put your brooms away and come up to the house! They’ve landed on the Moon!”

I didn’t need a second invitation. I’d enthusiastically followed the space program since first grade when John Glenn had orbited the Earth. I was 14 now, and I loved space even more than horses. The previous spring, I’d even written and hand printed a 60-page book, “The Apollo Program” for my eighth-grade English class.

I dashed from the stall, latching the gate behind me, and ran up the dusty road to the camp owner’s house. “Wait up!” my best friend Chrisse hollered as she scampered up the road behind me, followed by the other girls.

The owner, Mrs. Noll, insisted we brush dust and straw off each other’s clothes and remove our dirty shoes before entering her house. Then we filed into her living room and settled down cross-legged on the carpet, facing the television set. The TV was a stand-alone piece of furniture, a box on legs about three feet tall with “rabbit ears” antenna. The picture was in black and white.

The familiar face of CBS News anchor Walter Cronkite appeared on the screen. In his deep voice, he explained that Mission Control in Houston had given Apollo 11 astronauts Neil Armstrong and Buzz Aldrin the “go” to exit their spacecraft. The men had been scheduled to sleep but were too keyed up after the exciting first landing on the Moon.

I was keyed up, too. It was the first day of camp, and I’d just met five new girls. We had plenty to talk about while we waited for the astronauts to leave the lunar lander. “Which one do you think is the cutest?” Sue asked me as we loaded our plates for dinner.

“It doesn’t matter,” I said, snatching a roll. “They’re married!”

Sue frowned and then sighed as she scooped beans onto her plate. “Wouldn’t it be dreamy to marry an astronaut?”

“Yeah,” I agreed. Then I added silently, “But even better if you could be one!”

We finished dinner, and the astronauts still hadn’t emerged from their ship. We wondered what they were having for dinner. (I found out later, bacon cubes. Yuk!) We trotted back to the barn for evening chores. I brushed the horse who shared my nickname, Red. Then we got our showers and returned to Mrs. Noll’s house.

The television spurted static-filled voices of the crew talking with Mission Control. What was taking so long? Why didn’t they just open the door and hop out? Bedtime came and went. Luckily, Mrs. Noll let us stay up for this historic occasion.

Finally, six hours after Apollo 11 landed, the ghostly black and white “live from the Moon” image flickered on the screen. At 10:39 p.m. Eastern time, Armstrong spoke the now-famous words, “That’s one small step for man, one giant leap for mankind,” as he stepped backwards off the ladder onto the lunar surface. I remember thinking how I’d like to follow in his footsteps.

But in 1969, there was no such thing as a female astronaut. No woman in my family had even gone to college. Yet, the previous winter, I’d written in my diary, “I wish very much to be able to be an astronaut. I’m sorry I’m a girl, but I’ll have to try harder then.”

As I gazed up at the half-full Moon that July night, I marveled that there were men up there looking back at me. If those men could walk on the Moon, then maybe a skinny red-headed girl from a small town in Ohio could find a way to go to college and one day work for NASA.

–End excerpt from A Passion for Space, copyright Marianne Dyson