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When your slice of bread falls on the floor, everyone anxiously looks to see if it landed jelly side up or jelly side down. Simple probability gives a 50-50 chance either way, but it seems more correlated to the difficulty of cleaning that particular section of flooring.

On space station the probabilities are still the same, but the results are different. I fumbled my bread after spreading a generous layer of my favorite concoction, peanut butter and honey. It sped toward the overhead panel and hit it before I could intervene. Fortunately, it landed jelly side out (it’s interesting how many figures of speech have gravity-oriented references), so the 50-50 odds were in my favor this time. Unfortunately, it ricocheted and sped off in a different direction. I noticed that the angle of incidence equaled the angle of reflection. My earth-honed intuition anticipated a different motion, so I was not able to keep up with the errant slice. Like a real-life version of the game “asteroids,” it went on to hit a second panel. Jelly side was out again, so the 50-50 statistics were still in my favor. One more time my hand was lagging the trajectory. Like failing to flip heads three times in a row, the third collision was jelly side in, which immediately halted all motion. And just like on Earth, the outcome seemed related to the difficulty of cleaning the landing zone. After having hit two easy-to-clean aluminum panels, it landed on a white fabric covering on a patch of Velcro pile.

The fatalist in me accepts the inevitable Zero-G result of landing jelly side “down,” so I decided to make sure the probability would always be 100%. Realizing that the bread is merely a vehicle for conveying peanut butter and honey, I decided to spread it on both sides. In weightlessness, it’s easy to balance your slice on its edge so that it can be parked on the galley table without any fuss. And the result is pure tastebud heaven. I do it this way because I am in space, and I can.

On space station, we have a closet module. Its prosaic name is PMM, an acronym that has metamorphosed beyond the original assemblage of words to become a noun on its own, pronounced pee-em-em (only at NASA can we create new words without vowels). In a former life, it was an MPLM (another vowel-less word), a special transport container that flew up and down to space station in the back of the Space Shuttle. Made in Italy for NASA, the PMM was formally christened Leonardo—obviously named after a Teenage Mutant Ninja Turtle.

Me among the bags.

On my STS-126 Shuttle flight, I had the pleasure of moving Leonardo from the Shuttle payload bay and berthing it to the nadir hatchway on the station’s Node 2, using the Canadian robotic arm. Operating the Canada arm is a bit like working with a fancy backhoe, and requires its own skills. Once the module was berthed, we opened the hatch and unloaded many tons of much-needed equipment and supplies over the next 12 days.

For its return voyage, we loaded it up with garbage and trash. Included in the trash were bags of urine left over from human physiological experiments. These weren’t ordinary bags of urine; these were eight-month-old bags of urine. I did not need to read the label—my nose could identify the contents. We brought garbage-laden Leonardo home, but due to bad weather at the Cape, we landed at Edwards in California. It took another week before the Shuttle was transported home, and another week after that before Leonardo was removed from the payload bay and placed in its holding fixture. That was followed by the Christmas holiday. By the time folks got around to opening Leonardo, it had been sitting for well over a month, and some of the bags had leaked all over the inside of the module. I happened to be at the Cape the day after the technicians opened the hatch. It was not a pretty sight. I felt partly responsible, since I had been the one who did the orbital packing. I offered, but the technicians would not let me help clean up the mess.

In orbit, the Leonardo module is for me a special place. It is cool, quiet, soothing—a good place to reflect and recharge. But like most closets on Earth, the PMM is a total mess. The crew is so busy maintaining and utilizing space station that no one has time to properly arrange things, despite our good intentions. A typical clutter-creating scenario might go like this: Say you are in the middle of working on the station’s control system. Swapping out motherboards is a delicate task, akin to doing computer brain surgery. If you bend a pin while inserting a card, you can fry the whole works, and there are precious few spare parts. In the midst of this intensity your stomach starts rumbling, with the associated low blood sugar shakes. Your watch shows that you have been at this for hours without a break. So you fly over to Node 1 and dive into the module where the primary stocks are located, only to find that the pantry is down to vegetables and tofudibeast. You need meat and potatoes to keep going, so you float over to the PMM and pull out a new “meats in pouches” package. At the galley, you cut open a meat pouch, only to have a big bloop of gravy squirt out and make a mess. Reaching for the wipes, you discover that the last one had been dispensed to clean up the previous gravy squirt. Flying to PMA 1 (the connecting tunnel between the U.S. and Russian segments), where the hygiene supplies are kept, you find that the staging bag for dry wipes is empty.  Once again you dive into the PMM, searching for the mother lode of dry wipes. You refill the PMA 1 staging bag, and clean up your mess.

All of these packages have a nine-digit bar code. We are required to log these in our inventory management system, but often the bar code reader does not work. For this case of 20 dry wipe packages and a meats-in-pouches package, you have to write down 189 alpha-numeric characters (without a mistake).  These numbers must later be typed up in a crew note or called down to mission control.  So you think, “I will do all this inventory paperwork later.”

That’s how the PMM gets to be a mess.

When spare moments present themselves, I will go into the PMM and straighten up the clutter. Floating among the bags undulating on their anchor chords, I have the sensation of scuba diving in a kelp bed thicket. Then I catch up on the inventory paperwork. With luck, I’m able to scribble down all those nine-digit bar code numbers correctly.

Editor’s Note: Don Pettit demonstrates some weird physics onboard the space station for the Physics Central educational site.

The International Space Station was bought and paid for by a large group of nations. Now, with construction complete, we can focus on how best to use it.

We have built a laboratory located on the premier frontier of our era. Our Earth-honed intuition no longer applies in this orbital environment. On frontiers, things do not behave the way we think they should, and our preconceived notions are altered by observations. That makes it rich in potential for discovery. The answers are not in the back of the book, and sometimes even the questions themselves may not be known.

On the Station we can use reduced gravity as an experimental variable for long periods of time. We have access to high vacuum, at enormous pumping rates. (The rate at which space can suck away gas, hence its ability to provide a region devoid of molecules, far outpaces anything we can do on Earth.) We are beyond the majority of our atmosphere, which lets us touch the near-space environment where solar wind, cosmic rays, and atomic oxygen abound. Such cosmic detritus, unavailable for study within our atmosphere, holds some answers to the construction of our universe and how our small planet fits into the picture.

Here I am holding a glove from the Microgravity Science Glovebox, inside the Station's Columbus lab module.

The Station as a laboratory offers most of the features that Earth-borne laboratories have, including a good selection of experimental equipment, supplies, and a well-characterized environment (temperature, pressure, humidity, gas composition, etc.). There is generous electric power, high data-rate communications, significant crew work hours (the fraction of hours spent on science per crew day on Space Station is commensurate with the fraction for other science frontiers such as Antarctica and the deep ocean), and extended observational periods ranging from weeks to years. All this is conducted with a healthy blend of robots and humans, working together hand-in-end-effector, each contributing what each does best. Only on Earth is there a perceived friction between robots and humans.

In this orbital laboratory, we can iterate experimental procedures. We can try something, fail, go back to our chalk board, think, (we now have the time for this luxury) and try it all over again. We can iterate on the iteration. We now have continuous human presence, and time to see the unexpected and act upon it in unplanned ways. Sometimes these odd observations become the basis for studies totally different from those originally planned; sometimes those studies prove to be more valuable. And on this frontier the questions and answers mold each other in Yin-Yang fashion until reaching a natural endpoint or the funding runs out, whichever comes first. This is science at its best, and now, for the first time, we have a laboratory in space that allows us to do research in a way comparable to how we do it on Earth.

So what questions are ripe for study on the Station? What possible areas of research might bear fruit? We have a few ideas.

One area is the study of life on Earth. Life has survived for billions of years, during which temperatures, pressures, chemical potentials, radiation, and other factors have varied widely. Life always adapts and (mostly) survives. Yet there is one parameter that has remained constant for billions of years, as if our planet was the most tender of incubators. Now for the first time in the evolution of life, we humans can systematically tweak the gravity knob and probe its effect on living creatures. And we can change the magnitude of gravity by a factor of one million. Try changing other life-giving parameters, perhaps temperature, by a factor of one million and see how long it takes a hapless life form to shrivel up and die! The fact that gravity can be changed by many orders of magnitude and life can continue is, in itself, an amazing discovery. So now we have a laboratory to probe in-depth the effects of microgravity on living organisms.

The discovery of fire (or rather its harnessing) was a significant advance that allowed humans to transcend what we were to become what we are now. Well before Galileo and Newton dissected the basic formulations of gravity, humans intuitively understood that heat rises. We empirically learned how to fan the flames. But fire as we know it on Earth requires gravity. Without gravity-driven convection, it will consume its local supply of oxygen and snuff itself out as effectively as if smothered by a fire extinguisher. Questions about fire (up here we prefer the term “combustion”) are ripe for a place where we can tinker with the gravity knob.

Another invention, the wheel, literally carried us into the Industrial Age. Ironically, that particular tool is rendered obsolete on a frontier where one can move the heaviest of burdens with a small push of the fingertips. In space the problem is not how to move an object, but how to make it stay put. Perhaps the invention of the bungee cord and Velcro will be the space-equivalent to the development of the wheel on Earth. Such shifts in thought and perspective, some seemingly minor, happen when you observe the commonplace in a new and unfamiliar setting.

We are now told that we may only be seeing about 4 percent of the stuff that our universe is made of (which raises the question, what is the other 96 percent?). Some questions about fundamental physics can only be made outside our atmosphere or away from the effects of gravity. The International Space Station, contaminated with human-induced vibrations, may not be the ideal platform for these observations, but it is currently in orbit and is available to be used. Many of these experiments are like remora fish, latching onto an opportune shark for a sure ride instead of waiting for the ideal shark to swim by. And we pesky humans, even though we cause vibration, occasionally come in handy when some unexpected problem requires a tweak, a wrench, or simply a swift kick.

Although we have preconceived ideas about how the International Space Station can be utilized, benefits of an unquantifiable nature will slowly emerge and probably will be recognized only in hindsight. The Station offers us perspective; it allows us to question how humans behave on this planet in ways that you can’t when you live there.

Looking through the cupola windows on Space Station, it’s only natural to reflect upon who we are and where we fit into the world below. Like something out of Alice in Wonderland, this orbital looking glass can be both a window through which to observe the jeweled sphere of Earth and a mirror that (sometimes, depending on your viewing angle) shows you a translucent reflection of yourself superimposed on the planet.

City lights over Belgium and the Netherlands

From orbit, the more you know about our planet, the more you can see. You see all the geological features described in textbooks. You see fault zones, moraines, basins, ranges, impact craters, dikes, sills, braided channels, the strike and dip of layered rocks, folding, meanders, oxbow lakes, slumps, slides, mud flows, deltas, alluvial fans, glaciers, karst topography, cirques, tectonic plates, rifts zones, cinder cones, crater lakes, fossil sea shores, lava flows, volcanic plumes, fissures, eruptions, dry lakes, inverted topography, latteric soils, and many more.

You see clouds of every description and combination: nimbus, cumulus, stratus, nimbo-cumulus, nimbo-stratus, cirrus, thunderheads, and typhoons, sometimes with clockwise rotation, sometimes with counter-clockwise. You notice patterns: clouds over cold oceans look different than clouds over warm oceans. Sometimes the continents are all cloud-covered, so you have no recognizable landmass to help you gauge where you are. If you see a crisscross of jet contrails glistening in the sun above the clouds, you know you are over the United States.

Lightning storms flash like gigantic fireflies looking for mates half a continent away. You see patterns on the ocean surface, swirls and vortices on large scales, wave diffraction patterns around capes, solitary waves forming long lines out in the middle of nowhere, and rivers that look like they are spilling milk chocolate into turquoise oceans.

You see light-scattering phenomena of all kinds—at sunrise, at sunset, across the terminator, 16 times a day. You see crepuscular rays, forward reddened lobes, off-axis blue lobes, and corona halos. With binoculars you can count six distinct layers in the atmosphere, with the outer one seemingly fading into fuzzy blackness.

The aurora is nothing short of occipital ecstasy. It is always moving, always changing, and like snowflakes, no two displays are the same. The glowing red and green forms meander like celestial amoebas crawling across some great petri dish. One time our orbit took us through the center of an auroral display. It was as if we were in a glowing fog of red and green. Had we been shrunk down and inserted into the tube of a neon sign? It looked like it was just on the other side of the windowpane. I wanted to reach out and touch, but of course I couldn’t. Afterwards, I had to clean nose prints off of the window.

André looking out the Cupola windows

You catch an occasional meteor while looking down at Earth. You see stars and planets in oblique views, next to Earth’s limb. And they do not twinkle. Perchance you might spot a ragged shadow from a total solar eclipse projected onto Earth. Amazing, it looks just like it does in the textbooks! You have a godlike view of the finer details of shadowy projections onto spherical bodies. You see space junk orbiting nearby. Sometimes it flickers due to an irregularity, catching light as it rotates. An overboard water dump produces a virtual blizzard in the surrounding vacuum. Like strangers passing in the night, you see other satellites flash brilliantly for a few seconds, then fade into oblivion.

Jungles are the darkest land features you can observe in full sunlight. They are so dark that you need to open your camera lens to obtain a proper exposure. If there are clouds partly shrouding your view, you can be fooled into thinking you are over the ocean. Only when you notice rivers with braided channels and meandering loops of chocolate brown do you realize that it is jungle and not water. Farmland, rich with vibrant crops, is different. Farmland is bright, much brighter than the jungles. Here nature is giving us a clue as to the efficiency of light capture by plants.

The impact of humanity on Earth is humbling from orbit. Our greatest cities appear to the bare eye as minor gray smudges on the edges of continents—they could be the fingerprints of Atlas, from the last time he handled the globe. They are hardly distinguishable from volcanic ash flow or other geologic features. If you didn’t know it was a city, it would be difficult to conclude it was the result of human design. Under the scrutiny of the telephoto lens, things appear different. Like ants moving crumbs of dirt, we are slowly changing our world. You realize that Earth will do just fine, with or without us. We are wedded to this planet, for better or for worse, until mass extinction do us part.

Cities at night are different from their drab daytime counterparts. They present a most spectacular display that rivals a Broadway marquee. And cities around the world are different. Some show blue-green, while others show yellow-orange. Some have rectangular grids, while others look like a fractal-snapshot from Mandelbrot space.

Patterns in the countryside are different in Europe, North America, and South America. In space, you can see political boundaries that show up only at night. As if a beacon for humanity, Las Vegas is truly the brightest spot on Earth. Cities at night may very well be the most beautiful unintentional consequence of human activity.

This looking glass incites your mind to ponder the abstract. Through the window, you explore the world. In the mirror, you reflect upon your place within it and the reasons we explore. Is it fundamentally about finding new places to live and new resources to use? Or is it about expanding our knowledge of the universe? Either way, exploration seems fundamental to our survival as a species. After all, if the dinosaurs had explored space and colonized other planets, they would still be alive today.

Jim Voss shaves onboard the station in 2001.

I have never been able to shave with a safety razor without slicing my face, so I use a rotary electric razor instead. In weightlessness they work just as well, and the whiskers are captured inside the shaving head. But how does one clean out the whiskers in weightlessness? On Earth, you simply open the head and shake them out. Doing that up here would be a disaster. So once a week, when vacuuming the accumulation of lint, dust, and detritus against the air inlet filters, I vacuum my razor. I hold the vacuum cleaner hose between my legs, and use both hands to carefully open the shaving head in front of the suction. A cloud of whiskers jumps out, appearing like a miniature asteroid field, then quickly disappears into a black hole, with no chance of escape.

Kyrgyzstan is wedged in the mountainous wrinkles between Kazakhstan and China, created long ago when the land mass we now call India, propelled by plate tectonics, slammed into the Asian plate. Living there are a proud people with a rich history, surrounded by natural, high-altitude beauty.

Out of numerous Kyrgyz lakes, one in particular stands out—Lake Issyk Kul. When seen from orbit, Issyk Kul appears to be a giant eye, looking at us looking down at it. The snow-covered mountains become aged eyebrows. The lake itself, having a fairly high salt concentration, does not typically freeze over, thus reflecting wintertime light in such a way as to form a “pupil” that seems to track us as we orbit overhead.

In the Quest airlock, helping John Herrington suit up in November 2002.

A vacuum is a condition that is nearly devoid of molecules, and space is a molecular desert that makes the Empty Quarter of the Saudi Arabian peninsula seem like an oasis in comparison. But the space vacuum still has some molecules—residue from galactic processes, solar wind or atomic detritus spalled off from our atmosphere. And molecules, typically floating in the surrounding air, can be sensed via smell.

To talk about the smell of space makes no sense at all. Even if we had space-adapted noses, there is no air to transport the trace molecules. However, space does have a definite smell, and we can smell it in a roundabout way.

I have had the pleasure of operating our space station airlock for many crewmates while they went on spacewalks. Each time, when I repressurized the airlock, opened the hatch, and greeted my tired returning friends, a peculiar essence drifting about the newly repressurized chamber tickled my olfactory senses. I noticed that the smell was coming from the spacesuit fabric, the tools, and any other equipment that had been brought inside. It was more pronounced on fabrics than on metal or plastic surfaces. It most definitely did not come from the air lines that pressurized the chamber.

At first I couldn’t quite place the smell. The best description I can come up with is that it’s rather pleasantly metallic. It brought me back to my college summers, when I used an arc welding torch to repair heavy equipment for a small logging outfit. It reminded me of sweet-smelling welding fumes. To me this is the smell of space.

Reptiles have smell sensors located not within their nasal passage, but on the roof of their mouth. They smell by waving their moist tongue in the air, then pressing it against the roof of their mouth, thus indirectly transferring molecules from the air to the olfactory sensors. It occurred to me that I was smelling the essence of space through an indirect transfer, in a manner not unlike that of our lizard friends.

Twice a year, near the winter and summer solstices, the orbit of space station nearly parallels the terminator—the fuzzy line separating day from night on the surface below. For a period of about a week, we live in what seems like perpetual twilight, being in neither full daylight nor full night. Our orbit follows the terminator, so that space station is constantly sunlit. From this vantage I can see both day and night simply by swiveling my head from left to right. But the night is not really dark, and the day is lit by low-angle rays from the Sun.

Geographic relief casts long shadows, and imparts stark contrast to features that are typically overlooked. Small ripples in sand dunes make high contrast striations across the bright desert landscape that look like Nature’s way of drawing with pen and ink. Geographic relief plays tricks on you. First you see the Grand Canyon as this deep scar. Blink your eyes and it is now a rippling bump. Thunderstorms cast shadows that look like they come from some new type of ray beam weapon. Airliners, their path defined by contrails, leave glimmering lines like snail trails in the morning dew. The gardens of Earth appear to have quite an infestation of snails.

The Moon sets in a counterintuitive way. From this vantage it moves nearly parallel to the horizon. Once I saw it slowly set, only to reappear in a few minutes. The Moon was visible for nearly the whole orbit.

The night side is equally fascinating. The atmosphere on edge glows with a vibrant electric blue. Did van Gogh paint this scene? I can see at least five, maybe six distinct layers of blue—perhaps a visual display of the classic atmospheric strata. Just past the terminator, rays of sunlight can be seen projected above the darkened limb of the Earth.

The most striking aspect of our atmosphere is not the palette of electric blue colors but the thinness of it all. Our atmosphere is a diaphanous veil; thin, fragile, transparent, and the only thing that protects us from the harsh vacuum of space. Too much atmosphere, and the planet is choked and suffocated. Too little, and it is exposed to the harshness of cosmic space. My vantage on the station gives me a deep appreciation of this fact.

I like to eat with chopsticks, and I bring a pair on every flight. Like some prehensile extension of my fingers, they allow me to pull food out of its gooey pouch without getting sticky fingers. In weightlessness I can manipulate a huge chunk of food — maybe an agglomeration of ravioli that would normally fall apart under the influence of gravity. Here the pieces stay loosely connected, like a miniature collection of asteroid debris. These can be eaten as is, or wrapped between a couple of tortillas.

There are Velcro dots fixed to my chopsticks so they can be parked on the galley table and not float away. At least so I thought. I parked my chopsticks in the middle of dinner so I could fly to the cupola windows and take a picture of the Earth. When I came back, one of the chopsticks was gone. It had just floated off. Apparently I did not firmly engage the hook to the pile. My first instinct was to look down. This works on Earth, but not up here. I made a broad sweep of the surrounding volume. A small floating object is difficult to find in the camouflaging background of spacecraft clutter. My chopstick had simply vanished. Two days later, one of my crewmates found it stuck to a ventilator inlet grill.

In space you get to play with your food and call it science.

Editor’s Note: Don did an interview today with Oregon radio and TV reporters, and talked about everything from space immigration to the calluses that develop on the tops of your feet in zero-G (while the bottoms of your feet get soft). Here’s the video: