Section 1: Rethinking Space and Time Again
“We are so locked into the world of our own senses that, although we readily understand and fear a loss of vision, we cannot conjure a picture of a visual world beyond our own. It is humbling to realize that evolutionary perfection is a will-o’-the-wisp and that the world is not quite what we imagine it to be when we measure it through a lens of human self‑importance.”
Timothy H. Goldsmith
“What is essential is invisible to the eye.”
Antoine de Saint-Exupéry
Neutral Buoyancy Laboratory, NASA’s Johnson Space Center, Houston, Texas.
I am drifting-floating just inches above the dazzling white surface of the International Space Station (ISS). This brilliant playground calls to me, connecting me to a sensation discovered during childhood after building my first fort – a place where I could keep my top-secret projects safe, a place where I could observe the rest of the world as an outsider. Simply being here dilates my nerve endings and heightens my senses. In the background there are invisible eddies of resistance and my skin tingles with a constant stir.
As I look at the structure before me it is impossible to tell whether I am moving or it is moving. All that exists of the motion between us is relational, no other meaning survives. Another yellow handle comes within reach. I extend my hand and gently tug on it to redirect my course. I can feel the billowing cylinder rotate beneath me right on cue. I have to remind myself to breathe.
I continue gliding slowly from one handle to the next as if I were playing out the stanza of an eloquent symphony. Arm over arm I move over this surface as the music in my head builds toward its apogee. Although I am watching this space ship move beneath me, I suspect that an onlooker would describe me as a small bug encircling the branch of a tree. That is, if they allowed themselves to compare one of history’s most impressive construction projects to the branch of a tree.
In the middle of this stanza I hear the crackly voices of Mission Control over my bone phone. They are detailing the Orbital Replacement Unit (ORU) procedure as the Mission Specialists make their way from the Pressurized Mating Adapter (PMA). One of those astronauts is my dive partner’s father.
After completing our NASA nitrox certification, Brad and I undertake our first mission. My beating heart is constantly expressing how big of a deal this is to me. Even access to the deck above is tightly restricted, but now, as official flight leads, we are floating with astronauts around the ISS with a project of our own. The sensation is exhilarating.
The Neutral Buoyancy Laboratory (NBL) contains the world’s largest indoor pool (202 feet long, 101 feet wide, and 40 feet deep). It is a satellite to NASA’s Johnson Space Center (JSC) in Houston, Texas. This pool harbors exact scale mock-ups of the ISS, the Hubble Space Telescope (HST), and the Space Shuttle Cargo Bay, which are used to simulate mission EVA’s (Extra Vehicular Activities or ‘space walks’).
When the NBL was originally built, NASA had some difficulties procuring the appropriate water allocations for it. Consequently, it took over a month to fill the pool using only a garden hose. Now the entire volume, along with its carefully balanced chemicals, is filtered every twenty-four hours.
As the astronauts continue their simulation Brad and I begin our task. Our ‘cowboying around’ — which is what it is called when an EVA is performed without a tether — is not just an attempt to fulfill a childhood dream; we are photographing several of the external ISS components and its general profile for a catalogue we are composing. The ISS is reconfigured daily to replicate the stage of construction that each simulation crew will encounter in space. Photos of the intermediate stages will be a useful reference. Volunteering for this task gave us a good excuse to get into the pool every day.
I am carrying a bulky underwater digital camera and snapping pictures of this inspirational behemoth as it floats beneath/above me. When the memory card is almost saturated I hand the camera to Brad and begin to explore. It takes surprisingly little imagination to pretend that I am actually in space. Everything is neutrally buoyant — just floating about. The Cargo Bay of the Space Shuttle is visible off in the distance, and when the conversations with Mission Control cease, an eerie silence surrounds me. The colors are different too – not quite like they would be in space, but different enough to spark a feeling of the unfamiliar. It is a feeling that pours over my body and passes right through me.
As I recall my dreams of being in space and I am overcome with the desire to discover what if feels like to be drifting off into the heavens without the possibility of retrieval. Knowing that I am not wearing a tether (and allowing myself to believe that I am in space instead of a pool), I grip another protruding yellow handle and accelerate toward the edge of the cylindrical laboratory. I see the massive structure move beneath me. Handle to handle I pull and push. Then, as I launch off the edge of the structure, I turn and watch home base drift further and further away.
That’s when it hit me. That’s when I really figured out what it means to say that velocity is entirely relational. I had expected to experience what it was like to be drifting away from the ISS to my inevitable end, but instead I witnessed the ISS drifting away from me. This was somewhat surprising. For some reason, every time I had imagined what this experience would be like I had visualized it from the reference frame of the ISS. Now I was seeing it through my own eyes — from my own reference frame. The experience deeply rooted my intuition in the foundational principle in physics that tells us that all inertial frames are on equal footing — that one constant velocity reference frame is just as valid as any other.
Galileo Galilei connected to this principle inside the cabin of a ship. Einstein used the train station in Bern, Switzerland to relate his connection to it. I had learned from their insights and had completely accepted the principle of inertial frames as a fundamental truth. But until I actually saw the ISS drift beyond my reach, my intuition had not absorbed it. I had not grasped the enigmas that come with this truth. I had not wrestled with the mysteries that surround this simple property of spacetime. I had never asked why it is that all inertial frames are equal. This simple question turns out to be a very profound.
The greatest mysteries of the physical realm are but echoes of our ignorance of the true nature of space and time. Although they underlie all of our experiences and form the very metric of Nature, space and time have remained so clandestine that we haven’t definitively defined them. It is time for us to get beneath this nebulous understanding. It is time for us to crown our search for ontological clarity, to open the door of a wondrous world accessible to us by the power of scientific imagination, and to learn to see what is invisible to the eye. In order to do this we must focus in on the core of our ignorance. We must recognize the root of our confusion and wrestle with questions that reflect that root.
It is time for us to crown our search for a deeper essence, to open the doors of a wondrous world that is accessible to us only by the power of scientific imagination, to learn to see what is invisible to the eye. In order to do this we must focus in on the very core of our ignorance. We must recognize the root of our confusion and wrestle with questions that reflect that root.
This is not an easy thing to do; in fact, it is extremely difficult. The brilliant physicist Kip Thorne used a superb example that highlights why it is so difficult for us. He notes that Hendrik Lorentz and Henri Poincare both produced valuable insights that could have easily led them to discover Einstein’s new vision, but neither of them took that final step. Why? The answer, according to Thorne, is that both men “were groping toward the same revision of our notions of space and time as Einstein, but they were groping through a fog of misconceptions foisted on them by Newtonian physics.” (Thorne 1979)
Einstein by contrast was able to cast off Newtonian misconceptions. His willingness to start his investigation from scratch, whether or not it meant destroying the foundations of Newtonian physics, “led him, with a clarity of thought that others could not match, to his new description of space and time.” 
The lesson here is that if we are serious about questioning things, we need to question even the structural foundations that lie underneath our assumptions. We need to be willing to rebuild the entire metric of physical reality — should our investigation require it. Only then can we reach into the depths of our ignorance. Only from this state of mind can we truly press on with our journey.
In this spirit, let’s ask the most foundational questions we can – questions about the metric of spacetime. What is space? What is time? These questions appear to be entirely embryonic, and it seems that the answers should be readily evident, but they aren’t. Hypothetical solutions to these questions have come to represent the centerpieces of a realm still beyond our experience and imagination. To unveil that realm, we need to enter the debate over the essence of space and time.
Newton, who was one of the most influential captains on this quest, spearheaded our journey under the direction that space and time are real – that they are physical entities. But after Newton retired his command, Mach reversed our course by insisting that space and time aren’t real physical entities at all. Later, Einstein redirected us to an entirely new heading by redefining what we mean by space and time. Under this new direction we entered waters that had never before been charted. For a while, the dream of discovering a richer map filled our sails. But this optimism didn’t last for long. After a few short years Einstein reluctantly relinquished his command to the tyrannical whims of quantum mechanics. From that point on we have been randomly changing course, nauseously flickering from one heading to the next with each new moment.
The wind still blows but our sails rarely capture it. It has become increasingly obvious that we are lost in the middle of a disorienting ocean, spinning about a heavy anchor.
To reach our desired goal we need to lift that anchor, re-establish a heading for our intellectual quest, and to use our full sail to propel us toward a new destination. In order to do this, we need to figure out where we are and how we got here. We need to trace out the ideas that have guided us to this point, and then we need to find out what assumptions those ideas are based upon. After we have done this, we will concern ourselves with scrutinizing the map that falls out of those assumptions. It is by this process that we will learn how to pick a new direction, trim our intellectual sails, and recapture the wind. Here we go.