Fear not. I am not about to launch a politically correct offensive against your views of space and time. I will not be the one to tell you that, like gender and race, space and time are social constructs—mere manifestations of confirmation bias projected on our universe to make us pubescent humans feel better about our negligible influence on the vastness of eternity.
Nonetheless, there exist certain inconsistencies in our layman views of space and time, inconsistencies that one must sort out before even attempting to apprehend the complexities of motion and mass.
It is easy to think of space as a three-dimensional grid, marked evenly along the x, y and z axes to indicate units. Each line that comprises the grid is perfectly straight and perpendicular to all other lines it intersects. Mass and motion find themselves inside of this grid, but they do not influence its structure. In this view, space is impermeable, independent of time, mass and motion.
What is time to the layperson? Time is unfathomable as a concept. It is and it marches forward because we have defined it as such. Time afflicts all mass ubiquitously and isotropically.
These views of space and time offer an ease of mind and measurement. They insinuate that time and space are universal and independent of one another; three seconds for me is the same as three seconds for you. If I measure a stick to be one meter, then the stick is one-meter long. Period.
These views, however, neglect to incorporate relative movement and mass. For example, imagine you are driving on a highway. A stationary police officer notes your speed to be 80 mph. In your frame of reference, you are not moving—that is, your speed is 0 mph according to you. Instead the road and the landscape and the police officer are moving past you in the opposite direction at a speed of -80 mph. Both you and the police officer disagree on who is moving, your speed and thereby space itself.
The previously established view of space, however, demands that there exists one correct measurement of space: a privileged view called “absolute space,’ which is a reference frame by which all other movement is gauged. Who, in this scenario, encompasses most this privileged view—you or the police officer? Both frames of reference are equally valid. Therefore, it is impossible to determine which is most true. In this regard, it is necessary to reform our earlier view of space. Space is not universal, and all frames of reference are equal.
Time is not universal either. Physicists studying particles called muons find that the average lifetime of a muon in the laboratory is shorter than that of a muon traveling at a speed comparable to that of light. As a result, traveling at a higher speed changes what one perceives as time and space.
Furthermore, we must address the segregation of space and time in our mentality. Consider the diagrams on the right, and entertain the idea that the two-dimensional map of Drake University is space. This map represents the set of all points in space at one instance in time; a time slice.
Notice that this time slice is more a comment on the state of space than it is on the state of time. Similarly, if one were to track the changes over time of one point in space, the resulting set would be more reflective of the state of time than of space.
Both time and space are, by nature, reliant on one another. Thus, for convenience in thought, we refer to this entity as spacetime.
“We must address the segregation of space and time in our mentality…for convenience in thought, we refer to an entity known as spacetime.”
This “spacetime,” as a concept and a mentality, aids an observer in thinking four-dimensionally. Moreover, spacetime is an ideal coordinate system with which one might reexamine gravity. For what is perhaps more difficult to wrap one’s head around—pun intended—is the idea that mass warps spacetime.
Gravity, alongside the weak, electromagnetic and strong, for that matter, were initially considered forces. As the name suggests, forces alter the preexisting trajectory of a body of mass, which by default would continue along in a straight line or at rest in eternal resistance to change unless alternatively acted upon. Gravitational attraction is one of these forces. It occurs as a result of the exchange of massless particles called gravitons, whereupon the mass experiencing the attraction would find itself displaced from its inertial disposition—or so it was theorized before Albert Einstein.
The problem with this theory of gravity is that gravitons are particles, and as such are limited in velocity to the speed of light. Even if gravitons travelled at this speed in their exchange with other bodies of mass, the effect of gravity would be slightly delayed. The general theory of relativity accounts for this delay, as well, contributing to the existence and propagation of gravitational waves. But physicists have not, as of yet, managed to detect these gravitons. Thus, the theory of gravity as a force loses its luster in the face of the general theory of relativity, which incidentally has much more experimental backing.
Perhaps a more apt perspective to behold is that of gravity as a field; a preexisting structure influenced by any and all mass in the universe. All bodies that enter this field instantaneously experience the effect of gravity, thereby eliminating the issue of lag. As object approach other objects, they accelerate towards each other in a manner proportional to the product of their masses. In this regard, the spacetime around the masses is said to be warped, given that the path of least distance between any two points is altered. You may already be familiar with the image of a large body of mass sitting on the sagging mattress of a two-dimensional grid. While not completely ideal as a diagram, the image does demonstrate how spacetime warps due to the presence of mass.
So why does any of this matter (I’m so punny)? Why do you, a non-physicist, need to reform your views on spacetime?
On a sociological level, the dismantlement of a privileged, hierarchal view of space grants an individual the recognition that there exist other perspectives of the same truth. In this regard, a subconscious reformation of your views of spacetime may extend your tolerance for other realities different from your own.
“There exist other perspectives of the same truth. In this regard, a subconscious reformation of your views of spacetime may extend your tolerance for other realities different from your own.”
Furthermore, the theory that gravity—and by extent matter—is intrinsic to spacetime and vice versa is an extraordinary enlightenment to behold. We, as beings comprised of mass, are such stuff that spacetime is made of. What a fanciful, beautiful thought.
Or perhaps, the conception that high velocities influence one’s interactions with spacetime will merely give you something to ponder on long road trips down I-80. There’s nothing like eleven hours on a highway that will make you reexamine your preconceived notions about spacetime.