Physics has always been about figuring out the structure of the world, and the same can be said about our brains. However, physics often comes to conclusions that conflict with concepts fundamental to our minds, such as the realness of space and time. So, the question arises: are time and space objective realities or human-invented concepts?
Is space-time a real thing?
- Space-time is a concept in physics that combines the three dimensions of space and one dimension of time into a single four-dimensional continuum.
- It was first proposed by the mathematician Hermann Minkowski in 1908 as a way to reformulate Albert Einstein’s special theory of relativity (1905).
- Space-time diagrams can be used to visualize relativistic effects, such as why different observers perceive differently where and when events occur.
The history of the development of physics is filled with surprises, and many physicists believe that we are at a special junction again, where the next step might show that space and time are not quite real. But, how do we prepare for such a massive frameshift? To answer this, we need to understand the history of our ideas about space and time, and how they have evolved over time.
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The Evolution of Our Understanding of Space and Time
In the past, there were two radically opposing ideas about space and time. The first idea was the “Absolute” space and time view, championed by Newton. According to this view, space exists on its own, with no regard to any objects or entities, and time also exists, with its passage governed by a cosmic clock. However, this pure vision of absolute space and time could not be right, as ultimately, it did not correspond to our impression of them.
The second idea was the “relational” view, which considers space and time as a network of distances between objects or succession of events. Philosophers and scientists, such as Leibnitz and Descarte, considered this view to be more accurate. However, Newton thought that there must be a very close correspondence between our mental experience of space and time and the world external to our subjective experience.
Immanuel Kant also initially took Newton’s side on the reality of space and time but came to believe that space and time are not physically real but are constructs of the mind – inborn principles by which we organize the world.
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Einstein’s Perspective on Space and Time
So, how did Einstein explain space time? Einstein is often seen as the ultimate tie-breaker in the debate about space and time. In his essay about “the problem of space,” he wrote that “concepts of space and time are free creations of the human intelligence, tools of thought, which are to serve the purpose of bringing experiences into relation with each other.” Einstein’s statement implies that space and time are human inventions that serve as a mental construct for organizing our experiences.
The Neuroscience of Space and Time
The brain’s ability to understand space and time is critical to our survival, and it accomplishes this by creating a mental representation of the surrounding environment, often called a “cognitive map.” In 1971, neuroscientists John O’Keefe and Jonothon Dostrovsky discovered the first evidence of place cells, which are neurons in a section of a rat’s hippocampus that fire rapidly every time the rat enters a particular region. These place cells appear to represent our internal map of a given environment.
In 2005, Edvard and May-Britt Moser discovered another group of neurons called grid cells that behave like place cells but fire when the rat enters any number of other locations at equal distances from each other. These grid cells tile the current environment into grids of multiple different orientations and scales. Although each new space is tiled differently, individual grid cells represent a fixed scale, providing metric information with different resolutions.
Profile of May-Britt and Edvard Moser
The combination of grid cells and place cells seems to be a key part of the machinery behind our sense of surrounding space. The brain appears to include a coordinate grid, making space feel absolute rather than relational.
However, the brain’s processing of space and time is not so cut and dry. Under certain conditions, hippocampal cells seem to track the progression of time rather than place, suggesting that place cells may reflect our executed and planned trajectory rather than specifically space and time. This trajectory could be in actual space, an abstract space of thought and intention, or even a logical chain of reasoning. Evidence suggests that the hippocampus plays a critical role in laying down memories and indexing past experiences in a way that enables us to recall them in sequence, almost as though it were applying a coordinate system to them. This implies that the machinery that may have initially evolved for enabling navigation through space has been co-opted into a much bigger role.
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In conclusion – Space and time theory
We started by asking whether the space and time of our minds correspond to physically real entities. Some of the greatest minds in physics, including Einstein, thought that the perception of space and time are mental constructs. However, they were not saying that the external world isn’t real. Many researchers believe that our mechanisms for tracking time and space are general-purpose algorithms for tracking sequences of events and mapping the relationships between continuous variables. With navigation being such an essential function for survival, it seems likely that these systems evolved with the original purpose of doing this job for space and time. In other words, arranging the world into what, where, and when is our brain’s most efficient and meaningful way of carving nature at its joints. The fundamentality and primacy of space and time may stem from the fact that we have no alternative way of partitioning our experience.
As science continues to evolve and our understanding of the brain and the universe expands, it is likely that we will continue to be surprised by new discoveries and developments. It is important to remain open-minded and curious as we explore the mysteries of the world around us. By doing so, we may be able to unlock new insights into the fundamental nature of space, time, and our place within the larger cosmic order.
