The scientific method is the best tool of discernment we have. We don’t have to believe in things when using science. We just have to observe and make sense of the things we see. Nonetheless, we have to interpret and make sense of the evidence we gather through the scientific process to construct models.
For example, we have proven experimentally the theory of relativity’s prediction of being able to travel in to the future, e.g. the faster a particle (or person) travels the slower speed flows relative to a particle (person) at rest on earth. The implications of relativity and time travel are interesting to say the least, i.e. the person traveling at the speed of light for two weeks would return to earth where months have passed for the rest of us.
Many theoretical physicists believe there’s symmetry to the universe. (When I am using the word belief I am using it as a synonym for prediction.) For this reason some theorists argue if we can travel in to the future we should, at least in principle, be capable of traveling in to the past.
Enter Kurt Gödel.
Gödel (1906-1978) was an Austrian mathematician best known for developing the “incompleteness theorems” (theorems describing the limits of what mathematics can and cannot prove). Gödel used a combination of relativity’s predictions and mathematics to develop a model of the universe which predicted the Cosmos rotated (preventing the universe from crushing in on itself) while allowing for time travel in to the past.
According to Gödel’s model a traveler could return to a point in their own past by completing a circuit around a “cylinder” in spacetime (see diagram above). (Also, for more information see the September 2015 edition of Scientific American (Page 73).)
A closed timelike curve is any path through spacetime which loops back on itself. As it turns out, observations after Gödel developed his model have firmly established the Cosmos is actually expanding, not rotating. Nonetheless, prior to the observations made of an expanding universe, Gödel poured over all sorts of data to see if his model was reflective of reality. Despite Gödel’s error, the math underpinning his incorrect model of the universe was consistent with relativity (suggesting, at least at the level of mathematics, we could still learn something from the mistake: traveling back in time was theoretically possible).
The implication of Gödel’s work is obvious: scientists can construct models making valid predictions about reality even though the model itself might only be symbolic, or representational, of that reality. So despite the weaknesses in Gödel’s theory, there’s nothing about physics ruling out time travel to the past.
Reality is complex and it is rare indeed to be able to construct a model capable of fully explaining what’s going on “out there.” In fact scientists can create two models to describe the exact same phenomenon, e.g. light can be described as traveling as both a wave and as a discreet particle; gravity can be explained by appealing to either the bending of spacetime by massive objects, the action of conjectured gravitrons, and by appealing to the physical property known as acceleration (see Einstein’s acceleration-gravity equivalence). There is nothing contradictory about describing the same phenomenon using more than one model; rather, this capacity speaks to the explanatory power of science; that is, we can use science to develop different ways to describe the same reality in terms we can understand (even though reality, at its most fundamental or quantum level, makes absolutely no sense to anyone).
The KT Controversy
To get a basic appreciation for the nuances related to model creation, let’s consider the relatively recent controversy over the Cretaceous-Tertiary (KT) extinction event, i.e. a model positing an asteroid impact was responsible for the disappearance of the dinosaurs 65 million years ago.
What is incontrovertible about the KT Event is the fossil record firmly establishes the existence of dinosaurs and their relatively rapid disappearance at the time of the KT impact; however, the view perpetuated by well-meaning elementary and secondary teachers, that the asteroid was solely responsible for the extinction of the dinosaurs, might be overly-simplistic.
Subsequent analysis of the rock and sediment associated with the time period of the extinction event suggests the possibility these creatures were already in steady decline before the impact. The iridium found in the sediment of the earth at the KT (see Cretaceous-Tertiary boundary in diagram) may or may not be the product of an asteroid impact. Complicating things is iridium is also a product of volcanoes; as such, increased volcanic activity during the Cretaceous could actually account for the juxtaposition of iridium (leading to climate change) and the mass extinction event observed at and around the Cretaceous (for more see this article from the University of California (Berkeley): http://www.ucmp.berkeley.edu/diapsids/extinctheory.html).
This KT controversy is not the product of conflicting imagination or contradicting stories; it is born out of the genuine difficulty of constructing models from an interpretation of the available facts; and since science is not a fixed form of knowledge it is constantly being improved and amended; moreover, we are also not eye witnesses to the primary event forcing us to use a combination of evidence gathering and logical conjecture to put together a plausible picture. Scientists are detectives in the truest sense.
Suffice to say that although the scientific method helps us make some sense of things, the fact remains multiple and relatively trustworthy models can be constructed to describe the same reality or phenomenon. I do not mean to imply science as a result is arbitrary, only that, the rationalist would be wise to appreciate the scientific process produces plausibility not certainty; and I would further caution rationalists from doing expressly what they accuse non-rationalists of doing—believing science explains things, or rules out possibilities, that it does not.
Charles Darwin: The How Versus the Why
In his autobiography, the naturalist Charles Darwin (1809-1882) intimates science answers the question how physical processes unfold and not why they exist in the first place. Ultimately, it is an assumption nature is rationally organized as per the philosopher Immanuel Kant’s assertion that the language of nature is mathematics. Nature can be described using mathematics but it is not mathematics itself. In the great scheme of things, a model is our way of trying to make an irrational world—a reality shaped by both statistical determinism and randomness—rational.
In the 17th Century, Isaac Newton (1643-1727) explained the influence of magnets as the work of an invisible “soul.” Thinking of magnets in this way seems alien to us but it was natural to the people of Newton’s time, i.e. people believed some form of intentionality existed behind all things in nature. Unsurprisingly, most of us still perceive this intentionality in nature (contributing to our apparent inability at times to distinguish between correlation and causation). (For more on causation versus correlation see my article The Role of Perception in Science: Part 1 “Correlation versus Causation”.)
Although we no longer think of magnets in terms of souls, it is naïve to assume a scientist is immune to either the human penchant for story telling or from being influenced by their inherited worldview. Again, I do not mean to imply science is inherently untrustworthy. On the contrary, the Germ Theory of Disease would still be explained in terms roughly identical—pathogens cause disease—whether the author of the theory was a democratic-minded Frenchman or an authoritarian Russian.
Instead, the issue is whether the questions we ask lead us to answers reflective of what is actually happening in the world. In the end, and this is important to understand, we have no reason to assume the universe complies with our intellectual preferences for causal or rational order. Reality might just be, as the Enlightenment philosopher David Hume (1711-1776) asserted, a brute fact (no story or underlying purpose required).
Model Dependent Realism
In as much as the scientific method helps us construct plausible models of what is or what is not happening, rationalists still to varying degrees assume the scientific method is capable of describing the world with perfect objectivity.
How many high school (or university) science teachers teach the following fact? Even our best model is only ever provisional. In his book The Grand Design (2010), theoretical physicist Stephen Hawking (1942-present) describes the implications of our provisional knowledge by appealing to a concept called “model dependent realism.” Model dependent realism, roughly stated, is the notion our models (or perceptions) are merely representational (or symbolic) of reality. The models are not reality itself. Any assertion to the contrary, that “reality is one” as Plato insisted, that there’s no such thing as an “uncaused cause” as Thomas Aquinas argued, or “the earth is at the center of all creation because Man is God’s greatest creation” as the early Church intimated, etc. are just stories and illusions.
Hawking argues different models can describe the same phenomena and be equally useful; that is, the criterion for a successful model is not whether or not it disqualifies or even falsifies competing models; rather, a successful model is one which makes valid predictions while being simpler than a competing model. To illustrate his point Hawking contrasts Ptolemy’s “geo-centric view” with the Copernican or “helio-centric view” of the solar system.
The geo-centric view presented a description of the solar system with the earth at the center and the planets (and Sun) orbiting us. The helio-centric view by contrast posited the Sun at the center being orbited by all the planets.
Hawking asserted Ptolemy’s model is just as reliable a descriptive tool as the heliocentric when it comes to describing how the solar system functions, e.g. We could use Ptolemy’s model and still manage to send an astronaut to Mars or any other point in the solar system.
Hawking argued what ultimately set the heliocentric model apart from the geo-centric was the former provided a “simpler, more elegant” explanation for planetary motion while the latter required Ptolemy to posit something in to existence that did not in fact exist: epicycles (see diagram on the left). When the earth spins on its axis planets, unlike stars, appeared to the ancients to zig-zag back and forth. Ptolemy (90-168 AD) referred to this zig-zagging motion as an epicycle (a small local movement of a “planet” (a word in ancient Greek literally meaning “wanderer”)) while it orbited the earth.
The implications of gravity for epicycles and the geo-centric view notwithstanding, the strange implication of Hawking’s thinking is the following: it seems almost incidental planets in fact orbit around the Sun as opposed to zig-zag in fictional epicycles around the earth. Both models are functional and are usable to make successful predictions about where planets will be and when they will be there; it just so happens that the Copernican view is preferable because it does not postulate things into existence (like flat or immovable earths) just for the sake of making theory match observation.
Subjectivity is part of any scientific investigation and endows science with both unparalleled predictive and explanatory power for describing reality. Some critics claim that since scientists continually modify models, change their thinking, or cast aside obsolete theories, etc. science itself is inherently untrustworthy. Nothing is further from the truth. We should save such criticisms for those systems or ideologies which do not countenance or tolerate change or stand up to either testing or reasonable challenges. To change one’s mind in light of new evidence is wisdom, not folly, according the thinker with a more plausible view of how the Cosmos actually operates.