This presentation describes the scientific method and examines the reasons why controversies arise about scientific hypotheses.
Transcript:
This presentation describes the scientific method and examines the reasons why controversies arise about scientific hypotheses. The scientific method is supposed to be an objective procedure for determining truths about natural phenomena, so it is counterintuitive that there should be any big disagreements about ideas that have been tested and confirmed by experiments. Some scientific hypotheses make it possible to predict something that will happen in the future, so when a prediction is fulfilled, the scientific hypothesis is validated. This power of prediction is what makes science very valuable for human civilization.
Humans have always known that the movement of the Sun and the Moon along the background of fixed stars is associated with the tides and the seasons. This knowledge makes it possible to choose the time for planting crops or planning voyages or migrations. The study of the heavens and the movement of the celestial bodies has always been of great importance to human civilizations.
In the 2nd century of the Common Era, Claudius Ptolemy, an Egyptian astronomer and mathematician of Greek descent, standardized a geocentric system where all the planets and the Sun revolved around the Earth. It was a very logical system. Every day, we see the Sun rise in the east and set in the west. The stars also move from east to west during the night, so it is obvious that all the celestial bodies are moving around the Earth while the Earth is standing still. But there are some notable exceptions. The planets reverse their course against the fixed stars in a way that can be explained if the planets move in circular epicycles along their orbits. Using tables compiled by Ptolemy, astronomers could accurately predict eclipses and the positions of planets. The Ptolemaic system remained the standard explanation of the movement of the heavenly bodies for 14 centuries.
In 1543, Polish astronomer Nicolaus Copernicus published a book proposing that the earth rotates daily on its own axis and revolves yearly around the sun. This idea had been considered since antiquity, but it had been rejected in favor of the more easily visualized concept that the earth stands still and all the heavenly bodies rotate around it. In the Copernican system, the daily rotation of the Earth from west to east could account for why the sun appeared to rise in the east and set in the west. Also, the yearly orbit of the Earth around the Sun explained why the nearby planets appeared to reverse their trajectories relative to the more distant stars. The heliocentric model by Copernicus did not need epicycles, but many questions had to be answered, such as: "If the Earth is rotating so fast on its axis, why can't we feel it?"
Galileo was a mathematician at the university of Padua who had been using a telescope to study the planets and the stars. In 1610, he published a book called The Starry Messenger where he reported his observations of the Moon, Jupiter and the Milky Way. Galileo had concluded that the geocentric Ptolemaic model was wrong and he promoted the adoption of the heliocentric model by Copernicus.
This got him into big trouble because the Copernican system was investigated by the Roman Catholic Church in 1615, which concluded that heliocentrism was "foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture." In 1616, the Catholic Church issued a prohibition against the Copernican theory of the earth's motion. Under the leadership of Pope Urban VIII, the Roman Inquisition tried Galileo in 1633 and found him "vehemently suspect of heresy". Galileo was sentenced to house arrest where he remained until his death in 1642.
It took more than a century for the helicentric system to become widely accepted, but it was only in 1992, 359 years after Galileo's condemnation, that Pope John Paul II officially declared that Galileo had been right and admitted the error of the theologians of the time, when they maintained the centrality of the Earth.
The scientific method consists of making observations about physical phenomena, creating a hypothesis to explain the observations, and testing the predictions of the hypothesis to verify its validity. If a hypothesis cannot be tested, then it is not considered a scientific hypothesis. Science is supposed to give us an objective reality that everyone can accept. It seems like a very simple concept, but it is very difficult to implement.
Errors can be made in the observations because each one of us sees things in a different way. Stars always looked to me as blurry lights in the sky until I got glasses at age 14. In college, I had a colorblind roommate and we seldom agreed on the color of things. Each person has a different perception of the world. Some people may consider a glass to be half full, but others will say that it is half empty. The whole controversy of the geocentric versus the heliocentric system depends on whether we considered that the Earth is rotating along its axis or not. The way in which observations are made is very important in order to reach a consensus that reflects reality.
A scientific hypothesis provides an interpretation of the observations according to well-established scientific principles that can be tested. The Ptolemaic geocentric system was able predict eclipses that could be confirmed by observation, but there were inconsistencies in some small details that were discovered after the invention of the telescope, such as the phases of Venus. Galileo found that Venus went through phases, just like our Moon. Galileo concluded that Venus must travel around the Sun, passing at times behind and beyond it, rather than revolving directly around the Earth. In general, an inclusive hypothesis that explains all the observations is preferred over a hypothesis that cannot explain some of the observations.
The scientific method depends on physical tests or experiments that determine whether the predictions made by a hypothesis are true or not. The tests may be repeated several times to make sure that the results are reproducible. It is important to test the correct things, especially for complex systems that may have many interactions or dependencies. Sometimes, a computer model can be programmed to simulate processes for which it is not practical to conduct a physical experiment. Computer models are convenient, but they can produce misleading results if the rules followed by the model do not reflect what happens in the physical world.
An example of an incorrect computer simulation is given in the paper by Silber, et al., published in 2021, which tries to determine whether the Hiawatha crater could have been created by an extraterrestrial impact on the surface of Greenland covered with a thick layer of ice. The meteorite would have had to punch a hole in the ice layer to create a crater in the underlying rock.
The numerical simulation or hydrocode in this publication treats the ice sheet as a plastic material that can be deformed, but this is not what really happens in nature. The computer model illustrates a layer of ice undergoing a plastic deformation in which the ice layer is stretched and distorted while remaining in place. This is completely wrong, and it is remarkable that the publication passed through the peer-review process. Ice is fragile and has low tensile strength. Professor Peter Schultz from Brown University has conducted many tests of high speed impacts on ice sheets using the AMES high-speed gun of the National Aeronautics and Space Administration. The experiments demonstrate that the ice sheet breaks apart from the shock of the impact and the pieces of ice are then ejected in ballistic trajectories far away from the impact zone. The computer model is wrong because it does not produce results that correspond to the real physical event. Unfortunately, papers with invalid computer simulations are seldom retracted and they mislead future researchers.
Here is another example of a publication with false information that has misled many researchers. In 1977, Raymond Kaczorowski wrote a thesis that attempted to show that the Carolina Bays had been created by gradualistic mechanisms from the action of wind and water. To test his idea, Kaczorowski created a circular depression filled with water on a sand table and set a fan to blow over the water for a period of four hours, but he changed the fan to blow in opposite directions every fifteen minutes.
Kaczorowsk wrote that his experiment produced an elliptical structure, but this is clearly false, and he never tested the geometry of the resulting pool. The original model lake was modified by the wind, but the resulting structure did not have an elliptical geometry.
Kaczorowski's experiment produced a shape like a bloated American football with pointy ends. An ellipse cannot fit into the resulting shape. Well-preserved Carolina Bays, by contrast, have a perfectly elliptical geometry. Kaczorowski's thesis was never published in a peer-reviewed publication, but it has misled a large number of researchers. Many peer-reviewed publications claiming that the Carolina Bays were created by uniformitarian wind and water mechanisms have referenced Kaczorowski's thesis to support their arguments. These citations provide undeserved legitimacy to Kaczorowski's thesis and increase the opportunity for further misguiding other researchers.
One of the most controversial science topics of this century has been the Younger Dryas Impact Hypothesis, which has sparked many contentious debates and personal attacks. In 2007, Richard Firestone and 25 co-authors proposed that one or more extraterrestrial impacts caused the extinction of the North American megafauna and triggered the Younger Dryas cooling event. This paper reported microspherules and nanodiamonds at the Younger Dryas boundary as evidence of an extraterrestrial explosion over North America that destabilized the Laurentide Ice sheet and caused extensive biomass burning.
Firestone's paper was received with great skepticism by the scientific community, and in 2011, seven impact experts wrote a requiem paper that declared the death of the Younger Dryas Impact Hypothesis. The paper said that Firestone had not shown an impact crater, meteorite fragments, shock metamorphism and other expected markers of an extraterrestrial impact. In addition, the microspherules and nanodiamonds submitted as evidence of the extraterrestrial impact could have had a non-impact origin. In terms of the scientific method, the experts basically said the observations made by Firestone were wrong.
Objections to the Younger Dryas Impact Hypothesis continued to pile on. In 2012, Mark Boslough and 15 coauthors wrote a paper saying that the fragmentation and explosion mechanisms proposed by Firestone did not conserve energy or momentum and that the hypothesis did not have a physics-based model.
The Younger Dryas Impact Hypothesis appeared to be dead, but in a strange twist of fate, an investigation seeking residue of an extraterrestrial impact on the Greenland Ice Sheet found a large platinum anomaly exactly at the Younger Dryas Boundary approximately 12,900 years ago. This was evidence that an extraterrestrial impact had occurred at the time proposed by Firestone, but the location of the impact was not determined. Today, the Younger Dryas Impact Hypothesis remains as a controversial scientific topic because the impact crater and the minerals with shock metamorphism have not been found.
The scientists who introduced the Younger Dryas Impact Hypothesis in 2007 are members of the comet research group. Some of these same scientists wrote a paper in 2021 proposing that 3600 years ago a Tunguska sized airburst destroyed the Bronze Age city Tall el-Hammam in the Jordan Valley northeast of the Dead Sea. Their paper published in the peer-reviewed journal Scientific Reports claims that the proposed airburst was larger than the 1908 explosion over Tunguska, Russia which had one thousand times more energy than the Hiroshima atomic bomb. The evidence for the airburst at Tall el-Hammam includes a city-wide layer of carbon and ash with a thickness of 1.5 meters that contains peak concentrations of shocked quartz, melted pottery, diamond-like carbon and other residues thought to be associated with the extraterrestrial airburst.
This publication received wide coverage in the media because it mentioned the possibility that Tall el-Hammam could be the biblical city of Sodom. The paper does not address this question, but considers whether oral traditions about the destruction of this urban city by a cosmic object might be the source of the written version of Sodom in Genesis. The scientific community does not hold legends and oral traditions as a reliable source for scientific research, so the reaction to this publication was swift and aggressive.
One of the first negative comments came from Elisabeth Bik who noticed repetitive parts in the corner of an image. Such image manipulation could potentially bias or invalidate the observations. Modification of the observations in a scientific report can undermine the credibility of the conclusions derived by the authors and brings up questions about ethics and professionalism.
The Comet Research Group replied quickly and admitted that the graphic artist had made minor, cosmetic corrections to five of 53 images. The Comet Research Group published the unmodified images and said that all of the corrections were distant from any important scientific data and no changes were made to key data, such as bones or potsherds.
Not long after the Comet Research Group's paper was published, an op-ed article in the Sapiens anthropology magazine characterized the research as Biblically Inspired Pseudosciience that encouraged illegal excavations. The critical article claimed that sensationalization of the story had led to its popularity, and also expressed profound disappointment that Scientific Reports, a peer-reviewed journal operating under one of the world's leading scientific journals, Nature, published pseudoscientific research about a supposed ancient cosmic airburst destroying the Tall el-Hammam site in what is today Jordan. The op-ed article chastised the Comet Research Group for speculating that this putative event may have been the basis for the biblical story of Sodom, in which a city was allegedly destroyed by stones and fire sent from the sky.
This is the way that science works. You make detailed observations and accumulate data for several years. When you finally publish something that you think is significant, critics come out of the woodwork to shoot down your hypothesis. Sometimes the criticisms do not seem fair, but if the hypothesis can withstand all the challenges, it may become part of the scientific mainstream.
The scientific method seems so simple. You make observations, generate a hypothesis and then you test the hypothesis. But there are many ways to go wrong at each step, so this guarantees that there will always be controversial science.
