Ibn Al-Haytham: The Proud Physicist

Until Galileo Gelilei the assumption was that all objects tend resist movement to stay at rest. Until Antoine Lavoisier the assumption was the burning an object will cause the destruction of matter and disappearance of mass. Until Louis Pasteur the assumption was that living organisms would commonly descend from non-living objects--flies plainly come from putrid meat, aphids from dew, mice come from haystacks, fish come from water, alligators come from wet rotting logs, etc. Until Hermann Joseph Muller the assumption was that radioactivity was healthy and invigorating for the human body. (All fine stories those that we will get to in due time.)  The point is that “common knowledge” certainly does not always reflect reality, and oftentimes experimentation results in unexpected, even counter-intuitive, sometimes baffling results.

Experimentation is all about constructing a test to measure something and help decide between competing hypotheses; this is a more conclusive method than the old guessing of intuitive reasoning.

 

The first noted experimentalist was the 11th century CE Iraqi physicist Ibn al-Haytham (بن الهيثم, also sometimes simply “Alhazen”), someone who actively rejected Aristotelian intuitive reasoning and attempted to prove a hypothesis using observation from constructed experiments. Al-Haytham was born in 965 CE in the city of Basra of modern Iraq, in the Persian Empire. Records depict Al-Haytham as a brilliant, proud, confident, but cowardly man. Legend has that he boldly proclaimed that he could study and control the periodic flooding of Nile River. When the ruling Caliph demanded this task from the boastful Al-Haytham, the physicist quickly realized he could not do it, so he faked insanity to save himself from the wrath of the Caliph. He was then placed under house-arrest, where he quietly conducted most of his experiments.

Al-Haytham is most famous for his study of light. He attempted to address a recurring ancient debate about optics and vision: Do objects emit something that reaches the eyes, or do the eyes emit some beam that reaches and detects objects? This question might seem preposterous to us in the 21st century, but by far the most commonly accepted theory at that time was that the eyes send out a beam like a sort of radar that allows us to perceive the world. As cool as that would be to have radar-eyes, Al-Haytham developed his hypothesis that the eyes receive rather than send a signal, reasoning, among other things, that stars should be too far away for a eyes to send a signal to, and reasoning that the existence of darkness should preclude the emission hypothesis. After all, if the eyes can send out a signal, why would they stop doing it at night?

He used several experiments to show that beams of light travel in straight lines from a source. In one experiment, he positioned a straight tube and a curved tube next to a light source. Light could pass through the straight tube, but not the curved one, therefore the light must only move in straight lines.

Another experiment was a famous pinhole projection model. The idea was that in a dusty, darkened room, one could see the straight path of light pass into the room. Al-Haytham expanded upon this simple idea to develop a device called a camera obscura (Latin for “darkened room”). He predicted, and then showed, that he could produce a crude projected image of an object by forcing light through a tiny pinhole. Much like the projector at a movie theatre, he could see the dust in the path of the projecting light. He also noted that narrowing the pinhole produced a sharper, but dimmer, image. Al-Haytham’s conclusive experiment on the cause of vision involved him viewing pinhole projections of oil-lamps switching on and off. 

As you can see, the requirement for light to "squeeze" at a precise angle through the narrow pinhole results in the projected image appearing inverted.

Later developments were remarkably advanced; Al-Haytham’s treatise Book of Optics, completed some time around 1021 CE, is one of the most influential in the history of physics, including numerous experiments on refraction, reflection, lenses, and mirrors, and descriptions of the atmospheric refraction that causes phenomena such as rainbows and twilight (resulting in a rather accurate calculation of the height of Earth’s atmosphere). Reflection, al-Haytham observed, is the change of direction of a light ray at the surface of a medium interface (where two different media meet). Refraction is the change of direction of a light ray as it passes from one medium to another, like from air into water.

In this diagram representing refraction, we can see that the angle changes when the ray changes media: once from air-to-glass, and then again from glass-to-air. The dashed line represents the apparent path of the ray, had it been unimpeded.

Different colors of light refract differently--red refracts least, and violet refracts most. (We will delve into this when we talk about the physical nature of light.) Al-Haytham was able to accurately explain the phenomenon of twilight, understanding that as the light passes from the sun to our atmosphere the air causes light to refract. When the light from the sun approaches at a certain angle, the red light reaches our eyes while the other colors tend to refract away. Rainbows occur when light at a certain angle passes from air into water droplets and then back to the air.

Al-Haytham showed that perceived white light is actually a mixture of colored lights (thus lending way for 'Dark Side of the Moon' about 950 years later).

He speculated on the physical nature of light that might cause such behavior. He also dissected eyes and attempted to assign explanations to the anatomy, though he incorrectly identified the eye’s lens as the receptive tissue, whereas we know now that it is the retina on the back of the eye that detects light. Al-Haytham’s mathematical solutions to some of his problems were generations ahead of his time--he came very close to inventing methods that what we now call calculus.

As a legacy, Al-Haytham’s most important contribution was that he developed and described abstract theories from inductive reasoning, and then systematically evidenced his predictions. Translations of these works and others did not reach Europe until around the early-13th century, where they may have inspired modern methodologies of later scientists like Roger Bacon, Galileo, and others whose work we will discuss in depth another day.

Important Ideas

• The Iraqi physicist Ibn Al-Haytham was a trailblazer of the scientific method of observation, testing, and measurement of hypotheses in order to reach verifiable conclusions.
• Al-Haytham’s experiments led to numerous significant advances laying the foundation for physical optics.

Other Interesting Reading

• Ibn Sahl, a Persian optics engineer who laid the foundation for a lot of al-Haytham’s work

In The Beginning: Thales of Miletus

“Science” is an enormously broad topic that basically encompasses all disciplines that attempt to investigate and explain phenomena using empirical observation, while connecting and integrating prior knowledge. Fields ranging from nuclear physics to developmental biology to behavioral psychology to organic chemistry to even political science attempt fundamentally to employ the same strategies of observation, testing, verification, and analysis, in order to draw conclusions about the function of our world. Here in the 21st century we tend to take for granted this very concept of scientific endeavor. Radio sets, dinosaurs, volcanoes, Mars, and the DNA molecule just to name a small few are elements of science that have propagated in popular culture--even to those of us who never really participate in process, and, yes, even those of us who reject many of the conclusions of science.

My job here is to communicate--to make science accessible, interesting, and relevant. I produce short posts that introduce a scientific topic, its history, its conclusions, and its impact on society. I will do this primarily by discussing the people and their works, including some of the detail of the science itself. This is not intended to be just a biography; I want to communicate the concepts within the context of these lives. Sometimes I will write about one individual, and other times I may need to focus on a group of scientists.

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With a natural starting-point for my first series, I will briefly explore the history and origins of scientific thought itself.

Not a whole lot of detail is known about scientific investigation in the ancient worlds. The few existing records of the earliest precepts of science from various ancient worlds and times focus mainly on nature--attempts to explain the Earth and Sky. A handful of Ancient Egyptian texts (c. 1600 BCE) describe medical diagnosis and treatment of physical trauma, including basic surgeries and several magic spells. Babylonian astronomers of Mesopotamia, by around c. 500 BCE, had established a famously robust mathematical description of celestial movements. However, these disparate fields of geometry, arithmetic, astronomy, medicine, and engineering were not understood at that time as analytically related until developments in Ancient Greece.

The Edwin Smith Papyrus describes basic surgeries.

The first abstract discussion on matters of the natural world came from Ancient Greece, in what is known as the pre-Socratic traditions (roughly 625 - 400 BCE). The most famous of the Greek philosophers predating Socrates was the earliest of the traditional Seven Sages of Greece, called Thales (THAY-leez).

Sketch rendering of Thales of Miletus

Not much of Thales survives today, and most of what we do know is second-hand descriptions from later Ancient Greeks thinkers, particularly Aristotle. (We will see plenty of references to Aristotle in coming discussions.) Thales, we can say with some certainty, lived from the mid-620s BCE until the mid-540s BCE. He was born, probably to an aristocratic family, in Miletus, an Ionian Greek seaside town in what is now southeast Turkey, and was educated by Egyptian priests.

Accounts of Thales depict a bold, confident, slyly intelligent man. He once allegedly made a fortune buying and selling olive presses in order to boast his ability to predict growing-season weather. He was involved in politics and warfare, counselling the establishment of a central government for the Ionian people, and helping instruct leaders on defending their lands from invading Persians. (Accounts are not clear whether Thales began his work on naturalism during or after his political career.) One story has that Thales accurately predicted a solar eclipse on a day of a battle, which, in awe, caused the combating sides to lay a ceasefire. Thales was also a noted geometer, skilled in his understanding of similar triangles and their angles. (There are today two separate geometric theorems that are sometimes called “Thales’ Theorem”.) Thales was also supposedly absent-minded, and once got himself trapped in a well because he was not paying attention to his way. Whether these tales reflect reality or a mythologizing of the man is anyone’s guess.

One of Thales’ Theorems states that drawing two straight lines from any point on the edge of a semi-circle to the corners will invariably result in the creation of a 90-degree angle.

As evidenced from their many noted Olympian myths, the Ancient Greeks tended to explain the occurrence of natural phenomena with reference to gods and heroes. Thales instead, attempted to elucidate natural processes in and of themselves. His legacy was that he was perhaps the first scholar to firmly reject supernatural explanations of phenomena, and it is in this regard that Thales has earned his superlative as the Father of Science. Some ideas in medicine, mathematics, and astronomy had already existed, but Thales was the first to unite these things under a new concept of analytic explanation.

Thales and his successors tackled questions such as from where, and from what, matter arises, and how we can explain why matter exists in many different forms. The problem with the Greek naturalists from a perspective of modern science is that they generally attempted to explain their observations of nature from a basis of intuition, not investigation. Intuition, unfortunately, has proven time-and-again to be an extremely poor method for describing phenomena in the Universe. (After all, how many of us would have simply guessed by our intuition the existence of, say, plate tectonics?)

Although Thales rejected supernatural explanations, postulations attributed to him include that all matter is composed living beings (this theory was inspired by his observations on magnets), that all matter derives from water as the sort of “parent”, or that earthquakes are caused by floating land pitching and turning on waves of water. Even the famous Ancient Greek postulation of the existence of atoms elaborated by the philosopher Democritus was based on speculation, not any particular evidence. (The fact that he was indeed correct about the existence of atoms might be seen as somewhat lucky.) The great Aristotle, famous for his advocacy of empiricism, was not immune, writing “intuition will be the source of scientific knowledge.”

The next important development in science, therefore, would be the departure from intuitive reasoning, and the rise of experimentation. The first scholar of note to write a refutation of Greek techniques of reasoning came more than 1,000 years later, in Iraq.

Important ideas:

• The Greek philosopher Thales delivered an important conceptual breakthrough in his attempts to explain the world only in terms of natural occurrences.
• The Ancient Greeks employed intuitive reasoning--essentially “educated guessing”--which we now say is a flawed method for conducting most science.

Other interesting reading:

• Look into Democritus of Abdera, also sometimes called a “Father Of Science”, a man whom the great philosopher Plato despised so greatly that he passionately recommended all of Democritus’ work destroyed.

Come On In Folks

Welcome to Science Figures, or "Sci Fig"--the educational blog on science and scientists. What you are going to see here is clear, concise, captivating educational material, interspersed with some commentary on science and education.

Who am I, you might ask. My name is Andrew. I just earned a bachelor's degree in biology from George Washington University, I live in Michigan, and I am happy to answer emails if I can. Now, I don't really like the word "blog" or being called a "blogger", but until someone comes up with a better term, we're stuck with here calling this a blog. I am passionate about sharing knowledge, and helping people appreciate wonder in our World.

Here's Sci Fig's raison d'etre in a nutshell:

• Clear, organized, interesting, easily-understandable, free education material is surprisingly difficult to find on the internet.

Wikipedia is wunderbar, but have you ever tried to read their entry on general relativity? For those of us who are non-physicists (a.k.a. normal people), most will experience a sensation similar to hypnosis, compulsively check Facebook to snap out of it, and learn essentially nothing (except maybe that Ben lost his phone again...). The problem with the likes of Wikipedia is that information and education are not the same thing. Encyclopedias contain knowledge, but unless you're A.J. Jacobs, they are not strong learning materials.

At the same time, textbooks are verbose, boring and...holy cow! have you seen the price-tag on those things lately!?

So how can you trust me and my work?

1. I am accountable. I will happily accept (reasonable) criticism in comments or emails. If something is demonstrably wrong, I will correct it.
2. To be clear: My information is a combination of what I know off-hand, combined with good ol' fashioned Google books. I understand that some material may be "boiled down", and ignore some complicating detail. That's artistic license. All diagrams are my own unless otherwise stated.
3. Sci Fig is not an ideological blog. It may not be 100 percent politics-free, but I'd like it to be as close as possible. This is for everyone to appreciate.

I will demonstrate that science can be readable and relevant, and people of all ages can appreciate it.