1628: Blood Circulation

After thirty years of research, William Harvey’s landmark book On the Motion of the Heart and Blood in Animals established once and for all that blood flow was entirely circular and that the heart was a pump.  The discovery of blood circulation was transitory for a few important reasons. It established the principle of experimentation in medicine. It helped to create the new field of physiology. Lastly, it marked the beginning of the true understanding of our circulatory system with additional details to emerge later on.  

A Brief History of the Cardiovascular System up to Harvey

On the Motion of the Heart and Blood in Animals
On the Motion of the Heart and Blood in Animals
(Credit: Wikimedia Commons)

The ancient Greeks, those pioneers of scientific discoveries, once again lead the way in the fields of medicine and physiology in antiquity. It was understood by the Geeks that the peripheral parts of the body required nourishment. The mystery was how this was accomplished. The first detailed attempt at this explanation (that rejected divine causes) was put forth by Hippocrates of Cos and his pupils. It was grounded in humorism, a doctrine declaring that health was maintained by a balance in humors (bodily liquids). Disease was caused by an imbalance in these humors. Various Greek thinkers, including Praxagoras, Erasistratus, and Aristotle, identified the heart, veins, and arteries and theorized about their role in the blood system.

The next notable advancements came from Galen. Born during the second century AD at the height of the Roman Empire, he built on the systems he inherited from the Greeks while adding new information along the way. He carried out many experiments on animals, however none on humans. He was accumulated an array of facts and inherited ideas from which he attempted to deduce how the entire system worked. He differentiated between arteries and veins and proved that they both contain blood. This differed from Erasistratus’ view that arteries only contained air. He noted that the heart pulsated, that everything breathes, and made connections between the liver, heart, and lungs. While his system was complicated it was nowhere near as complicated as the human body’s system actually is. It can be summarized as the liver, veins, and the right side of the heart were to deliver nourishment to the peripheral parts of the body. Blood was thought to be manufactured in the liver, traveled to the peripheral parts of the body through the veins where the tissues take up its nourishment. The lungs, arteries, and the left side of the heart were to deliver fresh air and to cool the body.

The middle ages in Europe provided little advancement in knowledge. During this time the Catholic Church rose to power and suppressed any idea’s conflicting with Christian doctrine. Experimentation was discouraged and any new discoveries, such as Andreas Vesalius’s dissections or Realdo Colombo’s of pulmonary circuit, were made to fit in with Galen’s previously existing ideas, or ignored. This void of progress lasted about a thousand years, up to the time of the Renaissance.

William Harvey’s Contributions

The man who finally solved the riddle of the pathway of blood in the body was William Harvey. Born in 1578 during the Scientific Revolution, Harvey attended the University of Padua, the greatest medical school of its time. There he learned Galen’s physiology and throughout his life he still held on to some notions of ancient doctrine. However like many of the famous early scientists of his era he was not afraid to challenge it. He was very interested in academics and in his late 30s he decided to tackle the problem of how the heart works.

First, Harvey worked with animals to make his observations, sometimes cutting the chest of the animal open to watch what happens to the heart as the animal dies. Through his dissections, he was able to identify a thrusting motion which we now call systole, where the blood is moved out through the body. More specifically, he noticed that blood returns to the heart and fills up the atrium, the two chambers above the heart. When the atrium becomes full, the blood empties into the ventricles below, which then pump the blood out to the lungs and rest of the body. These studies become to topic of his lectures as the Lumleian Lecturer at the Royal College of Physician’s, and became the raw material for the first seven chapters of his later book On the Motion of the Heart and Blood in Animals. Additionally, his experiments with animals showed that that blood flows away from the heart in arteries and towards the heart in veins.

It had also made little sense to Harvey that so much blood should be going out to nourish the body with so little of it returning. Was it really possible that the liver could really make so much blood? He decided to make some rough estimates of the volume of blood passing through the heart. First, he noted that a human heart could hold about two ounces of water. He multiplied that by an average number of beats per minute, and took that figure times sixty for each minute in an hour. This lead to a conservative estimation showing that about at least hundreds of pounds of blood must flow through the heart in an hour. Clearly there was no way the body could produce this amount of blood each day.  By simple deduction this proved that blood flow must be circular.  The question became how did the blood come back?

Veins of the Arm,  On the Motion of the Heart and Blood in Animals
Veins of the Arm, On the Motion of the Heart and Blood in Animals
(Credit: Creative Commons)

His teacher at the University of Padua was a man named Fabricius who discovered the values in the veins but could not explain their function. By compressing veins at various places of the body, Harvey showed that blood flows from the periphery to the center of the body and that blood flows in one direction. The valves keep the blood from reversing direction.

Although Harvey proved blood circulation, he work had little immediate effect. Blood letting continued for some time and the clinical value of understanding blood circulation seems of little importance. In the long run, it marked the end of the Galenic theory and marked an important turning point for modern medicine.

Continue reading more about the exciting history of science!

John Napier

John Napier portrait
John Napier

John Napier (1550 – 1617) was a Scottish mathematician best known for his formulation of logarithms which provided aid to mathematical calculations.  In 1614 he published he book titled A Description of the Wonderful Law of Logarithms, which explained the technique of devising the logarithm (and differs from today’s concept of having a base raised to a corresponding exponent) and provided copious tables of logarithms to make calculations easier.  Additionally, Napier was the first to popularize the decimal point as a means to separate the fraction from the integer.

The logarithm is simply the inverse operation the the exponential, in other words a logarithm can be used to undo what an exponent does.  Logarithms were particularly useful in long distance navigation and astronomy whose calculations involved trigonometric functions.

In addition to publishing his impressive tables of logarithmic calculations Napier also found other ways to make mathematical calculations easier.  He invented what is called the Napier bones, a manually-operated calculating devise used to calculate products and quotients.

1608: The Refracting Telescope

A refracting telescope
A Refracting Telescope
(Credit: Wikimedia Commons)

One of the most remarkable phenomenon to ever capture the imagination of the human mind over the course of history are those tiny, visible glimmers of light that appear in the night sky. As we know and did our distant ancestors, those lights appear static each night but will rotate around the Earth. Except a few of them, the planets – from the Greek word meaning wanderer – and the Moon moved about more quickly. People wondered: what exactly were these lights up there and what were they doing? Early astronomers grouped them as constellations. Early religious leaders evoked them as Gods. They did, after all, seem to possess special powers as their positions could predict certain times of the year, such as a harvest. Their ultimate mystery was shrouded in the fact that they seemed to be too far away. An instrument needed to bring them into sharper focus was needed explain them. In the early 17th century that instrument came into existence and changed forever how humans viewed their place in the universe.

A Convergence of Lenses and Optics

The optical effects of lens were known about in antiquity.  Archeological evidence suggests that their use was abundant and spanned large geographical areas over several millennia.  They were used for a variety of situations: reflect and refract light, for simple magnification, and even as optical illusions.  Simultaneously characteristics of light were slowly being illuminated in antiquity. In the 2nd century the Greek scientist Ptolemy wrote about the properties of light in his treatise called Optics.  The convergence in the knowledge of optics and lens would lead to the invention of the refracting telescope.

Diagram of a Refracting Telescope
Diagram of a Refracting Telescope
(Credit: Wikimedia Commons)

The first evidence for what later was to be called the telescope was the submission of a patent to the Dutch government in 1608 by Hans Lippershey, although it is likely that the idea was hit upon earlier by other lens makers.  In any case, word of this new invention spread rapidly across Europe. One year following Lippershey’s patent Galileo Galilei improved on Lippershey’s design.  He used it to make his momentous astronomical discoveries that he published in a short book called The Starry Messenger in 1610.  Galileo’s observations through his telescope forever changed our view of the solar system.  

Lippershey’s and Galileo’s telescope is called a refracting telescope since its lenses bend light rather than reflect it.  A refracting telescope is constructed by using two convex lenses to bend light and form the image.  It works by having what’s called an objective lens at one end of a long tube to gather light.  The light is focused through the tube towards the lens at other end called an eyepiece, which magnifies and focuses the image on your eye.  Galileo’s initial telescope had a magnification power of around 8x.  This model was quickly improved to around 20x for the observations recorded in The Starry Messenger.  The most powerful telescope he ever designed totaled a length of 3 feet 3 inches and magnified objects around 30x.  

Technological improvements in magnification and clarity continued to accelerate in the decades to come, expanding the boundaries of the visible universe.  While Galileo used concave lenses in this telescope, Johannes Kepler designed an improved telescope using two convex lens that allowed for a much larger field of view and caused less eye strain.  However this approach inverted the image.  Eventually Issac Newton decided it would be better to make a telescope from mirrors rather than lens, thus inventing the reflecting telescope.  This type of telescope would prove to be superior to the refracting telescope and is the dominate telescope design in modern astronomy.  

Galilean Telescope
Galilean Telescope
(Credit: Wikimedia Commons)

The Historic Impacts of the Telescope

The impacts of the telescope were immediate and immense.  Observation with a telescope made clear that the universe was far, far larger than anybody had previously imagined.   Those tiny, visible glimmers of light in the night sky that were once numbered in the hundreds are today numbered in the trillions.  At the same time it removed humanity from its center and made our role in the cosmos feel much smaller.  It removed the idea of perfection from the cosmos.  Valleys and mountains could now be observed on the moon and planets, which were previously thought to be perfectly spherical.  

Modern telescopes have far more capabilities than the telescopes of the 17th and 18th centuries. In addition to superior magnification they can detect heat, x-rays, radio waves and more. One day in this future the telescope maybe finally answer the question of whether or not we are alone in the universe.

Continue reading more about the exciting history of science!

Galileo Galilei

Galileo Galilei (1564 – 1642) was famously placed on house arrest by the Catholic church inquisition for his astronomical discoveries that disagreed with the accepted church dogma of the time.  It would prove to be a defining moment in scientific history as the old superstitious religious cosmology was being overthrown and humanity was thrust into the modern scientific era.

Portrait of Galileo Galilei
Galileo Galilei

Philosophy [nature] is written in that great book which ever is before our eyes — I mean the universe — but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. The book is written in mathematical language, and the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth.  – Galileo Galilei

Ironically as a boy Galileo was tempted by the monastic lifestyle but was persuaded by his father to study medicine at the University of Pisa, where he later became a professor of mathematics.  Throughout his life he experimented with the physics of objects and devoted himself to the study of astronomy, all the while making revolutionary discoveries.  He demonstrated experimentally that objects of any mass will all fall to the ground (or accelerate) at the same rate and that projectile objects fly through the air in a parabola.  He experimented with pendulums and showed that the time of the swing is always the same regardless of the length of the arc, which turned out to be due to the conservation of kinetic energy in the pendulum.

His most important discoveries turned out to be astronomical.  After improving the magnification by about 10 fold on a spyglass originally made by Dutch lensmaker Hans Lippershey, Galileo turned his attention to the sky and made his revolutionary discoveries.  He saw sunspots on the sun, craters and valleys on the moon, noticed four moons revolving around Jupiter, observed additional stars in the night sky, and observed the phases of Venus from which he deduced that the planet revolved around the Sun.  These discoveries and observations forever changed our view of astronomy and ushered in a the modern scientific age of astronomy.