Day: January 31, 2018

1643: Discovery of the Vacuum

Posted on by Dan

The existence of a vacuum, a space completely empty of matter, had been debated since at least the ancient Greek philosophers, and probably much longer.  In 1643 the Italian physicist Evangelista Torricelli showed that for all practical purposes a vacuum was indeed possible. 

Philosophical Ideas about a Vacuum

Portrait of Evangelista Torricelli
Evangelista Torricelli

The philosophical debate about the existence of a vacuum, or the void as the Greeks may have called it, has been around for centuries. Is there a void or is no void possible? The debate itself was contentious and much doubt surrounded the idea that a vacuum could actually exist. In ancient Greece the idea began with Democritus, born around 460 BCE, who expanded on and synthesized the work of his teacher Leucippus. Democritus proposed that the world was composed of tiny particles moving around in an infinite void which he called atoms. Thus the space in between these particles was empty space, or what we might today call a vacuum. The most influential Greek thinker, Aristotle, made arguments against these ideas in his book titled Physics. The phrase “horror vacui” (nature abhors a vacuum) is attributed to Aristotle.

Given what we know of the influence of Aristotle over Medieval thinking it is no surprise that the idea of a vacuum fell out of favor during Medieval times. The rejection of a vacuum was restated time and again up until the time of Galileo Galalei.

An Accidental Discovery

Evangelista Torricelli was born in Faenza, Italy in 1608 to a relatively poor family. His father was a textile worker but he had to good sense to realize the extraordinary intellectual talents and abilities of his oldest child. Lacking the resources to provide his son with a proper education he send him to his Jesuit uncle where he was to receive his education at the Jesuit College in Faenza, then later in Rome where he studied science under the Benedictine monk Beneditto Castelli. Castelli was a student of Galileo, a figure who inspired Torricelli’s in his mathematical and scientific career included his experimental verification of a vacuum.

Late in his life, Galileo became preoccupied with the observation that well diggers suction pumps could only raise water about ten meters. In 1640 Galileo, along with his two assistants Torricelli and Giovanni Baliani, conducted a suction pump experiment at a public well. In every instance, no matter what they tried, the water would not rise more than 9.7 meters about the level of the well water. Galileo incorrectly surmised that a force created by a vacuum was preventing the water from rising any higher.

Torricelli discovered the vacuum accidentally when he was conducting experiments that were designed to solve the problem of pumping water out of a deep well.  He tried to scale down the problem using mercury instead of water because liquid mercury is much more dense than water and he hoped to be able to observe the same phenomenon at a lower height.  He took a tube closed at one end and filled it with mercury.  He stuck the open end in a bowl of mercury and slowly raised the closed end, where eventually a gap appeared above the mercury.  The gap could not have been air because when he lowered the tube again the gap vanished immediately, quicker than air could have dissipated. The gap above the mercury was the first experimentally verified vacuum.

Evangelista Torricelli’s Experiment that Led to the Discovery of the Vacuum

As to the problem of rising water and mercury above a certain level, Torricelli proposed the correct answer. It is that the mercury was rising due to the atmospheres weight (or atmospheric pressure) pressing down on the mercury in the dish. He correctly predicted that height of the mercury column would vary from day to day as the atmospheric pressure also changed. In effect, he invented the apparatus known today as the barometer.

Modern Uses of Vacuum Technology

The discovery of the vacuum was eventually applied to advances in technology and its principle many different industries today. One of the most common uses is in the food industry, where vacuum technology is used in the transport, processing, and packaging of food, and in bottling of beer and soft drinks. It prolongs the shelf life of food and maintains its nutritional content. Vacuum technology is used in the chemical industry to treat and purify reactants and products. Other applications of vacuum technology include usage in heating and cooling systems, light bulbs, steam engines, and cathode ray tubes.

Continue reading more about the exciting history of science!

1590s: The Microscope

Posted on by Dan
An Early Microscope
An Early, Crude Microscope

The vast scale of the universe, both cosmic and microscope, is one of the marvels that modern science has revealed. The revelation is the result of the invention of two instruments, the telescope for revealing the cosmic and the microscope for revealing the microscopic. Each of these instruments were invented roughly 500 years ago. Each changed how we thought about our place in the universe.

It is extremely difficult to imagine things on a microscopic scale given the limitations of our human senses. But we can try. Let’s take one example to illustrate the miraculous world of the microscopic. In a single drop of seawater one can find tens of millions of viruses and bacteria. Yet these microorganisms are completely invisible to the naked eye. The invention of the microscope was the instrument that shined a light on the realm of the small.

The Invention of the Microscope

Like many pre-modern inventions, the exact date of the first microscope is disputed, murky, and confused. However it is still possible to shine a light on this inventions beginnings. Credit is most commonly given to Zacharias Janssen and his father Hans Martenz for creating the first microscope as early as 1590, or at least sometime during that decade. 

They were, of course, not the first people to have experimented with enlarging objects. Centuries earlier saw lots of people attempting to magnify objects by means of using water to bend light or by using a very simple lens. However it’s probably safe to say that these methods do not meet the qualifications to what most would consider a microscope.

The important point was the people in the ancient world did come to learn that the best way to magnify an object was by viewing it through a lens. The important breakthrough occurred when several lenses were placed in a tube resulting in significant magnification of objects when viewed through a single lens. By using several lens to magnify an object, the compound microscope had just been invented.

An Improved Microscope
An Improved Microscope

Early microscopes came in a variety of forms ranging from single yet sophisticated powerful lens such as the type that Antony van Leeuwenhoek created and used, to simple compound microscopes such as those created and used by Zacharias Janssen, Galileo Galilei, and Robert Hooke.  The term microscope was first used in 1625 to describe one of Galilelo’s instruments that he invented in 1609. Although these microscopes provided increased magnification there were persistent problems with the image quality. The major nagging image issue was called chromatic aberration. It is caused by light passing through the lens at different points and color wavelengths, resulting in a color distortions at the edge of the image. This problem persisted early on due to the relative low quality of glass used combined with flaws in design of the microscopes.

It took about 100 years for significant discoveries to be made with the microscope. This is due to early microscopes having low magnifying power and producing blurry images. The first big breakthrough came with the publication of Robert Hooke’s book Micrographia in 1665. The book dazzled the imagination of the people who read it and naturally sparked an enormous amount of new interest in the emerging field of microscopy. Antony van Leeuwenhoek, a contemporary of Robert Hooke, made some of the most powerful microscopes of the early era. Throughout his life van Leeuwenhoek made over 500 microscopes, which were extremely powerful single lenses as opposed to the compound microscopes that Robert Hooke used.

Modern Microscopes

Today microscopes are available in an even greater variety of forms. By the turn of the 20th century the resolution limit of light microscopes had been reached. This limitation was quickly overcame in 1904 when a UV microscope was invented that had double to resolution of a light microscope. Since that time various types of more powerful microscopes have come onto the scene. One of the most powerful is the electron microscope. First invented in the 1930s, electron microscopes employ beams of electrons rather than light (since the wavelength of electrons is up to 100,000 times shorter than that of light), allowing for significantly greater magnification.

Today’s most powerful electron microscopes allow researchers to see resolutions so clearly that they can view images of individual atoms. Viruses can be viewed at a scale of less than four angstroms, or four ten-billionth of a meter. Resolution of this magnitude provides a powerful tool in advancing the field of microbiology.

Continue reading more about the exciting history of science!

Antony Van Leeuvenhoek

Posted on by Dan
Antony Van Leeuvenhoek portrait
Antony Van Leeuvenhoek

Important advances in microbiology were made by Antony van Leeuvenhoek (1632 – 1723), which include a substantial improvement on the microscope followed by the discovery of a variety of single celled organisms.

Antony Van Leeuvenhoek was for his time an unusual candidate to make breakthrough scientific discoveries.  He earned no university degrees and therefore had no formal scientific training, and he was not particularly wealthy.  His trade was that of a textile merchant that led him to develop improved lens in order to better observe thread quality.  He cultivated in himself a tremendous skill in lens making with some of his lens being able to magnify up to 300 times and possibly higher, which was a significantly higher level of magnification than the compound microscopes of his day that only magnified around 20x – 30x.  During his lifetime he may have made over 500 magnifying lenses.

He used these lenses, along with his terrific eyesight and observational skills, to observe the first bacteria.  Through a friend he communicated with the Royal Society through dozens of informal letters, and although the Society was originally skeptical of his claims they were later verified by Robert Hooke and others. This led to his election into the Royal Society in 1680 and bestowed on him a tremendous amount of fame.

1665: The Cell

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The observation by Robert Hooke in 1665 of what became coined the cell provided the starting point for a sequence of discoveries at the microscopic level. A rapid pace of discoveries quickly followed and has continued into our present time. From this moment onward our view of life has been revolutionized.  But while it was Hooke who observed the cell by viewing thin layers of cork, it was Antony Van Leeuwenhoek who can be considered as the first microbiologist and dramatically expended our view of cellular life. 

The Discovery of the Cell

Rendering of a Cork Cell as seen by Robert Hooke; Micrographia, 1665
Rendering of a Cork Cell as seen by Robert Hooke
(Credit: Micrographia, 1665)

The invention of the microscope in 1608 allowed for the discovery of the cell. Microscopes had been around for about a generation or so before Hooke began making and using his own instruments. By this time microscopes were very rudimentary, but Hooke’s had a technical supremacy in that it could magnify by up to 40x to 50x making it the best of its time. In 1663 and the following year Hook began making his microscopic observations. In 1665 he published his work in a book titled Micrographia. It was the first major publication of the Royal Society.

Meanwhile in Antony Van Leeuwenhoek was living in the Dutch Republic working as a textile worker. He was not a formally trained scientist at the time and was largely a self-taught man. He came across Micrographia and was fascinated by what he read and saw in it. He was already proficient in lens making and in the 1670s he started observing microbial world. He developed terrifically powerful microscope – ones that could magnify up to 270x. To the dismay of many was highly secretive about his techniques. Over the course of Van Leeuwenhoek ‘s career he made almost 200 reports to the Royal Society – offering facts of his findings including drawings. Leeuwenhoek began his work by analyzing drops of pond water. He also went to work on replicating some of Hooke’s earlier observations. In 1676 he to some of this tooth plaque and saw there were thousands of what he called living animalcules because they were moving like little animals. He had discovered bacteria.

A Wondrous Biological Factory

Contained in the cell are the structural and functional operations of a living organism, making it the basic building block of life.  All cells follow a similar basic plan. The cell membrane is the outer most layer of the cell and is composed of a mixture of lipids and proteins.  Inside the cell is whats called the cytoplasm, which is a complex mixture of water, salts, enzymes, and other organic molecules or organelles. The cytoplasm includes the cell nucleus which contains the cells genetic material.

The inside of a cell is a busy place.  That activity that happens there can be mind boggling. A cell is made up of millions of objects performing a multitude of tasks.  Millions of chemical reactions are taking place inside each cell.  Enzymes, which are a specific type of protein, perform up to a thousand tasks per second.  Some proteins exist for a short of thirty minutes, others for up to weeks.  Each cell contains up to 20,000 different proteins.  These proteins can be made up of up to 50,000 molecules.  This means each cell can be made up of hundreds of millions of chemical molecules, a staggering amount of chemical activity. 

Most of the food we eat and oxygen we breath are taken to the mitochondria, where it is converted into a form of energy called ATP.  A typical cell in each human body will contain about a billion ATP molecules.  In a matter of minutes all of these molecules will be used up, and another billion will have replaced them.  Each day every person produces about half of their weight in ATP.  This weight mostly comes from the air that we breath. 

From Cell Discovery to Cell Theory

The discovery of the cell lead to the elucidation of a core theory in biology called cell theory, which roughly states that all living organisms are made from basic units called cells that continually reproduce. It would take another 150 years after the discovery of the cell for cell theory to become established.

Critical work in advancing cell theory began in the early 19th century. In 1838 Matthias Jakob Schleiden was working with plants and concluded that all plants are made up as cells. This influenced the German physiologist Theodor Schwann and the next year he published Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants, a landmark work where he proposed his own Cell Theory.

Continue reading more about the exciting history of science!