TPO 8 Lecture 3 History
Pro：So we've been talking about the printing press. How it changes people's lives, ** books more accessible to everyone. More books mean more reading, right? But, as you know, not everyone has perfect vision. This increasing literacy, um, in reading, led to an increasing demand for eye glasses. And here's something you probably haven't thought of. This increased demand impacted the societal attitudes toward eye glasses. But, first let me back up a bit and talk about vision correction before the printing press. And, um, what did people with poor vision do, I mean, especially those few people who were actually literate? What did they do before glasses were invented? Well, they had different ways of dealing with not seeing well. If you think about it, poor vision wasn't their only problem. I mean, um, think about the conditions they lived in：houses were dark, sometimes there weren't any windows; candles were the only source of light. So in some places, um, like ancient Greece for example, the wealthiest people with poor vision could have someone else read to them- easy solution if you could afford it. Another solution was something called a “reading stone”. Around 1000 C.E. European monks would take a piece of clear rock, often quartz, and place it on top of the reading material. The clear rock magnified the letters, ** them appear larger, um, looks like what happens when a drop of water falls on something, whatever 's below the drop of water appears larger, right? Well, the “reading stone” works in a similar way. But rocks like quartz, well, quartz of optical quality weren't cheap. Late in the 13th century, glass maker in Italy came up with a less expensive alternative. They made reading stones out of clear glass. And these clear glass reading stones evolved into the eye glasses we know today. So we're pretty sure that glasses were invented about the late 1200's, well, over a hundred years before the printing press. But it's not clear who exactly invented them first or exactly what year. But record shows that they were invented in both Europe and China at about the same time. By the way, we call this “independent discovery”.
Independent discovery means when something is invented in different parts of the world at the same time and it's not as unusual as it sounds. You can look at the timeline chart at the back of your textbook to see when things were invented in different cultures at about the same time to see what I'm talking about.
So now let's tie this to what I've said before about societal attitude towards glasses. Initially in parts of Europe and in China, glasses were a symbol of wisdom and intelligence. This is evidence in an artwork from the period. European paintings often portrayed doctors or judges wearing glasses. In China, glasses were very expensive. So in addition to intelligence, they also symbolize affluence, um, wealth. In 14th century Chinese portrays the bigger the glasses, the smarter and wealthier this object was. So glasses were a steady symbol in some parts of the world. Now let's go back to the invention of the painting press in 1440. What happened? Suddenly, books became widely available and more people wanted to read. So the need, oh well, actually not only the need but the demand for more affordable glasses rose drastically. Eventually, inexpensive glasses were produced, and then glasses were available to everyone. People could purchase them easily from a traveling peddler.
TPO8 Lecture 4 Chemistry
Pro：So, are there any questions?
Stu：Yes, um, Professor Harrison, you were saying that the periodic table is predictive. What exactly does that mean? I mean I understand how it organize the elements but where's the prediction?
Pro：Ok, let's look at our periodic table again. Ok, it is a group of elements in the categories that share certain properties, right?
Stu：Um-huh~
Pro：And it is ranged according to increasing atomic number, which is…
Stu：The number of protons in each atom of an element.
Pro：Right, well, early versions of the periodic table had gaps, missing elements. Every time you had one more proton, you had another element. And then, oops, there have been atomic number, for which there's no known element. And the prediction was that the element, with that atomic number existed someway, but it just haven't been found yet. And its location in the table would tell you what properties that you should have. It was really pretty exciting for scientists at that time to find these missing elements and confirm their predictive properties. Um, actually, that reminds other, other very good example of all these, element 43. See on the table, the symbol for element 42 and 44. In early versions of the table, there was no symbol for element 43 protons because no element with 43 protons had been discovered yet. So the periodic table had gap between elements 42 and 44. And then in 1925, a team of chemists led by scientist named Ida Tack's claimed they had found element 43. They had been using a relatively new technology called X-ray spectroscopy, and they were using this to examine an ore sample. And they claimed that they'd found an element with 43 protons. And they named it Masuria.
Stu：Um, Professor Harrison, then, how come in my periodic table, here, element 43 is Tc, that's Technetium, right?
Pro：Ok, let me add that.
Actually, um, that's the point I'm coming to. Hardly anyone believed that Tack's discovered the new element. X-ray spectroscopy was a new method at that time. And they were never able to isolate enough Masurium to have available sample to convince everyone the discovery. So they were discredited. But then, 12 years later in 1937, a different team became the first to synthesize the element using a cyclotron. And that element had…
Stu：43 protons?
Pro：That's right, but they named it Technetium to emphasize that it was artificially created with technology. And people thought that synthesizing these elements, ** it artificially was the only way to get it. We still haven't found it currently in nature. Now element 43 would be called Masurium or Technetium is radioactive. Why is that matter? What is true of radioactive element?
Stu：It decays it turns into other elements. Oh, so does that explain why was missing in periodic table?
Pro：Exactly, because of radioactive decay, element 43 doesn't last very long. And therefore, if that ever had been present on earth, it would decay ages ago. So the Masurium people were obviously wrong, and the Technetium people were right. Right? Well, that was then, now we know that element 43 does occur naturally. It can be naturally generated from Uranium atom that has spontaneous split. And guess what, the ore sample that the Masurium group was working with had plenty of Uranium enough to split into measurable amount of Masurium. So Tack's team might very well have found small amounts of Musurium in the ore sample just that once was generated from split Uranium decayed very quickly. And you know here's an incredible irony, Ida Tack, led the chemist of that Musurium team, and were she the first to suggest that Uranium could break up into small pieces but she didn't know that that was the defense of her own discovery of element 43.
Stu：So is my version of periodic table wrong? Should element 43 really be called Musurium?
Pro：Maybe, but it's hard to tell for sure after all this time, if Ida Tack's group did discover element 43. They didn't, um, publish enough details on their method or instruments for us to know for sure. But I'd like to think element 43 was discovered twice. As Musurium, it was first element to discover that occurs in nature only from spontaneous vision, and as Technetium, it was the first element discovered in the laboratory. And of course, it was an element the periodic table let us to expect existed before anyone had found it or made it.
