April 24 – Quantum Revolution Time!!

Posted on April 24, 2018

Can you imagine a world without GPS? Without smart phones? Without the internet? Without computers?

I can actually remember the world without most of these things - and although computers were invented before I was born, the computers that existed during my childhood were so few and so so so so so so different from the computers now, I'm going to say that I remember the world without ANY of these things!

But I'm glad we have all of those things now!

All of these technologies are made possible by quantum physics (aka quantum mechanics). And quantum physics got its start on this date in 1914, when the results of an experiment were presented to the German Physical Society. Because the scientists who designed the experiment were named James Franck and Gustav Hertz, the experiment is called the Franck-Hertz experiment.

What is the key idea of quantum physics that was presented in that paper? It is that atoms have only certain energy levels that are possible for electrons. 

You might already know that atoms have a central nucleus formed by protons and neutrons, plus an outer cloud of electrons. 

One possible way for atoms to exist would be for the electrons to be just anywhere, like an informal gathering around a street performer. A lot of scientists thought this might be how atoms worked.

Another possible way for atoms to exist would be for electrons to only be allowed in certain places - and not allowed in others. This would be akin to a stadium or planetarium, where there are certain individual seats and

nobody is allowed to sit in the aisles or cluster in the front or back for safety reasons. In 1913 physicist Neils Bohr proposed this model for the atoms. And the Franck-Hertz experiment proved his model correct!

Learn more about the quantum nature of atoms in Quantum Physics for Kids.

Light and other forms of electromagnetic radiation
also have a quantum nature rather than being, as
people sorta-kinda assumed, a continuous ray
of energy. Find out more about that here.

Also on this date:

Demography pioneer John Graunt's birthday

Poetry and the Creative Mind Day

Concord Day in Niger

Anniversary of the launch of the Hubble Space Telescope

Anniversary of the publishing of America's first newspaper

Anniversary of the opening of the Woolworth Building

National Pigs in a Blanket Day

Armenian Genocide Remembrance Day

Pay It Forward

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• April holidays
• April birthdays
• Historical anniversaries in April

And here are my Pinterest boards for:

• May holidays
• May birthdays
• Historical anniversaries in May
  
  
  
  

October 7 – Happy Birthday, Niels Bohr

Posted on October 7, 2013

What can I say about a man who—while fleeing from the Nazis himself—refused his flight to safety until he made sure that other Danish Jews would have a place to go, as well?

Well, for one thing, I can say that he was a hero!

Niels Bohr was a famous scientist who contributed a lot to our knowledge about atoms and about quantum physics. Born on this date in 1885 in Copenhagen, Denmark, hen Bohr was just 20 years old, he won a gold medal competition in physics. In order to enter this competition, he had to use his dad's physiology lab because Bohr's university had no physics laboratory! Also, Bohr had to learn how to blow glass so he could create the kind of test tubes that he needed. When it came to actual assigned experiment, Bohr went above and beyond what the contest required—which is no doubt why he won! Much later in his career, Bohr won the highest prize in science: the Nobel prize.

As fascinating and important as Bohr's scientific career is, I find it interesting that he was so helpful in rescuing people during World War II. He gave Jewish scientists who were worried about Hitler temporary jobs at his institute, thus providing them financial support; he also arranged for many to receive fellowships from the Rockefeller Foundation, and he helped the scientists find permanent jobs elsewhere in the world, far from Europe.

After Hitler invaded Denmark, when it looked like Jewish people were about to be arrested and deported, Bohr was taken out of Denmark on a boat and carried off to safety in Sweden. As soon as he stepped foot in Sweden, Swedish government officials informed him of their orders to get him safely to the United States so he could work on an atomic bomb project. However, Bohr was worried about all the Jews in Denmark who were not important physicists. He refused to go anywhere until the Swedish king announced on radio and in newspaper that Sweden would take in all the Danish Jews—that they would have a new home in Sweden. Eventually Bohr made this plea in person to Sweden's King Gustaf—and Sweden did indeed take in around 7,800 Jewish Danes.

(Some historians believe that, even without Bohr's efforts, Sweden would have taken in the refugees. But other historians say that Bohr's personal plea made a huge difference in how these events played out.)

Last (and certainly least), Bohr was even able to save two scientists' Nobel medals from the Nazis (who would have undoubtedly melted them down)! Bohr directed that the medals be dissolved in acid! I know you are wondering why dissolving a gold medal in acid is better than melting a gold medal down into a lump—but the Nazis would have that gold lump to pay for weapons and ammunition. Whereas, after the war, the scientists were able to precipitate the gold from the acid and have the Nobel committee re-strike their medals. Good as new!

Back to Atoms...

Check out this YouTube video of the structure of an atom. (Note: This super-simple look doesn't get into the quantum realities that Bohr worked out.) 

This video is a more advanced look at Bohr's model of the atom. 

Here is a Nova special on quantum physics, the field that Bohr helped start. 

Also on this date:

World Smile Day

Anniversary of the invention of the bar code

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• October holidays
  
• October birthdays
  
• Historical anniversaries in October
  

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• November holidays
• November birthdays
• Historical anniversaries in November

November 7, 2010

Happy Birthday, Marie Curie and Lise Meitner

Two different eminent female scientists who did important pioneering work in the field of radioactivity were born on this day. Curie was born Maria Skłodowska in 1867, in Warsaw, Poland (at the time Warsaw was part of the Russian empire); most of her adult life and work were in France. Meitner was born in Austria in 1878, and (because she was Jewish) she later had to flee from the Nazis and ended up in Sweden.

Curie and her husband Pierre did experiments on uranium minerals and discovered two new elements, polonium and radium. Curie won two different Nobel prizes for her work (in Physics and Chemistry)—the first person in the world ever to win two, and still the only woman to win in two different fields. She coined the word radioactivity, invented techniques for isolating radioactive isotopes, and even did the world's first studies on radiation treatment of cancer. Sadly, she died from radiation poisoning.

As we learned yesterday, curium (atomic number 96) is named for Marie and Pierre Curie.

Meitner and her colleague Otto Hahn discovered nuclear fission. Although Hahn received a Nobel prize for the discovery, Meitner was overlooked—an omission that many people think was terrible. Meitner and Hahn's work explained why fission released energy, exactly how uranium breaks down into lighter elements, and why no stable elements heavier than uranium exist in nature.

The element meitnerium (atomic number 109) is named for Meitner.

Learn about nuclear physics!

Atoms are basically made up of heavy particles called protons and neutrons, which are found in the center (or nucleus) of the atom, and a surrounding cloud of teensy, almost weightless particles called electrons. A particular element is defined as having a certain atomic number, which is the number of protons that element has.

If an atom of a particular element loses or gains an electron or two, it is called an ion.

If an atom of a particular element has more or fewer neutrons than usual, it is called an isotope.

But if an atom of a particular element loses or gains a proton—it becomes another element!

• Check out this wall chart. Click on sections to see the details and read the text!  Then use the online teacher's guide to the wall chart to find out more. 

• For even more, use the Experiments section of the “ABCs of Nuclear Science.” 

• For more on Marie Curie, see this earlier post (scroll down). 

February 27, 2010

Science Celebrations Today! On this date in 1813, President James Madison signed into law a Congressional “Act to Encourage Vaccination.” On January 21, we commemorated the introduction of the smallpox vaccine and mentioned that Edward Jenner, whose work led to the eradication of smallpox, is credited by some experts with saving more lives than anyone else in history. Well, today we celebrate government support of vaccinations (and other preventative health care measures that really work!). This act was the first U.S. program in the young nation's history to improve the health of the general populace. It not only “encouraged” people to get vaccinated against the dreaded disease, it established a safe, uncontaminated supply of vaccine, subsidized distribution of the vaccine, and appointed a National Vaccine Agent. Virtual Vaccination! Someone in charge of the Preteen Vaccine Week of 2008 created a Microsoft Word document that details an interesting simulation activity about vaccines. There are a few aspects that are a bit cheesy, but the discussions and decisions suggested here seem very valuable. Since it's a document, I couldn't seem to link directly to it...but you can download the document by choosing the first item in this Google search.

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On this date in 1932, Dr. James Chadwick discovered the neutron. This is the particle in the nucleus (center) of atoms that is similar in size (mass) to the positively-charged proton, but that has no electrical charge. (Chadwick named it neutron because something with no charge is “neutral.” In the diagram here, the neutrons are green.) His discovery was no accident, no surprise. Chadwick reviewed others' work and thought there must be a particle as large as a proton but electrically neutral, and he ran experiments specifically designed to detect it. Chadwick won a Nobel Prize for his discovery. Charge up with Math! A proton is made up of 2 Up quarks and 1 Down quark. A neutron is made up of 2 Down quarks and 1 Up quark. An Up quark has a 2/3 positive charge. A Down quark has a 1/3 negative charge. Can you come up with equations that shows how much charge a proton has, and that shows why a neutron has no charge? Learn more about atoms at the Jefferson Lab website. Older kids might enjoy a more detailed look provided by Particle Adventure.

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On this date in 1940, Martin Kamen and Sam Ruben discovered carbon-14. A carbon-14 atom is a rare variation (or isotope) of carbon that has two more neutrons than the usual carbon atom. It basically behaves like normal carbon but is a little bit heavier. It's also radioactive, and it slowly decays, changing into nitrogen-14. There is always a tiny amount of carbon-14 in the atmosphere, along with a whole lot of normal carbon, in a gas called carbon dioxide. As long as plants are alive, they take in carbon (a tiny amount of carbon-14 and a whole lot of normal carbon) and use it to make leaves and fruits and seeds and roots. Animals, including people, eat plants or the animals that eat the plants and get carbon in their bodies, too (a tiny amount of carbon-14 along with a whole lot of normal carbon). This means that, as long as plants and animals are alive, they have in their bodies carbon-14 in about the same proportion to normal carbon as every other creature. But when a plant or animal dies, the proportion changes. Remember, carbon-14 slowly changes into nitrogen-14. A dead animals isn't breathing or eating, so it doesn't get any more carbon-14, and the carbon-14 that is already in its body starts to break down, or decay. Measuring the amount of carbon-14 that is still left is key to using carbon-14 to figure out about how long ago organisms died. See the diagram at “How Stuff Works” for a more detailed explanation. Notice that carbon-14 dating only works to figure out dates of biological things like bones, wood, fabric—things that were once living or that were made from once-living things. Also, carbon-14 dating only works to figure out ages of items that are 50 thousand years old or younger. That means it's useful to figure out how old early cave-dwelling human remains are, but it cannot be used to test anything dinosaur-related, since dinos died out about 65 million years ago! Carbon Dating...Simplified This lesson plan uses fun things like gummy bears and popcorn to explore concepts such as half-life and the process of carbon dating. It's written for an entire classroom but could be modified to work with individual students, too. It's high-level stuff but designed to be accessible to Grades 3 to 6.