Montshire Minute: Atoms

Originally aired during the week of April 15, 2002

Monday

The idea that everything is made up of atoms has been around since at least the 5th century BC. It wasn't until the 1800s that scientists began coming up with more detailed ideas about what atoms are like. Atoms might be too small to see, but scientists like the British chemist John Dalton found it logical to believe that each substance was made of specific particles unlike those found in other substances. Scientists create models to explain things they can't see, and the atom model helped explain the results scientists like Dalton were recording. There are 90 naturally occurring kinds of atoms on the periodic table. Scientists have been able to make many other kinds in the lab.

Tuesday

Atoms are the basic building blocks of matter that make up everyday objects. A desk, the air, even you are made up of atoms! A British physicist named Ernest Rutherford explained a lot about the nature of atoms through an experiment that consisted of little more than a thin sheet of gold foil and a lump of radium inside a block of lead. Rutherford directed a beam of the radioactive material at the screen of gold foil. As expected, most of the particles passed through the foil in a more or less straight line. But some particles were deflected in all directions. It was like firing bullets at a piece of tissue paper and finding some of them bouncing back. From this, Rutherford reasoned that particles passing through the foil without being deflected traveled between gold atoms, while the deflected particles bounced off the positively charged centers of gold atoms.

Wednesday

Atoms are about 4 to 16 billionths of an inch across. A human hair could be a million times wider than an atom. Even wavelengths of ordinary light, tiny as they are, are thousands of times wider than an atom, making it impossible to use visible light to view atoms through a microscope. Scientists now use scanning tunneling microscopes (STMs), which are really computerized laboratory tools, not microscopes as we think of them. Scientists can use the STM to "move" atoms with tiny electrical currents, much the same way you move a pin on the opposite side of a pane of glass using a magnet. A few years ago, Carl Wieman and Eric Cornell, two scientists from the University of Colorado in Boulder, created an image of a small mass of atoms.

Thursday

All matter is made up of atoms. But how do we know atoms exist if we can't see them? Well, new technology does allow us to see them, in a way. Two scientists in Colorado recently made a computer generated picture of atoms by cooling them to a temperature just a bit above "absolute zero," which is 459 degrees Farenheit below zero. At this temperature, an atom's speed slows down so much it becomes nearly motionless. The computer image came from a few thousand atoms bunched together inside a nearby vial. For a few seconds, these atoms had combined to form a new state of matter that was, perhaps, the coldest place ever to exist in the universe. The matter was named a Bose-Einstein condensate, a particle that, decades ago, Albert Einstein predicted was possible to create.

Friday

If atoms are the smallest unit of matter, what are atoms made of? Scientists believe that protons and neutrons, which make up the nucleus of atoms, are themselves made of even smaller electrically charged particles called quarks. In the same way that scientists created models of atoms years ago, they are now creating theoretical models of quarks. A few years ago, scientists in the Fermi National Accelerator Laboratory announced the discovery of the subatomic particle called the top quark, the last undiscovered quark of the six predicted. Scientists worldwide had sought the top quark since the discovery of the bottom quark at Fermilab in 1977. The name "quark" came from a quotation in James Joyces' Finnegan's Wake, and was chosen by Murry Gell-Mann who first proposed the existence of quarks in 1963.