Archives of Ask A Scientist!
About "Ask A Scientist!"
On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.
Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.
Now I will try to give a more complete answer regarding what is going on. In order to do this, I need a few concepts, which I will introduce now. Light can be thought of as being made up of particles called photons. These photons have different energy for all the different colors of light. Red light has a smaller energy than violet light because red light has a longer wavelength. Ultraviolet light has a shorter wavelength and more energy per photon than any kind of visible light. In general the energy of a photon is proportional to 1/wavelength.
The next concept we need to understand is that atoms can emit light through electronic transitions. This happens when an electron that is not in the lowest possible energy configuration, 'jumps' to the lower energy state. When this happens the atom emits a photon, the color of which corresponds to energy of the jump or transition.
With these two concepts in hand we can return to the diamond. Diamond is a crystal form of carbon. Crystals are simply a regular, predictable arrangement of atoms. This regular arrangement of atoms gives rise to many special properties. In certain crystals, including diamond, the atom's arrangement and electrical interactions give rise to a forbidden range of energies where transitions are not allowed. Pure diamond is clear because the forbidden energy range includes the energies which correspond to photons in the visible range. Because the visible light cannot be absorbed it passes though and the diamond is clear. All visible color in diamonds is therefore due to impurities which create isolated energy levels in this forbidden range via their electrical presence. When the crystal fluoresces, what happens is that an electron in a low energy state absorbs a photon and ends up in a higher energy state. It then loses some of that energy to processes that generate heat. Finally, it gives up its remaining energy to a photon in the visible range, which is the light that you see, when it glows.
- How is calcium measured in bone? (without using blood, as this applies to a forensic anthropological question). And, what is the procedure or method of doing so? Is there any special tools, or devices needed?
- In Einstein's equation, E = mc2, he says that the energy released by an object is equal to the object's mass times the speed of light squared. Why is the speed of light a factor in determining energy release?
- My instructor told me that the wavelength of laser light is determined by the distance between the mirrors in the laser device. I say he is not correct, it is the nature of the lasing medium itself as the molecules that make it up emit characteristic wavelenghts when excited. Which of us is correct?
- How do you make a rock into a metal or a crystal?
- I've heard that due to the massive amount of empty space in and between atoms, people could walk through a brick wall. How true is this from a scientific point of view?
- Is it possible to use electrolysis or another method to separate NaCl into sodium and free floating chlorine gas?
- If hydrogen and oxygen are both flammable why doesn't water burn?
- Why do stars twinkle?
- Why do ships float? Why don't ships sink?
- Why does each snowflake have a different shape?