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396B Posssibility of Asteroid Hitting Earth (2)
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153. Do negative ions make you feel good?I attended a session on multiple intelligences at a workshop last week. The presenter stated that we feel better when there is an abundance of negative ions in the air. She said that the wind whips up more positive ions and water produces more negative ions. That is why we feel better around water and the wind tires us out. Has anyone heard of this? Do any of you know of any research to support this? Any help would be appreciated. Sounds kind of questionable to me.
Reply  Sounds questionable, indeed. There always exists a small concentration of ions in air, from radioactivity and cosmic rays, maybe sunlight too. The density of positive and negative ions is essentially the same, for when an electron is torn off an atom, where does it go? It either stays unattached, or attaches itself to some molecule--a negative ion in either case.
Unbalanced densities create an electric field. A quiet-time electric field does exist in the atmosphere, produced by distant thunderstorms, and the difference over an altitude of (say) 2 meters may be a few hundred volts. That however can only exist because air is a very good insulator. Your body isn't: an electric charge touching it is soon discharged to the ground.
So, do "we feel better when there is an abundance of negative ions in the air"? Not due to the ions, no. But it could be that a steady electric field requires conditions which are comfortable to the human body, such as low humidity. I wouldn't be able to say.
154. Shape of the Earth's OrbitI am a 9th grade Earth Science Teacher. I am trying to find out further information about the Earth's orbit around the sun as determined by Kepler. I would like the students to draw a north orbital view with the earth at aphelion, perihelion, and put dates on the ellipse to correspond with the months, the solstices and equinoxes. I have found lots of information, but much of it conflicts. I am hoping that I can get more information to satisfy myself as to what the correct configuration should be
ReplyA perspective view of the Earth's orbit is given in "From Stargazers to Starships" at
and of course it looks rather elliptical, because of the perspective. Equinoxes and solstices are represented by their months, and you can add other details.
A perpendicular view of the orbit from north won't display any notable ellipticity: I have seen such a graph, and it looks just like a circle. The only visible concession to ellipticity is that the Sun is displaced from the center. The eccentricity e of the Earth's orbit is 0.01673, which means that the distances of aphelion and perihelion have a ratio 1.01673 to 0.98327, so with a diameter of 10 cm, the Sun is displaced by about 0.8 mm from the center, no more.
An interesting fact, related to the eccentricity of the Earth's orbit, is that spring and fall equinox are NOT exactly half a year apart. That is discussed in section #12A of " ("More on Kepler's 2nd Law") and is related to the fact that we are closest to the Sun around January 4 (sometimes 3 or 5--it varies as the orbit is perturbed). Milutin Milankovich tied this to his theory of ice ages, as described in section #7 on precession.
Other sections related to Earth sciences are #S-1, S-1A and S-1B dealing with weather and climate, and sections dealing with the Earth's magnetism (also with plate tectonics) in "The Great Magnet, the Earth", home page
especially the sections at the end, marked "Of Special Interest to Science Teachers."
(1) Why don't its particles separate by weight?