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Re: life finite versus eternal

By: faul in ALEA | Recommend this post (0)
Sun, 06 May 12 8:31 PM | 59 view(s)
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Msg. 07617 of 54959
(This msg. is a reply to 07615 by tryagain)

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tryagain.........the atom is composed of mostly empty space.

Why do you feel the need to take blood away from your brain?


The tutorial simulates diffraction of alpha particles (helium nuclei containing two positive charges) by a thin foil made of gold metal. Opposite the gold foil is a zinc sulfide screen that emits a flash of light when struck by an alpha particle. To operate the tutorial, use the slider to increase the slit width from a range 0.1 to 9.0 nanometers. As the slit is opened to widths greater than 2 nanometers, some of the alpha particles will collide with the gold nuclei causing them to deflect and deviate from the straight path dictated by the alpha particle source.

Geiger and Marsden expected to find that most of the alpha particles travel straight through the foil with little deviation, with the remainder being deviated by a percent or two. This thinking was based on the theory that positive and negative charges were spread evenly within the atom and that only weak electric forces would be exerted on the alpha particles that were passing through the thin foil at high energy.

What they found, to great surprise, was that while most of the alpha particles passed straight through the foil, a small percentage of them were deflected at very large angles and some were even backscattered. Because alpha particles have about 8000 times the mass of an electron and impacted the foil at very high velocities, it was clear that very strong forces were necessary to deflect and backscatter these particles. Rutherford explained this phenomenon with a revitalized model of the atom in which most of the mass was concentrated into a compact nucleus (holding all of the positive charge), with electrons occupying the bulk of the atom's space and orbiting the nucleus at a distance. With the atom being composed largely of empty space, it was then very easy to construct a scenario where most of the alpha particles passed through the foil, and only the ones that encountered a direct collision with a gold nucleus were deflected or scattered backwards.


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The above is a reply to the following message:
Re: life finite versus eternal
By: tryagain
in ALEA
Sun, 06 May 12 7:31 PM
Msg. 07615 of 54959

faul. My problem comes when you take away blood to the brain.

How many atoms are in the human body?

Answer 1

Would you settle for a whole bunch? I didn't think so. The number of atoms in one person is almost too big to write out. But fortunately there's a shorthand system, called scientific notation, that we use instead for writing really BIG or really SMALL numbers. Since huge numbers are generally just estimates anyway, we just use the first few numbers, followed by a code that tells you how many zeros would follow if you wrote it all out. Ok, here it goes. Hydrogen, oxygen and carbon make up about 99% of the average human. I'm going to cheat a little and leave out the other 1%, which is made up of trace elements (that is, stuff there's only a trace of in the body). Then, let's assume an average adult weighs 70 kilograms. Be sure to keep in mind that the following numbers are based on the number of atoms, not percent of body weight (by weight we are mostly oxygen). A 70 kg body would have approximately 7*1027 atoms. That is, 7 followed by 27 zeros:

7,000,000,000,000,000,000,000,000,000

Of that, 4.7*1027 would be hydrogen atoms, which have one proton and one electron each. Another 1.8*1027 would be oxygen, which has 8 protons, 8 neutrons and 8 electrons. There are 7.0*1026 carbon atoms, which have 6 protons, 6 neutrons and 6 electrons. Now, let's add that all up:
Protons Neutrons Electrons
Hydrogen 4.7*1027 0 4.7*1027
Oxygen 1.4*1028 1.4*1028 1.4*1028
Carbon 4.2*1027 4.2*1027 4.2*1027
Total 2.3*1028 1.8*1028 2.3*1028

Well, you'll have to agree that really is a whole bunch.

http://education.jlab.org/qa/mathatom_04.html


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