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Back to His/(s)tory • By the late 19th century a conflict had arisen between geology and astronomy. Geologists had firmly determined that the Earth was extremely old, hundreds of millions, perhaps even billions of years old. But physicists studying the sun could think of no source for the sun's heat except for gravitational contraction, and that would not allow the sun to be so old.
E=mc2 • The mystery remained intact until Albert Einstein derived the surprising equivalence between mass and energy E=mc2as a curious side effect of special relativity theory. That, plus the discovery of radioactivity at about the same time, led to new ideas about the sun's heat.
German-Swiss-German-US American 1879: Birth of little Albert in Ulm, Germany. 1891: Swiss Citizenship 1909: Professor in Zürich 1911: Professor of Theoretical Physics in Prague 1914: Director of the Kaiser Wilhelm Physical Institute Berlin and Professor in Berlin 1914: German Citizenship 1933: Renounced German Citizenship for Political Reasons 1933: Professor for Theoretical Physics at Princeton University 1940: US Citizenship 1945: Retirement from Princeton
Collaboration • Sir Arthur Eddington, Einstein's English champion, who first noticed the mass deficit of helium as compared to hydrogen, and suggested the fusion of hydrogen into helium might be the ultimate source of the sun's power.
Hans Bethe + Martin Schwarzschild • Bethe: 1906 (Strasbourg, Germany) - 2005 Ithaca • gets credit for first quantifying the reality of nuclear fusion as the sun's energy source • Schwarzschild: 1912 (Potsdam) – 1997 (Pennsylvania). • 1958: Structure and Evolution of Stars. The first book to include a complete treatment of nuclear fusion as the source of stellar energy.
Lets get a Space Heater instead? • The core of the Sun is considered to extend from the center to about 0.2 to 0.25 solar radius.It is the hottest part of the Sun and of the Solar System. It has a density of up to 150,000 kg/m³ (150 times the density of liquid water) and a temperature of close to 15,000,000 kelvin (by contrast, the surface of the Sun is close to 6,000 kelvin). The core is made of hot, dense gas in the plasmic state. The core, inside 0.24 solar radius, generates 99% of the fusion power of the Sun.
A Different Kind of Fusion PLEASE • Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy. Fusion is the process that powers active stars, the hydrogen bomb and experimental devices examining fusion power for electrical generation.
Is the Sun really a Green Propaganda Instrument? • Nuclear Fusion in the SUN
de nouveau: Protons repel each other electrostatically because they both have a positive charge. But at extremely close range (like 10-15 meters) they will attract each other, because of the strong nuclear force (usually shortened to strong force). Because of this, the temperature has to get high enough to overcome that repulsion, and push the protons close enough together for the strong force to take over.
on continue … Once that happens, the strong force overpowers the electrostatic repulsion, and pulls the two protons together, initiating proton-proton fusion. This requires temperatures in excess of 10,000,000 Kelvins. When that happens, one of the protons changes into a neutron, and the resultant nucleus of one proton and one neutron is called a deuteron ("d").
The excess positive charge is expelled in the form of a positron (e+). That positron rapidly runs into an electron (e-), and the two anhillate each other into gamma rays (the positron is the anti-matter analog for an electron). The excess momentum is carried away by a neutrino ("nu").
