Billion Tons Hydrogen "Burned" To Helium By The Sun:
Mass Lost By The Sun (In Million Tons):  
             As it shines,  the sun is getting lighter! Almost everybody knows Einstein's famous equation, E = m·c^2 . But what does that formula actually tell us? It tells us, that energy - E - and matter (mass) - m - are not as neatly separated as our daily experience has us believe. Matter can be transformed into energy - and vice versa, too! The factor c that connects the two is the velocity of light. According to Einstein's formula, matter actually contains a tremendous amount of energy. The energy of the atom bomb that destroyed Hiroshima could be released from less than one gramm of matter! However, matter is not converted to energy in everyday situations. It doesn't happen in a fire, in a furnace, in a conventional, or even a nuclear fission power plant. In everyday processes and transformations, energy in its different forms (e.g. electrical, heat or kinetic energy) and mass are always neatly conserved and do not mingle with each other. Even in nuclear fission reactions, mass is a constant. It is only during nuclear fusion that matter is transformed to energy. If four hydrogen nuclei fuse to form helium (the stuff that makes balloons fly and turns your voice squeaky), the resulting helium nucleus is a bit lighter than the hydrogen. This mass difference has been turned to energy and released in the form of photons. Fusion occurs only under extraordinary circumstances: in a so-called plasma, at extremely high temperatures and pressures. Conditions like that are found in the inner core of the sun and many other stars. The left side shows the mass (in tons) lost by the sun. The right side shows how much hydrogen is "burned" to helium.
This phantastic amount of energy, radiated into space by the sun during a single second, would be plenty to cover the needs of mankind for about a million years - if it could somehow be "syphoned off" and stored. As it is, we have to make do with whatever small percentage of it arrives at the earth's surface.
For comparison:1 billion tons - that`s the weight of a cubic kilometer of water, or about 300 times the New York Central park reservoir!
Fusion is how the sun creates the energy that radiates through space and finally reaches the earth, making life possible on our planet. But wait - does that mean the sun is getting lighter as it shines? Indeed. By fusion, the sun "burns" about 564 million tons hydrogen per second, resulting in 559.7 million tons of helium. The loss of mass, about 4.3 million tons per second, is transformed into energy. But don't worry, it's only 0.0000000000000000002 percent of the sun's entire mass. So yes: the sun is constantly "losing weight", though only a little. That weight is turned into energy: as much as about 4 trillion Hiroshima bombs every second.
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