|MadSci Network: Astronomy|
What fraction (%) of the total known mass of the universe does the earth represent? What percent of the total mass of the earth do [humans] represent? The answer to both questions is: approximately zero. Both questions are asking the same question: What do you get when you divide a number by an immensely larger number? The bigger the difference between the two numbers, the closer the answer gets to zero. REAL LIFE EXAMPLE: One large pizza from Joe's Monster Pizza Shack will feed 4 hungry students. One large pizza from Joe's Monster Pizza Shack will feed 50 hungry students, but everyone will still be hungry. One large pizza from Joe's Monster Pizza Shack will feed the entire student body, but you'll be able to hold your piece on your thumbnail. Question # 2 6 billion people multiplied by 70 kg/person ( guessed average human weight ) is only 420000000000 (4.20 * 10^11) kg. The earth's mass is close to 5980000000000000000000000 (5.98 * 10^24) kg. This means at a rough guess, humans are .000000000007% (7.0 * 10 ^ -14) of the earth's mass. Question # 1 The fraction of the mass of the earth to the universe is both harder and easier to answer. The mass of the universe is not known. But it is huge, and the fraction works out to "nothing". Our sun's mass is close to 1.99 * 10 ^30 kg. And our sun orbits in the milky way galaxy, a medium size star of who knows how many. There are people who have worked out guesses for the approximate mass of our galaxy based on how fast stars appear to be orbiting the center of the galaxy. Suffice it to say, it's huge. And it's only one galaxy in the observable universe. There are many, many galaxies that can be observed... There are certainly many more galaxies that we cannot observe with our present level of technology. Is the universe infinite or is there a limit? That moves closer to a religious question than a scientific one as we really don't have enough information. My guess is the mortal human race as we know it we never will.
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