### Re: What fraction of the total known mass of the universe does the earth compri

Date: Mon Sep 13 20:33:49 1999
Posted By: David Taylor, Staff, programming, Testronics
Area of science: Astronomy
ID: 936985519.As
Message:
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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

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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