How much mass is in the universe, and how do they know for sure?
597748
There's no way to know.
824559
Mass is measured in grams.
344825
density is mass divided by volume - so if you know the volume and the density, then you multiply them to get the mass  (which is synonomous with weight)
155835
The problem is to tabulate the total mass of the Universe, a realy BIG problem.  There may be a lot of undetected dark matter in the universe that would shift calculations of the Gravitational Constant that will determine the fate of the Universe.  It is like trying to count the mushrooms in a totally blacked out cellar while blindfolded, or even much harder.  Progress is being made as the limits of the Universe are being explored by every means possible, especially by use of the human brain.
820356
mass = the amount of matter, independant of gravity and in sci units measure in kg's\n\nweight= force, the downward pull on an object due to gravity, measure in N (newtons)
103036
We often use the terms "mass" and "weight" interchangeably in our daily speech, but to an astronomer or a physicist they are completely different things. The mass of a body is a measure of how much matter it contains. An object with mass has a quality called inertia. If you shake an object like a stone in your hand, you would notice that it takes a push to get it moving, and another push to stop it again. If the stone is at rest, it wants to remain at rest. Once you've got it moving, it wants to stay moving. This quality or "sluggishness" of matter is its inertia. Mass is a measure of how much inertia an object displays. \n\nWeight is an entirely different thing. Every object in the universe with mass attracts every other object with mass. The amount of attraction depends on the size of the masses and how far apart they are. For everyday-sized objects, this gravitational pull is vanishingly small, but the pull between a very large object, like the Earth, and another object, like you, can be easily measured. How? All you have to do is stand on a scale! Scales measure the force of attraction between you and the Earth. This force of attraction between you and the Earth (or any other planet) is called your weight. \n\nhttp://www.exploratorium.edu/ronh/weight/
89835
In terms of mass.\nThe SI unit for mass is the kilogram (kg).\n\nDo not confuse mass with weight, they are not the same thing.  The mass of an object is constant throughout the universe where as weight is a vector force that depends on the gravitational field around the object.  It is unfortunate that these two words are used interchangably sometimes.
1059357
Thats why they asked theoretically.\n\nsame radius as the solar system\n1267650600228229401496703205376 kms\n\nOf which you allready knew, otherwise u would not be asking
28023
The observable universe is estimated to contain:\n10^11 galaxies, 10^21 stars, and 10^78 atoms.\n\nThe means 100,000,000,000 galaxies.
559122
how the hell would we know
490259
The mass of earth is found as follows.\n\nThe acceleration due to gravity at a place is g. \ng = G M/R^2, where, G is gravitational constant, which is determined experimentally with two known masses.\n\nR is the radius of earth which we know by surveying the circumference of earth.\n\n M = 9.8 x 6400,000 x 6400, 000x / 6.673x10^ (-11) = 6x10^24kg.\n\nThe mass of Sun is found as follows.  \n\nWe determine the distance of Sun observing their angular diameters measured from different heights from earth. \n\nWe observe its period of rotation about the earth.\n\nNow using the formula ‘M = 4pi^2 R^3/G T^2’, M is found\n\n39.48 x (1.496x10^11) ^ 3/6.673x10^ (-11){365.25x24x60x60}^2= 1.989x10^30 kg.\n\nSince we know the mass of Sun, we can use only the period of rotation to find the mass without knowing the distance.\n\nAbout the mass of stars, I don’t know whether there is some way to find their mass.
1125776
How could we know that?
313486
your answer is in \nhttp://en.wikipedia.org/wiki/Big_Bang
3627
one estimate is about 10^52 kg, that is:\n\n\n100000000000000000000\n 00000000000000000000\n 00000000000000000000\n 000000000000 \nkilograms\n\nWithout about 90% being the "invisible" missing mass stuff.
49086
This is a question that neither science or religion can ever "prove."  In our human capacity, it is unlikely anyone will ever know the answer to this.  How can you even take a scientific approach to this?  You can speculate how the universe appears to be created based off measurements in the space, but you can always ask the question "but what about before that?"  \n\nUltimately it comes down to faith, and I don't necessarily mean in a God.  You have faith that the universe was started somehow.  Either God or some unexplainable cosmic phenomenon that we will never understand.  Or both!
215801
Planets, or other celestial objects' mass may be estimated by its size and its gravitational pull on objects around them. For example, Jupiter has a high mass being the largest planet in our solar system, If a star or sun that went through supernova, and collapses into a Red/brown/white dwarf, or becomes a black hole may seem relatively small from its original size, but still retain most of their massive gravitational properties, strong enough to even bend light, is known to have a considerable amount of mass.\n\nTry this sites:\n http://www.astronomynotes.com/solarsys/s2.htm\nhttp://en.wikipedia.org/wiki/White_dwarf\n\n~meow
42886
There is a detailed (perhaps too detailed) explanation at the following location:\nhttp://www.france-property-and-information.com/metric-system-and-history.htm\n\nYou will also find at this location several pages which will discuss other aspects of your question.\n\nIn terms of capacity, the metric system and the USA/Imperial systems simply use different units. The situation is a bit more complex for weight/mass. \n\nWeight is how much something ways, whereas mass is the amount of matter. We say that a kilogram (mass) is equal to 2.2 pounds (weight). However, this is true (roughly) only on Earth. For example, something that is 100kg. (220 pounds) on Earth would still be 100 kg. on the moon but only about 37 pounds on the moon. That is because mass is constant whereas weight depends on gravity. For most of this, the distinction is unimportant as we all live and work on the earth. However, scientific purposes (e.g. space travel) weight and mass are very different.