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Friday, 13 October 2017


It is the most frequently asked questions that what is the mass of the Universe, size of the Universe, or density of the Universe. We all know that Universe came into existence after the Big Bang. Big Bang is the phenomenon after which the Time came into existence. Universe is very big (actually that much big what we cant imagine of!). All the galaxies in the Universe are moving away from each other with very high speed whereas on the other hand, planets, moons are attracted by suns or stars. Even galaxies are also attracted by a big Black Hole in the center of it. There are billions of unsolved mysteries in the Universe. In these circumstances it is very difficult to calculate the exact mass, volume, and density of the Universe. Mass, density and size of Universe includes very big numbers and very small numbers too. For example, Mass Density of visible matter in the Universe is 3x10^-28 kg/cubic meter. The mass density of the Universe is 3x10^-31 times the mass density of water. These figures are enough explain the size of the Universe. Even after having so billions of heavenly bodies, Universe possesses a mass density of  just 3x10^-28 kg/cubic meter. The radius of the visible Universe is 4.40x10^26 meters, i.e 46.5 billion light years. Thus, we can say that observable Universe has diameter of about 8.8x10^26meters. Now here the question arises that what is Observable Universe?


The observable universe is a region (or we can say spherical region) of the Universe which includes all the matters that can be observed from Earth at the present time (Here, 'present time' is mentioned because Universe is expanding with the speed more than the speed of the light. This means by the time you read this line, Universe expanded more than 300,000km). That's very strange! The electromagnetic radiation from these far away objects taken time to reach Earth since the 'Big Bang' and astronomers believe that there are still many radiations left which are yet to come. There are at least 2 trillion galaxies present in the observable universe, containing more stars than all the sand particles present on the Earth! The estimated age of the observable universe is 13.799 billion years (being 0.021 billion years as its absolute error, means this age can be more than 13.799 billion years by 0.021 or less than 13.799 billion years by 0.021).


The radius of the Universe and density of the Universe is such that it give us the mass of the Universe, which is equal to 6x10^51 kg. This total mass is equal to the total mass of  4x10^78 Hydrogen atoms. We consider Hydrogen atom here because 9 out of 10 atoms and ions in the Universe are in the form of hydrogen atom. In physical cosmology, a famous theory named, Inflation theory helped in determining the mass of the Universe. This theory explains the exponential expansion of the space in the early Universe. The inflationary time lasted from 10^-36 seconds after the imagined Big Bang singularity to sometime between 10^-33 and 10^-32 seconds after the singularity. Also Inflation theory predicts that the mass density of the Universe should be close to the critical density that separates an open Universe which always grows from a closed Universe ( closed Universe collapses again and again!). The critical mass density is equal to 6x10^-26kg/cubic meters. This means that if the Universe is at critical mass density, then the total mass of the Universe will be 1x10^53 kg, which consequently increase the total number of atoms to 6x10^79. Also, there will be 1x10^9 times more photons and neutrinos  than atoms, which is flying in the Universe in the form of bundle of energy packet in light.



As we discussed earlier about the Observable Universe, which is observed by the Earth. Its been billions of years when Big Bang occurred. Since, Universe is expanding for 13.8 billion years, therefore the radius is now about 46.6 billion years. Of the 100% Universe, we can observe only 4% of them and the rest 96% is made up of matter that astronomers cant see, detect or even understand. These mysterious substances has not been identified or been detected yet. Astronomers named it as Dark Energy and the matter made up of these matter was named as Dark Matter. This energy helps the Universe to expand as this energy creates space anywhere in the space. Keeping in mind that the volume of the Earth is 260 Billion cubic miles and that of the observable Universe is 3.58x10^80 cubic meters, the percentage of the space by the Earth in the observable Universe is 1.167x10^-64 %. It means, if we consider a space occupied by a sand particles on the Earth, then the percentage of space occupied by the sand grain on the Earth will be 10^-62 times more than the percentage of space occupied by the Earth in the observable Universe. Just imagine how small we are if we consider observable Universe as the parameters.
That's all for now.. Hope you enjoyed it!
Be updated for the curiosity.. Gud bye..

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A tech and gadget lover who is passionate about writing. Life Goals: To shout from the Mountain Peak: Yes, I did it.


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