'Mass' is the measure of the intrinsic property of inertia of any object in the Universe which states that how much matter is packed in a certain volume of space. In other words, how much atoms are found in a certain volume of the space. This density of atoms creates a specific level of resistance to change in the motion of an object which is measured as 'mass'. Why this density behaves in this manner? To explain it at an atomic level, we would require Quantum Physics, but its effects accumulate large enough to be measured in the classical physics. One explanation, and perhaps more accurate, is that atom is basically a small pattern in the four-dimensional fabric of space-time continuum. Whenever this pattern is forced to move, it shows the resistance. To detect this resistance at atomic or subatomic level is very hard and 'uncertainty principle' does not permit to do so with high accuracy. This resistance has the accumulative property, so large number of atoms accumulate, thus, the resistance of any object large enough to be seen, bound by electromagnetic forces, is comparatively easy to determine. This explains why Relativity predicts the change of time, size, and mass of an object is dependent on its acceleration or its presence in the strong or weak gravity. For instance if t=7 and s=3, then t+s=10; or if s=7 and t=3, then s+t=10 too. It means, space-time is constant, but when we separate it into space and time independently, one or the other has to compensate. This is how 'time dilation effect' and 'length contraction' have the link with acceleration in the space. So faster you travel, longer you live. Slower you travel, faster you die. We humans are not made to conceive 4 dimensions, thus the constancy of space-time remains invisible; rather, we receive the 3-dimensional shadow of 4 dimensional space-time in which the symmetry is broken. These broken parts show us different values when we work on any part. This can be understood through a simple example: A 3-D cube's all corners run 90 degrees from each other (all six sides are squares). But when it casts the shadow which is in 2-D (length and width, but no depth), it's corners will have different angles, and more than four corners. This is only achievable if the matter is a pattern on the fabric of space-time, thus it affects the space-time. This also explains, that if anything in the Universe is a pattern of space-time, then the energy is no different so it is also the pattern of the same space-time, matter and energy then becomes convertible to each other. That is E=mc(2)

This explanation predicts that only space-time exists and nothing else. Everything is made of atoms and subatomic particles, thus it is the pattern or collection of patterns on the same fabric of space-time, though, this unification poses some implications i.e., if at an atomic level there is no difference between a living and a non-living thing, what is life then? What is life made of? Is this self-animation too the pattern of space-time? If so, then, is the space-time a largest living thing? Surprisingly the answer is 'yes'. This answer does not come from science directly yet, but from the Holy Qurran, which is indeed more authentic for these sortof 'other wordly' issues. Qurran says: 'The seven heavens and the earth and all that is therein, glorify Him and there is not a thing but glorifies His Praise. But you understand not their glorification. Truly, He is Ever Forbearing, Oft-Forgiving' (Al-Isra:44). Therefore, any definition which states the difference between the living and the non-living cannot be taken for granted. For example if the 'life' is the scientific name of 'ability of reproduction', then this definition makes 'fire' alive which is not acceptable to biologists. But according to Qurran, even fire is also alive, not because it is reproductive, but because Qurran has a different standard definition of 'life' which we do not yet fully comprehend. There is a Quantum mechanical evidence that every atom possesses a motion of some kind, either it is the electron which pops in and out of existence or the vibration an atom or a molecule which determines the temperature of the overall object. But this movement is nowhere near the general idea of 'life', though it is quite worthy. This movement appears more rather like a vibration of the strings of a guitar, implying a conscious 'musician' playing it. The 'String' theorists always interpret the basis of everything (sub-atomic particles) as the notes on the strings of a guitar where different notes and pitches of the same string show up as different sub-atomic particle i.e., electron, photon, neutron, proton, quarks, and recently new particles with opposite charges (positron is the electron possessing a positive charge), thus the name of 'String' theory. But we cannot imagine who and what this 'musician' is, and is the 'life' basically a special vibration associated to some collection of atoms i.e., a man? Avoiding this deep issue, so far it is now clear that everything that exists in the Universe has consciousness, including the Universe. They speak and posses feelings, but we do not understand them. Humans are also the ones who have capability to go against their Lord, thus making them different among other creatures. This ability to disobey also means that they are more worthy to be called 'viceroys of God' because they choose to become obedient while God remains unseen. It is however yet to explain completely what makes them different. Are all humans born different or just few amongst them achieve this status due to certain criteria later in their life? Humans are of course different than other animals because it was observed that humans use cell phones and they endeavor to cross the vastness of space to reach Moon and soon, on Mars.

Since 'everything will taste death' (Qurran), consequently Universe, its fabric of space-time, and everything in it is bound to taste the death, which is also a scientific fact now. The destruction of 'time', at which our all physical theories break down and do not give us permission to calculate, is the moment which shall result in exposing the 'eternity' in which a 'new kingdom of heaven' shall be created. This eternity is not a new eternity, in fact those 'time-bound' layers which began as a Universe will be actually demolished, the reason how the underlying eternity shall be exposed, which was also there before the creation of the Universe. Since 'time' will not be ticking anymore, everything in the new kingdom will be eternal. At this point of 'no-time', it is however important to be cautious that we are time-bound objects thus it will never be possible for us to describe this whole expected scenario with accuracy. Same like 'uncertainty principle', the further we try to calculate the mechanics of eternity, the more we loose its track. And also same like 'wave-particle duality of subatomic particles and light photons', Universe and its space-time posses the duality of finity and infinity at the same time. Visualizing this duality as a layered system is misleading because it is just one layer which has both opposite properties. Finite time and space are the patterns of eternal timelessness and the spacelessness, which cannot be differentiated into two things.

For an object with less mass, less force shall be applied to move it. This holds true even in the space and in the microgravity. (Microgravity is not the absence of gravity, rather the object's fall rate is same as 1 G. If someone is in the lift and suddenly the cables are broken, everything and everyone inside the lift will face microgravity for some moments and they will face weightlessness while the lift is still falling. Orbit is also a constant fall. If you maintain a special speed at a special altitude in the space, the object will keep on falling and will never hit the Earth because rate of fall is the same as curvature of Earth is being encountered. Onboard International Space Station which orbits Earth, you may have seen the weightlessness of astronauts and their tools. There even a massive machine requires considerable force to be moved, though it is not touching the floor or roof or any other side. Here on Earth, the friction from different supporting surfaces are also responsible for greater application of force for the massive machine. In the microgravity however the force of that friction is subtracted).

Weight is the measure of how much gravitational force is being applied to the object by the bigger object nearby i.e., Earth's gravitational force on Moon. Thus an object with a certain mass will be 60 kilograms at Earth considering Earth's gravity is called 1 G (falling rate of all objects is 11 meters per second), however it will be 10 KG at Moon (G is less than 1 at Moon), and over 300 KG at the surface of Jupiter (G is greater than 1 at Jupiter), even though the mass is the same. This also explains why lighter and heavier objects fall at the same rate on Earth considering air friction is not an issue. This is because gravitational force and the inertia of an object (resistance to change) are exactly cancelled out. A small piece of stone and a very large piece of stone fall on Earth at the same rate even though their masses are different.

Thus while the mass of an object can be the same at any place in the Universe, its weight would be different in different places in the Universe.