[Xiaoyu]

I read the thread "Matters made of space not energy" and i think Humility's idea is quite reasonable and that prompted me another idea,as described here below:

[POINT]:I think that Matter is made of space and in an ultimate sophiscated and orderly structure, just like a China knot or the folding of protein.

[China Knot]:think about the China knot, which is intricatedly woven by using a single cord(string or thread) - we may regard the cord as a single-dimentional space which is soft and felixble, after being woven, it becomes a square with certain woven pattern and the physical property of the whole knotted square(or squared knot) has changed from that of a single cord(mass just appears to be "substantial")
it is what i'd like to suggest: the folding of Space creats Mass(equivalently, Mass causes Space folding; gravity is only a case of distortion of space in a large spacetime domain), the Forces are phenomenea that a segment of space prevents another segment of space to crash (or blend) into it(if it does,there must be a blackhold).

[Entropy]I think Entropy(or negative Entropy) must be introduced to chracterize the complexity of the folding structure of space - Entropy is related to the density of Mass. The higher Entropy(less orderliness) the system is , the lower density is the system(actually all matters are "hollow" or "loose", the space between all kinds of elementary particles( and underlying structure) are supported by respective classe of forces ,because these forces have to prevent the space from crashing). Since we can use Entropy to characterize Energy(limitedly internal energy), and we have e=mc^2 ,therefore Entropy can also be used to characterize Mass extendedly.

[Orderliness] Actually, there exists nothing "really substantial" in the universe, but sophiscated "space tubes"(however in 4d spacetime,shall not be considered tube shape) system which is organized and maintained by a set of laws,in which may including the c - light velocity barrier(i think it is the most basic law - space can't crash into each other and we cannot leaped to another spacetime)

[e=mc^2] What really happens when fusion or fission takes place in a certain system is, not only does the mass lose,but also the orderliness of the whole system (the system Entropy increases)- the knot is unfolded. The equation just describes such an unfolding process and gives the conversion of the folding complexity to energy.

[then what is energy?] another presentation of orderliness(negentropy),i think. such a linear relationship between energy and mass in the Equation can only suggest the identical nature of the both.