宇宙临界密度学说自相矛盾无法自圆其说——大学物理学教材析疑

Question on the Theory of Universe Critical Density——Rectifications of Some Mistakes in College Physics Textbooks

通过引述几本具有代表性的大学物理学教科书中对宇宙演化的膨胀与收缩取决于天体物质密度与宇宙临界密度的相对大小的说法，指出了如果将宇宙收缩过程的所谓临界密度学说应用于宇宙膨胀过程就会自相矛盾，并解释了为什么会产生这种矛盾的错误．最后给出了能够自圆其说的正确答案：宇宙的膨胀与收缩取决于物质形态的互相转化和质量与能量的相互转换——当质量全部转换成了能量，宇宙就会由收缩转而膨胀；而当能量全部转换成了质量，宇宙就会由膨胀转而收缩．奇点只有能量，没有质量密度．

Concerning the concept in several representative college physics textbooks that the expansion and contraction of the universe depend on the relative magnitude between the densities of celestial bodies and the critical density of the universe, this article pointed out that if the socalled concept of critical density for explaining the contraction of the universe is used to explain the expansion of the universe, self - contradictions will occur. In addition, this article analyzed the reasons for this mistake, and proposed correct and selfsupporting answers as follows. Firstly, the expansion and contraction of the universe depend on the alteration of the form of matters and the transformation between mass and energy. To put this into perspective, when all the masses are transformed into energy, the universe will change from contraction to expansion） when all the energy is transformed into masses, the universe will change from expansion to contraction. Secondly, singularities only have energy, but don＇t have mass density