回复 1# hjfgcx
楼主质疑的是"宇宙加速膨胀"还是"暗能量"?
"宇宙加速膨胀"是一个观测事实,要想质疑它就要从观测的角度出发,比如数据处理有问题,有误差没有考虑,或者Ia型超新星不适合做标准烛光等等,不过这个显然不是楼主的出发点,所以说你还是接受宇宙加速膨胀这个事实的?只不过它跟"能量守恒"相矛盾,所以觉得有疑问?
关于"能量守恒", google到这么一段话,希望能够给楼主以启发:
> 1) Is it generally accepted that GR guarantees conservation of energy
> (or read "energy + momentum" wherever I write only "energy") locally,
> but not globally (in the universe as a whole) in an expanding universe?
It's trickier than that. Start with Newtonian gravity. For energy
to be conserved, one must clearly include gravitational potential
energy -- otherwise, the increasing kinetic energy of, say, a falling
apple would violate conservation. But in general relativity, there
can be no local definition of gravitational potential energy, since
for a small enough region one can always switch to a freely falling
reference frame, in which gravity locally disappears. So you can look
at the problem as not so much one of energy conservation as one of
even defining energy.
GR guarantees energy conservation locally in one, specific sense: if
in such a freely falling frame, in a region small enough that both
internal gravitational interactions and tidal forces from the outside
can be neglected, GR reduces to special relativity, in which energy is
conserved.
In an asymptotically flat spacetime -- that is, a spacetime in which
matter is all concentrated in a finite region, and the spacetime
becomes flat at large distances from that region -- one can also
define a *total* energy in GR ("ADM mass"), essentially because distant
observers see a flat, SR-like spacetime. This does not hold in our
Universe, of course, but it allows for good approximations. Spacetime
around the Solar System is not quite asymptotically flat -- eventually
you'll hit other stars -- but it's flat enough far enough out that the
ADM mass of the Solar System makes sense as a very good approximation.
出自:
http://www.natscience.com/Uwe/Fo ... -expanding-universe
简单来说就是广义相对论只保证局域的能量守恒,不保证全局的能量守恒.
当然我是不懂广义相对论的,所以欢迎后面的人补充. |
置顶卡
变色卡
千斤顶
显身卡