Some theorists have concluded that String Theory does not allow for Dark Energy.
As stated before, if the universe has matter and the surrounding nothingness does not, then there is a difference in pressure which should cause the universe to expand. Matter at the "edges" of the universe would dissipate faster than the matter in the "center". This might make it seem that the rate of expansion is increasing, since we use distance as a measure of age (time passed), thus measuring the edges of our known universe to find out what happened in the distant past.
Also, if everything decays into radiation which travel at the speed of light, then does this radiation "know" distance, since according to known theory, it does not "experience" time?
Quanta Magazine: Dark Energy May Be Incompatible With String Theory
