One way of solving this conundrum is to invoke a type of matter that has a gravitational field, but can not interact with light or other forms of electromagnetic radiation, and is therefore invisible.

• 解决这个难题的一个办法是求助一种拥有一种重力场的物质，但这种物质不能和光或另些电子磁场的辐射物质相互反应，因而为不可见的。