As I understand, Dark Matter and Dark Energy are euphemisms for "I really don't know". From the work of Fritz Zwicky and later by Vera Rubin what ever Dark Matter is, it responds to the force of gravity, but is not detectible as "ordinary" matter. Dark Energy describes "things/space" being pushed apart/away from one another. Research priority for these conditions/forces/things seems a challenge in modern physics which could re-write our place and future in the Universe. Based upon the curiosity raised in these articles, I've added Dark Matter and Dark Energy to my list to read about. Thanks.