Contrast the roles of dark matter and dark energy in the fate of ...

[Lobcity]

Contrast the roles of dark matter and dark energy in the fate of the cosmos.
 
  What will be an ideal response?

Question 2

How does gravitational lensing let us find massive dark objects?
 
  What will be an ideal response?

[connor417]

Answer to Question 1

At first, the discovery of much dark matter seemed to increase the role of gravity, giving us more than the critical density and closing the Big Bang. But dark energy acts against gravity, speeding up the expansion into at least a flat universe in the future.

Answer to Question 2

When a black hole or brown dwarf passes between us and a bright star, the gravity of the dark object can bend and focus the light of the distant star, making it brighten temporarily. The more massive the unseen object, the longer this brightening will last.

[Lobcity]

Excellent

[yeungji]

Thanks for the timely response, appreciate it