Lewis and Clark was a group of men in the military, known as the Corps of Discovery and civilians. Led by their leader Meriwether Lewis and Lieutenant William Clark to explore the land obtained by the United States in 1803. Known as the Louisiana Purchase.
Answer: The correct answer is : The critical density for the universe is approximately 10 ^ -26 kg / m ^ 3 or you can also say 10 hydrogen atoms per cubic meter.
Explanation: This value is given by:
critical density = 3H ^ 2/2 Pi G, where H is the Hubble constant and G is Newton's gravitational constant.
Critical density is the average density of matter necessary for the universe to stop its expansion but after an infinite time.
The crusades helped to increase trade between the Europeans and the Middle East.