The Blank is our name for the photons we see that were first released when the universe was about 380,000 years old.target 1 of 6 The Blank refers to a time period in which all four forces are thought to have been unified.target 2 of 6 Most of the helium in the universe formed during the Blank.target 3 of 6 The Blank is the name we give to the moment when the expansion of the universe began.target 4 of 6 The Blank refers to a time period in which the strong, weak, and electromagnetic forces were all unified.target 5 of 6 A very short period of extremely rapid expansion, called Blank, is thought to have occurred when the universe was about 10-38 second old