Why and how do dreams feel so real ?

Question

i have been sleeping and then when i dream about falling i get the feeling of it in my tummy

Answer 1

Dreams seem real because the part of you that constructs dreams has full access to all your memories. Not just visual memories, but memories of sensations of all types--it can make the dream as accurate as it wants.

Answer 2

There are two parts of sleep - normal sleep, and REM sleep.  We dream during REM sleep.  (The REM stands for Rapid Eye Movement, because our eyes move as we dream.)

The brain processes of normal sleep are quite different to those we go through when we are awake.  Brain processes during REM are actually very similar to those of the awake brain though.  When we dream we feel something, we use the same parts of our brains as when we actually feel it, which makes the dream seem very real.