From Serious Eats:
First off, it’s true: mushrooms do absorb water when you wash them, but it’s only about 2% of their total weight, or, translated to volume, that’s about 1 1/2 teaspoons of water per pound, which in turn translates to an extra 15 to 30 seconds of cooking time.
“Soggy” is an exaggeration.
AFAIK there is no known energy source that would keep a generation ship powered for the duration of an interstellar flight.
The person to whom you responded is half right. The speed of light is half of the barrier to interstellar travel. Entropy is the other half.