Why is this the answer?

The answer is bed because this sweet and clever riddle uses pictures made of words to describe where we sleep every night. It is a very tricky riddle that makes you think about an ordinary object in a brand new way, comparing it to two things found in nature. Let us look closely at the first clue: "In the night a mountain." Think about what your bed looks like when you are sleeping soundly inside it. When you climb in and get all tucked in, the blankets and pillows pile up and create big, puffy shapes. This is especially true if you have a big, fluffy comforter. When your body is underneath those heavy, thick covers, you push the material up and make big bumps and hills. These bumps and heaps of covers can look just like a small mountain range sitting right in your room! The sheets and blankets are rumpled and high, especially with you tucked securely underneath them, resting after a long day of playing and learning. The shadows at night can make those high spots look even bigger and more mysterious. This is why the riddle calls it a "mountain" in the dark when you are asleep and making those big shapes with your cozy, comforting covers. The bed, with all its blankets and pillows, becomes a great big mound. Now, let us think about the second part of the riddle: "in the morning a meadow." A meadow is a wide, open field covered in grass and flowers. Imagine that same bed after you wake up, stretch, and get out to start your busy day. If you remember to pull the blankets up and smooth out the sheets, the bed becomes flat, open, and neat again. The tall, bumpy "mountain" is completely gone. The bed is stretched out and level, just like a big, smooth meadow ready for whatever comes next. It is a surface with very few lumps or high spots. Even if you do not make your bed, the fabric naturally settles and becomes flatter once your weight is no longer on it. However, when it is neatly made, it looks perfectly smooth and wide, like a peaceful field of grass just waiting for the sunshine to hit it. This clever riddle captures the fun change a bed goes through every single day. It cleverly uses the contrast between the bed's look at night, when it is occupied and rumpled like a mountain, and its look in the morning, when it is empty and flat like a meadow. It shows how even the most common things in your house can be part of a wonderful puzzle waiting to be solved.