Dear Brooklyn,

That’s a great observation. When my friend Ashley Ingiosi was a kid, she remembers how napping in the car during a four-hour drive to her grandparents’ house seemed to make the time fly by. Maybe you’ve had a similar experience.

As a researcher at Washington State University, Ingiosi is really curious about what goes on within the human brain during sleep. She was happy to help with your question.

“Sometimes sleep feels so short because we become less aware of our surroundings,” she said.

As you go about your day, you rely on certain signals from your senses—or stimuli— to know if you are awake and aware. This awareness is what sleep scientists call consciousness.

Image of Ashley Ingiosi who helped answer a Dr. Universe question about sleep
Ashley Ingiosi

But when you are sleeping, you don’t really sense the world in the same way. You can’t use your sense of touch to feel your bedsheets. You often can’t use your sense of hearing to pick up on the sounds around you. You might not feel it, but during certain stages of sleep, your eyes are darting around under your eyelids.

Even though you have a lower level of awareness, your brain and body are still very active.

“Brains are still very busy during sleep and doing a lot of different things,” Ingiosi said. “But the reason why we can stay asleep is that we are less aware of what’s going on around us.”

When you are awake and aware, you can use clues from your environment to sense all kinds of things, including how time is passing. But when you sleep, it makes it harder to track all those seconds, minutes and hours ticking by.

“If we were aware of things in the way that we are when we are awake, we’d have a really hard time staying asleep,” Ingiosi said.

Dr. Universe cartoon cat looking up to the skyThe amount of time humans spend sleeping is also important, she adds. As children and teenagers grow up, they need to sleep even longer than adults need to sleep.

According to our friends at the National Institutes of Health, school-age children and teenagers need about 9 hours of sleep each day. After the teenage years, you can do with a little less sleep. Most adults need about 7 to 8 hours of sleep each day.

While scientists are still unraveling many of the mysteries around how and why humans sleep, we do know sleep gives the body and mind a chance to recharge. It helps you stay healthy.

Sleep can also help strengthen the memories that you form throughout the day. It helps keep your brain working well, so you can do everything from finishing your homework to playing sports to asking big questions about our world.

Who knows, maybe one day you’ll be a scientist who helps us understand more about the fascinating experience of sleep. As for me, after investigating this great science question, I think it’s prime time for a cat nap.

Dr. Universe

It’s trivia time!

Humans need lots of sleep. Other animals do, too. Which of these animals sleeps 22 hours a day? Is it…

  • sharks
  • cats
  • koala bears

If you guessed koala bears, you are correct. Koalas can sleep for around 22 hours a day. Cats sleep for 12-16 hours. Sharks rest throughout the day, but we still don’t know a ton about how shark sleep works. There’s always more to discover about our world.