Even if you’ve had seven or eight hours of sleep, when that alarm goes off or your eyes blink open first thing in the morning, you may still wake up feeling sluggish and disoriented.

Unlike a brand-new Porsche that can go zero to 60 nearly immediately, we’re more like a beat-up — but beloved — old Chevy that takes a few turns of the ignition before our engines really rev up. 

Even when you’re in tip-top shape, you might struggle with grogginess in the morning. So what’s going on?

Waking Up Tired

That groggy feeling has a name: sleep inertia. Despite most people experiencing it on a daily basis, scientists don’t know exactly what causes it. However, brain studies show that some features of being asleep persist even after you wake up. It’s theorized that this is a protective mechanism that makes it easier to fall back asleep if you wake in the night.

Not all parts of the brain warm up at the same time, either. You may get yourself to stand up and walk down the hall, but you probably couldn’t do your taxes in the moments after you wake up. Your prefrontal cortex — the part of the brain responsible for decision-making, emotional regulation, and working memory, appears to take the longest to get going.

There are two main signs that tell scientists your brain takes some time to fully catch up with your body in the morning. One is that the brain continues to emit delta waves — the slow-wave frequency your brain typically produces during deep sleep. 

The other involves adenosine, a chemical that builds up in your brain while you’re awake that promotes drowsiness, so you’ll want to sleep at night. The longer you’re awake, the more it builds up, making you more tired as the day wears on. This natural tranquilizer decreases while you sleep, but some scientists believe that when you wake, your adenosine level hasn’t fully “cleared” yet. That means you could be drowsy even after a full night’s rest.

This also helps explain why you’re especially tired when you don’t get enough sleep — you didn’t give your brain enough time to deplete its adenosine. It’s also why coffee wakes you up, as caffeine physically blocks the adenosine receptors in your brain.

Sleep inertia can occur when you wake up from an afternoon nap of more than 30 minutes, but it’s more likely seen after a night’s sleep. It causes reduced awareness, a decline in performance, difficulty making decisions, and a strong desire to return right back to sleep (we all know that one). These feelings usually go away after 30 minutes, but can last as long as two hours.

These Conditions Don’t Help

While sleep inertia is a normal part of waking up, some conditions can make it last longer, including sleep deprivation, insomnia, depression, stress, and drinking alcohol or caffeine before bedtime. Suboptimal sleep environments, such as bright, noisy, or hot rooms, may wake you up many times in the night without you realizing it, contributing to inertia.

You may also be out of sync with your own chronotype, your natural sleep preference. For instance, you may be a night owl but have to get up each morning at 7 a.m. for work. 

The best way to think of grogginess in the morning is that it’s a (hopefully brief) transition phase from being asleep to being awake. And because it’s a transition, that means it’ll soon pass and you’ll be bright-eyed and ready to get your day going — assuming, of course, you went to bed on time and got a good night’s sleep in the first place. You did go to bed on time, right?

Before babies can say “Do that again!” they already have a powerful way to communicate: laughter. A baby’s first giggles are among the most delightful milestones of infancy, but they also raise an intriguing question: Why do babies seem so much more easily amused than adults, with playing peekaboo or wearing a spoon on your nose sending them into fits of uproarious laughter?

After all, it’s easy to love your mom and dad — but that doesn’t necessarily mean they’ve got great comedic timing. But babies’ seemingly random giggles aren’t random at all.  

Researchers studying these questions (with some of the cutest subjects in science) think laughter may actually be one of babies’ earliest tools as they learn what it is to be human.

A Social Superpower

As cute as they are, a baby’s first smiles are usually involuntary or simple mimicking. Those early grins, which have even been observed in the womb, aren’t signs of happiness. 

But by about six weeks, babies develop “social smiles” in response to familiar faces and voices. Genuine laughter usually follows around three to four months, right as babies become increasingly interested in the people around them.

That timing is no coincidence. Developmental psychologists now think humans use laughter primarily as a social signal, rather than simply a response to something funny. Think about it — we tend to laugh far more often during ordinary conversations in response to fairly banal remarks (such as “I parked the car weird”) than after hearing actual jokes. In other words, we usually laugh to reinforce social bonds with one another.

Baby laughter appears to work much the same way. A laugh tells a caregiver, “I like this,” “I’m enjoying being with you,” or simply, “Keep doing that!” Infants’  laughs have been called the “five-star Yelp reviews” of babyhood, meaning that babies are simply enjoying being a baby. (“Five out of five stars, would baby again!”) 

The laughs also activate pleasure centers of the brain in both child and caregiver, cementing bonds in their relationship. That’s incredibly important, given how trying this relationship can be. (Hello, 3 a.m. wakeups.)

Goo Goo Ha Ha

Other times, babies just truly find something hilarious. Often these laughs are provoked by something surprising (but harmless). Peekaboo is a classic example. (Mom has temporarily disappeared, but not for so long as to be concerning.) Other examples include funny noises, exaggerated facial expressions, or grandpa pretending to wear a cup as a hat. 

Psychologists call these “benign incongruities” — things that violate expectations without being frightening. Babies are beginning to learn how the world normally works, so they delight when someone safely breaks those unwritten rules. It’s a sign of just how sophisticated their brains have already become.

As babies approach six months, they also begin experimenting with humor themselves. They may blow raspberries, knock over a block tower, or repeatedly perform an action that previously made everyone laugh. By the end of their first year, many babies intentionally tease adults by pretending to break small rules. 

These playful antics, sometimes called clowning, show they’re beginning to understand that other people have expectations — and that gently violating those expectations can be entertaining.

Scientists believe all of this serves a serious purpose. Laughter strengthens emotional bonds between babies and caregivers, encourages playful interaction, and helps babies practice important cognitive skills. In other words, every giggle is helping build both a growing mind and growing relationships. And there’s nothing silly about that.

There’s a myth that suggests hanging from a bar can make you taller by decompressing your spine. While there are many benefits to this “dead hang” exercise, including improved posture and grip strength, any height gains are temporary.

Yet there is one group of people who grow a couple inches every time they go into their unusual office: astronauts. Here’s what zero gravity does to their spines.

To New Heights

In space, astronauts experience microgravity (Earth is still pulling on them a little bit), a condition in which they seem to be weightless. Everything they do must be modified to account for the fact that without gravity, they float. 

Aboard the International Space Station, crewmembers sleep in pods with sleeping bags tied to the wall, and navigate by using handrails and gently pushing off walls. To work, they must strap themselves in or they’ll drift away.

That same lack of gravity also changes the human body. With no force pressing down on the spine, it decompresses when the spongy discs between the vertebrae expand and relax. Picture your spine, which is essentially a string of alternating bone and cartilage, stretching out like an accordion (though not nearly as dramatically). 

This results in a height bump of about 3% over the first 3 to 4 days spent in space. NASA astronaut Kate Rubins measured 5 feet, 6 inches tall on Earth, but grew to just over 5 feet, 7 inches tall in space. An astronaut who was 6 feet tall would gain about 2 inches. 

Because most of this increase is concentrated in the spinal column, the astronaut’s standing and sitting height changes, as well as their shoulder height. Their arms are farther from the ground, letting them reach objects positioned higher up. 

But just like dangling from a bar, this change doesn’t last forever. Once they return home, astronauts’ spines compress and bring them back to their “Earth” heights.

Growing Pains

While it might seem like becoming temporarily taller is a fun perk of going to space, microgravity can be harmful to the human body. When astronauts don’t have to bear weight while standing, sitting, or walking, they lose muscle mass. Their bones weaken, losing an average of 1% to 1.5% of their mineral density for every month in space. Bodily fluids also shift up and into the head, putting pressure on the eyes. 

About 70% of astronauts report back pain after a few days in space, and roughly half experience it back on Earth. One study conducted MRI scans of six NASA astronauts’ spines before their missions, immediately after they returned to Earth, and again one to two months later. The astronauts had all spent four to seven months in microgravity aboard the ISS. 

All six had experienced atrophy of the lean, functional muscle that supports the spine, and recovered only two-thirds of that loss one to two months after returning to Earth. They also faced four times the normal risk of a herniated disc. 

This is why NASA and other space agencies continue to study and find ways to counter the effects of microgravity on the human body. For example, compression cuffs can help keep blood in lower extremities, similar to wearing compression socks on long flights. 

Specific exercises can also help maintain bone and muscle strength. This is especially important as humans consider even longer missions and extended stays in space, and if we ever hope to reach Mars and other more distant destinations.

After all, we don’t want to take any small steps or giant leaps if it means throwing out our backs.