Regardless of their preferred mode, bats, elephant, honeybee, humans and more all sleep. In fact, scientists have yet to find a truly sleepless creature. But is sleep really necessary for survival?

Most humans will acknowledge that sleep is absolutely necessary. People often struggle to function after even just one sleepless night. Poor sleep over the long term has been linked to many negative health effects, from heart disease and stroke to weight gain and diabetes(糖尿病) . These connections, and the fact that all animals seem to sleep, suggest that sleep must play an essential function for animals. But what is that function? Does sleep allow the brain to repair damage and process information? Scientists and thinkers have offered explanations for why we sleep, and yet, the exact purpose of sleep remains an open question.

In the 1890s, Marie de Manaceine, a female physician in Russia, was troubled by the mystery of sleep. In her quest to figure out what exactly sleep is, she conducted the firstsleep-deprivationexperiment in animals.

Using an approach that now seems quite cruel, the physician kept puppies continuously awake, finding that they died after a few days of the experiment. Over following decades, further such experiments using other animals found similarly fatal results. However, the underlying cause of death in these cases, and how it relates to sleep are still unknown.

While total sleeplessness seems dangerous, some creatures can get by with a remarkably short sleep. They could be the key to understanding sleep's function, scientists have said.

A study published in Science Advances monitored the sleeping habits of fruit flies. "We found that some flies hardly ever slept," study co-author Giorgio Gilestro told Live Science."But these flies didn't die prematurely(过早)，like the Russian puppies did. These virtually sleepless flies instead lived just as long as a control group that was left to sleep normally"."

In a 2016 study, Rattenborg and his colleagues provided great frigatebirds in the Galapagos Islands with a small device to measure electrical activity in the brain. The study found that the frigatebirds, while flying, slept on average just 42 minutes per day, even though they typically got more than 12 hours of shut-eye on land.

Does Rattenborg think we'll ever find an animal that doesn't sleep at all?

"Anything is possible," he said, "however, an emerging pattern among the studies of short-sleeping animals is that none are completely sleepless. This preservation of a little sleep suggests that there is a minimum amount of sleep that is essential, even in these remarkable short sleepers."

New research has shown how the Leaning (倾斜) Tower of Pis has managed to keep standing in the face of several strong earthquakes. It has leaned at an angle of about five degrees.

The vulnerability (脆弱性)of the UNESCO World Heritage Site has confused engineers and scientists for a thousand years. Earthquake activities were expected to significantly damage the tower or even result in its falling over. However, unbelievably, this has not happened.

A research group of 16 engineers at the University of Bristol have now discovered that the height and hardness of the tower, combined with the softness of the base soil, ensure that it doesn’t resonate (共振)with earthquake ground motion, which is known as Dynamic Soil-Structure Interaction (DSSI) and the lower now holds the title of world record holder in DSSI effects.

What is interesting is that the very same soil, which caused the leaning instability(不稳定性) and made the tower almost fall, can be credited for helping it survive these earthquake events.

The tower continues to attract visitors keen to express their big surprise at amazing buildings. Construction of the tower began in the twelfth century and continued for over 199 years clue to the onset of a series of wars.

Multiple efforts to preserve the historic site have occurred over the years. In the 1920s, the bases were put in cement grout (水泥架)with the intention of making the tower firm. In 1990, a decision was made to completely close the site to visitors due to the fear that it was at risk of falling over.

It was the first time the tower had been closed in 800 years. It reopened again in 2001 and remains one of Italy’s most popular tourist attractions.

When you are sitting in class, have you ever drawn pictures in the margins (页边的空白处) of your notebooks? If so, you are doodling. Many people think of doodling as a distraction (分心) from more important things. But it might be just the opposite.

One study shows that doodling may help you remember things you hear 29% more. Besides, doodling can help you think creatively. Walking away from a problem to draw might actually help you solve it. When you come back, you’ll have a fresh perspective and figure out an answer more quickly.

An author named Sunni Brown wrote a book on doodling. She argues that doodling is a tool that can help people think. In fact, she runs a business that helps companies improve organization and planning through doodling. Brown believes doodling is helpful because it includes many ways of learning. You learn in four ways: seeing, hearing, reading or writing, and through movement. The more ways you use, the better you learn. And when you doodle while listening to a lecture, you use all four.

You might think that being good at drawing is important for doodling. But if the point of doodling is to help you think, then it doesn’t matter what the picture looks like. Even if you’re not an artist, doodling can help you. So next time you need help focusing, pick up a pen and doodle away!