【推荐2】Many of us have wondered what Earth is like beneath the surface. So have writers and scientists. In French novelist Jules Verne’s masterpiece Journey to the Center of the Earth, explorers go down to Earth’s center and discover amazing wonders.

But in real life, human beings haven’t even come close to the planet’s core (核心). The core is over 6,000 km down. The deepest hole ever created, according to the BBC, is the Kola Superdeep Borehole in Russia, which only goes 12.3 km down.

So how do we know about everything down below without any samples？

One good way to start is to think about the Earth’s density (密度), Simon Redfern of the University of Cambridge in the UK told the BBC.

“The density of the material on Earth’s surface is much lower than the average density of the whole Earth, so that tells us there’s something that has greater density,” Redfern said.

The challenge is to find out which heavy materials the core is made of. And the main material scientists have found is iron. The idea is that when Earth formed 4.5 billion years ago, a lot of iron made its way down to the core, taking up about 80 percent of it. Today scientists are still working on finding out which other materials the core could be made up of.

You might also wonder how we know the size of the core. There’s a one-word answer: seismology (地震学).

When an earthquake happens, seismic stations around the world record the shockwaves it sends throughout the planet. It’s like hitting one side of the planet with a huge hammer and listening on the other side for the noise.

Early research found that some shockwaves, called “S-waves”, went missing. S-waves can only travel through solid material, but not through liquid, so they must have found something molten in Earth’s center. By following the S-waves’ paths, scientists found out that rocks became liquid around 3,000 km down.

There are still many questions about the Earth’s core to answer. But the study of the dark world below isn’t just for scientists’ curiosity.

The movement of Earth’s molten iron core builds up a powerful magnetic (有磁力的) field. It protects us from radiation from the sun and is needed for compasses and GPS systems to work.

So perhaps none of us will ever set eyes on the core, but it’s good to know it’s there.

【推荐3】When special occasions such as birthdays or other big holiday events come around, parents often look for that special toy for their children. But there is a growing understanding that gifts of time and bonding, such as vacations and other experiences, make better and more lasting gifts for children.

Experts agree that gifting children with memorable trips and fun experiences is better for their body and mind, and has corresponding positive impacts on the rest of the family!

In a 2017 study that surveyed about 500 women between 18 and 93 years old, Dr. Oravecz, a human development and family studies professor at Pennsylvania State University, asked, “Most people feel loved when...” The study showed that the most popular answers had nothing to do with any material item. Dr. Oravecz said, “Our research found that micro-moments of positivity, like a kind word, a hug with a child or a sympathetic expression, make people feel most loved.”

Clinical psychologist Oliver James agrees. He stated that as opposed to toys, details from a trip are more likely to “stick with them for long after the vacation ends.” When families interact in a stress-free environment, this creates warm, generous feelings towards one another, which are likely to be remembered with fondness. Vacations create strong emotional responses that don’t often come with material possessions.

In addition, British child psychologist Dr. Margot Sunderland believes that vacations make children smarter. “What is less widely known is that vacations can also advance brain development in children. This is because on a family vacation, you are exercising two genetically ingrained systems deep in the brain’s limbic (边缘的) area, which can all too easily be ‘unexercised’ in the home.” Citing the work of neuroscientist Jaak Panksepp, Dr. Sunderland said, “These are the PLAY system and the SEEKING system.” “The brain’s PLAY system is exercised every time you bury your child’s feet in the sand or take them for a ride on your back. The SEEKING system is exercised each time you go exploring together: the beach, a cave, a hidden village...” She continued, “So when you take your child on a vacation, you are supporting their explorative urge (SEEKING system)—a vital resource for living life well, and their capacity to play (PLAY system). In adulthood, this translates into the ability to play with ideas—essential, for example, to the successful entrepreneur(企业家).”

In a busy household, perhaps the fun of having the latest toy may not last, but the space it occupies in the house could be there and gather dust. So for the next round of gift-giving with the children, consider an experiential gift instead. The return is definitely priceless.

【推荐2】If you have plans to run, then the first thing that you have to purchase is a good pair of running shoes. Put simply, how can you possibly run without running shoes, right? There are many ways about how to choose the right running shoes but these ways differ from one person to another. That is why first-hand experience is greatly recommended. By this we mean that you have to go to the store yourself to check and try on a pair of running shoes that you are looking at to see whether or not they are good for your feet and comfortable.

No matter what else you take into consideration, the most important thing is for you to be able to start choosing the right running shoes because there are a lot of options out there. These options might make you feel confused as to which pair to actually buy. But when you begin your search, you will have enough time to see which pair is best for you.

In the end, whatever you choose to buy should not require you to spend too much. That is to say, you have to make sure that what you buy is just right for your budget and the kind of activity you plan to take part in. This is to ensure as well that whatever you buy can be used for a long time.

So what more are you waiting for? Get up and start running by going to the different stores that sell running shoes and then see which pair is the best one for you. When you find the right pair, buy it immediately and start your new and far more active lifestyle now.

【推荐3】Good health is a precious thing. When we are healthy, we can learn, work, and support ourselves and our families. When we are sick, we struggle, and our families and communities fall behind.

That's why the World Health Organization is needed. Working with 194 Member States, across six regions, and from more than 150 offices, WHO staff are united in a shared commitment to achieve better health for everyone, everywhere.

The purpose that all people should enjoy the highest standard of health, regardless of race, religion, political belief, economic or social condition, has guided WHO's work for the past 72 years, since it was first set up as the lead agency for international health in the United Nations, which was founded in 1945.

Since 1970, the world has seen a rise in noncommunicable（非传染性的）diseases such as cancer, diabetes（糖尿病）and heart disease. Driven by forces such as rapid unplanned urbanization, globalization of unhealthy lifestyles and population ageing, these diseases now account for 70% of all deaths. So WHO has shifted focus, along with health authorities around the world, to promote healthy eating, physical exercise and regular health checks.

The organization has run global health campaigns on the prevention of diabetes and high blood pressure and on healthy cities. It negotiated（谈判）the WHO Framework Convention on Tobacco Control, a powerful tool to help reduce diseases and deaths caused by tobacco.

Achieving these goals will require unfailing political and financial commitment, from Member States and donors, and continued and expanded collaboration with colleagues from academia, Partners on the ground, and other members of the UN family.（From the official website of WHO, 2020. ）