If you’re on the hunt for something new and interesting to read, you have plenty of places to go. This week, we’re looking at four of the best book recommendation sites, services, or groups, based on your nominations(提名).

GoodReads

GoodReads is more than just a book recommendation site, although it excels at helping you find new books to read based on the ones you enjoy. You can build a virtual “shelf” of books you own or have already read, share your progress with the books you’re currently reading, rate the books you’ve read, leave reviews, and connect with other readers.

BookBub

While BookBub isn’t strictly a book recommendation service, it does bring you super-low-cost books based on your interests every day. The service is free, and when you sign up, you tell BookBub what kinds of books you like to read. From there, you’ll get an email from BookBub every day with book deals for that day. When we say “deal,” we mean it—many of BookBub’s titles are free entirely, $0.99, or just a couple of bucks.

LibraryThing

LibraryThing has been around for a long time and is still a great user-powered book ratings, review, and recommendation site. The service calls itself the world’s largest book club, and that’s a lot like the overall feel. Once you sign up, you’ll be encouraged to start adding books you’ve read and leave reviews for them. Behind its book ratings and reviews though, LibraryThing is a powerful tool to catalog and organize your entire book collection.

Olmenta

If you’re not interested in registering for accounts, adding your own books, or any of that hassle(麻烦), Olmenta can suggest some solid titles to you based on general popularity and the citation of the people behind the site. It’s a simple list of book covers that the service thinks you should read, and a few genres you can click on if you’re looking for something specific, like business, fiction, children’s, theatre, poetry, or nonfiction, among others.

Students should be able to show what they know. Many folks take this as an apparent truth. But I think it demands closer examination.

Possessing a skill or piece of knowledge is not the same thing as being able to show it. This is why many smart young people hate school. Understanding，figuring out，and getting a handle on a piece of knowledge is really exciting，but having to prove to somebody else that you understand is a pain in the neck.

Finding proof of student learning is a huge part of the teacher’s job，and whether it is done poorly or not makes all the difference in that teacher’s effectiveness. There is a huge difference between“how do I figure out if this student understands”and“how do I make this student prove to me he gets it”.The first is a valuable approach；the second is the first step on the road toward wasting everybody’s time.

And there’s the problem. If we start with the assumption that a student who knows must be able to show his knowledge to our satisfaction，we will be traveling down the wrong road. The more we demand that students prove to us that they know the stuff，the more we will design artificial tasks that demand a set of skills and knowledge entirely different from those we really want to measure.

As a classroom teacher，I have to remember that the burden(重担)is on me to find a way to see what my students know；the burden is not on them to put on whatever trained monkey show.

It may not be the worst thing ever to say，“Students should be able to show what they know.”But I think it’s far more useful to say，“Teachers should be able to discover what students know.”

Scientists are preparing to launch the world's first machine to clean up the planet's largest mass of ocean plastic.

The experts believe the machine should be able to collect half of the detritus in the patch – about 40,000 metric tons – within five years. In the past few weeks they have been busy welding together giant tubes that will sit on the surface of the sea and form the skeleton of the machine, creating the largest floating barrier ever made。

The system, originally dreamed up by Mr. Slat, will be shipped out this summer to the Great Pacific Garbage Patch, between Hawaii and California, and which contains an estimated 1.8 trillion pieces of plastic. It will be the first ever attempt to tackle the patch since it was discovered in 1997.

Mr. Slat was 16 and still at school when he was diving in Greece and first saw for himself the amount of plastic polluting the sea. “There were more bags than fish down there,” he recalls. Two years later he came up with a solution, quit university after six months and set up The Ocean Cleanup as a company. Mr. Slat, 23, says the first plastic to arrive on shore will be a major milestone. “We as a humanity created this problem, so I think it's our responsibility also to help solve it,” he said.

The Great Pacific Garbage Patch (GPGP) spans 617,763 sq miles - more than twice the size of France, and contains at least 79,000 tons of plastic, research found last month. Most of it is made up of “ghost gear” – parts of abandoned and lost fishing gear, such as nets and ropes – often from illegal fishing vessels.

Ghost gear kills more than 100,000 whales, dolphins and seals each year, according to scientific surveys. Seabirds and other marine life are increasingly being found dead with stomachs full of small pieces of plastic. Creatures eat plastic discarded in the sea thinking it’s food but then starve to death because they are not feeding properly. Others are trapped and die of starvation or are strangled or suffocated by ghost gear.

Traditionally, robots have been hard, made of metal and other rigid material. But a team of scientists at Harvard University in the US has managed to build an entirely soft robot-one that draws inspiration from an octopus (章鱼).

Described in science journal Nature, the “Octobot” could pave the way for more effective autonomous robots that could be used in search，rescue and exploration. “The Octobot is minimal system which may serve as a foundation for a new generation of completely soft, autonomous robots” the study’s authors wrote.

Robots built for precise, repetitive movements in a controlled environment don’t do so well on rough terrains (地形) or in unpredictable conditions. And they aren’t especially safe around humans, because they’re made out of hard and heavy parts that could be potentially dangerous to their users.

So researchers have been working on building soft robots for decades. They’re taken inspiration from nature, looking to animals from jellyfish to cockroaches, which are often made up of more flexible matter.

But creating a completely soft robot remains a challenge. Even if engineers build a silicone (硅酮) body, it’s still a grand challenge to construct flexible versions of essential parts, such as a source of power.

“Although soft robotics is still in its early stage, it holds great promise for several applications, such as search-rescue operations and exploration,” Barbara Mazzolai and Virgilio Mattoli of the Italian Institute of Technology’ Center for Micro-BioRobotics, wrote in a comment. “Soft robots might also open up new approaches to improving wellness and quality of life.”