If you see a group of people dancing and singing on the street or in the railway station,  you don't need to feel surprised．They are a flash mob （快闪族）, which is a group of people who come together suddenly in a public place, do something unusual for a brief period of time,  and then quickly break up．They are usually organized with the help of the Internet or other digital communication network．At a predetermined time, they gather and perform some  distractions（消遣） such as waving their hands and exchanging books, Then, they quickly break up before the police can arrive．Using mobile phones, the flash mob can change its location if the first one has been replaced for any reason．

    Bill Lasik, senior editor of Harper's Magazine, organized the first flash mob in Manhattan in May 2003 and the first successful flash mob came together on June 3, 2003 - after the first try was foiled at Macy's department store．Lasik claimed that the activity was designed to make fun of hipsters （起时髦的人）, and call attention to the cultural atmosphere．

    Flash mob gatherings can sometimes shock people．Such an activity might seem amusing and untrue, but it also might frighten people who are not aware of what is taking place．Undoubtedly, flash mobs can serve as good political tools in any direction．They also have great economic potential, such as using flash mobs to advertise a product．

    The flash mob is now becoming more and more popular．People use it to do many things．For example, in 2009, Michael Jackson's fans took part in a flash mob to remember him．Hundreds of his fans gathered singing and dancing Michael's famous song "Beat It" together．Flash mobs give people from all walks of life an opportunity to come together to create a memory．

    Ask someone what they have done to help the environment recently and they will almost certainly mention recycling. Recycling in the home is very important of course. However, being forced to recycle often means we already have more material than we need. We are dealing with the results of that over-consumption in the greenest way possible, but it would be far better if we did not need to bring so much material home in the first place.

    The total amount of packaging increased by 12% between 1999 and 2005. It now makes up a third of a typical household's waste in the UK. In many supermarkets nowadays food items are packaged twice with plastic and cardboard.

    Too much packaging is doing serious damage to the environment. The UK, for example, is running out of it for carrying this unnecessary waste. If such packaging is burnt, it gives off greenhouse gases which go on to cause the greenhouse effect. Recycling helps, but the process itself uses energy. The solution is not to produce such items in the first place. Food waste is a serious problem, too. Too many supermarkets encourage customers to buy more than they need. However, a few of them are coming round to the idea that this cannot continue, encouraging customers to reuse their plastic bags, for example.

    But this is not just about supermarkets. It is about all of us. We have learned to associate packaging with quality. We have learned to think that something unpackaged is of poor quality. This is especially true of food. But it also applies to a wide range of consumer products, which often have far more packaging than necessary.

    There are signs of hope. As more of us recycle, we are beginning to realize just how much unnecessary material we are collecting. We need to face the wastefulness of our consumer culture, but we have a mountain to climb.

    Who could have imagined that a treadmill（跑步机）on wheels would one day become a thing?!? Lopifit is an unusual means of transportation that allows you to power an electric bicycle by walking on a treadmill.

Lopifit founder Bruin Bergmeester says it all started when he asked himself the question "How can I use a treadmill outdoors?" He finally came up with a new design, adding an electric motor, and the Lopifit was born. It's similar to an electric bicycle in that the motor only works when the rider puts power in as well. The Lopifit senses when you walk on the treadmill and uses the motor to turn a drive chain at the back of the treadmill, helping you reach a top speed of 17 miles per hour.

    To use the Lopifit, simply turn on the battery（电池）and use your foot to slide the treadmill backwards and start the motor. Then get on and enjoy the ride! If you need speed, just walk on the treadmill, and if you want to coast（惯性滑行）, all you have to do is stay still and admire the view. To stop, you have two hand breaks.

    The Lopifit first hit the streets in 2014 and, unsurprisingly, became a hit overnight. That was actually quite challenging for the company, because it started getting calls for orders, but it was nowhere near ready for mass production. The unique treadmill bicycle could be bought this year, and Lopifit is struggling to keep up with demand, although the price is up to $2,115.

    Some people consider this means of transportation stupid and unnecessary, although there is a very loyal fan-base of so-called Lopifitters. They simply believe that if you're going to walk, you might as well do it the old-fashioned way.

But the Lopifit does have the special advantage of helping you "walk" really fast without much effort, or walking at cycling speed, if you will.

    As free as they make us, mobile phones still need to stay close to a power source. Soon that may change with "green" power.

    Three Chilean students got the idea for a plant-powered device(装置) to charge their cellphones, while sitting in their school's outdoor courtyard during a break from exams, with dead mobile phones. Then, one of them had an "aha" moment.

    “It occurred to Camila to say about plants,” said inventor Evelyn Aravena. “'Why don't you have a socket, if there are so many plants? 'After that, we thought, 'why don't they have a charging outlet? Because there are so many plants and living things that have the potential to produce energy, why not?'”

    Their invention—a small biological circuit called E-Kaia—uses the energy plants to produce during photosynthesis(光合作用). A plant uses only a small part of that energy and the rest goes into the soil, and that's where the E-Kaia collects it. The device plugs into the ground and then into your phone.

    "It's the most amazing project I've ever seen in my life, plain and simple. They brought this original model, and it worked — and that's when it all changed, at least from my personal point of view and I began to support them." said Mauricio Cifuentes.

    The device solved two problems for the engineering students — they needed an idea for a class project, and an outlet to plug in their phones.

    "Looking for a place to charge the notebook, which had no power, and the mobile phones, we weren't able to find anything because all the other students were in the same state of madness trying to find a place to charge their devices," said Aravena.

    But plants are everywhere, and the bio－circuit makes the best of their excess(过多的) power.

    The E-Kaia doesn't carry much charge but it's powerful enough to completely recharge a mobile phone in less than two hours.

    The student inventors have applied for patents on their technology, and expect the E-Kaia to go on sale in December 2016.

    During your four years in the college, you'll have many exciting choices to make, the first of which will be your course selection for your first semester. The beauty of this choice is that you can't go wrong! No matter which one of our First-Year Options you select to apply for, you will create a rich intellectual experience to begin your college career.

    Option 1: Liberal Arts Seminar

    The Liberal Arts Seminar is a multidisciplinary(多学科的)course that explores the cultural history of the Mediterranean through fictional and nonfictional books.

Fall schedule: When Registration opens, you will select between one and four additional courses to complete your schedule.

    Option 2: FLL Hager Scholars Program

    The FLL Hager Scholars Program is designed with our most ambitious students of languages and linguistics in mind, and is designed to create for them both a sense of community and opportunities for intellectual growth.

    Fall schedule: When Registration opens, you will select between one and three additional courses to complete your schedule.

    Option 3: Ignatius Seminars

    Offered only in the first semester, Ignatius Seminars introduce students to the depth and diversity of Georgetown's dynamic intellectual community.

    Fall schedule: When Registration opens, you will select three or four additional courses to complete your schedule.

    Option 4: Traditional First-Year Academic Program

    With this program, you'll take your first step into the college's rich and varied core courses and explore your fields of interest in free optional coursework.

    Fall schedule: When Registration opens, you will build a schedule of four or five additional courses from the full college curriculum.

Steager is an engineer at the University of Pennsylvania. His colleague Hyun Koo is an inventor and dental researcher there. Together, they found a way to form the nanoparticles（纳米颗粒）into long, skinny bristles（鬃毛）, a lot like the ones on a toothbrush. But these bristles shape-shift to fit whatever surface they encounter. They can even squeeze between teeth.

"A new way to clean teeth could help out anyone who finds this chore boring," says Koo. But it would be especially life-changing for people with disabilities or illnesses that make it difficult or impossible to hold and move a toothbrush.

The tooth-cleaning robot works thanks to two magnets（磁铁）. One goes on each side of the teeth. The nanoparticles sit in a water-based solution between the magnets. When the magnets are turned off, the nanoparticles float randomly in the solution. As soon as one magnet gets turned on, the nanoparticles clump together near its center. When you turn on the other magnet and turn off the first one, the nanoparticles extend outward in long, skinny bristles.

When there's a tooth in the way, these bristles can't stretch out as far as they want. So they push against the tooth's surface. If there's a gap between teeth, they push into the gap. Moving the magnets makes the bristles move against and between teeth.

Besides, as a bonus, the nanoparticles can kill what harms the teeth and keep them health y because it contains something commonly added to toothpaste and mouthwash.

The new invention is just a proof of concept. The researchers still need to turn it into a product that people will want to use. It must fit comfortably and safely in people's mouths. It can't draw too much power or cost too much. "There's a lot of engineering to get from here to there," says Steager. But he adds, "every good idea needs to have a start."