【推荐1】Plant-eating dinosaurs probably arrived in the northern half of the world millions of years after meat-eating dinosaurs, a recent study found. Their late arrival was likely a result of climate changes that took place hundreds of millions of years ago.

The study used a new way to ascertain the age of dinosaur remains found in Greenland. Researchers found that the plant-eating dinosaurs were about 215 million years old. The mineralized（石化的）remains of bones are called fossils. Earlier, those fossils were thought to be as old as 228 million years. The findings could change how scientists think about dinosaur movements, or migrations.

The earliest dinosaurs all seemed to first develop about 230 million years ago or longer. They appeared in what is now South America. Then, the creatures moved north and spread all over the world. The new study suggests not all dinosaurs moved at the same time.

So far, scientists have not found any evidence of plant-eating dinosaurs living in the Northern Hemisphere before 215 million years ago. One of the best examples of these is the Plateosaurus, a two-legged, 7-meter-long plant-eater that weighed around 4,000 kilograms. However, meat. eaters lived worldwide by at least 220 million years ago.

During the Triassic（三叠纪）period, 230 million years ago, CO₂ levels were 10 times higher than now. The Earth was hotter with no ice sheets at the poles and two areas of extreme deserts north and south of the equator（赤道）. It was so dry in those areas that there were not enough plants for the plant-eaters to survive. But there were enough insects so that meat-eaters could.

About 215 million years ago, CO₂ levels dropped. The drop resulted in more plant life in the deserts. The plant-eaters were then able to make the trip. Triassic changes in CO₂ levels were from volcanoes and other natural forces. The changes were different from those in our times, when the burning of coal, oil and natural gas are considered the main causes of climate change.

【推荐2】Your cat is probably keeping track of where you are, even if your feline (猫科的) friend isn’t in the same room with you and can’t see you.

Scientists recently learned that house cats create “mental maps” that tell them where nearby humans are located, based on where sounds are coming from. The researchers tested cats by playing recordings of human voices calling the cats’ names; they then played those recordings again, only this time through a speaker in a different place, so that the same sounds came from farther away. The cats acted surprised when the familiar voice came from a location that they didn’t expect, based on what they had already heard. This suggests that cats spatially (空间上) locate their unseen human companions using audio cues—a cognitive (认知) ability that was previously unknown in felines.

Knowing that something continues to exist even if it’s out of sight is called object permanence, and it’s a test that researchers use to measure animal intelligence. Human babies typically begin to develop object permanence when they’re around 8 months old, and this ability becomes more advanced when babies reach 10 to 12 months old; at that stage, babies can find hidden objects, and they begin to realize that their parents and caregivers don’t disappear just because they can’t be seen, a ccording to the Mayo Clinic.

In other studies, cats have also shown that they can distinguish between familiar and unfamiliar human voices and that they can orientate hidden objects. So “it seems reasonable that cats should be able to mentally map others’ locations based on sounds,” the scientists said in the study.

Being able to form a mental picture of the outside world “is an important feature in complex thinking,” and these findings put the study in a new light, which could inform future studies of feline cognition, the study authors concluded.

【推荐3】Every year, millions of birds are killed or hurt when they fly into buildings. Why does this happen?     1     Birds are flying into windows and tall buildings that are all covered by glass.

Many birds fly from one place to another. Most of the time, they live in the wild, such as forests and wetlands.     2     They might see small trees and flowers inside a window and want to rest on these plants. The birds do not know there is glass between them and the plants.     3    

Some birds fly at night. They use the moon and stars to help guide them in the right direction. Tall buildings with lights on at night can confuse the birds.     4     The birds see the light, but they cannot tell that the light is coming from inside a building. They fly toward the light and crash into a building. On many mornings, there might be several dead birds lying on the ground.

    5     Many office buildings now turn off their lights at night. This helps reduce the number of birds that fly into buildings and it also helps save energy.

【推荐3】Is Big Tech Losing Its Appeal?

Pizza stations, gyms, headquarters designed by world-famous architects, and the promise of a brilliant career that also has the potential to solve world problems.     1    But is its status starting to change?

It a well established that those aged between 18 and 24 are looking for more purpose in their work. “Purpose” can be defined in a few ways, but it often comes down to having high-level vision and a sense of personal impact.    2    . If tech workers don’t want to feel like a cog (轮齿) in an enormous machine, they no longer need to. There are many alternatives available.

    3     According to Hired. com, their average salary globally is $135,000. However, the culture of long hours (probably fueled by those free pizzas) has lost its appeal among the younger generation as they seek a better work-life balance. For those who stay in Big Tech, it is not hard to realize that the cost of living in big cities increasingly cancels out much of the amazing salary on offer.

    4     There is a monoculture in Silicon Valley. Employees often do not interact with anyone until they get to the office. They do not experience the real world and yet they are supposed to-in Facebook’s case-be serving a community of 2.5 billion. I find that really troubling. They need to be given more time and resources to think about the impact their products may have on society.

Despite these problems, the vast majority of tech workers still believe technology is a force for good. They could be a key force that helps to form the much-needed change of Big Tech companies. Empowering (赋权) them with “positive dissent (异议)” could be the way to keep them.    5    

【推荐1】Some people will say that you can place a value on anything. We may know the price of milk. We can also find out the value of the most expensive building in the world. Do you think it is possible to put a price on the Earth or other planets?

You probably think this is impossible. Scientist Greg Laughlin thought differently. In March 2009, NASA sent the Kepler telescope (望远镜) into space to explore the Milky Way galaxy and to find Earth-sized planets orbiting (环绕) other stars. As there are billions of stars within the Milky Way, it could mean there were several thousand planets to discover. How could scientists decide which ones to study further and which ones to take no notice of?

Professor Laughlin used information received from the Kepler telescope to create a formula (公式) that puts a price on planets. The age and size of each planet, its temperature, and the energy (能量) it created were considered. Older planets were given a higher value. The most important consideration was whether or not it may be possible for life to live on the planet.

By using his formula, Professor Laughlin found that planet Earth was the most important. He gave it a value of five quadrillion (千的五次幂) dollars. Mars was given a value of US$16,500 and Venus was valued at zero. That’s because it’s impossible to support life on Venus because it is too close to the Sun. The professor said that any planet that had a value of more than US$100 million was worth studying further.

By November 2018, about 1,200 planets in total had been looked at. Most of them were worthless because of their unsatisfactory conditions. So should you run to the bank and borrow US$16,500 so you can buy Mars? Maybe not today. You should just enjoy the five quadrillion dollar planet you already live on — and learn how to look after it.