Humans are responsible for 25% to 40% more of the total share of methane emissions(甲烷排放)than previously estimated, according to a new study in Nature.

Methane is one of the most powerful and effective greenhouse gases: about 28 times more effective than carbon dioxide at trapping heat in the atmosphere. It's responsible for about a quarter of global warming. It's produced naturally by animals, volcanoes, and wetlands, but it's also a byproduct of oil and gas production. It's this last form of methane that the study focused on.

Researchers used ice core measurements from Greenland from 1750 to 2013, plus previous data from Antarctica. They melted the ice to let the small quantities of ancient air trapped inside come out. These act a bit like time capsules,allowing us to learn about the methane in the atmosphere at the time. They used carbon-14, which comes from living things, as a substitute(替代物)to determine whether the methane they found came from biological sources. Until 1870, around the time when we started using fossil(化石)fuels, almost all methane came from these sources. After that, there was a rise in methane that didn't have any carbon-14, from ancient fossil sources in which carbon-14 had disappeared. That allowed the researchers to compare natural methane with methane caused by human activity.

If more methane is created by humans, there's an even bigger opportunity to control how much we release. Methane stays in the atmosphere for only a decade(compared with 200 years for carbon dioxide). So efforts to cut methane, which mostly comes from the production and transportation of gas and oil, could bring great benefit right away.

Do you know what “zero” means? Have you ever even stopped to think much about this concept (概念)? It’s an easy one to take for granted. Of course, everyone can understand the concept of nothing, or having nothing.

But did you know that some animals can understand zero as well? Experiments with monkeys and birds have proven that they can master this concept. But now, the understanding of zero has been found in a most unlikely candidate (候选人): bees.

According to a recently published study in the journal Science, Australian and French researchers worked together to conduct experiments to prove that bees are the first insects to “understand that zero belongs at the lower end of a sequence (序列) of numbers”, according to a report by Science Daily.

Scarlett Howard, a researcher at RMIT University in Melbourne, trained bees to choose from several cards with different numbers of shapes printed on them. Correctly choosing the card with the fewest shapes earned them a reward of sugar water. For example, the bees learned to choose three elements when presented with three VS four; or two elements when presented with two VS three. And then these bees were presented a challenge — a card that was entirely blank and that they had never seen before. But 64 percent of the time, they chose to fly toward the blank card instead of the card that had shapes on it. This suggests that the insects understand that zero stands for something less than two or three, according to Science magazine.

Associate Professor Adrian Dyer, also from RMIT University, said the number zero was the basis of modern mathematical and technological progress.

He told Science Daily that the findings have opened a door to new understandings of how different brains understand zero. “If bees can understand zero with a brain of less than a million neurons (神经元) [compared with the 86,000 million neurons of a human brain], it suggests there are simple and efficient (有效的) ways to teach artificial (人工的) intelligence new tricks .”

Jeffrey Hall, a professor at the University of Kansas, came up with the Communicate Bond Belong theory, which states that we all feel the need to belong and that both the amount of time and the type of activity shared with a partner are key investments to help us meet that need.

Hall set out to quantify(量化)the requirements of friendship in two separate studies. The first included 355 adults who had moved to a new place within the previous six months. Hall asked them to identify someone new they had met. It couldn’t be a family member, romantic interest, or someone they’d known previously. The participants told where they met this person, how much time they’d spent together the previous week and how much time they spent together in a typical week. They also classified the person from acquaintance(熟人)to best friend.

In the second study, Hall invited 112 University of Kansas freshmen and asked them to name two new acquaintances. Then he followed up twice over the first nine weeks of the school year to measure time spent with those new acquaintances and see how the relationships had changed.

The results of both studies confirmed that time spent together was associated with closer friendships. “I was looking for cut-off points, ”says Hall, “where there was a 50% greater likelihood you switch from acquaintance to casual and from casual to friend, then again from friend to best friend. ”He found that it took about 50 hours of interaction to move from acquaintance to casual friend, about 90 hours to move from casual friend to friend, and more than 200 hours to qualify as best friend. Those who never got beyond being acquaintances usually had spent no more than 30 hours together.

On the other hand, time together didn’t automatically(自动地) make two people friends. Some adults reported spending more than a thousand hours with colleagues but still called those people acquaintances. Basically, they just didn’t like them very much. Or they had no relationship outside of work.