【推荐1】Space settlement is widely debated. Some argue living in space is unrealistic and that we should concentrate on improving life on Earth instead of potentially ruining another planet.

Taking living on Mars as an example, some scientists think it is a fantasy. To make it, Mars needs to first be warmed to closer to Earth’s average temperature, which will take about 100 years. Then the planet must be made to produce oxygen, which will take 100,000 years or more. A 2018 NASA study concluded that, based on the levels of CO2 found on Mars, the above plan is not practical. If a solution were found and conducted, a project of that magnitude would cost billions, perhaps trillions(万亿).

Besides, humans have made a mess of Earth. If humans are able to change an uninhabitable planet in space into an appealing home for humans, surely we have the capability to fix the problems we’ve created on Earth. John Traphagan, Professor at the University of Texas, argued, “We need to stop holding the belief of human exceptionalism and start seeing humans as part of a collection of species. As long as we bring it with us to other worlds, we will repeat the same mistakes.”

However, others argue humans have a moral obligation to save our species from extinction, and space settlement is one way of doing so. According to some philosophies, humans are the only beings capable of morality, and, thus, preserving our species is the most morally pressing. Space settlement gives humankind the opportunity to significantly raise the chances of survival by providing access to the solar system’s resources, and increasing knowledge of space and Earth.

Space settlement is the next logical(合理的)step in human growth. Humans are not a species to stand still. Jeff Bezos, who traveled to space in 2021, stated, “The solar system can easily support a trillion humans. And if we had a trillion humans, we would have a thousand Einsteins and a thousand Mozarts and unlimited, for all practical purposes.”

【推荐2】We have been taught from a young age that red means stop and green means go. So why were these colors chosen for traffic lights? And what’s the history behind the colors?

To trace the connection between the colors and traffic lights,we have to travel back in time to the earliest railroad signals (信号灯) developed in the 1830s. Those first railroad signals were the forerunner of our modern stoplights. Like modern traffic controls,they contained three lights:one for stop,one for caution (警告),and one for go. The original color system was different from our modern system,though. Red meant stop,green meant caution,and white meant go.

The choice of red for stop was fairly obvious,since red — the color of blood — has been associated with danger for thousands of years, long before cars were even around. Scientifically speaking,red is the color with the longest wavelength which means that as it travels,it gets spread less in different directions than other colors,so it can be seen from a greater distance.

Why green and white were chosen for the other signals remains a bit of a mystery. It’s possible that the two colors were chosen because how they contrasted (反差) with red. This system of color-coded signals remained in place (仍然有效) for several decades until it became clear that using white for go could cause serious problems. Around 1914,a train signal’s red lights broke down,causing it to appear white. As a train approached the signal,it was supposed to stop,but the driver believed the white meant go. The result was a terrible train crash. After that,the color for go was eventually changed to green.

To provide the most contrast between red and green,yellow was then chosen as the new color for caution,because it can be seen well at all times of the day. After cars were invented and went into mass production,a similar signaling system was needed to control the flow of traffic. When traffic lights were put up,it became standard for them as well.

【推荐3】In many adults, learning and thinking begin to decline (衰退) as early as age 30 and become worse in their mid-60s, which is shown in tests of cognitive(认知的) abilities.

These changes are often considered as the result of normal aging. But they may instead show something more like the “summer slide” that some schoolchildren experience in study process during summer break. After formal education and job training end, many adults experience years of reduced chances of learning.

However, a three-month study Rachel Wu and her partners designed suggests that this decline can be addressed. In this study, they provided an encouraging learning environment for 24 older adults between 58 and 86 years of age. Before and after, they tested the cognitive abilities. The older adults signed up for at least three classes that met weekly to learn new skills, such as drawing, iPad using and Spanish-language learning. During this period, the adults’ cognitive scores for memory improved greatly, and their cognitive abilities after one year were similar to those of adults 50 years younger.

The team is still investigating why their cognitive scores continued to climb after the program’s end, but one possibility is that the experience encouraged these adults to continue learning and practice new skills. To be clear, the researchers do not think that formal education is the only or most important way to support learning. Their idea is to instead create encouraging environments for older adults, so they can increase both real-world skills and cognitive abilities over the long term.

“Use it or lose it,” the saying goes. Let’s change the conversation about adults from avoiding loss and decline, or keeping what people have, to learning and growing.