In the traffic lights,red means "stop",green means "go",and yellow means "hurry": Why those colors, though? Why not blue,purple,and brown?The following are transponded from others WeChat.

●Red is an inherited symbol from railroads

    Red symbolizes danger in many cultures,which makes sense,considering it has the longest wavelength of any color,meaning you can see it from a greater distance than other colors.Red has meant "stop" since long before cars existed,with railway signals use of red dating bake to the days when mechanical arms lifted and lowered to indicate whether the rail ahead was clear.So that one's simple.

●Green meant "caution" at first

    Green's role in lights has actually changed dramatically over time.Its wavelength is next to (and shorter than) yellow's,meaning it's still easier to see than any color other than red and yellow.Back in the early days of railway lights,green originally meant "caution",while the "all-clear" light was,well,clear or white.Trains,of,course,take an unlimitedly long time to stop,and legend has it that several disastrous collisions happened after an engineer mistook stars in the night horizon for an all-clear.Thus,green became "go",and for a long time,railways used only green and red to signal trains.

●Yellow means "caution" because it's almost as easy to see as red

    From the earliest days of motoring up until the mid-1900s,not all stop signs were red-many were yellow, because at night it was all but impossible to see a red stop sign in a poorly lit area.The yellow stop-sign craze began in Detroit in 1915,a city that five years later installed its first electric traffic signal,which happened to include the very first amber traffic light,at the corner of Michigan and Woodward Aves.

    America is a mobile society. Friendships between Americans can be close and real, yet disappear soon if situations change. Neither side feels hurt by this. Both may exchange Christmas greetings for a year or two, perhaps a few letters for a while - then no more. If the same two people meet again by chance, even years later, they pick up the friendship. This can be quite difficult for us Chinese to understand, because friendships between us flower more slowly but then may become lifelong feelings, extending (延伸) sometimes deeply into both families.

    Americans are ready to receive us foreigners at their homes, share their holidays, and their home life. They will enjoy welcoming us and be pleased if we accept their hospitality (好客) easily.

    Another difficult point for us Chinese to understand Americans is that although they include us warmly in their personal everyday lives, they don't show their politeness to us if it requires a great deal of time. This is usually the opposite of the practice in our country where we may be generous with our time. Sometimes, we, as hosts, will appear at airports even in the middle of the night to meet n friend. We may take days off to net as guides to our foreign friends. The Americans, however, express their welcome usually at homos, but truly can not manage the lime to do n great deal with a visitor outside their daily routine. They will probably expect us to get ourselves from the airport to our own hotel by bus. And they expect that we will phone them from there. Once we arrive at their homes, the welcome will be full, worm and real. We will find ourselves treated hospitably.

    For the Americans, it is often considered more friendly lo invite a friend to their homes than to go to restaurants, except for purely business matters. So accept their hospitality at home!

    Legal information on call

    I just celebrated my 95th birthday last week, and people always ask me about my secret. Of course, it's important to eat right and exercise, but that's not much of a secret. I actually have quite a few friends over the age of 90, and we all say the same thing: laughter. Are we telling jokes all the time? Not necessarily. Are we watching funny movies around the clock? Of course not. Do we take the time to laugh at ourselves and generally try to keep things light as much as we can? Certainly. One of the best ways to make sure you laugh every day is to be around children or pets because they just can't help being funny! And what about those polite little laughs when your neighbor tells a joke that isn't really funny, but you laugh anyway? Those are fine, but the ones where you laugh with your whole body and mind are the ones where you end up tired and out of breath, where everyone around you starts laughing, too. My “senior” friends and I even came up with a nice round number: For each full “belly laugh” you have, you'll live one extra hour in your lifetime. Now that might not sound like much, but if you have one every day, you'll live an extra three or four years. I try to have between five and ten of those laughs every day, and so should you.

    We've heard of robots and AI（Artificial Intelligence）taking human jobs, but I bet mayors（市长）don't really think their jobs can be threatened any time soon. They were wrong, and the AI running for the mayor of a Tokyo district was clear proof of that.

    AI can't legally nm for high-ranking public management positions yet, but one mayoral candidate from Tama City, Tokyo, intended to maximize the use of artificial intelligence in running city affairs. He was running his campaign （竞选运动） as "AI Mayor". Basically, he was suggesting replacing human public officials with AI and having them collect city data and create fair and balanced policies that will benefit everyone.

    "For the first time in the world, AI will run in an election," human candidate Michihito Matsuda announced on Twitter. "Artificial Intelligence will change Toma City. With the birth of an AI Mayor, we will conduct balanced politics."

    The AI Mayor was campaigning very much like its human competitors. Posters were shown all over Tama City and campaign trucks were blaring out（大声鸣响）promises of an AI utopia （乌托邦）and asking for support.

    Some people called Michihito Matsuda's campaign a stunt （噱头）, as a human would still be the one legally in charge. However, others said that they were excited about the future of AI running things in the background, adding that it had to be a better choice.

Plants, and the insects which rely on them, are the living foundations of our planet. But these foundations are under stress because we have a tendency to replace fields and forests with decorative trees and shrubs imported from around the world. Adding to the problem, our obsession (痴迷) with perfection leads us to use a lot of pesticides (杀虫剂).

These actions are part of the reason global biodiversity is crashing. There are over three billion fewer wild birds in North America than there were in 1970. Recent research shows that insect numbers, even in nature reserves, have fallen, and 40 percent of all insect species may be extinct within a few decades. This is discouraging news; however, there are actions we can take to help bring at least some species back.

The first step is to redefine our concept of "garden" to include more than just plants. We need to intentionally share our space, and not just with the birds, bees and butterflies that visit our flowers, but also with the little insects that may eat a part (very rarely all) of our plants. Therefore, we must limit pesticide use. It's crucial to support nature's recovery, and it's much better for everyone: no doctor has ever recommended long-term exposure to pesticides.

Many drought-tolerant plants brought in from across the planet are being passed off as ecofriendly. However, mostly they're not. Yes, you're saving water, but these foreign plants can become disasters when they escape our yards. Helping the environment can be about more than saving water. Even in drier areas, like the American West, the selection of attractive native plants to choose from is vast. If dry is your style, there are native wildflowers, flowering bushes and trees that allow you to save water and nature.

Xeriscapes (节水型园艺) leave many gardeners thirsting for green, and there's an important alternative that has been largely ignored. For those disenchanted with dry landscaping, using underappreciated and water-loving native plants to make your garden a real-life oasis (绿洲) could be lifesaving to wildlife. In nature, this unsung group of native plants is limited to riparian zones, the narrow belts of green along water bodies, but if consumers demand them, nurseries will increasingly carry these riparian species, and the presence of such plants in the garden will provide for many animals including not just butterflies and their relatives but also colorful birds.

The ideal garden would offer a combination of drought-tolerant native plants and a few species that need a little more water, providing options for little guests and the bigger ones that will come to eat them. As more creatures stop by to share our yards, we will be making nature, and us all, a little healthier.