Every summer, the calls of thousands of swamp sparrows can be heard across North America's wetlands. These little brown birds know only a few songs, but they know them very well. In fact, their musical set list probably hasn't changed much for centuries.

Like humans, baby swamp sparrows learn to communicate by copying adults. From a young age, they learn to copy, or mimic, songs sung by their elders. "Swamp sparrows very rarely make mistakes when they learn their songs," says biologist Robert Lachlan. In fact, their mimicry is so accurate that the music changes little between generations.

Just like children, the sparrows don't remember every song they hear. Lachlan says. "They don't just learn songs at random; they pick up commoner songs rather than rarer songs." In other words, they learn songs they hear most often. It's an example of a strategy that scientists call conformist bias. Until recently, this learning ability was thought to be special only to humans.

Between 2008 and 2009, Lachlan's research team recorded the calls of 615 male swamp sparrows across the northeastern United States. The researchers used computer software to break each song into a collection of notes, or syllables. They then measured the differences between the tunes.

The research revealed that only 2 percent of male sparrows sang a different song from the standard tune. The combination of accurate mimicry and conformist bias allows the birds to create traditions that last for centuries. "With those two ingredients together, you end up with traditions that are really stable," says Lachlan. "The song-types that you hear in the marshes（湿地）of North America today may well have been there 1,000 years ago." Lachlan's study is also among the first to measure the longevity of song traditions within a bird species.

The findings are really exciting, says scientist Andrew Farnsworth. He hopes that future research will evolve from these studies. For example, scientists may be able to identify how other animals are able to preserve their cultural traditions. "Seeing the potential for it in other organisms is super cool," says Farnsworth.

The sounds of the Northern Lights have been a mystery to scientists for over a century. But now it seems that a researcher has figured out how auroras (极光) really make sounds. "It has pretty much been confirmed all over the world," "historian Fiona Amery said. "In Canada, Norway and Russia, they are all hearing very much the same sounds." "The auroras can occur hundreds of kilometers above the ground, which strengthens opinions that their sounds are just a false impression," said Fiona. Many scientists argued that auroras were too far away to hear and that any sound would take several minutes to reach the ground, so it was impossible for them to change in time with the auroras.

However, other scientists were convinced that the Northern Lights really made noises. In the 1920s, Canadian astronomer Clarence Chant first suggested a mechanism by which they could occur: The motion of the aurora caused changes in the electrification of the atmosphere that created crackling sounds close to the ground. Almost 100 years later, Clarence's suggestion seems close to what could be the true reason for the sounds.

In 2012，an expert named Unto Laine showed a recording of auroral sounds after years of monitoring auroras. In 2016, he announced the mechanism that makes the sounds: an inversion layer(逆温层) of cold air in the atmosphere that can form below an aurora and a short distance above the ground in calm weather.

Unto argues that visible changes in the aurora cause changes in the inversion layer, causing accumulated electricity to discharge as sparks (火花) that create sounds that can be heard. That explains how the sounds correspond with the aurora 's visible movements 一they begin to happen in the inversion layer only about 75 meters above the observer.

Have you ever been told to, "go your own way" when faced with a dilemma? We all roll our eyes and say we will, but if only we meant it…

No matter how often it's repeated, let's all face it — we naturally tend to mirror the behaviour of those in our surroundings. While it's not a good nor a bad habit, I believe we should reflect on how much we let others impact us. Why? Because we're independent people and we can choose for ourselves.

Jim Rohn, a motivational speaker, said, "You are the average of the five people you spend the most time with." This means our close circle of peers can be seen as parts of ourselves. That's why I often find it difficult, even now, to go against my family's or friends' opinions, because they're the people I care for most and don't want to disappoint.

When I was around nine years old, I went to a summer camp where I met lots of other kids. At dinnertime, we'd all gather around in the cafeteria. At some point, my group of friends and I decided to throw a competition of "who could drink the most glasses of water." Little me, very competitive and careless, drank 14 glasses of water in the span of 20 minutes. Obviously, I was encouraged by my friends, who were cheering me on and laughing. As the night went on, my body suffered from loss of minerals, which caused me to collapse and be rushed to the hospital. Thankfully, I didn't experience any long-term effects from that night, but you can imagine how far it can quickly go.

It's the idea of belonging to a group that's tricky, because we can become vulnerable (脆弱的) to the people we open ourselves up to. One universal truth I'm convinced of is real friends will always respect your choices. It doesn't matter what's at risk — if you've thought through the pros/cons and don't want to do something, you shouldn't do it. Your true friends shouldn't force you to do anything. You're the master of your own choices.

I think, most of the time, our friends are the people we think most alike. However, I don't let the "awkward" moment of saying "no" overshadow my power over myself, because I know I'm first and foremost loyal to my values and beliefs. In the end, I realize it's not my peers who raise my hand to drink water or smoke weed. I'm the one who faces the consequences of my actions, not my friends. And that's what I try to remember in my everyday life.