Across the developing world, homeowners, farmers, and businesses are turning to cheap, secondhand solar to fill power gaps left by governments and utilities. To meet that demand, businesses ranging from individual sellers on Facebook to specialized brokerages are getting into the trade.

Earlier this month, Marubeni Corp., one of Japan’s largest trading houses, announced that it’s establishing a blockchain-based market for used solar panels（太阳能板）. Collectively, these businesses will likely play a crucial role in bringing renewable energy to the world’s emerging markets（新兴市场）—and keeping high-tech waste out of the trash.

In 2016, the International Renewable Energy Agency estimated that as much as 78 million tons of solar-panel waste will be generated by 2050. That’s almost certainly an undercount. Over the past decade, falling prices and improved efficiency in newer models have offered a strong incentive to replace solar panels earlier than their intended lifespan. By one estimate, those upgrades could lead to 50 times more waste than the agency has predicted within five years.

In developed countries, recycling-not reuse and resale-tends to be the natural response to managing such waste. But there are two problems with recycling unwanted solar panels. First, doing so is far costlier than simply burying them. Second, waste solar panels often aren’t waste, they’re just degraded by time in the sun or less efficient than newer models. They may not be good enough for San Francisco homeowners and advanced utilities, but they work perfectly well for anyone in a sunny climate in need of stable, off-grid（离输电网）power who doesn’t want to pay full price.

That’s potentially a huge market. Between 2010 and 2019, the number of people living without electricity declined from 1.2 billion to 759 million in developing countries. Some of that gap was closed by new power lines and other transmission facilities. But most of it was achieved by installing used solar panels to power a village, farm or even a single home. As of last year, 420 million people got their electricity from off-grid solar systems. By 2030, according to the World Bank, that number could nearly double.

It’s a popular belief that a fish’s memory lasts for only seven seconds. It may seem sad to think that they don’t remember what they’ve eaten or where they’ve been, and they don’t recognize you or any of their friends---every moment in their life would be like seeing the world for the first time.

But don’t be so quick to feel sorry for them. A new study has found that fish have a much better memory than we used to think. In fact, certain species of fish can even remember events from as long as 12 days ago.

In the study, researchers from MacEwan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They then waited for 12 days before putting them back in the tank again.

Researchers used computer software to monitor the fish’s movements. They found that after such a long break the fish still went to the same place where they first got food. This suggested that they could remember their past experiences.

In fact, scientists had been thinking for a long time that African cichlids might have a good memory. An earlier study showed that they behaved aggressively in front of certain fish, perhaps because they remembered their past “fights”. But until the latest findings, there was no clear evidence.

Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild.

“If fish are able to remember that a certain area contains safe food, they will be able to go back to that area without putting their lives at risks,” lead researcher Trevor Hamilton told Live Science.

For a long time, fish were placed far below chimpanzees, dolphins and mice on the list of smart animals. But this study has given scientists a new understanding of their intelligence.

Dopamine (多巴胺) is often considered as the source of pleasure. But that’s not quite what it does. Dopamine is what makes us desire things. And it’s that desire that gives us the motivation to get up and do things.

In fact, your brain considers something more important than others mainly depending on how much dopamine it’s expecting to get. If an activity releases a lot of dopamine, you’ll be motivated to repeat it, over and over. So which behavior releases dopamine? Any activity where you expect there’s a possible reward releases it.

And in today’s digital society, we are flooding our brains with unnaturally high amounts of dopamine on a daily basis, even if we don’t know it. Some examples of high dopamine behavior include: visiting social media websites, playing video games, etc.

And you might think, “Oh so what? It’s not like it’s harming me in any way.” But you’d be wrong. Our bodies have a biologically balanced system. Whenever an imbalance occurs, our body adapts to it. Basically, your brain gets used to having high levels of dopamine and those levels become your new normal. Thus, you develop a dopamine tolerance. This can be a huge problem because the things that don’t give you as much dopamine don’t interest you any longer. That’s why people tend to prefer playing video games or surfing the Internet, compared to studying or working on their business.

But it is possible to make doing difficult things feel easier. Separate yourself from the unnaturally high amounts of dopamine, or at least expose yourself to it far less frequently. Only then will normal, everyday, low dopamine activities become exciting again and you’ll be able to do them for longer. That’s why you might want to limit your phone and computer usage, along with other high dopamine-releasing behavior.

We are all dopamine addicts to a certain extent. And that’s a good thing because dopamine motivates us to achieve our goals and improve ourselves. But it’s up to you to decide where you’re going to get your dopamine.