The science behind fall's brilliant colors  November 19, 2025

 

What's up, sunshine? I'm Coy Wire. This is CNN 10, your 10 minutes of news where I tell you the what, letting you decide what to think. Special hello to our friends way up in northern Alaska today, or shall we say tonight.

 

The city of Utqiagvik entered its polar night season yesterday, meaning the sun set there for the last time until January 22nd. Around the clock darkness, they'll still shine bright. Rise up.

 

polar night 极夜，又称永夜、夜昼、月昼

 

We begin today's news at the White House, US President Donald Trump hosting Saudi Arabia's Crown Prince Mohammed bin Salman. Yesterday, the president has worked to build closer ties with the prince who last visited the US during Trump's first term in 2018.

 

The visit was marked by a lavish welcome ceremony, an oval office bilateral meeting or discussion between two parties and a black tie dinner.

 

black tie （晚礼服佩戴的）黑领结; 礼服; a semi-formal Western dress code for evening events

 

The president's efforts to foster a better relationship with the de facto leader of the Saudi kingdom has brought mixed reviews.

 

de facto【法】事实上（的）

 

Numerous organizations have accused bin Salman's regime of human rights abuses, including the 2018 killing of journalist Jamal Khashoggi. The regime has denied those claims.

 

Ahead of the visit, President Trump announced the US will sell F-35 fighter jets to the Saudis, a move experts say could alter the balance of military power in the region.

 

President Trump sees Saudi Arabia as a key ally in the Middle East, and his office has worked towards having them sign on to his signature Abraham Accords with the goal of normalizing their diplomatic ties with Israel.

 

signature [ˋsɪgnətʃɚ] adj. 代表性的

 

In London, teens from across the UK took part in the annual British Youth Parliament, debating a copious amount of topics.

 

copious [ˋkopɪəs] adj. 丰富的，大量的

 

The annual session was held in the House of Commons, and the young politicians argued things like housing, climate change, and public transport.

 

House of Commons 英国下议院

 

Our presence here is more than just an inspiration, but it is a hope, a vision, a dream that no matter who you are, the future is in your hands.

 

The program was started in 1999.

 

It has more than 300 members ages 11 to 18 who are elected every two years to represent views of their generation. Elections often take place in schools across the country. The initiative is funded by the government's Department of Culture.

 

It aims to introduce younger generations to the world of policymaking and parliamentary process.

 

Big changes coming to Roblox, and they affect anyone who wants to chat with other players on the gaming platform.

 

Roblox says users will soon be required to verify their age, either by uploading a government ID or letting an AI tool scan their face.

 

verify [ˋvɛrə͵faɪ] v. 证明，证实；核对

 

The new system would use your device's camera and ask you to move your face in different directions so that AI can estimate your age.

 

It then sorts players into age groups and limits your ability to chat only with the people who are in or near your age group.

 

Roblox says the tech usually accurately estimates your age within a year or two, and parents can correct their child's age if needed.

 

Roblox has more than 150 million users worldwide. About a third of them are under the age of 13. The company calls the move a major step toward keeping kids safer and reducing unwanted or inappropriate contact between players.

 

Pop quiz, hot shot. What is the job of a lexicographer?

 

lexicographer [͵lɛksəˋkɑgrəfɚ] n. 词典编纂者

 

Engineer cogs or gears, write poetry, compile and edit dictionaries, or analyze handwriting?

 

cog [kɑg] n.【机】钝齿

 

If you said compile and edit dictionaries, put your picture next to correct. Lexicographers use corpus linguistics to decide which new words to add to dictionaries.

 

corpus [ˋkɔrpəs] n. 文集；全集；主体

corpus linguistics 语料库语言学

linguistics [lɪŋˋgwɪstɪks] n. 语言学

 

They examine words, phrases, and grammar patterns in books, articles, even social media to uncover how people communicate.

 

Oh, Wolf, you're such a great listener. That's a parasocial relationship.

 

parasocial [͵pærəˋsoʃəl] adj. 拟社会的，准社会的

 

Oh my God, he's right. Parasocial is Cambridge Dictionary's word of the year for 2025. If you've ever felt like you've personally known a celebrity, an influencer, or something like Chat GPT, well, that's a parasocial relationship.

 

It's actually been around since the 1950s.

 

Another example of this is Travis Kelce and Taylor Swift's engagement, where millions of fans felt this deep emotion for a couple that they've never even met.

 

engagement [ɪnˋgedʒmənt] n. 订婚；婚约

 

And by the way, the dictionary also added 6,000 new words, including tradwife, dilulu, and skibidi.

 

tradwife: short for traditional wife

dilulu 妄想;不切实际

skibidi [ˈskɪbɪdi] adj. a word that can have different meanings such as "cool" or "bad", or can be used with no real meaning as a joke

 

Welcome to the internet.

 

We're just about halfway through the fall season, and many of us here in the northern hemisphere might be noticing Mother Nature is just showing off. Fall foliage colors are popping, with trees starting to turn brilliant shades of yellow, red, and orange.

 

Have you ever wondered why and how the leaves change colors? Who better to ask than our CNN meteorologist, our weather wizard, Allison Chinchar. So great to see you. Looking fall-tastic today with your display.

 

Speaking of display, how do these leaves change color? Why do they change color? And how do they know when to start?

 

Right, because sometimes they change a little bit later in the year versus others. So yeah, there's a lot of factors here, Coy. But the biggest one is daylight hours.

 

As the days start to get shorter and we have less and less daylight as we head into winter, it's essentially kind of a cue to them to stop photosynthesizing. Now, photosynthesis is basically using the sunlight to give them food and energy. But this process slows incredibly in the winter months.

 

cue [kju] n.【戏】提示，尾白；暗示，信号；线索

photosynthesis [͵fotəˋsɪnθəsɪs] n. 光合作用

 

So the trees aren't dying. They're just going dormant.

 

Why do some leaves turn red, like this one? Right.

 

So not all trees have this special gift that allows them to be this beautiful color. Basically, what they have inside of them is something called anthocyanin.

 

anthocyanin [͵ænθəˋsaɪənɪn] n. 【植】【生化】花青素

 

And it allows these trees, when they start to go through that photosynthesis process in the winter, when they slow down, they're changing into this beautiful red, or sometimes even that pretty purple color, all because they have this special ingredient.

 

But you also have to have the right weather conditions. You have to make sure you've had enough water leading up to the fall season and also plenty of sunlight.

 

Now, why is it that some trees don't change colors and nothing falls?

 

Right. So these are what we refer to as evergreen, hence the color, trees. Basically, these trees have evolved so that they never stop going through the photosynthesis process.

 

refer to .. as 把…称为…

 

Now, it slows considerably in the winter, but it never actually stops, meaning they don't have to lose their leaves or change their color.

 

In this warming climate environment that we're living and we're experiencing nowadays, how might warming temperatures around the world affect the changing colors of the leaves?

 

Right. So the most obvious answer to that is the leaves will be falling off much later into the season because we're staying warmer longer.

 

f trees could actually pick their ideal conditions, it would be for the temperatures to cool down gradually, like you and I would probably pick.

 

But if temperatures drop too quick, let's say 30 to 50 degrees in just a couple of days, trees can go through what's called shock, which causes them to just drop their leaves, even if they never ended up fully changing colors.

 

So why do trees decide to let their leaves go? Is this like a preservation thing that some they have to do?

 

It's to really save a lot of the energy that the tree would use up during the winter. Many people don't know this, but leaves take up the vast majority of the water source that a tree takes in.

 

So if it doesn't have its leaves anymore, it can consolidate a lot of that energy to get through a rough winter.

 

consolidate [kənˋsɑlə͵det] v. 合併，聯合，統一; 巩固，加强

 

Thank you for helping us branch out today and get to the root of this very interesting topic.

 

branch out 向新的方向扩展自己的活动或兴趣

get to the root of something: to understand the cause or source of something

 

Today's story getting a 10 out of 10, a VIP, a very important porpoise making a splash in the canals of Venice, Italy.

 

porpoise [ˋpɔrpəs] n. 海豚；鼠海豚

make a splash 引起轰动; 惹人注目

 

A dolphin nicknamed Mimmo has people flippering out as it swims among the gondoliers in the St. Mark's Basin.

 

flipper [ˋflɪpɚ] n. 鳍状肢 (flippering ou t雙關語)

flip out 精神错乱, 情绪激动, 发疯,疯狂

gondolier [͵gɑndəˋlɪr] n. 操平底船的船夫

 

He's been drawing attention and adoration since the summertime, creating loads of dolphin fans along the way. The only other time a dolphin has been seen in this area was at the tail end of the COVID-19 pandemic in 2021, when boat traffic was low.

 

According to officials, Mimmo appears to be showing up on porpoise. He's fed and fawned upon and unfazed by the noise of boats and crowds.

 

fawn [fɔn] v. (狗等动物）向…摇尾乞怜[+ upon]

unfazed [ʌnˈfezd] adj. 不受干扰的；不担忧的；不为所动的

 

That's quite the phenomenon.

 

Congrats to our Your Word Wednesday winners, Mr. Senra and friends at Dawes Elementary School in Evanston, Illinois, who submitted copious, an adjective meaning abundant in supply or quantity.

 

Thank you for making us smarter today. Also, thanks to all of you who have been sending us copious amounts of swag.

 

As you can see, Miss Sabrina went with a bit of a t-shirt theme today. And speaking of t-shirts, we have a good one for our shout out of the day. This one goes to Mr. Williams, Coach Williams, and our soccer state champions at Bethany High School in Bethany, Oklahoma.

 

Salutations, congratulations, and keep bucking Broncos. Go make it an awesome day. Make someone smile today.

 

salutation [͵sæljəˋteʃən] n. 致意；行礼

buck [bʌk] v.（马等）猛然弯背跃起

 

I'm Coy Wire, and we are CNN 10.