THE WASHINGTON POST – Kids around the world have always drawn the sun a little differently. Americans tend to sketch a yellow circle surrounded by straight lines – sometimes with a smiley face or black shades. Japanese children might make their circle red, not unlike their country’s flag.
Now, adults are fiercely debating the colour of our solar system’s star, with some insisting it has changed hues since their childhood.
It all started last week when writer Jacqui Deevoy tweeted that the round yellow sun of her childhood had suddenly turned white and wonky looking. In a matter of days, the post amassed over six million views and divided users into two camps: those who agreed with Deevoy and those who said the sun had always looked white.
So, what colour is the giant star: yellow or white? According to science, it’s a bit of both, but also neither.
“The sun would appear green if your eye could handle looking at it,” said project scientist of NASA’s Solar Dynamics Observatory W Dean Pesnell. “Basically, when you look at the sun, it has enough of all the different colours in it and it’s so bright that everybody’s eyes are firing like crazy and saying, ‘It’s too bright for me to tell you what colour it is.’ That’s why the sun looks white to us.”
From 93 million miles away, the sun usually looks like a white spot in the sky. But the reason many people perceive a yellow tint has to do with how light is scattered, Pesnell said.
Molecules in the air redirect sunlight’s blue and violet wavelengths, allowing more yellow and red ones to hit our eyes. (This is also why the sky looks blue). As day turns into night, sunlight has to pass through a thicker atmosphere – thus, more molecules scatter its blue hues and lead to dazzling displays of oranges and reds during sunset, he added.
“Essentially,” Pesnell said, “it’s a green star that looks white because it’s too bright, and it can also appear yellow, orange or red because of how our atmosphere works.”
What we perceive as the sun’s hue is really light bouncing off surfaces. When it comes to stars, colour equals temperature, Pesnell said. The hotter a star, the more blue light it gives off, while cooler stars appear red.
With a temperature that tops 27 million degrees Fahrenheit in its core, the sun is “somewhere in the middle, in this weird space where we can’t perceive its colour”, Pesnell said – but the massive, glowing mass of gases is bound to change hues in the very, very distant future.
The sun is the source of all the light and heat that makes flowers bloom, birds sing and beachgoers smile because of the conversion of hydrogen into helium taking place deep inside its core. However, that hydrogen gas will eventually run out.
The sun will balloon and take on a deep red shade before it turns Earth and other nearby planets into snacks.
So, Pesnell said, the sun will glow bright blue for a bit – and then dim away into such a low temperature that its colour will become imperceptible.
That doomsday, however, isn’t predicted for at least four billion to five billion more years.
“The sun is at its midlife, and it still has quite a lot of years before it changes colours,” Pesnell said. “It still hasn’t dimmed out one bit.” So why are some people convinced it has turned whiter? It has more to do with the brain’s perception of the sun than astrophysics, Pesnell said. And perceptions can differ from person to person.
“When astronomers say colour, they really mean temperature,” he said. “But to anyone in the public, colour just means the colour you see and how you make sense of the world.”
In its most physical sense, colour is what people see when a wavelength enters the eye.
There, specialised cells send signals to the brain, which translates the waves into the colours we see. And though everybody is essentially receiving the same information, what we make of it is marked by individual life experiences and backgrounds, said Alice Skelton, who researches developmental colour science at the University of Sussex in England.
“We think of perception and vision as being really straightforward, with this idea of ‘I have my eyes and see,'” Skelton said.
“And actually, it’s not like that at all. It’s influenced by where you grow up, when you grow up and who you grow up around.”
Take the famous “white dress or blue dress” debate that divided the world in 2015.
People believed the garment to be one colour or the other depending on their perception, Skelton said: “It’s the same input, but what you come in with gives you different answers.
For people who are more used to being in the sunlight, the dress looked one way. For those who are more used to shadows, it looked a different way.”
The same thing happens in the Arctic Circle, where some children are born during long periods of darkness and others experience prolonged sunlight.
As adults, Skelton said, research showed their time of birth influenced their abilities to distinguish different shades. Language may also play a role, she added – with some cultures not having a word to differentiate between blue and green, for instance.