What is the green flash?

A brief green glow at the edge of the setting or rising Sun

The atmosphere bending colors by different amounts

Why can green be the last color seen?

It is bent more than red and yellow

Where is it easiest to see?

Over a clear, distant horizon like the sea

What can make flashes more striking?

Mirages from temperature layers

Why is care needed when watching?

Looking at the Sun can harm eyes

Green Flash Quiz: The Sunset's Last Emerald Spark

This green flash quiz watches the last sliver of the Sun slip below a clear sea horizon. Play 10 interactive questions on how the atmosphere bends colors by different amounts, why green is the last color seen, why blue is usually scattered away, flashes lasting a second or two, mirages that stretch them, the best clear horizons and Jules Verne's novel The Green Ray.

Start Green Flash Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

What
What is the green flash?
Cause
What causes it?
Last
Why can green be the last color seen?
Blue
Why don't we usually see a blue flash?
Length
How long does a green flash usually last?
Horizon
Where is it easiest to see?
Mirage
What can make flashes more striking?
Verne
Which author wrote The Green Ray?
Safety
Why is care needed when watching?
Time
When can the green flash appear?

Explanations: answer key for all 10 questions

Q1: What is the green flash?
Answer: A brief green glow at the edge of the setting or rising Sun
It is real, not a myth.
Q2: What causes it?
Answer: The atmosphere bending colors by different amounts
This is refraction.
Q3: Why can green be the last color seen?
Answer: It is bent more than red and yellow
The red image sets first.
Q4: Why don't we usually see a blue flash?
Answer: Blue light is scattered away
Air scatters short wavelengths.
Q5: How long does a green flash usually last?
Answer: A second or two
Blink and you miss it.
Q6: Where is it easiest to see?
Answer: Over a clear, distant horizon like the sea
Dust and haze hide it.
Q7: What can make flashes more striking?
Answer: Mirages from temperature layers
They stretch the image.
Q8: Which author wrote The Green Ray?
Answer: Jules Verne
It was published in 1882.
Q9: Why is care needed when watching?
Answer: Looking at the Sun can harm eyes
Wait until only a tiny sliver remains.
Q10: When can the green flash appear?
Answer: At sunset or sunrise
Sunsets are easier to watch.

The Sunset's Final Spark

The green flash is a real atmospheric effect: a brief green glow at the top edge of the Sun just as it sets or rises. The atmosphere bends light, a process called refraction, and it bends shorter wavelengths more. As the Sun sinks, the red and yellow images set first, leaving green for a moment.

Blue and violet are bent even more but are scattered away by the air, so we usually see green instead. A green flash typically lasts a second or two. Mirages from layers of warm and cool air can stretch the image and make flashes more striking.

The best chance is over a clear, distant horizon such as the sea, free of dust and haze. To protect your eyes, wait until only a tiny sliver of the Sun remains. Jules Verne wrote about the legend in his 1882 novel The Green Ray.

What This Quiz Teaches

Sky fans will enjoy these questions.

What the green flash is
Why green appears
Why blue is missing
Where to see it
Who wrote about it

Did You Know?

Pilots sometimes see it from aircraft.
Binoculars must never point at the Sun.
It can also appear at moonset.
Photographers capture it with zoom lenses.
Islands are popular viewing spots.