The Rainbow Is Yours Alone—Here's What That Means

There is something quietly unsettling about learning that the rainbow you stopped to photograph is not the same rainbow the person standing next to you saw. Not slightly different—an entirely different rainbow. Computed by the geometry of your eyes, your position, and the specific cluster of raindrops angled correctly toward you at that precise moment. The other person's rainbow is a different optical event, produced by different droplets, experienced from a different vantage point.

This is not a metaphor. It is the physics.

In a recent StarTalk episode, astrophysicist Neil deGrasse Tyson walked co-host Chuck Nice through the optics of rainbows—what they are, what they aren't, why you've never seen one at noon, and why the leprechaun legend is, inadvertently, physically airtight. The conversation is characteristically conversational, occasionally chaotic, and contains at least one genuinely revelatory piece of geometry that I suspect most people—science-literate or otherwise—have never fully sat with.

The Physics of Personal Experience

The basics first. When sunlight enters a raindrop, it refracts—bends—and then disperses. Dispersion is what happens when you take white light, which is composed of multiple wavelengths, and cause those wavelengths to travel at slightly different angles. Shorter wavelengths (violet, blue) bend more than longer ones (red, orange). The result is a spectrum, exiting the raindrop at different angles, sorted by color.

What this produces is not a thing hanging in the sky. It is an angle. Specifically, you see the red portion of the spectrum at about 42 degrees from the direction directly opposite the sun, and violet at about 40 degrees. Every raindrop in your field of view that happens to sit at that angular distance from your antisolar point—the point directly opposite the sun from your eyes—is contributing to your rainbow. Move two feet to the left, and the contributing droplets shift entirely.

"Someone standing next to you may not see it," Tyson explains. "They see a different rainbow. Everybody sees their own rainbow."

This is the detail that, once absorbed, makes rainbows stranger and more interesting. The rainbow is not out there, waiting to be reached. It is a relationship between your position, the sun's position, and the geometry of suspended water. It is, in a very specific sense, personal.

Why You Can't Chase It

That private geometry is also why the pot of gold at the end of the rainbow is mythologically genius. The end of the rainbow is the point where the arc meets the horizon—but because the rainbow is always centered on your antisolar point, any forward movement you make shifts the antisolar point forward too. The rainbow recedes at exactly your pace. You cannot, by construction, reach its base.

Tyson puts it plainly: you have never seen a rainbow at any angle other than directly in front of you. It is always what he calls "full frontal"—positioned at a fixed angular diameter of roughly 80 to 85 degrees, relative to your own eyeline. The rainbow from your sprinkler is the same angular size as the rainbow arcing over a valley three miles away. It just looks smaller because distance compresses apparent angular size.

The leprechaun, then, is not hiding gold somewhere geographically remote. The leprechaun is exploiting topology. "They can go to the base of a rainbow and put it in a place where you will never get it," Tyson notes, with what sounds like genuine respect for the elegance of the legend.

Newton's Unnecessary Seventh Color

One historical footnote worth pausing on: the canonical seven-color rainbow—red, orange, yellow, green, blue, indigo, violet—is a product of Isaac Newton's numerological preferences, not atmospheric physics. Newton had a documented fascination with the number seven, and found six colors insufficiently mystical. He inserted indigo between blue and violet, which gave the spectrum seven colors and also, conveniently, produced the mnemonic ROY G. BIV.

Tyson is blunt about this: indigo earns its place mainly as a vowel in a useful acronym. "If you leave out indigo, no one will fault you." Physically, the spectrum is continuous—there are no discrete bands, only a smooth gradient from red to violet. The six-color version (which is, incidentally, what appears on the original rainbow Pride flag) is at least as defensible as Newton's seven. The additional irony is that Newton was colorblind, which makes his color-classification project either poignant or farcical, depending on how charitable you're feeling.

The Second Rainbow, and the Darkness Between

Every rainbow, Tyson explains, is technically accompanied by a second one—though you rarely see it. When light enters a raindrop and reflects twice internally before exiting (rather than once), it exits at a different angle and with the color sequence reversed: red on the inside, violet on the outside, the inverse of the primary bow. This secondary rainbow sits outside the primary arc and is considerably dimmer.

The visible consequence of this is a dark band between the two arcs, known as Alexander's dark band (named after Alexander of Aphrodisias, who described it in the third century CE). The dark band appears because light is being redirected into both rainbows, leaving a relative deficit between them. It is easier to see in photographs than with the naked eye, and Tyson recommends searching for double rainbow images specifically to see this effect.

The secondary bow needs specific conditions: dim sun, good contrast, ideally an overcast sky that's not too bright. It was famously captured in a 2010 YouTube video by a man hiking in the Pacific ranges, whose overwhelmed, ecstatic reaction to seeing it became one of the internet's foundational memes. "Double rainbow all the way across the sky. What does it mean?"

The man, Paul Vasquez—known online as Yosemitebear—died in 2020. Tyson, in recounting the story, disclosed he had originally tweeted the video with the caption "This is how you behave when you don't know physics," a remark he revisited with some ambivalence. The response to Vasquez's video was, and remains, split between derision and genuine affection. The physics explanation and the emotional response aren't actually in conflict—they describe the same event from different angles, not unlike two observers looking at two different rainbows.

Geometry, Timing, and the Circle You're Missing

Two geometric facts about rainbows that don't get enough attention.

First: you have never seen a rainbow at solar noon. You have seen rainbows in the late afternoon, or occasionally in the morning, and this is not coincidence. Because the rainbow arc is centered on the antisolar point—the point directly opposite the sun—a high sun pushes the antisolar point below the horizon, which pushes the rainbow arc below the horizon with it. The sun needs to be below about 42 degrees elevation for any part of the primary bow to appear above the horizon. In practice, Tyson puts the effective threshold at around 4 in the afternoon for temperate latitudes, which also happens to coincide with afternoon thunderstorm activity in much of North America.

Second: the arc you see is not an arc. It is a circle. You're just seeing half of it, because the Earth is in the way. The rainbow is a cone of light centered on your antisolar point, and the circle is where that cone intersects a field of raindrops. Standing on the ground, the lower half of that circle is below the horizon—intercepted by terrain. But from altitude (an airplane, for instance), it is possible to see the full disk of a rainbow below you. And from a garden hose held correctly, with the sun at the right angle behind you, you can generate a complete rainbow circle with your own sprinkler.

"If the optical situation is just right, then the rainbow actually completes an entire circle," Tyson says. "You just never see the bottom half. Earth is in the way."

The circle has always been there. You've been seeing a cross-section of it your whole life.

A moonbow, for the curious: the same optics, executed with moonlight. Typically requires a full moon, ice clouds at altitude, and good dark adaptation. Colors are usually too faint to register on the human eye's color-sensitive cones, so moonbows often appear as white arcs or halos rather than full spectrum bands. Cameras, which are more sensitive than dark-adapted eyes over long exposures, tend to capture color that observers on the ground describe as white light.

The rainbow is, at its core, a geometry problem. Your specific geometry, solved fresh every time by the angle of the sun and the position of your eyes. That the same optics also produce a persistent human mythology—the unreachable end, the hidden gold, the otherworldly beauty—suggests that not knowing the physics was never really the point. Vasquez wasn't asking a scientific question when he asked what a double rainbow meant. He was asking the other kind.

Whether knowing the physics makes rainbows more or less meaningful is a question each observer will answer privately—which is, come to think of it, entirely appropriate.

By Priya Sharma, Science & Health Correspondent, Buzzrag