You’ve seen the shot. A fighter jet, maybe an F/A-18 Super Hornet or an F-35, screaming across the ocean just above the waves. Suddenly, a ghost-white shroud of mist wraps around the tail of the plane like a giant, ethereal donut. People post these images of sonic boom events all over social media, claiming they’ve captured the exact moment the sound barrier "breaks."
It’s a lie. Well, sort of.
The thing is, those stunning visual displays aren't actually the sonic boom itself. Sound is invisible. What you’re looking at is a complex interaction of pressure, temperature, and humidity known as a vapor cone—or, if you want to sound like a NASA engineer, a Prandtl-Glauert singularity. If you want to understand what's really going on when a pilot pushes the throttle forward, you have to look past the "cool" factor and into the physics of compressed air.
Why images of sonic boom don't show what you think they do
When an aircraft flies, it pushes the air out of the way. This creates waves of pressure. At subsonic speeds, these waves move out ahead of the plane at the speed of sound. Think of it like a motorboat creating a wake. But once that jet hits Mach 1—roughly 761 mph at sea level—the plane is moving faster than the pressure waves it’s creating. The waves get "bunched up" and compressed into a single shock wave.
That's the boom.
The white cone you see in many images of sonic boom captures is actually water vapor condensing. As the jet moves at high transonic speeds (usually between Mach 0.8 and Mach 1.2), the air pressure drops sharply behind certain parts of the airframe. When pressure drops, temperature drops. If the air is humid enough, the water in the air reaches its dew point and turns into a cloud. It happens in a heartbeat. Then, as the pressure returns to normal, the cloud vanishes.
You can actually see these cones at subsonic speeds. If the humidity is high enough, a jet maneuvering hard at 600 mph can trigger a vapor puff. So, while the photo looks like the "moment of impact" with the sound barrier, it’s really just a localized weather event caused by a very fast piece of titanium.
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The shock waves you can actually see
Wait, so can we ever see the actual shock wave? Yes. But it doesn't look like a fluffy white cloud. To see the actual pressure change, you need something called Schlieren photography.
NASA has been perfected this over decades. They use a technique called AirBOS (Air-to-Air Background Oriented Schlieren). Essentially, they fly one plane above another and use the edge of the sun or a mottled desert background to track how light bends as it passes through air of different densities. In these specific images of sonic boom research, you see thin, dark, jagged lines radiating away from the nose, the cockpit canopy, and the tail. Those are the real shock waves. Those lines represent the physical "wall" of air that hits your eardrums as a double-thud when the plane passes over.
The N-Wave: Why your ears hear two bangs
If you've ever stood on a flight line or at an airshow when a pilot gets "cleared for supersonic," you know it’s not just one sound. It’s a crack-crack.
This is the N-wave.
The first "peak" of the N-shaped pressure graph comes from the nose of the aircraft. This is a sudden, violent increase in pressure. The pressure then drops linearly toward the tail, eventually dipping below the normal atmospheric pressure (the "suction" phase). Then, the tail of the jet passes, and the pressure snaps back to normal. This second snap is the second boom.
In many popular images of sonic boom vapor cones, you’ll notice the cone often starts near the middle or rear of the jet. That’s because that specific area is where the air is expanding and cooling most rapidly.
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It’s not a one-time event
One of the biggest myths fueled by photography is that a sonic boom is a "pop" that happens only at the moment the pilot crosses Mach 1. People think of it like a balloon bursting.
Wrong.
The sonic boom is a continuous "carpet" of sound. As long as the plane is flying supersonic, it is dragging that cone of shock waves behind it like a heavy cape. If an F-22 flies from Los Angeles to New York at Mach 2, everyone along that entire flight path would hear the boom as the plane passes over their specific location. It doesn't "break" and then stop. It’s a constant state of atmospheric violence.
Challenges for the future: The quiet supersonic era
The reason we don't see (or hear) many images of sonic boom events over land is because of the FAA's ban on civilian supersonic flight over the United States, which has been in place since 1973. The Concorde was too loud. It rattled windows and terrified pets.
But things are changing.
NASA’s X-59 Quesst (Quiet SuperSonic Technology) is currently testing a new airframe design. The goal is to change the shape of those shock waves we see in Schlieren photography. Instead of the waves bunching up into a sharp N-wave "crack," the X-59 is designed to spread the waves out. The result? A "thump" about as loud as a car door closing.
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- Long, pointed nose: This prevents the nose-shocks from merging.
- Top-mounted engine intake: This keeps the loudest shock waves from pointing toward the ground.
- Smooth underbody: No protrusions to create extra pressure spikes.
When we eventually see the first images of sonic boom tests from the X-59, we won't see the massive vapor cones of the past. We will see a much more controlled interaction with the atmosphere.
Practical ways to capture or identify these images
If you’re a photographer or an aviation enthusiast trying to find or take these shots, you need to know what to look for. Not every cloud near a plane is a sonic event.
First, look at the edges. A true vapor cone—often called a "shock egg"—is perfectly symmetrical with the aircraft's axis. If you see wispy "smoke" coming off the wingtips during a turn, that’s just a wingtip vortex. It’s cool, but it’s not transonic.
Second, check the environment. You are almost never going to see a massive vapor cone in the desert. You need high humidity. That’s why the most famous images of sonic boom are taken by Navy photographers on aircraft carriers. The salt-heavy, moisture-laden air over the ocean is the perfect canvas for these pressure changes.
Third, understand the "Mach tuck." At these speeds, the center of pressure moves backward. Pilots have to fight the plane’s desire to dive. If you see a photo where the elevators at the back of the plane are angled sharply, the pilot is working hard to stay level while flirting with the sound barrier.
Actionable Next Steps
To truly understand the visual science of high-speed flight, you should move beyond the static photos and look at the raw data.
- Search for NASA's Schlieren imagery: Look specifically for the "AirBOS" project. These images show the actual pressure lines, not just the water vapor. It’s much more revealing of the physics at play.
- Monitor the X-59 Quesst progress: Follow the NASA Armstrong Flight Research Center updates. They are currently leading the charge in "shaping" the boom to make it quiet enough for overland travel.
- Learn to read METAR reports: If you’re heading to an airshow, check the "dew point" spread. If the temperature and dew point are within a few degrees of each other, the air is saturated. That is your best chance to see a vapor cone even if the jet stays subsonic.
- Distinguish between "vortices" and "cones": Next time you see a photo of a jet, look for the "shock" line. A cone wraps around the body; vortices trail from the tips. Being able to tell the difference makes you a much more informed observer of the tech.
The physics of air is a wild thing. It acts like a fluid until it acts like a wall. Images of sonic boom captures are a glimpse into that transition—the moment air stops being something we breathe and starts being something we can shatter.