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On May 22, 2026, the Pentagon released a second batch of previously classified photos and videos showing what appear to be unexplained flying objects. These file dumps were the culmination of a process that was set in motion back in July 2023, when a group of government whistleblowers testified before Congress that the U.S. government was secretly in possession of extraterrestrial spacecraft and suspected alien body parts.
That congressional hearing marked the beginning of a cultural shift in which UFO reports are increasingly treated as a matter for serious discussion, both within the government and the scientific community.
The Pentagon released over 200 previously classified UFO files in May 2026. Image: Department of Defense
But is this newfound legitimacy deserved? As an aerospace scientist who studies aircraft and spacecraft design, I approach this question using math, physics and the principles of engineering. To assess the plausibility of alien visitors, it’s necessary to understand the obstacles that an extraterrestrial vessel would need to overcome to reach Earth.
The tyranny of distance
There is no evidence of intelligent alien life in our solar system. So any extraterrestrial visitors would likely have to come from another star system within our Milky Way galaxy.
Proxima Centauri, the star closest to our Sun, is located 4.25 light-years (about 25 trillion miles or 40 trillion kilometers) away.
For perspective, if Earth were the size of a pea, the distance to Proxima Centauri would roughly equal the distance between New York and Sydney, Australia.
Even the stars closest to Earth are incredibly far away.
Since only a fraction of stars are thought to host intelligent life, the nearest alien civilization – if one exists – is surely much farther away than Proxima.
A need for speed
Given the scale of interstellar distances, it’s inevitable that any alien voyage to Earth would span many years and possibly several centuries. But as the time spent in transit increases, so does the risk of catastrophic accidents or system malfunctions that could jeopardize the mission. So it’s important to avoid an overly lengthy journey by traveling as fast as possible.
No object can reach or exceed the speed of light (roughly 186,000 miles or 300,000 kilometers per second). But well before approaching that threshold, engineering constraints begin to assert themselves. Limited fuel availability and the potential for structural damage will restrict the spacecraft’s peak velocity.
There is no universally accepted upper limit on interstellar flight speeds, but studies tend to converge around 19,000 miles per second (30,000 km/s) – 10% of the speed of light – as a realistic cruise velocity. At this speed, a journey of 10 light-years will take approximately 100 years to complete.
Fueling the dream
Finding a way to accelerate the ship to its target cruise speed is the central challenge facing any would-be alien explorers.
Interstellar space is unforgivingly vast, but the emptiness has some advantages. The lack of atmosphere means there is no aerodynamic drag. So when the ship reaches its cruise speed, it can shut down its propulsion system and coast toward the final destination. Unfortunately, the lack of atmosphere also means there is nothing to slow the ship down prior to arrival. So ideally, the propulsion system would be used for both acceleration at the start of the trip and deceleration at the end.
One of the more exotic propulsion strategies employs high-powered laser beams to push the ship through space. The beam is projected from a stationary array near the travelers’ home planet and directed toward a thin reflective sail attached to the ship. The beam’s photons exert radiation pressure on the sail, propelling the ship forward.
This approach has a major advantage in that it requires no onboard fuel. But the amount of energy and infrastructure needed to operate the laser would be staggering. Also, beamed propulsion provides no mechanism for deceleration. At best, this method could be deployed as part of a hybrid strategy that uses a separate system for deceleration.
A more practical approach is to use rocket propulsion. Rockets generate propulsive force, also known as thrust, by expelling high-velocity exhaust in a rearward stream. By reversing the direction of the exhaust, rockets can also be used to slow the ship down.
Their main disadvantage is that rockets must carry their own fuel in addition to carrying the passengers, the habitat and other life-sustaining systems. The extra load necessitates even more fuel. In other words, you need fuel to transport your fuel. The result is a costly snowball effect that can cause the total fuel requirement to balloon to absurd proportions.
Rocket propulsion can be divided into three broad categories.
Chemical propulsion uses chemical reactions – typically combustion – to extract energy from the bonds between atoms. All human space missions thus far have used chemical propulsion. The problem with this method is that it accesses only a tiny fraction of the energy contained within the fuel.
Antimatter propulsion is theoretically the most efficient option. When antimatter comes into contact with ordinary matter, the two undergo mutual annihilation and 100% of their combined mass is converted into energy. This makes it possible to achieve the same cruise velocity – one-tenth the speed of light – with fuel accounting for less than a quarter of the ship’s total mass. This is science fiction-level fuel efficiency, which makes antimatter an attractive option for interstellar propulsion.
NASA has been working to develop nuclear propulsion. This artist’s impression shows what a nuclear-powered rocket could look like. Image: Public Domain, John Frassanito & Associates/Wikipedia
These numbers assume that our extraterrestrial visitors have figured out how to efficiently convert the energy released by their reactor – whether nuclear fusion or antimatter – into thrust.
Just as importantly, they must be able to create optimized fuel tank structures that are ultra lightweight yet highly secure. Designing the structure of the ship, from the fuel tanks to the hull, would be one of the biggest engineering challenges of the entire mission.
Interstellar space contains a sparse smattering of hydrogen atoms and microscopic grains of cosmic dust. At 19,000 miles per second (30,000 km/s), dust particles would smash into the ship’s hull with the energy of a .22-caliber bullet. The bombardment of hydrogen atoms would produce a violent cascade of radiation that could erode even the most resilient engineering materials.
Surviving the onslaught would require no less than a flying fortress with complex magnetic shielding. This would increase the total mass of the ship, which further drives up the demand for fuel.
This example is just one of the hundreds of delicate design trade-offs that would plague any interstellar vessel. Each individual design requirement acts as a filter, reducing the number of feasible solutions.
Finding a single system that simultaneously satisfies all the requirements is analogous to shopping for a car online. With each new filter you apply – four-wheel drive, black exterior, less than 10,000 miles on the odometer – the number of available options dwindles.
When design requirements are in tension with one another – for example, requiring a structure that is lightweight but also supremely durable – the number of feasible solutions can drop to zero.
No single law of physics prohibits an interstellar voyage to Earth. But the combined effects of hundreds of extreme, often conflicting engineering requirements may render it physically infeasible.
It’s also possible that alien civilizations have discovered novel technologies that outperform anything currently known to humans. But like the examples discussed here, any such technology will inevitably encounter its own engineering hurdles.
The trillion-dollar question
Ultimately, engineering challenges are just some of the many barriers to interstellar travel. Any prospective alien visitors must also have sufficient cognitive ability, technological maturity, physical resources, collective desire and proximity to Earth.
That said, if the stars were to align and an alien vessel made it to Earth intact, it would trigger a torrent of burning questions: Where are they from? What do they want? What are they made of?
But the question that would go furthest in shedding light on the deeper mysteries of the universe is, “How on Earth did they get here?”
What are those orange balls on some power lines? – Maggie, age 8, West Chester, Pennsylvania
Have you ever looked up while driving on a highway and spotted those big orange balls hanging on power lines? They look a bit like giant toy beads strung along the electric wires.
What in the world are those overgrown basketballs doing up there?
Those big orange balls don’t help with electricity flow or improve the efficiency of the power lines, but they do have a very important job. Officially called aviation marker balls or spherical markers, they’re there to help pilots see power lines so airplanes and helicopters don’t crash into them. They’re like bright warning signs in the sky, protecting pilots, passengers and people on the ground below.
Big round warning signs in the sky
Power lines can be very hard to see from an airplane or helicopter, especially when pilots are flying low. Thin metal wires can visually blend into the background of nature.
The orange balls help the lines stand out. You can think of them as being like reflective tape on a bike – just a little something simple that helps people notice a danger before it’s too late.
Orange isn’t a random choice. This vibrant color is very visible to the human eye and especially stands out against the more muted colors of nature – blue sky, green trees or gray clouds. Sometimes the balls are red or white, or even striped, but orange is the most common because it works well in most lighting conditions.
Aviation safety rules in many countries explain which colors should be used so pilots can quickly recognize hazards. Organizations like the U.S. Federal Aviation Administration publish guidelines you can check out about marking obstacles near flight paths.
These balls may look like slightly oversized ping-pong balls from your perspective on the ground. But most are actually much bigger, about the size of a large beach ball, roughly 2 to 3 feet (0.6 to 1 meter) across. Each one can weigh 10 to 25 pounds (4.5 to 11 kilograms), about as heavy as a large backpack full of books.
They’re usually made from strong plastic or fiberglass, similar to materials used in boats or playground equipment. That way, they can survive years of sun, rain, snow, wind – and even the occasional bird landing on them.
Even though they sit on wires that carry huge amounts of electricity, the balls themselves are not energized. They’re made of insulating materials, so electricity does not flow through them.
The wires are strung between sturdy metal towers or wooden poles that are very tall to keep dangerous high-voltage electric wires high up in the sky, far away from people on the ground. This design makes it safe to walk, play and drive underneath them. Some transmission towers, especially for very high-voltage lines, can be as tall as a 15-story building.
If you look closely at big transmission lines, you’ll often see three thick wires, sometimes with an additional thinner one on top that’s called a shield wire. Because the shield wire sits higher, lightning is more likely to hit it first, protecting the other wires from a strong blast of electricity that can damage equipment or cause power outages. The shield wire is connected to the ground, so a lightning strike’s electricity can flow safely down the tower and into the earth.
The three main wires work together to carry electricity in a steady rhythm. By sharing the job among three wires instead of one, the system can move more energy with less waste, making it more efficient.
Installing the aviation marker balls is a job for specially trained crews, often working from helicopters. The power line usually stays turned on while the work is being done, so safety rules and careful planning are critical. The ball comes in two halves that clamp around the wire and bolt together tightly.
Once installed, these balls can last 10 to 15 years, depending on weather and conditions. They don’t need much maintenance, but utilities inspect them from time to time to make sure they haven’t cracked or faded too much.
Not every transmission line needs the markers. Usually only places where aircraft are more likely to fly low – such as near rivers, valleys, airports or helicopter routes – will use these brightly colored balls. Most neighborhood power lines are too low to need markers.
Next time you spot those bright orange dots in the sky, you’ll know: They’re not electrical equipment, and their color isn’t random. They’re simple, clever tools helping keep our busy world a little safer.
Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.
And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.
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