You can’t make a black hole in a lab, garage, or anywhere on Earth with current or foreseeable technology. But nature makes them all the time, and understanding how reveals some of the most extreme physics in the universe. Black holes form when matter or energy is compressed into a small enough space that gravity becomes inescapable. The ways that actually happens range from dying stars to colliding remnants to conditions in the first fraction of a second after the Big Bang.
The Basic Recipe: Density Beyond a Threshold
Every black hole comes down to one requirement: pack enough mass or energy into a small enough region that nothing, not even light, can escape. General relativity sets a hard boundary for this. If any object is compressed within a radius defined by its mass (called the Schwarzschild radius), a black hole forms. For Earth, that radius would be about 9 millimeters. For the Sun, roughly 3 kilometers. The challenge isn’t having enough mass. It’s compressing it enough.
Stellar Collapse: How Nature Does It
The most common black holes form when massive stars die. A star spends its life in a tug of war between the outward push of nuclear fusion and the inward pull of its own gravity. When a star at least 20 to 25 times the mass of the Sun exhausts its fuel, that balance breaks. The core collapses in seconds.
What happens next depends on how much mass remains in the core after the explosion. Neutron stars, the ultra-dense remnants of slightly smaller collapses, max out somewhere between 1.4 and 3 solar masses. Above that ceiling, no known force can resist gravity. The core keeps collapsing past the point of no return, and a stellar-mass black hole is born. These typically range from about 5 to several dozen times the mass of the Sun.
Merging Black Holes Together
Once black holes exist, they can grow by merging with each other. Gravitational wave detectors have directly observed this. The first confirmed detection, in 2015, captured two black holes spiraling together to create one 62 times the mass of the Sun. More recently, a 2023 event detected at LIGO involved two black holes of roughly 100 and 140 solar masses merging into a single black hole about 225 times the Sun’s mass, the most massive merger observed to date. The “missing” mass in these collisions gets radiated away as gravitational waves, ripples in spacetime itself.
Primordial Black Holes From the Big Bang
Stars aren’t the only path. In the first second after the Big Bang, the universe was so hot and dense that black holes could have formed without any star at all. During this period, small regions with density fluctuations roughly 30 to 50 percent above average could overcome the pressure resisting collapse and form what physicists call primordial black holes.
The mass of these objects depended on when they formed. A primordial black hole forming around one second after the Big Bang could have been as massive as 100,000 Suns. One forming earlier would be smaller, potentially down to microscopic scales. These remain theoretical, as none have been directly detected, but they’re a leading candidate for explaining some or all of the universe’s dark matter.
The smallest primordial black holes wouldn’t have survived to the present day. Black holes radiate energy through a process called Hawking radiation, and smaller ones radiate faster. The temperature of this radiation scales inversely with mass, so a tiny black hole is extraordinarily hot and loses mass quickly. Any primordial black hole lighter than about 500 million metric tons would have fully evaporated by now, roughly 13.8 billion years after forming. A stellar-mass black hole, by contrast, would take incomprehensibly longer than the current age of the universe to evaporate.
Could a Particle Accelerator Make One?
This was a real concern people raised when the Large Hadron Collider (LHC) at CERN began operating. The short answer: no. According to general relativity, the energies at the LHC are nowhere near sufficient. Each proton collision at the LHC involves about as much energy as a mosquito in flight. Astronomical black holes require concentrations of energy trillions upon trillions of times greater.
Some speculative theories involving extra dimensions of space suggested micro black holes might form at lower energies than expected. CERN addressed this directly. Even if such black holes could form, theory predicts they would decay almost instantly through Hawking radiation. But the stronger argument is observational: cosmic rays from space routinely produce collisions far more energetic than anything the LHC achieves. Over billions of years, nature has generated as many collisions as about a million LHC experiments’ worth on Earth alone. The universe as a whole conducts more than 10 million million LHC-equivalent experiments every second. Earth, the Sun, neutron stars, and white dwarfs are all still here. If these collisions could produce dangerous black holes, the evidence would be the absence of these objects, which obviously isn’t the case.
Could You Make One From Pure Light?
Einstein’s general relativity allows for it in principle. Energy and mass are interchangeable, so a sufficiently concentrated beam of light could theoretically warp spacetime enough to form a black hole. This hypothetical object has a name: a kugelblitz.
It’s a beautiful idea, and it’s almost certainly impossible. Theoretical physicist Eduardo Martín-Martínez and colleagues at the University of Waterloo calculated what would actually happen if you tried. When electromagnetic energy is concentrated to extreme levels, quantum effects kick in. Pairs of particles and antiparticles (electrons and positrons) spontaneously form and escape the region, carrying energy away. This bleeds off energy faster than you can concentrate it, creating a ceiling that falls far short of black hole formation.
The numbers are staggering. Forming a kugelblitz in a lab would require light intensities more than 10^50 times the most powerful laser pulses humanity has ever produced. That’s a 1 followed by 50 zeroes. Even nature can’t do it. The brightest quasars, the luminous cores of active galaxies, are vastly too dim. “No known source in the current universe would be able to produce it, neither artificial or natural,” Martín-Martínez says.
Supermassive Black Holes: Still a Mystery
The black holes at the centers of galaxies, millions to billions of times the Sun’s mass, present a different puzzle. They clearly exist (we’ve even photographed the shadows of two of them), but how they got so large remains an open question. They may have grown from smaller stellar black holes that merged and accumulated gas over billions of years. Or they may have formed from the direct collapse of enormous gas clouds in the early universe, skipping the star stage entirely. Some could even trace back to unusually large primordial black holes that served as seeds.
What’s clear is that making a black hole requires conditions far beyond anything achievable with human technology: the crushing gravity of a dying star, the extreme density of the newborn universe, or energy concentrations that dwarf anything in the observable cosmos today. Nature makes black holes routinely. We can only watch.