Could our universe have been born from a black hole?

Scientists Explore the Intriguing Idea that Our Universe Might Have Originated from a Black Hole.

TL;DR

In the 20th century, cosmology evolved dramatically, leading to bold ideas like our Universe possibly emerging from a black hole. Einstein’s theory of General Relativity revealed that the Universe is not static, and expanding space was confirmed by observation. Coincidentally, the size of a black hole with the mass of the observable Universe is nearly identical to our Universe’s size. Recent theories suggest black holes might give birth to “baby universes,” but there’s no definitive evidence yet. These ideas remain speculative but offer fascinating possibilities for the origin of our Universe.

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In the 20th century, our understanding of the Universe underwent a major transformation. Just over a century ago, we believed that the Milky Way galaxy contained everything visible in the sky. The Universe was thought to be static, unchanging, and possibly eternal, governed by Newton’s law of universal gravitation.

That perspective changed rapidly. Einstein’s General Relativity replaced Newton’s gravitation, revealing the relationship between matter, energy, and spacetime. His equations showed that the Universe couldn’t be static, but had to evolve over time, a concept confirmed by the discovery of the expanding Universe. His theory also predicted black holes, which were later detected and even directly imaged.

This gave rise to a bold idea: perhaps our Universe was born from a black hole. Here’s why this idea is so intriguing.

Both inside and outside the event horizon of a Schwarzschild black hole, space flows like either a moving walkway or a waterfall, depending on how you want to visualize it. At the event horizon, even if you ran (or swam) at the speed of light, there would be no overcoming the flow of spacetime, which drags you into the singularity at the center. Outside the event horizon, though, other forces (like electromagnetism) can frequently overcome the pull of gravity, causing even infalling matter to escape.
Andrew Hamilton / JILA / University of Colorado

A black hole’s defining characteristic is the event horizon, a boundary that presents a different reality for objects outside versus inside. Outside the event horizon, objects feel the black hole’s gravitational pull but can still escape if they move fast enough or in the right direction. However, once an object crosses the event horizon, it is inevitably drawn into the black hole’s singularity, contributing to the black hole’s mass. From an external viewpoint, the black hole appears to form, gain mass, and grow over time.

One of the most important contributions of Roger Penrose to black hole physics is the demonstration … [+]
Nobel Media, The Nobel Committee for Physics; annotations by E. Siegel

But what does this have to do with the Universe? If we combine all the known matter and energy in the observable Universe and compress it into a single point, what happens? According to Einstein’s theory of gravity, this would result in a black hole. Remarkably, the Schwarzschild radius of a black hole with the mass of the observable Universe is almost exactly the same as the size of the visible Universe. This coincidence raises the possibility that our Universe could be the interior of a black hole, but the story doesn’t end there.

In the 1960s, a discovery revolutionized our view of the Universe: low-energy radiation was detected coming uniformly from all directions in the sky. This radiation, now known as the cosmic microwave background, was found to have a temperature of 2.725 K, just above absolute zero, and a near-perfect blackbody spectrum. This evidence supported the idea that the Universe was expanding and cooling, having been hotter and denser in the past. The further back we go, the more the hot Big Bang model approaches a singularity, similar to the conditions found inside black holes, where densities and temperatures become extreme, and the laws of physics break down.

When examining the equations governing black holes, something remarkable occurs. Outside the event horizon, as you move away from the black hole, your distance (r) goes from the Schwarzschild radius (R) to infinity (∞). Inside the event horizon, the distance decreases from the Schwarzschild radius to zero (0) as you approach the singularity. The key point is that the properties of space outside the event horizon are mathematically identical to those inside the event horizon, but with r and R reversed.

In recent decades, two major discoveries have shaken cosmology. The first is cosmic inflation: the idea that the Universe underwent a rapid, exponential expansion before the Big Bang. The second is dark energy: a mysterious force causing the Universe’s expansion to accelerate. Some speculate that black holes could be linked to these phenomena. Could cosmic inflation represent the birth of our Universe from an ultramassive black hole? Could dark energy be connected to black holes?

There’s also the idea that each black hole in our Universe might spawn a “baby Universe” inside it. While these speculations are compelling, none have led to definitive conclusions. Theoretical models must meet three criteria:

  • Reproduce all of the successes of the current Big Bang model.
  • Explain phenomena that the current theory can’t.
  • Make new predictions that can be tested.

One notable attempt is Roger Penrose’s Conformal Cyclic Cosmology (CCC), which predicts the existence of “Hawking points” — regions of low temperature variance in the cosmic microwave background. However, these features haven’t been robustly observed, keeping the idea of black holes birthing universes in the realm of speculation.

Nearby, the stars and galaxies we see look very much like our own. But as we look farther away, we see the Universe as it was in the distant past: less structured, hotter, younger, and less evolved. Measuring the Universe at different epochs helps us understand all the different forms of matter and energy present within it, including normal matter, dark matter, neutrinos, photons, black holes, and gravitational waves.
NASA, ESA, AND A. FEILD (STSCI)

The idea that black holes and the birth of universes are linked is appealing from both physical and mathematical perspectives. It’s possible that our Universe originated from a black hole in a previous Universe or that black holes in our Universe are creating new ones. However, we still lack the crucial evidence to confirm this. Until that evidence is found, these ideas remain speculative hypotheses. While we don’t yet know if our Universe was birthed from a black hole, it remains a fascinating possibility that cannot be ruled out.

When a black hole forms, the mass and energy collapses down to a singularity. Similarly, continuing to extrapolate the expanding Universe backwards in time leads to a singularity when temperatures, densities and energies are high enough. Could these two phenomena be connected?
NASA / CXC / M. WEISS

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