How Dark Energy Makes Black Holes Less Destructive ⚡ экспресс
In the McVittie black hole model embedded in an expanding universe, particles fall onto the horizon in finite time. But for extended bodies, it's trickier: with a positive cosmological constant (Λ>0), curvature at the horizon stays finite, while with Λ=0, second derivatives of curvature and some curvature tensor components grow without limit. So surviving a plunge into such a hole is only possible with dark energy. It's like jumping into a pool: if there's water, it cushions the fall; if it's empty, the impact is lethal.
Spacetime is a flexible fabric. A black hole presses it into a bottomless funnel, while the expansion of the universe stretches this fabric in all directions. Dark energy—the mysterious force accelerating the stretch—smoothes the funnel’s edges.
New calculations show: a speck of dust is guaranteed to slide into the funnel in a finite time. But the fate of a large body depends on whether dark energy is at play. Where it acts, tidal forces—the stretching stresses—at the funnel’s rim remain finite. Without it, these forces become infinite, grinding up everything that approaches.
So it turns out, the very dark energy that pushes galaxies apart makes black holes “softer.” The ideas of Karl Schwarzschild about black holes and Edwin Hubble about expansion merge into one model. A surprising fact: the black hole’s horizon, usually the point of no return, ceases to be a lethal trap in an expanding universe.
🎯 The supermassive black hole Sagittarius A* at the center of the Milky Way holds onto a gas cloud, despite cosmic expansion—its gravity is stronger than the cosmic stretching.
🎬 In “Interstellar,” astronauts survive inside a black hole; perhaps dark energy in their universe acted as an invisible guardian.