Night Sky Gaze
An artist's depiction of a Black Hole

Cosmic Objects: What Is a Black Hole, Really?

The boogeyman of the cosmos is the undetectable, inescapable death of all information: the black hole. Nearly everyone has heard of the naturally occurring phenomenon, but not everyone is familiar with the details of these mind-bending voids in space.

So, what is a black hole, really? Let’s take a closer look–but not too close; that’s how you fall into an event horizon.

What Is a Black Hole?

A black hole is a region of space and time that has become so dense that escape velocity from its gravitational pull would require you to move faster than the speed of light. Since it’s impossible to move faster than the speed at which light moves, black holes are, by definition, inescapable.

The outer boundary around a black hole from which nothing can escape—not light, not particles, nothing—is called an “event horizon.” This is the point beyond which information is completely destroyed. Since no force could ever recover matter or energy from within a black hole, the event horizon acts as a curtain between the interior of a black hole and the rest of the observable universe.

How Do They Form?

When sufficiently massive stars collapse, they can become black holes. This is due to their incredible mass. As they become more and more dense, they eventually form what is known as a gravitational singularity. This object, theoretically, has infinite density.

To an outside observer, as a black hole forms, the matter falling into the singularity would appear to stop and hover just beyond the event horizon indefinitely. This process is known as gravitational time dilation.

Eventually, the appearance of this matter would also become more and more red, due to gravitational red shift, before slowly fading from view. From the point of view of an indestructible viewer, this process would occur normally over a finite span of time.

Problems and Questions

The existence of black holes raises a number of questions regarding the laws of physics and the nature of the cosmos. Black holes appear to invalidate a number of universal constants and seem to act under their own set of rules. Questions about the resolution of such problems continue to be hotly debated in the physics community.

For now, what is known is that black holes are inescapable, they might last forever if they are of sufficient mass, and they could represent the death of meaningful information. In spite of this, their very existence is theoretical; scientists can only detect them by their impact on surrounding objects. This makes them some of the scariest natural phenomenon ever described.

Cameron Norris