10 Facts About Black Holes

Science fiction writers love black holes and have picked up on the idea that they could be responsible for wormholes. They imagine that space travellers can pass through these to reach other parts of the universe or even different universes. Reality is very different as you will see from these ten facts about black holes.

1. The concept of a black hole is not new.

A black hole is not a new concept.

The Cambridge astronomer and geologist John Michell appears to have been the first to consider the possibility of black holes in 1783. He called them ‘dark stars’ and based his idea on Newton’s corpuscular theory of light which assumed light to be made of particles.

2. Black holes were predicted by the Theory of Relativity.

Karl Schwarzchild

Within a year of publication of Einstein’s theory of relativity, Karl Schwarzchild found a solution to the theory that predicted strange behaviour at what is called the Schwarzchild radius. This radius defines what is now known as the event horizon.

3. Black holes produce gravity wells in the space-time continuum.

Illustration of a gravity well in the space-time continuum.

The gravity well of a black hole is so deep that light can’t escape, which is why black holes are black!

4. A black hole consists of a singularity surrounded by an event horizon.

Features of a black hole.

When a massive star collapses to form a black hole it disappears from the universe. The event horizon is an impenetrable ‘wall’ that not even light can cross.

5. As you approach the event horizon of a black hole, you would sense that time slows down.

When you reach the event horizon, time would stand still for you … but please read fact 6 before you try!

6. As you approach the event horizon you would be ripped apart by the gravity.

The gravitational forces are incredibly strong around a black hole. Your feet would be attracted more strongly than your head. The gravitational difference between the extremities of your body would literally rip you apart well before you reached the black hole.

7. A black hole without an event horizon is called a ‘naked singularity’.

Wormhole created by a naked singularity.

The theory of relativity predicts that a naked singularity could create wormholes in space. These could provide shortcuts through space and time. Anyone attempting to use a wormhole would be subjected to the same gravitational forces as they would feel whilst approaching a black hole.

8. Black holes can be detected by gravitational lensing.

Gravitational lensing by a black hole.

The gravitational field is so intense at a black hole that it can bend and magnify distant galaxies so even though the black hole is invisible, its effects on other objects can be seen.

9. Space scientists believe that there is a super-massive black hole at the centre of most spiral galaxies, including our own.

Sagittarius A is the location of a massive black hole at the centre of our galaxy.

In our Galaxy, the powerful source of radio waves known as ‘Sagittarius A’ puzzled space scientists for many years. It is know believed that it is the location of a supermassive black hole.

10. Black holes ‘evaporate’ over time.

Black holes evaporate over time - Hawking radiation.

In the 1970s, work by professor Stephen Hawking showed that black holes lose mass by emitting a form of radiation. This radiation is known as ‘Hawking radiation‘.

Taught science for 16 years at a secondary school in the East Midlands.