Black Holes (C1)

black holes

Answer the following questions with a partner:

• What are black holes?

• Where do they come from?

• What happens if you fall into one?

Discussion

The average L1 user of English would certainly have some difficulty processing all of this information. How overwhelmed where you?

Did the content of the video cohere with your own answers?

What three interesting bits of information did you take away from the video?

What were some 'I didn't really get what he was saying' moments?

The video mentioned a common myth about black holes: they don't actually suck things. Did you know that? Can you think of any other myths about black holes?

Myths about black holes

1

Black holes suck everything in like cosmic vacuum cleaners.

At a distance, a black hole's gravity is the same as that of any object with the same mass. If the Sun were replaced by a black hole of exactly the same mass, Earth would keep orbiting as before. It would just get very dark and very cold.

2

Black holes are holes.

Despite the name, a black hole is not an empty gap in space. It is an object: a huge amount of matter squeezed into an extremely small space, so dense that not even light can escape its gravity.

3

All black holes are enormous.

Some are, but many are not. A black hole with ten times the mass of the Sun has an event horizon only about 60 kilometres across, roughly the size of a large city.

4

Anything that gets close is instantly ripped apart.

5

Black holes last forever.

Near a small black hole, the difference in gravity between your head and your feet would stretch you like spaghetti long before you reached the edge. Near a supermassive black hole, however, you could cross the event horizon without feeling anything unusual at that moment.

Stephen Hawking calculated that black holes slowly lose energy and should eventually evaporate. For a black hole the mass of the Sun, this would take far longer than the current age of the universe, and the effect has never been observed.

6

A black hole could swallow Earth any day now.

7

Black holes are invisible, so we can't study them.

The nearest known black hole is more than 1,500 light-years away, and it is not heading towards us.

We can't see a black hole itself, but we can see its effects: stars racing around it, gas glowing as it falls in, and ripples in space called gravitational waves when two black holes collide.

Discussion

• Which of these myths did you believe before today?

• Did any of the definitions from the warmer include one of these myths?

• Are there any that you just can't make sense of?

• Where do you think these myths come from? Films, news headlines, the name itself?

• If you overhear a conversation where someone you know mentions one of these myths, how confident do you think you'd be at explaining it?

Now let's take a look at some more images of black holes

Real picture or artist’s impression?

Most black hole pictures you see online are not photographs. They are artists' impressions or computer simulations, based on what physics predicts a black hole should look like. Some are very accurate. The black hole in the film Interstellar, for example, was created with help from a Nobel Prize-winning physicist. But they are still illustrations, not observations.

Only two real images of a black hole's surroundings exist so far. In 2019, the Event Horizon Telescope released a picture of the black hole at the centre of the galaxy M87, followed in 2022 by one of Sagittarius A*, at the centre of our own galaxy. To make them, radio telescopes around the world observed at the same time, together acting like a single telescope the size of Earth. They produced so much data that it was stored on hard drives and flown to computing centres, where algorithms reconstructed the images. Even then, the orange colour was added afterwards, because the radio waves they recorded are invisible to the human eye.

discussion

Before reading the text, did you think the pictures you saw were real photographs?

News websites often use artists’ impressions without clearly labelling them. Is this a problem? Why or why not?

Even the real images were reconstructed by computers and coloured by scientists. Are they still “real”?

Is it acceptable to make science look more exciting than it is in order to attract public interest and funding?

Who is responsible for making the difference clear: scientists, journalists, or readers themselves?

Can you think of other areas, such as advertising, history or medicine, where images are “improved” for the public? Is that any different?

Finally, let's take a look at the latest research into black holes.

Which are you most interested in?

Or, which can you vaguely understand? 😅

H · READ

Current research on black holes

1

A black hole older than its galaxy.

Using the James Webb Space Telescope, researchers studied gas orbiting the black hole of a tiny galaxy more than 13 billion light-years away. Their results suggest that the black hole, about 50 million times the mass of the Sun, existed before its host galaxy and may even have formed within the first second after the Big Bang. It accounts for roughly two thirds of the galaxy’s total mass.

2

The Milky Way’s black hole is “breathing”.

3

Wandering black holes.

Astronomers using the ALMA telescope array in Chile have found clear evidence that Sagittarius A*, the black hole at the centre of our galaxy, is blowing out a hot wind, something scientists had been looking for for more than 50 years. X-ray data from NASA’s Chandra observatory confirmed that the black hole is responsible, not nearby stars.

Supermassive black holes are normally found at the centres of galaxies. This year, however, NASA’s Swift observatory saw one tearing apart a star more than 30,000 light-years from the centre of a distant galaxy, producing a flare that briefly outshone the whole galaxy in ultraviolet light. Artificial intelligence helped make the discovery possible, and another team has found the first sleeping, inactive black hole that far from a galaxy’s core.

4

Breaking the speed limit.

There is a theoretical limit on how fast a black hole can feed. Japanese astronomers have found a black hole from about 12 billion years ago that is growing at roughly 13 times that limit. This challenges current models and may help explain how black holes grew so large so quickly in the early universe.

5

The biggest collision ever detected.

Gravitational wave detectors pick up ripples in space caused by colliding black holes. One recent merger, known as GW231123, created a black hole about 225 times the mass of the Sun, heavier than many scientists thought possible for this kind of collision.

6

From photographs to films.

After producing the first two images, the Event Horizon Telescope team is now trying to show how black holes change over time. The long-term goal of an expanded network is to produce full-colour, high-definition movies of black holes.

discussion

Which of these research projects sounds the most interesting to you? Which sounds the least interesting?

Do any of these discoveries have practical value for people on Earth, or is it purely knowledge for its own sake?

Research like this costs billions. Is it worth it? What else could that money be spent on?

If you could fund only one of these projects, which would it be, and why?