The Times Australia
The Times World News

.

how do black holes pull in light?

  • Written by Sara Webb, Postdoctoral Research Fellow, Centre for Astrophysics and Supercomputing, Swinburne University of Technology

How can a black hole pull in light when light isn’t a physical thing? – Will, age 8, Victoria

how do black holes pull in light?

What an excellent question, Will! I too wondered about this when I started to learn the wonders of physics.

To answer this, we must first explain three things: 1) what is light, 2) what is gravity, and 3) what is a black hole?

1) What is light?

Light is just a type of energy, travelling through space. There are many different types of light we can’t physically see, but can detect and even use. For example, ultraviolet light that comes from our Sun is why you have to wear sunscreen – so the light doesn’t hurt your skin.

A chart showing the entire electromagnetic spectrum from radio waves to gamma rays
The electromagnetic spectrum includes all types of electromagnetic radiation – that is, energy. The bit in the middle with a rainbow and a sun symbol on it marks visible light. Shutterstock

Read more: Curious Kids: can our brains sense electromagnetic waves?[1]

It’s important for us to remember that just because light doesn’t have mass, it still is very much a physical thing in our universe, following physical laws.

The neat thing is, no matter what type of light, it all follows the same physical laws in the universe. One rule is that light always wants to travel in a straight line through space.

This is where we now need to break down gravity, and what space is made of.

2) What is gravity?

Gravity is the force that keeps us safe here on Earth. It also keeps Earth circling around (orbiting) our Sun. But what causes gravity?

Many scientists in history pondered this question, and came up with all sorts of theories. But when Albert Einstein presented his theory on general relativity in 1915, we started to really understand exactly what gravity was, and how it affects our universe.

Einstein had mathematically worked out that we exist in something called “spacetime”. You can picture this as the fabric of our universe. Like a fabric, it can bend and stretch. I like to picture space like a trampoline. When you put something heavy (like a bowling ball) in the middle of a trampoline, the fabric underneath it bends and sinks down.

A cartoon image of a purple trampoline with a bowling ball in the middle A trampoline being bent by a bowling ball is not unlike spacetime being bent by something heavy. This is how gravity works. Sara Webb, CC BY[2]

Now imagine a universe-sized trampoline, and we place our Sun on it. The dip in that trampoline represents the gravity of the Sun. And we can do this with every object that has mass.

When spacetime is bent by that mass, the lines that would normally be straight become slightly curved – you can see that in the picture below. This is most extreme around the really massive objects we call black holes.

A chart showing a grid lightly stretched by a yellow ball, and very stretched by a black ball Spacetime bending around the Sun compared to a black hole. Note the lines that once would have been straight are bent and curved under the gravity. Sara Webb/Wikimedia Commons, CC BY[3][4]

Read more: Curious Kids: How are planets created?[5]

3) What is a black hole?

Black holes are, in my opinion, one of the coolest things we’ve ever discovered in the universe. Black holes are regions of space so dense, nothing can escape.

They are usually formed when very large stars get too heavy and collapse (implode) on themselves. Astronomers think all the mass in the black hole is actually squished into a single point in the middle.

Black holes get a bad reputation for eating “anything that is near them”, which is just not true. Black holes do have a distance from their centre, which we mark as the point of no return. This is called the event horizon.

But farther away from this point, light and matter can circle around a black hole for a very long time.

So how can a black hole pull in light?

Now we’ve broken down those three key things, we can answer the great question asked by Will: how can a black hole pull in light?

When light is travelling near a black hole, it is still trying to travel in a straight line. As it gets closer to the black hole where spacetime is bent, the light will follow those bends.

When light gets very close to the black hole, it can be trapped circling around and around it. That’s because the fabric of spacetime is bent to the extreme. As you’ll remember, light is indeed a physical thing and is affected by spacetime.

Possibly my favourite part about this fact is it doesn’t just apply to black holes.

Anything with enough mass can make light bend around it, even our Sun. This was how scientists first confirmed Einstein’s theory of gravity was likely correct in 1919[6].

Something really heavy, like a whole group of galaxies clumped together, can bend space so much, it works like a magnifying glass and shows zoomed-in pictures[7] of the stars behind it.

Read more: Curious Kids: what are gravitational waves?[8]

References

  1. ^ Curious Kids: can our brains sense electromagnetic waves? (theconversation.com)
  2. ^ CC BY (creativecommons.org)
  3. ^ Sara Webb/Wikimedia Commons (commons.wikimedia.org)
  4. ^ CC BY (creativecommons.org)
  5. ^ Curious Kids: How are planets created? (theconversation.com)
  6. ^ was likely correct in 1919 (www.discovermagazine.com)
  7. ^ shows zoomed-in pictures (esahubble.org)
  8. ^ Curious Kids: what are gravitational waves? (theconversation.com)

Read more https://theconversation.com/curious-kids-how-do-black-holes-pull-in-light-208848

Times Magazine

Building a Strong Online Presence with Katoomba Web Design

Katoomba web design is more than just creating a website that looks good—it’s about building an online presence that reflects your brand, engages your audience, and drives results. For local businesses in the Blue Mountains, a well-designed website a...

September Sunset Polo

International Polo Tour To Bridge Historic Sport, Life-Changing Philanthropy, and Breath-Taking Beauty On Saturday, September 6th, history will be made as the International Polo Tour (IPT), a sports leader headquartered here in South Florida...

5 Ways Microsoft Fabric Simplifies Your Data Analytics Workflow

In today's data-driven world, businesses are constantly seeking ways to streamline their data analytics processes. The sheer volume and complexity of data can be overwhelming, often leading to bottlenecks and inefficiencies. Enter the innovative da...

7 Questions to Ask Before You Sign IT Support Companies in Sydney

Choosing an IT partner can feel like buying an insurance policy you hope you never need. The right choice keeps your team productive, your data safe, and your budget predictable. The wrong choice shows up as slow tickets, surprise bills, and risky sh...

Choosing the Right Legal Aid Lawyer in Sutherland Shire: Key Considerations

Legal aid services play an essential role in ensuring access to justice for all. For people in the Sutherland Shire who may not have the financial means to pay for private legal assistance, legal aid ensures that everyone has access to representa...

Watercolor vs. Oil vs. Digital: Which Medium Fits Your Pet's Personality?

When it comes to immortalizing your pet’s unique personality in art, choosing the right medium is essential. Each artistic medium, whether watercolor, oil, or digital, has distinct qualities that can bring out the spirit of your furry friend in dif...

The Times Features

How much money do you need to be happy? Here’s what the research says

Over the next decade, Elon Musk could become the world’s first trillionaire[1]. The Tesla board recently proposed a US$1 trillion (A$1.5 trillion) compensation plan, if Musk ca...

NSW has a new fashion sector strategy – but a sustainable industry needs a federally legislated response

The New South Wales government recently announced the launch of the NSW Fashion Sector Strategy, 2025–28[1]. The strategy, developed in partnership with the Australian Fashion ...

From Garden to Gift: Why Roses Make the Perfect Present

Think back to the last time you gave or received flowers. Chances are, roses were part of the bunch, or maybe they were the whole bunch.   Roses tend to leave an impression. Even ...

Do I have insomnia? 5 reasons why you might not

Even a single night of sleep trouble can feel distressing and lonely. You toss and turn, stare at the ceiling, and wonder how you’ll cope tomorrow. No wonder many people star...

Wedding Photography Trends You Need to Know (Before You Regret Your Album)

Your wedding album should be a timeless keepsake, not something you cringe at years later. Trends may come and go, but choosing the right wedding photography approach ensures your ...

Can you say no to your doctor using an AI scribe?

Doctors’ offices were once private. But increasingly, artificial intelligence (AI) scribes (also known as digital scribes) are listening in. These tools can record and trans...