The Times Australia
The Times World News

.
The Times Real Estate

.

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

The Times Features

Itinerary to Maximize Your Two-Week Adventure in Vietnam and Cambodia

Two weeks may not seem like much, but it’s just the right time for travelers to explore the best of Vietnam and Cambodia. From the bustling streets of Hanoi to the magnificent te...

How to Protect Your Garden Trees from Wind Damage in Australia

In Australia's expansive landscape, garden trees hold noteworthy significance. They not only enhance the aesthetic appeal of our homes but also play an integral role in the local...

Brisbane Homeowners Warned: Non-Compliant Flexible Hoses Pose High Flood Risk

As a homeowner in Brisbane, when you think of the potential for flood damage to your home, you probably think of weather events. But you should know that there may be a tickin...

Argan Oil-Infused Moroccanoil Shampoo: Nourish and Revitalize Your Hair

Are you ready to transform your hair from dull and lifeless to vibrant and full of life? Look no further than the luxurious embrace of Argan Oil-Infused Moroccanoil Shampoo! In a...

Building A Strong Foundation For Any Structure

Building a home or commercial building can be very exciting. The possibilities are endless and the future is interesting. You can always change aspects of the building to meet the ...

The Role of a Family Dentist: Why Every Household Needs One

source A family dentist isn’t like your regular dentist who may specialise in a particular age group and whom you visit only when something goes wrong. A family dentist takes proa...

Times Magazine

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

How AI-Driven SEO Enhancements Can Improve Headless CMS Content Visibility

Whereas SEO (search engine optimization) is critical in the digital landscape for making connections to content, much of it is still done manually keyword research, metatags, final tweaks at publication requiring a human element that takes extensiv...

Crypto Expert John Fenga Reveals How Blockchain is Revolutionising Charity

One of the most persistent challenges in the charity sector is trust. Donors often wonder whether their contributions are being used effectively or if overhead costs consume a significant portion. Traditional fundraising methods can be opaque, with...

Navigating Parenting Arrangements in Australia: A Legal Guide for Parents

Understanding Parenting Arrangements in Australia. Child custody disputes are often one of the most emotionally charged aspects of separation or divorce. Parents naturally want what is best for their children, but the legal process of determining ...

Blocky Adventures: A Minecraft Movie Celebration for Your Wrist

The Minecraft movie is almost here—and it’s time to get excited! With the film set to hit theaters on April 4, 2025, fans have a brand-new reason to celebrate. To honor the upcoming blockbuster, watchfaces.co has released a special Minecraft-inspir...

The Ultimate Guide to Apple Watch Faces & Trending Wallpapers

In today’s digital world, personalization is everything. Your smartwatch isn’t just a timepiece—it’s an extension of your style. Thanks to innovative third-party developers, customizing your Apple Watch has reached new heights with stunning designs...

LayBy Shopping