In January 2023, a new comet was discovered. Comets are found regularly, but astronomers quickly realised this one, called C/2023 A3 (Tsuchinshan-ATLAS), had the potential to be quite bright.

Some hyperbolic reports have suggested it might be the “comet of the century”, but any astronomer will tell you the brightness of comets is notoriously hard to predict. As I explained last year, we’d have to wait until it arrived to be sure how bright it would become.

Now, the time has come. Comet C/2023 A3 is currently visible with the naked eye in the morning sky in Australia and Aotearoa New Zealand, with its best yet to come in the next few weeks. And it does look promising. It’s unlikely to be the comet of the decade (never mind the comet of the century), but it will almost certainly become the best comet of the year.

So where, and when, should you look to get your best views of this celestial visitor?

A show in the morning, before sunrise

At the moment, comet C/2023 A3 (Tsuchinshan-ATLAS) is a morning object, rising around an hour and a half before sunrise. It is visible to the naked eye, but not yet spectacular. However, with binoculars you can easily see the comet’s dusty tail pointing away from the Sun.

The comet will remain at about the same altitude in the morning sky until around September 30. It will then get closer to the horizon on each consecutive morning until it’s lost in the glare of the approaching dawn by October 6 or 7.

If you want to spot the comet in the morning sky, look east. The sliders below will help you orient yourself and choose the best time to look, depending on your latitude.

During this period, the comet should slowly brighten. It reaches its closest approach to the Sun (perihelion) on September 27, when it will be 58 million kilometres from our star.

As it swings around the Sun, it will continue to approach Earth, and so should continue to brighten. The best show in the morning sky will likely be during the last couple of days of September and the first few days in October, before the comet is lost to view.

A potential daylight comet

Thanks to pure good fortune, comet C/2023 A3 (Tsuchinshan-ATLAS) will then pass almost directly between Earth and the Sun on October 9 and 10.

This could cause a spectacular brightening of the comet, thanks to “forward scattering” caused by its dust. Imagine looking towards a bright light source through a cloud of dust grains. The grains nearest to the light source will scatter light from the source back towards you.

As the comet swings between Earth and the Sun, it will be perfectly placed for this forward scattering process to occur. If the comet is particularly dusty, this could cause its apparent brightness to increase by up to 100 times.

If it does, there’s a small chance the comet could briefly become visible in the daylight sky on October 9 and 10.

However, it will be very close to the Sun in the sky, and incredibly hard to spot. Only the most experienced observers may be able to detect the comet at this time, and it requires a special technique. Do not try to stare at the Sun to see it.

The best show could be after October 12

After swinging between Earth and the Sun, the comet will appear in the evening sky. It will rapidly climb in the western sky, and should be a bright, naked-eye object for a few days from October 12. The sliders below will give you a sense of where to look.

For the first few days of this period, the comet will still benefit from the forward scattering of sunlight, but this will decrease as it moves away.

What about the tail?

The positioning of the comet, Earth and the Sun in the Solar System means the comet’s tail will be streaming outwards, past our planet. This means it could grow to prodigious lengths in the night sky.

The bulk of that tail will likely be too dim to see easily with the naked eye, but it could be a fantastic spectacle for photographers. Expect to see a wealth of comet images flooding the internet around the middle of October.

As the days pass and the comet climbs higher, it will fade quite rapidly. It will likely become too faint to see with the naked eye, even for seasoned and experienced observers, before the end of October.

At that point, the show will be over. Comet C/2023 A3 (Tsuchinshan-ATLAS) will continue to flee the inner Solar System, moving into the icy depths of space, never to return.

How reliable are the predictions?

At the moment, the comet is already bright enough to consider it the “comet of the year”, outshining comet 12P/Pons-Brooks from earlier this year.

But remember the classic saying – comets are like cats. They have tails and will often surprise us. For now, comet C/2023 A3 is behaving itself. It’s brightening predictably, and putting on a good show.

But comets that approach this closely to the Sun often fragment. This is impossible to predict, and far from guaranteed. If the comet did break up, it could become even more spectacular because of all the dust and gas it would release.

The opposite could still happen, too. The comet could fail to brighten as much as we expect, although that seems unlikely at this stage.

Whatever happens, we’re in for a fascinating few weeks of comet watching. Hopefully, a real spectacle awaits us.

Jonti Horner, Professor (Astrophysics), University of Southern Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Have you ever wondered how chameleons change colour? And can they do this while they’re asleep? What about if they are able to dream? Does their dream flash across their bodies in reds, turquoises and greens?

Join curious ten-year-old Ikechukwu from Lagos, Nigeria, as he takes all his questions to an expert!

Featuring Russell Ligon, a recent postdoctoral researcher at Cornell University in the US.

The Conversation’s Curious Kids podcast is published in partnership with FunKids, the UK’s children’s radio station. It’s hosted and produced by Eloise. The executive producer is Gemma Ware.

Email your question to curiouskids@theconversation.com or record it and send your question to us directly at funkidslive.com/curious.

And explore more articles from our Curious Kids series on The Conversation.

Disclosure statement:

Russell Ligon recently finished a postdoctoral research position at Cornell University. He’s received funding for his work on chameleons from the National Science Foundation, Harvard Travellers Club, American Society of Naturalists, Animal Behavior Society, American Society for Ichthyologists and Herpetologists and Arizona State University where he did his PhD.

Sound credits

Choir sound by liezen3 via freesound.org .

Eloise Stevens, Host, The Conversation's Curious Kids podcast, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What does the edge of the universe look like?

Lily, age 7, Harcourt

What a great question! In fact, this is one of those questions humans will continue to ask until the end of time. That’s because we don’t actually know for sure.

But we can try and imagine what the edge of the universe might be, if there is one.

Looking back in time

Before we begin, we do need to go back in time. Our night sky has looked the same for all of human history. It’s been so reliable, humans from all around the world came up with patterns they saw in the stars as a way to navigate and explore.

To our eyes, the sky looks endless. With the invention of telescopes about 400 years ago, humans were able to see farther – more than just our eyes ever could. They continued to discover new things in the sky. They found more stars, and then eventually started to notice that there were a lot of strange-looking cosmic clouds.

Astronomers gave them the name “nebula” from the Latin word for “mist” or “cloud”.

It was less than 100 years ago that we first confirmed these cosmic clouds or nebulas were actually galaxies. They are just like Milky Way, the galaxy our own planet is in, but very far away.

What is amazing is that in every direction we look in the universe, we see more and more galaxies. In this James Webb Space Telescope image, which is looking at a part of the sky no bigger than a grain of sand, you can see thousands of galaxies.

It’s hard to imagine there is an edge where all of this stops.

The edge of the universe

However, there is technically an edge to our universe. We call it our “observable” universe.

This is because we don’t actually know if our universe is infinite – meaning it continues forever and ever.

Unfortunately, we might never know because of one pesky thing: the speed of light.

We can only ever see light that’s had enough time to travel to us. Light travels at exactly 299,792,458 metres per second. Even at those speeds, it still takes a long time to cross our universe. Scientists estimate the size of the universe is at least 96 billion light years across, and likely even bigger.

You can learn a little more about that and our universe as a whole in this video below.

What would we see if there was an edge?

If we were to travel to the very, very edge of the universe we think exists, what would there actually be?

Many other scientists and I theorise that there would just be … more universe!

As I said, there is a theory that our universe doesn’t actually have an edge, and might continue on indefinitely.

But there are other theories, too. If our universe does have an edge, and you cross it, you might just end up in a completely different universe altogether. (That is best saved for science fiction for now.)

Even though there isn’t a straightforward answer to your question, it is precisely questions like these that help us continue to explore and discover the universe, and allow us to understand our place within it. You’re thinking like a true scientist.

Sara Webb, Lecturer, Centre for Astrophysics and Supercomputing, Swinburne University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The days are getting longer and in Australia, the switch to daylight saving time is almost upon us (for about 70% of the population, anyway).

But why do we have longer days in summer and shorter days in winter?

It’s all about the tilt

Earth goes around the Sun in an almost circular orbit. But not everything is lined up perfectly. Earth’s axis is tilted by 23.44 degrees relative to its orbit around the Sun.

Imagine Earth’s orbit as a flat frisbee with the Sun in the middle and Earth as a ball on a stick going around the edge.

If Earth’s axis wasn’t tilted (if its tilt was zero degrees) the stick would be exactly perpendicular to the frisbee. If you grab that perpendicular stick and tip it 23.44 degrees sideways, that’s what Earth’s tilt looks like now.

As Earth orbits the Sun, the tilt of the stick does not rotate relative to the Sun. If you were in outer space looking at the Sun and you watched from the exact same position for a whole year, you would see Earth go around the Sun while the stick stayed tilted the same direction.

In other words, if the top of the stick was pointing to the right when you started watching Earth go around the Sun, it would stay pointing to the right the whole way around.

This tilt gives us longer days in summer and shorter days in winter. Let’s set up the scenario so the Northern Hemisphere is the top of the planet and the Southern Hemisphere is the bottom of the planet.

When Earth is on one side of the Sun, the top of the stick is pointed towards the Sun. This is summer in the Northern Hemisphere and winter in the Southern Hemisphere. Six months later, when Earth is on the other side of the Sun, the bottom of the stick is pointed towards the Sun – and the seasons are reversed.

Solstices and equinoxes

Those two points, when the top of the stick is pointing directly towards the Sun or directly away from the Sun, are the solstices. They are the longest and shortest days of the year, depending on your hemisphere.

The shortest day of 2024 in Australia was June 21. Looking forward to sunnier times, the longest day of the year in 2024 will be December 21.

In between the summer and winter solstice, we have the equinoxes – when days and nights are almost exactly the same length. Those are the days when the stick through Earth is “side-on” to the Sun. The equinox is also the day when the Sun passes directly over Earth’s equator. In 2024 this happened on March 20 at 2:06pm AEDT and September 22 at 10:43pm AEST.

That means that since September 22, days have been getting longer than nights in the Southern Hemisphere.

What does daylight saving do?

Earth’s tilt means the Sun both rises earlier and sets later as we head towards summer. When the clocks (in some states) switch to daylight saving time, people in these states all get one hour less of sleep. However, the total length of the day doesn’t change just because we changed our clocks.

For me, daylight saving means I need an extra cup of coffee in the morning for about a week before I adjust to the daylight saving-lag (like jet lag, but without the fun of travel).

What it really gives us is more daylight in the evening, instead of more daylight in the morning. If you’re already a morning person, this isn’t the way to go. But if you prefer to have a long dinner in the summer sun it’s ideal.

Has it always been this way?

Earth’s axis hasn’t always been tilted at 23.44 degrees. It cycles from a minimum 22.1 degree tilt to a maximum 24.5 degree tilt and back again once every approximately 41,000 years.

Earth’s axis also “precesses”, where the stick through it draws a circle once every approximately 26,000 years. You can see this in the animation below.

The length of a day on Earth hasn’t always been the same, either.

At the moment, the length of a day is nearly exactly 24 hours. But it’s shifting all the time by tiny amounts. This is tracked very closely by a system of telescopes and satellites. These systems measure “Earth orientation parameters” that describe Earth’s exact orientation compared to the position of stars in the sky.

These are important to astronomers because the exact location of our telescopes is important for creating accurate maps of the sky. On top of all of this, the gravitational drag from the Moon causes days to become longer by around 2.3 milliseconds every 100 years. A few billion years ago, Earth’s day was a lot shorter – only 19 hours long.

Even though some of us are losing an hour of sleep this weekend, at least we get to enjoy 2.3 milliseconds longer every day than our great – and great-great – grandparents did.

Laura Nicole Driessen, Postdoctoral researcher in radio astronomy, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Seven-year-old Julia in London thinks that rainbows and the Northern Lights are magical. But if a scientist tells her how they work, will she still believe they are? Join us to find out on The Conversation’s Curious Kids podcast!

Featuring Partha Chowdhury, professor of physics at UMass Lowell in the US.

This is the last episode in the first season of The Conversation’s Curious Kids podcast, published in partnership with FunKids, the UK’s children’s radio station. It’s hosted and produced by Eloise. The executive producer is Gemma Ware.

Email your question to curiouskids@theconversation.com or record it and send your question to us directly at funkidslive.com/curious.

And explore more articles from our Curious Kids series on The Conversation.

Disclosure statement:

Partha Chowdhury does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Eloise Stevens, Host, The Conversation's Curious Kids podcast, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How high could I jump on the moon? – Miles, aged five, London, UK.

If you were lucky enough to go to the moon, you’d be able to jump six times as high there as you can here on Earth. Try it: jump up and imagine you’re on the moon. Six times further up you’d go (better not look down).

How does that work? Well, it’s all to do with gravity, that mysterious force that pulls you down when you jump up, and makes sure the people living on the other side of the Earth don’t just fall off.

Gravity doesn’t stick you to the ground like glue, or pull you back to earth like an elastic band. What you’re actually feeling is space changing shape. You can do an experiment to show how it works. You need a towel, an apple or an orange, a pea and four friends.

Get your friends to each hold a corner of the towel so that it is nice and flat. Ask your friends to close their eyes. Then place the fruit in the middle. Your friends will know when you did so, because they felt the towel pull at their hands. This is because the fruit has got “mass” – it’s made of stuff.

Now place the pea somewhere on the towel and let go. You’ll see it rolls towards the fruit in the middle – not because the fruit pulled at it, but because the fruit changed the shape of the towel, and the pea noticed that.

Curious Kids is a series by The Conversation, which gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our very best.

Anything with mass changes space in this way. You do, too – just a tiny amount. Perhaps it’s not surprising, then, that the moon orbits around the Earth, since our planet is so much bigger.

But wait – it’s not just size that matters, mass does too. The moon is just over a quarter of the size of the Earth. But if it had the same mass, then the moon’s gravity would be about 14 times stronger than Earth’s and you’d hardly be able to jump at all.

If that same mass was squeezed down to the size of a village, it’d become a black hole, and we’d all be sucked into it.

But the moon is made of similar stuff as the outer bits of the Earth, which are less dense and float on top of the heavier core in the middle, like oil floats on top of water.

This means the moon actually has 80 times less mass than Earth. So, the gravity on the moon is (80 divided by 14) six times as weak. And that’s what makes it so easy (and fun) to hop around on – just like the Apollo astronauts used to do.

US National Archives/Giphy

But beware: when you come down after your record-breaking jump, the landing will feel just as hard as it does on Earth.

Up, up and away?

Although you can jump very high on the moon, you’ll be happy to know that there’s no need to worry about jumping all the way off into space. In fact, you’d need to be going very fast – more than 2 kilometres per second – to escape from the moon’s surface.

The fastest jumping human being ever was Javier Sotomayor, who reached a speed of 7 metres per second, and a height of 2.45 metres (he was nearly 2 metres tall already).

If Sotomayor had jumped on the moon, he would have been able to jump over a house - but he wouldn’t have gone any faster. The speed at which you jump does not depend on the strength of gravity – it depends on your muscle strength (and skill). So he wouldn’t have been able to jump off the moon, either.

What about fleas? They would be able to jump well into space, surely? Nope. They can’t even reach the same speed as humans when they jump. That’s why a flea on Earth couldn’t jump 2.45 metres high. They do jump many more times their own height, of course – but then, they are really tiny.

The highest jumping animal in the world is the white-tailed jackrabbit. They can jump over six metres in the air, and would certainly get a speeding ticket if caught jumping in town. On the moon, a white-tailed jackrabbit would easily jump over a ten-storey flat – but still not shoot off into space.

People would love to go back to the moon. If they get serious about it, it will happen. Wouldn’t you love to be one of them?

Children can have their own questions answered by experts – just send them in to Curious Kids, along with the child’s first name, age and town or city. You can:

• email curiouskids@theconversation.com
• tweet us @ConversationUK with #curiouskids
• DM us on Instagram @theconversationdotcom

Here are some more Curious Kids articles, written by academic experts:

• Why do some animals have two different coloured eyes? – George, aged ten, Hethersett, UK.

• How long has gravity existed? - Aine, aged 13, Edinburgh, UK.

• Does the sky protect the Earth and if yes, then how? – Saskia, aged eight, Estonia.

Jacco van Loon, Astrophysicist and Director of Keele Observatory, Keele University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

Is it possible to make a phone through which we can smell, like we can hear and see? – Muneeba K., age 10, Pakistan

Imagine this: You pick up your phone for a video call with a friend. Not only can you see their face and hear their voice, but you can also smell the cookies they just baked. It sounds like something out of a science fiction movie, but could it actually happen?

I’m a computer scientist who studies how machines sense the world.

What phones do now

When you listen to music or talk to someone on your phone, you can hear the sound through the built-in speakers. These speakers convert digital signals into physical vibrations using a tiny component called a diaphragm. Your ears sense those vibrations as sound waves.

Your phone also has a screen that displays images and videos. The screen uses tiny dots known as pixels that consist of three primary colors: red, green and blue. By mixing these colors in different ways, your phone can show you everything from beautiful beach scenes to cute puppies.

Smelling with phones

Now how about the sense of smell? Smells are created by tiny particles called molecules that float through the air and reach your nose. Your nose then sends signals to your brain, which identifies the smell.

So, could your phone send these smell molecules to you? Scientists are working on it. Think about how your phone screen works. It doesn’t have every color in the world stored inside it. Instead, it uses just three colors to create millions of different hues and shades.

Now imagine something similar for smells. Scientists are developing digital scent technology that uses a small number of different cartridges, each containing a specific scent. Just like how pixels mix three colors to create images, these scent cartridges could mix to create different smells.

Just like images on your phone are made of digital codes that represent combinations of pixels, smells produced by a future phone could be created using digital codes. Each smell could have a specific recipe made up of different amounts of the ingredients in the cartridges.

When you receive a digital scent code, your phone could mix tiny amounts of the different scents from the cartridges to create the desired smell. This mix would then be released through a small vent on the phone, allowing you to smell it. With just a few cartridges, your phone could potentially create a huge variety of smells, much like how red, green and blue pixels can create countless colors.

Researchers and companies are already working on digital odor makers like this.

The challenges to making smell phones

Creating a phone that can produce smells involves several challenges. One is designing a system that can produce thousands of different smells using only a few cartridges. Another is how to control how strong a scent should be and how long a phone should emit it. And phones will also need to sense odors near them and convert those to digital codes so your friends’ phones can send smells to you.

The cartridges should also be easy to refill, and the chemicals in them be safe to breathe. These hurdles make it a tricky but exciting area of research.

An odiferous future

Even though we’re not there yet, scientists and engineers are working hard to make smell phones a reality. Maybe one day you’ll be able to not only see and hear your friend’s birthday party over the phone, but also smell the candles they blew out!

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Jian Liu, Assistant Professor of Electrical Engineering and Computer Science, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

Why can’t it always be summer? – Amanda, age 5, Chile

With its long days just itching to be spent by water doing nothing, summer really can be an enchanting season. As Jenny Han wrote in the young adult novel “The Summer I Turned Pretty”: “Everything good, everything magical happens between the months of June and August.”

But all good things must come to an end, and summer cannot last forever. There’s both a simple reason and a more complicated one. The simple reason is that it can’t always be summer because the Earth is tilted. The more complicated answer requires some geometry.

I’m a professor of geography and the environment who has studied seasonal changes on the landscape. Here’s what seasons have to do with our planet’s position as it moves through the solar system.

Closeness to the Sun doesn’t explain seasons

First, you need to know that the Earth is a sphere – technically, an oblate spheroid. That means Earth has a round shape a little wider than it is tall.

Every year, Earth travels in its orbit to make one revolution around the Sun. The Earth’s orbit is an ellipse, which is more like an oval than a circle. So there are times when Earth is closer to the Sun and times when it’s farther away.

A lot of people assume this distance is why we have seasons. But these people would be wrong. In the United States, the Earth is 3 million miles closer to the Sun during winter than in the summer.

Spinning like a top

Now picture an imaginary line across Earth, right in the middle, at 0° latitude. This line is called the equator. If you drew it on a globe, the equator would pass through countries including Brazil, Kenya, Indonesia and Ecuador.

Everything north of the equator, including the United States, is considered the Northern Hemisphere, and everything south of the equator is the Southern Hemisphere.

Now think of the Earth’s axis as another imaginary line that runs vertically through the middle of the Earth, going from the North Pole to the South Pole.

As it orbits, or revolves, around the Sun, the Earth also rotates. That means it spins on its axis, like a top. The Earth takes one full year to revolve around the Sun and takes 24 hours, or one day, to do one full rotation on its axis.

This axis is why we have day and night; during the day, we’re facing the Sun, and at night, we’re facing away.

But the Earth’s axis does not go directly up and down. Instead, its axis is always tilted at 23.5 degrees in the exact same direction, toward the North Star.

The Earth’s axis is tilted due to a giant object – perhaps an ancient planet – smashing into it billions of years ago. And it’s this tilt that causes seasons.

It’s all about the tilt

So that means in June, the Northern Hemisphere is tilted toward the Sun. That tilt means more sunlight, more solar energy, longer days – all the things that make summer, well, summer.

At the same time, the Southern Hemisphere is tilted away from the Sun. So countries such as Australia, Chile and Argentina are experiencing winter then.

To say it another way: As the Earth moves around the Sun throughout the year, the parts of the Earth getting the most sunlight are always changing.

Fast-forward to December, and Earth is on the exact opposite side of its orbit as where it was in June. It’s the Southern Hemisphere’s turn to be tilted toward the Sun, which means its summer happens in December, January and February.

If Earth were not tilted at all, there would be no seasons. If it were tilted more than it is, there would be even more extreme seasons and drastic swings in temperature. Summers would be hotter and winters would be colder.

Defining summer

Talk to a meteorologist, climate scientist or author Jenny Han, and they’ll tell you that for those of us in the Northern Hemisphere, summer is June, July and August, the warmest months of the year.

But there’s another way to define summer. Talk to astronomers, and they’ll tell you the first day of summer is the summer solstice – the day of the year with the longest amount of daylight and shortest amount of darkness.

The summer solstice occurs every year sometime between June 20 and June 22. And every day after, until the winter solstice in December, the Northern Hemisphere receives a little less daylight.

Summer officially ends on the autumnal equinox, the fall day when everywhere on Earth has an equal amount of daylight and night. The autumnal equinox happens every year on either September 22 or 23.

But whether you view summer like Jenny Han or like an astronomer, one thing is certain: Either way, summer must come to an end. But the season and the magic it brings with it will be back before you know it.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Stephanie Spera, Assistant Professor of Geography and the Environment, University of Richmond

This article is republished from The Conversation under a Creative Commons license. Read the original article.