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.

If the James Webb telescope was 10 times more powerful, could we see the beginning of time? - Sam H., age 12, Prosper, Texas

The James Webb Space Telescope, or JWST for short, is one of the most advanced telescopes ever built. Planning for JWST began over 25 years ago, and construction efforts spanned over a decade. It was launched into space on Dec. 25, 2021, and within a month arrived at its final destination: 930,000 miles away from Earth. Its location in space allows it a relatively unobstructed view of the universe.

The telescope design was a global effort, led by NASA, and intended to push the boundaries of astronomical observation with revolutionary engineering. Its mirror is massive – about 21 feet (6.5 meters) in diameter. That’s nearly three times the size of the Hubble Space Telescope, which launched in 1990 and is still working today.

It’s a telescope’s mirror that allows it to collect light. JWST’s is so big that it can “see” the faintest and farthest galaxies and stars in the universe. Its state-of-the-art instruments can reveal information about the composition, temperature and motion of these distant cosmic objects.

As an astrophysicist, I’m continually looking back in time to see what stars, galaxies and supermassive black holes looked like when their light began its journey toward Earth, and I’m using that information to better understand their growth and evolution. For me, and for thousands of space scientists, the James Webb Space Telescope is a window to that unknown universe.

Just how far back can JWST peer into the cosmos and into the past? About 13.5 billion years.

Time travel

A telescope does not show stars, galaxies and exoplanets as they are right now. Instead, astronomers are catching a glimpse of how they were in the past. It takes time for light to travel across space and reach our telescopes. In essence, that means a look into space is also a trip back in time.

This is even true for objects that are quite close to us. The light you see from the Sun left it about 8 minutes, 20 seconds earlier. That’s how long it takes for the Sun’s light to travel to Earth.

You can easily do the math on this. All light – whether sunlight, a flashlight or a light bulb in your house – travels at 186,000 miles (almost 300,000 kilometers) per second. That’s just over 11 million miles (about 18 million kilometers) per minute. The Sun is about 93 million miles (150 million kilometers) from Earth. That comes out to about 8 minutes, 20 seconds.

But the farther away something is, the longer its light takes to reach us. That’s why the light we see from Proxima Centauri, the closest star to us aside from our Sun, is 4 years old; that is, it’s about 25 trillion miles (approximately 40 trillion kilometers) away from Earth, so that light takes just over four years to reach us. Or, as scientists like to say, four light years.

Most recently, JWST observed Earendel, one of the farthest stars ever detected. The light that JWST sees from Earendel is about 12.9 billion years old.

The James Webb Space Telescope is looking much farther back in time than previously possible with other telescopes, such as the Hubble Space Telescope. For example, although Hubble can see objects 60,000 times fainter than the human eye is able, the JWST can see objects almost nine times fainter than even Hubble can.

The Big Bang

But is it possible to see back to the beginning of time?

The Big Bang is a term used to define the beginning of our universe as we know it. Scientists believe it occurred about 13.8 billion years ago. It is the most widely accepted theory among physicists to explain the history of our universe.

The name is a bit misleading, however, because it suggests that some sort of explosion, like fireworks, created the universe. The Big Bang more closely represents the appearance of rapidly expanding space everywhere in the universe. The environment immediately after the Big Bang was similar to a cosmic fog that covered the universe, making it hard for light to travel beyond it. Eventually, galaxies, stars and planets started to grow.

That’s why this era in the universe is called the “cosmic dark ages.” As the universe continued to expand, the cosmic fog began to rise, and light was eventually able to travel freely through space. In fact, a few satellites have observed the light left by the Big Bang, about 380,000 years after it occurred. These telescopes were built to detect the splotchy leftover glow from the Big Bang, whose light can be tracked in the microwave band.

However, even 380,000 years after the Big Bang, there were no stars and galaxies. The universe was still a very dark place. The cosmic dark ages wouldn’t end until a few hundred million years later, when the first stars and galaxies began to form.

The James Webb Space Telescope was not designed to observe as far back as the Big Bang, but instead to see the period when the first objects in the universe began to form and emit light. Before this time period, there is little light for the James Webb Space Telescope to observe, given the conditions of the early universe and the lack of galaxies and stars.

Peering back to the time period close to the Big Bang is not simply a matter of having a larger mirror – astronomers have already done it using other satellites that observe microwave emission from very soon after the Big Bang. So, the James Webb Space Telescope observing the universe a few hundred million years after the Big Bang isn’t a limitation of the telescope. Rather, that’s actually the telescope’s mission. It’s a reflection of where in the universe we expect the first light from stars and galaxies to emerge.

By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them flourish. That includes the evolution of supermassive black holes, the life cycle of stars, and what exoplanets – worlds beyond our solar system – are made of.

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.

Adi Foord, Assistant Professor of Astronomy and Astrophysics, University of Maryland, Baltimore County

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

Kids ask the coolest questions! And on The Conversation’s Curious Kids podcast we get the brainiest people we can to answer them!

Every week, a curious kid joins host Eloise to ask the world’s top researchers their burning question, whether it’s about space, dinosaurs, trees or even why their dog is just sooooo cute.

Episode 1 of our first season lands on 21 April. Listen to a taste of what’s in store in our trailer and subscribe so you don’t miss out!

The Conversation’s Curious Kids podcast is published in partnership with FunKids, the UK’s children’s radio station.

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

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

Gemma Ware, Head of Audio, The Conversation

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 don’t numbers end? – Reyhane, age 7, Tehran, Iran

Here’s a game: Ask a friend to give you any number and you’ll return one that’s bigger. Just add “1” to whatever number they come up with and you’re sure to win.

The reason is that numbers go on forever. There is no highest number. But why? As a professor of mathematics, I can help you find an answer.

First, you need to understand what numbers are and where they come from. You learned about numbers because they enabled you to count. Early humans had similar needs – whether to count animals killed in a hunt or keep track of how many days had passed. That’s why they invented numbers.

But back then, numbers were quite limited and had a very simple form. Often, the “numbers” were just notches on a bone, going up to a couple hundred at most.

When numbers got bigger

As time went on, people’s needs grew. Herds of livestock had to be counted, goods and services traded, and measurements made for buildings and navigation. This led to the invention of larger numbers and better ways of representing them.

About 5,000 years ago, the Egyptians began using symbols for various numbers, with a final symbol for one million. Since they didn’t usually encounter bigger quantities, they also used this same final symbol to depict “many.”

The Greeks, starting with Pythagoras, were the first to study numbers for their own sake, rather than viewing them as just counting tools. As someone who’s written a book on the importance of numbers, I can’t emphasize enough how crucial this step was for humanity.

By 500 BCE, Pythagoras and his disciples had not only realized that the counting numbers – 1, 2, 3 and so on – were endless, but also that they could be used to explain cool stuff like the sounds made when you pluck a taut string.

Zero is a critical number

But there was a problem. Although the Greeks could mentally think of very large numbers, they had difficulty writing them down. This was because they did not know about the number 0.

Think of how important zero is in expressing big numbers. You can start with 1, then add more and more zeroes at the end to quickly get numbers like a million – 1,000,000, or 1 followed by six zeros – or a billion, with nine zeros, or a trillion, 12 zeros.

It was only around 1200 CE that zero, invented centuries earlier in India, came to Europe. This led to the way we write numbers today.

This brief history makes clear that numbers were developed over thousands of years. And though the Egyptians didn’t have much use for a million, we certainly do. Economists will tell you that government expenditures are commonly measured in millions of dollars.

Also, science has taken us to a point where we need even larger numbers. For instance, there are about 100 billion stars in our galaxy – or 100,000,000,000 – and the number of atoms in our universe may be as high as 1 followed by 82 zeros.

Don’t worry if you find it hard to picture such big numbers. It’s fine to just think of them as “many,” much like the Egyptians treated numbers over a million. These examples point to one reason why numbers must continue endlessly. If we had a maximum, some new use or discovery would surely make us exceed it.

Exceptions to the rule

But under certain circumstances, sometimes numbers do have a maximum because people design them that way for a practical purpose.

A good example is a clock – or clock arithmetic, where we use only the numbers 1 through 12. There is no 13 o’clock, because after 12 o’clock we just go back to 1 o’clock again. If you played the “bigger number” game with a friend in clock arithmetic, you’d lose if they chose the number 12.

Since numbers are a human invention, how do we construct them so they continue without end? Mathematicians started looking at this question starting in the early 1900s. What they came up with was based on two assumptions: that 0 is the starting number, and when you add 1 to any number you always get a new number.

These assumptions immediately give us the list of counting numbers: 0 + 1 = 1, 1 + 1 = 2, 2 + 1 = 3, and so on, a progression that continues without end.

You might wonder why these two rules are assumptions. The reason for the first one is that we don’t really know how to define the number 0. For example: Is “0” the same as “nothing,” and if so, what exactly is meant by “nothing”?

The second might seem even more strange. After all, we can easily show that adding 1 to 2 gives us the new number 3, just like adding 1 to 2002 gives us the new number 2003.

But notice that we’re saying this has to hold for any number. We can’t very well verify this for every single case, since there are going to be an endless number of cases. As humans who can perform only a limited number of steps, we have to be careful anytime we make claims about an endless process. And mathematicians, in particular, refuse to take anything for granted.

Here, then, is the answer to why numbers don’t end: It’s because of the way in which we define them.

Now, the negative numbers

How do the negative numbers -1, -2, -3 and more fit into all this? Historically, people were very suspicious about such numbers, since it’s hard to picture a “minus one” apple or orange. As late as 1796, math textbooks warned against using negatives.

The negatives were created to address a calculation issue. The positive numbers are fine when you’re adding them together. But when you get to subtraction, they can’t handle differences like 1 minus 2, or 2 minus 4. If you want to be able to subtract numbers at will, you need negative numbers too.

A simple way to create negatives is to imagine all the numbers – 0, 1, 2, 3 and the rest – drawn equally spaced on a straight line. Now imagine a mirror placed at 0. Then define -1 to be the reflection of +1 on the line, -2 to be the reflection of +2, and so on. You’ll end up with all the negative numbers this way.

As a bonus, you’ll also know that since there are just as many negatives as there are positives, the negative numbers must also go on without end!

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.

Manil Suri, Professor of Mathematics and Statistics, University of Maryland, Baltimore County

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

“How is eye colour made? And why are they different colours?” – Jane, age 12, from Pascoe Vale South

Hi Jane,

Eyes are so fascinating and I’m glad you asked this question!

When we talk about eye colour, we’re talking about the iris or coloured area around the dark dot (pupil) in the centre of the eye. Like our fingerprints, iris colours are unique to each person.

The most common eye colour is brown, then blue, and less often green or hazel. Pigment means a substance that adds colour. The amazing thing is the human body only makes brown iris pigment (melanin) but not blue, green or hazel iris pigments. So how come everyone doesn’t have brown irises?

‘What colour are your eyes?’

Iris colours can be brown, blue or green, or mixtures such as brown-yellow, greenish brown or blue-brown. The word “iris” comes from the Greek word meaning “rainbow”. In ancient Greek stories, a goddess called Iris carries messages across a rainbow bridge between Earth and the supernatural world.

Genetics – how physical traits and characteristics pass from one generation to the next – play a part in determining eye colour. In many cases, the genes that produce brown eyes are dominant, but how eye colour genes are passed on is complex. This can mean if one biological parent has brown eyes and another has blue eyes, their child is more likely to have brown eyes. But not always.

But what about all the other colours?

So what is the iris made of? Our iris is inside the eye, behind a clear layer called the cornea. It’s circular and very thin (less than half a millimetre) and shaped like a donut with a hole in the middle for our pupil. The iris contains many cells, special muscles, blood vessels and nerves, surrounded by a gel material with millions of tiny crisscrossed fibres.

Iris pigment cells – melanocytes – contain pigment particles (melanosomes). Pigment cell numbers for all iris colours are about the same. But pigment particles inside the cells are different. For example, a blue iris does not have as many pigment particles as a brown iris.

The other iris cells make the tiny fibres and gel material in the iris, and other cells help protect the iris from damage. Special iris muscles with thin stretchy fibres can bunch up or relax the iris to control our pupil size in bright or dim light.

The back of the iris has a dark brown surface because of cells filled with brown pigment. This back surface pigment helps our vision as it stops light scattering through the iris.

White or visible light contains a rainbow spectrum of colours from blue to red. As light passes through the iris, the blue light scatters much more than other colours. So blue light bounces back, and this means that if there are fewer pigment particles, we see a blue iris.

Other colours in light, especially red, scatter less and get into the iris between the tiny fibres, gel and cells. Green, hazel or brown irises have more pigment particles that soak up this light.

So the eye colours we see are a result of the scattering of some light colours more or less than others, brown pigment particles soaking up more of some colours, and the number of pigment particles a person has in their iris.

Can eye colours change?

Iris colours can seem to change if different colours are near the eye. For example, different-coloured eye makeup can “trick” us as to the iris colour we see.

People with little or no iris pigment often have very pale blue irises. These can look reddish without the iris pigment to soak up the red light from inside the eye, which then passes through the iris.

Iris colour does not always stay the same during life. Babies born with blue eyes can have brown or hazel eyes by their second birthday because more dark pigment is made in iris cells after birth.

Iris colour can also change because of rare diseases or injuries.

Some eye drops to treat eye pressure make more brown pigment in iris cells, and make eyes appear browner. Some people are born with one brown eye and one blue eye, but these stay the same with age – although we’re not sure why.

There’s still so much to discover about irises and eye colour!

Michele Madigan, Associate Professor, Optometry and Vision Science, UNSW Sydney and Clinical Associate Professor, Save Sight Institute, Clinical Ophthalmology, University of Sydney

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