Does space stop – or does it drag on? | Kiowa County Press

It can prompt your mind to think about what really exists. Stijn Dijkstra / EyeEm via Getty Images

Jack Singal, University of Richmond

Curious Kids is a series for children of all ages. If you have a question you would like an expert to answer, send it to [email protected]

What is beyond outer space? – Siah, 11, Fremont, CA

Right above you is the sky – or as scientists would say, the atmosphere. It stretches approximately 20 miles (32 kilometers) above the Earth. A mixture of molecules floats in the atmosphere – tiny pieces of air so small that you absorb billions of them every time you breathe.

Above the atmosphere is space. It is called that because it has a lot less molecules, with a lot of empty space between them.

Have you ever wondered what it would be like to travel to outer space – then keep going? What would you find? Scientists like me are able to explain a lot of what you would see. But there are some things we don’t know yet, like space goes on forever.

Planets, stars and galaxies

At the start of your space trip, you might recognize some of the sights. Earth is one of a group of planets that all orbit the Sun – with a few orbiting asteroids and comets mixed in as well.

A diagram of the solar system, showing the sun and its planets in orbit.
A familiar neighborhood. Mark Garlick / Science Photo Library via Getty Images

You may know that the Sun is actually just an average star and that it looks bigger and brighter than other stars just because it is closer. To reach the next closest star, you will have to travel thousands of billions of miles of space. If you could climb aboard the fastest space probe ever designed by NASA, it would still take you thousands of years to get there.

If stars are like houses, then galaxies are like cities full of houses. Scientists estimate that there are 100 billion stars in the Earth’s galaxy. If you could zoom out, well beyond Earth’s galaxy, those 100 billion stars would blend together – as the lights of city buildings do when viewed from an airplane.

Recently, astronomers have learned that many, if not most, stars have their own orbiting planets. Some are even like Earth, so it’s possible that they are home to other beings who are also wondering what’s out there.

An image showing the details of a galaxy, but visually implying that there are many more.
One galaxy among many other galaxies. Michael Miller / Stocktrek Images via Getty Images

You will have to travel millions of billions of additional kilometers in space just to reach another galaxy. Most of this space is almost completely empty, with just a few parasitic molecules and tiny, mysterious invisible particles that scientists call “dark matter.”

Using large telescopes, astronomers see millions of galaxies there – and they keep moving, in all directions.

If you could look long enough, over millions of years, it would appear that new space is gradually being added between all the galaxies. You can visualize this by imagining tiny dots on a deflated balloon and then thinking about detonating it. The dots would continue to recede, just like the galaxies.

Is there an end?

If you could keep going out as far as you wanted, would you keep passing galaxies forever? Are there an infinite number of galaxies in all directions? Or does it all end up? And if it ends, what does it end with?

These are questions to which scientists do not yet have definitive answers. Many believe that it is likely that you will continue to pass galaxies in all directions, forever. In this case, the universe would be infinite, endless.

Some scientists believe it is possible that the universe will eventually fold in on itself – so if you could just keep going out, you will someday come back to where you started, the other way around.

One way to think about this is to imagine a globe and imagine that you are a creature that can only move on the surface. If you start walking in any direction, east for example, and just keep going, you will eventually come back to where you started. If this were the case for the universe, it would mean that it is not infinitely large – although it is still larger than you might imagine.

Either way, you will never be able to reach the end of the universe or of space. Scientists now consider it unlikely that the universe will have an end – a region where galaxies stop or where there would be some sort of barrier marking the end of space.

But no one knows for sure. The answer to this question will have to be found by a future scientist.

Hello, curious children! Have a question you would like an expert to answer? Ask an adult to send your question to [email protected] Please tell us your name, age and city where you live.

And since curiosity has no age – adults, also tell us what you are wondering. We will not be able to answer all the questions, but we will do our best.

This article has been updated to correct the distances to the nearest star and galaxy.

The conversation

Jack Singal, Associate Professor of Physics, University of Richmond

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

About Florence M. Sorensen

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