As scientists call it, the sky- or the atmosphere – is directly above you. It reaches a height of around 20 miles (32 kilometers) above the Earth. A combination of molecules floats throughout the atmosphere — tiny pieces of air so minuscule that you take in billions of them every time you breathe. Have you ever thought about what it would be like to go to and then return from outer space? What would you discover? Scientists like can explain a lot about what you observe. But there are certain things we don’t know yet, such as whether space continues indefinitely.
You may recognize some of the sights at the start of your journey through space. The Earth is a group of planets that all circle the Sun, along with certain asteroids and comets. You may be aware that the Sun is only an ordinary star that seems more significant and brighter than the other stars due to its proximity.
To get to the next closest star, you’d have to travel billions of miles across space. Galaxies are like towns full of homes, if stars are like houses. Scientists believe that the Earth’s galaxy has 100 billion stars. Those 100 billion stars would mix if you could zoom out far beyond Earth’s galaxy, much as the lights of city skyscrapers do when seen from an aircraft.
To reach another galaxy, you would have to travel across millions of trillions of miles of space. The vast majority of that space is almost empty, with just a few errant molecules and small mystery unseen particles known as “dark matter” by physicists.
Astronomers use large telescopes to observe millions of galaxies out there – and they keep going in every direction. If you could see for a long enough period, spanning millions of years, it would appear that additional space is progressively being added between all the galaxies. Scientists do not yet have definitive answers to these issues.
Many people believe you’d keep passing galaxies in every direction indefinitely. The cosmos would be endless in such a situation, with no beginning and no end. Consider seeing a globe and imagining yourself as a creature that can only move on the surface. If you start walking in any direction, say east, and keep going, you’ll ultimately end up back where you started. If this were true for the universe, it would imply that it is not indefinitely large – albeit it is still more significant than you can fathom.
You could never reach the end of the universe or space in either circumstance. Scientists today believe that the cosmos does not have an end – a point where galaxies come to a halt or where some form of barrier marks the end of space. Nobody knows for sure. A future scientist will have to find out how to answer this question.