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On This Page You Will Learn
This guide is written for beginners. It starts with the simple idea, then builds toward real-life examples so the topic becomes easier to remember and easier to use.
- How this topic fits into the bigger story of Earth, gravity, orbits and space
- Why movement, distance, time and energy matter in space
- How scientists use observations, missions and measurements to understand it
- What to read next so the space journey feels connected
ExplainItSimply learning path
How big is the universe, and where do we fit inside it?
This short guide prepares you for the main explanation. It shows the problem, the simple solution and the step-by-step path that makes the topic easier to understand.
?The problem
Space can feel too big to understand because the distances, movements and forces are far beyond everyday experience.
!The simple solution
Begin with something familiar, like day and night, the Moon, sunlight, seasons, gravity or the way objects move.
*Why it matters
When you understand The Universe — Galaxies and Space, the sky becomes less mysterious and the world around you starts to make more sense.
Real-life example: Watching the sky
You do not need a telescope to begin learning space. A sunrise, a shadow, the Moon during the day or a clear night sky can all become simple starting points.
How the idea builds up
- Start with one thing you can observe.
- Ask what is moving or changing.
- Connect the idea to Earth, the Moon, the Sun or gravity.
- Use a simple picture or comparison.
- Build toward the bigger space story step by step.
Remember this: A topic becomes easier when it is explained in order and connected to something familiar.
In Simple Terms
Did you know?A space mission is not one single event. It is planning, launch, orbit, navigation, communication, landing, and learning from data.
How big is the universe? What is a galaxy? What happened at the Big Bang? The grandest questions about our cosmos, answered simply.
What Is the Universe?
Did you know?The Sun does not switch off at night. Night happens because your part of Earth has turned away from the Sun.
The universe is everything that exists — all matter, energy, space, and time. It contains all the stars, galaxies, planets, black holes, dust, gas, and even the laws of physics themselves. As far as we know, there is nothing "outside" the universe, because the universe is, by definition, all there is.
The observable universe — the part we can see from Earth — has a diameter of about 93 billion light-years. A light-year is the distance light travels in one year: about 9.46 trillion kilometres. These numbers are so vast they are almost impossible to comprehend in everyday terms.
Scale perspective: If the Sun were shrunk to the size of a grain of sand, the nearest star (Proxima Centauri) would be about 4 kilometres away. The Milky Way would be the size of Europe. The observable universe would be about the size of the Earth itself.
Universe in Numbers
- Age: approximately 13.8 billion years
- Observable diameter: about 93 billion light-years
- Estimated galaxies: 2 trillion or more
- Stars in the Milky Way: 100–400 billion
- Estimated stars in the universe: more than grains of sand on all Earth's beaches
What Is the Big Bang?
Did you know?People in different countries see sunrise and sunset at different times because Earth is a spinning sphere.
The Big Bang is the leading scientific explanation for the origin of the universe. About 13.8 billion years ago, all the matter and energy in the universe was compressed into an incredibly hot, dense point (called a singularity). Then, in a fraction of a second, it began expanding — rapidly inflating in what we call the Big Bang.
It is important to understand that the Big Bang was not an explosion in space — it was an expansion of space itself. The universe did not burst outward from a central point. Instead, everywhere in the universe simultaneously became less dense as space stretched in all directions.
Evidence for the Big Bang includes the cosmic microwave background radiation (the faint glow left over from the early universe, detected in all directions), the observed expansion of the universe, and the abundance of hydrogen and helium in the universe.
What Is a Galaxy?
Did you know?A space mission is not one single event. It is planning, launch, orbit, navigation, communication, landing, and learning from data.
A galaxy is a massive collection of stars, gas, dust, and dark matter, all held together by gravity. Our galaxy is called the Milky Way — it contains between 100 billion and 400 billion stars. From Earth, on a dark night, you can see a faint band of light across the sky — this is the glow of billions of stars in our own galaxy, seen edge-on.
Galaxies come in different shapes:
- Spiral galaxies — flat discs with spiral arms, like the Milky Way and the Andromeda galaxy.
- Elliptical galaxies — oval or spherical, typically older and containing less gas and dust.
- Irregular galaxies — no defined shape, often the result of galactic collisions.
The Milky Way is part of a small group of galaxies called the Local Group. The Local Group is part of a larger cluster called the Virgo Supercluster, which is itself part of an even larger structure called Laniakea — a supercluster containing about 100,000 galaxies.
Black Holes
Did you know?People in different countries see sunrise and sunset at different times because Earth is a spinning sphere.
A black hole is a region of space where gravity is so strong that nothing — not even light — can escape. Black holes form when massive stars collapse under their own gravity at the end of their lives. The boundary around a black hole from which nothing can escape is called the event horizon.
Black holes come in different sizes. Stellar black holes (formed from collapsed stars) can be 5–100 times the mass of the Sun. Supermassive black holes, found at the centre of most large galaxies, can be millions or even billions of times the mass of the Sun. The Milky Way's central black hole, Sagittarius A*, is about 4 million solar masses.
In 2019, the Event Horizon Telescope produced the first direct image of a black hole — the supermassive black hole at the centre of galaxy M87, 55 million light-years from Earth.
Dark Matter and Dark Energy
Did you know?Orbit is not floating without gravity. Orbit is falling around something while moving sideways fast enough to keep missing it.
Here is one of the most remarkable facts in modern science: the ordinary matter we can see — stars, planets, gas, dust — makes up only about 5% of the universe. The rest is mysterious.
- Dark matter (27%) — an invisible form of matter that does not emit or absorb light. We know it exists because of its gravitational effect on galaxies (galaxies spin faster than they should if only visible matter were present). Its exact nature is unknown.
- Dark energy (68%) — an even more mysterious force that is causing the expansion of the universe to accelerate. It was only discovered in 1998 and remains one of physics' greatest unsolved mysteries.
Space ideas become easier when we connect them to Earth, light, gravity and motion.Go deeperHow to understand The Universe — Galaxies and Space clearly
Did you know?Orbit is not floating without gravity. Orbit is falling around something while moving sideways fast enough to keep missing it.
The Universe — Galaxies and Space is part of the bigger story of how our planet, the Moon, the Sun, gravity, space, and time work together. This page explains the idea slowly, using everyday examples, so a beginner can understand the science without needing a textbook first.
A helpful way to learn this topic is to connect it to something familiar. Instead of memorising terms first, start by asking: what is moving, what is changing, what is causing it, and why does it matter in real life? That simple question turns a difficult subject into a story you can follow.
On ExplainItSimply, the goal is not to make you sound technical. The goal is to help you understand the idea well enough to explain it to someone else. When you can explain the universe — galaxies and space using your own words and a normal example, the topic has started to make sense.
What you will learn on this page
- You will understand the basic science behind the universe — galaxies and space without needing formulas first.
- You will see how the idea connects to everyday experiences such as daylight, seasons, tides, time, navigation, and the sky above you.
- You will learn the difference between what people commonly imagine and what is actually happening in space.
- You will get simple examples that make large distances, motion, gravity, and time easier to picture.
- You will finish with a clearer sense of how Earth fits into the wider universe.
The ExplainItSimply promise for this topic
No jargon for the sake of sounding clever. No confusing shortcuts. This page explains the universe — galaxies and space with plain language, real examples, and clear connections so you can use the idea, remember it, and continue learning with confidence.
Interesting things about the universe
Did you know?A space mission is not one single event. It is planning, launch, orbit, navigation, communication, landing, and learning from data.
The universe is not just empty space with stars sprinkled inside it. It contains galaxies, gas clouds, planets, moons, black holes, dark matter, radiation, and huge distances that are difficult to imagine. Light itself takes time to travel, which means looking far into space is also looking into the past.
Some stars are being born inside clouds of gas, while others are dying in powerful explosions. Some planets may be rocky like Earth, while others are gas giants, icy worlds, or objects unlike anything in our solar system. The universe is full of questions, and each answer usually opens a bigger question.
Why this page matters
This page matters because space can feel too big to understand at first. By explaining The Universe — Galaxies and Space in simple steps, the guide helps you connect the sky, planets, motion, time and life on Earth into one understandable story. You do not need to be a scientist to follow it; you only need curiosity and a willingness to picture each idea slowly.
What you will learn about The Universe — Galaxies and Space
You will learn what The Universe — Galaxies and Space means, why it is important in the bigger space journey, and how it connects to Earth, the Moon, the Sun, planets, gravity and the wider universe. You will also see how one space idea often depends on another, because orbits, light, distance, heat, atmosphere and time all work together. By the end, the topic should feel less like a difficult science word and more like something you can explain in your own words.
Deeper Explanation
Did you know?Orbit is not floating without gravity. Orbit is falling around something while moving sideways fast enough to keep missing it.
The universe is bigger than one solar system
The universe includes all galaxies, stars, planets, space, time, matter and energy. Our solar system is only a tiny part of one galaxy called the Milky Way. That galaxy is only one of many billions, which means the universe is far larger than everyday imagination can easily hold.
Why scale matters
Learning about the universe teaches scale. It helps us understand that some light has travelled for millions or billions of years before reaching us. When we look deep into space, we are also looking back in time because light takes time to travel.
Simple learning promise
For this space guide, the promise is simple: each idea is explained in plain English, with familiar examples that help you picture gravity, motion, distance and the sky without assuming that you already know astronomy.
A Practical Example
Did you know?Orbit is not floating without gravity. Orbit is falling around something while moving sideways fast enough to keep missing it.
Imagine you are explaining The Universe — Galaxies and Space to someone who has never heard the idea before. You would not begin with technical words. You would begin with a picture, a story, or a familiar comparison. That is how this page is written: it starts from the simplest useful idea and then builds slowly so the reader does not feel lost.
A useful explanation should answer the reader’s first question, provide enough context to understand the full idea and then point naturally to the next topic. That creates a learning journey instead of a collection of disconnected facts.
Common Questions
Did you know?A space mission is not one single event. It is planning, launch, orbit, navigation, communication, landing, and learning from data.
Is this guide written for beginners?
Yes. This guide is written for readers who want to understand The Universe — Galaxies and Space without needing expert knowledge first. It uses plain English and builds the explanation step by step.
Why does the page use longer paragraphs?
Longer paragraphs allow the idea to breathe. Instead of throwing disconnected bullet points at the reader, the page explains the thinking in full sentences so the topic feels more natural and complete.
What should I read next?
Use the related reading cards below or the menu at the top of the page. The best next page is usually one from the same category, because related topics strengthen each other.
Read More on ExplainItSimply
Did you know?People in different countries see sunrise and sunset at different times because Earth is a spinning sphere.
Learning is easier when related topics connect. These guides continue the journey and help visitors spend more time exploring useful pages on the site.
Read another helpful guide
Learning works best when ideas connect. Explore another ExplainItSimply page and keep building your knowledge.
Explore Space & UniverseContinue learning in simple English
Now that you have started understanding The universe — galaxies and space, keep going. The next page will help you connect this idea to another useful topic.
OverviewEarth — Our HomeRead blogs
The universe is full of stars, galaxies and questions that begin with simple curiosity.Where you will see this in real life
This topic is easier to remember when it connects to everyday life. Here are a few familiar situations where this idea becomes visible in everyday life.
Flying
Airplanes stay in the atmosphere because of lift, engines and gravity working together.
GPS
Your phone uses satellites and timing signals to find your location.
Weather
Satellites help track clouds, storms and changing weather patterns.
Football
Gravity pulls the ball back down after it is kicked into the air.
Questions about the Universe
These questions answer the things beginners usually wonder about after reading this page. Open each question to see a simple, direct explanation.
Why is space important to learn about?
Space helps us understand Earth, seasons, time, gravity, weather, satellites and our place in the Universe.
Can beginners understand astronomy?
Yes. Astronomy becomes much easier when it starts with familiar ideas like day, night, the Moon and the Sun.
Why do planets stay in orbit?
Planets stay in orbit because they move forward while gravity pulls them inward.
Are the images and examples connected to the topic?
Yes. Each space page uses related explanations and visuals so readers can connect the idea to something they can picture.
More real-life examples and practical understanding
Space topics become easier when you connect them to movement. The Earth spins, the Moon orbits Earth, Earth orbits the Sun, satellites orbit Earth and spacecraft follow planned paths through space. Gravity pulls objects together, while motion keeps them moving forward. That balance explains why planets do not simply fall into the Sun and why satellites can stay above us long enough to support GPS, weather forecasts and communication.
Why this matters
When a topic connects to something familiar, it becomes easier to understand. ExplainItSimply uses everyday examples so readers do not have to memorise difficult words before they understand the idea.
Simple space connection map
- Gravity pulls objects together.
- Motion keeps objects moving forward.
- Orbits happen when gravity and motion balance in a path around another object.
- Satellites use orbits to support GPS, weather monitoring and communication.
- Space missions use science, engineering and software to travel safely.
A visual reminder that the universe — galaxies and space connects to real systems, real decisions and real life.
Quick recap
You Have Learned This
You have learned the main idea behind The Universe — Galaxies and Space, why it matters and how it appears in real life. You have also seen that difficult topics become easier when they are explained step by step with practical examples.
Remember this
The goal is not to memorise big words. The goal is to understand the idea well enough to explain it to someone else in simple language.
Deeper Understanding
The Universe — Galaxies and Space Explained Through Everyday Life
Have You Ever Wondered?
Have you ever wondered how space affects everyday life, from GPS and weather forecasts to tides, seasons and the stars you see at night?
The Simple Answer
Space is not separate from daily life. Satellites, gravity, the Moon, Earth's rotation and the Sun all affect things people use or experience, including navigation, seasons, tides, weather information and communication.
The Journey Behind The Scenes
Most topics become easier when you follow the full journey from start to finish. Instead of memorising a definition, follow what happens first, what happens next, who or what is involved, and why the result matters.
Object In SpaceGravityMotionOrbit Or EffectEarth ImpactDaily Life
Weather From Space
Weather forecasts use satellites, ground stations, radar, ocean sensors and aircraft observations. Satellites watch clouds, storms and moisture from orbit. Computers combine this information into forecast models, and meteorologists check the results before forecasts reach TV, websites and phone apps.
Moon, Tides And Tilt
The Moon helps create tides, which are the rise and fall of ocean water. Its gravity pulls on Earth's oceans and creates bulges of water. The Moon also helps keep Earth's tilt more stable. Tilt means Earth leans slightly as it travels around the Sun, and that lean helps create seasons.
Why This Matters
Understanding this topic helps you see the hidden systems behind everyday life. It also makes other topics easier to learn because technology, science, money, aviation, space and AI are connected. When you understand one part of the journey, the next part becomes less confusing.
You Have Learned
You have learned the main idea behind this topic, how it works and why it matters in real life. You should now be able to describe the process in your own words and recognise where it connects to other subjects.