The Universe

A Galaxy is a collection of stars. The Milky Way has about 250 Billion stars. That’s 250,000,000,000 stars. So if the Solar System is our neighbourhood then the Milky Way is County Cork. Earth is located about halfway between the centre of the Milky Way and its outer edge. Again travelling at the speed of light it would take us about 25,000 years to get to the centre of the Milky Way. And we’re aren’t anywhere near the edge of the Milky Way. It would take 100,000 years to travel from one side of the Milky Way to the other. 

But we’re not done travelling yet. The Milky Way Galaxy is part of a group of Galaxies. Imagine them as our province, Munster. Ours is called The Local Group. To travel from one side of the Local Group to the other would take an amazing 10 million light years. That’s 10,000,000 years traveling at the speed of light.

The Sun provides us with heat and light and sits at the centre of our Solar System. The light from the sun doesn’t reach us instantly. It takes some time for that light to reach us. Light travels at a very, very, very fast speed. In fact it travels at a speed of 300,000km per second. Light from the sun reaches the Earth in about 8 minutes. In a light year you can travel 9.5 Trillion km (9,500,000,000,000 km)

When you look up at the sky at night you are looking further than our Solar System. All those tiny stars are actually Suns but they are a very, very, very, very long way away. What you are seeing is stars from a galaxy called the Milky Way.

Let’s take things a bit further and start thinking about how far you could travel in one year if you were travelling at the speed of light. We call this a Light Year. Our Solar System is about 2 light years from one end to the other. This means that if you were travelling on a spaceship from one side to the other it would take you 2 years to get there. Remember it would take you about 1 tenth of a second to travel around the Earth. 2 years is taking you on a very very long journey. And we’ve only just reached the edge of the Solar System.

It took the Voyager 1 Spacecraft 35 years to reach the end of the Solar System. And it started its journey from Earth and not the edge.

The Earth is about 12,000 km in diameter. If you could travel at the speed of light you could travel from one side of the earth to the other in 4 hundredths of a second (0.04 seconds). If you were travelling on the Equator around the World you could make the journey in 0.13 seconds.

We have traveled from our house (The Earth) to our neighbourhood (the Solar System) to the furthest known reaches of our Universe but even that doesn’t do the size of it justice. It would be closer to think of the Solar System as being your bedroom (or maybe even just your bed) and not as big as your neighbourhood. If that were the case then the Earth itself would simply be the smelly sock you left under the covers. It’s not such a small world after all.<br/>

Our neighbourhood has 8 planets, including Earth. We call this neighbourhood The Solar System. The Solar System also has few smaller planets known as Dwarf Planets. There are currently 5 Dwarf Planets in our Solar System but there could be more. Our Solar System is big and we still have a lot to explore. Some of the planets in our Solar System have moons. We have one moon orbiting the Earth while Jupiter has a whopping 79 moons.

And even at that there is more. Think of these enormous Super Clusters as our planet, Earth. Between them is empty space but there are believed to be hundreds if not thousands of these clusters throughout the universe. They are all moving through space and some are even moving towards each other. But don’t worry. With the distances we’ve just looked at it will be a long time before they meet.<br/>

We live on a planet called Earth. The Earth revolves around the Sun which is our nearest star, by a long long way. How long. We’re about to find out. Prepare for a very long journey.

Imagine the Earth as the house you live in.

Yes you guessed it-we’re not done yet. Our Local Group is part of a Super Cluster called the Virgo Supercluster. Imagine this as our country, Ireland. To get from one side of this to the other would take 110 million light years (110,000,000 light years). This Supercluster is about 100 billion times the size of the Milky Way. In fact there are about 2,000 galaxies in the Virgo Supercluster. The scariest part. There are millions of these Superclusters in the universe.

And there’s more. Some of these Superclusters are part of bigger units that can span billions of light years across. This could be described as our continent, Europe. We are part of a Supercluster of Superclusters called Laniakea (immeasurable heavens in Hawaiian). Laniakea is believed to be made up of about 100,000 galaxies and it would take you 500 million light years to cross (500,000,000 light years). 

So how big is the universe? We really don’t know. Especially because it is still growing. When we look at the sky at night we are actually looking back in time. The universe is believed to be about 14 billion years old. This means that any light we see must have been traveling for this long. We call this the Observable Universe. But because the universe is still expanding the distance has grown even more in that time. In fact that place that was once 14 billion light years away is now 46 billion light years (46,000,000,000 light years) away and getting further away all the time.

And Laniakea isn’t alone. Right next to Laniakea is another of these Superclusters. This one is called Perseus-Pisces. 

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