We, humans, love to put ourselves at the centre of things. For this reason, we believed for years that the universe revolves around us and that the stars have no other purpose than to show us our way.
We were the most beautiful, the greatest, the most intelligent of all created. Then over the years, We have made various discoveries using this intelligence. But with every new bit of information we learned, we got smaller and smaller.
For us who have been measuring the greatness with our own little kingdoms for centuries, the size of the universe was greater than we could ever imagine.
In fact, the Earth is not small at all for our unit of measure. The circumference of the it is 40 000 km. If you were to go around the world with your 100 km per hour car, it would take about 17 days.
Our nearest neighbour, the moon, is about 384 000 km away from us. If you could drive the same car to the moon (why not, it's maybe a Tesla) you could arrive in almost 6 months.
The brightest star we've seen in the sky: our sun. How beautiful it shines. As if we will touch and hold. But it is 150 million km away. Even a beam of light to reach us therefrom takes 8 min. In the photos, we see it as if it is a little bigger than our world. But in fact, it is so much bigger than us that 1 million 300 thousand worlds can fit in it.
There are two planets between him and us: Mercury and Venus. But we don't have to be afraid. They cannot compete with us. They are smaller and warmer than Earth so there can be no life there.
Mars comes after Earth. Almost the same size as us. It's 225 million km away. Our car, which travels 100 km per hour, gets there in 260 years. But at this point, driving our little car won't be useful. We can base our spacecrafts. But even for them, it can take more than 9 months to reach Mars.
After passing the asteroid belt around the sun, we reach the outer solar system. The gas giant Jupiter welcomes us. The first born child of the solar system. And this is its signature giant red spot. A storm, four times bigger than the world that has raged for centuries. Yep, it's a little enviable planet. It is 1300 times the size of the Earth. And it looks like it has a solar system of its own with exactly 79 moons. The distance between him and us is almost 1 billion kilometers.
And Saturn. Look at these beautiful rings. It is approximately 1 billion 300 million km from us. It is so far, that it took 7 years to reach it for the Cassini-Huygens spacecraft who was travelling at 120 000 km per hour.
Uranus. Another blue planet of our solar system that continues its journey at a nearly right angle around the sun, it is approximately 2.7 billion km from Earth.
And the last planet of the solar system: Neptune. It is about 4.3 billion km away from Earth. For the Voyager 2, the first spacecraft who photographed Neptune, it took 12 years to reach it.
Speaking of Voyager 2, its brother Voyager 1 is the furthest man-made vehicle from Earth. During his career, which started in 1977, he travelled almost 22 billion km. And he's been playing our music in the galaxy ever since.
Our closest neighbour is Alpha Centauri. It is 40 trillion km, or about 4 light-years away. Voyager 2 is currently heading for it at full speed, but it will take 73,000 years to reach. Even 2500 generations after us will not see it get there. Our little car, which can make 100 km per hour, would arrive in 47 million years. We said we would never talk about that car again, right? The human way of thinking. Nothing to do!
But when talking about great distances, Let alone our small car, even our fastest spacecraft will not be enough. From this point on, we will be using the speed of light, which is the unit in the universe, to measure lengths.
The solar system and several stars around it make up the Local Interstellar Cloud. This region is about 30 light-years across.
We are now in the Orion Arm, one of the four arms of our Galaxy. It is almost 10 000 light-years long. And it is estimated that there are 50 to 100 billion stars in this arm alone.
And our home galaxy, the Milky Way. It is almost 100 000 light-years long and 1000 light-years thick. It's almost as old as the universe itself, about 13.2 billion years old. It contains 200 to 400 billion stars. Our Sun is almost 26 000 light-years away from the centre of the galaxy. It takes about 220 million years to complete one tour.
We've come a long way here. But still we are not that far away. Let's visit our next-door neighbour: Andromeda. 2.5 million years away. It is several thousand light years wider than the Milky Way.
These two neighbors and about 50 other galaxies together form the Local Group. It is almost 10 million light years in diameter. Think about it, more than 50 galaxies and they all contain 100 billions of stars. But still, there is more.
When we get a little bit more open, we encounter the Virgo Supercluster, which is 55 million light-years in diameter and contains more than 100 local groups. Every bright spot we see at this stage, is a galaxy. Thousands of it. When we look from this distance, let alone the sun or the earth, we cannot even tell which one is the Milky Way galaxy,
We have reached the final stage within our technology and the speed of light: The Observable Universe. In this area, we can see the remnants of Cosmic Microwave Radiation from the Big Bang era. Its diameter is estimated to be 93 billion light years. It contains more than 2 trillion galaxies, and trillions of stars and planets.
Is that it? Of course no. Maybe this area does not correspond to one in 500 of the whole universe. So if the whole universe were a basketball, the observable universe would be a marble. Well, if we are talking about an area whose diameter is 93 billion light-years like a marble with a diameter of 4 centimetres, what is our solar system in that marble? An atom of it? Or it's not even a proton in that atom? And if the sun is considered the size of a proton, what is the earth? Is it a quark? Even smaller? What about us? The creatures who live on a quark grain and who think that they are the only inhabitants on this basketball and that ball was created for their sake only?
Yes, we are very small. And this smallness should add humility to us, should tell us what we really are when we see ourselves too high.
But no matter how small we are, ultimately, we do exist. And we are truly incredible creatures. Maybe, we are really the ones who give meaning to the universe. At some point, how could this great being know about itself without the creatures to discover it? Perhaps we really are a way for the universe to know itself. Yes, we may be the creatures lost in this greatness so much, that it cannot be seen from afar. But this should not upset us because we are too small. On the contrary, it should make us happy to be part of such a great thing. After all, we were made of the same stuff.
And within this greatness, I think, our responsibility is to realize the insignificance of our small benefits, against the size of the universe, and to work for the bigger causes.
Our responsibility is never to be content with what we discover, but to always want to discover more.
Our responsibility is to realize how special everyone we meet on the street and to show everyone the respect and the value they deserved. Because as Carl Sagan said: In a hundred billion galaxies, you will not find another.
