If you stop and think about it, it makes my hair stand on end: the dizzying dimensions of space.

The universe contains (at least) 2000 billion galaxies. That's a 2 with twelve zeroes… Ten times more than expected. One of those galaxies, our own Milky Way, would have a diameter of 200,000 light-years. That, in turn, is more than double than has been assumed so far.

Buckle up for a cosmic roller coaster ride!

For a long time man fulfilled a central role in the cosmos. The earth was nicely in the middle. The celestial bodies revolved in perfect circular motion around it. In this model you can clearly see distinct spheres in ascending distance to the earth. First you had the moon, then Mercury, Venus, the sun, Mars, Jupiter and Saturn. This model of Aristotle, further elaborated by Claudius Ptolemaeus, would remain intact the entire ancient times and Middle Ages.

Aristotle's cosmos

The rise of the new science changed all of this. Heliocentrism catapulted the earth, and with it man, away from the center. After more than a thousand years of tinkering with the equant and epicycles, the perfect circular shape had to give way to elliptical orbits. Comets turned out to fly through the impermeable atmospheres and supernovae sort out the illusion of eternal, unchanging stars.

How do we now think about the structure of the universe and what is the place of the earth/man in this?

• Step 1: The earth

Let us, like Aristotle, start on familiar ground: our earth. The big difference now is that we realize that it is no longer in the center of the universe. And that we now have to share our precious planet with 7.7 billion others, which is a factor 50 higher than at the time of Aristotle.

Moreover, we now know that man is only a very recent phenomenon. We made our entrance several hundred thousand years ago, while our planet already exist a sloppy 4.6 billion years and the universe even 13.8 billion years.

Step 2: The solar system

The earth is one of the eight (or nine) planets of the solar system. She is 150 million kilometers from the surface of the sun. Despite the tremendous speed, it took The Voyager 1 spacecraft 36 years to leave behind the solar system's outer regions. On November 5, 2018, Voyager 2 had followed the example of his older brother, after a 41-year journey.

Step 3: The Milky Way

In our solar system, it's all about the sun - literally and figuratively - but amidst her fellow stars she does not look very special. The sun is one of the estimated 250 billion stars that are part of the star system Milky Way. It is not remarkably large or bright and with its position in one of the spiral arms, it certainly does not occupy a special place.

The Milky Way has existed for more than 13.5 billion years. It has a diameter that has been estimated for a long time at 100,000 light-years (in kilometers, that is a 1 with 18 zeroes), but, as mentioned in the opening lines, it may be twice as much.

We are about 24,000 light-years from the center of the Milky Way, where an all-devouring black hole is located. To put this distance in perspective: the distance between earth and sun is 8.3 light-minutes.

Step 4: The Local Group

The Milky Way itself is one of many galaxies. Together with 53 companions it forms the Local Group. This cluster of galaxies has a diameter of roughly 10 million light-years.

Our closest 'real' neighbor (not including dwarf galaxies) is the Andromeda Nebula at 2.5 million light-years. Both neighbors are zipping towards each other at incredible speeds. The big clash is planned for within four billion years.

The Andromeda Galaxy

Step 5: Cluster above cluster

Clusters of galaxies, in turn, also cluster in even larger structures, superclusters. Our Local Group is on the edge of the Virgo supercluster, a colossus of several tens of thousands of galaxies. It has an estimated diameter of some 110 million light-years.

It seems that these superclusters also merge into even larger structures. The Virgo supercluster, for example, would form part of the Laniakea supercluster.

At the highest level of structures, the universe can be seen as a web-like pattern full of filaments, voids, clusters of galaxies and superclusters.

Step 6: The observable universe

And yet we are not at the end...

The universe we are talking about is the whole of structures that is observable to us. That includes all transmitted light that can be picked up by us since the big bang 13.8 billion years ago. At first glance this observable universe should have a radius of 13.8 billion years, but since the universe itself is expanding all that time, it is a considerably larger area, with a diameter of 93 billion light-years.

Beyond you can find the rest of the universe. A universe that is permanently unknowable to us...

Step 7: the multiverse

And maybe there will be an extra step.

From a theoretical point of view, such as string theory and a certain interpretation of quantum physics, this enormously large universe would in turn be only one of untold numbers of universes. For some string theorists, this number can reach 1 with 500 zeros.

Back to ‘our’ galaxy

As mentioned before, the number of galaxies in the observable universe is estimated at 2000 billion.

Assuming an average of 100 billion stars per galaxy, this brings the estimation of the number of stars in the observable universe to the staggering number of 1 with 24 zeroes.

Or, to give this number something tangible: ten thousand times the estimated number of grains of sand on earth...