Trying to fathom the mind-boggling size of the universe

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

31 December 2023

The universe is mind-bogglingly large. In the year 2012, I illustrated that it is not possible to draw the solar system (the sun and eight planets) to scale. The reason is that the distances between orbits are so great that, if you scaled them down to fit on the largest piece of paper ever made, you wouldn’t get a pencil thin enough to draw the smallest planet to scale!

If we reduced the size of our planet (about 12,800km diameter) to the scale of the football (about 30cm), the moon would be about 9m away. In reality it is about 384,000km from Earth. In this model, the sun will be 3.5km away (150 million km in reality) and the orbit of Neptune, the last planet, would be about 102km away: if the globe was at Nation Centre, then Neptune would somewhere in Gilgil town! And since the real sun is about 100 times the diameter of the real earth, then, in this scale, it would be about 30m across.

We can extend this further. The farthest manmade object from earth is the Voyager 1 spacecraft, currently located about 20 billion km away. In the scale of the earth as a football, this comes to about 470km away. That is, from Nairobi to the southern most tip of Kenya at Lunga Lunga.

Even though this seems like very far away, it is nothing in the scale of interstellar distances. The nearest star to the sun is located some 41 trillion kilometres away. That’s an unfathomably great distance – light from there takes 4.25 years to get to earth. In the scale of the earth as a football, The nearest star would be more than one million kilometres away!

Suddenly, we are again not about to visualise the distance, even though is has been scaled down by a factor of 40 million. So, we need to scale down further. What if we reduced the Earth to the just a dot? The smallest one visible by the human eye is about 0.05mm wide.

Scaling the earth this size mean reducing it by a factor of about 256 billion. In this scale, the 41 trillion km reduces down to just 16km. And the sun’s diameter is just 5mm – about the size of a green-gram (ndengu).

So, imagine this: there is one ndengu seed at the Nation Centre in Nairobi and another one 16km away – at the gate of Kenyatta University on Thika Highway. And there is nothing in between! That’s how empty the universe is.