A journey to Pluto can help us fix religious public holiday dates

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

11 Aug 2019

Space travel is not like driving or flying where the engines of the vehicle are kept running or the driver stays at the controls throughout the journey. If you did that on, say, a journey to Pluto – 5 billion kilometers away – you would need so much fuel that the spacecraft wouldn’t be able to take off the ground!

In addition, since the journey takes about ten years, a large team of astronauts would be required to take turns at the controls to keep the spacecraft on the right path. In short, such a plan would fail from the word go.

So, how did NASA send a probe to Pluto in 2006? Well the spacecraft was aimed at the target, short with a very large force and allowed to travel for ten years with minimal guidance.

That takes very high precision aiming and timing. Pluto is a moving object travelling at about 17,000km/h. It is also very far away – 5 billion kilometres from Earth.

The spacecraft was fired from a moving object (the earth).

To make matters worse, Pluto was discovered in 1930 and it takes 249 years to make one revolution around the sun. So, by 2006, it had only covered about 30 per cent of its orbit since discovery. There is no certainty about how it will behave in the remaining 70 per cent of orbit.

Now, the further a target is, the more difficult it is to strike. For an object 5 billion kilometres away, if your aim if off by just one degree, you will miss the target by 87 million km!

To get within, say 100km of the target, the targeting equipment should be able to aim within about one-millionth of a degree. That’s like trying to shoot a strand of human hair from 5km away!

Yet only four trajectory corrections were done in the entire ten-year journey: two in 2006, one in 2007 and a final one three years later in 2010. Three lasting just one minute each and the longest one 15 minutes. In the five-year period from 2010 to 2015, the spacecraft travelled directly to its target encounter with Pluto without any further assistance.

I tell this story four years late because there is something that has disturbed me about our country for quite some time now. If there is technology available to aim a spacecraft to a moving object 5 billion km away, how come we cannot predict the date of a public holiday just one year in advance?

Many people assume that religious public holidays depend on moon sightings hence they think it is impossible to tell the dates. That is simply not the case! Predictions can be made even centuries in advance.

And, like I have written here before: if we can announce the date three days ahead, we can also announce it three months, or three years, or three decades in advance. We need to wake up.