Communicating at one billion kilometers per hour is easy!

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

13 September 2009

Allow me to respond to some reader’s questions that have been sitting in my inbox for quite a while. The first one is from Justin Njagi of Likoni, Mombasa. He writes: “We’ve heard, about sound on earth and also…about humans living in outer space at the International Space Station (ISS). How does sound travel there and at what speed [considering that] there is no air, wind or gravity?”

The quick answer is that sound does not travel through empty space. In fact, it cannot exist in vacuum! It needs a medium like air or a solid or a liquid. In addition, it does not need gravity to travel from one point to another. Therefore, the question Justin is asking is how the people at the ISS talk to those on Earth.

The answer is by using radio waves. Unlike sound, these waves are electromagnetic in nature and therefore they do not a medium of transmission: they easily travel through empty space.

Without going into much technical detail, it should be enough to state that the process of converting sound into electromagnetic waves is not a complicated one: it is exactly the same thing that radio stations do in order to transmit their broadcasts to listeners over a wide area.

Since the communication with the ISS is through radio waves, it follows then that the speed of transmission is equivalent to that of light – approximately 1,000,000,000 (one billion) kilometres per hour! This is because all electromagnetic waves travel at this speed.

The second question comes from Samuel Mwai who writes “Has anyone ever thought of the world and her sister planets being an electron while the sun is the nucleus? So as we think of the size and shape of the universe we perhaps should imagine ourselves existing on an electron (earth). So, … any given element forms a universe by itself … [and] when you drink water [or] eat food, you could be swallowing universes with beings like as! [Tell] me; do you think I’m crazy?”

No you are not crazy, Samuel! All you have done is inverted the reasoning that was used by Sir Ernest Rutherford one century ago. After the discovery of negatively and positively charged particles in atoms, Rutherford conducted experiments aimed at finding out how these charges are arranged in an atom… Interestingly, the year 2009 marks the 100th anniversary of the publication of his experimental results.

After two years of pondering the results, he concluded that the negative charges (electrons) must be circling the positive ones in the same way the planets go round the sun. Thus the (planetary) model of the atom was developed on the basis of the solar system. This is why I say that Samuel has reversed the thinking when he says we should think of our planet as an electron.

Further research however, showed that Rutherford’s model was not quite correct; indeed, the new thinking is that the electrons can exist anywhere in the vicinity of the positive nucleus – they are not necessarily going around it in orbits!

Nevertheless, Rutherford’s model explains many of the experimentally observed properties of atoms and for that reason, it is still taught in schools around the world 80 years after it was proved inaccurate!