The discovery of a new planet is always an occasion to celebrate. For it may generate a rise in confidence that we are not alone in the universe. Although until about 1992, we had no evidence to say that stars other than the Sun have planets, now we have at least a thousand examples of planets around other stars. The technology that made this transformation possible can be described on another occasion. Right now we can credit the space telescope mission Kepler with the rapidly rising extra-solar planets.
The recent announcement of the finding of a planet in an environment similar to the Earth has once again given rise to speculation as to whether we have alien neighbours similar to us. The planet called Kepler-452b is not exactly a stones-throw neighbour… its distance from us is close to 1,400 light years. That means, light from the planet would reach us in 1,400 years. But distance apart, the information about the state of the planet makes it worth exploration.
For example, its diameter is about 60 per cent larger than the Earth’s diameter, while it is five times as massive as our planet. Its Sun is twice as massive as ours and it takes about 385 Earth-days to make one round of its Sun. The overall age of the planet is estimated at six billion years, more than the age — 4.6 billion years — of our Earth. The planet is believed to be in eco-friendly zone which allows it to maintain water in liquid form. Keeping in view the characteristics of our own planet, it is being argued that Kepler-452b is an elder brother of Earth.
This has raised the expectation that we may have at last found a planet with likely living systems and it may even have advanced aliens. By “advanced” we imply “superior to us” in intelligence and technology. In this day and age, information is taken as a measure of advance. A method of measuring information of a civilisation can be as follows. Suppose we have five on/off switches close to one another. Given that there are two possibilities for each switch and that the switches act independent of one another, the set of five switches give us 2×2×2×2×2, that is, 32 possibilities.
These could be used to codify the English language with each letter of the alphabet being represented by a well defined combination of five open or closed switches. Since the alphabet has 26 letters, we can use the remaining six for various punctuation symbols. In short, we may identify each switch with a unit of information and say that each letter is represented by five info bits. Continuing this, we may say that the average length of a word is four and this will need four times five, that is, 20 information bits. Next we look at a typical book and say that each page on it has around 500 words corresponding to 500×20, that is, 10,000 information bits. Multiply this with the number of pages. Taking an average value as low as 100 pages per book we get a million info bits per book.
An exercise along these lines can be performed with more data. If one goes by Google estimate there are a little under 130 million books present today. Multiplying this number by our figure of a million per book we arrive at a figure of around 130 trillion info bits. Including pictures, music, etc., this figure may be increased up to a thousand trillion.
If we did a similar evaluation of human civilisations in the past, we would get smaller numbers. Thus we may look upon the creation of information as a measure of progress. Another supporting measure is the use of energy. The amount of energy used up per year in the world today exceeds the energy used over a century before the industrial revolution. One needs to conserve energy if we do not have new energy sources.
So imagine that we are in communication with a superior alien. What should we ask? Everyone has his or her own list. Mine would have this question: How can we solve our energy problem? Indeed, one reason for supporting programmes looking for extraterrestrial supercivilisations is to use their knowledge to solve our problems. There is, however, a strong reason for caution. For, if the aliens see what a pleasant planet the Earth is and how we are messing it up, they might easily dispossess us of this planet. So disclosing our existence may endanger us.
However, we need not fear any invasion from Kepler-452b just because we have found it to be similar to Earth. At a distance of 1,400 light years, our fastest messages, using radio waves, would take 1,400 years to reach them. If they decide to launch an invasion, they will at least take 1,400 years to reach us… that is, provided they can travel at speeds approaching light. Physics tells us that no material can travel with speed equal to or exceeding the speed of light. In fact, if we ask them a question today, their answer, if any, will come 2,800 years later. So it is a quest that demands infinite patience.
The writer, a renowned astrophysicist, is professor emeritus at Inter-University Centre for Astronomy and Astrophysics, Pune University Campus. He was Cambridge University’s Senior Wrangler in Maths in 1959.
