Life in the Universe part 7: How long will a civilisation remain willing and able to communicate?

This is part of the Life in the Universe series of posts. Go here for the first one.

Part 6 dealt with the fraction of intelligent life forms that will develop the ability and desire to communicate across the stars. This one takes the next step and asks how long such civilisations will remain in such a phase.

As with many aspects of other posts in this series, the only real evidence we have available to us comes in the form of life on our own planet. The only species on Earth that has so far developed the ability to build the technology required to communicate with civilisations on planets orbiting other stars is us, the human race, and we've only been able to do it for a relatively short amount of time. While we're not actively trying to communicate beyond our own planet, whether or not to begin doing so is being debated right now by many people in certain fields of research. So, if we're at the beginning of this communicative phase:

How long will we remain able and willing to communicate?

To simplify, lets assume that we stick around on planet Earth and don't develop stable, self-sufficient advanced communities in other solar systems. In this case, we can put an upper limit on our time on Earth: Our main source of heat and light, the Sun, will die in approximately five billion years. We cannot, at this time, conceive of a way of living without such a power source, so 5 billion years could be a top-end estimate for our communicative phase's time span.

However, the Sun will start to get uncomfortably hot for us in only around 500 million years. It's feasible that we will find (relatively) short term ways of dealing with this, but I think it's a fairly safe bet that our priorities with regards to technology, research and finance will point in this direction rather than one of communication.

So, with a limit of around 500 million years, we can start looking at other factors: there are plenty of things that could cause the snuffing-out of life on Earth long before that 500 million year period is up. Comet or asteroid impacts are probably the most widely known, thanks to movies like Deep Impact and Armageddon, but there are many other events that could wipe us out, some of which I discussed in a previous post, what could cause the human race to become extinct?

That's the morbid stuff out of the way. Something else we have to consider, though, is even if we are capable of sending off signals to the stars, and even if we really, really want to, is it always going to be feasible? To commit the resources to sending off signals and listening for responses (remember, it is likely to take hundreds of years at best to receive any response- to send a signal to our nearest star and receive one back would take an absolute minimum of eight years. Most stars are much, much further away from us) our society here on Earth would need to be stable, with comfortable amounts of food and energy to support its population. War and environmental disaster would disrupt any communication programme (these would be seen as much more important uses of funds and resources!) At the moment the human race cannot commit the required resources because these things are not in place. Will they ever be? Who can tell.

How long will a civilisation remain communicative?

Taking these things into account, current estimates range from a few thousand years to a few million, though somewhere between 10,000 and 100,000 years seems to be a popular and sensible estimate for the length of any given intelligent civilisation's communicative phase.

Life in the Universe

This is the seventh in a series of posts about life in the universe, culminating in a discussion about the Drake Equation. The first post concentrated on the number of suitable stars formed each year, and the next will be the final instalment detailing the Drake Equation itself.


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