Sand On The Beach Analogy

[grunion]

In a conversation with a believer about extraterrestrial alien encounters, he posited that if I accepted the possibility of intelligent life elsewhere in the universe, then I was being closed-minded to deny that any of the reported alien encounters by earthlings throughout history were indeed actual encounters with an alien race. If it is possible, why couldn't it be true?

In response I suggested that due to the vastness of time and space, that if two grains of sand were chosen entirely at random from all the grains of sand on all the world's beaches, the probability that they were actually touching each other is greater than the probability that another intelligent race somewhere in the universe has encountered us.

Interestingly, he pondered that analogy and it gave him pause. But I wonder now how accurate it was.

Obviously due to all the unknowns there's no way to accurately put a probability on the number of intelligent civilizations that have ever existed in the universe. I have no idea how many grains of sand there are on all the world's beaches but I suppose that number can indeed be estimated.

Do you think my analogy was fair? If so I think it can be pretty useful.

 

[aggle-rithm]

It's probably impossible to say, but the huge numbers involved in the notion of interstellar travel are very unintuitive to most people, so a dramatic example is called for.

In order to know the probability of another species contacting us, you have to know the probability that other planets will have life, and that life will be intelligent, and that intelligent life has ventured into the very risky and possibly pointless exercise of trying to travel to other stars. Only then could you start to calculate the probability that such a species would somehow happen to blunder upon Earth.

ETA: This is assuming that faster-than-light travel is impossible, as it certainly appears to be at the moment.

 

[Overman]

Ah....see I use this Sand on the Beach analogy in a slightly different way...

When one of our buddies is thinking about bringing his woman to the (club, party, wedding, or even beach) we say 'Why bring sand to the beach?'!

 

[Hellbound]

I dunno about the sand analogy. Simpyl because life could not be right next to us int he universe. Even the closest star is 4 light years away. That doesn't sound like much, but it's a huge distance and would require an enormous expenditure of resources, energy, time, and people to make that trip, using any known or theorized technology. And a few cow anuses and redneck ova are unlikely to make that trip profitable in any fashion.

The distance issue is one to consider, perhaps by comparing the distance in terms of how far it is to our moon. Our moon is about 450,000 miles. 4 light years is (31,536,000 seconds/year * 186,000miles/second * 4 years) 23,462,784,000,000 miles. So it's about 52,139,520 times as far to the nearest star as it is to the moon. You can carry this comparison into whatever analogy seems adequate to explain the distance. And this doesn't even fgo into the distance to other stars, or those likely to hold environments conducive to light. I believe the nearest extra-solar planet detected is about 17 light years, assuming I'm not mis-remembering.

Once that's done, you still have to consider temporal distance. Our of 4.5 billion years since the Earth formed (and 9 to 15 billion since the universe), we've had the ability to detect signals from space (namely radio and similar) for maybe 200 years. For simplicity's sake, let's assume that even the very first reciever could detect any possible signal (a state we still haven't reached, btw). That means that we've only been able to detect another civilization for 1/22,500,000th of the time our planet has been here. Even if humanity survives for another 10,000 years, the amount of time we could contact another civilization is a vanishingly small percentage of the time the planet has been here.

Even assuming that 1 in 100 planets holds intelligent life (an absurdly high percentage based on everything we know), the chances of us being at a stage where both we and another race are technologically able to communicate, to recognize each other's communications, and both happen to be transmitting/recieving in the right directions, are comparible to you and your buddy going hunting and you accidentally shooting his rifle bullet out of the air with your own.

 

[tsg]

Do you think my analogy was fair? If so I think it can be pretty useful.

I don't know about fair in terms of being an accurate portrayal of the probability, but I would say it is fair in terms of this question:

If it is possible, why couldn't it be true?

My usual response: "It could be true. It just isn't."

This is the old "it's not impossible" dodge. The problem is we aren't arguing about whether or not it could happen, but whether or not it did. "Could be" and "are" are very different things. Not being able to show that it couldn't be doesn't support "it is". And I think the sand analogy points that out: yes, it's possible, but it's so unlikely that it may as well not be.

 

[clerihew80]

In a conversation with a believer about extraterrestrial alien encounters, he posited that if I accepted the possibility of intelligent life elsewhere in the universe, then I was being closed-minded to deny that any of the reported alien encounters by earthlings throughout history were indeed actual encounters with an alien race.

Alien encounters haven't been reported "throughout history." They only began in the twentieth century, after the concept of extraterrestrial intelligence began to filter into the public consciousness through literature, film, television, etc. Before that, it was abduction by faeries or Gods or demons or whatever impressionable people heard about in folk tales.