Archive for octubre, 2010

Video de Sir Martin Rees sobre lo que no sabemos

domingo, octubre 17th, 2010

Martin Rees. (Wikimedia Commons)

Un usuario de este blog me hizo llegar el siguiente video sobre este tema. Dura casi 50 minutos, se llama «Lo que aún no sabemos» (What we still dont know), y está en Google Video. El autor es el cosmólogo y astrofísico inglés Sir Martin Rees.

What We Still Dont Know

Las respuestas íntegras de Duncan Forgan

domingo, octubre 17th, 2010
Duncan Forgan. (Imagen obtenida de

Here are the complete answers of Duncan Forgan, researcher of astrophysics at the University of Edinburgh, to my article about the possibility of alien life.

I told him:
«We watched last Sunday in our country the Discovery Channel documentary with Stephen Hawking, and I saw your work mentioned in a BBC article called «Number of alien worlds quantified» (February, 2009).
«It would be great for my article if you could answer a few questions.

1. Which is the number of intelligent civilizations you deem most likely in our galaxy (and why): 1, 361, 31,513, 37,964, 1,000,000?

Forgan answer:

Thanks for your mail.  Here are some answers for you, I hope they are useful!

1. At the minute, all of those numbers are still possible.  Which number you come up with depends on which assumptions you make about life and its evolution into intelligent life.  I expect that the real number is closer to the tens of thousands.

2. Do you think there is a possibility of contact with alien civilizations?

2.  Sadly no.  Even if there are tens of thousands of civilisations in the Galaxy, they are likely to be separated by vast distances.  The speed at which communications could travel is the speed of light.  The Galaxy is 100,000 light years across, which means signals would take 200,000 years to travel that distance and come back to us.  While aliens might be a little closer, my research indicates not much closer, maybe 1,000 light years away.  This means that if we send a signal now, we wouldn’t get a response until 4010.

Also, civilisations have to exist at the same point in time to communicate.  The number tens of thousands is throughout the history of the Galaxy (nearly ten billion years).  All these facts make the probability of communication very low indeed.

3. Could there be life on Mars? Or, could life have existed on Mars?

3. This is very difficult to say! There appears to be geological evidence of liquid water on Mars in the past, which would be very helpful for life.  It’s possible there may still be habitats for life under the surface in the permafrost.  If there ever was life on Mars, then it’s  unlikely to be more sophisticated than simple, hardy bacteria that can survive in conditions most lifeforms would think of as thoroughly unpleasant.

4. The possibility of life in the universe is rare or frequent? What do you think? Are we average or the exception?

4. I suspect that simple bacterial life is probably very common.  I wouldn’t be surprised if we found it in our own Solar System (say on Jupiter’s moon Europa, or Saturn’s moons Enceladus or Titan). As for intelligent life, I suspect that it may be moderately common, but in such a vast Galaxy, quite insignificant and probably impossible to communicate with.  Most of scientific theory since Copernicus begins with the premise that Earth and its occupants do not occupy a special place in the Universe.  I hope to live to see the day when that can be tested!

Best Wishes,

Duncan Forgan

Postgraduate PhD Student
Institute for Astronomy
School of Physics and Astronomy
University of Edinburgh
Royal Observatory
Blackford Hill

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