Hawking mentions values of physical constants that support life as being often given as an evidence that the Universe was designed. I was wondering once if the values of constants are not enforced by the structure of the Universe, and are not magic numbers that could theoretically be changed. Maybe we don't really understand the underlying mechanism that gives a physical constant a given value, and if we did, it could turn out, that the constant can not possibly have any other value.

Take PI as an example. People very well understand what a PI is and how it can be delivered. Because of this, we do not argue what would happen if PI had a value of 3.15... not 3.14... In a Universe with different PI circles wouldn't be circles, atoms or planets would maybe collapse, but such deliberations do not make any sense because what PI represents enforces the only value that it can have. Maybe the same is true for the electric charge and other constants Hawking mentions?

In case you missed it, this was written in 1996. A very interesting read indeed. Yet it is somehow disappointing to see that 16 years later, there are yet not a lot of examples of what he calls the "self-designing" of the human race. Quite contrarily there's still a strong opposition (both amongst the legislators and the general public) against stem cell research and human cloning in many countries.

It really is surprising that life could be so rare. But then you realize that the chance of us detecting life from a distant star comes in only very fine bands: in other words our post-SETI civilization needs to be within the light-distance of the star at or after they first produce radio communications but before they start using something far more advanced for communication that we don't yet know how to detect. Plus they need to not destroy themselves. And we need to actually look right at their signal, and notice it!

Basically what this means is: SETI is looking for stars that have developed intelligent life and radio roughly exactly as many years ago as they are light-years away from us. This minimizes the ease of finding significantly.

We could assume civilizations always use advanced forms of radio after they develop it but then why haven't we found life? We assume there must be a limit to the usefulness of radio in that sense. After all, we're moving to fiber etc.

I've always wondered what the minimum unit for mechanical life would be. I.e., what's analogious to a biological cell?

It seems to me to have an automated spaceship that can land on planets and produce more automated spaceships, it would require most of the tools available on earth in one way or another; vehicles, mining equipment, refineries, factories, and more. And for each piece say vehicles you need all of the infrastructure to create those.

Hawking is a great writer, I first encountered his writing with his "A brief history of time" book - which was easy to read for someone without much physics knowledge. http://en.wikipedia.org/wiki/A_Brief_History_of_Time

My favorite quote from the article "By contrast, there are about 50,000 new books published in the English language each year, containing of the order of a hundred billion bits of information. Of course, the great majority of this information is garbage, and no use to any form of life"

Never was there a more perfect candidate for the text-to-speech function in Safari.

"But Freeman Dyson has shown that, despite this, life could adapt to the ever-decreasing supply of ordered energy, and therefore could, in principle, continue forever".

Does anyone knows what he's talking about ? Dyson's sphere ? Surely there's some energy loss involved in the process ? But if it's true I'm happy to learn that an intelligent lifeform can theoretically live forever.

I believe there is a fourth explanation on why no intelligent life forms have presented themselves to us, and Hawking states the rationale in his article. The fourth explanation is that we have been visited by intelligent aliens, but they have hidden themselves, like the Star Trek "prime directive", so that we don't end up like native Americans to the intelligent aliens' Colombus.

I'm surprised at how little new information I found in this talk. Which is not to suggest I'm very knowledgeable, only that a few of my favorite wikipedia articles must do a damn good job of summarizing these topics, particularly http://en.wikipedia.org/wiki/Fermi_paradox

About classifying computer viruses as a form of life:

"Maybe it says something about human nature, that the only form of life we have created so far is purely destructive."

Other (constructive) computer programs could just as well be seen as a form of life. The difference would simply be that one spreads without our immediate consent and the other needs to convince us that it is useful to us before being allowed to spread (kind of like pilot fish). Both use a combination of pre-existing infrastructure/ecosystem to procreate - our brains, computers, language and other methods of communication.

They are all the form of life called memes or temes by Susan Blackmore (http://www.ted.com/talks/susan_blackmore_on_memes_and_temes....). (Also Dawkins et al)

Great reading!

I would like to add that the development of a brain is another huge milestone. Somehow Hawking forgets to mention that.

And the development of the computer and Internet is a big milestone in the external transmission period in my opinion.

If you like this kind of reading, I recommend the book: http://www.amazon.com/Short-History-Nearly-Everything/dp/076...

> because there's no way one can show a period of ten thousand years, on the same scale as billions of years

Isn't that what log scales are for?

This was an amazing read. It elegantly covers Life from the inception of the universe to what might occur next.

What I liked the most was when he talked about "externally transmitted information". I never thought of books and written knowledge as being part of human evolution as much as DNA, though it definitely fits the description.

Given he so eloquently puts the arguments, it baffles me to think that we might just be an extremely lucky and rare occurrence in the universe. To me, it is more terrifying to think we are the only ones, than to think there are aliens. The vastness of spaces suddenly seems so claustrophobic.

Is there an available Hawking text-to-speech converter? Or perhaps a recording of this by him?

I strongly recommend reading the Carl Sagan book in a similar vein called "Shadows of Forgotten Ancestors" for folks interested in a pop-intro to genetics and the history of life.

So many of the points made by Hawking could be used to justify Creationism, and yet it's waved off as 'impossible'. That is bad science.

<<This lecture is the intellectual property of Professor S.W.Hawking. You may not reproduce, edit, translate, distribute, publish or host this document in any way with out the permission of Professor Hawking.>> How to write for the net, 1980's style. It feels like a provocation to do so.

I haven't read the article yet, but I find the intro

"This lecture is the intellectual property of Professor S.W.Hawking. You may not reproduce, edit, translate, distribute, publish or host this document in any way with out the permission of Professor Hawking."

bad taste for a person carrying a degree granted by the public.

Besides, is my squid proxy already in violation of this?

EDIT: Seriously, why the downvotes?