Solar system stuff.

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I think the thing that 'confused' me at the beginning of this comment thread was that while infinities by thier very nature have no end (or if they are circular then they are not really true infinities, just closed systems), they do have beginnings.

And they have ends too, so actually, nothing is literally infinite in every sense. The universe will end, some unimaginably distant time in the future, and anything that ends isn't infinite.

--A

[peter]

Ahh yes, it will end - but is it not infinite in respect of 'space'?

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We don't really know, do we? But can we even say something is infinite in only one direction?

--A

[peter]

re the 'Universe' - as a word it has little meaning doesn't it; we should correctly talk either about the 'observable universe' or the 'non-observable universe' (and who knows what goes on there )

[Hashi Lebwohl]

The observable universe depends upon what you are trying to observe. Viewing objects using visible light will get us back only to the point of photon decoupling, or 13.75 billion years ago (give or take a couple of dozen million). Other phenomena appear to be able to be detected from earlier times. Combine this with the fact that the farther away something is from us the faster away it is moving, apparently even surpassing the speed of light because the space in between us is also stretching while the object is moving away and the "edge" of the universe approaches over 40 billion light years away. This is large enough to make it so that if you and I are 1 billion light years apart with both experience the observable universe as a sphere centered on us and our calculations of its size will be quite similar.

In short, the universe is infinite enough that we may think of it as truly infinite in the usual definition of the word. Maybe if somehow you could travel one parsec per day you could reach the edge but I am uncertain what that would be like--probably just background noise. I suspect that if we go far enough then there won't be galaxies--they hadn't formed yet.

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Close enough to infinite to make no practical difference huh?

--A

[peter]

Talking about a Universe of this size and age, did anyone ever satisfactorily answer 'Fermi's Problem' (the physicist Enrico Fermi, in consideration of the fact that there was in all likelyhood nothing special about our planet orbiting our sun in our solar system such that the development of astrophysicists in other similar systems was almost a given, is said to have asked "Where are they?"

[Vraith]

Talking about a Universe of this size and age, did anyone ever satisfactorily answer 'Fermi's Problem' (the physicist Enrico Fermi, in consideration of the fact that there was in all likelyhood nothing special about our planet orbiting our sun in our solar system such that the development of astrophysicists in other similar systems was almost a given, is said to have asked "Where are they?"

No, no definitive answer. And probably won't be until we either find someone [or they find us] or we search and exclude huge swaths of the universe.
Because in the problem, there are many, many variables that are "known unknowns." We know they are essential variables, have effects, but we have no idea what the values are/how to solve for them.
There are very likely "unknown unknowns." Variables/effects that we don't even know that we don't know. [But can heuristically assume exist because we have run across them in almost every endeavor...at which point they usually become known unknowns, then eventually become known knowns.
[heh...can't believe Rumsfeld said that, can't believe he was the first, but it makes sense to me]
And completely leaves out the Unknown knowns. Things we are sure we know but are wrong about.

[Hashi Lebwohl]

The exoplanets are out there; we simply have difficulty locating them at this time until we can get better interferometers into orbit. Only a small percentage of them will be in habitable zones, only some of those will be sufficiently solid, only some of those will be relatively the same size as our planet, and only some of those will also have liquid water and a similar atmosphere. Still...out of the potential dozens of billions of planets there have to be a couple hundred that will be similar enough to maintain carbon-based lifeforms. We will never visit them or be able to effectively communicate with them but they will be there nonetheless.

[peter]

And still we think quite possibly in too narrow terms. I quote David Deutsch, winner of the Institute of Physics 'Dirac Prize and Medal':-

The physicist Robert Forward wrote a superb science-fiction story Dragon's Egg based on the premise that information could be stored and processed - and life could evolve - through the interactions between neutrons on the surface of a neutron star....It is not known whether this hypothetical neutron analogue of chemistry exists - nor whether it could exist if the laws of physics were slightly different. Nor do we have any idea what other sorts of environment permitting the emergence of life would exist under those variant laws. (The idea that similar laws of physics can be expected to give rise to similar environments is undermined by the very existence of fine-tuning).

[Vraith]

Hee...I like that neutron-star life.

But I don't believe in fine-tuning.
I'm sure I've seen mention of several models with variations of up to 25% in the constants that still make a workable universe.

[peter]

Deutsch also is not a fan of fine tuning but he does not subscribe to the Hawking position of regarding life in general and hunanity in particular as nothing special (a thin scum on the surface of an uninteresting planet or some such words was how he described us) - on the contrary he firmly believes the possibilities for the future are almost limitless as far as we are concerned.

I'm suprised to read Hashi's comment that we will never visit or effectively communicate with our co-denizens in the Universe. Where is the trekkie in you Hashi! (I know the distances are unimaginably huge etc but never?)

[Hashi Lebwohl]

There is no trekkie in me, I'm afraid.

The only way to be able to communicate with some other species on a planet 100 light years away (or farther) would be with faster-than-light communication or FTL travel. FTL communication would require some sort of gravity ripple manipulation, tachyons (which we still cannot even detect, to the best of my recollection, so they are still only theoretical), or some sort of quantum coupling effect (but that would necessitate decoupling a pair here and sending one there). I suppose SRD's idea of an SCRT could work but both we and the remote species would have to have the same idea and build it the same way. FTL travel is most likely a complete impossibility without being able to translate an entire ship into some different dimension where space isn't like the space here.

The idea is fascinating and the foundation of nearly every science fiction world ever created but the reality is that even if we somehow detected a remote species we could never have meaningful communication. At best, we upload a couple of terabytes of information about ourselves and send it to them then wait for them to do the same.

Now...for some reason nearly every story about alien races supposes that those species are more technologically advanced than we are. What if their technology is similar to ours? In that case they would have great difficulty detecing us, as well, and it may be another 50 years before one of us accidentally discovers the other. What if their technology is less advanced than ours? In that case we will detect them first. If we sent our "hello" information it would be at least 200 years before their reply gets to us.

It is for these reasons that I conclude that even if we detect other species we will never have useful interaction with them. The fallout from the knowledge that we are not the only technologically-savvy species in the universe will be impossible to predict but I do know that the culture shock will be massive.

[Vraith]

It is for these reasons that I conclude that even if we detect other species we will never have useful interaction with them. The fallout from the knowledge that we are not the only technologically-savvy species in the universe will be impossible to predict but I do know that the culture shock will be massive.

I hope you are completely wrong about all of that.
Chances for "real time" communications...yea, very slim.
But we could collect all the important human knowledge in a year or so, then transmit it in an hour or two. [transmit it often over a long time so they don't miss it.] And they could do the same to us [if they're reasonably close to our level.] It would be worth doing. [Suppose we could open an eye in time over the Egyptians at their height. No real communication...but think of all the stuff we could learn/know for sure...and that's just from some dead "primitives."]

Simply the definite knowledge that others exist[ed] might be a shock...or not.
I mean, of all the folk I have any contact/communication with, I don't think there is a single one who thinks we are first, last, and only intelligent life. Everyone already believes they exist or have existed or will exist. So I doubt a massive shock...I predict massive EXCITEMENT.
I wish it would happen before I die...I wish it would happen right NOW.
NOW...go NOW...
guess they aren't listening.
Only fools would panic or go nuts.
Not that we don't have a supply of them. Maybe I'm being more optimistic than is warranted...
People are odd and unpredictable, after all.

[Hashi Lebwohl]

I agree--if I am lucky we will uncover definitive evidence of some other remote species before I die. Part of me does hope that my wet blanket opinion is incorrect but I am not going to hold my breath waiting for it.

I suspect the vast majority of our theologies will have to be either updated or abandoned upon proof of extraterrestrial species; this will cause unimaginable system shock. Some people will accept it--"well, what do you know? how about that"--while others will freak out wildly--"*gasp* there really isn't a God". A subset of the ones who freak out will probably commit suicide.

Regardless of whether we have reasonable communication with them we must meet them out there, not wait for them to show up here. We have seen what happens here when technologically-advanced country A lands on the shores of not-technologically-advanced country B--A wins the inevitable conflict 100% of the time.

[peter]

Theologies are nothing if not resistant. Look at the way the three monotheistic faiths have absorbed scientific advance where it suits them, rejected it where it does not and generally remoulded their 'explanations' to include the new post-enlightenment knowledge. I think 'contact' would mean only one thing to them - potential converts!

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But we could collect all the important human knowledge in a year or so, then transmit it in an hour or two. [transmit it often over a long time so they don't miss it.]

Uh, and tell whoever might be out there all about us huh? Isn't that the start of every alien invasion movie ever?

--A

[peter]

I seem to remember that Stephen Hawking thought that plaque on the side of the Voyager vessel was a really bad idea

[Vraith]

But we could collect all the important human knowledge in a year or so, then transmit it in an hour or two. [transmit it often over a long time so they don't miss it.]

Uh, and tell whoever might be out there all about us huh? Isn't that the start of every alien invasion movie ever?

--A

HEE...yea, a lot of them anyway.
But I'd find an invasion much more exciting, interesting, and valuable than
loneliness and the self-delusion of ultimate superiority.

But on Hashi's point of what happens when high-tech A meets low-tech B, I have 2 points to make:
First, the "primitive" often has greater effects on the "advanced" than history tends to recognize.
Second, maybe that result is cuz none of us are as "advanced" as we think and because all of those incidents were really just people meeting people.
No evidence or reason to assume it is some kind of "natural law."
I assume if we were the superior folk in such a meeting, we'd likely ruin them [not definitely, but likely]. The opposite doesn't have to be true, and nothing exists to base an opinion on.

[Hashi Lebwohl]

No, it isn't a natural law but history is rife with examples of the technologically superior nation utterly defeating their neighbors who are not quite as advanced. As I have noted before, our technology may be faster and our gadgets are shinier but we are essentially the same people we were 10,000 years ago--put two groups into the same area and it will result in bloodshed.

Broadcasting a terabyte or two of information about it is the extraterrestrial equivalent of tweeting or facebooking everything we do, revealing too much information for others to misuse.

I concur with Vraith--I think meeting an exoterrestrial species would be a wonderful break from the monotony in which we find ourselves so much of the time. I long for such an event to occur.