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Do you believe we are alone in the universe?

The universe is far, far, far too big and ancient a place to reasonably rule out life elsewhere. Even if the galaxy is currently lacking intelligent life other than our own (and I'm not convinced it is - our expectations of what intelligent life should be doing with itself is, obviously, prejudiced toward our own ideals), I don't think it was nor will be. I'm also much more optimistic about FTL. :)
 

The “our knowledge of the universe is incomplete, therefore you may not assert anything” is pretty much a conversation ender. If we can’t assert anything, what’s the point of even talking?

I feel like it must be a logical fallacy, too, but I’m not familiar enough with all the common fallacies to say for sure.

Closely followed by “scientists sometimes revise their hypotheses, so scientists can’t assert anything”. Which you also used.

They’re both largely nothing-statements. :)

I'm not saying we can't assert anything. I'm just saying that we should be qualifying our assertions with at least a "At our current level of understanding X is/isn't possible.", rather than just declaring something impossible.
 

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Yes and no. Stars with chemical composition similar to those in the rest of the galactic plane are found at great distances, but there's some question as to their density. It may be that there are some outliers, but the main disk could still be 100 - 150 thousand light years.

But, either way, that only makes the job of getting across the galaxy harder. Folks often talk as if self-replicating machines are somehow static, never-changing entities, as if they can last 10,000 years without alteration, and would replicate perfectly, and that's a naive position to take. It would be more reasonable to consider such a probe to be a living thing, with an electro-mechanical (or whatever) basis rather than a biological one.
Maybe it would actually be better to rely on something biological, though. Carbon, Hydrogen and Oxygen are fairly common in the universe, and if you, say, need to build your drones to a large part from iron and copper, it might become impractical to self-replicate.

But maybe the truth is you can't do it with small machines at all. The only way to support anything self-replicating is to have a star and a planet in its orbit at the right distance for the right temperatures with the right planetary compistion. Only then you have enough base materials and the right conditions to support the type of catastrophic failures that can happen over millions or billions of years.
The only way to explore the universe and reach out is to "fly" a star system. We're already doing that, but we can't steer it...
 

Maybe it would actually be better to rely on something biological, though. Carbon, Hydrogen and Oxygen are fairly common in the universe, and if you, say, need to build your drones to a large part from iron and copper, it might become impractical to self-replicate.

It doesn't really matter what you make it out of. The radiation out in interstellar space is powerful stuff, because much of it originates in the most powerful events in the universe - cosmic rays will damage DNA or flip/destroy computer memory bits with equal ease.
 

It's hubris to think we know for certain whether or not it's possible to have perfect replication.

With respect, we are talking about the Laws of Thermodynamics here. Being able to outdo the Laws of Thermodynamics is, in all cases, equivalent to creating a perpetual motion machine, and that's a source of infinite energy*.

And, if you have access to infinite energy, you don't need any bloody self-replicating probe. You have *INFINITE ENERGY*. Even with the lightspeed barrier, infinite energy means you can send living people at arbitrarily large fractions of the speed of light, which means arbitrarily large time dilation effects. From Earth's perspective a trip may take 100K years, but from the point of view of the travelers, reaching another star is pretty much instantaneous with enough time dilation.




* If I recall correctly, infinite energy is also equivalent to a violation of causality, which leads to silliness like you being born before you are conceived. And I am pretty sure nobody wants that. :p
 


But in any case a quick google search showed the top ten Oldest Animal Species On Earth: the youngest is Martialis Huereka-120 million years old and the oldest is Cyanobacteria – 2.8 billion years old. So are Cyanobacteria breaking Newtons laws of Thermodynamics?

No, they aren't. What we have today is basically the same kind of organism, but it isn't *completely unchanged* over 2.8 billion years.

Which is to say, you are mistaking "oldest known distinct lineage" for "oldest species". Martialis huerka it the only still living twig on the branch that came off closest to the trunk of all other ants. But, that ant of today is not the same as when it branched away from the common ancestor of other ants - it has been evolving along during that time.
 

I'm a bit late to this, just let me begin with saying I truly believe -If I'm not certain- that we are truly alone in the universe, at least by a given definition of universe. And by that I mean I believe there's nobody else in our Hubble Bubble which by all means and purposes is the practical limit of our universe. Lightspeed is the hard limit, and will be until we find a way to manipulate mass/gravity, but that is unlikely. Even warp engines -which are actually possible under the laws of physics should we find an energy source big enough to produce and store enough antimatter - wouldn't be practical, as the effect of bending the space actually destroys whatever is in your way.

When people look at the Drake Equation they automatically jump and think "Well whatever the actual numbers, given the age of the universe is in the billions there's got to be a ton of other advanced civilizations out there". But there's something we are forgetting, the values of the drake equation aren't necessarily constant, and the whole thing is indeed not uniform (I.e. The rate of birth of new stars is slowing down) . Which means the actual solution can't be found by simple substitution but by integration, of a seven variable function, which means that no matter how high the values are, since they all are less than one, their integral will be even smaller so we are talking about a number below 1*10^-10, and the age of the universe is in the order of 1*10^10, so the solution is actually closer to one or even less than one-and that means us.
 

No, they aren't. What we have today is basically the same kind of organism, but it isn't *completely unchanged* over 2.8 billion years.

Which is to say, you are mistaking "oldest known distinct lineage" for "oldest species". Martialis huerka it the only still living twig on the branch that came off closest to the trunk of all other ants. But, that ant of today is not the same as when it branched away from the common ancestor of other ants - it has been evolving along during that time.

Even more recent living fossils aren't exactly the same as they were millions of years ago.
 

No, they aren't. What we have today is basically the same kind of organism, but it isn't *completely unchanged* over 2.8 billion years.

Which is to say, you are mistaking "oldest known distinct lineage" for "oldest species". Martialis huerka it the only still living twig on the branch that came off closest to the trunk of all other ants. But, that ant of today is not the same as when it branched away from the common ancestor of other ants - it has been evolving along during that time.

So then what exactly is your point? If imperfect replication can last for a Billion years then do you need perfect replication.

Or in other words, why would we care if the aliens we meet are actually evolved from what they were originally?
 

I
But there's something we are forgetting, the values of the drake equation aren't necessarily constant, and the whole thing is indeed not uniform (I.e. The rate of birth of new stars is slowing down) . Which means the actual solution can't be found by simple substitution but by integration, of a seven variable function..

I'm sorry, but that's not correct, for two reasons:

1) There is a term in the equation (L - the average lifetime of a civilization) that effectively maintains a window - unless L is on the order of the lifetime of a star, we don't have to worry about changes in the terms over cosmological timescales - like changing the rate of star formation. Unless L is on the order of geologic timescales, we don't have to worry about the ecosystem of the planet collapsing out from under the civilization (except by their own action, which is encapsulated in L), and so on.

2) The terms in the equation are *averages*, implicitly over the period L.

So, no multi-variable integration is required. Drake knew what he was doing.
 

Into the Woods

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