Some thoughts on the Fermi Paradox

[Mirannan]

I'm assuming that everyone on an SF board knows what the Fermi Paradox is, but the formulation from Fermi himself (Where are they?) probably sums it up as well as any.

It's a mashup between the anthropic principle, the "many worlds" interpretation of quantum mechanics and the Smolin evolutionary universe theory. (Heavy stuff eh? )

Briefly: There is a theory (a very poor one because, although testable, the results can't be communicated) that everyone is immortal or at least has a much longer lifespan than usually thought. Why? Simply because at many points in your timeline, there will be decision points at which one result leads to you being alive and the other... not. The many worlds theory implies that all the timelines exist, but as far as you are concerned only the ones that contain you alive count.

The evolutionary universe theory is simply that universes reproduce by something happening at the quantum gravity scale, probably by budding off in the middle of black holes. And the anthropic theory is that the universe is suitable for life simply because if it wasn't, we wouldn't be here to talk about it.

Finally, my little thought depends on some wrinkle of physics that we haven't discovered yet and may not, and if we do discover it we may or not play with it but probably will - and if we do, it sooner or later destroys the universe. (Something like metastable vacuum collapse, perhaps.)

So - we are here only because of a vast sheaf of possible universes, we live in a highly improbable one in which we are the only sapients - because in all the others where sapient life developed before us, they sooner or later found the trap in physics and destroyed their entire universe and all life within it. And since if that had happened in ours we wouldn't be here to discuss it...

Unfortunately, the corollary of this is that sooner or later, H. sapiens or our descendants will destroy the universe by our own stupidity.

 

[J Riff]

The aliens will not let us mess up their galaxy, don't worry.
Most of the biomass on Earth is in the deep ocean - no light, so who needs these surface-crawlers anyway.

 

[Michael Colton]

The perspective of these questions that always interests me more than the questions themselves (since I am not a physicist, so my ability to discuss it is similar to those 'for general readership' books that famous physicists write - namely, simplistic) is the likelihood that if we ever discover the answers to these sort of questions 'we' will no longer be 'we.' Our technological advancement in other areas is developing so much faster than our understanding of these theoretical physics questions that when we finally do understand them it is very likely that by that time we will no longer be human in any currently recognizable sense.

 

[farntfar]

All right.

Let’s take you’re conditions one by one.
First we are all immortal, because all events are possible in an infinite multiverse.* Therefore there is always a universe (or indeed an infinite number) in which we don’t die.
There are still an infinite number of universes in which we do and a similar number in which we never existed. **

The second bit, about the universe only being important because it has life in, just implies cutting the numbers down a bit, and doesn’t really affect the argument one way or another.

As for the last bit, the implication is that there is a possible and therefore existing universe (or there are several) in which the aliens have come to see us, but we don’t happen to be in that one.

There are also several universes where the dodgy physics event is not triggered either by other races or by us, either in the past or in the future, and presumably where something worse or better occurs later or earlier. (We all live but are even more thoroughly miserable perhaps. )
Further, unless, at the moment of my death or deaths my essence or being is somehow transferred to one of my still living alternate selves (ehem. I have a second theory! Which is mine.), the vast probability is that I won’t get to see it.


Or to conclude, the answer to the Fermi Paradox is therefore that the reason the aliens haven’t come in this reality is that in this reality the aliens haven’t come.


*Is multiverse still a usable term? Or is it out of date?
** I bandy the word infinite around here. And I accept that it isn’t infinite. It’s only the possible number of possible combinations of possible quantum states of all the possible quantum particles since the big bang. Therefore not infinite but a pretty large number.***
*** I accept that infinite implies things that bloody great big number doesn’t. In this instance I think the conclusion is the same.

 

[farntfar]

P.S.
Nice question though.

 

[Mirannan]

Ah, but farntfar:

Consider a less momentous branch point. (Example: on your way to work this morning you decided between a latte and an espresso.) Both branches, in this theory, are equally valid and both of them have a copy of you in them. Now consider a potentially lethal branch. In one of them, you live on indefinitely; in the other, you die a few seconds after the branch. (Hit or not by a car, perhaps.) There is a copy of your consciousness in each branch, but the day after the branch point the copy in the lethal branch is now irrelevant because it no longer exists. But the living copy has continuity of memory.

No transfer of consciousness either happens or is required. What has happened is that each time a decision is made, another copy is created. (Which probably means countless trillions of copies of you exist, because there are innumerable decisions in your past.)

It's a variant on the anthropic principle. There are billions of universes in which you exist, and countless quadrillions in which you do not. But from your point of view, the ones in which you don't exist are irrelevant.

 

[Vertigo]

My problem with the whole branching multiverse idea is that it just becomes silly. Mirannan suggests a "less momentous branch point" but if that will cause a branch then every decision point must be a branch and ultimately that comes down to quantum decisions; every time a quantum particle could be in two different places you have a branch, which means countless trillions of branches per nanosecond. And then there's conservation of energy (which works the other way as well - no energy for nothing) so where is the energy for all the matter in these multiverses coming from. It just doesn't add up.

I don't disagree with the idea of multiple universes I just disagree with the idea of them continually branching out in this way.

On Fermi's paradox; I've always said the fundamental flaw is that it assumes interstellar travel is an inevitable result of technological progression. With physics as we know it today I cannot see interstellar travel as practical, certainly not on any significant scale. And, with so much space out there, unless such travel is on a considerable scale it's none too surprising that no one has contacted us. And, of course, all that assumes that intelligent life is going to be common, which I personally doubt. In fact I personally doubt whether anything much more complex than microbes is going to be common out there.

 

[Mirannan]

Vertigo: Two possible answers to the conservation problem. #1; it doesn't apply to the particular case of a quantum branch point; reasonable, because that extra energy is inaccessible. #2; there is a reasonable argument that the total mass/energy of the entire universe is zero. The argument here is that the gravitational energy of the universe is negative, and equal to the mass/energy of all the particles within it.

As for your point about interstellar travel - well, maybe but that doesn't answer the question of why haven't we detected any signals yet? Including some distinctly non-obvious and accidental ones, such as the signature of a Dyson swarm - which doesn't require FTL. And we shouldn't ignore the point that at least four human artefacts are already on interstellar journeys.

 

[farntfar]

As I said, Vertigo, the number of branched universes on that princople is equal to the number of possible combinations of all the possible states of all the possible quantum particles since the big bang.
It has nothing to do with my decisions, except in as much as my decisions are presumably a result of quantum fluctuations in my brain.
We must assume that there are a zillion universes where I am exactly the same, but some quark somwhere else in the universe does something different.

The problem is its an all or nothing question.
In Asimov's "The Gods Themselves." he states that any number between one and infinity is impossible here.
In fact he's wrong, it's just an impossibly large number.

As for the bit about regrouping of essences, Mirannon, this is just a silly idea I had once to sort of explain why I wasn't dead yet.

 

[Vertigo]

I agree it's an all or nothing thing, which in turns pushes me towards the nothing end of the argument. But I'm no quantum physicist so I won't go further than that

Mirannan you ask: "well, maybe but that doesn't answer the question of why haven't we detected any signals yet?" The problem is that most of the various signals being transmitted out into space by ourselves (TV, radio etc.), and by extrapolation any other radio using aliens, is all coming from a point source and as such would not be detectable even from our nearest star.

For example, a TV picture having 5 MHz of bandwidth and 5 MWatts of power could not be detected beyond the solar system even with a radio telescope with 100 times the sensitivity of the 305 meter diameter Arecibo telescope.

So there's no real chance of detecting tv or radio. The only chance of detecting a signal would be a tightly focussed signal like a radar pulse or a transmission using a parabolic antenna (eg. Curiosity on Mars or Voyager). Then, with very little dispersion of the signal, it is possible it could be detected in other star systems but - and here's the reason SETI will never detect anything - that signal can only ever be detected if you happen to be looking in exactly the right direction at exactly the time a signal is arriving. What are the chances of that? How long would it take to scan the entire galaxy? That's how long an alien would have to beam a signal at us to ensure we received it without them even knowing if anyone is here. Not going to happen, sadly.

 

[Michael Colton]

On Fermi's paradox; I've always said the fundamental flaw is that it assumes interstellar travel is an inevitable result of technological progression. With physics as we know it today I cannot see interstellar travel as practical, certainly not on any significant scale.

This is the other part about Fermi's that has always seemed odd to me. Any implicit assumption of faster than light travel is a massive assumption. It is quite a leap to assume we will ever be able to harness enough energy to make it plausible.

 

[Mirannan]

Interstellar travel doesn't have to be FTL. Admittedly, keeping an interstellar civilisation together without it is difficult to say the least.

Vertigo, that doesn't mean that accidental "signals" aren't possible. For example, a body of size around 5 AU radius or so, radiating about as much energy as the Sun but all in far infrared, would be a fairly probable civilisation marker. Probable enough to take a closer look with optical instruments and radio receivers, anyway.

(A Dyson swarm wouldn't be perfect. And such an object might well involve small ships moving around inside the system, which are likely to be using fusion drives - which might well be detectable at short interstellar ranges.)

Further, I disagree that the mere presence of a radio-using civilisation wouldn't be detectable - this doesn't mean reading the signals would be possible. It's little known, but in radio wavelengths Earth is currently about as bright as the Sun.

 

[Vertigo]

Sadly I agree with you Sodice. However in fairness the Fermi paradox doesn't make the assumption of FTL but without it huge timespans required would leave you feeling why bother? Some unmanned missions for scientific interest possibly but manned? Unlikely I think.

Doesn't stop me inventing stories in my head with interstellar travel though

Edit: (M got in whilst I was typing) Yes I agree a Dyson sphere might be extrapolated. However I remain to be convinced that a Dyson sphere could ever realistically be built. But let's not get into that one.

I'm no physicist but I've never heard that the Earth is radiating as much in the as the sun in the radio wavelengths. Do you have a source for that as I would be immensely surprised? Unless it is by surface area in which case the difference in our surface areas would make our contribution negligible. My understanding of the article I quoted above (and other similar articles I have found previously) is that this is the detection range for such emissions from Earth. But I may be wrong.

 

[Michael Colton]

Sadly I agree with you Sodice. However in fairness the Fermi paradox doesn't make the assumption of FTL but without it huge timespans required would leave you feeling why bother? Some unmanned missions for scientific interest possibly but manned? Unlikely I think.

Doesn't stop me inventing stories in my head with interstellar travel though

Well, Karl Schroeder's argument for interstellar travel without FTL is some form of cryonic sleep. That is the entire premise of his new novel which I have yet to read, but somewhere on this site someone posted a link to a recent interview with him about the entire topic. His primary argument was that he finds FTL too implausible for his own fiction at this point, but thinks there are a variety of other possible and much more plausible technological advancements that could make up for it - such as cryonic hibernation throughout the whole trip.

And yes, obviously it does not have to stop writers from utilizing FTL. The further you get away from a contemporary timeline, the less implausible it may feel to the reader. If someone wrote a story about FTL that was set forty years from now, it would feel a bit odd. But three hundred? Five hundred? A thousand? Very easy to suspend disbelief in that case.

 

[Vertigo]

Agreed, but (to be Devil's advocate) if we believe it'll be possible eventually then we come right back to Fermi again where the argument would be that if it is physically possible and there is other life then it has already done... many times.

Although there is still the other worryingly possible answer to Fermi... that all technological civilisation will inevitably destroy themselves either through war or through habitat destruction.

 

[Vertigo]

Sorry for the double post. I just picked this up from SETIs own FAQ pages:

If an extraterrestrial civilization has a SETI project similar to
our own, could they detect signals from Earth?

In general, no. Most earthly transmissions are too weak to be found by
equipment similar to ours at the distance of even the nearest star. But there
are some important exceptions. High-powered radars and the Arecibo broadcast of
1974 (which lasted for only three minutes) could be detected at distances of
tens to hundreds of light-years with a setup similar to our best SETI
experiments.

Unfortunately their last comments are back to that unlikely chance of transmitting in just the right direction at just the right time for some one potentially hundred of years later to be looking in just the right direction at just the right time to see it.

Whole SETI page is here

 

[farntfar]

Essentially SETI is an expression of hope, rather than expectation.

Like many such things the benefits are more likely to be felt by the people that hope than the object of their hopefulness.

 

[Mirannan]

Sadly I agree with you Sodice. However in fairness the Fermi paradox doesn't make the assumption of FTL but without it huge timespans required would leave you feeling why bother? Some unmanned missions for scientific interest possibly but manned? Unlikely I think.

Doesn't stop me inventing stories in my head with interstellar travel though

Edit: (M got in whilst I was typing) Yes I agree a Dyson sphere might be extrapolated. However I remain to be convinced that a Dyson sphere could ever realistically be built. But let's not get into that one.

I'm no physicist but I've never heard that the Earth is radiating as much in the as the sun in the radio wavelengths. Do you have a source for that as I would be immensely surprised? Unless it is by surface area in which case the difference in our surface areas would make our contribution negligible. My understanding of the article I quoted above (and other similar articles I have found previously) is that this is the detection range for such emissions from Earth. But I may be wrong.

That's why I said "Dyson swarm" not "Dyson sphere". The latter implies a solid construct - although Dyson didn't have that in mind. The former does not; it implies a dense swarm of smaller (though still perhaps thousands of kilometres) objects.

The best source I could find is this: http://history.nasa.gov/CP-2156/ch5.4.htm

 

[Venusian Broon]

Sadly I agree with you Sodice. However in fairness the Fermi paradox doesn't make the assumption of FTL but without it huge timespans required would leave you feeling why bother? Some unmanned missions for scientific interest possibly but manned? Unlikely I think.

This is from memory but I believe when Fermi came up with the paradox he has in mind that an alien race would construct "Von Neumann probes" i.e. probes that would 'eternally' fix themselves and also replicate when they came across resources and therefore as it turned out quite effectively cover the entire galaxy. These probes obviously do not care how long they take to get between stars!

When he put in numbers for replication rates and sub-FTL speeds that he thought were plausible (even for the 1950s) the model he had gave him the answer that these probes should have visited every single star in a remarkably short time. (I think we are talking about hundreds, maybe even as low as 10s of millions of years if you have a very aggressive replication rate of these probes for the entire galaxy.)

The black monolith of 2001 is of course be ACC's take on these probes.

 

[Venusian Broon]

And then there's conservation of energy (which works the other way as well - no energy for nothing) so where is the energy for all the matter in these multiverses coming from. It just doesn't add up.

Oh, some theories of the evolution of the universe require total energy to be zero. Essentially Kinetic energy of the big bang explosion (+ve) balances the gravitational energy of all the bits (-ve) etc... Especially if we came from a <cough, cough> false vacuum. (Yes, other theories would have us coming from a false vacuum at a certain vacuum energy, but they are just other theories )

Therefore 'creation' of a new universe in this particular case doesn't violate any energy conservation laws!

BUT - all we know that energy is conserved within our universe - if there is something like a multiverse why should it follow these conditions? And more pertinently how do we test such a hypothesis???

Of course the main reasons that the many-world interpretation of QM is popular are:

1) astrophysicists when applying QM to the entire universe get worried about the Cophenhagen interpretation about 'observers' outside looking in. Many-worlds gets rid of this. (The whole observer thing is a bit woolly and open to terrible abuse IMHO)

2) All these new-fangled theories that do not have a jot of evidence are coming up with a lot of 'multiverses' so they try and tack onto something with a degree of plausibility (except of course there isn't a jot of evidence for many-world either )

3) Perhaps most importantly, it's brilliant for us SF writers