Shouldn't we have heard alien radio signals by now? Why not?

[SeventhSigma]

I figure that intelligent life couldn't have formed until, at the very least, the second generation stars that started birthing forth carbon (maybe 3 billion years after the Big Bang?). On Earth, it took something like 2.5 billion years until multicellular life formed, and so maybe we can estimate that intelligent civilizations didn't start popping up until ~7 billion years after the Big Bang.

If this is true, that may imply that radio signals from these intelligent civilizations may have been traveling for ~7 billion years or so prior to today. Shouldn't that be a decent stretch across the cosmos -- about half of our cosmic horizon?

Do you think radio signals are "weakened" to the point where we can't detect them? Is it possible that intelligent life couldn't have formed until much later in the game despite the carbon influxes? Do you think it's some other reason? Let me know your thoughts!

 

[Antiphon]

I think that there is a very short window for a civilization, maybe only 5000 years between the time it starts broadcasting radio signals and the time its technology becomes so advanced that they no longer broadcast high power RF signals.

This leaves only the possibility that they are deliberately sending signals for another civilization to pick up. I find this very unlikely due to the inherent danger in the uncontrolled contact between civilizations of widely differing technology.

 

[Chronos]

Other issues - how many radio capable [and utilizing] civilizations overlap? How many have the means and desire to transmit sufficiently powerful radio signals during the overlap period? I don't think intelligent civilizations are necessarily unique, just that they rapidly pass through the radio era of communication. I think they are sufficiently rare that funding for sufficiently powerful ET radio studies have a very tiny window.

 

[nicksauce]

Do you think radio signals are "weakened" to the point where we can't detect them?

Yes, of course. Think about how hard it is to see an individual star in a nearby galaxy. Now compare the power output of such a star to the power output of a typical radio transmitter that an intelligent civilization might have. It is pretty much unthinkable that we would ever get ET signals from outside of our galaxy, let alone, from billions of light years away.

 

[phyzguy]

Try googling the "Fermi paradox". Basically Fermi asked the same question - "If intelligent life is common, then where are they?" The simple answer is that we don't know. Maybe intelligent life is extremely rare. Maybe intelligent life destroys itself after a short time. Maybe (this is Hawking's recent point) there are predators out there and any civilization that makes "noise" gets quickly found and snuffed out or enslaved. Maybe energetic events like gamma ray bursts periodically sterilize the galaxy. Maybe... We simply don't know yet.

 

[Radrook]

Some believe that the WOW-Signal constituted the necessary evidence to conclude that there are other civilizations out there. Unfortunately, that signal was not sustained and finding it again by scanning that same section of the universe has proven fruitless. Some have said that we might have just listened in a brief ship-to-ship communication. Others a distress signal that was heeded and needed no repetition. Still others say that we don't listen long enough and their transmission schedule might not coincide with our listening one. In any case the signal was impressive enough to warrant a big WOW written next to it and it has referred to by that ever since.

 

[Rasalhague]

I got some good replies to a related question:

https://www.physicsforums.com/showthread.php?t=374799

 

[cmarrou]

Those who believe radio communication is a temporary development are likely correct. It was barely a century ago that Marconi first sent his three-dot "S"s into the void. Radio and television broadcasting work well for sending content from the few to the many, but today people want more give-and-take. Most TV is now received through shielded coaxial cables, and radio is rapidly becoming outdated through satellite broadcasts that are aimed down at the Earth, not from it into space. In another twenty years or so, we are unlikely to have much of a radio wave signal to show the universe, so, figuring maybe 150 years out of 7 billion for use of radio waves, perhaps one in 50,000,000 planets with intelligent life would show some radio profile. Then again, maybe radio was developed here because we missed the development of greeblatz or some other alternative technology that sends nothing at all skyward. Woe is us!

 

[Vanadium 50]

Despite mentor warnings, this thread was getting side-tracked into a non-scientific direction. Those messages have been removed.

I think people are missing something. It is completely plausible that a society will use less and less radio for communications, for all the obvious reasons. However, SETI doesn't have to just look for radio - it also looks for radar. Radar has many advantages. A putative civilization would like some advance notice of nearby asteroids that might collide with them. It's high power. It's aimed up in the sky. It's likely to be reasonably regular and thus easy to spot.

 

[Rasalhague]

The article Chronos mentioned in the thread I linked to has some interesting comments on high intensity narrowband radar, as the one kind of signal our civilisation makes which a civilisation of equivalent technological development could be reasonably expected to detect.

https://www.physicsforums.com/showpost.php?p=2564759&postcount=5
http://www.faqs.org/faqs/astronomy/faq/part6/section-12.html]

 

[PacketMan]

The other question is how much of a sample have we really been able to take so far? We've been looking for what, 50 years? I saw an astrophysicist on some program on the Science Channel put it very well: If you dipped a glass of water in the ocean and looked it at, would you conclude that the ocean has no fish in it?

 

[ThomasEdison]

I figure that intelligent life couldn't have formed until, at the very least, the second generation stars that started birthing forth carbon (maybe 3 billion years after the Big Bang?). On Earth, it took something like 2.5 billion years until multicellular life formed, and so maybe we can estimate that intelligent civilizations didn't start popping up until ~7 billion years after the Big Bang.

If this is true, that may imply that radio signals from these intelligent civilizations may have been traveling for ~7 billion years or so prior to today. Shouldn't that be a decent stretch across the cosmos -- about half of our cosmic horizon?

Do you think radio signals are "weakened" to the point where we can't detect them? Is it possible that intelligent life couldn't have formed until much later in the game despite the carbon influxes? Do you think it's some other reason? Let me know your thoughts!

Are you sure about fully developed civilizations being possible as far back as 7 billion years ago?

So you mean a modern type solar system at least 10 billion years old because I can only assume it would take a few billion years to form a civilization from a rocky world.

That seems like a very broad window.



EDIT:
Can someone who is well versed in Astronomy confirm or deny the plausibility of modern (extra)solar systems existing that far back? Modern =A long lived yellow to red sun with rocky bodies made of heavy elements orbiting it. How far back was this even possible?

If we truly want to approach this question shouldn't we start there?

What exactly is the timeline window for the development of solar systems and life on them?

 

[GODISMYSHADOW]

Shouldn't we have heard alien radio signals by now? Why not?

Maybe we did, but the source LGM-1 was later downgraded and written off as being a rotating neutron star.

 

[tasp77]

We are first.

 

[Ryan_m_b]

We are first.

Care to clarify any reasoning behind this?

 

[drollere]

Can someone who is well versed in Astronomy confirm or deny the plausibility of modern (extra)solar systems existing that far back? Modern =A long lived yellow to red sun with rocky bodies made of heavy elements orbiting it. How far back was this even possible?

If we truly want to approach this question shouldn't we start there?

What exactly is the timeline window for the development of solar systems and life on them?

supermassive stars appear to have formed relatively early in the history of the universe (around 13 billion years ago, more or less) and would have very rapidly (within a million years or so) begun spewing out heavier elements.

life on our planet evolved within 1 billion years after the formation of the earth, if not earlier.

the crux here is that there are uncountably more explanations for why something has *not* happened than for why it *has* happened.

surely the inverse square law of radiation, and the sheer scale of the universe, and the disparity between energy requirements and practical motivation, suggests that at some point there is a horizon on the signals one might receive from an advanced civilization elsewhere in our galaxy.

but because i choose something that appears relatively more plausible as a piece of the scheme of things does not mitigate the problem. I'm still dabbling with the toy of my ignorance ... or i work for the SETI foundation.

 

[tasp77]

Care to clarify any reasoning behind this?

Consistent with data we have on hand,


+


being first has to happen to some civilization, mighty profound if it be us.

 

[Ryan_m_b]

Consistent with data we have on hand,
+
being first has to happen to some civilization, mighty profound if it be us.

Absence of evidence is not evidence of absence. You are making a fallacious statement when you claim that we are first.

 

[Orion1]

https://www.youtube.com/watch?v=17jymDn0W6U
Most humans underestimate the vastness of space-time.

Watch this video and pay close attention to time index 2:35 to 2:49, the extent of humanity's first radio signals to scale with the Milky Way galaxy. This should provide some indication as to just how difficult it is to detect an artificial transmission, even within our own galaxy, let alone any artificial transmission from another galaxy.
[/Color]
Reference:
http://www.youtube.com/watch?v=17jymDn0W6U"

 

[Ryan_m_b]

https://www.youtube.com/watch?v=17jymDn0W6U
Most humans underestimate the vastness of space-time.

Watch this video and pay close attention to time index 2:35 to 2:49, the extent of humanity's first radio signals to scale with the Milky Way galaxy. This should provide some indication as to just how difficult it is to detect an artificial transmission, even within our own galaxy, let alone any artificial transmission from another galaxy.
[/Color]
Reference:
http://www.youtube.com/watch?v=17jymDn0W6U"

Very cool! Can anybody tell me the reason as to why the areas of the universe we have mapped extend from Earth in a sort of double fan shape rather than a sphere?

 

[Orion1]

https://www.youtube.com/watch?v=c64Aia4XE1Y

Can anybody tell me the reason as to why the areas of the universe we have mapped extend from Earth in a sort of double fan shape rather than a sphere?

Watch the TED lecture by astrophysicist George Smoot. The short answer is that this is the limit of the present galaxy sky survey data which must be mapped and cataloged.
[/Color]
Reference:
http://www.youtube.com/watch?v=c64Aia4XE1Y"

 

[Ryan_m_b]

Watch the TED lecture by astrophysicist George Smoot. The short answer is that this is the limit of the present galaxy sky survey data which must be mapped and cataloged.
[/Color]
Reference:
http://www.youtube.com/watch?v=c64Aia4XE1Y"

Very interesting. Thanks

 

[Drakkith]

Watch the TED lecture by astrophysicist George Smoot. The short answer is that this is the limit of the present galaxy sky survey data which must be mapped and cataloged.
[/Color]

That was awesome!

 

[Flustered]

Do all intelligent civilizations evolve like we do? Do they all go through the same technology advances we do? What if another life form, had technology in totally different ways than humans, but they were still type 0 or 1 civilizations like us? Is it possible for life forms on the other side of the universe to have different elements and particles from us? Could their periodical table have more elements?

 

[Flustered]

Also could someone elaborate on the this question.
I once heard that not every galaxy can even harbor life, my teacher told me that only spiral galaxies can have life. Other galaxies cannot have life because they are not spinning there for new stars are not being born, or something to that extent.

 

[DaveC426913]

Do all intelligent civilizations evolve like we do? Do they all go through the same technology advances we do?

We don't know.

Probably there are some considerable differences, but we kind of assume a certain amount of convergent evolution in both biology and technology. (Not the kind that leads to bipedal axial symmetry, but the kind that leads to physical multi-cellular bodies with sensors, organs and brains, as well as a desire to observe the "thousand point of light" in the night sky.)

Is it possible for life forms on the other side of the universe to have different elements and particles from us?

They might be made of different elements than us, though those elements will still be from our periodic table

Could their periodical table have more elements?

No.

I once heard that not every galaxy can even harbor life, my teacher told me that only spiral galaxies can have life. Other galaxies cannot have life because they are not spinning there for new stars are not being born, or something to that extent.

meh.

There are arguments that they may harbor less life than life as we know it, but it's pretty speculative.

 

[Ryan_m_b]

Do all intelligent civilizations evolve like we do? Do they all go through the same technology advances we do?

Evolutionary processes are the same whether or not it is life in the Earth's oceans or dots on a simulator but that doesn't mean they have to be anything like us physically or socially (beyond the need to be able to reproduce with variation to evolve and have the faculties to innovate and build/use tools).

There's little reason to believe that they will have the same technology though they may develop similar solutions to similar problems. It all depends on what natural and social problems they attempt to overcome, what resources they have to do it and what their psychology and culture permit.

This is speculation (albeit logical) and doesn't really mean much until we have more than one tool-using species that we would judge equivalently intelligent to compare ourselves with.

 

[Flustered]

Evolutionary processes are the same whether or not it is life in the Earth's oceans or dots on a simulator but that doesn't mean they have to be anything like us physically or socially (beyond the need to be able to reproduce with variation to evolve and have the faculties to innovate and build/use tools).

There's little reason to believe that they will have the same technology though they may develop similar solutions to similar problems. It all depends on what natural and social problems they attempt to overcome, what resources they have to do it and what their psychology and culture permit.

This is speculation (albeit logical) and doesn't really mean much until we have more than one tool-using species that we would judge equivalently intelligent to compare ourselves with.

Is it a given that a type 1 civilization can only get there if math is involved, math is a big part of physics and what not. Is it possible for a civilization to get farther than us without math? Also would they have the same concepts as us? Would they need to use negative numbers like we do? Could they advance farther without language?

Michio Kaku was saying that star wars would be a type 3 civilization, is it even possible for all those different life forms to be living in the same galaxy at the same time and fighting one another. I know it is SCI FY but what are the chances? Also Kaku was talking about civilizations taking all of their power from the stars, how would a civilization begin to take solar power from all the visible stars and use it?

 

[Ryan_m_b]

Is it a given that a type 1 civilization can only get there if math is involved, math is a big part of physics and what not. Is it possible for a civilization to get farther than us without math? Also would they have the same concepts as us? Would they need to use negative numbers like we do? Could they advance farther without language?

Michio Kaku was saying that star wars would be a type 3 civilization, is it even possible for all those different life forms to be living in the same galaxy at the same time and fighting one another. I know it is SCI FY but what are the chances? Also Kaku was talking about civilizations taking all of their power from the stars, how would a civilization begin to take solar power from all the visible stars and use it?

The kardashev scale isn't a scientific proposition, it's an idea that doesn't entirely make much sense. The idea being that type 2s have the capability to build Dyson spheres and a type 3 simply does this to all stars in the galaxy, but there is no reason to think that there is an absolute path that a tool-using, sentient race would follow this scale. Regarding mathematics it would be pretty important, you can't produce any good science, economics or even politics without it and it would most likely be similar.

 

[Flustered]

Off topic//

Our all galaxies the same age? And has any galaxies that we know of, started to "die" or are "dead".

 

[Flustered]

https://www.youtube.com/watch?v=c64Aia4XE1Y


Watch the TED lecture by astrophysicist George Smoot. The short answer is that this is the limit of the present galaxy sky survey data which must be mapped and cataloged.
[/Color]
Reference:
George Smoot: The design of the Universe

Problems with this video, how can we map 360 degrees the CMB, but not 360 degrees of all the galaxies in the universe?

He also didn't explain what in our galaxy is blocking us from mapping the voids, nor did he explain why telescopes can't do it either.

He also said our galaxy is on the "boonies" not at the CENTER of the universe, he was implying that there is a center of the universe, he said it as clear as day.

In another thread, everyone is saying there is no center, but he said different.

 

[Flustered]

Is there a connection between the formation of galaxy superclusters, and the human brain cells. They look a lot alike.

 

[DaveC426913]

Off topic//
Our all galaxies the same age? And has any galaxies that we know of, started to "die" or are "dead".

All galaxies are not the same age, no. But galaxies won't really die. Galaxies are just collections of stars. I suppose in principle a galaxy could be composed of nothing but dead stars...

Is there a connection between the formation of galaxy superclusters, and the human brain cells. They look a lot alike.

No. Not in any but the most basic ways in mechanics of shapes. (A bubble and a star are both spherical but only because they are both comprised of competing symmetrical inward and outward forces).

 

[Drakkith]

Problems with this video, how can we map 360 degrees the CMB, but not 360 degrees of all the galaxies in the universe?

He also didn't explain what in our galaxy is blocking us from mapping the voids, nor did he explain why telescopes can't do it either.

The CMB is a much longer wavelength than visible and infrared light and is able to penetrate through large sections of our galaxy to be seen, whereas most of the visible light is blocked by dust. It is also very very smooth and is fairly easy to capture a large portion of the sky. In contrast, the vast majority of galaxies require a very high magnification and multiple hours of exposure time to see properly. This puts constraints on how much we can map with the few telescopes we have that can even see them. As an example, consider the Hubble Deep Field and Hubble Ultra Deep Field images. They requires DAYS of exposure time just to capture a very very small area of the sky.

He also said our galaxy is on the "boonies" not at the CENTER of the universe, he was implying that there is a center of the universe, he said it as clear as day.

If you go to the video again, you can see that he said we were not at the center of our Solar System, Galaxy, and Cluster, not universe.

 

[Wanderlust]

Several Speculative Scenarios

There are no active civilizations within a few tens of thousands of light years. Active being functional and broadcasting for at least a hundred thousand years time. [radius of the galaxy]

There are no civilizations active within a hundred thousand years in time, don't forget we are separated in time as much as space. There is only a 100,000 year window of detection after a civilizations stops broadcasting in one wavelength

All current active advanced civilizations use different communication systems than we do, perhaps ones we have not thought of. Maybe other frequencies or other ideas we have not tried

We are the first civilization to emerge and activate in the galaxy

We are alone in the galaxy

Communication methods fade into the cosmic background after a distance. (most likely, stuff fades out as distances get larger) You need power to go long.

We are not trying hard enough [money]

 

[epenguin]

We are first.

Some people (i.e. this astronomer I heard in a meeting about 12 years ago) think we are last - we arrived when the party is nearly over.

 

[Ryan_m_b]

There are no civilizations active within a hundred thousand years in time, don't forget we are separated in time as much as space. There is only a 100,000 year window of detection after a civilizations stops broadcasting in one wavelength

I think this is a key point that is often forgotten in science fiction (unless you read hard-SF). Humans/the Homo genus evolved to the point where they could communicate and use tools to the sophistication we see today over the last few hundred-thousand to million years (depending on whether or not you consider the capabilities of other species of human). However we only started to organise into non-nomadic communities in the last ten-thousand years. There is little reason why a species with these attributes couldn't have evolved at any point since the Cambrian explosion but that is just how things have gone. It would seem an extraordinary coincidence if we were to identify an alien species whose history was the same length as us and who were at roughly an equal level of technology. More likely the separation would be measured in mega years.

 

[TGlad]

"Shouldn't we have heard alien radio signals by now? Why not?"
Because you have many hidden assumptions that are probably false:
1. That aliens want or need to communicate with us.
The vast likelihood is that they are either way behind us (they are sponges, fish etc) or way ahead of us, in which case we are not of slightest interest to them.
2. That stray alien signals would be easy to pick up.
Even human signals are tending more and more towards something that looks like white noise. Why? because white noise contains the most information. White noise is also almost impossible to interpret for patterns by its very definition.
3. That signals would leak to earth.
If aliens were speaking to each other, broadcasts in all directions would be massively inefficient so wouldn't be used
4. That we are the peak and the future of evolution.
We arrogantly consider ourselves the 'best' animals, but maybe we are just an oddity that over-populates, sucks all the oil then dies out, with rodents the most common animal over time. The long term future may look much like the past, different animals, different plants coming and going.

I expect our discoveries in future will come mainly from simulations, rather than trying to set up conversations with aliens with a lag time of thousands of years. So if we aren't likely to be making such conversations, we shouldn't expect ET to be doing that either.

 

[DaveC426913]

4. That we are the peak and the future of evolution.
We arrogantly consider ourselves the 'best' animals,

No we don't. We simply recognize that, as an animal with
1] the capacity for foresight, and
2] the tools to do something about it,
we are capable of guiding - and thus preserving - our own destiny.

Like evolution, it inevitably leads to greater prosperity - unless something goes terribly wrong (which is a failure not a natural progression).

I expect our discoveries in future will come mainly from simulations,

I think it was Aristotle that made that profound error - the conviction that we can learn all there is to learn from logic alone, that going out and observing - seeking new (and specifically, unexpected) information - is unnecessary. He was wrong.

"Aristotle understood that logic can be used to deduce true consequences from true premises. His error was his failure to realize that we have no absolutely true premises, except ones we define to be true."

 

[Wanderlust]

in which case we are not of slightest interest to them.

Ameobas are interesting. You don't realize that groups of people have specialists. I am not interested at all in a new species of slug in borneo, but some people are passionate about it. Some individuals in that society may have a keen interest in new sapient civlizations.

3. That signals would leak to earth.
If aliens were speaking to each other, broadcasts in all directions would be massively inefficient so wouldn't be used

Good idea, haven't though of this one before.

 

[Radrook]

The article Chronos mentioned in the thread I linked to has some interesting comments on high intensity narrowband radar, as the one kind of signal our civilisation makes which a civilisation of equivalent technological development could be reasonably expected to detect.

https://www.physicsforums.com/showpost.php?p=2564759&postcount=5
http://www.faqs.org/faqs/astronomy/faq/part6/section-12.html]

That's assuming the same types of psychological needs and motivations of course.

 

[Ryan_m_b]

Ameobas are interesting. You don't realize that groups of people have specialists. I am not interested at all in a new species of slug in borneo, but some people are passionate about it. Some individuals in that society may have a keen interest in new sapient civlizations.

More than that looking at simple life would be intensely fascinating to any biologist, especially biochemists, microbiologists and any branch of evolutionary biology. If the ameoba were to use something other than water as a solvent and biochemistry not based on amino acids, nucleotides or carbohydrates (or even not based on carbon) that would be fantastically interesting.

 

[Radrook]

The other question is how much of a sample have we really been able to take so far? We've been looking for what, 50 years? I saw an astrophysicist on some program on the Science Channel put it very well: If you dipped a glass of water in the ocean and looked it at, would you conclude that the ocean has no fish in it?

That's an excellent analogy which becomes even more compelling if we hypothetically add the possibilities of life inherent in the dimensional or multiple universes ideas that physicists are currently tossing around.

 

[Ryan_m_b]

That's an excellent analogy which becomes even more compelling if we hypothetically add the possibilities of life inherent in the dimensional or multiple universes ideas that physicists are currently tossing around.

Firstly you are using the term dimension wrong here. Secondly no theory involving a multiverse involves the capability to transfer from one to the other. It's easier to keep it within the realm of known physics in the known universe.

Not that it wouldn't be interesting to view life under different physical laws but a bit moot.

 

[D H]

Secondly no theory involving a multiverse involves the capability to transfer from one to the other.

Ahem.

I don't know about you, but I take umbrage when someone describes evolution as "only a theory." The lay community uses the term "theory" to mean "some crazy idea I had when I woke up at 3 AM thanks having eaten a bad batch of seafood." Science views the term differently. Scientific theories are the pinnacle of scientific knowledge.

Let me correct that statement of yours, if you don't mind.

Secondly no [strike]theory[/strike] conjecture involving a multiverse involves the capability to transfer from one to the other.​

Sorry for the derailment. Go on back to discussing why we haven't heard alien radio signals by now.

 

[Ryan_m_b]

Let me correct that statement of yours, if you don't mind.

No problem, you're dead right. I put it down to a slip of the tongue/hand.

 

[Radrook]

Firstly you are using the term dimension wrong here. Secondly no theory involving a multiverse involves the capability to transfer from one to the other. It's easier to keep it within the realm of known physics in the known universe.

Not that it wouldn't be interesting to view life under different physical laws but a bit moot.

Firstly you are using the term dimension wrong here.

Really? How? Strange since I didn't go into a detailed definition of what I think the term "dimension" means.

Secondly no theory involving a multiverse involves the capability to transfer from one to the other.

Please show me where I made that ridiculous claim.

It's easier to keep it within the realm of known physics in the known universe.

Please show me where I said it wasn't.

Not that it wouldn't be interesting to view life under different physical laws but a bit moot.

Well, it might seem moot if we understand it in a certain irrelevant way and not as intended. The point is that life is life whether we can communicate with it or not and whether it is within our dimension or not but still extraterrestrial or out there somewhere in the general direction where our telescopes are aimed.

Any claim that extraterrestrial life doesn’t exist based on our meager attempts to detect it would be ludicrous. But it would be even more ludicrous when the possibility of multiuniverses and extra dimensions where life might be present, as physicists are currently theorizing, is taken into account. It is such a claim that I was commenting on as I clearly pointed out.

Brane cosmology

String theorists like Neil Turok, Burt Ovrut and Paul Steinhardt discuss the idea that there are no more or fewer than 11 dimensions. These structures, membranes, exist across all these dimensions. Presumably, the one dimension of time and other ten dimensions of spaces have always existed. The physicists suggest that our universe may have formed when two extra-dimensional membranes collided. On this conception, our universe may not be so special, since membrane collisions could cause big bangs all the time. The result is a sort of multiverse - with universes acting like bubbles that generally cannot interact with one another. These ideas have implications for Cosmogony.[1]
http://en.wikipedia.org/wiki/Brane_cosmology

Parallel Universes Videos


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Who lives in the eleventh dimension Video
http://www.youtube.com/watch?v=xE7xRgfPjAI&feature=related

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[Ryan_m_b]

Really? How? Strange since I didn't go into a detailed definition of what I think the term dimension means.

No but the way you are using the term is wrong; only colloquially is dimension synonymous with universe.

Please show me where I made that ridiculous claim.
Please show me where I said it wasn't.

I never suggested you did. My point was that talking about life in other universes is a pointless exercise because 1) we can't be sure that such universes exist and 2) even if they did we could never expect to hear from them anyway. As this thread is about detection bringing something to the conversation that cannot be detected won't get us anywhere.

Well, it might seem moot if we understand it in a certain irrelevant way and not as intended. The pint is that
life is life whether we can communicate with it or not and whether it is within our dimension or not.
Our claim that no extraterrestrial life doesn’t exist based on our meager attempts to detect it would be ludicrous. It would be even ludicrous when we consider the possibility of multiuniverses and extra dimensions where life might be present is taken into account. It is such a claim that I was commenting on as I clearly pointed out.

Again only colloquially is dimension used to mean universe.

Parallel Universes Videos...

Popular science documentaries are not supportive evidence.

 

[SeventhSigma]

Part of me worries that intelligent life is just so rare, even when taking into account the countless number of planet types/star systems/etc that would be conducive to it.

 

[micromass]

Really? How? Strange since I didn't go into a detailed definition of what I think the term "dimension" means.

The term dimension has nothing to do with parallel universes. We often see in science-fiction shows that "people have been transported to other dimensions", like tey have went to another universe where the laws of physics are different.

The term dimension has absolutely nothing to do with this. Dimension has a very precise mathematical meaning. A dimension actually is "the number of free variables possible in a system". For example, the plane has dimension 2 since you need 2 variables to specifically determine a point in the plane (indeed: you need an x and a y-variable). The space has dimension 3 since you need 3 variables.

So a dimension is not a parallel universe, it is simply a number!

In physics, a dimension has a related but different meaning. A dimension there can be used to signify whatever units we use. For example, accelaration has units m/s^2 and has a different dimension than velocity which has units m/s.
Again, there is no talk about parallel universes.

If you want to talk about parallel universes, you are welcome to do so: but do NOT use the term dimension.