UFOs & Extraterrestrial Life

I'm not very optimistic about either of them. Even if one or both aren't tidally locked, any life would probably evolve no farther than a thin film. I saw a hypothetical view of life on a world twice as massive as Earth, with a surface gravity treble what we experience. There were virtually no flying creatures and animals needed six legs instead of four... Imagine life on a world almost eight times as massive as ours...

The observations we have are skewed by the method used to detect these extra-solar planets. Earth sized planets are much
harder to find compared to 2x Earth size and larger. So we have more of these large "Earth" observations. They do not mean
anything. Since we have established that there is a rich spectrum of planetary systems, it would be unphysical if Earth sized
and smaller were not available in large numbers. You never hear about 1/2 Earth size planets because the current method
and instrument accuracy can't detect them. But they must exist.

Back in the 1980s, it was not clear at all that so many Earth range planets were out there and the Star Trek universe looked
contrived. Now, it is no longer an obscure issue. There is a vast number of Earth-sized (i.e. within 10% not 100%) planets
out there. And they are basically guaranteed to have water unless they are pathological like Venus. Venus got screwed up
by most likely a large impact that left its axis of rotation almost parallel to the orbital plane and left its rotation to be much
weaker than that of Earth. If you look at Jupiter, Mars and Earth, they all have a 24-25 hour rotation rate. That is a characteristic
feature of planetary formation for our star. Venus should have had a similar rotation rate and its axis of rotation should have
been perpendicular to the orbital plane accounting for the wobbling that you normally find. Thus, "M class" planets really
do exist in vast numbers. That leaves only life formation and development of intelligent life and civilizations as the uncertain
variables. Unlike Star Trek, there is likely to be no endless availability of humanoid civilizations on these Earth-like worlds.
Most of them probably do not have intelligent (as in civilization-forming) life.

But given the enormous number of Earth-like planets, even if only a small probability of intelligent life exists on them, then
that implies tens of thousands or higher order of such planets. Then we have the distribution of advanced civilizations and more
primitive ones. The likelihood of Earth-type civilizations is not 100% and we probably are down to hundreds of actual instances.
The number of sci-fi utopias among them is basically zero. All of the civilizations will be subject to the same physics and
are guaranteed to have exploited carbon fossil fuels just like humans. All of these Earth-type planets will have fossil fuel
resources since they are generic due to life and solar energy (oil, gas and coal are sources of fossilized sunshine). So it
is highly probable that most advanced civilizations off themselves in the fashion humans are doing, i.e. via thermal death
through CO2 pollution. Some of them may see the light earlier and transition to nuclear (including ultimately fusion), but
these will number in the handful.

So the reason we have no signals from aliens, is because the ones even capable of sending them are few and thus
scattered over a vast volume and hence too far (1/r^2 attenuation of EM signal with distance). They are probably not
building any enormous signal generators to attract our attention just like we are not building any such devices. And
any advanced civilization will not waste energy in a fashion that would broadcast its existence to the whole universe.

They are out there regardless of our ability to detect them. But their numbers are very small which is why we cannot
detect them.

So we have more of these large "Earth" observations. They do not mean anything.

Super earths may have earth-size moons with right conditions for life.
There may be a lot more advanced civilizations that been using different ways to communicate for 100s/Ks of years that we still can't detect. Also, they may scramble their radio signals to sound like natural radiation so only certain recipients can decode them.

kvs wrote:Venus got screwed up
by most likely a large impact that left its axis of rotation almost parallel to the orbital plane and left its rotation to be much
weaker than that of Earth.

Receiving almost twice as much insolation as Earth may have made a runaway greenhouse effect inevitable.

 Venus should have had a similar rotation rate and its axis of rotation should have
been perpendicular to the orbital plane accounting for the wobbling that you normally find.

At its distance from sol, tidal dissipation was another issue.

So it
is highly probable that most advanced civilizations off themselves in the fashion humans are doing, i.e. via thermal death
through CO2 pollution.

Smacks of temporocentrism. Mirroring the Cold War, Sagan thought many civilizations destroy themselves in nuclear wars.

Some of them may see the light earlier and transition to nuclear (including ultimately fusion), but these will number in the handful.

I don't doubt there will be grave crises due to global warming and other issues. But I've long opined the ultimate casualty will be democracy not civilization.  It's not that solutions are lacking it's just that people tend to resist them, as they involve sacrifices. Present government is obsolete and will go.

So the reason we have no signals from aliens, is because the ones even capable of sending them are few and thus
They are out there regardless of our ability to detect them.   But their numbers are very small which is why we cannot
detect them.  

The number of independently evolved civilizations is indeed small, I suggest only 100 or so in the whole galaxy. But many of these could've spread. We're mere beginners; others may have been spacefarers for millennia, maybe eons. I think ET has been here a long time.

GarryB wrote:
.. higher gravity means denser gases surrounding the planet and denser gases are easier to fly through...

Na, a denser medium is harder to move through, more resistance.

Imagine a creature that has an enormous sac like Portuguese man o' war jellyfish that produces light gases from the food it eats perhaps that can float around like a balloon in the thick atmosphere...

What does it eat up there? To my knowledge there are no analogues in our atmosphere. Higher gravity isn't favorable to true flight because it takes more energy to become airborne and stay that way.

https://books.google.com/books?id=NvI0AgAAQBAJ&pg=PA146&lpg=PA146&dq=life+in+universe+may+be+common+david+j+eicher&source=bl&ots=uEx3s4yaoQ&sig=ACfU3U3iaiROPidyB4XD9RBIgUGrdc8DLg&hl=ru&sa=X&ved=2ahUKEwiUvrjQ_8DoAhULqp4KHRHzCr0Q6AEwCXoECAoQAQ#v=onepage&q=life%20in%20universe%20may%20be%20common%20david%20j%20eicher&f=false

Ancient fossil microorganisms indicate that life in the universe is common

https://earthsky.org/space/ancient-microorganisms-fossils-life-common-universe

https://www.discovermagazine.com/the-sciences/life-in-the-universe-is-common-oldest-fossils-on-earth-suggest

http://www.sci-news.com/paleontology/simple-life-forms-common-universe-05549.html

https://www.huffingtonpost.co.uk/entry/fossil-could-be-proof-that-life-in-the-universe-is-actually-common_uk_5a3a32eee4b025f99e135190?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAH_7WvA4m0uflTrreFFlnfGxe4hMvIcmnjiZjNVqln_Fpjm7BCe7OYxyuEUNPysuFAs8FRNl0ngYkXYgROTKCpfkR15E5QqCV8kFPu4dQTKYgJ6iwqZoMdKX_vf1mKU33IlKwbXeqC6-qJ4BYtnAufgLvMAYNax7REdQB40nJlRY

https://www.space.com/life-spread-around-galaxy-panspermia.html

https://www.space.com/18790-habitable-exoplanets-catalog-photos.html

Tsavo Lion wrote:
There may be a lot more advanced civilizations that been using different ways to communicate for 100s/Ks of years that we still can't detect.

Not sure if this can be true because a more advanced civilization would realize that people on Earth will not be able to decipher their signals. So they would have communicated in a way humans understood.

The opposite is also true. Even if humans would have tried to reach out to them my sending out message that would be considered primitive in their world, being an advanced civilization they would have been able to decipher it.

They been here for Ks of years to influence our civilization; but to them, we r not ready for direct overt official contact at this time, since Earthlings r still fighting each other & have too much ego.

Most, if not all, of very advanced civilizations would survive long enough w/o going suicidal, & will migrate to other planets if need be. They would form an intergalactic communities to settle disputes, deal with primitive civilizations, exploration, cosmic/planetary cataclysms, & help each other.
The Earth would become uninhabitable in a few M years, if not earlier, anyway as the Sun becomes hotter; there r plenty of other planets with better living conditions- if they can reach us, those planets could be reached too.

Tsavo Lion wrote:They been here for Ks of years to influence our civilization; but to them, we r not ready for direct overt official contact at this time, since Earthlings r still fighting each other & have too much ego.

Even if Earthlings are fighting among themselves and have a huge ego, why are these two aspects seen as detrimental by aliens in order to make contact?

Because making a contact will do more harm than good- we need to solve our problems themselves & grow from that experience; besides, the aliens have their own problems & don't need anything extra.

They already kidnapped scores of people & know our DNA, diseases & pathogenes enough to protect themselves.

I would assume that they already have encountered & contacted many other life forms long before us & survived their bacteria & viruses alien to them, & had enough time to study Earth's biology to equip themselves with adequate protection.
The "War of the Worlds" by G. Wells won't happen.
https://www.gutenberg.org/files/36/36-h/36-h.htm

GarryB wrote:... In a very dense atmosphere... like Jupiter... the life form might seek sunlight for photosynthesis,

Doubtful. At Jupiter's distance insolation is a tiny fraction of what we receive. And unless the organism is at the top of the atmosphere, it would be reduced even further.

Tsavo Lion wrote:They already kidnapped scores of people & know our DNA, diseases & pathogenes enough to protect themselves.

I doubt there's any need for such protection. Although reported humanoids tend to appear biological, I would assume they're a form of advanced AI/robots. That way they're immune not only to pathogens but calcium loss in low gravity, and probably other issues.

Tsavo Lion wrote:
The "War of the Worlds" by G. Wells won't happen.

Of course not. The '53 movie was good in some ways but the ending was ridiculous, in more ways than one...

The show stopper for inter-stellar travel is the speed of light. That is why sci-fi comes up with deus ex machina solutions such as
warp drive or wormholes or hyperspace or any cheat to defeat the speed of light barrier.

Unlike the speed of sound, the speed of light is a barrier that cannot be crossed. Massive particles cannot be accelerated to and
past the speed of light since it takes an infinite amount of energy to push v -> c. (Put another way, the ability to accelerate to
c goes to zero as v -> c.) And at the speed of light, the mass is converted into photons if one could magically get v=c. Those
photons do not interact to maintain whatever mass was there before (spaceship, human, air). So reaching v=c means dissociating
into a photon gas.

Traveling at some v close to c means that every atom or dust particle that collides with the space ship is catastrophic. Even in
the "vacuum" of space the spaceship will ablate away.

So there is a good reason we have no anal probing alien visitors and can't even pick up EM signals from distant civilizations.

kvs wrote:
So there is a good reason we have no anal probing alien visitors and can't even pick up EM signals from distant civilizations.  

If legions of witnesses have been reporting UFOs and occupants for several decades, and there's some physical evidence, I think our present understanding of physics ought to be called into question instead of UFOlogy or ET. SETI btw always struck me as a poor approach. Considering we're mere beginners where civilization has existed only a few thousand years, it's silly to dismiss ET because there's little/no evidence he communicates like we do.