1 hour ago, Fielder said:

How many times do you have to jump off the roof to test the reality of gravity before you believe the results? How many thousands of times do you observe experimental results before accepting the evidence that alien contact is almost surely not going to happen?

 

Yep, as I've spoken about before on the forum, there's the Drake Equation that suggests that the galaxy should contain numerous technologically advanced species but then there's the Fermi Paradox that asks, where are they? Given the age of the universe, all it would take is for one species to survive "the great filter" (which you allude to later in your post) and then even at the velocities we are capable of now, that species would be capable of colonizing the Galaxy in a mere two million years. And yet, we see nothing, no Von Neuman probes, no large scale mega structures, no radio frequency communications. 

 

1 hour ago, Fielder said:

Because as knowledge increases asymptotically, some one evil thing is almost sure to spiral beyond control. The first virus grown artificially in non human tissue was done in about 1950. The faster we accelerate knowledge, the number of and the danger from global threats increase alarmingly.

 

The so called "great filter". The question is where that "great filter" lies. If the great filter lies at or ahead of our level of technological development, then you would expect at least ONE of the numerous advanced species predicted by the Drake Equation to have avoided such an extinction event and gone on to colonise the galaxy in the two million year time frame suggested as feasible for such an endeavour.  But we see nothing. Is it really feasible that NONE survive the great filter? 

 

1 hour ago, Fielder said:

It seems that surely some of the hypothetical other civilizations would perhaps have had say a ten million year head start on our civilization. Time enough to have learned to escape the bounds of time, speed, and space to penetrate the vast continuum which we ourselves cannot. But still, they are not here. And I believe it extremely unlikely that they will be, say in the next ten thousand years. And we will not likely be there. I doubt we will be here either.

 

Way more than a ten million year head start. The universe is 13.8 billion years old. But yes, Fermi hit the nail on the head, a paradox is certainly is. 

Although there are explanations for the paradox and quite numerous they are too...

Hypothetical explanations for the paradox

https://en.wikipedia.org/wiki/Fermi_paradox#Hypothetical_explanations_for_the_paradox

Extra-terrestrial life is rare or non-existent

Extra-terrestrial intelligence is rare or non-existent

Periodic extinction by natural events

Intelligent alien species haven't developed advanced technologies

It is the nature of intelligent life to destroy itself

It is the nature of intelligent life to destroy others

Civilizations only broadcast detectable signals for a brief period of time

Alien life may be too alien

Colonization is not the cosmic norm

Alien species may have only settled part of the galaxy

Alien species may not live on planets

Alien species may isolate themselves from the outside world

Lack of resources needed to physically spread throughout the galaxy

It is cheaper to transfer information than explore physically

We haven't listened properly

We haven't listened for long enough

Intelligent life may be too far away

Intelligent life may exist hidden from view

Everyone is listening but no one is transmitting

Communication is dangerous

Earth is deliberately avoided

Alien life is already here unacknowledged (UFO phenomenon) 

The ones in bold are my favoured explanations. 

 

Clearly a combination of the explanations above could be responsible. I certainly think we should take the notion that, detectable signals are only broadcast for a limited time, seriously. We ourselves are communicating via fibre optic cables that don't emit RF frequencies into space. Could well be that technologically advanced species utilise technology that doesn't emit. May be just a small window in which signals are detectable. 

We do have to take the possibility that intelligent life is very rare seriously too. Simple life appeared here on Earth as soon as it was feasible. More advanced life though took something like one billion years longer. Cleary advanced life is hard. 

And what of UFO's? Can we really dismiss them as top secret aircraft, marsh gas, weather phenomena and optical; illusions? Or perhaps there is veracity to these claims and we are seeing Alien, Von Neuman, robotic  probes. 

 

 

Edited April 8, 20215 yr by martin-w

"Alien species may not live on planets" I hadn't thought of that, very interesting...

I do not take as trump the 'too far away' explanation. Einstein et al. made obsolete some Newton absolutes, and nowadays papers and seminars about strange behavior near singularities. Speed limit centers may not hold.

Thanks for the Drake equation and Fermi paradox, of which I was unaware.

I remember years ago meditating as Carl Sagen enthused about 'billions and billions of stars' on Cosmos and watching Jodie Foster in the old movie "Contact". And I was thinking, o.k. then where are all these wonderful creatures? And if the universe is monstrously big compared to the Milky Way, so what, because it somehow does not seem very big compared to the infinite.

I have stacks of old radio magazines and rebuild tube radios from the 1920's and 30's. Publications in that era were all excited about the signals which we should be hearing soon coming from outer space. Almost every year an issue or two of the many radio hobby magazines had such an article when commercial broadcast radio stations first appeared in stores and in living rooms around the western world.

 

Many years ago I predicted that the first interstellar war would be prompted by us constantly beaming reruns of "I Love Lucy" into their airspace.  Given the speed of light and the distances involved, they may already be on their way. 

😄

Hook

3 hours ago, Fielder said:

I do not take as trump the 'too far away' explanation. Einstein et al. made obsolete some Newton absolutes, and nowadays papers and seminars about strange behavior near singularities. Speed limit centers may not hold.

 

Not sure what you mean there. 

 

Quote

It may be that non-colonizing technologically capable alien civilizations exist, but that they are simply too far apart for meaningful two-way communication.^[90]:62–71 Sebastian von Hoerner estimated the average duration of civilization at 6,500 years and the average distance between civilizations in the Milky Way at 1,000 light years.^[75] If two civilizations are separated by several thousand light-years, it is possible that one or both cultures may become extinct before meaningful dialogue can be established. 

 

2 hours ago, LHookins said:

Given the speed of light and the distances involved, they may already be on their way. 

 

Our radio signals have only travelled about 200 light-years.  52,850 light years is the size of our galaxy. So if intelligent species are  rare, its doubtful any would have detected our transmissions. 

Of course it is possible that we are the only sentient, intelligent beings in the universe, but I doubt it.

There could be a civilization as advanced as we just a few hundred light years away, or even much closer, and we'd never know it.  Like Martin said, our own radio emissions have not traveled very far at all, plus there's the fact that we're not scanning all frequencies, in all directions, all the time, so we could easily miss an alien signal.

The known universe is so vast that it is difficult to comprehend.  Our own galaxy is over 100,000 light years across and 1,000 light years deep with hundreds of billions of stars.  There are hundreds of *billions* of galaxies that we know of.  You do the math.  IMO, there must be many advanced civilizations out there.

Until we develop faster than light travel, which I am convinced is possible by "bending" or compressing space, we will not likely encounter intelligent alien life unless they visit us first.

Dave

1 hour ago, martin-w said:

Our radio signals have only travelled about 200 light-years.

There are about 5900 stars within 150 light years of Earth.  About 850 of these are visible to the naked eye.

Hook

Edited April 8, 20215 yr by LHookins

22 minutes ago, LHookins said:

There are about 5900 stars within 150 light years of Earth.  About 850 of these are visible to the naked eye.

Hook

 

Yep, very true, which was why I said "So, if intelligent species are  rare". The Fermi Paradox would suggest rare. If very common it would be a different scenario. 

Edited April 8, 20215 yr by martin-w

1 hour ago, dave2013 said:

Of course it is possible that we are the only sentient, intelligent beings in the universe, but I doubt it.

 

Yep, we certainly cant rule it out. Given the age of the universe, may simply be that we're alone now but over the entire 13.8 billion years there have been many advanced species, as a species, we're late to the party. 

 

1 hour ago, dave2013 said:

plus there's the fact that we're not scanning all frequencies, in all directions, all the time, so we could easily miss an alien signal.

 

Very true. And its not a stretch to conceive of aliens using a form of communication we haven't even dreamt of and can't detect. 

 

1 hour ago, dave2013 said:

There are hundreds of *billions* of galaxies that we know of.  You do the math.  IMO, there must be many advanced civilizations out there.

 

Our current best measurements tell us that the universe is flat. If it is, then that implies infinite. And if infinite, then anything that doesn't defy the laws of physics WILL happen. Simply because there's only a limited number of ways atoms can arrange themselves, so repetition must occur. Thus, literally an infinite number of species like us and identical to us in the universe. Which was why I was careful to stipulate "galaxy" not universe in terms of the Fermi Paradox. 

1 hour ago, dave2013 said:

Until we develop faster than light travel, which I am convinced is possible by "bending" or compressing space, we will not likely encounter intelligent alien life unless they visit us first.

 

Seems that physics doesn't rule out warp drive. New calculations are suggesting that negative energy may not be required now as well. Although that would be close to the speed of light but not beyond IIRC. 

Still an enormous amount of energy required though. In fact Alcubierre himself said that we would be better off trying to travel through worm holes than creating a warp drive. But then his comment was some time ago. Not sure if he's changed his mind. 

In the short term, in regard to our laudable endeavours to send people to Mars and further out in the solar system, nuclear thermal propulsion has to be the right move. 

And in terms of nuclear powered plasma rockets, below is very interesting...

Dr Fatima Ebrahimi has invented a new fusion rocket thruster concept which could power humans to Mars and beyond.

https://news.sky.com/story/new-concept-for-rocket-thruster-exploits-the-mechanism-behind-solar-flares-12202285

 

 

49 minutes ago, martin-w said:

In fact Alcubierre himself said that we would be better off trying to travel through worm holes than creating a warp drive.

There is no reason to think that wormholes would provide a smooth passage, is there? I would think that something of that scale would be so turbulent that it would destroy any kind of vessel that we could ever build.

8 hours ago, martin-w said:

Periodic extinction by natural events

 

8 hours ago, martin-w said:

It is the nature of intelligent life to destroy itself

Reminds me of Arthur Clarke's Rama Revealed. There were lots of alien civilisations and some almost made it to our solar system but died out before that could happen. I think genetic engineering gone wrong was one of the reasons.

Edited April 8, 20215 yr by dmwalker

1 hour ago, dmwalker said:

There is no reason to think that wormholes would provide a smooth passage, is there? I would think that something of that scale would be so turbulent that it would destroy any kind of vessel that we could ever build.

 

I recall that it would need to be a supermassive black hole, to avoid spaghettification. It would also need to not be feeding.

 

 

I've often wondered how the folks in Star Trek, Star Wars, et cetera magically avoid time dilation during their journeys. I dimly recall a story by Heinlein (IIRC) that featured two twins who were telepathic. They were chosen among many such gifted twins to serve as communicators between Earth and exploration space craft.

They were about 15 years old at the beginning of their mission, but by the time the ten year mission was completed and returned to Earth, the one who remained on Earth was an old man, and his twin a mere 25...

Thanks to Einstein, we know that the faster you go, the slower time passes--so a very fast spaceship is a time machine to the future. Five years on a ship traveling at 99 percent the speed of light (2.5 years out and 2.5 years back) corresponds to roughly 36 years on Earth.

https://www.amnh.org/exhibitions/einstein/time/time-machines

https://www.youtube.com/watch?v=nRc0yaMW7Mw

Mike A.