Intelegent life in the Universe, how common is it?

[DanS]

If sentience is anything but singular, where are they all?

[Boris Godunov]

Originally posted by DanS
If sentience is anything but singular, where are they all?

Far enough away that we can't detect them.

[reds4ever]

Originally posted by DanS
If sentience is anything but singular, where are they all?

Observing us until we prove ourselves worthy of a seat on the Galactic Council!

Or rather, more boringly, intersellar travel maybe much more difficult than we imagine, everyones just poking around their own little bit of space wondering where everyone else is!

[Boris Godunov]

Originally posted by reds4ever
Or rather, more boringly, intersellar travel maybe much more difficult than we imagine

It would be hard for it to be more difficult than we imagine, since the experts have concluded that interstellar travel of any significance is an extremely remote possibility.

[DanS]

Within the next couple of thousand years it seems likely that we will send self-replicating non-manned interstellar probes to our closest neighbors.

Why wouldn't the aliens do the same? If sentience is anything other than singular, this universe should be crawling with everybody's interstellar probes despite the distances.

[Boris Godunov]

Originally posted by DanS
Within the next couple of thousand years it seems likely that we will send self-replicating non-manned interstellar probes to our closest neighbors.

Which will still take thousands of years to travel even a fraction of the galaxy and send back data.

Why wouldn't the aliens do the same? If sentience is anything other than singular, this universe should be crawling with everybody's interstellar probes despite the distances.

The distances are a lot vaster than you are assuming. Consider that that fastest man-made object ever was the Helios probe, that got up to 150,000 mph in orbit around the sun. Now, at that speed, it would take 11,000 years to reach the next closest star to earth.

If you have a galaxy teeming with life where you have sentience on 1 out of every 100 stars (which is highly unlikely), that will still make interstellar contact a remote possibility.

Besides, the other sentient species could, hypothetically, not be as advanced as us, or just as advanced.

[Whaleboy]

The Drake Equation does not have enough variables. For example, Earths tilt is kept between 20 and 25 degrees because of Luna. The Erath-Moon system is the only case of a double planet in the Solar System (I don't consider Pluto a planet, it is the largest known Kuiper Belt object, technically). Without the Moon the Earth's axis will wobble around randomly between 0-90 degrees, preventing the evolution of complex life.

I would suggest that the degree to which the axis of rotation effects the planet is dependent upon where in the habitable zone the planet is, the albedo of the planet (one would expect it to have a higher effect with a lower albedo) and also of course the presense of other planets at all. Consider that were it not for the moon, the other gravitational influences would be mostly Venus, Mars and Jupiter (to a lesser extent) and Saturn to a far lesser extent. Remove all planets but Jupiter and you have a more stable system in operation, though admittedly not by much it would potentially allow evolution to adapt. This of course relies on a Jupiter-sized object at that distance, and we have seen larger and smaller exoplanets at a variety of ranges to their parent star.

Onother trump card is the thickness of the stellar disc. If the desc is too thick and dense it will cause the planets to spiral inward untill the disc is cleared. this is carried to great extremes with the systems with "epistellar giants", gas giant planets that are closer to their star then Mercury is to the Sun. The only hope for such systems is if a Jovian planet with an earth-sized moon ends up in the star's habitable zone. There is one such planet known. HD177830 b is a 1.28 Jupiter mass planet orbiting the K0 (yellow-orange) star HD177830, located 192 light-years away in the constellation Vulpecula. This planet is likely to be within its habitable zone. A moon found here could have liquid water and look similar to Earth.

Would expect that planet to be very heavily irradiated, which is a problem, though not a fatal one as far as life is concerned. The thickness of the disk would be more a problem for the outer planets, since much of the gas and dust in the inner part of the disc is blown out when fusion starts in the star. That is why there is relatively little hydrogen, helium and interplanetary dust within the orbit of Mars. The gas giants must have formed beforehand, which is likely considering that such planets are failed protostars (consider that if Jupiter were 10x the mass, it would have been sufficient for a fusion reaction to occur, and the Sun would be like many/most other stars in this galaxy: a binary/trinary system). Look at the other gassy planets as evidence of that too.

[reds4ever]

Originally posted by DanS
Within the next couple of thousand years it seems likely that we will send self-replicating non-manned interstellar probes to our closest neighbors.

Why wouldn't the aliens do the same? If sentience is anything other than singular, this universe should be crawling with everybody's interstellar probes despite the distances.

You should at least reference the above, instead of passing it off as your own

It's called Fermi's paradox and, it too, like Drakes equation is a crock of sh1te.

try putting 'Fermi's paradox debunked Sagan' in to Google and have a look round.

[reds4ever]

Originally posted by Boris Godunov


It would be hard for it to be more difficult than we imagine, since the experts have concluded that interstellar travel of any significance is an extremely remote possibility.

I agree Boris, but it does n't stop 'the man in the street' (or people here for that matter) asking the question, 'if they are out there why havn't they found us?'

[Boris Godunov]

Originally posted by reds4ever
I agree Boris, but it does n't stop 'the man in the street' (or people here for that matter) asking the question, 'if they are out there why havn't they found us?'

Ignorance on the part of the man in the street is no excuse. The answer is simple: The distances between us are too vast.

[reds4ever]

Originally posted by Boris Godunov


Ignorance on the part of the man in the street is no excuse. The answer is simple: The distances between us are too vast.

OK, OK I give in, I worded it wrong. Happy now???

[DanS]

The distances are a lot vaster than you are assuming.

The max theoretical speed is something like 1/10th the speed of light. Even at 1/100th the speed of light max speed, our galaxy would be awash in probes of all types in no time.

[reds4ever]

Originally posted by DanS


The max theoretical speed is something like 1/10th the speed of light. Even at 1/100th the speed of light max speed, our galaxy would be awash in probes of all types in no time.

MESSAGE REPEATS:

It's called Fermi's paradox and, it too, like Drakes equation is a crock of sh1te.

try putting 'Fermi's paradox debunked Sagan' in to Google and have a look round.

[DanS]

It's called Fermi's paradox and, it too, like Drakes equation is a crock of sh1te.

Much less a crock of **** than Drake's equation (which is a total crock of ****). It's brings up a lot of interesting questions about our place in the universe.

For the record, I chose "Unsure". Personally, I think looking for aliens is a pretty poor allocation of scarce resources, but there you are.

Edit: With regard to Sagan, he was more of a politician than a scientist. I might do the Google search as you suggest when I get a chance though.

[reds4ever]

Originally posted by DanS

Much less a crock of **** than Drake's equation (which is a total crock of ****). It's brings up a lot of interesting questions about our place in the universe.

Then you know the arguement against it?