E.T. a machine

[UnderseaLcpl]

I would think that if other intelligent life did exist, it would exist in more place than one, and at least some of those civilizations would be older than ours. That being the case, if the were an extraterrestrial lifeform(s) with the means to travel to Earth and hurt us, it stands to reason that we would have picked up somebody's radio transmissions by now. The galaxy is only 100,000 light years across, after all.

[Schroeder]

The Galaxy yes, the universe no. Other life forms don't have to be from our galaxy.
Besides, why do you think that an alien species would use radio signals as we do. Maybe the communicate through light or something we've never heard of. If you travel for light years radio communication (that only travels at the speed of light) would be extremely ineffective. You need something faster than light to stay in touch with your home world.

[UnderseaLcpl]

I just assume that at some point in their history they would have used radio communications. You have to start somewhere.

And of course, who knows with extragalactic lifeforms. I doubt we'll find any evidence of their existence or non-existence anytime soon.

[Oberon]

Their radio transmissions may well have reached us when we were banging rocks together for communication and now they're using something bigger and better. I mean, it's a big timeframe we've got to deal with, not to mention a big universe. After all, you say the galaxy is only 100,000 light years across...and radio waves travel at the speed of light (or thereabout), that means that it'd take 100,000 years to get here from the other side of the galaxy. So, it's still a big ballpark.

[Skybird]

Originally Posted by UnderseaLcpl

I would think that if other intelligent life did exist, it would exist in more place than one, and at least some of those civilizations would be older than ours. That being the case, if the were an extraterrestrial lifeform(s) with the means to travel to Earth and hurt us, it stands to reason that we would have picked up somebody's radio transmissions by now. The galaxy is only 100,000 light years across, after all.

"Only" 100,000 lightyears...? Some more respect, please! Probolem is that most people just read numbers - they do not try to form an image of what they mean. Which in this case is difficult to imagine indeed, I admit.

Could you specify the basis of your assumptions on others using radio signals, 100000 lightyears being "only" 100000 lightyears, and the expected ratio of surviving civilisation being older than ours?

1 lightyear translates into a distance of

9,450,000,000,000 km.

100000 lightyears thus are around 9.45x10^17 km, or

945,000,000,000,000,000 km.

"Only"...?

the next galaxy is 2.5 million lightyears away, Alpha Centauri. In km that is

23,625,000,000,000,000,000 km

When we see Andromeda in the telescope (or the naked eye), we see it as it was 2.5 million years ago. For comparison: the homo erectus appeared on the scence around 1.8 million years ago, the australopithecus africanus is marked at around 2 million years (there were several "models")

The milky way is estimated to feature around 100 billion suns. If you would start to count them and take one second per sun, you woild need 100 billion seconds to count them all - or the equivalent of around 3 thousand years.

Planets not counted.

It is estimated that the region of the milky way in which our sun is located, forms the youngest 10% of star systems, meaning that 90% of those suns in our galaxy would be older than ours - up to hundreds of millions and billions of years. If you assume that only one in a thousand planets can carry life, and just one in one thousand of these life-carrying planets carries intelligent life, and of these one in a thousand in a thousand planets around 90% are millions, hundreds of millions and billions older than our solar system - can you imagine how many civilisations there would be (if they survived of course) that are incredibly older and superior in knowledge to ours? not all stars have planets, but stars may have more planets than one. Let's assume that in mean for each star thewre is one planet (jujst speculation, I have no data basis for this speculation, it's just a mindgame). (10^11/1000)/1000= 100,000. that would be the number of civilisations that are much older than ours. that number means nothing, admitted - i just play games to illustrate what the numbers would mean if they were like this.

How much older could these 100,000 superior civilisation be? If you scale the 14 billion years we estimate since the Big Bang, to one full calender year, than the milky way would have formed up sometime in February. But the solar system would have formed up not before 3rd September, and first life on earth at 22nd September. so theyx could be older by several weeks to several months. One week equals 270 million years.

also, this dance of numbers:
http://www.subsim.com/radioroom/show...=173045&page=3
Posting #40.

We have no reason to assume that any superior civilisation must use equivalents to our form of tehcnology, and radio. Also, since when have radio emissions left earth, and powerful7energetic eough to travel long distance? make it 1920, for example? then these transmission have travelled just 90 lightyears deep into space (loosing in clearness and energy while doing that). That is 0.09% of the long axis of the milky way's diameter. the milky way is 3-dimensional, so we would need calculate the volume of the milky way with a diameter of 100000 lyversus a shere of 90 ly. that tells oyu how many stars our radio signals maybe, possibly could have fetched up. and that is: not too many. Now, when the signals reaxches somewhere, the maybe present intelligence "thereW" needs to know what to look for 8which may or may not be in mutual support with it'S way of having a culture, scine and technology). It must be awake and must have switched on it's equipement when the wave reaches it's position. It must send back a signal if it wants to reply - and the reply will travel as many decades as our signals took it to travel there.and finally: the alien intelliegnce must be interested and motivated to answer.

there are so many reasons we can imagine why we have not picked up signals so far. Add the even greater number of reasons that we can not imagine. Or do you think we are so fantastic that the galaxy is standing in line just to make our acquaintance? We humans tend to think we are so supr, so cool, so "in". just some generations ago - and not many! - we still tried to make the whole universe revolve around Earth. But I think, in this galaxy the odds are that we are - just one of the latest newcomers in the babygroup in the Kindergarden.