2007-07-09 22:37:18 · 12 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
Carl Sagan did a similar estimate and came up with a figure of 10,000!. He based this on the overall number of stars in the Milky Way 10 million*10million. Out of them he deducted the amount that would have planet like formations, some 1 million* 1 million. And out of that sum, planets that could sustain some kind of life. Given the size, and age of the Galaxy, he estimated that 10,000 must have a civilisation.
2007-07-09 22:58:02 · answer #1 · answered by Old Man of Coniston!. 5 · 3⤊ 0⤋
The number of civilisations in the cosmos is currently estimated using the "DRAKE EQUATION".
Find it at:
http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html, and is the base of the SETI project (Search for Extra Terrestrial Intelligence).
Basically, and only for OUR GALAXY:
N = N* fp ne fl fi fc fL
The equation can really be looked at as a number of questions:
N* represents the number of stars in the Milky Way Galaxy
Question: How many stars are in the Milky Way Galaxy?
Answer: Current estimates are 100 billion.
fp is the fraction of stars that have planets around them
Question: What percentage of stars have planetary systems?
Answer: Current estimates range from 20% to 50%.
ne is the number of planets per star that are capable of sustaining life
Question: For each star that does have a planetary system, how many planets are capable of sustaining life?
Answer: Current estimates range from 1 to 5.
fl is the fraction of planets in ne where life evolves
Question: On what percentage of the planets that are capable of sustaining life does life actually evolve?
Answer: Current estimates range from 100% (where life can evolve it will) down to close to 0%.
fi is the fraction of fl where intelligent life evolves
Question: On the planets where life does evolve, what percentage evolves intelligent life?
Answer: Estimates range from 100% (intelligence is such a survival advantage that it will certainly evolve) down to near 0%.
fc is the fraction of fi that communicate
Question: What percentage of intelligent races have the means and the desire to communicate?
Answer: 10% to 20%
fL is fraction of the planet's life during which the communicating civilizations live
Question: For each civilization that does communicate, for what fraction of the planet's life does the civilization survive?
Answer: This is the toughest of the questions. If we take Earth as an example, the expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict or will we overcome our problems and survive for millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.
When all of these variables are multiplied together when come up with:
N, the number of communicating civilizations in the galaxy.
Multiply the result by the billions of galaxies that exist, and the estimate is pretty high!
The estimate? unknown, but leads to think "unthinkable and impossible" that we are totally alone.
2007-07-09 23:37:41 · answer #2 · answered by just "JR" 7 · 2⤊ 0⤋
This pertains to our own Milky way Galaxy. human beings have studied the mass distribution of stars interior the galaxy. further, one additionally knows the quantity of sunshine placed out with the help of each and every variety of celebrity. So, with the help of measuring the comprehensive quantity of sunshine interior the galaxy (talked approximately as luminosity), and understanding the mass, you possibly can estimate the type of stars that are there interior the galaxy. So, even nonetheless we can not incredibly count selection the type of stars interior the galaxy, we are able to estimate the type of stars interior the galaxy as extra or less a hundred billion (a hundred,000,000,000). It seems that there are various extra stars with mass below the mass of the sunlight than with mass extra beneficial than the mass of the sunlight. So, all of it works out stunning. The sort of stars interior the Universe would be envisioned with the help of multiplying the type of stars interior the Milky way with the help of the type of galaxies interior the Universe. it incredibly is an exceptionally inexact approach yet provides us a coarse theory.
2016-09-29 10:31:56 · answer #3 · answered by mcglothlen 4 · 0⤊ 0⤋
ZERO!
The calculation is as follows:
The universe is infinite. Within that infinite space are an infinite number of planets. Only a finite number of those planets are populated with civilisations. Any finite number divided by infinity is so small it can legitimately be considered zero. Therefore, there are zero populated planets in the universe and thus no civilisations.
Before you argue that planet earth contains a civilisation watch the news - there's nothing civilised about us!
2007-07-10 06:52:20 · answer #4 · answered by cafcnil 3 · 0⤊ 1⤋
It is most probably from 20 to 60.
Further, there are probably from 300 to 3000 planets on which there are the remains of a now-extinct civilization. Pessimists think that within two or three centuries there will be one more.
2007-07-10 07:00:41 · answer #5 · answered by Anonymous · 2⤊ 0⤋
There is room for thousands of intelligent,technological societies in our galaxy.
Many would be thousands of light years away,many more would be obscured by intervening matter.
A recognizable signal from any one is very unlikely,but possible.
Millions more reside in other galaxies,obscured by much more intervening matter and at such distances that any communication is virtually zero.
2007-07-10 00:35:30 · answer #6 · answered by Billy Butthead 7 · 1⤊ 0⤋
there are a lots of .i really wonder why mankind is looking for the same sort of stuff ; 'iphone culture ' civilisation out there in this vast universe.
if you take a look the life of other animal or our eco system here in this earth itself ,you will find answer ; we know a little about some and dont know anything at all about others.
we hope to see the same human like aliens and try to imagine that they speak the language which we understand.
untill we get rid of those stereotypes from our mind we will never find anything .............
at least they dont use iphone to comunicate ...i bet
2007-07-10 00:00:46 · answer #7 · answered by Rave 1 · 1⤊ 1⤋
there must at least be one other inteligent life form because there must be thousands of other plantets just like earth considering how big the universe is and we have alredy discovererd another earth so I would say if there are 10 000 planets like earth then there should be at least 1000 civilizations like us in the universe. people who think that we are alone in the universe is just like the people who said the world was flat.
2007-07-10 01:58:54 · answer #8 · answered by aaaaaaa 4 · 1⤊ 1⤋
Only just the one and we are it. So hard luck you have got us for the rest of your life.
2007-07-09 22:46:05 · answer #9 · answered by focus 6 · 0⤊ 2⤋
it's difficult to believe were are all alone in the universe...but who can say for sure?
2007-07-10 06:38:07 · answer #10 · answered by maurice 7 · 0⤊ 1⤋