Abundance Of Life In The Universe

[MJR]

Things to consider:
Formulas were developed to calculate the number of communicating civilizations. The number of communicating civilizations (N) can be calculated by the following formulas:
N=N*fpneflfifc
N=R*fpneflfifcL

Note: 2nd letters below are subscripts.

Where
N*= Number of stars in the observable universe.
R*= Rate of star formation.
fp= Fraction of stars with planets.
ne= Mean number of planets per star with environments suitable for life.
fl= Fraction of these planets on which life does not arise.
fi= Fraction of life-bearing planets on which intelligent life evolves.
fc= Fraction of these planets which develop the technology needed to use radio
communication.
L= Mean life of communicating civilizations.
The first formula assumes that a communicating civilization, once formed, survives as long as the planet. The second takes account of the destruction of civilizations.

Note: Numbers below separated by a dash mark are superscripts.

In 1958, Shapley first calculated in “Of Stars And Men,� that there are:
10-20 stars in the universe.
10-11stars in galaxy.
10-9 galaxies.
10-17 stars with planets.
10-14 planets at a suitable distance for life to arise.
10-11 planets with a suitable atmosphere.
10-8 planets on which life arose.
10-5 planets with intelligent life.
10-2 planets with communicating civilizations.
Shapley did not consider the rate of star formation or the rate of destruction of civilizations and came up with a relatively conservative estimate of 10-2 communicating civilizations in the universe. He used low values to present the least favorable scenario.
Sagan and Drake later came up with a much more optimistic estimate of 10-10 to 10-16 communicating civilizations in the universe. They also gave a “high� and “low� optimistic estimate for communicating civilizations per universe and per galaxy.
Low Optimistic: 10-10 per universe.
0.1 per galaxy.

High Optimistic: 10-18 per universe.
10-7 per galaxy (this would give us a pretty good chance of finding life within our galaxy)!

Other Factors:
Most stars are double or triple and are inappropriate places to look for life due to unstable planetary systems.
Large and hot stars have short life times. Our Sun is a Type G2.
Small stars are not suitable because they have a smaller habitable zone.
The distance from a star is very constrained. For example, if the Earth were 1% closer to the Sun there would be a runaway “greenhouse effect.�

How are we going to find extraterrestrial life?
Spacecraft-No good. With our present understanding of physics it would take too long.
Robots-Possibly. At this point not realistic.
Radio Communication-Our best shot right now; however there is the problem of what frequency to transmit and receive at. SETI.

[Tales from Tanelorn]

I think it is almost a certainty that there will be life out there in the Universe. It is extremely big and I dont just mean enormous and it has been around for one heck of a long time. Our sun is quite new, whole star systems have been born and died before our sun came along. So there is plenty of chance for life giving molecules to have come together throughout the universe.

So the difficulty is that we have to find intelligent, technologically advanced life, within range of us and which exists in our present timeline. This I think may mean we might never ever make contact, its just down to chance.

How about a poll "Would you want to make contact with Extraterrestrial Intelligence?" could they be dangerous!?

[VonWeiner]

Yes, it is called the Drake Equation. I first saw it on Cosmos, an excellent series done by Carl Sagan and shown on PBS. I have the series on DVD and absolutely recommend it for anyone (especially if you like astronomy)

Here is a good link to it. You can plug in your own values or use Drake's.

The Drake Equation :idea:

[MJR]

Tales from Tanelorn--You make a critical point when you state, "...which exists in our present timeline." This variable is probably the trickiest one to overcome.

I really like this quote from Michael Moorcock: "No, I think Space is a dimension of Time. My theory is that Time is a field and that Space exists as an aspect of Time." So, if true, and we can learn to manipulate this field, then perhaps we have a chance?

Von Weiner--Thanks for that link. Very cool. I havn't seen that one before.
In case anyone is interested in this stuff, here's some more reading on the subject matter:


"The Search For Extraterrestrial Intelligence," C. Sagan and F.Drake, Sci.Am. May 1975, p.80.

"The Primeval Fireball, " P.J. E. Peebles and D.T. Wilkinson, Sci. Am., June 1967, p. 28

"The Cosmic Distance Scale," P.Hodge, Am. Sci. 72, 474 (1984).

"Supernovas in Other Galaxies," R.P. Kirshner, Sci. Am. , December 1976, p. 89.

"Did a Supernova Trigger the Formation of the Solar System?," D.N. Schramm and R.N. Clayton, Sci. Am. Oct. 1978, p. 124.

" The Youngest Stars," G.H. Herbig, Sci. Am. Aug. 1967, p. 30.

"More Than A Planet, Almost A Star," M.M. Waldrop, Science, 227, 44 (1985).

[VonWeiner]

:idea:

SETI on Drake's Equation

[Tales from Tanelorn]

I once exchanged email with the director of SETI. I was interested in how they hope to detect a signal which is so low down in the noise floor. The answer is they have to assume the bandwidth is exceedingly low so they can average the signal over a relatively long time. Then they can also look for specific types of modulation schemes such as FM churp which also provides an improvement in signal to noise. Problem is it would be impossible to distinguish from noise unless you knew the exact characteritics of the modulation scheme. So its kinda chicken and egg.

[Tales from Tanelorn]

MJR I put together a few thoughts on time on another thread.
Even Feynman said "dont ask me what time is".

Without it things would remain pretty much unchanged. Did the Lords of Law try to destroy time yet?

By the way Jere, using a singularity I have the ability to travel through time because as you can see I know in advance that you are going to say that science ceases to exist in black holes.

In fact, effectively, nothing exists inside a black hole since it is a singularity which produces only one effect in our universe, gravity.

[Corum]

Time slows down near massive objects and may even cease to exist entirely inside black holes.

[Jere]

You could say that science ceases to exist in black holes or supernovas (S.Delanyآ´s Nova).
I think right now itآ´s very sci-fi to think about finding intelligent life; but it would be stupid to think we are alone. We are just too far away(in time or space). And, how many sci-fi concepts have become a reality in the last century?

[Tales from Tanelorn]

OK I think I got it sussed. Time doesnt actually exist as such and neither does space for that matter. They are just observational, relative positional measurements on matter and energy and their units are seconds and meters. In fact matter and energy are also more or less the same thing and matter can be viewed as "condensed energy".

So what are we left with is just energy and the distance it moves from one point to another and the time it takes to get there as the matter or energy moves from a higher energy state to a lower energy state or changes form...

Are we clear?

Look out here come the Vogons !

[Jerico]

Yeah that sounds right, Tales.
I believe the professor from the one philosophy
class I took said time is "the perception of self in space" ?
awe crap I can't even remember at this point.
Nevermind! :roll:

[Tales from Tanelorn]

When I die I am going to donate my body to Science Fiction...

[VonWeiner]

Time doesnt actually exist as such and neither does space for that matter. They are just observational, relative positional measurements on matter and energy...

This is getting into the metaphysical. All of these things may just be mechanisms for your mind to understand the world around you. Time, space, energy - these are things that are measured relative to you. Even in Einstein's theories on Relativism, you find that time, space and energy are relative to the observer. For the man in the spacecraft, time passes differently relative to those on the ground. Space(distance) for those who are at rest seems vast, but to those travelling at great velocity, it may not. The amount of energy it requires to move an object in space, may be far less than needed in some other medium, thus energy has meaning only based on the position of the observer. We have managed to assign values to all of the above, in hopes of finding a constant - a truth, so to speak.

I remember that there was one philosophical notion that somewhere in the universe are "perfect" examples of things. For instance, take a sphere: somewhere there exists The Sphere, the sphere that all others are based upon. This means that all other spherical objects are just that - spherical. But they are not spheres. Only one Sphere exists, all others are just approximations. So when one says, "that is a sphere", he is wrong, for he has never seen a sphere, truly. It is said that this notion can extend to most things. If you have never seen a square, how can you claim something is or is not square? You have no real knowledge. All of your thoughts are theory. Nothing more.

It can even be said about such a simple thing as color. Look at an object in front of you. On this planet alone, there are many different creatures who would, if they could communicate it, dispute the color of everything you see. They observe color from a different perspective. The house fly lives out its life in a single day, but to us this is a fleeting moment, a day amongst many. Could it be that this crature sees its "day"(time) in a way far different from our own?

Life, energy, time, distance - we have given each its own measure, a gauge to help us understand the things we observe. Who can say what the truth of anything is?

I could go on further and I think I will tomorrow, but it is 2:45am and I am probably rambling (even more than usual!), I'll probably read this tomorrow and say "what the hell was I saying..." :lol:

[Tales from Tanelorn]

I could go on further and I think I will tomorrow, but it is 2:45am and I am probably rambling (even more than usual!), I'll probably read this tomorrow and say "what the hell was I saying..."

I do so with 95% of what I say! :P

[MJR]

It's fun to speculate though, eh?

:P