How Many Earths Could Be Out There?

The universe is extremely large and consists of Billions of galaxies and Trillions upon Trillions of stars. We are in the Milky Way galaxy. which itself can hold millions of stars itself...thinkin...

if the probablility of another earth-like planet is..oh lets say 1 in like a zillion.. and the fact that there are more then one trillion stars just between two galaxies alone which we have more then billions of in this universe( galaxies).. id say the possibility of there being another planet like ours is...there has got to be AT LEAST one.
correction there is said to be millions of stars in a single galaxie..and for all we know there are trillions of galxies...all most likely containing "planets" around them in orbit.
so i come to my conclusion...even if the chances SAY its extremely unlikely it has to be possible...there are just to many dang solar systems and galaxies in this huge place to even begin to deny such a thing..id like to see someone though prove this wrong or give a good idea why i could be wrong... Aliens HAVE to exsist! no matter what form they will come in..
:.Kiliker.:

What you are referring to is what is known as the Drake Equation, thought up by none other than Mr. Drake in the 60s or early 70s. Given this powerful tool, roughly 35 years later, we are no closer than we were back then to the answer. You challenge someone to prove you wrong. That's the problem with philosophy masked as science--you can't prove "what if" ideas wrong that are not bound by the laws of science.

Let me (try) to cite an example of this. Long, long ago lived a smart guy who thought that the universe was finite. To prove his case, he stated that if the universe were infinite, the night sky would be infinitely bright from the combined light of the infinite stars out there. Sounded good; convinced a lot of people. But he was completely wrong. If you wish to discuss ideas, get crazy. But if you expect people to be able to prove your thoughts and ideas incorrect when dealing with an inifinite space, it ain't gonna happen.

It's good to see people thinking though.

Not considering the possibility of alien civilisations as part of the equation......as all we're doing is calculating how many "earths" there are in the Galaxy, here is an estimate of their numbers......

I've stated these figures before in previous posts, but I will do the same here for clarity of purpose. From the simulations of developing stellar systems, and from observation, it's is thought that every stellar system will have at least 1 Earth-like planet. However, given that 5% of all Sun like stars have "Hot Jupiters" and therefore may not have any terrestrial planets at all (although new information suggests otherwise), we'll discount those.

So, that leaves approx' 95% of all Sun-like stars that have planets are suitable for Earth-like planets. That means 5.7 billion late F class stars (F5-F9), 11.4 billion G class stars and 47.5 billion K class stars. Now with those of M class (M0-M4) that are believed to be able to sustain an Earth-like planet, nearly all of them don't have "Hot Jupiters" (around 99%), so that means 114 billion upper M class stars should have an Earth-like planet. That means, in this Galaxy alone there are 178.6 billion Earth-like planets!!!!.

If you include in the definition of "Earth-like" those planets that are more like Mars, or even intermediatry between Earth and Mars in conditions, the numbers skyrocket upto 400 billion or more. So as you can see, there's no shortage of possible places for an alien civilisation to have developed on, just in this galaxy alone.


[edit on 19-9-2006 by GhostITM]

Originally posted by GhostITM
From the simulations of developing stellar systems, and from observation, it's is thought that every stellar system will have at least 1 Earth-like planet. However, given that 5% of all Sun like stars have "Hot Jupiters" and therefore may not have any terrestrial planets at all (although new information suggests otherwise), we'll discount those.

5%?!!!

I'd re-check those figures--it will have a major impact on your results.

His figures are partially made up and partially extrapolated from data gleaned from Simulations and Exo-Planet hunters. And and all new information is likely to make those estimates swing wildly around over time. just like the estimated age of the Universe

[edit on 19-9-2006 by sardion2000]

If there are other 'earths', then I say it most certainly not our placwe to find them since we haven't come up with the technology. And even if we did have the means necessary, I would hate to see us go there for fear that some people would get greedy and destroy what upon their homeland was beautiful and turn it into another thing like this planet. So lets leave the aliens/ humans be...

Large Jupiter-like "still born stars" are not the exception at 5%, they are the majority--dare I say by far. I found the figures to be offensive because they were presented in a factual way for someone who was asking a really good question (i.e. showing imagination, intelligence, curiosity, etc).

Hey Guys,
This topic has already been covered before. Check out these threads....

How Big is the Universe?

and

Are There Any Super Intelligent Civilisations in the Universe?

And there needn't be Earth like planets to harbour life!



[edit on 19-9-2006 by mikesingh]

Originally posted by backtoreality

Originally posted by GhostITM
From the simulations of developing stellar systems, and from observation, it's is thought that every stellar system will have at least 1 Earth-like planet. However, given that 5% of all Sun like stars have "Hot Jupiters" and therefore may not have any terrestrial planets at all (although new information suggests otherwise), we'll discount those.

5%?!!!

I'd re-check those figures--it will have a major impact on your results.

5%......and that is confirmed from radial velocity observations of the Sun-like stars. They've made observations on thousands of Sun-like stars and that's what it shows. Large, Hot Jupiters impart large radial velocity motions on the stars they orbit. The majority of Sun-like stars don't have excessively large radial velocity displacements. Nor do they show the expected doppler shifts (>3m/sec) of their spectral lines which also denote large, close orbiting planets such as Hot Jupiters.




[edit on 19-9-2006 by GhostITM]

Originally posted by sardion2000
His figures are partially made up and partially extrapolated from data gleaned from Simulations and Exo-Planet hunters. And and all new information is likely to make those estimates swing wildly around over time. just like the estimated age of the Universe

[edit on 19-9-2006 by sardion2000]

Read my answer to backtoreality, above. You'll find that what I have quoted is not made up. That is the 5% and such. However, the numbers of planets/stars are based on the estimates of the total numbers of stars within this galaxy, which is thought to be 400 billion. If you want the figures for the numbers of the various types of stars in the Galaxy it's O,B, giants and supergiants (

Originally posted by backtoreality
Large Jupiter-like "still born stars" are not the exception at 5%, they are the majority--dare I say by far. I found the figures to be offensive because they were presented in a factual way for someone who was asking a really good question (i.e. showing imagination, intelligence, curiosity, etc).

Large Jupiters are not "stillborn stars". You are talking about Brown Dwarfs, not planets. The cutoff point for a planet/brown dwarf is 13 Jupiter masses. The figure of 5% is not including brown dwarfs, it's only the figure for planets. Most brown dwarfs are solitary, just like their larger M class cousins. And you can have a look at all the observations and surveys done so far, plus simulations of their formation. You'll find that I'm correct.

If you took offense at that figure, you need to learn something about astronomy. And before you go castigating what I said, you can have it on notice.......I have 35 years of experience as an amateur astronomer. I think I know a little bit more than you do about what I'm talking about.

How many, well to fix the OPs numbers..

There are a few billion galaxies in the known universe.

Each galaxy has about 100billion stars.

So, lets use our own galaxy, anbd we'll assume there are 150billion
stars (for simplicities sake).

Now, we'll assume that about 30% of stars have Earth like planets.

That gives us a grand total of 45billion Earth like planets in our galaxy
alone.

If you want to go further, with life any beyond, I'll provide my own
calculations, using conservative variables.

-30% of stars have planets.
-1 on average planet in the habitable zone.
-Life arises on these planets 95% of the time.
-50% evolve sentient life.
-80% of them develop detectable technologies.
-On average the race produces currently detectable signals for 200
years.

The result is 206 communicating species in our galaxy.

How many, well to fix the OPs numbers..

There are a few billion galaxies in the known universe.

Each galaxy has about 100billion stars.

So, lets use our own galaxy, and we'll assume there are 150billion
stars (for simplicities sake).

Now, we'll assume that about 30% of stars have Earth like planets.

That gives us a grand total of 45billion Earth like planets in our galaxy
alone.

Iori, that's pretty much all assumption and the figures you have quoted don't reflect what they know about the numbers of stars per galaxy nor the numbers of Earth-like planets possible around each system. There are far more than 100-150 billion stars in our galaxy alone...... the most recent estimates put them at between 400-750 billion. Most astronomers use the lower estimate. Just for comparison, Andromeda is estimated to have 1 trillion stars!!!. 45 billion Earth like planets would be an extremely conservative answer, and not based on what they know from simulations done on planet formation.

Want to find out a bit more about our Galaxy and Andromeda.....go to these:

www.seds.org... (our Galaxy)

www.seds.org... (Andromeda Galaxy)

But, your answer is a good attempt.....keep up the good work




[edit on 19-9-2006 by GhostITM]

Wow, I did'nt know it was suppose to be that high..

I've always read that it's between 100-200billion in ours.

Thanks for the info.

Originally posted by GhostITM
So that means 114 billion upper M class stars should have an Earth-like planet. That means, in this Galaxy alone there are 178.6 billion Earth-like planets!!!!.

If you include in the definition of "Earth-like" those planets that are more like Mars, or even intermediatry between Earth and Mars in conditions, the numbers skyrocket upto 400 billion or more. So as you can see, there's no shortage of possible places for an alien civilisation to have developed on, just in this galaxy alone.


[edit on 19-9-2006 by GhostITM]

That Is far Greater Then What I was Expecting!.
So The Chances are...The Alien Races We Have Heard Of (grey/communion)...Are just the tiny bit of the top of the Ice berg!...EVEN If a large percent chunk was taken from that mass number, say: by miscalculations..its still a hell of a lot of earth-like planets just ALONE in this Galaxy, and chances are...they are more older then we can ever imagine..more wise more advanced...i bet you the world outside of our solar system is just like movies percieve it...but we are held in the dark because of the government has kept it that way... its a shame if you really think about it..but in ways its a good thing..this planet im sure compared to others is not a peacful one....(in their eyes at least)
Kudos All Of You!

:.Kiliker.:

Originally posted by kiliker30
The universe is extremely large and consists of Billions of galaxies and Trillions upon Trillions of stars. We are in the Milky Way galaxy. which itself can hold millions of stars itself...thinkin...

if the probablility of another earth-like planet is..oh lets say 1 in like a zillion.. and the fact that there are more then one trillion stars just between two galaxies alone which we have more then billions of in this universe( galaxies).. id say the possibility of there being another planet like ours is...there has got to be AT LEAST one.
correction there is said to be millions of stars in a single galaxie..and for all we know there are trillions of galxies...all most likely containing "planets" around them in orbit.
so i come to my conclusion...even if the chances SAY its extremely unlikely it has to be possible...there are just to many dang solar systems and galaxies in this huge place to even begin to deny such a thing..id like to see someone though prove this wrong or give a good idea why i could be wrong... Aliens HAVE to exsist! no matter what form they will come in..
:.Kiliker.:

There are many more, we can only see as far as we can, we cant see the rest of the universe, we don't know what is out there where the telescopes dont reach, and I'm talking about dots, we cant even see the rest of it as dots.
Can you count each bacteria on earth? for a bacteria thinking how many of his felow bacteria are on earth would be equvalent to us thinking how many planets are out there, I belive the chances far exed 1.
Light can be blocked by gas gigants, or gas formation in the universe, black holes, other stars and so on, so we can only see little, we truly dont know and only can see a small part of the universe.


[edit on 19-9-2006 by pepsi78]

I'll put things in a conservative way for you all.......considering the possible number of Earth-like planets that are orbiting the stars in this galaxy, let's just say that only 30% of them ever formed......for whatever reasons.

That still leaves a possible 57.53 billion Earth-like planets. Even 1/10th would be 17.8 billion.

Now, let's figure out how many possible alien civilisations there are out there, given those conservative figures.

If only 1/10th of all those planets developed an intelligent, technologically advanced civilisation (not counting who survived or not, we'll stay with 100% for that value, for expediency), there'd be between 5.75 and 1.8 billion civilisations around in this galaxy alone (for viable earth values between 10-30%.) Given then, that 65-70% of all stars are older than the Sun, that means (taking the 70% value) between 1.26 to 4 billion of them are as old or older civilisations than us.

You can see just how large the numbers can be, even when taken very conservatively.

Thank you guys so much for doing all the calulations, although not 100% acurate (of course we probably will never be) it gave us a good heads up of where we are at...thinking about it is making my head fuzzy, i just cant imagine all of that vaust space, and thinking " i wonder what someone else is doing and thinking on another planet..i wonder what it looks like.." and so on...pretty soon we will be getting more and more answers to all of the questions we wanna know
:.Kiliker.:

This is all awesome, of course, but...

We still have no way of a) finding an actual planet with Earth-like conditions, b)Getting there, and c)surviving the whole trip. We are a long way off... too bad we are spending millions of dollars A DAY on this stupid war (and wars in general) and not INVEST in spaceflight.


sigh...

Originally posted by Mouth
This is all awesome, of course, but...

We still have no way of a) finding an actual planet with Earth-like conditions, b)Getting there, and c)surviving the whole trip. We are a long way off... too bad we are spending millions of dollars A DAY on this stupid war (and wars in general) and not INVEST in spaceflight.


sigh...

A. We will in a decade at the most.
B. Hyperspace my friend, the best way to travel, well apart from
wormholes, but those are just to uneconomic to operate.
C. Well, if we bring food water, and entertainment we'll survive.


But yeah, we could get alot more done and researched if we were'nt
pooring billions a year into war.