Empirical evidence for et's

[granpa]

Many scientists believe that et's are likely to exist.

Some would say almost certainly exist.

 

Empirically speaking:

Either et's exist or they don't so the a priori probability is 0.5 = 50%

This just means "we dont know one way or the other".

The only empirical evidence that et's exist that I have ever heard anyone claim is that we observe life here on earth therefore et's are likely to exist.

 

By Bayes Theorem:

Probability that ets exist given that we observe life on earth = 0.5*probability that we observe life on earth given that et's exist/probability that we observe life on earth

 

0.5*1/1 = 0.5

 

The probability is completely unchanged by the observation that life exists here on earth.

We still dont know one way or the other.

 

So if you happen to believe that et's are likely to exist then what empirical evidence do you base that belief on?

[Daecon]

Or, conversely, what empirical evidence is there that Earth is somehow special or unique in all the Universe by being the only planet amongst millions of stars in millions of galaxies to be able to support life?

Edited July 26, 2016 by Daecon

[granpa]

what part of "we dont know one way or the other" did you not understand?

[MigL]

Using your logic, I have a 1/2 probability of winning the lottery.

Either I win, or I lose.

 

Never mind the fact that there's millions of ways for me to lose , and only one way to win !

Edited July 26, 2016 by MigL

[granpa]

that is the a priori probability if you dont know anything more about it

 

each time you lose you will revise the bayesian probability downward until it eventually approaches the true probability

[ajb]

You might be interested in the Drake equation - though we are not sure how useful it is as some of the parameters are pretty much just guessed.

[granpa]

I'm looking for empirical evidence

[ajb]

I'm looking for empirical evidence

Right now there is no evidence.

 

We know that the building blocks of life are found throughout the galaxay and Universe. We have found planets that sit in the 'Goldilocks zone' of their respective systems. We know that there is lots of room in our galaxy for life - let alone the Unievrse. The best one can do right now is try to put some numbers to what we observe to get some estimates on various probabilities. The Drake equation is one way of trying to put some kind of numbers to the question of how many extraterrestrial civilizations in the Milky Way galaxy that we maybe able to detect via their communications.

 

The bounds given by the Drake equation do not say anything about life that is not advanced.

[granpa]

Difference between empiricism and rationalism:

 

Something is empirical if it conforms to observation.

Something is rational if it conforms to the laws of cause and effect

 

the existence of ets is the most rational possibility

Edited July 26, 2016 by granpa

[ajb]

the existence of ets is the most rational possibility

In this sense I agree - there has been no observational evidence for the existence of life elsewhere in the Universe.

[Strange]

the existence of ets is the most rational possibility

 

I thought you said you were looking for empirical evidence?

 

Is that why this is under religion, because you believe in the existence of ETs in the absence of any evidence?

[granpa]

absence of empirical evidence.

[Daecon]

Absence of evidence is not evidence of absence. Just because there has been no definitive proof that life definitely exists outside of Earth, that doesn't imply that Earth is the only place in the Universe that has or can have life.

[granpa]

Nope its not. Unless you would expect to see such evidence

[Strange]

In this case, the absence of evidence tells us nothing one way or the other. It is not like we have failed to find evidence where there really should be some (in which case absence of evidence could be evidence of absence).

 

So we are back to: we don't know.

[swansont]

I'm looking for empirical evidence

 

 

 

!

Moderator Note

Well, then, this doesn't belong in Religion. Moved.

[John Cuthber]

I'm looking for empirical evidence

Here is a list

 

 

Until that list gets longer, there's no reason for the thread to get longer.

[Moontanman]

Here is a list

 

 

Until that list gets longer, there's no reason for the thread to get longer.

 

Stone Cold Dude!

 

Recent papers and empirical data suggests that the possibility of habitable planets has expanded greatly, out to 10 AU around Sol like stars... So many terrestrial class planets have been found in this area around other stars alien life is beginning to look more likely than ever.

 

Of course there are a hand full of UFO sightings that have a rather high strangeness, How about that granpa?

[granpa]

Something is empirical if it conforms to observation.

Something is rational if it conforms to the laws of cause and effect

 

Question: What is an example of something that is rational but not empirical?

Answer: Et's

 

Empirically speaking:

Either et's exist or they don't so the a priori probability is 0.5 = 50%

This just means "we dont know one way or the other".

The only empirical evidence that et's exist that I have ever heard anyone claim is that we observe life here on earth therefore et's are likely to exist.

 

By Bayes Theorem:

Probability that ets exist given that we observe life on earth = 0.5*probability that we observe life on earth given that et's exist/probability that we observe life on earth

 

0.5*1/1 = 0.5

 

The probability is completely unchanged by the observation that life exists here on earth.

Empirically speaking, We still dont know one way or the other.

 

 

However rationally speaking we know that the laws of cause and effect have allowed life to exist here on Earth and those same laws apply everywhere throughout the Universe. Given the vast size of the universe it is most rational to believe that these exist

[Daecon]

Probability doesn't work like that.

[granpa]

Bayesian probability does though

[Moontanman]

I'm looking for empirical evidence

 

 

They're here they're there they're everywhere so beware...

[Prometheus]

Bayesian probability does though

 

The probability of life on Earth given we observe it is one. But the unconditional probability of life on Earth is less than one: it might never have got started, or a meteorite might have wiped it all out. Similarly, the probability of life on Earth given ET exists is less than one.

 

Check out the cancer at 65 example on wikipedia's Bayes page. Even though we know the person in question is 65, the (unconditional) probability that the person is 65 is given as 0.2%, while the probability of being 65 given they have cancer is given as 0.5%. Following your example we would say both these events have a probability of one.

 

 

 

Empirically speaking:

Either et's exist or they don't so the a priori probability is 0.5 = 50%

This just means "we dont know one way or the other".

 

A uniform distribution is not necessarily the best choice of prior in the absence of any other information. Fisher is reported to have said:

 

Not knowing the chance of mutually exclusive events and knowing the chance to be equal are two quite different states of knowledge

 

 

We could equally say, due to complete ignorance of what is out there, each planet in the universe has a 50/50 chance of harbouring life. Then when we came to consider the chance of life on any planet, we'd have anything but an equal prior.

 

For instance, in this paper, they model the prior probability of abiogenesis occurring as a Poisson process.

[granpa]

Not the probability that life exists on Earth. The probability that we observe life on Earth

 

That probability is of course 1

Edited August 1, 2016 by granpa

[Moontanman]

Not the probability that life exists on Earth. The probability that we observe life on Earth

 

That probability is of course 1

 

 

We have done so little real investigation of life other than the Earth I am still optimistic. I think NASA missions should be more of a hunt for life than they currently are. Checking out the geysers on Enceladus would be high on my list of priorities... The Curiosity rover is not checking for life, in fact none of our current space craft are looking for life in our solar system..