What is "Earth-like"?

[Forty Two]

Average temperature on Venus: 462 deg C. Very Earth-like...

Eartlike just means it's a rocky planet composed of silicate rocks and metals. So, yes, Venus is Earthlike.

[pErvinalia]

For the third time: The probability is not calculable on empirical grounds. Haven't we agreed on this some time ago?

I would prefer to say that the probability is not presently calculable on any grounds, empirical or otherwise.

If you can name a way of calculating probability of a physical event non-empirically, I'd be all ears.

[Forty Two]

Why would I do that?

[pErvinalia]

Average temperature on Venus: 462 deg C. Very Earth-like...

Eartlike just means it's a rocky planet composed of silicate rocks and metals. So, yes, Venus is Earthlike.

Back in the day, Venus probably had more earth like temperatures and liquid water. It may have actually had life that has long since evaporated.

[pErvinalia]

Why would I do that?

Because you named an "otherwise" case. What is that case?

[Forty Two]

You continually have this inability to read plain English. I think it's your propensity to decide what someone really means, rather than simply letting a person speak for himself.

"I would prefer to say that the probability is not presently calculable on any grounds, empirical or otherwise."

Hermit used the qualifier "empirical" to modify the word "grounds." He said that the probability could not be determined on "empirical" grounds. That leaves open the logical possibility that Hermit allowed for there to be other grounds, non-empirical, on which the probability could be determined. I don't know what they might be, as they were not specified. I don't think there are any other grounds.

So, saying that the probability is not presently calculable on any grounds, empirical or otherwise, sews up the idea that it cannot be calculated at all. if Hermit believes there is another ground, besides empirical, on which the probability can be based or found, then he can certainly say what that ground is.

If Hermit was not allowing for a ground other than empirical to exist, then his use of the qualifier is unnecessary. He could simply have said, "for the third time, the probability is not presently calculable."

He his failure to include the word "presently" or its equivalent renders the statement vague in terms of whether he was saying the number is inherently incalculable, or whether he is saying we don't have enough information yet from which to glean it.

[pErvinalia]

blah blah... As usual, you can't own up to your own words. You wrote: "I would prefer to say...". Those were your preference for words that followed. If you accept that there isn't any other way of calculating the probability of a physical event besides empirically, then why did you say that?

[Hermit]

For the third time: The probability is not calculable on empirical grounds. Haven't we agreed on this some time ago?

I would prefer to say that the probability is not presently calculable on any grounds, empirical or otherwise.

Yes, presently. At the moment we have insufficient empirical data for any such calculation to be taken seriously.

As for calculations based on other grounds, they have been made. In the matter of extraterrestrial life, for instance, Harlow Shapley speculated on the number of inhabited planets in the universe, saying "The universe has 10 million, million, million suns (10 followed by 18 zeros) similar to our own. One in a million has planets around it. Only one in a million million has the right combination of chemicals, temperature, water, days and nights to support planetary life as we know it. This calculation arrives at the estimated figure of 100 million worlds where life has been forged by evolution." Speculations, such as this one, of course can only be determined as right or wrong on empirical grounds, and sometimes, such as the neo-Platonists' assertion that a major, as yet undiscovered continent must exist in the southern hemisphere turn out to be right for the wrong reason. They were of the opinion that what became known as Australia must exist to balance planet earth.

[pErvinalia]

A report the other day suggested that the estimate of the number of galaxies in the universe is out by a factor of 10 (or it might have been 100). Previous estimates were 100 billion. The new estimate is in the trillions (can't remember the exact estimate).

[JimC]

I suspect that the chances of life arising on a given planet might well be high enough to expect a reasonable number of life-bearing planets per galaxy, but that the chance of intelligence evolving from that life might be very much lower, to the point where it galaxies may only contain a handful of technologically advanced species, if any at all.

Speculative, I know, but a counter to the unthinking view that intelligence almost inevitably emerges, given multi-cellular life.

[rainbow]

Did you not even bother reading the OP at the beginning of this thread:

Can you point to a statement wherein I disagree with Miriam Kramer's article?

You seem to be working with a definition of "earth-like" I had not hitherto encountered.

Had you read the article, you'd know exactly where such a definition is being used.

Let's have a look at the context, shall we?

Oh yes, lets look at the context.
Please make your point. You seem to have a problem with the definition of Earth-like as put in Miriam Kramer's article.
Feel free to explain why you don't think that Venus fits the wider definition with which she has a problem.

Enlighten us.

[Hermit]

You seem to have a problem with the definition of Earth-like as put in Miriam Kramer's article.
Feel free to explain why you don't think that Venus fits the wider definition with which she has a problem.

Kramer's definition of earth-like can be gleaned from the article's title. "Stop describing a planet as 'Earth-like' unless it really is". In the body of the text she explains that from what we do know about Proxima b, we cannot conclude that it is an Earth-like planet. There's a section of the article that makes her intention perfectly clear. "Not Earth-like". Until we know if the planet has a suitable atmosphere and a magnetic field, both of which are necessary for life, we cannot conclude that it is Earth-like, that is capable to support life-forms. As Kramer puts it: "Proxima b is far from being a twin of our planet. Scientists aren't sure what kind of atmosphere it has or even if it's able to support a magnetic field, two things that it would need to sustain habitability in orbit around its active, flaring star. We simply don't know if it can support water, life or much of anything on its surface at all." Thus, to describe the newly discovered planet as Earth-like is just another one of those beatups the media are so fond of in order to maximise readership and through it advertising revenue.

I don't have a problem with what she wrote in the context she wrote the article. Discovery of the century, my foot. Proxima b is just another one of the well over 3000 exoplanets that have been discovered since 1988. Beginning in 2009 the Kepler space telescope alone has found more than two thousand.

[rainbow]

Good.
So now you've cleared up you confusion, can we move on?

[Brian Peacock]

Frank Drake's equation attempts to estimate a probability based on a set of logical assumptions.



As such it acts as a motivator to firm-up those assumptions empirically.



Of course, the Fermi Paradox somewhat undermines Drake's optimism.

[Sean Hayden]

I prefer to explain the lack of evidence by invoking The Wisdom of The Laws of The Failed Imagination, which states among other things, that it's always in the last place you look.