More Earth-like planets found
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16-07-2017, 07:15 AM
RE: More Earth-like planets found
The Drake Equation and the Fermi Paradox lead me to believe, without fail, intelligent life destroys itself. We're on deck.
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16-07-2017, 07:17 AM
RE: More Earth-like planets found
Let me see if I can explain this again. A planet exactly like Earth in the same orbit, around a star like our sun would not support life. Our planet is a lucky accident due to a collision with another planet. I assume that a real list would not be dependent on such an extremely rare occurrence.

So, our Earth is not a reference planet; it's too small and too close to the sun. Without the luck of the collision the Earth would have been scoured dry by the solar wind, like Venus. You need a larger planet, large enough to have a well developed magnetic field. This requires an active, molten core. Venus doesn't have this and neither does Mars. The Earth wouldn't have an active core if not for that lucky collision. This magnetic field keeps the solar wind from removing the water. However, if the planet is larger then it retains more heat so it has to be farther from the sun. And, more distance means that the solar wind is weaker than at Earth's orbit.

Unfortunately, if the planet is too large and too distant then it actually retains gas from the solar wind and becomes enveloped in gas. This occurs at about 3 Earth masses. These are often called mini-Neptunes. Life is not possible on a planet without water and not possible on a planet shrouded in hydrogen gas. It isn't possible on a planet that orbits a gas giant and doesn't seem to be possible in a binary star system. It doesn't seem possible with a star larger, smaller, more or less radiant than our sun. This excludes something like 99% of all star systems because they either have red dwarf stars or binary systems. Then you exclude highly variable stars and stars with near orbit gas giants. You probably have to exclude stars without outer orbit gas giants. And you have to have a molten, nickel iron core. We've probably now exluded 99.99% of star systems. I suppose that would still leave about 20 million stars in our galaxy. But you also have to exclude stars in dense clusters and in the dense galactic core. So, maybe 250,000 stars.

For example, Gliese 581 does not appear to be a real candidate because the star is a red dwarf. The star's output is only 1.3% of our Sun. Since intensity is relative to the inverse square of the distance a planet would need to be about 1/8th the distance of Earth's orbit. Good so far but gravity is also inversely proportionate to the square of the distance. And, unfortunately, Gliese is about 1/3rd the mass of our Sun. You're going to end up with solar, tidal forces about 20 times stronger than Earth experiences which would lead to tide locking. You won't find life on a tide-locked planet.

It isn't hopeless yet but we really haven't found any likely candidates. Maybe James Webb will find something.
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16-07-2017, 07:36 AM
RE: More Earth-like planets found
Does the fact that we have found life in incredibly unlikely locations on earth soften your position at all? Do you believe that all life on earth has a single common ancestor or is it possible that different life originated at different times and places on earth? I'm just at the pop-science TV documentary level of knowledge to let you know what you're dealing with here lol.
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16-07-2017, 08:29 AM
RE: More Earth-like planets found
(16-07-2017 07:36 AM)ImFred Wrote:  Does the fact that we have found life in incredibly unlikely locations on earth soften your position at all? Do you believe that all life on earth has a single common ancestor or is it possible that different life originated at different times and places on earth? I'm just at the pop-science TV documentary level of knowledge to let you know what you're dealing with here lol.

Organic material is very common; we have found it in comets, for example. I'm not sure though what you mean by "single common ancestor". Are you referring to a particular strand of XNA or are you talking about one proto-cell or are you further along to fully functioning cells? It looks like all life on Earth can be traced to a common ancestral cell going back about 3.5 billion years. However, that means that it was the surviving lineage rather than the only lineage. There could have been cell lineages that were replaced with more robust lineages. In other words, this would not exclude multiple origins.

We have found bacteria in unlikely places such as deep underground and in the Antarctic but the bacteria didn't originate there.
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16-07-2017, 08:46 AM
RE: More Earth-like planets found
I guess I meant the common ancestral cell.

A part of me wants to jump out and say yeah but maybe life can evolve in extremely different circumstances but there's not much point getting into every imaginable possibility. We only have one example to go on so I dig what you're saying. Still, it's fun to dream about the what ifs. I don't remember who said it but I like the quote that we're either alone or we're not and they're both scary as hell.
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16-07-2017, 09:05 AM
RE: More Earth-like planets found
(16-07-2017 07:15 AM)ImFred Wrote:  The Drake Equation and the Fermi Paradox lead me to believe, without fail, intelligent life destroys itself. We're on deck.
And neither of those has been proven, so you can relax. (The Fermi "Paradox" is just silly.)
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16-07-2017, 09:10 AM
RE: More Earth-like planets found
It's never very relaxing to be told to relax by someone known as Gawdzilla.
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16-07-2017, 09:23 AM (This post was last modified: 16-07-2017 09:28 AM by scientious.)
RE: More Earth-like planets found
(16-07-2017 08:46 AM)ImFred Wrote:  I guess I meant the common ancestral cell.

A part of me wants to jump out and say yeah but maybe life can evolve in extremely different circumstances but there's not much point getting into every imaginable possibility. We only have one example to go on so I dig what you're saying. Still, it's fun to dream about the what ifs. I don't remember who said it but I like the quote that we're either alone or we're not and they're both scary as hell.

There are lots of crazy ideas about alternative life forms. Some of these include:
  • silicon based life
  • liquid methane instead of water
  • groups of single cells forming an intelligent organism
  • aquatic civilization
  • intelligent life with tentacles or without a skeleton
  • intelligent colonies like termites or ants
  • ancestral memory
  • intelligent life much smaller than humans; an intelligent alien you could hold in your hand.
  • intelligent life much larger than humans; an intelligent alien who could hold you in their hand.
  • aliens vastly more intelligent than humans
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16-07-2017, 09:27 AM
RE: More Earth-like planets found
Proving that there are no radio transmissions might take something more involved like building a radio dish array on the far side of the Moon. At least, it might be useful for radio astronomy.
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16-07-2017, 09:27 AM
RE: More Earth-like planets found
(16-07-2017 09:10 AM)ImFred Wrote:  It's never very relaxing to be told to relax by someone known as Gawdzilla.
That's MR. Gawdzilla.

Smartass
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