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VoilaVoilaWashington t1_j6a0lpl wrote

Reply to comment by sprawler16 in Shouldn't goldilocks zones shift over time? by LaRoara42

However!

When scientists talk about a new planet in the goldilocks zone, they're talking about today (or what appears to be today, but might be many years ago). They're looking at a specific sun as it is today, and commenting on that.

Yeah, in a billion years, it will be different. And that's okay.

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LaRoara42 OP t1_j6a8s4q wrote

So...could that mean...we evolved as scientists think we did but maybe we did that on another planet in our our system and had to move to Earth when the goldilocks zone shifted?

....maybe? Even in a "plausible sci fi" way?

Or is the change over too many billions of years to make any sense?

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makary12 t1_j6aaa4q wrote

That would be a nope from chief. My understanding is that the earth has always been in the Goldilocks zone. I think you're severely underestimating the time it would take for the Goldilocks zone to move far enough so that earth is no longer within it. We would definitely know if we changed planets; that is not something that would fly under the radar.

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psymunn t1_j6ba17n wrote

I never understood what would be more fascinating about life originating on another planet rather than earth. It just passes the buck. Also it doesn't explain the rest of the biodiversity we have here

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LaRoara42 OP t1_j6bg7g3 wrote

It's more like humans feel sorta...out of place.

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haysoos2 t1_j6bp1f2 wrote

Not really. Our entire biology and fossil history fits with the diversity of life in Earth.

As multicellular, deuterostome, bilateral, chordate vertebrates, osteichthyans, sarcoptergyians, tetrapods, synapsids, mammals, eutherians, primates, cercopithicoids, hominoids and hominids we have an entire branching and interlinked family history with all of the other life that shares our planet.

For any of that to make sense, that shared history would also have to be extraterrestrial, making the introduction billions of years ago at the very beginning of cellular life, and as such just adds more questions without actually answering anything.

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A_Dapper_Goblin t1_j6cmmom wrote

I feel like this post is getting a lot more hate than it deserves. OP is asking something a lot of people ask. It may be ignorant of a lot of important facts, but asking questions and having them answered is a big part of how you remedy ignorance. OP is clearly trying to do that, and is taking the responses seriously, and changing their view of things as they get new information. That sort of thing should be encouraged.

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EarthSolar t1_j6boylv wrote

When the Sun had just formed its luminosity was ~70% today’s, and so Earth back then would’ve received 70% its current light too. But the thing is, with carbon dioxide and other greenhouse gases, liquid water oceans can exist much further out than we are now. With just carbon dioxide the outer limit is around 40% Earth’s sunlight, so Earth has always been within the habitable zone.

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