Shouldn't goldilocks zones shift over time?

Submitted by LaRoara42 t3_10ndybj in askscience

I might be misunderstanding the concept, but:

If the goldilocks zone is just the sweet spot away from a star that could sustain life, is it possible for that zone to shift as the star goes through different life stages? Or possibly life might evolve differently at different distances?

Does this have a place in our modern understanding?

Update/Follow Up Question: There seems to be a consensus in the thread that this is a valid concept. 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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sprawler16 t1_j68qi6e wrote

Yes, different stars are different sizes and output different amounts of radiation, light, heat, and gravitational pull. All of these things affect the planets and celestial bodies around them. And stars in their final days balloon outwards as they expend the last hydrogen inside of them. This also shifts the Goldilocks zone outward.

So yes.

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VoilaVoilaWashington t1_j6a0lpl wrote

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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athomasflynn t1_j694k97 wrote

It is already a part of the calculation. Different types of stars have different goldilocks zones so if a star transitions between types the zone placement will be different afterwards.

If you're asking would life on a specific planet survive the transition, the answer is no, almost certainly not. Take our star and Earth as an example. It's the only one we have. In 5 billion years when our sun transitions to a red giant its diameter will massively increase but its mass will remain the same. So the planetary orbits relative to the center of the sun will remain the same. There's a good chance that the Earth will be consumed entirely. Wherever the new goldilocks zone is, you can be pretty certain that it's not inside the star.

This type of problem will be similar with most of these transitions. If the stars diameter and energy output change but the orbits of the planets surrounding it do not, it's highly unlikely that a planet would be inside it both before and after the transition. Probably impossible but I don't have the time or data to prove that.

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Harbinger2001 t1_j6aihf0 wrote

Before the Sun goes red giant, its temperature will rise enough for Earth to be out of the goldilocks zone. Currently estimated at 1 billion years.

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Harbinger2001 t1_j6ai2gv wrote

The Sun is heating up. In 1 billion years the Earth will no longer be in the Goldielocks zone. So we probably have about 500 million years before it becomes a real issue for humans. Hopefully by then we should be able to either move the Earth as the zone moves, or build space habitats.

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GeneralBacteria t1_j6cm8s2 wrote

600 million years before the Earth becomes too hot to support the carbon cycle.

Safe to say humans will have problems long before that.

although even 1000 years is a very long time with our current rate of technological progress. credible plans exist to change the orbit of the Earth to keep us in the Goldilocks zone.

edit: for the doubters/downvoters.

https://lifeboat.com/ex/lets.lift.the.earth

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PD_31 t1_j693bqu wrote

The Goldilocks zone will depend on the star's temperature and therefore how much its energy output is, so yes over time it will shift. To take an extreme example, our Sun's late life stage will see it expand and swallow up the earth; clearly we will no longer be in the zone when that happens.

So yes, the zone will shift but the lifespan of a star is so long that it won't change on a human (or even humanity's) timescale for most stars.

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Varsect t1_j69d4ga wrote

Yes. It happens all the time. During the Red Giant phase, the Earth will either become a bunch of new thermal energy to add into the system or become the new Mercury and the goldilocks zone will have shifted to somewhere between Saturn and Uranus. It will also be influence by temp too but anyways,it is also predicted that Titan and Europa could hypothetically reach levels tolerant enough to reach Earth's current temp.

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spideywat t1_j6acp8z wrote

The only possibility that I have heard is perhaps Mars is where life started, got blasted off by an asteroid impact, fragments came to earth and restarted here as Mars became inhospitable. That was decades ago and we have done lots of studies on Mars since, so the plausibility of that I don’t really know.

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starmartyr t1_j6cp14w wrote

There is the panspermia hypothesis. The idea is that microbial life could somehow be ejected from its home planet by something like a meteor impact. So you have a rock floating through space that contains a dormant single-cell organism. It floats around space for millions of years until it eventually lands on a planet with a habitable atmosphere. The organism evolves over millions of years and eventually, the planet is covered in diverse life forms. That could have happened on Earth. While this theory is interesting it doesn't do much to answer the question of the origin of life. It just passes the buck to somewhere else in the universe.

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LaRoara42 OP t1_j6aur2q wrote

It's fun to wonder even if we can't know

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warrenv02 t1_j6dfysc wrote

I think the article below best answers your question. Think of the earth’s distance from the sun as fixed but the habitable zone is expanding outwards.

I can’t speak to evolution at all.

For your follow up question in a sci fi way if Venus was in the habitable zone before earth yes we would need to move outward in the solar system.

I think the most fascinating fact in the article is that earth has already moved through 70% of the habitable zone.

https://www.nature.com/articles/nature.2013.13788

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RShArren t1_j68rgp8 wrote

It is totally possible. As you correctly noticed, at different stages of the star's evolution its spectral energy distribution changes, meaning that at some stages most energy is emitted in the infrared range, and at other stages - in visible, ultraviolet, etc. Depending on the planet's atmosphere composition, it will absorb/reflect/transmit different wavelengths with different efficiency. Atmosphere composition, in turn, depends on many factors, such as geological age of the planet, its initial composition, amount of water, presence of life, etc. In other words, the surface temperature on the planet depends on many factors that can and do change as the central star and the planet itself evolve. Consequently, the Goldilocks zone can move.

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Inverted-pencil t1_j6cjet7 wrote

This is actually nonsense since the sun is not actually hot, the surface is but not the space around it. The sun rays hitting the atmosphere creates heat. Its actually very cold high up in the earth atmosphere where oxygen is low the sun is not heating up space. As long you have liquids distance don't matter much it could support life.

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slomobileAdmin t1_j6drsay wrote

Assume that is true. A planet of equal size farther from the sun receives fewer total rays because that is how angles work. Yet solar rays are considered effectively parallel due to the extreme distance. So is it the apparent size of the sun in the sky that makes the difference? If distance doesn"t matter, we would be heated by all the stars in the sky and there would be little difference between day and night temperature. Is there a large difference between day and night? This illustrates the problem with describing things using generalities.

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Inverted-pencil t1_j6n66hv wrote

I did not mean that distance did not matter at all. But considered that a planet whit lots of volcanic activity and thich atmosphere could do fine at a long distance or perhaps even without a sun at all.

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slomobileAdmin t1_j6o4zhe wrote

Ok, I didn't know where you were going with "As long you have liquids" but think I get it now.

You make a good point about the radiated energy of the sun only being converted to heat once it strikes matter. Orbiting high energy reflectors could make a planet habitable closer to a sun. On distant planets, low altitude energy absorbers which reradiate IR could raise surface temps enough to boost biology which conditions the atmosphere favorably.

It wouldn't make much difference on a cosmological scale, but to an intelligent species facing extinction, it might be something they/we would attempt at the edges of goldilocks zones to eek out a few more generations.

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