<p>From observation of stars we know that there are many types of stars that evolve over time and change and this known as <a href="https://en.wikipedia.org/wiki/Stellar_evolution" rel="nofollow noreferrer">stellar evolution</a>. Over time a star changes in its size and in the intensity of its radiation.</p>
<p>Based on our observation of other stars, what estimate can be made of the time remaining before changes in the sun's intensity would render the earth uninhabitable?</p>
<p>Note that my question is about <strong>observation of the intensity of radiation from other stars during their evolution</strong> (is that even measurable?). This is not a question about terrestrial climate effects.</p>

CC BY-SA 4.0
2022-11-20T03:19:58.450Z
See, e.g., https://phys.org/news/2016-05-earth-survive-sun-red-giant.amp
Jon Custer
CC BY-SA 4.0
2022-11-20T03:52:09.550Z
@JonCuster I would imagine the intensity of the sun would begin changing way before it became a red giant. I mean the climate just a few hundred thousand years ago was much different than it is now. Even 10,000 years ago there were hippos living in the Thames.
Tyler Durden
CC BY-SA 4.0
2022-11-20T09:07:42.353Z
The mean behaviour of the Sun is well understood and is unlikely to be the determining factor in how inhabitable the Earth is. Given that the Earth may become uninhabitable on a very short timescale (unless humans are wiped out) I think this is very much an opinion-based question.
ProfRob
CC BY-SA 4.0
2022-11-20T16:48:53.053Z
I don't understand the question, following the edit.  There gradual increase in brightness is not directly measurable, but well and confidently modelled.  If this is not about "terrestial climate affects", then how can you ask about rendering the earth uninhabitable. It is the effect of the sun on the atmosphere that renders the planet uninhabitable.
James K
CC BY-SA 4.0
2022-11-20T16:58:48.003Z
You might have to work in upper and lower bounds.  "Uninhabitable" is basically saying "evolution fails to win," which has historically been a very poor bet because evolution has out-witted our analysis many times.  This leads to needing to change the environment quite radically to make the planet uninhabitable.  On the other than, there are many who argue that the system is actually far more fragile than that, and it would take very little to destroy life as we know it.  The range between the lower and upper bounds could be quite wide indeed!
Cort Ammon
CC BY-SA 4.0
2022-11-20T18:11:21.857Z
How can a question about habitability not be about climate effects? Please elaborate. The last paragraph as is now makes this question completely unclear and unanswerable in my eyes.
planetmaker
CC BY-SA 4.0
2022-11-20T18:15:49.113Z
Before the edit it looked to me like  a good question with a reasonable answer by JamesK
planetmaker
CC BY-SA 4.0
2022-11-20T19:59:03.400Z
The age of stars is judged by their change in luminosity, not the other way around.
ProfRob
CC BY-SA 4.0
2022-11-21T01:19:39.940Z
@ProfRob Ok, maybe that is an answer. To what degree of detail can we describe stellar evolution? If it is just too approximate, then maybe there is no way to tell when the sun might decrease in intensity enough to be significant. So, maybe the answer is "we have no way to know as of yet".
Tyler Durden
CC BY-SA 4.0
2022-11-21T02:28:12.870Z
@Tyler Decrease? The Sun is increasing in luminosity as it ages.
PM 2Ring
CC BY-SA 4.0
2022-11-21T02:33:40.933Z
@PM2Ring I would expect the radiation from the sun decreases over time. I mean just since Roman times 2000 years ago, the earth seems to be receiving less energy from the sun.
Tyler Durden
CC BY-SA 4.0
2022-11-21T02:46:33.680Z
https://en.wikipedia.org/wiki/Sun#Main_sequence The Sun is gradually becoming hotter in its core, hotter at the surface, larger in radius, and more luminous during its time on the main sequence: since the beginning of its main sequence life, it has expanded in radius by 15% and the surface has increased in temperature from 5,620 K (5,350 °C; 9,660 °F) to 5,777 K (5,504 °C; 9,939 °F), resulting in a 48% increase in luminosity from 0.677 solar luminosities to its present-day 1.0 solar luminosity.
PM 2Ring
<stellar-evolution>
What estimate can be made of the time before a change in the Sun's intensity would make the earth uninhabitable?
Tyler Durden
# What estimate can be made of the time before a change in the Sun's intensity would make the earth uninhabitable?

(Asked by: username_0 on 2022-11-20)

From observation of stars we know that there are many types of stars that evolve over time and change and this known as [stellar evolution](https://en.wikipedia.org/wiki/Stellar_evolution). Over time a star changes in its size and in the intensity of its radiation.

Based on our observation of other stars, what estimate can be made of the time remaining before changes in the sun's intensity would render the earth uninhabitable?

Note that my question is about **observation of the intensity of radiation from other stars during their evolution** (is that even measurable?). This is not a question about terrestrial climate effects.

**Tags:** stellar-evolution
> **Comments:**
> **username_1**: See, e.g., https://phys.org/news/2016-05-earth-survive-sun-red-giant.amp  
> **username_0**: @JonCuster I would imagine the intensity of the sun would begin changing way before it became a red giant. I mean the climate just a few hundred thousand years ago was much different than it is now. Even 10,000 years ago there were hippos living in the Thames.  
> **username_2**: The mean behaviour of the Sun is well understood and is unlikely to be the determining factor in how inhabitable the Earth is. Given that the Earth may become uninhabitable on a very short timescale (unless humans are wiped out) I think this is very much an opinion-based question.  
> **username_3**: I don't understand the question, following the edit.  There gradual increase in brightness is not directly measurable, but well and confidently modelled.  If this is not about "terrestial climate affects", then how can you ask about rendering the earth uninhabitable. It is the effect of the sun on the atmosphere that renders the planet uninhabitable.  
> **username_4**: You might have to work in upper and lower bounds.  "Uninhabitable" is basically saying "evolution fails to win," which has historically been a very poor bet because evolution has out-witted our analysis many times.  This leads to needing to change the environment quite radically to make the planet uninhabitable.  On the other than, there are many who argue that the system is actually far more fragile than that, and it would take very little to destroy life as we know it.  The range between the lower and upper bounds could be quite wide indeed!  
> **username_5**: How can a question about habitability not be about climate effects? Please elaborate. The last paragraph as is now makes this question completely unclear and unanswerable in my eyes.  
> **username_5**: Before the edit it looked to me like  a good question with a reasonable answer by JamesK  
> **username_2**: The age of stars is judged by their change in luminosity, not the other way around.  
> **username_0**: @ProfRob Ok, maybe that is an answer. To what degree of detail can we describe stellar evolution? If it is just too approximate, then maybe there is no way to tell when the sun might decrease in intensity enough to be significant. So, maybe the answer is "we have no way to know as of yet".  
> **username_6**: @Tyler Decrease? The Sun is increasing in luminosity as it ages.  
> **username_0**: @PM2Ring I would expect the radiation from the sun decreases over time. I mean just since Roman times 2000 years ago, the earth seems to be receiving less energy from the sun.  
> **username_6**: https://en.wikipedia.org/wiki/Sun#Main_sequence The Sun is gradually becoming hotter in its core, hotter at the surface, larger in radius, and more luminous during its time on the main sequence: since the beginning of its main sequence life, it has expanded in radius by 15% and the surface has increased in temperature from 5,620 K (5,350 °C; 9,660 °F) to 5,777 K (5,504 °C; 9,939 °F), resulting in a 48% increase in luminosity from 0.677 solar luminosities to its present-day 1.0 solar luminosity.  

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## 0 answers

