How big will the sun get when the seas begin to boil?

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Discussion Overview

The discussion revolves around the future size and brightness of the Sun as it approaches the end of its life cycle, particularly in relation to the boiling of Earth's seas. Participants explore the implications of solar evolution and its effects on Earth over billions of years, touching on theoretical aspects of stellar life cycles and planetary conditions.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires about the visual size and brightness of the Sun when Earth's seas begin to boil, indicating a lack of technical knowledge regarding astronomical measurements.
  • Another participant estimates that in about 3.6 billion years, the Sun's output will increase by approximately 40%, leading to the evaporation of Earth's seas and a radius increase of about 18%, with no significant change in color.
  • A different participant notes that the Sun will not yet be a Red Giant at the time when the seas boil, which is expected to occur around 5 billion years from now, at which point the Sun's diameter could reach 2 astronomical units (au).
  • This participant claims that the apparent size of the Sun will increase dramatically, from about 0.5 degrees to approximately 90 degrees, making it appear over 200 times larger than it does currently.
  • Another participant suggests that the end of life on Earth will occur when the oceans dry up, which they argue will happen long before the Sun undergoes more dramatic changes.
  • One participant expresses confusion about the mention of the Red Giant phase, indicating a possible misinterpretation of earlier statements.

Areas of Agreement / Disagreement

Participants express differing views on the timeline and implications of the Sun's evolution, with no consensus on the specifics of when significant changes will occur or their effects on Earth.

Contextual Notes

There are assumptions regarding the distance of Earth from the Sun over time and the conditions that lead to the boiling of the seas, which remain unresolved. The discussion also reflects varying levels of understanding of astronomical concepts among participants.

Khantazm
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First of all, I apologize if this is not the right place - it's my first post (although I've lurked for a while), so... er.

Doomsday question. I'd like to know how big the sun will get - visually (but please without °, I am not educated enough to understand those) - at the end of its life cycle at the moment when the seas on Earth begin to boil. And also how bright and what color the light will be, if possible.
 
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After some poking around, here's what I came up with as a rough estimate. In about 3.6 billion yrs the Sun will have slowly increased its output by ~40%, the seas will evaporate and Earth becomes another Venus. The radius of the Sun will have increased by ~18%. Its color will not appreciably changed.
 
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Thank you very much. Although, that's not much potential for drama, is it?:smile:
 
Khantazm said:
Thank you very much. Although, that's not much potential for drama, is it?:smile:

No, but at that point in time the Sun will not be a Red Giant yet. That will happen at approximately 5 billion years from now. It is expected that the diameter of the Sun will be 2 au, which means its radius will be about 1 au, so it will extend out to Earth's current orbit.

The apparent size of the Sun will increase from about 0.5 degrees (the apparent size that it is now) to about 90 degrees, an increase of over 200 times. So it will appear about 200 times as big as it does now.

Now that is assuming the Earth is still near 1 au from the center of the Sun. If we assume the Earth will get further away over time as the Sun loses mass, the Sun will appear slightly smaller.
 
Drakkith said:
No, but at that point in time the Sun will not be a Red Giant yet.

His last statement suggested to me that he's writing a story. The end of life on Earth will come when the oceans dry up - loooong before the sun starts doing anything more ... dramatic.
 
DaveC426913 said:
His last statement suggested to me that he's writing a story. The end of life on Earth will come when the oceans dry up - loooong before the sun starts doing anything more ... dramatic.

Hrmm. I could have swore I saw "Red Giant" somewhere in the post...my apologies.
 

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