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How Do We Know How Old the Sun really is and do We really Know its Ultimate fate ??

BAYLOR

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#1
Consensus say 5 billion years , but do we know that with certainty? Perhaps the sun might be older then we think?

The reason I'm staring this thread is, that I was thinking about something I heard with regard to the sun, that in billion years or so the sun would be hotter then it is now , solar output would increase from 10 to 20 percent( not sure on that number ) but either number would not be beneficial to life on earth. At that point, the earth might be rendered uninhabitable by the increased solar output. And thought its life the sun has converting Hydrogen to helium as and that 10 billion year the sun turn red an cool off and expand consuming the inner planets up to an including Mars . ( one wonders how the expanded sun will affect Jupiter and the surviving planets. A billions after the the suns outer layers will dissipate into space leave a cooling white dwarf which will ultimately dim into a black hole. Thats the prediction based on current scientific understanding. Ints also unlikely that the sun will ever have nova pahse given that its the wrong type of star with an insufficient mass .

Thoughts ?:unsure:
 

Overread

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#2
I think that when science starts talking of predictions of things to come in billions of years and things that came before in billion of years there's a LOT of scope for errors, mistakes, miss interpretations and general confusion. And that's before we've even got to the dumbed down versions that summarise these results which are often all that is presented by the media to the general public.

Also don't forget that in areas of theory there are very rarely only single theories. There will be popular and unpopular ones within a sea of choices. So again there's even more scope for complexity in the potential answers. Furthermore the media science is often years behind the real science. Take black holes; most lay people consider Stephan Hawking to be the current leading expert, when in fact he's but one of many and his theories are not as strongly held as they once were (least that was my last hearing a few years back, could be its all changed again).


I'd say that science doesn't know these answers; heck its got enough trouble predicting the weather next week. So yeah there are theories, but I'd wager they are the sort that are in constant review and likely change with each new observation in space
 

HanaBi

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#3
I took up amateur astronomy 30 or 40 years ago, purely through related TV shows like Patrick Moore's "Sky at Night", Carl Sagan's "Cosmos", James Burke's "Connections" and the various "Horizon" programs on the BBC. I was really interested in our solar system and how it came to being, and the scientific research & theory back them seemed so sure of itself that one had to believe in it. Because after all, they are the experts aren't they!?

But over the years a lot of that theory has been amended/appended, or has fallen by the way side completely as the technology of understanding what is happening out there has improved over time. But that still doesn't mean that because we know more today that our understanding of the Sun's existence, for example, is absolute. There's still a lot of guess work going on, and one wonders if we will ever know for definite about how the Universe really ticks.

I am still waiting on someone to find-fault in Einstein's E=MC² equation. If they do then a lot of cosmological theory will collapse!
 

Stephen Palmer

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#4
The sun gets slightly hotter as it gets older.
This fact led James Lovelock to ponder why the average temperature on Earth's surface was about the same over 4 billion years >> Gaia Theory.
In about 1 billion years time (estimates vary) the Earth's CO2 temperature regulation will fail.
Then it gets toasty pretty quick.
See also this...
 

BAYLOR

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#5
The sun gets slightly hotter as it gets older.
This fact led James Lovelock to ponder why the average temperature on Earth's surface was about the same over 4 billion years >> Gaia Theory.
In about 1 billion years time (estimates vary) the Earth's CO2 temperature regulation will fail.
Then it gets toasty pretty quick.
See also this...
What about moving the earth further away from the sun as it ages?
 

Serendipity

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#6
...
I am still waiting on someone to find-fault in Einstein's E=MC² equation. If they do then a lot of cosmological theory will collapse!
**warning geek at play here **

This is just the kinetic energy i.e. there is no potential energy involved in the derivation of this equation. So if the body at rest has potential energy, then this equation may not apply...
 

Mirannan

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#7
The age of the Solar System can be inferred from age measurements of things like Lunar rocks, using radioactive decay as a clock. As for predicting the future of the Sun; well, the predictions are based on known physics and (to some extent) can be checked by studying a large number of other stars - including samples of such stars which are known to be of similar ages because they are all in a cluster which was formed (roughly!) at the same time. Examples; Pliades and Hyades.
 

Vertigo

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#9
When the sun expands it will only reach just about as far out as Earth's orbit - so it's toast for Mercury, Venus and us, though it has been speculated that as the sun expands the increased solar wind might just push the Earth out enough that it doesn't get consumed. However it won't be enough for our survival and besides we will have had it long before due to the increased solar heat. As far as the other planets go there will probably be almost no effect; the Sun will still be approximately the same mass so the orbital dynamics don't change and they (or at least Jupiter onwards) are far enough away that the increasing and decreasing solar temperature as the sun ages will probably have little impact until it really gets cold.
 

BAYLOR

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#10
Never heard of that. Try googling it!
Im think that millions of years from now if mankind is still around( and I think it's possible we might be)we'll have the technology to move the earth. We might even have enough tech and know how to reengineer the sun and extend it's life and maybe prevent it from going red( wouldn't that be wonderful).
 

BAYLOR

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#12
I think the latter is unlikely; when the hydrogen is burnt it's burnt.
Unless we can find a means to convert it from Helium ash back into Hydrogen. Millions of years hence , that kind thing might be in the realm of possibilities.
 

BAYLOR

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#14
I think if we were capable of doing something like that then we'd really not have much need of the sun any longer...;)
That is an excellent point. :)

But maybe mankind will have some kind of nostalgia for keeping Sol alive. :D
 

Venusian Broon

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#15
What about moving the earth further away from the sun as it ages?
Yes it probably should in general. In the same way the moon is getting further away from the Earth, because of gravitational tidal forces causing 'friction' means that the orbital speed is forever slowing. A slower orbit is a larger orbit.

In the Sun-Earth case this could be the case as well, as the Earth is also in an elliptical orbit there is also tidal forces caused by the changing gravity of the Sun in different parts of the orbit, causing a tidal bulge and resultant friction that slows the orbit.

There may be other factors that accentuate or hinder this though.

It's not much - apparently 15 cm a year. So in a billion years the Earth should be orbiting 150,000 km further out (not much compared our current orbit of ~150 million km
 

Venusian Broon

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#16
the Sun will still be approximately the same mass so the orbital dynamics don't change and they (or at least Jupiter onwards)
There does seem to be significant loss in mass with some red giants - however that might be at the end of the red giants life span and not for the initial expansion to ~200x radius. Essentially the sun can no longer hold onto it's outer portions as well, it seems. I'm reading of mass drops of ~50%. If that was the case then the orbit of the Earth would be dramatically increase it's orbit, to my calculations about 1.8x further away (and putting us reasonably safely away from the edge of the sun....however that might be 1) at the end of the Red Giant phase, so a billion years skimming the surface and 2) we'd get a face load of ejected sun)
 

chrispenycate

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#19
**warning geek at play here **

This is just the kinetic energy i.e. there is no potential energy involved in the derivation of this equation. So if the body at rest has potential energy, then this equation may not apply...
Potential energy has no actual existence, just because it is potential, not actual. If, for example, a star had a largish percentage of its mass well away from its core, held there by the pressure generated by its own temperature, then it would have potential energy of position, but this energy would have no mass unless the star suddenly cooled down, and it became infall energy. At which point it is kinetic, and follows all the rules (not that this situation is likely to arise, or should that be 'collapse' very often. Stars are remarkably good about long-term stability). If you consider a few billion megatons of hydrogen as 'potential fusion energy', then the equations still work out the same if it's fusing or cold.
 

hitmouse

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#20
**warning geek at play here **

This is just the kinetic energy i.e. there is no potential energy involved in the derivation of this equation. So if the body at rest has potential energy, then this equation may not apply...
Not really. The equation simply describes the fundamental equivalence between mass and energy. It is basic and it always applies to everything.
 
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