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



## BAYLOR (Sep 29, 2017)

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 ?


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## Overread (Sep 30, 2017)

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


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## HanaBi (Sep 30, 2017)

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!


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## Stephen Palmer (Sep 30, 2017)

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...


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## BAYLOR (Sep 30, 2017)

Stephen Palmer said:


> 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?


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## Serendipity (Sep 30, 2017)

HanaBi said:


> ...
> 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...


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## Mirannan (Oct 1, 2017)

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.


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## Stephen Palmer (Oct 1, 2017)

BAYLOR said:


> What about moving the earth further away from the sun as it ages?



Never heard of that. Try googling it!


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## Vertigo (Oct 1, 2017)

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.


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## BAYLOR (Oct 1, 2017)

Stephen Palmer said:


> 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).


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## Vertigo (Oct 1, 2017)

I think the latter is unlikely; when the hydrogen is burnt it's burnt.


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## BAYLOR (Oct 1, 2017)

Vertigo said:


> 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.


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## Vertigo (Oct 1, 2017)

I think if we were capable of doing something like that then we'd really not have much need of the sun any longer...


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## BAYLOR (Oct 1, 2017)

Vertigo said:


> 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.


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## Venusian Broon (Oct 1, 2017)

BAYLOR said:


> 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


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## Venusian Broon (Oct 1, 2017)

Vertigo said:


> 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)


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## Vertigo (Oct 1, 2017)

Yeah, I suspect life on Earth would have become pretty terminal by then!


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## BAYLOR (Oct 1, 2017)

Vertigo said:


> Yeah, I suspect life on Earth would have become pretty terminal by then!



But if you owned stock in company the produces sunblock , you become very rich and then you'd be toast.


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## chrispenycate (Oct 2, 2017)

Serendipity said:


> **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.


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## hitmouse (Oct 3, 2017)

Serendipity said:


> **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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## Vertigo (Oct 3, 2017)

hitmouse said:


> Not really. The equation simply describes the fundamental equivalence between mass and energy. It is basic and it always applies to everything.


In fact come to think about it, is it not really describing the ultimate potential energy? It's certainly not describing kinetic energy as it does not involve the velocity of the mass and kinetic energy is surely a function of mass and (relative) velocity? Maybe I'm wrong but that's how I understood it.


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## hitmouse (Oct 3, 2017)

Vertigo said:


> In fact come to think about it, is it not really describing the ultimate potential energy? It's certainly not describing kinetic energy as it does not involve the velocity of the mass and kinetic energy is surely a function of mass and (relative) velocity? Maybe I'm wrong but that's how I understood it.


Don't confuse C with kinetic energy or velocity. It is simply a universal constant. E is proportional to M, but e=mc^2. Think about the energy released in  a nuclear reaction.


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## Vertigo (Oct 3, 2017)

hitmouse said:


> Don't confuse C with kinetic energy or velocity. It is simply a universal constant. E is proportional to M, but e=mc^2. Think about the energy released in  a nuclear reaction.


No, that's why I said it _*doesn't*_ describe kinetic energy, what it describes is the potential energy available if it's completely converted to energy.


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## Venusian Broon (Oct 3, 2017)

Vertigo said:


> In fact come to think about it, is it not really describing the ultimate potential energy? It's certainly not describing kinetic energy as it does not involve the velocity of the mass and kinetic energy is surely a function of mass and (relative) velocity? Maybe I'm wrong but that's how I understood it.



Potential energy is the energy of a particle that it possesses because of it's position relative to other particles. Usually we think of a particle and it's relationship to a field, where the field has been generated by another particle. e.g. gravitational field and mass. 

E=mc^2 is a truncated term that comes from the Relativistic Energy-mass equivalence. (As Hitmouse stated!) It comes about because the conservation of mass didn't work in special relativity and therefore it was required to 'fold in' the conservation of Energy also to make it work. Thus one finds that the universe can convert mass to energy and energy to mass.

The full term is     
	

	
	
		
		

		
			





Now if we take the frame of reference of any individual particle, called the centre of mass frame I think, it is stationary therefore it has zero velocity and p=0 and the familiar E = m_0 c ^2 drops out. However if we look at the particle from another frame of reference - say a moving frame - then we also need, in order to be exact, to add the momentum term.

At no point have I talked about any other particle or field to derive this equation thus it is not a potential energy. Or at least potential energy as defined by physics.

I see where you are coming from, I think....but because energy and mass are equivalent and these are conserved, in a closed system the value of 'E' is a constant. On the other hand, a particle in a field can vary the total energy of the system by moving in the field, and this is what we mean by potential energy.


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## hitmouse (Oct 3, 2017)

Vertigo said:


> No, that's why I said it _*doesn't*_ describe kinetic energy, what it describes is the potential energy available if it's completely converted to energy.


Apologies for misreading your post. What Venusian Broon said about potential energy, though. By textbook definition, a bit different to the energy implied by E:M equivalence.


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## Vertigo (Oct 4, 2017)

Venusian Broon said:


> Potential energy is the energy of a particle that it possesses because of it's position relative to other particles. Usually we think of a particle and it's relationship to a field, where the field has been generated by another particle. e.g. gravitational field and mass.
> 
> E=mc^2 is a truncated term that comes from the Relativistic Energy-mass equivalence. (As Hitmouse stated!) It comes about because the conservation of mass didn't work in special relativity and therefore it was required to 'fold in' the conservation of Energy also to make it work. Thus one finds that the universe can convert mass to energy and energy to mass.
> 
> ...





hitmouse said:


> Apologies for misreading your post. What Venusian Broon said about potential energy, though. By textbook definition, a bit different to the energy implied by E:M equivalence.


Oh I agree, I was playing on words a little  but my main point was to contradict an assertion earlier in the thread that described e=mc^2 as kinetic energy


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## BAYLOR (Oct 11, 2017)

Perhaps in a billion years we will build giant space generational habitats that can travel between star systems. Maybe we can build enough them movie Earths entire population out of harms way.


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