<div> </div>
<div>Paul et. al.</div>
<div> </div>
<div>Paul wrote:</div>
<div><br>We've been around for a mere few million years, only the last few thousand of which we've had the ability to write things down. This is a small fraction of time for the Sun. Our observations of the Sun has occurred over such a small timescale that we can basically say that we've only seen it as a static observation.
</div>
<div>------</div>
<div>Good point, a point that applies in different ways to many scientific issues...We could question whether gravity has always operated as we observe, given the over 10 billion year history of the universe, and our limited time scale of observation. Science makes certain assumptions about how the universe operates, and the continuity of the "laws of nature" is one of those assumptions, continuity over time and in different places in the universe. This principle cannot be "proved" without a doubt, as far as I know
</div>
<div> </div>
<div>But science does have its "time machines" to see into the past before humans could make observations directly. The theory of biological evolution is not based on just the life forms we have observed evolving since Darwin, but on the evidence of fossils from Earth's history, offering a kind of scientific "time machine" giving information on life forms millions of years before humans walked the planet. And in astronomy, we have observations of many different kinds of stars from many different stages of evolution, providing a kind of "time machine" to allow us by inference to look into our suns past and future. The information we get from distant stars is in some ways like a fossil (I don't intend this as an exact analogy), given that this information sometimes took longer than the history of the human race to reach us...It's mind boggling, but astronomy gathers information about the universe dating from billions of years ago, even before our solar system formed.
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<div>------</div>
<div>Paul wrote:<br><br>I think the 0.8 billion year number you quoted is the time it will take for the slow process of hydrogen fusion at the core to raise the Earth's temperature 5%. <br>------</div>
<div>The article I quoted on stellar evolution said that due to our suns evolution the Earth would warm 5 degrees in 0.8 billion years, not 5%.</div>
<div> </div>
<div>As to how reliable this figure is, I cannot say for sure, given I have not surveyed the scientific consensus on this issue in this field, and there may not be a consensus.</div>
<div> </div>
<div>I was wondering, can you offer some sources, articles, books, or websites, for the information you were providing on stellar evolution?</div>
<div> </div>
<div>Ted Moffett</div>
<div><br>Ted Moffett wrote: </div>
<div>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div text="#000000" bgcolor="#ffffff">
<blockquote cite="http://midd03f69e0704231323w6c982dffh331e1366bbf68cff@mail.gmail.com" type="cite">
<div><span class="e" id="q_11221edbe19be194_1">
<div> </div>
<div>All-</div>
<div> </div>
<div>Our sun will eventually cause fatal increases in Earth temperature in its inevitable evolution into a red giant star. When will these temperature impacts become significant? The article below estimates that in 800 million years the sun's impact will raise Earth temperatures by 5 degrees, the same amount predicted by some global warming models for the human impact on global temperatures in the next century:
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<div> </div>
<div><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sussex.ac.uk/press_office/media/media191.pdf" target="_blank">http://www.sussex.ac.uk/press_office/media/media191.pdf</a></div>
<div> </div>
<div> </div>
<div><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://72.14.253.104/search?q=cache:hAqjwfgBKT4J:www.sussex.ac.uk/press_office/media/media191.pdf+time+remaining+Earth+biosphere+sun+expansion&hl=en&ct=clnk&cd=6&gl=us" target="_blank">
http://72.14.253.104/search?q=cache:hAqjwfgBKT4J:www.sussex.ac.uk/press_office/media/media191.pdf+time+remaining+Earth+biosphere+sun+expansion&hl=en&ct=clnk&cd=6&gl=us </a></div>
<div> </div>
<div>"As a first application, let us ask how long it will take for the temperature of the Earth to rise by 5 degrees (the rise anticipated in the next century or so if the current human-induced greenhouse effect continues unchecked). The equation predicts it will take the evolving sun about about
0.8 billion years to produce this rise- so human activity may be accelerating astronomical effects by a factor of about 10 million."</div>
<div>------</div>
<div>This puts the highly doubtful claim that the current warming trend on Earth is mostly due to increases in solar activity into perspective, it seems.</div>
<div> </div>
<div>Ted Moffett</div>
<div> </div>
<div> </div></span></div><pre><hr width="90%" size="4">
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