The amount of heat generated by the Sun per volume is much less than a typical pile of burning coal.
Experts Doubt the Sun Is Burning Coal (1863)
151–160 of 244 posts
Re: Experts Doubt the Sun Is Burning Coal (1863)
#152I was once at a tech conference for high schoolers in London where one of the distinguished speakers (others included Vint Cerf, and a UK government minister) told us that the primary reason the sun is hot was because it was still glowing with heat from the pressure of gravitational collapse.
I think their claim was that the nuclear reactions in the sun contributed to the Sun’s radiation, but did not contribute to the bulk of the Sun’s temperature (heat?)
I’m a little fuzzy, but I’ve never seen this claim elsewhere. Is it true?
Re: Experts Doubt the Sun Is Burning Coal (1863)
#153To me, I think what this demonstrates more than anything else is that the human mind is limited by the metaphors it has access to. Leaving astronomy out of it— just look at the how we describe the mind — it’s been variously described as breath, or hydraulics, or clockworks and now as a computer. Probably in 100 years we’ll be looking back at our primitive understanding of how the brain works and laughing. They though…
I strongly disagree. I don't disagree that human mind is limited by metaphors. I disagree that it applies to this situation.
Before you know about radioactivity and nuclear reactions the only options available were:
1. Try to find reasonable explanation using scientific explanations (chemistry at that time) and try to calculate the possibilities.
2. Leave the question undetermined.
3. Wildly speculate without any constraints. (God or some magic force).
Science was limited by data and experiments.
Re: Experts Doubt the Sun Is Burning Coal (1863)
#154Just checkin' the math: >>> sun_output = 3.828e26 # watts >>> sun_mass = 2e30 # kg >>> coal_energy_density = 30e6 # W*s/kg >>> year = 365*86400 >>> sun_mass * coal_energy_density / sun_output / year 4970.1868313110635 So (assuming a magical supply of oxygen) a lump of coal the mass of the sun could burn with the brightness of the sun for 4970 years Numbers from https://en.wikipedia.org/wiki/Sun and https://en.wikiped…
Thanks! — Any idea how they worked this one out?
> Assuming that the heat of the sun has been kept up by meteoric bodies falling into it, it is possible from the mass of the solar system to determine approximately the period during which the sun has shone. The limits lie between 100 millions and 400 millions of years.
Re: Experts Doubt the Sun Is Burning Coal (1863)
#155Earlier quoted context omitted.
Interesting to read. The Sun is referred to as 'he' and people were just beginning to understand how heat energy and mechanical energy could be transformed into one another. "He has enlightened our globe from one generation to another without any apparent diminution of strength, and we have formed the instinctive belief that no limit in the past or any in the future can be assigned to his functions. No proof of progr…
Maybe "he" is short for "Helios" :-)
Or it's the elemental symbol for Helium, and they knew about nuclear fusion.
Oh, you weren't joking?
Re: Experts Doubt the Sun Is Burning Coal (1863)
#156I would really like to be in 150 years in the future to see what assumptions we are making today are totally foolish like that was the case is sun as coal ;)
Re: Experts Doubt the Sun Is Burning Coal (1863)
#157Pop quiz - what do you think people will be laughing this hard about from our time in 150 years?
Re: Experts Doubt the Sun Is Burning Coal (1863)
#158Earlier quoted context omitted.
Kelvin also publicly stated we would never have heavier than air flying machines.
To be fair to Kelvin, it was a reasonable opinion at the time: 1) Half of the aviation pioneers died trying. 2) The Wright brothers were truly overachievers, devising a control system, early aviation engine (1903) and wind tunnel. 3) Producing light-weight, reliable and powerful aviation engines took over 20 years. The Atlantic crossing only became survivable after the Wright Brothers made the Whirlwind J-5 radial en…
To be fair to his critics: birds, bats, and bees exist.
Re: Experts Doubt the Sun Is Burning Coal (1863)
#159Remarkable to think that less than 150 years after that publication humanity was building supercolliders
Re: Experts Doubt the Sun Is Burning Coal (1863)
#160I had absolutely no idea that SA is so old. New Scientist - https://en.wikipedia.org/wiki/New_Scientist is a mere whippersnapper. It doesn't matter that the article is bollocks. It is reasoned bollocks. That is basically what science is all about! I would prefer if there was some more working shown to back up the article but it seems to imply that some might be available rather than just simple assertions. We live in…
> It doesn't matter that the article is bollocks. No, it isn't. It's correct in the basic claim of the title. Scientists in 1863 who believed that no known source of energy was capable of powering the Sun were right . The Sun is not powered by any source of energy that was known in 1863. > I would prefer if there was some more working shown to back up the article Scientific American wasn't the place to show the detai…
The article is using meteorites as an analogy; the model is of the Sun forming by gravitational contraction of a gas cloud, for which an r of infinity is appropriate.
What's interesting is that the power available from solar fusion is of a similar order of magnitude to that available from gravitational contraction. But of course it must be, because if fusion was too powerful medium-mass stars wouldn't be able to form to provide light and heat to habitable worlds, and if it was too weak then giant stars wouldn't be able to overcome their gravitational binding energy in supernovae to disperse the elements that form habitable worlds.