Nuclear ignition of gas giant atmospheres

  • Thread starter Tyro
  • Start date

chroot

Staff Emeritus
Science Advisor
Gold Member
10,166
34
Oh, and by the way, my claim was:
The sun's core produces less energy per unit volume than does a candle flame.
to which you replied
I COULD NOT DO ANY CALCULATIONS TO VERIFY IT
You COULD NOT DO ANY CALCULATIONS? Why not? Are the solar luminosity and core radius known only by me or something? *snicker* You're a funny one.

- Warren
 
105
0
Originally posted by marcus
It makes two orders of magnitude difference----a factor of 100.
All life would be burnt up if your figure for the wattage of the sun were correct, Tyro.

Allen's handbook figure is 3.8 E26 watts. It is a standard reference in Astrophysics. But also one can easily calculate it from the solar constant.

In your calculation please verify your figure of 2.87E12 meters for the radius of the earth's orbit
and the formula used for the area of a sphere (should be 4piR2 and not simply piR2

Your figure for the radius of the earth's orbit might be too large by a factor of 19.
When I talked about it not making much of a difference, check the low energy/volume figures you are getting. It is not going to make much of a difference in the conclusion that the energy/volume of the sun < energy/volume of a candle.

My calculations were based on using the solar constant, which was constant throughout the calculations and is what would determine whether we get burnt up or not. So, all life would not get burnt up in one sense.

marcus - I am not saying your calculations are wrong. I am asking why mine are wrong. So quoting your reference is unnecessary - I know when there is an error.

As for verifying the dimensions of Earth's orbit, I got it by pulling off the first figure I could Google out (link below):

here

Edit:
Whoops. I found the mistake. I was reading the info off the first link too fast and didn't read the header. I am getting 3.874e26 now - so that is fine now. Earth's orbital radius should be 1.5e11m. The one I quoted was for Uranus.



Whoops @ the factor of '4'. Summer heat quite literally cooks my brain . But the conclusion is still the same and still out by a magnitude of 100.


Basically, what are the assumptions made in calculating the sun's power output?
  • Part of the sun's energy goes to radiant energy, the rest to gravitational energy to the outbound mass flux. Is this included in the power output calculations?
  • If the sun's power output is calculated using the solar constant, does the solar constant itself involve energies within the visible and near visible wavelengths, or beyond it?

Both of these factors could potentially increase the actual value of the sun's power output, although it seems that the conclusion made previously regarding a candle/sun would be the same because of the sheer minuteness of the figure.

*Goes to look up the definition of solar constant to check for its assumptions.*

Note: From these calculations, it seems that the solar energy output does not take into account the energy lost to GPE from outwards mass flux.
 
Last edited:
105
0
Originally posted by chroot
Oh, and by the way, my claim was:

to which you replied

You COULD NOT DO ANY CALCULATIONS? Why not? Are the solar luminosity and core radius known only by me or something? *snicker* You're a funny one.

- Warren
*snicker* You did not provide me with any of YOUR assumptions before you started. If I started making assumptions and my assumptions were different from yours, of course our results will differ.

Your assumptions only became clearer in your NEXT post so from there only can I start doing calculations. Capiche?
 

chroot

Staff Emeritus
Science Advisor
Gold Member
10,166
34
I'm going to ask you a second time.

What assumptions are necessary to verify or disprove the following statement:
The sun's core produces less energy per unit volume than does a candle flame.
- Warren
 
105
0
Originally posted by chroot
I'm going to ask you a second time.

What assumptions are necessary to verify or disprove the following statement:
Originally posted by chroot

The sun's core produces less energy per unit volume than does a candle flame.
- Warren
Unless I have been reading too fast again or you edited a previous post, this is the first time you asked me what assumptions are necessary.

Assumptions/info needed:
  1. Assumed radius of region actively undergoing nuclear fusion.
  2. Whether this is the same as your definition of 'core'.
  3. Your value for the power output of the sun.
  4. Actually, power outputs for a candle you are using too.
  5. Your definition of a candle flame - to determine the volume of the reacting area for comparison.
  6. Finally, checking that the assumptions first made are relevant to the problem. (E.g. the solar power output seems dubious because it seems to have been derived purely from radiant energy calculations)
    [/list=1]

    I have to check that I am starting off with the right assumptions as you and that you are starting off with the right assumptions, before barreling of to do a calculation. It is just that. Different assumptions, different results.
 
Last edited:

chroot

Staff Emeritus
Science Advisor
Gold Member
10,166
34
Originally posted by Tyro
Assumptions/info needed:
You are misusing the term 'assumption.' What you really mean is prior, a result of a previous experiment. An assumption has no experimental basis. I made no assumptions, but I did make use of priors.

- Warren
 

Related Threads for: Nuclear ignition of gas giant atmospheres

Replies
10
Views
6K
Replies
1
Views
2K
Replies
1
Views
2K
Replies
13
Views
5K
Replies
76
Views
11K
  • Posted
Replies
1
Views
660
  • Posted
Replies
14
Views
14K
Replies
27
Views
3K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top