From: William Hall (william-hall@bigpond.com)
Date: Fri Dec 12 2008 - 00:32:03 MST
Alexi,
Let's get real here.
To fuse, deuterium nuclei have to come together physically in an area the
size of the atomic nucleus. This takes a great deal of pressure and heat.
More likely than two deuterium nuclei fusing is that a deuterium nucleus and
a hydrogen nucleus will fuse to form helium 3. I doubt that the pressures in
a gas giant are anything like high enough to support detonation of the whole
planet. Unlike nuclear fission, where fast neutron cause fission ahead of
the shock front resulting from the release of energy by prior fission events
and thus generate true detonations, fusion requires extremely high pressures
and temperatures such as are found in the centers of stars.
Even assuming that you could set of an H bomb in the center of a gas giant,
the heat released would cause the surrounding material to expand and thereby
reduce the probability of further fusion. As long as significant fusion
continues, there is a homeostatic relationship between pressure and the
release of heat. As the rate of fusion increases and more heat is released
the star expands to reduce the rate of fusion.
Conceivably, if the temperature of a gas giant was raised locally by a bomb,
perhaps there would be enough pressure in the core to sustain a continuing
rate of fusion. With luck, you might end up with a short-lived brown dwarf.
Even if the surface temperature of the planet reached the temperature of the
Sun, several factors would mitigate any significant impact on the
temperature and ecology of the earth.
Earth's orbit has a radius of 1 AU, Jupiter's is 5 AU. At its very closest
approach to Earth, Jupiter is 4 times as far from Earth than the Sun is
every day, and has a radius a tenth that of the Sun, or a disk area of
1/100th that of the Sun. The amount of radiation drops of as a function of
the square of the distance. Thus, at closest approach, assuming equal
surface temperatures, the amount of radiation from Jupiter would be
something on the order of 1/1600 th of that from the Sun.
1
---------
4^2 * 100
When Earth and Jupiter are on opposite sides of the Sun, the distance is 6
AU, and thus, the amount of radiation received from Jupiter would be 1/3600
that of the Sun.
Also, the temperature of a star is a function of its mass (increasing as a
function of its mass) and that the gas composition of Jupiter is not greatly
different from that of the Sun, if fusion was sustained at all, it would
take place at a VERY much lower rate than in the Sun.
As it is, Jupiter is known to be radiating slightly more heat than it
absorbs from the Sun. Someone has suggested that the excess energy to
maintain the temperature above thermal equilibrium might actually be the
consequence of a very low rate of deuterium fusion already going on in the
core. More likely though is that the planet is still radiating heat from
gravitational contraction continuing from the time of its initial formation.
In any event, your scenario that Earth would be threatened by a detonation
of deuterium within Jupiter is so far from what we know about astrophysical
processes and possibilities that it must be treated as pure fantasy. It is
simply too easily refuted by even the most basic understanding of nuclear
physics, astrophysics and classical astronomy.
Regards,
Bill
William P. (Bill) Hall, PhD
Documentation and Knowledge Management Systems Analyst
PO Box 94
Riddells Creek, Vic. 3431
Tel: +61 3 5428 6246
Email: william-hall@bigpond.com
Evolutionary Biology of Species and Organizations
URL: http://www.orgs-evolution-knowledge.net
National Fellow
Australian Centre for Science, Innovation and Society University of
Melbourne
ICT 5.59, 111 Barry St., Carlton
Tel: +61 3 8344 1530 (Mon, Tue, Thurs only)
Email: whall@unimelb.edu.au
URL: http://www.acsis.unimelb.edu.au/
-----Original Message-----
From: owner-sl4@sl4.org [mailto:owner-sl4@sl4.org] On Behalf Of Alexei
Turchin
Sent: Friday, 12 December 2008 10:02 AM
To: sl4@sl4.org
Subject: Re: [sl4] giant planets ignation - one more existential risk
Look. There is a big difference between very slow burning of ordinary
hydrogen in the Sun and detonation of deiterium. Detonation means
explosion.
http://en.wikipedia.org/wiki/Detonation
Ordinary hydrogen could not detonate - the p-p reaction takes time.
D+D could react immediately. So, D+D could give an explosion, and
p+p - can''t.
Ammount of D (deiterium) on the Jupiter is very large. If its
concentration is only 1 to 1600, then its ammount is in order of 20
masses of the Moon. This is in order of 10**24 кг.
If all it reacts 1/100 of this mass will be transformed into energy.
It is 10**21 kg. it is aproximately 10**37 J.
But the Sun every second creates only 10**26 J (3.83×10**26 W)
http://en.wikipedia.org/wiki/Sun
That means that if reaction would take 1 second, the Jupiter will
shine 10**11 times brighter then the Sun.
This is 100 billion times!
This is upper limit, of course, and we could reduce it on several
orders of magnitude easily, because not all D will react, because
Jupiter is futher from the earth then Sun (and so earth would receive
25 times less share of its energy) and so on.
But it still huge enough to think about it.
On 12/12/08, GS <radiosity@gmx.net> wrote:
> On Thu, 11 Dec 2008 20:03:45 +0100, Alexei Turchin
<alexeiturchin@gmail.com>
> wrote:
>
>
> > If all deiterium in the Jupiter reacts it would relize energy of 30
> > 000 years of Sun work in less then 10 seconds.
> > In this case the Earth will lose its atmosphere and several kilometers
> > of upper curst.
> >
>
> Can you tell us on which (maybe more than one) sources your "knowledge"
and
> estimations are based, and what exactly leads you to this beliefs?
>
> How would you explain that the fusion reaction of the Jupiter
> would be 9,4*10^10 (which is the result of your 30000 years in 10 sec)
> times stronger as a MUCH bigger system, namely the sun doing the same
> thing?The sun contains about 99% of the mass of our solar system. And it
> does allday long nothing but constantly burning in a fusion reaction.
> Besides that,the sun fuses mostly ordinary hydrogen atoms into helium,
which
> providesmore energy than deuterium because of the higher binding energy in
> the nucleus.
>
> gs
>
> --
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>
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