[elijah77jc]

Originally Posted by Lightknight

Perhaps you should be a bit more explanatory to her. I feel like her question was not directly answered.

while i admit that my avatar is a bit misleading, please don't tell me that you think i'm a girl.

come on gavin, we've crossed lines in the past.

[jdironfist]

Originally Posted by elijah77jc

while i admit that my avatar is a bit misleading, please don't tell me that you think i'm a girl.

come on gavin, we've crossed lines in the past.

Plus, Elijah's a guy .

Love in Him,
Joel

[jdironfist]

Originally Posted by JerryLove

As to the question of the loss of mass, the rate is hard tobe certain on. We can estimate the mass lost through the fusion of hydrogen into helium by looking at the sun's energy output; but I don't think we have an accurat model of nutrino loss, nor are we certain how much mass the sun gains from consuming matter around it.

I thought we actually did have a decent model of neutrino loss. It would go something like this:

The Sun operates on the proton-proton cycle (it fuses hydrogen into helium). So for every hydrogen involved in the fusion, you add a proton (I think it's safe to ignore the electrons because this deep into the Sun, the electrons have been stripped off the atom due to the immense pressure). Now, this is a problem—helium not only has two protons, but also has two neutrons. In the proton-proton cycle, four hydrogens are actually consumed, but two of the protons become neutrons. This transformation causes two neutrinos to be emitted, one for each proton that is turned into a neutron. So the equation would look something like this:

4H⁺ ==> 1He₄ + 2 neutrinos (normally denoted with the Greek letter "nu")

Using this equation, the mass of a proton, and the mass of a helium-4 atom, we can (I think) figure out how much mass is lost, given the number of fusions that happen per day (which I think can be calculated, but I can't remember).

Originally Posted by JerryLove

It's not as simple as you believe it to be. The orbit of the Earth varies over time. Sometimes more circular, sometimes more elliptica, sometimes farther out, sometimes farther in. In addition to the inherent issues with any orbiting body, the effects of other gravitic sources (other planets for example) cause both cyclial and non-cyclical changes in orbit.

The Earth's axis rotates in 41,000 year cycles, the obliquity cycles in 1,250,000 year cycles, orbital eccentricity every 100,000 years or so. Then there are the several cycles in solar activity to deal with.

Reality is far more complicated than you give it credti for.

In other words, we can't assume the cow is a sphere ? Bummer.

Love in Him,
Joel

[JerryLove]

I thought we actually did have a decent model of neutrino loss. It would go something like this:

I think the issue has been in verifying that number; though it may indeed be accurate. Nutrions have that annoying tendancy to pass through detectors.

In other words, we can't assume the cow is a sphere ? Bummer.

Well it would make the math easier

[nate95366]

Generally speaking, the volume of the Sun is more directly a function of its internal (core) temperature than its mass. The heat energy radiating from the core provides a force counter-active to gravity. Now, mass does play a part in how hot the core of the sun gets, but so does the availability of fusible materials (hydrogen and helium in the sun's case). If the core of the Sun were hotter (as seen in other stars principally fusing helium), the Sun would be larger (greater volume) and its surface would be cooler (i.e. a red giant of sorts). If the Sun's core were cooler, the sun would be smaller, and its surface may actually be hotter (i.e. a white dwarf of sorts). The former situation is more common than the latter, unless you speak of stars that have basically stopped doing fusion and are just cooling off slowly (which would be most white dwarves).

At least that's how I understand it?...

Nate

[himself12]

The sun is "burning" and therefore becoming smaller in mass.
Therefore, the gravitation must also become smaller over time.
That will have influence on the gravitation force that holds the planets in orbit around the sun.
1 bill. years ago the gravitation force of the sun would have been must greater, which again would have influence on the orbits of the planets.

Mercury is the closest planet. There must be a limit to how large the mass / gravitation force from the sun could be before Mercury would had been pulled in to the sun.

[JerryLove]

Originally Posted by himself12

The sun is "burning" and therefore becoming smaller in mass.
Therefore, the gravitation must also become smaller over time.

Yes. Loss of mass as the result of both conversion to energy and expulsion of particles.

The mass converted to energy over the entire life of the Sun to date is about 3.1 x 10^29 grams. The mass of the Sun is 4 x 10^33 grams so this loss equals 0.008 percent of its current mass.

The Sun also produces a 'solar wind' of particles at a rate of about 10^-14 solar masses per year. In 4 billion years this amounts to about 0.001 percent of the Sun's mass

That will have influence on the gravitation force that holds the planets in orbit around the sun.

Yes. Their orbits are generally getting larger.

1 bill. years ago the gravitation force of the sun would have been must greater, which again would have influence on the orbits of the planets.

The gravity was about 0.002% higher.

Mercury is the closest planet. There must be a limit to how large the mass / gravitation force from the sun could be before Mercury would had been pulled in to the sun.

Yes.

[RiftZM2003]

Between 1986 and 1996, the intensity of solar radiation increased by 0.036 percent, according to Richard C. Willson of Columbia University's Center for Climate Systems Research in Altadena, California. Then, according to Judith Lean from the Naval Research Laboratory in Washington, D.C, the sun's strength in 1996 equaled or fell slightly below its 1986 value. Since the strength and size of the sun has only been studied with accurate technology since 1978, it's hard to give an estimate on just how long the cycles actually are. It is believed that they go through 11-year cycles, but it is also believed that the sun might undergo other cycles of intensity and whatnot, such as the mini ice age during the 17th century, or even the mini ice age experienced during the "Dark Ages," where the temperature was lower than that of normal, followed by the "Medieval Warm Period." Around 1250 the Atlantic Ice Pack began to grow, in 1300 warm summers stopped being dependable in Northern Europe, 1315-1317 there were rains and great famine. In 1550 it is believed that worldwide glacial expansion began, and in 1650 we experienced a "climatic minimum." In 1677, the Thames River in froze solid (which was unusual), ice skating on the main canal of Pompenburg, Rotterdam in 1825.

"In the North Atlantic, sediments accumulated since the end of the last ice age, nearly 12,000 years ago, show regular increases in the amount of coarse sediment grains deposited from icebergs melting in the now open ocean, indicating a series of 1-2°C (2-4°F) cooling events recurring every 1,500 years or so (Bond et al., 1997). The most recent of these cooling events was the Little Ice Age. These same cooling events are detected in sediments accumulating off Africa, but the cooling events appear to be larger, ranging between 3-8°C (6-14°F)."
- quoted from: USGCRP Seminar: Abrupt Climate Changes Revisited: How Serious and How Likely? -

There really isn't a whole lot of data to suggest what normal climate temperatures are, if there is such a thing, but there are always a lot of factors that go hand in hand with climate change, such as pollution (CO2), volcanic activity, ocean current flows, fluctuations in the suns solar activity, etc. Over the past 10 years, the sun has actually gotten slightly brighter now than it was 10 years ago, which does mean an increase in solar radiation. Also, the sun is entering it's "quiet" phase, or solar minimum. So, it is very likely it will dim gradually over the next 10 - 11 years before entering the solar maximum. Usually, this accounts for a .10 percent fluctuation (yes, .10%, not 10.0%).

As for the actual growth, Table 2 of Sachmann, Boothroyd, and Kraemer (1993; ApJ 418, 457) gives the following about the Sun's age and radius (age is in billions of years and the radius is in solar radii):

AGE RADIUS

0.048 0.897
4.550 1.00
7.56 1.13

So, during 7.56 - 0.048 = 7.512 Gyr, the Sun's radius increases by 1.13 - 0.897 = 0.233 solar radii. That works out to 3.1 x 10**-11 solar radii = 2.2 cm = 0.85 inch per year. The annual increase in the Sun's diameter (as opposed to the radius) would be twice this.

[Sean.thomson]