How do we know how long the sun will and has lasted?

Answer 1

We DON`T.
So called experts work it out in some equation based on prior knowledge adn experiments carried out on earth. Seeing as our prior knowledge is nothing, not even 0.00000001% in comparison to what could be know.

The "educated" guesses these people are allowed to make are rediculous. Just because they memorised stuff some previous person taught them and through this avenue achieved a PHD doesn´t mean they can guess our whole science up.

Answer 2

The universe is full of stars which are at various stages of their lives. Astronomers examine these stars at their different stages and calculate whether or not they have a similar make up to the Sun. They also calculate how old they are (I don't know how) and use these calculations to estimate the stages of the Sun's life and how long it will last. Of course nothing can be proven conclusively. The fate of the sun is as follows: Our Sun is estimated to be around 5 billion years old, with an expected lifespan of a further 5 billion years- our Sun is now middle-aged.
The life cycle of a star depends very much on it's size and mass. In the case of the Sun, five or six billion years from now when the central hydrogen to helium reactions have ceased, the outer shell of the Sun will expand. This expansion continues until the shell reaches a point where temperatures are less than ten million degrees. Hydrogen fusion will shut itself off and the self gravitation of the Sun will force a renewed contraction of it's helium rich core, thus resulting in an increase in temperature and pressure. The helium nuclei will be jammed together and the ashes of the previous burning stage will ignite, triggering a second round of fusion reactions. These processes are responsible for the creation of heavier elements such as carbon and oxygen. The Sun's appearance will change dramatically, as it takes on a bloated look - a red giant star, enveloping the inner planets Mercury, Venus and probably Earth as well. Eventually, the solar interior will be comprised mainly of carbon and oxygen, where at the prevailing temperatures no further nuclear reactions can take place. Once again the Sun will continue it's inevitable collapse, temperatures rising again and triggering perhaps a last round of nuclear reactions.In the last death throes, the Sun will spew it's gaseous atmosphere out to space- a spherical shell of illuminated gas as often seen in other nebulae. What remains of the Sun will be a small hot star, cooling and collapsed to immense density - a spoonful of the star would weigh about a ton. Ultimately, while cooling over a further few billion years, our Sun will be known as a white dwarf and finally a dark and dead black dwarf.
But you probably already knew that.

Answer 3

from wiki >
The Sun's current age, determined using computer models of stellar evolution and nucleocosmochronology, is thought to be about 4.57 billion years.

The Sun is about halfway through its main-sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than 4 million tonnes of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. The Sun will spend a total of approximately 10 billion years as a main sequence star.

The Sun does not have enough mass to explode as a supernova. Instead, in 4-5 billion years, it will enter a red giant phase, its outer layers expanding as the hydrogen fuel in the core is consumed and the core contracts and heats up. Helium fusion will begin when the core temperature reaches about 3×108 K. While it is likely that the expansion of the outer layers of the Sun will reach the current position of Earth's orbit, recent research suggests that mass lost from the Sun earlier in its red giant phase will cause the Earth's orbit to move further out, preventing it from being engulfed. However, Earth's water and atmosphere will be boiled away as the sun's luminosity eventually increases by a factor of several thousand.

Following the red giant phase, intense thermal pulsations will cause the Sun to throw off its outer layers, forming a planetary nebula. The only object that remains after the outer layers are ejected is the extremely hot stellar core, which will slowly cool and fade as a white dwarf over many billions of years. This stellar evolution scenario is typical of low- to medium-mass stars.

Answer 4

About 74% of the Sun's mass is hydrogen, 25% is helium, and the rest is made up of trace quantities of heavier elements.
It generates its energy by nuclear fusion of hydrogen nuclei into helium and is in a state of hydrostatic balance, neither contracting nor expanding over time.
We know how much energy sun emits each hour, we also know how much energy is produced from one pound of the sun mass and we know how much sun weights (sun mass is approximate equal to 332,950 times the earth mass).
The Sun's current age is thought to be about 4.57 billion years. The Sun will spend a total of approximately 10 billion years as a main sequence star.

Answer 5

Astronomers determine the age of our Sun, and other stars, using a process called nucleocosmochronology. This link will help explain what that is. Basically hydrogen and helium burn at predictable rates and that rate of consumption is steady and constant and used to predict the relative age of our Sun.

Answer 6

It's calculated based on
1. Raw hydrogen available for combustion in different zones
2. Temperature at different zones (core, surface etc)
3. Pressure in different zones.

There is radiation pressure created when fusion from hydrogen to helium takes place....There is equilibrium maintained between gravitaional pull -- towards the core and radiation pressure - away from the core and hence the shape and temperature of sun is maintained. If amount of hydrogen in core is consumed and it's quantity decrease, radiation pressure decreases and gravitational pull increases...sun collapse during this time and becomes white due to less amount of radiation emitted (white dwarf)..This is beginning of death of a star

Answer 7

Don Juan , from Carlos Castaneda books series [yes the yaqui curandero ] used to say * our awarness feeds the Sun *
according to the ancient Maya .and now days astronomy, sunspots determine our future
though none knows the precise dates of its beginning ...obviously to be accurate in
choosing an end date is pure guessing
yet evreything is interconnected ,and deeply related
[if we... like /agree ,with it or not , is absolutely irrelevant ]
facts are facts so who know ? probably depends on the capability [among current terrestrials to keep the torch burning
'so to speak ..!!!

Answer 8

Read THE SUN Newspaper (it only tells the trough)

Answer 9

Based on the ratio of hydrogen to helium, and the rate at which it is being used up (converted from hydrogen to helium).

Answer 10

I can safely say it's lasted for at least the last 18000 days, so it's probably going to be around for a little while longer. Worry about something important, like ... are they ever going to make another Star Trek series? Inquiring minds wanna know ;-)