Heat Death of the Universe

[Radar]

I find this during my cyber travels.

An interesting read about energy transfer. Once the universe heats up from heat dissipation, then no more heat transfer can happen, which means the universe will cease functioning as we know it.

http://gawain.membrane.com/multimedia/play_the_name_game/my_terminal_condition/heat_death_of_the_universe_footnotes.html

It's a long shot I know.

Ray

[Jimbot]

SO the real question is about whether the universe is/will continue to expand and therefore which end will be valid. Hmmm 15 billion years old approx so far and just another few to go. Guess we need some more info before we state who is right!!

Jim




I find this during my cyber travels.

An interesting read about energy transfer. Once the universe heats up from heat dissipation, then no more heat transfer can happen, which means the universe will cease functioning as we know it.

http://gawain.membrane.com/multimedia/play_the_name_game/my_terminal_condition/heat_death_of_the_universe_footnotes.html

It's a long shot I know.

Ray

[Robert TG]

The Universe is thought to be 13.7 Billion years old, if our understanding of it is correct. While our Sun is expected to only last another 5 billion years or so, the rest of the universe has a very long time ahead of it. The lifetime of the universe is in the order of Many Billions of Billion of years. In that time scale we are at the birth of the universe, in the universe’s infancy, and it is expected to have an enormous life.

[Tenacious Del]

This thread is like a main course. Great reading. What happens when all the hydrogen in the universe is used and stars can no longer burn? what happens to all the matter? we will probably have technology by then to make stars out of anything, I hope. :pipethinker:

[Robert TG]

"WE" would be very lucky to still be around that far into the future.

There are enormous quanities of Hydrogen in gas clouds and when it forms a star and gets 'used up' it produces Helium. So star births will be around for such a long time after our sun is gone. The earliest (oldest) Red Dwarf Stars that have formed in the universe have never 'burned out' yet, in the Billions of years since they have formed.

When it is said that our sun will stay on the main sequence for another five billion years, it means the Sun will remain the about the same as it is today for that period of time. Our Sun will eventually become a white dwarf and last for many more billions of years as that.

[Radar]

So Rob, can helium feed stars like hydrogen can? I guess it can. What are the main differences between a helium rich star compared to a hydrogen rich star?

Ray

[Robert TG]

So Rob, can helium feed stars like hydrogen can? I guess it can. What are the main differences between a helium rich star compared to a hydrogen rich star?

Ray

That’s a big topic, but in a nutshell…

There are huge clouds of Hydrogen gas that will never form stars and will remain as clouds of Hydrogen gas.

There are Giant Balls of warm hydrogen gas that never reaches fusion temperature, called Brown Dwarfs. So there should be plenty of Hydrogen around for a long time.

All stars START out with Hydrogen burning (Fusion), the 'ash' of this burning is Helium. So as a star ages it's % of Helium becomes larger.

From here a lot depends upon the size of the star.

A small star like a Red Dwarfs will form Helium but never have enough Helium to cause a collapse and start Helium fusion, so they will end their very long life as a giant ball of cooling Helium.

The helium doesn't burn at the lower temperature or pressure it takes to burn Hydrogen. The heavier Helium sinks to the central region or core of a Hydrogen burning star. The Hydrogen continues to burn around this ever growing core of helium and thus fusion is taking place closer and closer to the surface of the star. As the heavier Helium builds up the core contracts and heats up and the other layer expands and the star can become a Red Giant.

So, a Red Giant could be said to be a very Helium Rich star.

Again it depends on the size of the star but the Helium can get enough temperature and pressure to start Helium fusion into Carbon. The star stuff we are made out of (Carbon based life forms). The carbon core builds up in the centre of the star in the same way because it is heavier. The core can collapse and the outer layer can be blown away and we see the core as a White Dwarf star, being very Carbon rich, and given enough mass the fusion of carbon can form Iron.

The collapse cores can form Neutron stars, depending on the original star size, greater than 10 solar masses, or Black Holes where the original star has over 30 solar masses.

What the star is made of changes it's brightness and temperature and size over time and that changes Spectral Class we put the star in and what we call them.

[Impakt]

There is no evidence (believe it or not) that stars are powered by nuclear fusion. It's pure speculation (as with most things in astronomy). In fact, the nuclear fusion model can not account for the suns corona - it shouldnt be there if nuclear fusion is the correct model. thats not to say that nuclear fusion does not occur in stars (it does) it's just not proven to be how stars are powered as such. There are other theories which make more accurate predictions (electric universe theory - I'll start a thread about this). At the end of the day I dont much care with theory is right or wrong, provided our star keeps doing it's thing!

[Radar]

There is no evidence (believe it or not) that stars are powered by nuclear fusion. It's pure speculation (as with most things in astronomy).

Hmm, never really thought about the proof side of this. I'll check that electrical theory out.

Ray

[Impakt]

I always belived everything I heard from NASA and astronomers, but when I started to realy dig into the physics of it, I discovered that much of what I thought was fact, was actually theory or outright speculation!

One must remember that science lives off grants and funding. It's safer to tow the line than to go out on a limb. People who go out on a limb often loose their funding or as in Halton Arps case, telescope time.