Solar system future: John Baez timeline

[Astrobuff]

Hello Astrobuff. I think you must be Shaun who commented on Stein's blog.

Good blog isnt it?

 

You may have misunderstood the point of posting JB's timeline.

I, for one, was not worrying about threats to human survival.

I don't "burn out precious braincells" worrying about the sun getting too hot.

 

I'm far more concerned with the immediate threats of war, overpopulation, destruction of land and ocean resources----human stupidity basically.

 

the point of the timeline, whether or not it is factually correct in every detail, is to get a perspective that says "look at the opportunity! we have all this time, if we don't screw ourselves and the rest of life up and miss the chance"

 

the sun going sub-giant is not a threat, it is a TIME-MARK analogous to a land mark, to help punctuate the perspective

 

IMHO if we are not âssholes we will most likely have spread life to other systems long before then

 

Hiya Martin. And yes I'm Shaun. This is the name most who knows me at work, in my political life and previously in school knows me by. John and Maurice are pseudonyms I used in communicating with some. Yeah Dr Steinn sure has a great blog. Really informative and regularly updated. Learnt tons there. I must have been living in the Dark Ages somehow for me not to found it earlier. By the way, Dr Steinn was someone I once pestered over email with a series of questions on white dwarfs, black holes, KT event, Methuselah (that 12.7 Gyrs old GC "captured" planet) a few years ago . With astronomers and astrophysicists now having their own blogs, perhaps it sure does make the life of astro bufss like myself a lot easier when we want to shoot a barrage of complex technical questions LOL.

 

Nah my reply to JB's post was really but an expression of angst. An plea for some common sense. By the look of things, we humans may not even live to survive past this century. Let alone to the sub-giant stage. Anyway likelihood is the Earth's oceans would have boiled away aeons before that. I'm not sure if any colonization of other worlds would mean that every man, women and child stands an equal right to be considered as a candidate when the time comes. Somehow I believe that there will be some kind of prejudicial selection process in place. Some men/women and child would be deemed to be more equal than others me think.

[lucaspa]

I don't think we can definately rule out a Big Crunch yet...

 

The nature of Dark Energy or the Cosmological Constant is not well known.

 

The cause is not well known, but the effect is.

 

During Inflation the Universe went through an episode of rapid expansion, in the first moments of the Big Bang. But the Inflation ended, how can we be sure it won't end again or even that the Cosmological Constant will remain positive ?

 

Because the Cosmological Constant can only BE positive. Also, data indicate that the CC has been around since the beginning of the universe. It is actually increasing in magnitude.

 

Remember, inflation was just for a fraction of a second; it was a period when expansion was geometric and faster than light. Inflation did end, but the expansion kept going on momentum. It was thought that it was possible for gravity to counter this momentum but there are 2 problems:

1. There isn't enough matter, either visible or dark, to counter the expansion even before the acceleration was discovered.

2. The expansion is accelerating, not slowing down! This makes it impossible for gravity to counter it. Already the expansion is so fast that gravity can't stop it.

 

We know that the expansion is currently accelerating, the data and our best models favors a Big Freeze.

 

But we don't know what cind of data and new models that lurks in the future.

 

We make conclusions based on the data we have today, not on data we hope or wish we will find in the future. IF and when new data turns up, then we change our minds. But to insist on forcing what we would like the universe to be onto the universe is the opposite of doing science.

 

However, right now the data falsifies a Big Crunch. Some absolutely new process would have to begin in order for the universe to contract again. All the processes we see operating right now falsify a Big Crunch.

[Spyman]

Because the Cosmological Constant can only BE positive.

Is that statement really proved ?

 

We make conclusions based on the data we have today, not on data we hope or wish we will find in the future. IF and when new data turns up, then we change our minds. But to insist on forcing what we would like the universe to be onto the universe is the opposite of doing science.

I don't think current conclusions totally rules out a Crunch, not enough data and understanding yet.

 

It's you that is extrapolating on current data and have faith in the results.

 

However, right now the data falsifies a Big Crunch. Some absolutely new process would have to begin in order for the universe to contract again. All the processes we see operating right now falsify a Big Crunch.

Well, like I said, the processes are not well known, when we learn more about them, we might have to change our view. It doesn't need to be any new processes, a better understanding of them might suffice.

 

The data favors a Big Freeze but doesn't rule out a Big Crunch.

 

The current evidence neither favors nor rules out dark energy, or modifications of general relativity, of a form that could halt or reverse an eternal expansion; it does, however set lower bounds on the duration collapse (approximately 42 billion years from now, or more than 24 billion years at the 95% confidence level, according to one group led by Andrei Linde). http://en.wikipedia.org/wiki/Big_Crunch