Semi-OT: A General Tech Question Thread for me :)

[narf poit chez BOOM]

Slick said:
Then there would be a "south" but no "east" or "west".

In, Out, Up, Down, East, West.

* Niven!

[Hunpecked]

AgentZero writes: "As for the whole whether or not an FTL race would have found us by now, I think most arguments are flawed by assuming that an alien race would have even remotely the same motivations as our own."

Obviously it's tough to generalize from one data point. It seems reasonable to suggest, however, that both biological and cultural evolution favor expansionism in intelligent species. Biologically, species that don't try to increase their numbers and ranges tend to get wiped out by competing organisms and/or environmental changes (ice ages, asteroid strikes, etc.). Culturally, stagnant civilizations are usually overrun by vigorous expansionist competitors. If a sapient alien species is as culturally diverse as our own (e.g. because of varied planetary habitats), even a SINGLE expansionist culture would end up determining the character of the whole race.

The same principle holds on a larger scale. Perhaps evolution for some reason favors introspective sentient species. Maybe the universe is full of "flower children" who make love (with birth control), not road trips. If so, then FTL doesn't exist, because it takes only ONE vagabond culture in ONE species with practical FTL and a billion year head start to put ALL the hippies out of business.

With STL only, the same thing should happen on a galactic scale, so I can buy the argument that we're either first or alone (more or less) in the Milky Way, as unlikely as that appears. There are of course other possibilities, some of which we've already covered.

AgentZero also writes: "Our solar system is located in one of the arms of the Milky Way's spiral, now does that make it part of the older (first to form) or newer parts of the galaxy?"

According to the article below the first stars in our galaxy formed about 13.6 billion years ago. That makes our sun, at 5 billion years, a relative youngster.

http://www.space.com/scienceastronom...ge_040817.html

I assume that 13 billion years ago local conditions could have led to star formation just about anywhere in the galaxy, but most "old" stars formed near the galactic center and in the galactic "halo" of globular clusters. Spiral arms are areas of new star formation that shine brighter than the rest of the galactic disk due to the very young blue giant stars within them. Our solar system has been around the galaxy 18-20 times since it was born, so our current location in a star forming region is a coincidence.

[dogscoff]

Hunpecked said:
According to the article below the first stars in our galaxy formed about 13.6 billion years ago. That makes our sun, at 5 billion years, a relative youngster.

http://www.space.com/scienceastronom...ge_040817.html

But according to that same article, our galaxy is almost as old as the universe. When the universe was born, it was all hydrogen- there were no heavy elements. It is the ongoing process of star-burning that turns dull old hydrogen into stuff like carbon and oxygen that we need for life. The older the universe gets, the more hydrogen is turned into heavy elements. Therefore, looking at it the other way, as you look back in time towards the Big Bang the amount of heavy elements in the universe dwindles down to nothing.
Since these heavy elements are needed for life, shouldn't the probablilty of life dwindle away with it?

Or, to put it another way, we may be among the first life to emerge, because it's not the amount of stars that have existed over the last 13.whatever billion years that matters, it's the availability of heavy elements- and they've never been more available than right now. Give it another 10 billion years and there could be life springing up all over the place, because the universe will be a much heavier place than it is now. It may even get *too* heavy for life at some point, which would mean the Drake equation would have to factor in some sort of bell curve with "suitability for life of heavy element/ hydrogen ratio" on one axis and "time since big bang" on the other.

[Wolfman77]

Sorry about the quote, I wasn't thinking about location as much as looking at the part about the newer stars around us.

Good wiki article on coordinates a few posts back.

Once the stars fuse the hydrogen into large elements, and there isn't enough left to make significant amounts of things like water. I think it will probbably work like most stuff does. We'll never runn completely out , but there will be less and less, and fewer and fewer stars being born. so the amount of habitable areas will shrink.

[dogscoff]

Since I'm in a diagrammatical mood (see Ceres thread):


It's the goldilocks syndrome all over again. The question is, where are we on this line? The fact that we aren't yet overrun with aliens would indicate that we are on the steep bit of the climb between A and B, but who knows? Maybe we're somewhere nearer C and everyone else is just extinct already.

Actually, the line between B anc C probably ought to be far shallower and straighter, since the hyrogen->heavy element process will be quicker when the universe is young, because there's more hydrogen about to clump up and form stars.

[Hunpecked]

Dogscoff writes: "...as you look back in time towards the Big Bang the amount of heavy elements in the universe dwindles down to nothing. Since these heavy elements are needed for life, shouldn't the probablilty of life dwindle away with it?"

Absolutely. Note, however, that we're dealing with averages and probabilities here. In regions of unusually rapid star formation (galactic cores, globular clusters) the interstellar medium could be sufficiently enriched with "metals" (atomic number 3 and above) in a billion years (the most massive stars are thought to go supernova in under a hundred million years). Such regions are also pretty hostile to life (black holes, sterilizing radiation), but given the vast number of galaxies in the universe, it seems likely that suitable combinations of conditions would exist in many of them. If so, even after 4-5 billion years of evolution, life forms in these regions would have a 7 billion year head start on us.

While researching this post I came across an interesting article from 1996:

http://hubblesite.org/newscenter/new...eases/1996/37/

Judging from Hubble images of distant galaxies, it appears that the rate of star formation in the universe peaked about 3 billion years after the Big Bang (BB), at about 10-15 times the current rate. By the time our sun was formed, some 8-9 billion years post-BB, most of the stars the universe will ever have had already been born. That means we've also already had most of our supernovas, so Dogscoff's curve (lovely diagram, BTW) should probably be skewed to the left.

[Renegade 13]

dogscoff said:
When the universe was born, it was all hydrogen- there were no heavy elements.

As far as I know, when the universe was born, it was essentially an electrically charged soup of particles. Free atomic nuclei and free electrons were everywhere, since the temperature for a few hundred million years was far too hot to allow electrons to 'permanently' bond with the free atomic nuclei. So for quite a while in there it was an electromagnetically opaque universe, until things cooled off enough to allow the first elements to form.

[narf poit chez BOOM]

...Why would all of those elements be hydrogen?

[Wolfman77]

Protons atract electrons. 1 proton + one electron = hydrogen. Protons, having the same electric charge, need to be forced together to form larger atoms. Which happened only after stars formed.

[narf poit chez BOOM]

That makes sense.

But...Wouldn't 1 proton + 1 electron = neutron?