Discussion in 'Astronomy, Exobiology, & Cosmology' started by KennyJC, May 29, 2005.
I don't know where you got that idea, Dwayne, but it is wrong.
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Wow ! ! What was that all about ? I just got back to sciforums after an absence of some weeks. Can any one explain to me what all that means. Have I missed some revolution in science while I was away ?
I dont mind the guy's gramar, after all many members do not have english as their first language. But ??
I think you are not aware of all the facts.
The proximity of alpha Centauri is random and has <b>not</b> had any major affect to our solar system.
The Alpha Centauri system, seems to have been born a couple of thousand million years before the sun in a different star nursery.
It is currently approaching the sun at a rate of about 16000m/s …so after it passes us we probably won’t ever encounter the star again.
<b>BUT</b>, it is thought that close passages of a star(s) a couple of billion years ago <i>did</i> influence our system (<i>that event may have perturbed the oort cloud and orbits of the giant planets and eventually lead to the bombardment phases and it is thought that those cometary impacts brought water to a dry earth</i>)
Another group of star also may have influenced the earth. a volatile star pack known as the <b>Scorpius-Centaurus OB Association</b>, passed relatively near the solar system several million years ago.
The stars have a habit of going supernova….
Interestingly, the timing of the last star explosion, about 3 million years ago, coincides with a change in the climate in Africa, when drier conditions caused forests to retreat and the savannah to emerge.
(<i> it also coincided with the uplifting of the moon mountains, in central Africa , that changed the rainfall patterns</i>)
Anthropologists and other experts believe this change brought early hominids (<i>Australopithecus afarensis</i>) out of the trees, forcing them to walk upright.
4.5 billion, according to the New Zealand system of counting, is 4,500,000,000 i.e. four thousand, five hundred million; So thirthy billion trillion is 30 x 10 to the power of 30, i.e. 30 with 30 zeros after it as you've written, blindman.
I've noticed that everytime it's 'hot', I want to swing down from my tree, grab my club and head out for good long 'upright' walk with my hairy hominid buddies, looking for some 'fastfood'. Rhino burgers anyone?
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Well at least you have a choice .
But for other hominids then the deforestation does not give them any choice.
They have to survive in dwindling forest islands or adapt to a life on the open plain.
BTW 4,600,000,000 Years age of Earth...
Maybe, that's just the way it is and thanks to the intelligence of the human race, just maybe, that's way it will always be. 'Here Today, Gone Tomorrow' seems to sum it up appropriately, I think.
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Is that a lot?
Well deduced! Those are exactly the figures I read in an Asimov book twenty years ago!
(Correct spelling of "our" inserted in quote, and highlighted fyi.)
You are correct - noone has overthrown the theory of relativity. And the theory of special relativity states, that at the speeds near the speed of light space appears to be contracted. This means that if we could build a spaceship that could go with 0,9c and faster (0,99c, 0,999c, etc), then space would contract so much from its point of view, that it shouldn't be much of a problem to travel to the nearest stars, across the galaxy, or even to other galaxies.
Of course, the other matter to be taken into account is time dilation, which will be so big at the speeds involved, that if the spaceship ever wanted to return to earth, it would find that thousands or millions of years have passed there. Basically, from earths perspective the spaceship travels to the other end of the galaxy at the speed the ship is actually travelling. From earths point of view, there is no space contraction and it takes an enormous amount of time for the space ship to get anywhere.
I will also add some examples of how many times the space will be contracted and the time dilated at some relativistic speeds.
The figures are calculated using the lorentz transformations equation.
So the only thing that needs to be done, is to build a spaceship that can move at a speed high enough. Which will probably prove to be difficult, since the mass of the spaceship will also increase with the speed by the same amount as the space contracts. And the spaceships that travel so far without any hope of returning to the earth it remembered should probably contain enough habitants and technology to produce a vital colony, once it found a suitable planet at its destination.
Maybe a little off topic, but here goes:
A thing occurred me a while ago, while watching some sci-fi show.
Let's assume for the sake of my argument that within a thousand years of discovering radio communication, a civilization (that doesn't blow itself to smithereens) eventually progresses scientifically to the point where supra-light travel becomes possible.
Let's assume that there are numerous species evolved in the universe, and that each one of those species that evolves to the point where they are capable of developing their own versions of Howdy Doody, follows a similar thousand year trek to interstellar travel. (That puts our own deadline at around 2900 AD. If supra-light speed is achieveable in our universe, I think we will have discovered it by then.)
Here's the final piece of the puzzle that is my argument: if you can discover a method for sending physical objects through space faster than light, then you have most likely discovered concurrently a method for sending information faster than light. And if you can do that, why bother pissing around with electromagnetic communications?
What this means, if you buy my premises, is that any intelligent life out there in the great wide universe is only likely to broadcast signals that we can currently detect for a window of about a thousand years.
And that means you need the following ducks in a row for SETI etc. to confirm the existence of alien life using the current scheme of electromagnetic detection: the other planets must be suitable for life, for long enough for life to evolve after the unbelieveably rare occurence of that first spark of life hitting the planet's surface, and that evolution has to be so precisely in synch with our own (after accounting for the propagation delays between our planets) that their thousand year window has to at least fractionally overlap with our own.
Some great points I never thought of before.
I like the 1000 year window and the inevitable disuse of elctromagnetic communications.
There are three possible answers:
1) There is no "chatter" to detect.
2) Our methods of eavesdropping are woefully inadequate.
3) ET, looking to send signals back and forth as cheaply as possible, employs the most efficient communications techniques. Blasting massive radio signals out in all directions probably doesn't qualify as "most efficient".
Of the three, the problem of #2 is so overbearing that trying to draw conclusions is somewhat meaningless at this time.
Assuming for a moment that only we and one other ET civilization exist in the Milky Way, I'm able to make a prediction that has a high chance of being true:
We are the most dangerous thing in the entire galaxy to ET.
Fermi's Paradox, when it boils down to it, must rely upon one of two propositions to explain a lack of intelligent life in the galaxy:
1) We are the result of a unique set of circumstances that has occurred nowhere else in 100+ billion stars.
2) Intelligent life does not endure for any great length of time.
Neither supposition is particularly compelling, not in the least because another set of possibilities exist that have a higher chance (IMO) of being true than either #1 or #2 above:
1) We are unable to properly scan the galaxy for signs of interstellar communications at this time. By definition, we are looking for signal strengths as found here on Earth, not some non-existent multi-terrawatt beacon. (Indeed, if we find it, our slothy civil services can then cite undeniable proof that there are greater wastes of public funds in the galaxy...)
2) Anything intelligence that has detected us lacks an incentive to communicate with us.
I think the only meaningful debate must concern travel to other solar systems within our galaxy. One order of magnitude at a time!
Within this poster's morass of manias is the above excerpt, which, IMO, is amongst the cleverest observations on the subject I've yet to read here. Kudos.
And having made said clever point, he proceeds to fall flat on his face! If ET wants us dead, we are toast, and without need for fancy chemistry-altering, trans-galactic rayguns, I might add. Any civilization capable of getting to Earth should be capable of running stuff into it at near-lightspeed velocities. Question: Assuming a velocity of .9 C, how heavy does an object have to be in order to liquefy the Earth's crust?
Colonization would be a function of a number of things. First, the question of why it is necessary. Next, how it is to be done (which reflects upon both the technological problems involved, the resources available, and the objectives in doing so). Finally, reconnaissance; how do we discover where it is we want to go?
Before any colonization will take place, all of the above problems will have to be solved. My guesses are as follows:
Reconnaissance: I'm thinking that better observational techniques can tell us a great deal about which stars around us are the most interesting. Perhaps, to identify with reliability systems with Earth-like planets at the correct distance from their stars, and even knowledge of their elemental composition. Certainly methods must exist to allow us a rough sort for which systems, for whatever reason, interest us.
The most efficient probe, it seems to me, must be very small, very light, and very fast. Any lack of capability inherent in being small must be compensated for by the ability to send many probes of differing (but complementary) function. The method of propulsion would be Sol-based (to save weight on the probe). Say an electromagnetic rail gun, or laser arrays, or both. I'm picturing tiny, very sophisticated robots being flung in numbers through distant systems at truly ridiculous velocities.
In terms of method, assuming the objective is to establish a human colony, the most efficient system would probably be to send some sort of system with precise instructions on how to replicate human DNA from scratch. No humans, no DNA, no eggs would go. All of that could be constructed at the other end in due time.
Most people picture a ship of sorts, but I'm guessing otherwise. Ships are too slow and too heavy. Why do anything if it takes 10,000 years? If a small probe can be designed with the capability to de-accelerate from very high speeds, then we could fire thousands of probes into a system, and they'd construct in orbit whatever machines were necessary to do the job, right there on site.
As to why we'd go in the first place: the only answer I can see is that there is no choice (a danger to our system), or the potential for profitable economic activity.
If we consider the speed of light as a limit, then it would still take an enormous amount of time to get any information out of the probes, since they would need to first get to the distant solar systems and then send back the information gathered aswell.
If we are talking about big distances, then the acceleration/decceleration phase shouldn't be too time-consuming, when compared to the time of travel itself.
If there's a danger to our system, then I'd imagine a departure taking place as soon as possible, and the exact destination would be specified later, when more precise measurments have been done from the ship, once it has gotten closer to other solar systems. If we're talking about a colonization ship, where tens of thousands of people live anyway, then some telescopes and research equipment wouldn't be too heavy to throw in aswell.
From the earths point of view, the rest of the galaxy is quite unreachable, since getting information from anywhere would take atleast twice the distance in lightyears time and the galaxy is tens of thousands of lightyears in size. That is why I suggested the near-lightspeed colonization ship, since at that speed the trip wouldn't be too long for the people inside.
Ofcourse that kind of technology would probably take much longer to develope, than the small probes.
At some point in the future the speed of light becomes the limit. But for now, the problem is the truly silly amounts of energy needed to make anything at all go a "reasonable" speed in the galaxy. A colony ship weighing 20,000 tons requires 10^26 Joules of energy to accelerate to .8c. That's 7 BILLION nuclear powerplants operating full-out for 9 solid months. But if the parcel is very, very light, the energy constraints look, if not sane, then at least less loony. A 1kg object accelerated to .2c needs only 1.26 nuclear powerplants going full-out for 9 months. Seems to me that it would be easier to design a probe that can do something useful weighing 1kg than solve the energy requirements of a heavy object moving faster. At .2c, a 1kg probe could pass through the Proxima system and report back within 24 years.
But if we are to assume a colony ship is traveling at an average of .001c and moving to a star 10 light years away, takes, it should take about 10,000 years to reach it's destination. The logic of the situation virtually dictates that no people should be sent. They'll all be dead long before reaching the target anyways, so why bother? Sure, in theory some distant descendent generation might eventually arrive, but intellectually speaking, what's the difference between that and having a computer biolab construct the first colonists out of material found in the new solar system? If we can design the biolab to be really, really light and resistant to high g forces, we can get it there faster, and we don't have to worry about details like drive radiation killing everyone
Dont you just hate it when someone good at maths comes along Please Register or Log in to view the hidden image! You lost me after "At..............."
Actually, I had to get my brother to email me the formulas so I could do the calculations....
One thing about starship travel is that acceleration equals speed equals acceleration (or something) does not a ship double its acceleration every so often. If that makes sesne.
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