The future of mankind discussion.

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The future of mankind discussion.

Postby Stucky101 » Sun Apr 01, 2007 4:29 am UTC

I've always been interested and excited about the future of our civilization. I'm not talking about an ethnic group or a single nation. I'm talking about us as a single intelligent species. This topic is for people to discuss what they think the future of mankind is. Whether we'll be wiped out in a collision between Earth and some huge asteroid. Or if we will triumph as a Galactic Civilization discovering the secrets of the universe. What ever you think will become of us, please post it.

As for me. I think humanities future is bright. With the increasingly rapid growth of technology it will only be a matter of time before we go to the stars. Taking up residence in other worlds beyond our own solar system. Becoming what I like to call a Galactic Nation. I like to think that owning a space ship will be as common as own a car. MAN that would be awesome! ^_^

That's just about all I have to say. Please post your thoughts.


P.S. I originally had this topic in the General sub forum. But quickly found out it was the wrong one since people kept posting pictures of their nipples. So please excuse the topic spamming.
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Re: The future of mankind discussion.

Postby Solt » Sun Apr 01, 2007 5:19 am UTC

Stucky101 wrote:With the increasingly rapid growth of technology it will only be a matter of time before we go to the stars. Taking up residence in other worlds beyond our own solar system. Becoming what I like to call a Galactic Nation. I like to think that owning a space ship will be as common as own a car. MAN that would be awesome! ^_^



I agree that it would indeed be tremendously awesome, but I don't think it's possible. I think we've established to reasonable certainty that nothing can move faster than the speed of light, or even close without experiencing horrible time dilation. As a result, while travel to the stars is possible it will be entirely pointless, as only the travelers will be around to see them up close. Although I read somewhere that thanks to time dilation a group of travelers could cross the entire Milky Way galaxy in little over 100 years. Of course human civilization would be like 100,000 years ahead.

I see a future where we've managed to fix all our problems. Basically, we've figured out everything- we know exactly how the global ecosystem works and can control it perfectly in all aspects, we are masters of the human body and can extend and even create life without nature's help. Energy production is cheap and is done in a non-impactive way, perhaps off world. Computer technology is perfectly compatible with the human brain, to the point where we could even exist, consciously, on the internet.

And of course supply is no longer a problem as we can manufacture anything for any one for next to nothing. No wars or conflicts over resources. All disease and hunger conquered. Lots of vacation time.

Of course there are things that may or may not be possible, things that we don't even know about, that could change everything. Like the development of matter/energy conversion. If that's possible who knows what crazy things we could do. Earth getting crowded? Ok, synthesize a new one! Ever wonder why gravity acts instantly even over great distances? Maybe we will be able to communicate instantly over interstellar distances by sending data in "waves" through space-time. Or something. The possibilities are endless!

One thing is for sure, I bet most people would rather stick around to find out what will happen than blow up the whole world.

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Re: The future of mankind discussion.

Postby Stucky101 » Sun Apr 01, 2007 5:47 am UTC

I think we've established to reasonable certainty that nothing can move faster than the speed of light, or even close without experiencing horrible time dilation.

Yes I do know of Einstein's theory of relativity. And while it may sound too amazing to be true, I believe that with time and great minds technology has no limits what so ever. With the surprising increase in knowledge over our universe's physics. I with out a doubt believe that it's possible to bend or tear space to create a "wormhole". Wormholes wouldn't be the only way to travel too. I won't go into much explaining of it, but it's been found that through quantum entanglement, it may be possible to actually move faster than light. It sounds insane and nothing but sci-fi. But that's what people thought about space flight not just a century ago. :wink:

Ever wonder why gravity acts instantly even over great distances?

I don't know who or where you got that from. But gravity does not at all act instantly at any distance. If that were true it'd have to travel faster than the speed of light and that's not possible. Gravity actually travels at the speed of light. So for example, the sun's light takes 8 minutes to reach earth. So if the sun would all of a sudden disappear for no reason, the earth will stay in orbit for another 8 minutes before speeding out into space.
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Re: The future of mankind discussion.

Postby Peshmerga » Sun Apr 01, 2007 5:56 am UTC

Stucky101 wrote:And while it may sound too amazing to be true, I believe that with time and great minds technology has no limits what so ever.


While I share your optimistic views that humanity will find a way, I wouldn't say it loud enough for the physics guys to come in and shoot it down. They are awfully intimidating within their own context :o
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Postby Xial » Sun Apr 01, 2007 5:57 am UTC

I see a time when humans will have abandoned their bodies for mechanical frames in which you stick the brain. These bodies will be entirely customizable and will extend human life thousands of years.

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Re: The future of mankind discussion.

Postby Solt » Sun Apr 01, 2007 6:09 am UTC

Stucky101 wrote:I don't know who or where you got that from. But gravity does not at all act instantly at any distance. If that were true it'd have to travel faster than the speed of light and that's not possible. Gravity actually travels at the speed of light. So for example, the sun's light takes 8 minutes to reach earth. So if the sun would all of a sudden disappear for no reason, the earth will stay in orbit for another 8 minutes before speeding out into space.



I actually googled it before posting, I suggest you do the same :)

Apparently astronomical observations have shown that gravity MUST act several million to several billion times the speed of light. Perhaps even instantly.

Here's an example I sort of understood:

If gravity only acted at the speed of light, planets would veer off course. Let's pretend gravity acts at the speed of light. The sun is moving through the galaxy. Say the sun moves a given distance, then 8 minutes later we here on earth start feeling a pull from the sun's new location. Well, our orbit would hardly be as perfectly elliptical as it is. It would be some sort of weird ass spiral that accounts for the fact that both bodies are accelerating separately. Sometimes the sun would be pulling us back along our orbit, some times pulling us forward. We possibly would have flown off into space or even into the sun because our orbit would be so erratic.



Edit, Also:

And while it may sound too amazing to be true, I believe that with time and great minds technology has no limits what so ever


I really do hope you are right but is there any logical reason to believe that such a thing will happen? Or are you just hoping for it so bad, you expect it to come true? Is it any different from believing you will end up in heaven when you die (it IS possible, just very unlikely...)?

Wanting something will not make it so.

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Postby Hawknc » Sun Apr 01, 2007 6:15 am UTC

Solt, have you done any astrophysics study? General relativity gives a pretty good argument for the speed of gravity being c. So I'm gonna ask you to PPOR if that's alright.

(PPOR = post proof or retract, for those new to the internet)
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Postby Solt » Sun Apr 01, 2007 7:16 am UTC

Hawknc wrote:Solt, have you done any astrophysics study? General relativity gives a pretty good argument for the speed of gravity being c. So I'm gonna ask you to PPOR if that's alright.



No, I haven't formally studied any of this stuff. So I'm in no position to judge for myself. This guy, however cites references and that's generally a good thing. So I believed him.

http://metaresearch.org/media%20and%20l ... peikin.asp

Apparently there are at least 6 experiments demonstrating that v_g >> c, while there is only one showing v_g = c and it is flawed.

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Postby Vaniver » Sun Apr 01, 2007 7:46 am UTC

If gravity only acted at the speed of light, planets would veer off course. Let's pretend gravity acts at the speed of light. The sun is moving through the galaxy. Say the sun moves a given distance, then 8 minutes later we here on earth start feeling a pull from the sun's new location. Well, our orbit would hardly be as perfectly elliptical as it is. It would be some sort of weird ass spiral that accounts for the fact that both bodies are accelerating separately. Sometimes the sun would be pulling us back along our orbit, some times pulling us forward. We possibly would have flown off into space or even into the sun because our orbit would be so erratic.
That's the fun thing. Our orbits aren't perfectly elliptical. In fact... the error is just about what general relativity would predict. Funny how things work.

For clarification: this is what my professors with PhDs in Astronomy and Physics say, so this comes with the skewed credibility that is someone on the internet (since this is coming through me). You can also check out this.

As for the original post- I'm optimistic about human survival; I'm not 'optimistic' about the future, in the sense that I believe life will either continue very similarly to how things are now (with minor improvements) or will change so drastically that our predictions are near-worthless.

Someone, sometime, is going to go to another planet. Whether or not their colony will fail hideously is up for grabs (although always bet on failure when it comes to new, untested technology). Assuming no FTL communication or travel (because it's silly to assume you'll have that), they'll essentially create a separate history, sending messages to humans centuries after the humans who sent messages to them. But even then, it's not like you'll be able to send much of a message from hundreds of lightyears away.
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Postby Hawknc » Sun Apr 01, 2007 8:06 am UTC

Fair enough. I'm going to counter with some peer-reviewed articles:

Aberration and the Speed of Gravity argues a speed cg = c

The speed of gravity in general relativity essentially argues cg = c, but it's more complicated than that

Model-dependence of Shapiro time delay etc says it's difficult to tell from current experiments

The problem is that this is currently a very new field of experimentation. The current theory supports cg = c, and there's no mathematical modelling to suggest otherwise yet, but the experiments being done aren't universally agreed upon.
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Re: The future of mankind discussion.

Postby hyperion » Sun Apr 01, 2007 9:32 am UTC

Stucky101 wrote:With the increasingly rapid growth of technology it will only be a matter of time before we go to the stars.
Possible, but i doubt we'll last the next 1000 years.

There'll be a plague, or nuclear war, or something that destroys all. With the way things are today, i wouldn't be surpised if, in <20 years, everyone got sick of repression and rebelled, leaving the world in ruins. As much as i don't want it to happen, it probably will.
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Postby Phy » Sun Apr 01, 2007 10:39 am UTC

I have... well, not much hope that we'll outlast the oncoming combined climatic and energy catastrophe. If we can punch through that, we can punch through damn near anything.

I have not much hope, but I have hope.

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Postby aldimond » Sun Apr 01, 2007 6:31 pm UTC

I believe that we could survive the next thousand years if we found a way to provide people with a good quality of life while the population declined.

Unfortunately all of the powerful economies at the moment demand growth. What the fuck ya gonna do, 'eh?
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Postby Stucky101 » Sun Apr 01, 2007 6:39 pm UTC

While we will die out some day. I don't think it'll be anytime soon. I think it's very possible that we'll live for at least another 10,000 years. And population growth will only help that fact. It's easier to kill 1 fish than 2. :wink:
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Postby Xial » Sun Apr 01, 2007 6:58 pm UTC

Stucky101 wrote:While we will die out some day. I don't think it'll be anytime soon. I think it's very possible that we'll live for at least another 10,000 years. And population growth will only help that fact. It's easier to kill 1 fish than 2. :wink:


Except of course if those two fish are competing for the same resources and one fish, knowing that it will loose that fight, decides to destroy the resource so that no one can have it.

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Postby Belial » Sun Apr 01, 2007 7:06 pm UTC

Or just uses up all the resources as fast as possible so that both starve.
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Postby Tchebu » Sun Apr 01, 2007 8:24 pm UTC

If there's anything people really like... its being alive. This means that no matter how we mess up the planet, when it REALLY starts to hurt (i.e. half the population dies or something) we'll start making ways to survive. Invent real new energy sources etc. We could have invented them a long time ago already if people concentrated on it. But noone needs this energy except the enviromentalists. Everyone else is happy because we have oil, and the oil companies are even happier because they get money from it... if we start to die out, noone will care about oil, they will care about "clean" energy, and then the scientists will suddenly find themselves getting all the support they need... so we're not dying any time soon... well at least the "surviving" half.

As for the gravity speed... how far does the Sun travel in 8 minutes? If gravity was instant, the earth would be experiencing the suns gravitational pull from the point that distance ahead of where we actually SEE the Sun... does that happen? Also, this would imply that there would be areas of space that would have a gravitational field but no visible light coming from them because the light from that star or something wouldn't be here yet... wait... i think i just solved the "dark matter" problem... IM A GENIUS!!!... (ok... no...) :D

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Postby Belial » Sun Apr 01, 2007 8:25 pm UTC

We've always survived before, so we'll keep surviving?

There are some serious logical problems with that.
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Postby Stucky101 » Mon Apr 02, 2007 12:05 am UTC

Belial wrote:We've always survived before, so we'll keep surviving?

There are some serious logical problems with that.

What his point is Belial. When we as a species begin feeling the effects of near extinction, then we'll all go into survival over drive. Almost like adrenaline.
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Postby Belial » Mon Apr 02, 2007 12:07 am UTC

Or we'll just tell ourselves "Oh, we don't have to worry about it, we're resourceful, we'll survive, we always have" until it's too late to do anything.
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Postby Xial » Mon Apr 02, 2007 12:12 am UTC

Stucky101 wrote:
Belial wrote:We've always survived before, so we'll keep surviving?

There are some serious logical problems with that.

What his point is Belial. When we as a species begin feeling the effects of near extinction, then we'll all go into survival over drive. Almost like adrenaline.


Except that in the past when we went into survival overdrive we did not have a big red button which would allow us to vaporize those we were competing with.

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Postby Vaniver » Mon Apr 02, 2007 1:49 am UTC

With the way things are today, i wouldn't be surpised if, in <20 years, everyone got sick of repression and rebelled, leaving the world in ruins.
Isn't the sum total of human history people "rebelling"?

We have bigger guns, now, and better explosives, and deadlier poisons. But we probably won't kill everyone.

This means that no matter how we mess up the planet, when it REALLY starts to hurt (i.e. half the population dies or something) we'll start making ways to survive.
The question is whether it'll be hundreds who survive in Fallout-style vaults, or billions.
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Re: The future of mankind discussion.

Postby gmalivuk » Mon Apr 02, 2007 5:16 pm UTC

Solt wrote: I read somewhere that thanks to time dilation a group of travelers could cross the entire Milky Way galaxy in little over 100 years. Of course human civilization would be like 100,000 years ahead.


Not sure that's true, unless we find a way to dampen acceleration.

I calculated once that at continuous 1g (subjectively), it'd take 245 years to reach the galactic center.

Of course, I don't remember for sure if I took into account both time and length changes near lightspeed... (I'll have to come back to that once I've redone the calculations.)
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Postby fjafjan » Mon Apr 02, 2007 5:48 pm UTC

Where humans should go? I think it's essential that we do not get too obsessed with technology or our greatness that we forget Human suffering and equality etc etc, Going to Mars is cool but if we still have people dying of AIDS or Malnurishment then it's pretty wasted.
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Postby gmalivuk » Mon Apr 02, 2007 7:09 pm UTC

Okay, so I was wrong. If you keep up the local external acceleration (how fast you're moving through the universe compared to how fast you experience time onboard ship), the local internal acceleration (what it feels like onboard) drops to zero. So as you're going faster, you can increase the local external acceleration without any ill effects onboard.

So I don't know how to figure out an exact figure, but I guess you could definitely cross the galaxy in less than 500 years local time.

(You can't, however, keep the internal acceleration at 1 g, just like you can't keep up the nonlocal acceleration, as this would result in reaching lightspeed in finite time.)
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Postby Vaniver » Mon Apr 02, 2007 7:23 pm UTC

(You can't, however, keep the internal acceleration at 1 g, just like you can't keep up the nonlocal acceleration, as this would result in reaching lightspeed in finite time.)
Internal acceleration in one direction, sure. You just build a cylindrical ship that can be useful both when the circles are the floors and when the outer walls (and concentric cylinders inside) are the floors (since you can get acceleration there by spinning it).

Although, actually, if you did that fairly late in the process, I suppose it would be harder to do. And you wouldn't get a direct switch anyway, so there would always be a point where a ball on the floor will roll to a corner of the room.
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Postby Gadren » Mon Apr 02, 2007 7:28 pm UTC

fjafjan wrote:Where humans should go? I think it's essential that we do not get too obsessed with technology or our greatness that we forget Human suffering and equality etc etc, Going to Mars is cool but if we still have people dying of AIDS or Malnurishment then it's pretty wasted.


Agreed, but I don't think it's a good stance to wait around to fix everything at point A before we start moving to point B. Here's something I wrote a while back (apologies if the tone sounds harsh -- it fit more with the heated debate in which I originally posted it).



From a certain episode of Babylon 5:

Reporter: "After all that you've just gone through, I have to ask you the same question a lot of people back home are asking about space these days. Is it worth it? Should we just pull back, forget the whole thing as a bad idea, and take care of our own problems, at home?"

Sinclair: "No. We have to stay here, and there's a simple reason why. Ask ten different scientists about the environment, population control, genetics - and you'll get ten different answers. But there's one thing every scientist on the planet agrees on: whether it happens in a hundred years, or a thousand years, or a million years, eventually our sun will grow cold, and go out. When that happens, it won't just take us, it'll take Marilyn Monroe, and Lao-tsu, Einstein, Maruputo, Buddy Holly, Aristophanes - all of this. All of this was for nothing, unless we go to the stars."


It's very doubtful we'll ever fix everything on Earth. Why do we need to get everything finished here before starting elsewhere? The problem with this thinking is that it leads to the kind of contentment with the status quo that prevents progress. If this line of thinking had been held by everyone, we would never have gone anywhere at all! Sail to America? No -- there are still problems in Europe! Build the Roman aqueducts? No -- what about the plight of the Gauls...shouldn't that come first? Go over that hill beyond our thatched hut? No -- what about the rest of the hungry cavemen?

From one particularly wise Slashdot comment:

Space offers us an unlimited future. As soon as anyone can exist in space, we have that limited backup (sort of). As soon as we can build, garden, live and breed in space, then we have that unlimited future.

The problems people cite as reasons not to explore have always been with us, read Tacitus, Sun Tzu or the Hammurabi column for proof. The "Fix us first" crowd wants Utopia on Earth. There is no such thing, unless you can stamp out human nature. If their arguments won out, we'd still be clubbing antelope in Africa, "Oh, no, don't walk north, you might stub your toe."

Space is our future. Lead, follow or get out of the way. The meek shall inherit the Earth, the rest of us are going to the stars.


------
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Anyway, my hopes for the future of mankind mainly revolve around the idea of a technological singularity. Yeah, I know it's kind of a "Rapture of the Nerds," but it's held a special place in my mind for some time. :D

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Postby Yakk » Mon Apr 02, 2007 7:56 pm UTC

There is a wonderful shortcut to figure out the subjective time it takes to travel between two locations, given that you are accellerating at a constent rate and flipping over, taking into account relativity.

It is ... ignore relativity.

It happens to work. :)

So, to reach 50,000 ly @ 10 m/s^2, we have:

50,000 ly = 5*10^4 = 1/2 * 10 * t^2
t^2 = 10^4 ly/(m/s^2)
t = sqrt( 10^4 c * 1 y/(1 m/s^2) )
reformatted to:
( 10^4 (c * year) * second*second/m )^(1/2)
and plugged into google:
((10^4) * (c * year) * ((second * second) / m))^(1 / 2) = 308.221554 years

A trivial turnover time, followed by an equal decelleration, gives us 100,000 light years in 617 subjective years at 1 gravity of accelleration.

And yes, you can keep up a local-frame accelleration of 1 gravity indefinately, given unlimited-but-finite reaction mass and energy.

To the rest of the universe, you aren't accellerating at 1 g: instead, you are squeezing yourself into a pancake and slowing down.

To you, you are accellerating at 1 g, but as you do it for long periods of time, the rest of the universe turns into a pancake. By the midpoint of your journey, the entire 100000 lightyear-wide galaxy seems significantly less than 600 lightyears across.

So you don't see yourself moving faster than light, and others don't see you moving faster than light.

The trick of using newtonian mechanics to calculate such a trip is just a really neat way to avoid all of the relativity effects -- they happen to cancel out when solving this particular problem!

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Postby Stucky101 » Mon Apr 02, 2007 9:02 pm UTC

Gadren wrote:
fjafjan wrote:Where humans should go? I think it's essential that we do not get too obsessed with technology or our greatness that we forget Human suffering and equality etc etc, Going to Mars is cool but if we still have people dying of AIDS or Malnurishment then it's pretty wasted.


Agreed, but I don't think it's a good stance to wait around to fix everything at point A before we start moving to point B. Here's something I wrote a while back (apologies if the tone sounds harsh -- it fit more with the heated debate in which I originally posted it).



From a certain episode of Babylon 5:

Reporter: "After all that you've just gone through, I have to ask you the same question a lot of people back home are asking about space these days. Is it worth it? Should we just pull back, forget the whole thing as a bad idea, and take care of our own problems, at home?"

Sinclair: "No. We have to stay here, and there's a simple reason why. Ask ten different scientists about the environment, population control, genetics - and you'll get ten different answers. But there's one thing every scientist on the planet agrees on: whether it happens in a hundred years, or a thousand years, or a million years, eventually our sun will grow cold, and go out. When that happens, it won't just take us, it'll take Marilyn Monroe, and Lao-tsu, Einstein, Maruputo, Buddy Holly, Aristophanes - all of this. All of this was for nothing, unless we go to the stars."


It's very doubtful we'll ever fix everything on Earth. Why do we need to get everything finished here before starting elsewhere? The problem with this thinking is that it leads to the kind of contentment with the status quo that prevents progress. If this line of thinking had been held by everyone, we would never have gone anywhere at all! Sail to America? No -- there are still problems in Europe! Build the Roman aqueducts? No -- what about the plight of the Gauls...shouldn't that come first? Go over that hill beyond our thatched hut? No -- what about the rest of the hungry cavemen?

From one particularly wise Slashdot comment:

Space offers us an unlimited future. As soon as anyone can exist in space, we have that limited backup (sort of). As soon as we can build, garden, live and breed in space, then we have that unlimited future.

The problems people cite as reasons not to explore have always been with us, read Tacitus, Sun Tzu or the Hammurabi column for proof. The "Fix us first" crowd wants Utopia on Earth. There is no such thing, unless you can stamp out human nature. If their arguments won out, we'd still be clubbing antelope in Africa, "Oh, no, don't walk north, you might stub your toe."

Space is our future. Lead, follow or get out of the way. The meek shall inherit the Earth, the rest of us are going to the stars.


------
(I wrote this last June -- you can read the whole thing at http://playfulseraph.blogspot.com/2006/ ... nswer.html )


Anyway, my hopes for the future of mankind mainly revolve around the idea of a technological singularity. Yeah, I know it's kind of a "Rapture of the Nerds," but it's held a special place in my mind for some time. :D

Gadren, that is the best argument I've heard in a long time. I'm saving this as a notepad doc! Good job man.
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Postby Belial » Mon Apr 02, 2007 9:03 pm UTC

Garden:

Loved that episode, loved that argument.
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Postby gmalivuk » Mon Apr 02, 2007 10:50 pm UTC

Yakk wrote:There is a wonderful shortcut to figure out the subjective time it takes to travel between two locations, given that you are accellerating at a constent rate and flipping over, taking into account relativity.

It is ... ignore relativity.


See, that's what I thought at first. But then I started confusing myself by considering two kinds of local acceleration. It seems like the rate of change of your apparent speed through the universe is different, at relativistic speeds, from the acceleration you feel onboard your ship.

I was figuring that the local external acceleration is du/dtau where u is the "local external velocity" and tau is your experience of time. (u is v/sqrt(1-v*v) (where v=1 is c), and so u=c means that in one year onboard, you move one lightyear through space). Whereas local internal acceleration (what you feel) is less than this, by a factor of sqrt(1-v*v). Then again, after working on related equations for awhile, I realized I was making some mistakes. So perhaps the one where I look at two different kinds of acceleration is one of them. I'll have to go back and do it yet again now. :-)
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Postby Bluesprite » Tue Apr 03, 2007 1:53 am UTC

The possibility of a technological singularity frightens and saddens me in a way that I can quite express.
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Postby Shadowfish » Tue Apr 03, 2007 4:01 am UTC

On topic: I think that getting to another star will take tens of thousands of years. Not tens of thousands of years from now, but tens of thousands of years from the first time people start thinking seriously about getting to another star.

The energy required to get a macroscopic object to relativistic speeds is unimaginable. Either you have to spend thousands of years gathering enough energy make whatever fuel your ship will use, or you need to make the trip at non-relativistic speeds, and so the people on the ship will experience thousands of years of subjective time. This makes it a bit less likely that we will get to another star.

Slightly less on topic:
There is a wonderful shortcut to figure out the subjective time it takes to travel between two locations, given that you are accellerating at a constent rate and flipping over, taking into account relativity.

It is ... ignore relativity.

It happens to work. :)


Could you give an argument for this? Not cause I don't believe you, but because its too cool for me not to understand.

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Postby Stucky101 » Tue Apr 03, 2007 6:08 am UTC

Shadowfish wrote:On topic: I think that getting to another star will take tens of thousands of years. Not tens of thousands of years from now, but tens of thousands of years from the first time people start thinking seriously about getting to another star.

The energy required to get a macroscopic object to relativistic speeds is unimaginable. Either you have to spend thousands of years gathering enough energy make whatever fuel your ship will use, or you need to make the trip at non-relativistic speeds, and so the people on the ship will experience thousands of years of subjective time. This makes it a bit less likely that we will get to another star.

That's what makes quantum entanglement so beautiful. I don't entirely understand it, but basically it may enable us to travel almost instantly anywhere. And yes this does defy theory of relativity I know. It's something they're still trying to figure out. Quantum physics is quite strange.

Check it out on wiki if you don't know what it is.
http://en.wikipedia.org/wiki/Quantum_entanglement (Quantum Mechanics)
http://en.wikipedia.org/wiki/Quantum_teleportation (Quantum Teleportation)
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Postby cmacis » Tue Apr 03, 2007 8:14 am UTC

Yes we should spread to other stars to preserve everything humanity has worked for since the sun will die one day, but so will the universe one day. Unless we work around the second law of thermodynamics then the useful energy in the universe will be gone. All that will be left is too little heat over too large a universe.

Alternatively the universe could start contracting and collapse back to a point. Possibly there's a solution where everything bounces off before reaching the point and expands again until it starts contracting. Maybe with sufficiently advanced technology we could survive in whatever form we have achieved by then.
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Postby Vaniver » Tue Apr 03, 2007 2:11 pm UTC

That's what makes quantum entanglement so beautiful. I don't entirely understand it, but basically it may enable us to travel almost instantly anywhere. And yes this does defy theory of relativity I know. It's something they're still trying to figure out. Quantum physics is quite strange.
Quantum entanglement does not allow you to travel instantly, communicate instantly, or defy relativity. Sorry.

[edit]Also, read your links. Both of them state that it doesn't work that way in the first paragraph.
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Postby Shadowfish » Tue Apr 03, 2007 2:13 pm UTC

Damnit Vaniver, you beat me to it.

Still, there's a very good reason you can't travel faster than light. http://en.wikipedia.org/wiki/Causality_%28physics%29

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Postby gmalivuk » Tue Apr 03, 2007 5:10 pm UTC

Shadowfish wrote:Either you have to spend thousands of years gathering enough energy make whatever fuel your ship will use, or you need to make the trip at non-relativistic speeds, and so the people on the ship will experience thousands of years of subjective time. This makes it a bit less likely that we will get to another star.


Hasn't this already been discussed to death? Taking all your fuel with you when the universe is full of fusable hydrogen is just plain stupid. It's like spending months on a river and bringing thousands of gallons of water in the boat when you could instead just get a little purifier unit.

Granted, we have no way of knowing at this point whether ramjets are actually feasible modes of travel, but we also have no particular evidence to say they're not. And if we had one, continuous acceleration over lightyears of distance would be possible.

Speaking of which, why you can ignore relativity:
When you're traveling at velocity v (where v=1 is the speed of light), your experience of time is contracted by a factor of Sqrt(1-v^2). That is, if you're travelling at, say, 2/Sqrt(5), your experience of time is 1/Sqrt(5) the rate of people in a nonmoving frame. So when you consider the time it takes you to get from one star to another, knowing the distance in the frame of the stars themselves, you can treat your subjective velocity as 2/Sqrt(5) / 1/Sqrt(5). That is, twice lightspeed.

I had confused myself briefly yesterday, but calculating it again after Yakk's comment reassured me that the same is true for acceleration. If the acceleration you feel onboard is about 1 lightyear/year^2 (conveniently fairly close to one g), then after one year you would seem to be going c, after two, 2c, and so on. (That is, after two subjective years, your actual velocity is 2/Sqrt(5), so your subjective velocity is 2.)

Note that from your frame, the rest of the universe actually squishes itself in the direction of travel, to exactly counter the time dilation. So after two (subjective) years you can compute that you're still only going at the perfectly legal speed of 2/Sqrt(5). The stars you're heading towards are just a lot closer to you than they were before you started moving so fast.
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Postby Yakk » Tue Apr 03, 2007 5:21 pm UTC

Shadowfish wrote:On topic: I think that getting to another star will take tens of thousands of years. Not tens of thousands of years from now, but tens of thousands of years from the first time people start thinking seriously about getting to another star.

The energy required to get a macroscopic object to relativistic speeds is unimaginable. Either you have to spend thousands of years gathering enough energy make whatever fuel your ship will use, or you need to make the trip at non-relativistic speeds, and so the people on the ship will experience thousands of years of subjective time. This makes it a bit less likely that we will get to another star.


KE = [L-1] * m_0 * c^2

L = 1/sqrt(1-v^2)
with v measured in "fraction of c". This also happens to be the time dialation factor. (L is known as the Lorentz factor)

Travel time = D * L/v

with v close to c, this varies with L and D: the details of how close our v is to c are pretty unimportant.

So, let's say we want a 10:1 time ratio: 1 year travel time for every 10 lightyears of distance, roughly.

L = 10. So KE = 9*m_0*c^2.

Ie, we need 9 times our mass in energy.

Suppose our ship weighs 10^9 kg (a million tonnes). Then we need 10^10 kg of energy.

The sun puts out:
4* 10^33 ergs/second /c^2 = 5*10^9 kg of energy per second.

So to get a million tonne ship up to a lorentz factor of 10 speed, we need 2 seconds of the sun's energy output.

This is a tough problem: it requires either a large pile of work on the part of a type 1 civilization, or reaching a type 2 civilization.

The harder problem is, of course, slowing down. :) But practically, you don't have to travel at a 10 times time dilation factor.

(BTW, a Lorentz speed of 10 is .995 c).

Slightly less on topic:
There is a wonderful shortcut to figure out the subjective time it takes to travel between two locations, given that you are accellerating at a constent rate and flipping over, taking into account relativity.

It is ... ignore relativity.

It happens to work. :)


Could you give an argument for this? Not cause I don't believe you, but because its too cool for me not to understand.


I think I ran the math once, or saw it run. Basically, the time dialation and the space dialation cancel out. :)

...

Conceptually: newtonian dynamics is nearly perfect approximation for what things act like in any inertial frame of reference. As you accellerate, the universe starts looking wierd -- but your frame of reference still seems normal to you.

It takes about 6 months to reach 1/2 c. During that time, the universe squishes about 15%: relativistic effects are not that pronounced. You then drop a rock. You then accellerate for another 6 months local time. That rock you dropped is now 15% squished relative to you. :)

...

I can't remember if it took special or general relativity to prove the result -- I think special was enough.

For some evidence:
1/2 * (10 m/s^2) * (6 years)^2 / (c*1year) = 18ish
http://musr.physics.ubc.ca/~jess/p200/str/str13.html
notes that a 6 year ship-time 1 g journey does an 18 ly flyby.

(the jess in question seems to be a physics prof at UBC.)

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Postby Vaniver » Tue Apr 03, 2007 9:32 pm UTC

Taking all your fuel with you when the universe is full of fusable hydrogen is just plain stupid.
But, that fusable hydrogen is rarely in a package that is easy to open; it'd be like not taking drinking water while crossing the Antarctic, trusting that you'll be able to melt and filter the snow.
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