Posted on 08/26/2013 4:29:42 PM PDT by LibWhacker
(Phys.org) —Scientists as eminent as Stephen Hawking and Carl Sagan have long believed that humans will one day colonise the universe. But how easy would it be, why would we want to, and why haven't we seen any evidence of other life forms making their own bids for universal domination?
A new paper by Dr Stuart Armstrong and Dr Anders Sandberg from Oxford University's Future of Humanity Institute (FHI) attempts to answer these questions. To be published in the August/September edition of the journal Acta Astronautica, the paper takes as its starting point the Fermi paradox – the discrepancy between the likelihood of intelligent alien life existing and the absence of observational evidence for such an existence.
Dr Armstrong says: 'There are two ways of looking at our paper. The first is as a study of our future – humanity could at some point colonise the universe. The second relates to potential alien species – by showing the relative ease of crossing between galaxies, it makes the lack of evidence for other intelligent life even more puzzling. This worsens the Fermi paradox.'
The paradox, named after the physicist Enrico Fermi, is something of particular interest to the academics at the FHI – a multidisciplinary research unit that enables leading intellects to bring the tools of mathematics, philosophy and science to bear on big-picture questions about humanity and its prospects.
Dr Sandberg explains: 'Why would the FHI care about the Fermi paradox? Well, the silence in the sky is telling us something about the kind of intelligence in the universe. Space isn't full of little green men, and that could tell us a number of things about other intelligent life – it could be very rare, it could be hiding, or it could die out relatively easily. Of course it could also mean it doesn't exist. If humanity is alone in the universe then we have an enormous moral responsibility. As the only intelligence, or perhaps the only conscious minds, we could decide the fate of the entire universe.'
According to Dr Armstrong, one possible explanation for the Fermi paradox is that life destroys itself before it can spread. 'That would mean we are at a higher risk than we might have thought,' he says. 'That's a concern for the future of humanity.'
Dr Sandberg adds: 'Almost any answer to the Fermi paradox gives rise to something uncomfortable. There is also the theory that a lot of planets are at roughly at the same stage – what we call synchronised – in terms of their ability to explore the universe, but personally I don't think that's likely.'
As Dr Armstrong points out, there are Earth-like planets much older than the Earth – in fact most of them are, in many cases by billions of years.
Dr Sandberg says: 'In the early 1990s we thought that perhaps there weren't many planets out there, but now we know that the universe is teeming with planets. We have more planets than we would ever have expected.'
The Acta Astronautica paper looks at just how far and wide a civilisation like humanity could theoretically spread across the universe. Past studies of the Fermi paradox have mainly looked at spreading inside the Milky Way. However, this paper looks at more ambitious expansion.
Dr Sandberg says: 'If we wanted to go to a really remote galaxy to colonise one of these planets, under normal circumstances we would have to send rockets able to decelerate on arrival. But with the universe constantly expanding, the galaxies are moving further and further away, which makes the calculations rather tricky. What we did in the paper was combine a number of mathematical and physical tools to address this issue.'
Dr Armstrong and Dr Sandberg show in the paper that, given certain technological assumptions (such as advanced automation or basic artificial intelligence, capable of self-replication), it would be feasible to construct a Dyson sphere, which would capture the energy of the sun and power a wave of intergalactic colonisation. The process could be initiated on a surprisingly short timescale.
But why would a civilisation want to expand its horizons to other galaxies? Dr Armstrong says: 'One reason for expansion could be that a sub-group wants to do it because it is being oppressed or it is ideologically committed to expansion. In that case you have the problem of the central civilisation, which may want to prevent this type of expansion. The best way of doing that get there first. Pre-emption is perhaps the best reason for expansion.'
Dr Sandberg adds: 'Say a race of slimy space aliens wants to turn the universe into parking lots or advertising space – other species might want to stop that. There could be lots of good reasons for any species to want to expand, even if they don't actually care about colonising or owning the universe.'
He concludes: 'Our key point is that if any civilisation anywhere in the past had wanted to expand, they would have been able to reach an enormous portion of the universe. That makes the Fermi question tougher – by a factor of billions. If intelligent life is rare, it needs to be much rarer than just one civilisation per galaxy. If advanced civilisations all refrain from colonising, this trend must be so strong that not a single one across billions of galaxies and billions of years chose to do it. And so on.
'We still don't know what the answer is, but we know it's more radical than previously expected.'
You are. And the fact that you don't know that you are tells anyone reading your posts why you don't understand what you're talking about.
The geometry of our universe is such that it is impossible to travel through space without also traveling through time. Moving from one point in space-time to another point in space-time faster than light always requires time travel from the original proper time of the traveler into his past; when he arrives at his destination, he is there before any simultaneous event seen in any inertial reference frame that includes his original location and his new location could be observed. In particular, this implies he could beam a message back to himself that arrives before he leaves.
Superluminal transmission of anything other than space-like quantum states always implies causality violations. Always. It's impossible to get around it, because the space-time we live in has this structure.
So was heavier-than-air manned flight, until the Wright brothers did it. Landing men on the moon was widely ridiculed at one time, because it seemed so far-fetched.
No.
Laymen say silly stuff like this all the time, and it just isn't true. Heavier than air flight did not violate the known laws of physics.
No serious scientist ridiculed the idea of landing men on the moon; the basic science of that feat was mundane -- even trivial -- it was a fantastic engineering challenge and accomplishment, but it did not in any way tax our basic understanding of physical law. We knew all the physics of it that we needed to know when Newton was still alive.
You live in an age of technological marvels and breakthroughs.
True. And despite that, in 107 years, no experiment has fundamentally challenged the truth of Lorentz invariance. None. All of our experiments have confirmed this to a fare-thee-well.
Things are yet to be invented that seem like pure science fiction to you today.
Maybe, but they will not violate the Theory of Relativity, and they will not make effects appear with their causes in the future.
It's only my opinion, but I think listening and transmitting are a waste of time.
First off, I don't believe our civilization has the technology to receive or broadcast on the kinds of frequencies that interstellar travelers would use.
Secondly, what fool would intentionally broadcast their coordinates when they don't know who's listening? Only a pointy headed liberal wouldn't stop to think that maybe - just maybe, an advanced predator race might pick up their broadcast.
Thanks for the slap down, but I think rigid thinkers such as yourself are going to be proven wrong in decades to come. Such has always been the case with those who refuse to dream big.
Superliminal velocities do not involve time dilation, which is a difference between an observer's proper time and the time he measures for another observer either in a gravitational field or in relative motion to his frame of reference. Both frames of reference are inside the light cone.
Time dilation only occurs as objects approach the speed of light from below. It does not apply to hypothetical superluminal objects. These objects are "spacelike" and outside of the light cone. When they (hypothetically) decelerate to speeds actually allowed in our universe they would arrive before they left.
Don't doubt me. I've taught university physics courses in relativity.
Wikipedia's discussion is actually accurate and accessible to laymen: http://en.wikipedia.org/wiki/Light_cone
If I had that solved, I'd already be setting the pricing schedule for trips to Alpha Centauri.
Physicists are only just now exploring the theory and working out what it would take to make it a reality. Others will come after them and build upon their work.
I hate to differ, but that's not even close to being true.
Life is found in practically every place we've looked on this planet, including in boiling sulfur springs, and even within solid ice. Even rocks in the most barren places on our planet, have been found to contain microbial life.
Scientists refer to these lifeforms as 'extremeophiles'. Some environments on moons of other planets are even less inhospitable to life, as some on Earth that currently have life within them.
The speed of light is not an engineering limitation, like the speed of sound is. The speed of light is actually two things: 1) the speed at which massless particles in the absence of external matter and fields travel and 2) a constant defining the interrelationship between time and space.
Mathematically, because of (2) the speed of light appears the same to all observers no matter how quickly or slowly they themselves are moving with respect to the source of light.
The geometric way of looking at this is as follows: We believe that we are free to move in all three dimensions of space at any speed we desire. However, the truth is that the dimensions of space and time are actually connected, and for particles which have mass, it is impossible to move through space without also moving through time. In fact, because of (2) we are actually confined to a much smaller subset of space-time. Space and time are potentially "infinite" but some regions of space-time are not actually accessible to us. They lie outside of what is called our "light cone." Objects traveling faster than the speed of light would actually be moving through this geometrically inaccessible region.
When people talk about tesseracts, Einstein-Rosen bridges, and "warp-drives" they are talking about mathematically possibilities, which -- if they existed physically -- would also imply time travel. If you moved outside of the light cone of our thread of history, to travel faster than the speed of light, you would necessarily intersect the light cones of different eras of the universe as you moved. When you stopped, you would no longer be in our light cone, but in another one. Time travel.
Prove me wrong. I did say by objective measure. The only two I know of would be a mass ratio or a volume ratio. I figured that the mass ratio is less than one part per billion.
Life is found in practically every place we've looked on this planet, including in boiling sulfur springs, and even within solid ice. Even rocks in the most barren places on our planet, have been found to contain microbial life.
Sure, but most of the Earth is inanimate by a wide margin.
> I have another hypothesis to toss out there:
Maybe when a species advances to a certain point, its advances lead to its destruction.
Entirely possible. Look at the current situation. We may end up killing ourselves off within the next few years at this rate...
It actually does. Even millions of ships would have to cover around 3-4 * 10^13 (c-yr)^3 to blanket our galaxy. Our civilization detectable neighborhood is ~1 (c-yr)^3. It would be highly impractical to make a stop on what is beginning to look like ~10^12 planets.
Correct.
It’s not a slap-down. You are mistaken about the nature of the problem in a fundamental way, and I used what was mildly rude language to get your attention. We don’t live in Cartesian space. We live in Minkowski space. Dreaming Big won’t get us out of that.
Sure you did. Thanks for the non apology.
OK, I apologize. You’re still wrong.
Well, go out and objectively examine the world we live in. Most of it is full of life. Even in places that challenge our fundamental understanding of what constitutes a habitable zone. It's ubiquitous.
Yes, until someone proves that I'm right. It'll happen.
“First off, I don’t believe our civilization has the technology to receive or broadcast on the kinds of frequencies that interstellar travelers would use.”
It depends on how long their projects could be sustained, I suppose. A race that has a natural lifespan of 100,000 years or have beaten geriatric death would plan for the long-haul, they could think pointing a message at potential aliens that takes 50,000 years to get where they are is a good bet. As far as detection ability for decreasing signal, who knows how sensitive such instruments could become.
“Secondly, what fool would intentionally broadcast their coordinates when they don’t know who’s listening?”
That’s what I think too. The first radio broadcast was 100+ years ago, of course we actually pointed a message at specific things in the case with METI, to my understanding.
Freegards
Off the coast of Western India there are cities in ruin which predate the last Ice Age.
Just off Okinawa are megalithic structures which also predate the last Ice Age.
There are cut or poured stones in South America Mountains at ruins of megalithic structures fitted perfectly together.
And of course there is the enigma of the Sphinx, a statue fashioned probably thousands of years before having the head re-carved by a local Pharaoh.
The Bible indicates that humankind was here before God made Adam and Eve. The distinction of Adam and his descendants from the other humankind is the presence of the spirit in the soul. It is very possible that intelligent beings inhabit other solar systems but lack what God breathed into Adam, a spirit.
A planet with active geology can pretty well obliterate the accouterments of technologies given time and tectonics and weather.
There is strong indication that advanced civilization arose on Mars or migrated to Mars in the distant past, but was devastated by a planetary explosion nearby, flooding Mars with such a massive amount of water that literally one half of the planet has been scoured of impact craters and the axis of the poles shifted dramatically.
What speculations such as these Scientists are making always fail to include are the threads of ruins scattered around our solar system. And of course, NASA never lands a mission close to anything that might tip the applecart.
Care to make it interesting?
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