Parallel Universes

Scientific American ^ | May 2003 | Max Tegmark

[Junior]

Is there a copy of you reading this article? A person who is not you but who lives on a planet called Earth, with misty mountains, fertile fields and sprawling cities, in a solar system with eight other planets? The life of this person has been identical to yours in every respect. But perhaps he or she now decides to put down this article without finishing it, while you read on. The idea of such an alter ego seems strange and implausible, but it looks as if we will just have to live with it, because it is supported by astronomical observations. The simplest and most popular cosmological model today predicts that you have a twin in a galaxy about 10 to the 1028 meters from here. This distance is so large that it is beyond astronomical, but that does not make your doppelgänger any less real. The estimate is derived from elementary probability and does not even assume speculative modern physics, merely that space is infinite (or at least sufficiently large) in size and almost uniformly filled with matter, as observations indicate. In infinite space, even the most unlikely events must take place somewhere. There are infinitely many other inhabited planets, including not just one but infinitely many that have people with the same appearance, name and memories as you, who play out every possible permutation of your life choices. Entire Article

Overview / Multiverses

• One of the many implications of recent cosmological observations is that the concept of parallel universes is no mere metaphor. Space appears to be infinite in size. If so, then somewhere out there, everything that is possible becomes real, no matter how improbable it is. Beyond the range of our telescopes are other regions of space that are identical to ours. Those regions are a type of parallel universe. Scientists can even calculate how distant these universes are, on average.

• And that is fairly solid physics. When cosmologists consider theories that are less well established, they conclude that other universes can have entirely different properties and laws of physics. The presence of those universes would explain various strange aspects of our own. It could even answer fundamental questions about the nature of time and the comprehensibility of the physical world.

[Arthur Wildfire! March]

"You didn't directly address my main argument (that finite plus finite is still finite)..." Now quit being conservative. That kind of talk is hyper-rational and overly sensitive to ultra-truthisms. You are supressing the free spirit of expression and thought. Think like a liberal. Space is finite, which is why we must prune the surplus population and save our fragile planet from any more technology. Quit thinking as though infinity is unlimited, and quit thinking that the historic blunderings of liberals mean anything. Truth is Left. There is only infinity in that direction, which is also limited. To the right, there is a wall of elephants thumping Bibles and weilding assault rifles.

[longshadow]

lost thread hyper-placemarker

[Arthur Wildfire! March]

Moorecock, I read him for research purposes. What a sick mind he had. Oh, he was imaginative, all right. And his writing was quick-paced. But evil.

[Lazamataz]

I don't like the idea of parallel universes. I can't even parallel park.

Let's Freep 'em!

[Arthur Wildfire! March]

"In infinite space, even the most unlikely events must take place somewhere."

I almost agree, although everything must be limited in both space, time, and influence. Otherwise, they would make other things impossible to exhist. How limited? I have no idea. Limited in uniqueness? Nope. And that means, there are lookalikes and actalikes. There's no getting away from it. This ball of stars, the multi-galactic 'universe' isn't the only thing out there. That would be impossible. And as for Heavan and Hell, they are in another plane of exhistence, which opens up another realm of possibility.

[Arthur Wildfire! March]

ROFL!

[Arthur Wildfire! March]

"If I say "infinite volume", I'm referring to the area of the balloon, not the area of the circle."

Infinite volume? Kind of like Hellery's mouth, a pandora's box of infinite and terrifying impossibilities.

[Arthur Wildfire! March]

Not to mention, an 'infinite balloon' would have to be one big sucker. No one would never see the wall, because infinity can never be walled in.

[Arthur Wildfire! March]

"...No one would never..." [Smacking self, walking off muttering...]

[Arthur Wildfire! March]

"...Nature has already done almost all of the winnowing out of that ensemble of 210^118 possibilities. All of the absurd ones are gone, so you don't have to "reach past" them."

Hm.... If only I could reach past them. But I'm too busy laughing.

[Physicist]

How can infinity have a radius?

A radius can be infinite. It's simple mathematics.

Let's suppose you're driving in your car. The road bends from side to side. Sometime the road curves gently, sometimes it curves sharply. At each point, you can describe that curvature by a radius: if you are driving around a circle, and are turning just as sharply as you are now, what is the radius of that circle? Sharp curves will have a small radius; gentle curves will have a big radius.

Then you get to a place where the road is perfectly straight. There's no curvature at all! What is the radius of curvature then? Why, it's infinite. (Although in practice, a "straight" road that is long enough won't have a radius of curvature much greater than 4000 miles--the radius of the Earth!)

The overall geometry of our universe is flat. That means that for a long, straight journey, the radius of curvature for your path will be infinity, just like it will be for a straight road or a flat table top.

[Physicist]

No one would never see the wall, because infinity can never be walled in.

You don't get it. There are no walls. The balloon example was a two dimensional analogue, with the 2-dimensional surface area of the balloon playing the role of the volume of our universe. Our universe expands continually in three dimensions just as the surface of an inflating balloon expands continually in two dimensions. Furthermore, while the surface of the balloon is curved, our universe is flat.

It's a tricky concept, I know.

[tang-soo]

In infinite space, even the most unlikely events must take place somewhere.

Sounds like Vaphod Beeblebrox and the improbability drive.

[Centurion2000]

Now, how do we find the universe where the US Constitution was never shredded up by big government and how can we get there ?

[Arthur Wildfire! March]

On a serious note, the idea of nature winnowing out vast possibilities of similar intelligent life forms in this particular ball of galaxies might be correct. How different can environmental conditions be, however?

Entire ecosystems are found where there is no sunlight, for example. We cannot even begin to explore high g-force planets, and what kind of life could evolve in them. What form could intelligent life be? Obviously, it could withstand whatever our toughest machines can withstand. This might sound grotesque, but so long as a computer chip can withstand the harshness, so could a brain that we would have difficulty comprehending.

It would be koolness incarnate if we are truly the most intelligent mortal beings in this ball of galaxies. But then there is the "Great Beyond". We will never have the technology to see the end of infinity. And could other beings travel accross incalculable distances at a speed revealing that light is merely the residue of something much faster?

Or perhaps through something more advanced than deep-freeze, 'kryogenics [sic?]', they travel more slowly, but relentlessly across great voids. Then again, a vast void between two multi-galactic orbs would have absolutely no friction, nor would there be much gravitational pull to alter their course. What it's like to travel them, we have yet to learn. Or perhaps there are forms of 'virtual travel' we have yet to comprehend.

Conclusion: Intellectually speaking, we are yet merely babes in the woods. Perhaps we always will be.

I could easilly conceived of advanced life from a doomed world beyond our particular ball of galaxies sending out droids to help other races prosper.

Well, enough of reality. I think I'll turn to some fiction now. =]

[No hard feelings? I was just having fun.]

FReegards....

[Arthur Wildfire! March]

Hm... a straight line is a straight line, it is not a curve. A radius forms a circle. And a circle must be finite, because once it closes, you can calculate a finite diameter, etc. Sorry if I'm wrong about that. I'm really not a math major. But I did have one brilliant math teacher who taught me about infinity and blew my mind.

[Arthur Wildfire! March]

"Our universe expands continually in three dimensions just as the surface of an inflating balloon expands continually in two dimensions. Furthermore, while the surface of the balloon is curved, our universe is flat."

Ah, so in other words, the universe is hollow? And the galaxies are disk shaped to form the membrane? Interesting.

At the same time, we are thinking on two different levels.

I'm saying that space is unlimited, that our collection of galaxies, [whether it's shaped like a ball or like a disk not being the point], is only a finite part of the big picture of infinite space.

In unlimited space, it is impossible to make an infinitely large curve or circle. An infinite zigzagging path? Maybe.

Thinking beyond the stars is thinking beyond physics. And that is sheer chaos. So while I was joking around, I do undestand our trouble communicating.

[MissAmericanPie]

I hope my twin stays on her diet.

[Physicist]

Ah, so in other words, the universe is hollow? And the galaxies are disk shaped to form the membrane? Interesting.

No, the universe is uniformly filled with matter and expands in all directions. You have to scale the balloon example up by a dimension.

[wordsofearnest]

Perhaps you are the doppelganger.