Parallel Universes

davej

Decent enough article, good references at the bottom of each page..

http://www.sciam.com/article.cfm?articleID=000F1EDD-B48A-1E90-8EA5809EC5880000&pageNumber=1&catID=2

davej

PHB

I remember someone telling me this, can't rememe who.

The theory is that every particle has an anti particle.
Applying this to the theory of the big bang, since we have a universe, we must also have an anti-universe

Zukustious

Every particles anti-particle exists in this universe. There is anti-matter here just not much of it.

SOL

Well if there is an infinite amount of universes to happen then there is an infinitely large chance that one of them will have destroyed our universe so I don't believe you :P

Zukustious

Originally posted by SOL
Well if there is an infinite amount of universes to happen then there is an infinitely large chance that one of them will have destroyed our universe so I don't believe you :P

Buh??? Since when was it declared that universes destroy other universes? What the Hell are you talking about?

Thomas from Presence

Where's Liebeniz when you need him?!

bonkey

Originally posted by Zukustious
Buh??? Since when was it declared that universes destroy other universes? What the Hell are you talking about?

He's just trolling with his pseudo-maths again.

jc

Bob the Unlucky Octopus

Not necessarily PHB. Just as every particle has an anti-particle, matter is balanced by dark matter.

"Dark matter" is a theoretical entity, but we know it's there because its effects are measureable. Looking at it that way, it does not necessarily follow that for every universe there is an "anti-universe". Simply because, while a particle can be defined by its characteristics, charge, spin, mu-constant and such- the universe is simply a paradigm.

Take this example- Newton's 3rd law of motion. Simply because for every force there is an equal and opposite force- does it necessarily follow that there is an "anti-force" that destroys any force exerted? Clearly not, that would create a paradox in which no forces could exist. A "force" means nothing if not defined- by itself the term means nothing. Whereas if I said "electron"- then I am talking about a highly specific charged particle with a particular weight, negative charge, etc, etc.

There has indeed been theoretical speculation about multiverses, but it has been based on a single, unproveable premise- ie, that the universe is of infinite size. This is presumptive knowledge. By beginning with a faulty premise, I could indeed prove (mathematically) that black is white, 1+1 = 3 and that England can actually win at one of the damn sports they invented. Impossibilities all of them (alright, nearly all of them )- but you see my point. It's like reasoning upon the premise that a God exists. Since it's not observable or indeed proveable, nothing more can be reasoned from it scientifically. "Why does God let bad things happen to good people?"- assumes the existence of a God. If someone has faith that a shaky unproveable premise can indeed be reasoned upon, then they have exited the realm of science and entered that of philosophy.

Similarly "Is there another Bob the Unlucky Octopus agonizing over similar issues 10^(10^28) + 1 meters away?" question- assumes that space is at least that big. Given that we can only see about 4 x 10^26 meters, it's enormously speculative to suggest either that space is infinite, or that it extends beyond this near-impossible range. The rate of expansion of the universe would indicate that it is enormously unlikely that it could be that large. Put it this way, you are as unlikely to find all the fat molecules in your buttocks to jump simultaneously 1 meter to the right (sorry ladies )

Speculation about the theoretical existence of ******* in the expansion of space, and pockets of the multiverse are on the whole meaningless if we can't even see halfway to where these pockets supposedly abide. Moreover, the lack of any mathematical support short of a probability test is misleading. In an infinitely large space (or a space approaching that value), almost *anything* is possible. That doesn't mean to say likely, or that it exists at all. Theoretical physics is full of issues like these, brain-teasers with no solution, trick questions missing a trick.

davej

There has indeed been theoretical speculation about multiverses, but it has been based on a single, unproveable premise- ie, that the universe is of infinite size. This is presumptive knowledge.

Yes you are right, but the article takes this point on board and acknowledges that the theory would be stuck in the realms of metaphysics if it weren't for the fact that it can make predictions, be experimentally tested and be falsified. The Level 1 case is a very generic prediction from well established physics and is in fact rather uncontroversial. Also studies of the microwave background provide evidence for flat infinite space.

Each universe is merely a small part of a larger "multiverse."
By this very definition of "universe," one might expect the notion of a multiverse to be forever in the domain of metaphysics. Yet the borderline between physics and metaphysics is defined by whether a theory is experimentally testable, not by whether it is weird or involves unobservable entities. The frontiers of physics have gradually expanded to incorporate ever more abstract (and once metaphysical) concepts such as a round Earth, invisible electromagnetic fields, time slowdown at high speeds, quantum superpositions, curved space, and black holes. Over the past several years the concept of a multiverse has joined this list. It is grounded in well-tested theories such as relativity and quantum mechanics, and it fulfills both of the basic criteria of an empirical science: it makes predictions, and it can be falsified. Scientists have discussed as many as four distinct types of parallel universes. The key question is not whether the multiverse exists but rather how many levels it has.


davej

Bob the Unlucky Octopus

With respect, I disagree with the author of the article on that particular point. Comparing a multiverse to the once-metaphysical question of the earth's being round is absurd. Numerous calculations dating back to Grecian times had long-established the observability of this. It is a measureable fact of perspective and geometry, that requires absolutely no presumptive knowledge.

With the multiverse on the other hand, you are dealing with a conundrum of presumption. If the universe is infinite in dimension, then the theory is a remote possibility, if not the theory is an impossibility. The question begs itself- even though the theory within itself rigorously submits to the scientific method, of what value is this when the very premise is presumed?

That's the point the article abjectly fails to address- comparisons with the spherical nature of the Earth are a feeble attempt to make the reader forget about the near non-existent premise. It addresses the issue of an infinite universe from a metaphysical perspective ("How can it *not* be infinite? It seems to make sense that it would be," etc).

If I took the ultimate metaphysical question, assumed the existence of God and then tried to reason within the scientific method around that premise...how seriously would I be taken? About as seriously as most people who aren't theoretical physicists would take the scientific value of the multiverse, I would hope. Yes the theory makes predictions, but those predictions are not based on observation. In other words, while special relativity was only proved on paper, the theory was of little value. When referred back to Michaelson-Morley and tested with highly accurate timing and measurement devices, the theory could then be refined.

Black holes, dark matter- these things can be measured through observation and identified. The multiverse is by definition something that requires an omniscient reference point to observe. Unless or until that is somehow achieved, the multiverse is little more than a string of probability theorems formed around a shaky premise. Scientific progress is ultimately derived through observation- when someone measures or observes a parallel universe then it will be worthy of genuine scientific discussion. Until then, the question is as meaningless as any metaphysical paradox.

davej

But according to current observations and theories the idea of a finite universe is much more problematic than an infinite one. It is generally agreed according to Einstein's theories and what we have observed about the density of matter/energy in the universe that it is expanding. A continually expanding universe precludes the possibility of a finite universe.
Also an eternal universe is impossible if it is finite (or even an infinitely bounded sphere) , this is can be proved with Newtonian physics. So for you to reject the assumption of an infinite universe means you must reject the theory of the continually expanding universe and accept that there will be a big crunch.

Eg: this from a standard cosmology faq (Prof. Wright)

http://www.astro.ucla.edu/~wright/infpoint.html

or here (Assoc Prof Ciardullo):

http://www.astro.psu.edu/users/rbc/a1/lec17.html

So from my point of view all of the evidence points towards an infinite universe, and most cosmologists today are making this very assumption. Of course we may yet be proven incorrect, but it has yet to be falsified and there is far less evidence for a finite one. While this does not necessarily prove in itself the existence of the multiverse it makes it possible. The fact that the theory of the multiverse can help explain some strange properties of our own universe, increases its likelyhood.

davej

comet

Bob you seem to be saying seeing is believing, you can't believe there is an infinte universe until it can be observed, you can't believe in paralel universe until they are observed and so they are not worthy of genuine scientific discussion. Ideas can lead to observable proof, these ideas need to be developed so that we can know what to look for. Perhaps this theory is like Einsteins Relatively waiting to be proved by observation.

Impurity

Black holes, dark matter- these things can be measured through observation and identified.

these things mights be measured but we are completely clueless as to what and why they are!

there are many theories about both dark matter and black holes, just cause we can see them, doesn't mean that we know what they do.

take for instance the most common theory about black holes, a rip in space, probably due to the collapse of a huge star (much bigger than our sun) that has a gravemetric field so strong, that even light itself can't escape. hence the name, black hole!

this theory came about because we can't see black holes, all we see is the absence of light! it could really be anything! but this is an intelligent theory. you say that the multiverse is just theory with no proof, but yet we have these black holes, we can see them, but we still don't know they exist! ironic, isn't it!

Capt'n Midnight

this theory came about because we can't see black holes

Bollocks (Not a rude word - cf. Richard Branson ) - they were around in theory long before anyone

Black holes came about because the speed of light is finite (cf. Maxwell) and the gravitational attraction of a body of weithg M can be calculated (Netwon) the size of a body depends on how compact it is and the point at which atoms break down to neutrons can be calculated - hence given the size and mass the escape velocity can be calculated further (Schwarzchild) .

At a certain mass the excape velocity exceeds the speed of light - hence the name BLACK Hole.

Actually in point of fact the random generation of particles and antiparticles for a short time (keeping the overalll energy level of free space low) means that if one of these pairs falls in to a black hole before it can aniliate its counter part - means the other is actually free to travel away from the hold (Hawking Radiation)

So Black holes are actually evaporating - and long after the last neutron has decayed (10^43 year half life ?) black holes will still be loosing mass.

And when the mass falls to a point where the escape velocity is less than that of the speed of light - KABOOOOOMMMMM.....

(rather a long way of saying they are not gateway to parallel Uni's)

PS. before you start worrying about the sun going nova in 4 billion years remember
a) the milky way will have collided with andronomeda by then
b) Oxygen is carcinogenic (hence the need for Vitamine E)

Impurity

well sheck mate to me ;-)

you obviously know far more about it than me, i am only a first year college physics student and we only beirfly touched on black holes!

i like your signature! ;-)

Capt'n Midnight

one of the many theories about the start of the universe proposed by those who wern't that at the time is that you don't need much energy to create a universe.

so get your favorite Brownian motion producer and even though it will have a low average amount of energy in it - there is the possiblilty that a fluctuation for a very short time so as not to increase or decrease the average overall amount of energy will create particles / antiparticles which will colide and hand back the energy they were created from - this can happen in free space too.

Now the good bit - in an infinite amount of time in an infinte space with just a smidgen of energy (now where did that come from) is enough to create a whole multituse of universes. none will be long lived from the perspective outside - but inside is a different thing - eventually one will last long enough (from the internal frame of reference) to support life capable of realising that it exists. am fairly sure there is not enough energy in the universe to step outside it and the time of its existance is too short to allow anyone from the outsdide to enter - not much point cos all the physical laws would be different..

i.e. our universe suits us cos if it did not then we would not exist ..

AFAIK infaltion theory does not put a limit on the universes size just how much of it we can see/communicate with - if two parts of the universe are expanding at c/2 in opposite direction then there is no way of seeing each other - but a point mid way in between would be able so see both of them (but only as they were in the far distant past )

there is a different theory that says when you time travel you LEAVE this time line and enter another so it is not your grandfather you kill and so it is only your equlivant who gets killed in a second universe - not you - problem is you can't go back if this theroy is true.

Now since at the last count we are living in an expanding universe this kinda screws up the big-crunch theories.

BTW: expansion can't be measured locally it only is visible over vast distances (bigger than galactic)

Capt'n Midnight

If you can prove something it is not a theory by definition.

Theories can only be disproven (and since many theories are based on others you can end up with a house of cards where by disproving one you end up with a complete mess)

Theories should explain all observed facts and make predictions which can be checked. Otherwise it's just observation or opinion.

No one is ever asked to take a theroy as truth - because it can never be - again by definition.

If you disagree with a theory then suggest a better one, if it explains more or is more robust then it too may be accepted until a better one comes along.




PS. Bob - you should try to get your hands on a finite probability generator - among it's many uses are getting molecules to move to the left. (usually cotton/nylon rather than gylcerides)

pro_gnostic_8

Hi. May I ask a question, please, of a cosmological nature indirectly related to this thread............ something that has intrigued me for a long time now.

At the time of the "Big Bang", did that pea-sized object without dimensions (the singularity) that contained all the mass and matter of the future universe expand into an empty void that was already there? In other words, was there a universe-sized vacuum of nothingness around it? Or did the singularity as it pulsed into expansion in the first nano-second of the Big Bang also create space (and time)?

I hope the above question makes sense. Thank you in advance for any light you can shed on this for me.

davej

Our universe was always "infinite" in size even at the big bang.
But you have to stop thinking of it as a balloon that got blown up.

Check the first link of my previous post for an explanation.
Also see here:

http://www.wonderquest.com/SpacePinhead.htm

davej

pro_gnostic_8

Originally posted by davej
Our universe was always "infinite" in size even at the big bang.

Well. no, Dave............ not exactly. The link in your most recent post would suggest otherwise. That quote is " space was always infinite even at it's creation: the Big Bang"

This seems to insinuate that there was no space "around" the singularity for it to expand into! Or am I reading this completely wrong?

bonkey

Originally posted by Bob the Unlucky Octopus
Black holes, dark matter- these things can be measured through observation and identified.

Actually, thats not true.

Black holes - which everyone has latched onto from this post - are something which we believe we can identify.

Our theory of how the universe posits that they should be capable of existing, and that if they did, they would have certain properties, and interact with the rest of the universe in certain ways.

To date, we have found bodies which appear to exert these influences - or have these properties - and therefore have concluded that it would appear our theory is correct.

So, with as much certainty as we can claim to know anything about cosmological entities, we can say that black holes would appear to exist, and we understand them as well as we understand (say) neutron stars, pulsars, and other entities that we have identified through a combination of theory and observation.

Dark Matter, on the other hand, is exactly the opposite. It is matter which we cannot observe, which does not interact with anything we are aware of, and which basically is nothing but a theoretical construct. Indeed, anything observed - by definition - cannot be dark matter.

The only "evidence" for its existence is that we need to insert something into our existing models of the universe in order to balance what our models say should be happening with what our current theories say we are observing. By our calculations, the universe has < 10% of the mass it should have to be exerting the properties it appears to exert, at the age and size we think it is.

To counteract this, we have posited that there should be dark matter out there. Its the "only thing" that makes sense.

Even when we combine all of the mass we believe might be out there (such as with the relatively recent findings on neutrinos), allowing for the best case scenarios in our calculations, we are still worfully short on matter.

Dark matter, ultimately, is something science is taking on faith to fill a gap which it cannot explain.