As the only criticism on this article has been downvoted strongly, I feel compelled to repeat my explanation of that criticism (that believing in the multiverse is like believing in heaven or hell) at a higher level, in the hopes that people will be somewhat more critical of what esteemed scientists are peddling as truth:
There is not a shred of experimental evidence for the multiverse. In fact, experimental evidence is not even possible. That places it firmly in the pantheon of metaphysics.
That there is a multiverse could be an unescapable conclusion from an otherwise very successful theory, with many experimental verifications, but that isn't the case. The article neglects to mention that there are many alternative interpretations and theories that can equally well explain 'how it all started' and still result in inflation and all associated 'best' theories for the experimental observations of the universe. This article is all unwarranted extrapolation (back to the beginning of time and before).
The main pillar of the success of the multiverse theory is that it successfully appeals to the imagination. The main reason that it is being promoted is because the great physicists promoting the idea do not realize they are not as great philosophers as they are physicists.
Assertions that take the form "X is like religion" are not enlightening. When it is prefaced with "get the facts straight" then of course it's going to get downvoted. There is nothing being "peddled" here, there is no hidden agenda by "esteemed scientists".
We have experimentally demonstrated that the universe is a really, really weird place. Time and space can bend. Whoah. But hey, we proved that beyond a shadow of a doubt. Then there's quantum mechanics. Wave functions! Entanglement! Turns out the universe really works that way. Then the universe starts looking really non-deterministic. Then we figured out that the simplest interpretation of QM implies Many Worlds, that the universe splits and splits and splits into a bazillion near-copies. The quantum events just look non-deterministic from our perspective. Do we know everything? Hell no. But we know that QM is true and that it uses some form of Many Worlds. We know that the world is deterministic. We don't know for sure how the universe came into being (but we are sure the universe is expanding). We don't know if there really is such a thing as the multiverse, but as we figure out more about the big bang, about background radiation, about black holes and dark matter and the shape of our universe there's a good chance we'll figure it all out eventually.
Physics is treading on the domain of philosophy because we're getting better at physics. Philosophers debated since the dawn of time about free will and didn't get anywhere. Now we know that non-reductionist or dualistic world views make little sense. Philosophers debated for ages about morality. Now neuroscience is starting to deliver concrete answers. Philosophers debated for ages about religion and heaven/hell. And elementary Bayesian math shows the questions are just nonsensical.
Philosophy is about reasoning about topics we don't really understand. As our understanding of physics, math, neuroscience and biology grows philosophy has to make way.
The author responds to this point in one of the comments; I quote:
this is -- and I make no pretensions otherwise -- theoretical physics. It's not airy-fairy pie-in-the-sky speculation, but it also isn't proven the way you would prove that a * b = b * a. You may want to read this recent guest essay (http://scienceblogs.com/startswithabang/2011/10/guest_essay_...) that does a wonderful job of explaining, with some brilliant metaphors, what this sort of theory is (and isn't).
Isn't this like having a function that explains very well data that is within an observable range, and then stating with confidence that that function also applies to data in a range that is unobservable to you?
Yes, that function may hold outside your observable space, but it may not. We can't simply state as fact the predictions that come from assuming that this function applies outside our observable space.
Spot on, and even much of what is 'observable' here is not even close to understood. Inflation and dark energy/matter are both concepts that have been built to explain observation but which are themselves not yet explained at least not with much consensus.
How can the universe get "colder"? Does it just mean that the average energy-per-square-meter (or whatever unit) is less? If so, wouldn't that mean that saying "less dense" and "colder" mean basically the same thing at that scale?
Maybe I'm asking something stupid and obvious, but I keep thinking that energy can't be destroyed, ergo, there's exactly as much energy (and thus heat?) as before. Or is heat energy density? But doesn't that make "less dense and colder" a redundant statement, since they'd be the same thing?
Less dense implies colder, as the volume is not constant, but expanding. Temperature and density are different things though - one is how much energy something has, the other is how far away from other things it is. Related, but different.
With respect to destroying energy - energy converted into matter is 'colder'. There's not the exact same amount of energy - it's not that it can't be destroyed, it must be conserved with matter (E=MC^2). Great example - kinetic energy is used in a particle accelerator to create new particles, and it takes a ton of energy to make even a tiny bit of mass, so the average temperature would go down as more mass is created (heat being the transfer of energy - once it's trapped in a particle, it's not transferred as freely).
Yes, heat is energy density which is why pressure is basically the same thing as heat. That's why a pressure cooker can generate incredible pressure just by heating it. Similarly, your refrigerator cools things by expanding a liquid into a gas (state change is actually the dominant mechanism in a refrigerator but it would work in principle with out the state change)
Fascinating article, but I'd still like to know more about that 8th figure on the inflation model. We are told that the y-axis represents energy, but what is the x-axis? It clearly isn't time because it's being measured in phi over something measured in GeV.
This kind of science has always been hard for me to integrate. Thinking as a Bayesian, these arguments seem to be meant to influence my "prior" over possible initial states or natures of the universe. I'm not accustomed to that.
I'm used to science presenting me with evidence meant to influence my "posterior". I can handle that.
Are you aware that's irrational? Your assumptions about priors contain plenty of mistakes (all ideas do, mine too) and you should find a way of thinking which better allows for correcting those mistakes.
You're not meant to retain your prior forever. When you update, you replace it. Think of it as a FOR loop over incoming evidence. On each iteration, you increment or decrement the probability of the proposition in proportion with the evidence.
Consider what the alternative would look like. You retain both your original prior and every piece of evidence you've ever seen, then recompute all of it each time you need the current value? No. That doesn't pass the intuition test either. What you now think of as your prior on the Universe is not actually the belief you held at birth. You've updated dozens or hundreds of times during childhood, and each time you discarded your old "prior".
Sometimes I think I was born too soon. To think the new knowledge we well discover with in the next 100, 200, 1000 years is really exciting.
I wouldn't be surprised if in the next 20-50 years with all the genetic engineer going on one could live for ever. Of cause as long as you can afford it.
Sometimes I agree with you, but on the other hand, you have to recognize how lucky you are. There is no guarantee that the future will be better than the present, and there are many plausible risks that it could be much worse. For example, highly disruptive consequences of climate change; nuclear war; massively destructive accidents (like the gray goo scenario); and so on.
Whenever I find myself getting wistful about the future portrayed in science fiction, I remind myself that I am better off than all the humans before me since the dawn of our species, and also better off than the vast majority of humans on the planet right now. Future generations may look back at this as a golden age. So enjoy it!
I envision a world where, due to technology and science, everyone stops aging after 25.
A clock will be constantly visible on your forearm and time will be the only commodity in the world, in which you'll get paid and make payments in.
After the age of 25, you'll get 1 to 75 years of "time" deposited in your account. The clock on your arm will decrement by default as time passes, and increase/decrease as you earn/spend.
When your time expires (the clock reaches zero), you die.
Most people will live day-to-day, only having 24 hours of time in any given moment. Others will have millions of years on their clocks.
I cannot recommend the writings of Max Tegmark on the multiverse enough. Among people doing science at the heights of their fields, he is perhaps a uniquely talented popular writer. He even keeps it readable on his scientific papers, which read mostly just like his popular papers except shorter and with more math.
I agree -- if you're interested in MWI then you should read Deutsch (in fact, you should read Deutsch anyway) -- but the OP isn't about MWI, it's about a different sort of multiverse, with lots of "pocket universes" even on a single Everett branch because of inflation. Many of the implications are pretty similar, though.
hah, its like a variable in a function making theories about what the whole program is all about, and that there might be many other functions similar to it. :D
[+] [-] Confusion|14 years ago|reply
There is not a shred of experimental evidence for the multiverse. In fact, experimental evidence is not even possible. That places it firmly in the pantheon of metaphysics.
That there is a multiverse could be an unescapable conclusion from an otherwise very successful theory, with many experimental verifications, but that isn't the case. The article neglects to mention that there are many alternative interpretations and theories that can equally well explain 'how it all started' and still result in inflation and all associated 'best' theories for the experimental observations of the universe. This article is all unwarranted extrapolation (back to the beginning of time and before).
The main pillar of the success of the multiverse theory is that it successfully appeals to the imagination. The main reason that it is being promoted is because the great physicists promoting the idea do not realize they are not as great philosophers as they are physicists.
[+] [-] gizmo|14 years ago|reply
We have experimentally demonstrated that the universe is a really, really weird place. Time and space can bend. Whoah. But hey, we proved that beyond a shadow of a doubt. Then there's quantum mechanics. Wave functions! Entanglement! Turns out the universe really works that way. Then the universe starts looking really non-deterministic. Then we figured out that the simplest interpretation of QM implies Many Worlds, that the universe splits and splits and splits into a bazillion near-copies. The quantum events just look non-deterministic from our perspective. Do we know everything? Hell no. But we know that QM is true and that it uses some form of Many Worlds. We know that the world is deterministic. We don't know for sure how the universe came into being (but we are sure the universe is expanding). We don't know if there really is such a thing as the multiverse, but as we figure out more about the big bang, about background radiation, about black holes and dark matter and the shape of our universe there's a good chance we'll figure it all out eventually.
Physics is treading on the domain of philosophy because we're getting better at physics. Philosophers debated since the dawn of time about free will and didn't get anywhere. Now we know that non-reductionist or dualistic world views make little sense. Philosophers debated for ages about morality. Now neuroscience is starting to deliver concrete answers. Philosophers debated for ages about religion and heaven/hell. And elementary Bayesian math shows the questions are just nonsensical.
Philosophy is about reasoning about topics we don't really understand. As our understanding of physics, math, neuroscience and biology grows philosophy has to make way.
[+] [-] Umofomia|14 years ago|reply
this is -- and I make no pretensions otherwise -- theoretical physics. It's not airy-fairy pie-in-the-sky speculation, but it also isn't proven the way you would prove that a * b = b * a. You may want to read this recent guest essay (http://scienceblogs.com/startswithabang/2011/10/guest_essay_...) that does a wonderful job of explaining, with some brilliant metaphors, what this sort of theory is (and isn't).
[+] [-] guscost|14 years ago|reply
[+] [-] sendos|14 years ago|reply
Yes, that function may hold outside your observable space, but it may not. We can't simply state as fact the predictions that come from assuming that this function applies outside our observable space.
[+] [-] redwood|14 years ago|reply
[+] [-] lionhearted|14 years ago|reply
How can the universe get "colder"? Does it just mean that the average energy-per-square-meter (or whatever unit) is less? If so, wouldn't that mean that saying "less dense" and "colder" mean basically the same thing at that scale?
Maybe I'm asking something stupid and obvious, but I keep thinking that energy can't be destroyed, ergo, there's exactly as much energy (and thus heat?) as before. Or is heat energy density? But doesn't that make "less dense and colder" a redundant statement, since they'd be the same thing?
[+] [-] count|14 years ago|reply
With respect to destroying energy - energy converted into matter is 'colder'. There's not the exact same amount of energy - it's not that it can't be destroyed, it must be conserved with matter (E=MC^2). Great example - kinetic energy is used in a particle accelerator to create new particles, and it takes a ton of energy to make even a tiny bit of mass, so the average temperature would go down as more mass is created (heat being the transfer of energy - once it's trapped in a particle, it's not transferred as freely).
(Caveat - I'm not a cosmologist...)
[+] [-] fleitz|14 years ago|reply
[+] [-] thret|14 years ago|reply
[+] [-] acak|14 years ago|reply
http://www.ted.com/talks/george_smoot_on_the_design_of_the_u...
[+] [-] TheBurningOr|14 years ago|reply
[+] [-] fl3tch|14 years ago|reply
http://ned.ipac.caltech.edu/level5/Narlikar/Narlikar3_2.html
which has a lot more information. Phi is defined as the Higgs scalar field.
[+] [-] anakanemison|14 years ago|reply
I'm used to science presenting me with evidence meant to influence my "posterior". I can handle that.
[+] [-] xenophanes|14 years ago|reply
[+] [-] zmj|14 years ago|reply
Consider what the alternative would look like. You retain both your original prior and every piece of evidence you've ever seen, then recompute all of it each time you need the current value? No. That doesn't pass the intuition test either. What you now think of as your prior on the Universe is not actually the belief you held at birth. You've updated dozens or hundreds of times during childhood, and each time you discarded your old "prior".
Footnote: you do retain some of your recent evidence, for smoothing purposes. For more information, investigate how Bayesian networks incorporate time: http://en.wikipedia.org/wiki/Dynamic_Bayesian_network
[+] [-] knodi|14 years ago|reply
I wouldn't be surprised if in the next 20-50 years with all the genetic engineer going on one could live for ever. Of cause as long as you can afford it.
[+] [-] adriand|14 years ago|reply
Whenever I find myself getting wistful about the future portrayed in science fiction, I remind myself that I am better off than all the humans before me since the dawn of our species, and also better off than the vast majority of humans on the planet right now. Future generations may look back at this as a golden age. So enjoy it!
Edit: this inspired me to write an article:
http://news.ycombinator.com/item?id=3172469
[+] [-] kingkawn|14 years ago|reply
[+] [-] powertower|14 years ago|reply
A clock will be constantly visible on your forearm and time will be the only commodity in the world, in which you'll get paid and make payments in.
After the age of 25, you'll get 1 to 75 years of "time" deposited in your account. The clock on your arm will decrement by default as time passes, and increase/decrease as you earn/spend.
When your time expires (the clock reaches zero), you die.
Most people will live day-to-day, only having 24 hours of time in any given moment. Others will have millions of years on their clocks.
[+] [-] rms|14 years ago|reply
http://arxiv.org/PS_cache/arxiv/pdf/0905/0905.1283v1.pdf is his overview of the levels of multiverses.
If that properly blows your mind, see Bostrom's Infinite Ethics. http://www.nickbostrom.com/ethics/infinite.pdf
[+] [-] xenophanes|14 years ago|reply
http://beginningofinfinity.com/
[+] [-] gjm11|14 years ago|reply
[+] [-] unknown|14 years ago|reply
[deleted]
[+] [-] trocker|14 years ago|reply
take a look at this one too - http://en.wikipedia.org/wiki/Many-worlds_interpretation
[+] [-] powertower|14 years ago|reply
They take something that's perfectly explainable with a probability wave, and turn it into fantasy.
http://en.wikipedia.org/wiki/Wave_packet
[+] [-] jaequery|14 years ago|reply
[+] [-] borism|14 years ago|reply
Have you read the article?