APOD and General Astronomy Discussion Forum
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Astrogirl, this sounds like a school assignment. Is it? If so, you should seek out some of the literature on multiverses; check out this link, for example: https://arxiv.org/search/?query=multive ... rce=headerastrogirl808 wrote: ↑Tue Dec 03, 2019 7:51 am Hey guys, I'm a high school astronomy student in Hawai'i and was wondering if anyone had any opinions on the existence of multiverses? If so which of the existing theories on multiverses seems the most probable based on physics/science? Any answers would help out a lot thanks so much!
Markus, you might like some of the papers at the link I supplied, too!Markus Schwarz wrote: ↑Tue Dec 03, 2019 9:05 am 'Multiverses' maybe fun for science fiction, but they are not science! The main reason for that is that they are not testable (hence, they cannot be falsified): you cannot measure something which, by definition, is outside the observable universe.
Multiverses may or may not be testable but agnostic/atheist scientists like myself cherish them as our own "Just So Stories" that totally exclude "divine intervention" (or Schrödinger's cat "human intervention") in explaining the world we live in.astrogirl808 wrote: ↑Tue Dec 03, 2019 7:51 am
Hey guys, I'm a high school astronomy student in Hawai'i and was wondering if anyone had any opinions on the existence of multiverses? If so which of the existing theories on multiverses seems the most probable based on physics/science? Any answers would help out a lot thanks so much!
There's a lot of truth there, but I wouldn't say that these hypotheses aren't science. Some of them do offer tests (for instance, they predict certain structure in the CMB). And in general, even very speculative ideas from smart people can form the basis of science that gets developed out in the future. (String theory might be one such example.)Markus Schwarz wrote: ↑Tue Dec 03, 2019 9:05 am 'Multiverses' maybe fun for science fiction, but they are not science! The main reason for that is that they are not testable (hence, they cannot be falsified): you cannot measure something which, by definition, is outside the observable universe.
I did. The first paper is about multiversions in software development, the next two are from computer science. From the context of atrogirl808's question, I assumed she is interested in the cosmological multiverse (which papers 4 and 5 write about). For more details why I consider the multiverse arising from superstring theory as pseudo-science, see this FAQ by Dr. Peter Woit, who wrote a whole book on the subject.
I think we are talking about different things. I refer to the multiverse in superstring theory and the anthropic reasoning that goes with it.Chris Peterson wrote: ↑Tue Dec 03, 2019 1:56 pm Some of them do offer tests (for instance, they predict certain structure in the CMB).
Okay. But I take the question of multiverses to extend to a variety of hypotheses which have been offered, and some definitely offer potential tests.Markus Schwarz wrote: ↑Tue Dec 03, 2019 2:20 pmI think we are talking about different things. I refer to the multiverse in superstring theory and the anthropic reasoning that goes with it.Chris Peterson wrote: ↑Tue Dec 03, 2019 1:56 pm Some of them do offer tests (for instance, they predict certain structure in the CMB).
Chris Peterson wrote: ↑Tue Dec 03, 2019 2:29 pm
(I'm inclined to agree, however, that anything invoking the anthropic principle for scientific explanation might reasonably be called pseudoscience.)
https://en.wikipedia.org/wiki/Anthropic_principle wrote:
<<The anthropic principle is a philosophical consideration that observations of the universe must be compatible with the conscious and sapient life that observes it, and that there is hence a survivorship bias. A weak anthropic principle (WAP) similar to the one defined by Brandon Carter, states that the universe's ostensible fine tuning is the result of selection bias (specifically survivorship bias): i.e., only in a universe capable of eventually supporting life will there be living beings capable of observing and reflecting on the matter. Most often such arguments draw upon some notion of the multiverse for there to be a statistical population of universes to select from and from which selection bias (our observance of only this universe, compatible with our life) could occur.>>Click to play embedded YouTube video.
But that is exactly my point: the multiverse of string theory heavily relies on the anthropic principle. The short version is: Superstring theory only works in 10 dimensions. But we only observe 4 (three spatial and one temporal), so the other 6 need to be somehow 'compactified', i.e. made so small that we do not observe them. It turns out that there are roughly 10^500 ways to 'roll up' the 6 dimensions, and each of these leads to different values for the physical constants (speed of light, rest mass of the electron, etc.). As far as we know, there is no reason why one compactification is preferred to any of the others. This is where the anthropic principle comes into play: we just happen to be in the part of the multiverse with 'our' natural constants, because if we were in any of the others, we wouldn't be here to ask. End of story!neufer wrote: ↑Tue Dec 03, 2019 4:16 pmA weak anthropic principle (WAP) is excellent Darwinian science, IMO.Chris Peterson wrote: ↑Tue Dec 03, 2019 2:29 pm
(I'm inclined to agree, however, that anything invoking the anthropic principle for scientific explanation might reasonably be called pseudoscience.)
There is no one multiverse hypothesis. There are several, with fundamental differences. And, of course, there's really no "fine tuning" problem. It's not even an issue.BDanielMayfield wrote: ↑Tue Dec 03, 2019 6:48 pm Consider the origin of the Multiverse hypothesis. It is an idea without fundamental factual support that was put forward as an answer to the Fine Tuning "Problem". But if the one and only universe that we know to actually be in fact real was in fact "tuned" as it were, then the need for such an idea evaporates.
Yes, I know. I didn't say ALL of the papers... I said "some of the papers at the link I supplied."Markus Schwarz wrote: ↑Tue Dec 03, 2019 2:20 pmI did. The first paper is about multiversions in software development, the next two are from computer science.
Yes, I made the same assumption. I also assume a high school student is capable of looking at that list and picking out some of the relevant papers. It's nice that you have demonstrated that you are capable of doing so! I wasn't expecting that from you!!Markus Schwarz wrote: ↑Tue Dec 03, 2019 2:20 pmFrom the context of atrogirl808's question, I assumed she is interested in the cosmological multiverse (which papers 4 and 5 write about).
I don't need more details and in fact, find your comments not very helpful in this context, though admit you did answer the first part of the student's query as to whether anyone here had opinions about multiverses!Markus Schwarz wrote: ↑Tue Dec 03, 2019 2:20 pmFor more details why I consider the multiverse arising from superstring theory as pseudo-science, see this FAQ by Dr. Peter Woit, who wrote a whole book on the subject.
Perhaps the student and her teacher will be interested in your take on the matter. Since I suspect the second part of her query is the more important part, I tried to steer her to resources she can use for that.Markus Schwarz wrote: ↑Tue Dec 03, 2019 5:58 pm
One of the problems I have with this, is that it stops all kind of scientific endeavor. According to the above paradigm, asking fundamental questions like why the universe has the properties it has is pointless, because the answer is that the multiverse 'did it'. Furthermore, we cannot test superstring theory, so we cannot find out if it is the correct theory in the first place.
SAP over WAP).Chris Peterson wrote: ↑Tue Dec 03, 2019 1:56 pmThere's a lot of truth there, but I wouldn't say that these hypotheses aren't science. Some of them do offer tests (for instance, they predict certain structure in the CMB). And in general, even very speculative ideas from smart people can form the basis of science that gets developed out in the future. (String theory might be one such example.)Markus Schwarz wrote: ↑Tue Dec 03, 2019 9:05 am
'Multiverses' maybe fun for science fiction, but they are not science! The main reason for that is that they are not testable (hence, they cannot be falsified): you cannot measure something which, by definition, is outside the observable universe.
As theory, or even as hypothesis, most multiverse ideas remain scientifically weak, but to call them nonscientific is, perhaps, taking things a little too far.
Good eye, this is an assignment for my astronomy class where Astrogirl was given the direction to ask experts a question where either she could not find the answer to via Google or the answers were too complex or contradictory. She also asked a local astronomer and included his response in her final work as well as snippets from this conversation. Thanks to everyone who participated!owlice wrote: ↑Tue Dec 03, 2019 9:38 am
Astrogirl, this sounds like a school assignment. Is it? If so, you should seek out some of the literature on multiverses; check out this link, for example: https://arxiv.org/search/?query=multive ... rce=header
There's no way any telescope will ever be able to see anything that is outside of this universe.orin stepanek wrote: ↑Fri Jan 03, 2020 3:27 am This is just a muse; but how do you suppose the the Science community will react if James Webb sees well beyond the Big Bang?
And no optical telescope will ever see to the edge of the observable universe, because it was optically opaque for the first few hundred thousand years after the Big Bang. A gravitational wave telescope might be able to see to the very edge, however.BDanielMayfield wrote: ↑Fri Jan 03, 2020 12:23 pmThere's no way any telescope will ever be able to see anything that is outside of this universe.orin stepanek wrote: ↑Fri Jan 03, 2020 3:27 am This is just a muse; but how do you suppose the the Science community will react if James Webb sees well beyond the Big Bang? :mrgreen:
The fact that we can't directly observe either beyond the edge of the observable universe, or directly observe other universes (those are different things) does not imply that theories about them aren't falsifiable. Theories about both make predictions on how they affect the structure or character of the observable universe. Direct observations aren't required.That leads to one of the key objections to multiverse theories; untestablity. Since the existence of other universes cannot ever be supported by observational evidence, it requires a kind of leap of faith to believe in them.
https://physicsworld.com/a/new-evidence-for-cyclic-universe-claimed-by-roger-penrose-and-colleagues/ wrote:Click to play embedded YouTube video.
Physics World : Cosmology Research update 21 Aug 2018
New evidence for cyclic universe
claimed by Roger Penrose and colleagues
<<Unexpected hot spots in the cosmic microwave background (CMB) could have been produced by black holes evaporating before the Big Bang. So says a trio of scientists led by mathematical physicist Roger Penrose in a paper presenting new evidence that our universe is just one stage in a potentially infinite cycle of cosmic extinction and rebirth. Other researchers, however, remain sceptical that the microwave background really does contain signs from a previous “aeon”.
According to standard cosmology, the universe underwent a very brief but exceptionally intense expansion just after the Big Bang. This period of “inflation” would have ironed out any irregularities in the structure of the early universe, leading to the very uniform cosmos that we observe around us.
However, Penrose, based at the University of Oxford , has developed a rival theory known as “conformal cyclic cosmology“ (CCC) which posits that the universe became uniform before, rather than after, the Big Bang. The idea is that the universe cycles from one aeon to the next, each time starting out infinitely small and ultra-smooth before expanding and generating clumps of matter. That matter eventually gets sucked up by supermassive black holes, which over the very long term disappear by continuously emitting Hawking radiation. This process restores uniformity and sets the stage for the next Big Bang.
Penrose has... identified patches within the CMB that are much hotter than the surrounding region. The idea is that these hot spots could be due to the (mainly electromagnetic) radiation given off during the Hawking evaporation of supermassive black holes in the previous aeon.
Penrose says that although originally very feeble, those emissions would have been concentrated in our own aeon into spots with huge amounts of energy that he and his colleagues call Hawking points. That concentration comes about, he explains, because “the universe loses track of how big it is at the transition between aeons”. The Hawking points would then have stretched during the early universe, forming circular patches with a diameter on the sky about five times that of the Moon.
Penrose and two colleagues – Daniel An of the SUNY Maritime College in the US and Krzysztof Meissner at the University of Warsaw in Poland – report scouring CMB data from the European Space Agency’s Planck satellite for hot spots of various sizes and analysing how quickly the microwave temperature drops off around them compared to spots in 1000 simulated maps of the CMB. They found that in and around small spots, not a single simulated map had higher temperature gradients than the real cosmos – with the temperature variations in the latter case being about an order of magnitude higher (some 3×10-4 K) than the CMB average.
Some other physicists, however, remain unconvinced. James Zibin of the University of British Columbia in Canada points out that scientists have been scrutinising the CMB for years and have found no evidence for particularly hot spots (although they have identified one anomalous cold patch). He also reckons that Penrose and colleagues have failed to account for the “look elsewhere” effect, arguing that because they found the hottest spots in the real as opposed to simulated data in just 2 out of 40 tests (focusing on different sizes of spot and CMB border region each time) the chances of having been the victim of a statistical fluke drop from 1 in 1000 to as low as 1 in 50.>>
For believers direct observations of the Creator aren't required either. But calling on infinite infinities to explain existence is an infinite stretch, to put it simply.Chris Peterson wrote: ↑Fri Jan 03, 2020 2:30 pmAnd no optical telescope will ever see to the edge of the observable universe, because it was optically opaque for the first few hundred thousand years after the Big Bang. A gravitational wave telescope might be able to see to the very edge, however.BDanielMayfield wrote: ↑Fri Jan 03, 2020 12:23 pmThere's no way any telescope will ever be able to see anything that is outside of this universe.orin stepanek wrote: ↑Fri Jan 03, 2020 3:27 am This is just a muse; but how do you suppose the the Science community will react if James Webb sees well beyond the Big Bang?
The fact that we can't directly observe either beyond the edge of the observable universe, or directly observe other universes (those are different things) does not imply that theories about them aren't falsifiable. Theories about both make predictions on how they affect the structure or character of the observable universe. Direct observations aren't required.That leads to one of the key objections to multiverse theories; untestablity. Since the existence of other universes cannot ever be supported by observational evidence, it requires a kind of leap of faith to believe in them.
BDanielMayfield wrote: ↑Fri Jan 03, 2020 4:34 pm
For believers direct observations of the Creator aren't required either. But calling on infinite infinities to explain existence is an infinite stretch, to put it simply. So some multiverse theories may be falsifiable, that's good. A great number of religious theories have been and will continue to be falsified, which is also good. Long live the pursuit of truth. May ideas that deter finding the truth come to nothing.
https://en.wikipedia.org/wiki/God_of_the_gaps wrote:
<<"God of the gaps" is a theological perspective in which gaps in scientific knowledge are taken to be evidence or proof of God's existence. The "gaps" usage was made by Christian theologians not to discredit theism but rather to point out the fallacy of relying on teleological arguments for God's existence. Some use the phrase as a criticism of theology, to mean that the existence of a creator is almost always proposed for anything not currently explained by science.
From the 1880s, Friedrick Nietzsche's Thus Spoke Zarathustra, Part Two, "On Priests", said "... into every gap they put their delusion, their stopgap, which they called God."
The concept, although not the exact wording, goes back to Henry Drummond, a 19th-century evangelist lecturer, from his Lowell Lectures on The Ascent of Man. He chastises those Christians who point to the things that science can not yet explain—"gaps which they will fill up with God"—and urges them to embrace all nature as God's, as the work of "an immanent God, which is the God of Evolution, is infinitely grander than the occasional wonder-worker, who is the God of an old theology."
In 1933, Ernest Barnes, the Bishop of Birmingham, used the phrase in a discussion of general relativity's implication of a Big Bang:
Must we then postulate Divine intervention? Are we to bring in God to create the first current of Laplace's nebula or to let off the cosmic firework of Lemaître's imagination? I confess an unwillingness to bring God in this way upon the scene. The circumstances with thus seem to demand his presence are too remote and too obscure to afford me any true satisfaction. Men have thought to find God at the special creation of their own species, or active when mind or life first appeared on earth. They have made him God of the gaps in human knowledge. To me the God of the trigger is as little satisfying as the God of the gaps. It is because throughout the physical Universe I find thought and plan and power that behind it I see God as the creator.
During World War II the German theologian and martyr Dietrich Bonhoeffer expressed the concept in similar terms in letters he wrote while in a Nazi prison. Bonhoeffer wrote, for example:
how wrong it is to use God as a stop-gap for the incompleteness of our knowledge. If in fact the frontiers of knowledge are being pushed further and further back (and that is bound to be the case), then God is being pushed back with them, and is therefore continually in retreat. We are to find God in what we know, not in what we don't know.
Both many theologians and scientists believe that it is a logical fallacy to base belief in God on gaps in scientific knowledge. In this vein, Richard Dawkins, an atheist, dedicates a chapter of his book The God Delusion to criticism of the God-of-the-gaps fallacy. Other scientists holding religious beliefs, such as Francis Collins, reject a God-of-the-gaps while embracing the idea of a God who fine tuned the universe precisely so human life could exist.>>
You are using "theory" in two different ways here, using two different meanings of the word. So I don't think you're making any sort of valid comparison.BDanielMayfield wrote: ↑Fri Jan 03, 2020 4:34 pm So some multiverse theories may be falsifiable, that's good. A great number of religious theories have been and will continue to be falsified, which is also good.
