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Big Bounce Simulations Challenge the Big Bang

127 points by SirLJ 6y ago

runxel 6y ago
Both theories are somewhat incomprehensible for normal human beings. The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. We humans are inherently bad in dealing with these terms.
- Johnjonjoan 6y ago
  You're right of course but I find the cyclic version so much more intuitive. The force from the big bang was imparted in an instant yet gravity is a constant force. IANAP but surely at some point the accumulative force of billions/trillions/... of years of gravity overcomes the force imparted by the big bang and the universe compresses into a singularity again? I'd really appreciate someone explaining why this isn't obviously the case.
  - coldcode 6y ago
    I'm not sure we can ever tell the difference between the two models. Given the assumption that both produce a "boring" universe, and that models are never completely verifiable, it could be that either pathway appears the same to us at this point in time.
  - tyfon 6y ago
    The issue with this view is that in the universe we see today the gravitational force is not strong enough to do what you describe here. There is acceleration of the expansion i.e. energy is added to the system (in the form of vacuum energy possibly). To say it in another way, the energy used to expand the universe today is not only the initial force imparted by the big bang but is added to as part of quantum processes in empty space. However as the universe expands, the amount of matter (dark + luminous) does not increase so the proportion of gravity/matter to dark energy (the force that accelerates the expansion) is getting lower and we get an acceleration. These observations exclude the possibility of a "big crunch". Disclaimer: I am a statistician not a cosmologist but this is how I have understood it.
    - Johnjonjoan 6y ago
      Cheers, I now understand why it's not such a clear case. I fear I may have many more harder to answer questions now though - Thanks none the less!
      - GioM 6y ago
        Take the idea a little further, to the end of the universe, and the rate of acceleration of expansion of space increases so much that stars become isolated from each other, then planets from stars, then molecules from each other, then atoms, and then quarks, the constituents of matter itself, and then.... An interesting thing happens. When you tear a quark away from it's antiquark, you get two quarks. The energy is equal to that required to bring another quark into existence. At this point, the rate of expansion is so vast that every quark in the universe has been forever isolated from one another, and then each bursts into a sea of high-energy quark-gluon plasma. The massive energy of expansion is rapidly consumed generating these quarks, and then the expansion slows, never stopping, but continues at a much slower rate. Wait... we've seen this before. A quark-gluon plasma, rapidly expanding from a single point, in a universe isolated from all others. Only expansion is required to generate new universes, forever.
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  - treeman79 6y ago
    Gravity is traveling at the speed of light. Space is expanding. Objects far apart are traveling away from each faster than the speed of light. Or more that the space between them is expanding faster then the speed of light. So those objects will never have any sort of interaction. Only ways around this if space itself start contracting. (No known way for this to happen). Or somehow the universe is a big circle, and going far enough brings you back to the starting point. Negative curvature. We don’t have any good theories on this. Some highly interesting ones that move the problem up a level. For Example one theory is our entire universe is inside a black hole created from the remains of a four dimensional hyper star. The math seems to work. Soo cool. But then where does the hyper star come from? It’s “turtles all the way down”, is the thought to lot of the best theories. Or everything is a simulation, again math kind of works. No direct evidence, but neat idea. But who’s hosting the sever that’s running the universe. Something from nothing problem is a real trouble maker.
    - Johnjonjoan 6y ago
      Objects far apart may be traveling faster than the speed of light but once the universe reaches equilibrium won't there be intermediate masses that gravity will be able to travel through? I was also under the impression that an expansion of space would just reduce the gradient of the gravity along that space and not inhibit its propagation. If like a bubble space has some form of surface tension then would there be a point that it can no longer expand? Gravity could then become dominant and force the contraction. -edit-> I guess that wouldn't contract the space though just the matter? I promise I'm not being pedantic or contrarian for the sake of it but to further my knowledge, thanks for your input!
      - fhars 6y ago
        There is no "equilibrium" the universe is moving towards, it is just expanding, and the "intermediate masses" are getting more spread out the more the universe expands. The expansion doesn't inhibit the propagation of gravity, it just makes the attraction between masses weaker and weaker the further they are apart, until they are so far apart that the space between them expands faster than the speed of light, at which moment they will no longer be able to interact with another, neither by light nor by gravity, and the contracting effect of gravity becomes weaker and weaker the larger the universe becomes. According to out current best cosmological model, Lambda-CDM (which, admittedly, is mostly a phenomenological model for things we only half understand, but still describes our current observations better than any competing model), gravity used to be the dominant force in the universe when it was smaller so that the masses were closer together until quite recently. But now it looks like the expansion, the "Lambda" term in "Lambda-CDM", the cosmological constant of general relativity, has become the dominant force in the universe, and the universe is slated to expand ever faster. It could start to contract if Lambda were closer to zero, but it currently doesn't look like it might move there. But then we don't know why Lambda it there at all and what causes it not to be zero in the first place, as everyone expected it to be until about two decades ago (Einstein himself thought of the introduction of the term into his theory as a blunder, as it would obviously be zero in any sane universe.)
  - hacknat 6y ago
    The Universe can be infinite without being cyclic.
- deleted 6y ago
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- sago 6y ago
  I'm not the physicist (my mother was), but as I understand it the 'came into existence' is not part of the big bang model. Big bang only makes sense to a particular energy/time/space limit. All the energy that came to be all the universe already existed. What happened 'before that' doesn't even make sense. I was told that 'creation' type language is a misunderstanding of the big bang. Is that not still the way it works?
  - simonh 6y ago
    The Big Bang theory itself doesn't answer the question of where the Universe came from, but I don't think it's stilly to ask what happened 'before' the Big Bang, or when the size of the Universe was near or below the Planck Scale. Relativity by itself predicts a singularity at a finite time in the past, at the beginning of the Big Bang. We know from Quantum Mechanics that Relativity is not complete though so the origin of the Universe and the nature of time through that process is still up in the air.
    - mensetmanusman 6y ago
      How can one speak of the size of the universe before the big bang if the concept of space-time was created during the event?
      - simonh 6y ago
        How do you know the concept of space-time was created during the event though? That's just an assertion. This theory, and the theory of conformal cyclic cosmology proposed by Roger Penrose do not have that feature, for example.
      - MacsHeadroom 6y ago
        Size and progression do not require space or time. The quantity of nodes in a branching tree of causal events can grow larger without time or space if there is no reccurance for any given state to be compared to another. From the "gods eye view" the tree "grows" even if there's no internal information which can be used to recover any space/time prior to reccurance.
- state_less 6y ago
  A circle doesn’t have a beginning or an end, yet folks seem to be okay dealing with them. Personally, I’m stumbling on understanding physical fields. This looks like another field is being added, which is nice in some sense, but why do we have the number of fields that we do and what conditions are needed to create/sustain physical fields?
  - JamesSwift 6y ago
    The issue is not that a circle has no beginning and end, but what led to the creation of the circle in the first place? It didn't materialize from nothingness, I drew it on a paper.
    - state_less 6y ago
      Rather than materialize from nothing, every event would be connected to the next and if you proceed along the events, you'll eventually see the same/similar events again. Sort of like a circularly linked list.
      - pravus 6y ago
        Except now you have a winding number and the two circles aren't equivalent everywhere.
- onion2k 6y ago
  The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. It's only an issue if you think about space and time as separate things. I find it makes (a little) more sense when you understand that time is a function of spacetime. Therefore if you're happy with space not existing prior to the big bang (which people do seem to be OK with) then automatically time didn't exist either, and hence 'before the big bang' ceases to be a problem.
  - simonh 6y ago
    That's just a semantic dodge to avoid answering phrasings of the question that use the term 'before'. However the comment you're replying to didn't use the 'before' phrasing. We can't dodge the broader question of how, or why the Universe came about in the particular form that it did so easily.
    - asdfasgasdgasdg 6y ago
      You can dodge further by saying that causality only exists in space time, so asking what "caused" the start of space time is incoherent. But, "it just did" has never been a satisfactory answer outside the halls of churches and seminaries, so this dodge continues to be unsatisfying.
      - mensetmanusman 6y ago
        The phrasing is worded wrong here: “it just did” has never been a satisfactory answer inside of churches or seminaries. That is why almost all the metaphysical discussion in these areas of human thought are around why we exist (in human terms). “it just did” has been a satisfactory answer outside of churches or seminaries. This is why almost all discussion of why there is something rather than nothing in secular academia is ‘meh, impossible to know, don’t worry about it’
  - istjohn 6y ago
    This is what gets me. I can imagine no space and no time. But in a reality without space and time, by definition, nothing happens. There is nothing to act or be acted on. There is no timeline by which to order cause and effect. But the Big Bang posits that, in fact, something did happen: space and time began. The most incredible event imaginable occurred in the most impossible circumstance. It just doesn't compute for me. It's much easier for me to imagine that time is just turtles all the way down.
- Santosh83 6y ago
  Actually I find an absolute beginning and an absolute ending more troublesome to think about. It is easier to accept that in reality while everything keeps changing and recycling, the sum total has always been.
  - stOneskull 6y ago
    why there is something at all, i think we can never know. but yeah, likewise. it seems energy/things existing for infinity is the only thing that makes sense, and something coming from nothing is impossible. i think a part of us wants there to be a beginning but there really can't be.
    - aspaviento 6y ago
      On the other hand, maybe this bouncing is completely deterministic and we are meant to do the exact same things we did trillions of years ago.
      - ssijak 6y ago
        If the universe has infinite bounces than yes, there are countless universes in the past and future where I type this same message.
    - ssijak 6y ago
      “Why there is something at all?” The only answer I can satisfy myself with at least a bit is that there is no option for nothing to exist.
- Allower 6y ago
  Probably because its a really weak theory..folks in the scientific community are grasping at straws far more than they are willing to admit. For some sense, just notice how rare it is for any so-called "expert" to preface their statements with "as far as we know" or some other similarly appropriate hedge.
oxymoran 6y ago
The universe always having always existed makes slightly more sense to me than it just popping out of nowhere. Sure, from the Big Bang onwards the inflation theory seemed to make sense but it didn’t explain how everything could magically erupt out of nothing or what caused said eruption when nothing existed prior to it. For all the crap that religions get for believing in nonsense, I always felt the Big Bang was a scientific parallel.
- augustl 6y ago
  The way I'm put together, both ideas makes me uneasy when I _really_ think about them. There used to be no universe? Ugh :( There's always been an universe? How's that possible? Ugh :(
- umvi 6y ago
  > For all the crap that religions get for believing in nonsense Curiously, Latter Day Saints (aka Mormons) have taught for over a century that essentially the Big Bang theory is incorrect and that matter has always existed and that when the Earth was created God simply "organized" existing matter rather than conjuring something out of nothing. Putting aside their other beliefs I thought this was an interesting curiosity in this context.
  - mrkstu 6y ago
    Yep- there is a reason there are so many Mormon sci-fi authors and why Mormons are one of the few religions where engagement increases with education. Growing up LDS there was never any existential angst as I became more educated and there was never a need to overcome any cognitive dissonance as I learned evolution or cosmology- the baseline belief is a very sci-fi one of the first super-consciousness (God) taking upon itself the shaping of spiritual (dark matter?) and then physical matter and making pathways for other intelligences to master the same. No ex-nihilo involved. Even if the LDS specific conceptions have all the details wrong, the overarching idea is completely plausible.
- mensetmanusman 6y ago
  Religion simply starts with the idea that what we observe is not meaningless. Reality is often stranger and more incomprehensible than fiction.
catmistake 6y ago
As I have long suspected, though computer science is a subset of mathematics, cosmology is actually a subset of computer science.
- Johnjonjoan 6y ago
  They're both variations on information theory.
ralfd 6y ago
I thought the universe is too big as to contract again?
- mabbo 6y ago
  The results don't necessarily tell us about the future- but that there may have been a bounce in the past. As far as being too big, that's not quite it. Everything is moving away from each other because of the big bang, but astronomers realized that hey, gravity should be slowing that down. So they tried to measure the deceleration of the expansion of the universe. Instead they found it's accelerating. There's a lot of theories as to why, but right now it's just called "Dark Energy" because no one really has a full understanding of it. Space itself seems to be stretching out, becoming larger. Will the acceleration of expansion continue forever? Maybe someday it will slow and reverse? No one is sure yet.
sliken 6y ago
My biggest problem with the big bang is why didn't the incredible density of energy (it hadn't cooled enough for matter) just turn into a black hole? The big bounce avoids this particular problem.
- JesseMeyer 6y ago
  Inflationary theory. Someone more educated on the topic can pine in, but my lay understanding is that the output of some form of primeval radioactive decay (Big Bang) caused a phenomenal rate of spacial expansion, which caused space to expand faster than the rate of gravitational collapse in those first moments.
  - sliken 6y ago
    It's not the rate of gravitational collapse you have to beat, it's the speed of light. Although I guess that makes sense. After all it's spacetime, not space. So if the expansion rate is higher than the speed of light, then you don't have the black hole problem.
- mensetmanusman 6y ago
  There has to be spacetime to form a black hole, where would it find such spacetime before the big bang...
  - sliken 6y ago
    Well what about 0.000001 seconds after the big bang (add zeros as needed).
- LockAndLol 6y ago
  Why does it avoid the problem? > Over billions of years a contracting scale factor brings everything a bit closer, but not all the way down to a point. The dramatic change comes from the Hubble radius, which rushes in and eventually becomes microscopic All the matter of universe at a microscopic radius? That doesn't avoid the problem.
- 6y ago
OneGuy123 6y ago
The bing bang is way too accepted in the mainststream: in reality there is no concrete proof for it. Therefore we can either: a) Fit the models to fit the data. b) Invent more physical phenomena to make it fit the data (quasi particles in physics). There is nothing wrong in doing that, but there is severe arrogance of saying that "the bing bang happened" where in reality we just have a hypothesis. And even "the most widely accepted by CONSENSUS" hyptothesis doesn't make mean is actually TRUE. It's perfectly fine to make new theories, but at the end of the day we simply don't know enough: and yet the mainstream/every kid believes in the the bing bang to the extend as religous people believe in God.
- dkersten 6y ago
  It was my understanding that physicists have never claimed that the big bang happened. That the big bang itself isn’t really part of the theory at all and that its simply a singularity point, but that some moments before that point, ohysics as we know it breaks down, so we don’t know what happened before and therefore do ‘t know if there was a bang or not, just that after that time, things happened that we can measure. Put another way, the big bang theory doesn’t include the big bang itself (the something from nothing part) but is about the inflation and expansion of the universe. Here are some PBS Space Time videos on the subject: Why the big bang definitely happened: https://youtu.be/aPStj2ZuXug https://youtu.be/aPStj2ZuXug Did time start at the big bang: https://youtu.be/K8gV05nS7mc https://youtu.be/K8gV05nS7mc Whats wrong with the big bang theory: https://youtu.be/JDmKLXVFJzk https://youtu.be/JDmKLXVFJzk “In the beginning, there was nothing, which exploded”, now, a lot of non-scientists like to repeat this statement, but no credible scientist has ever said this, nor believes it. So its unfortunate that this statement is used to deride the big bang theory. The big bang describes a series of events that happened to the universe following its existence in an extremely hot, dense state. We have a ton of evidence that the universe was once in such a state. Perhaps our understanding of this state will eventually lead to a theory of the origin of the universe, but the big bang theory as it stands does not claim to explain such an origin. — Matt O’Dowd, PBS Space Time
- ryanianian 6y ago
  I mean. Sure? This is how science works. The "theory" of evolution is the same thing. We have no "proof" of it. But of course we do. Evidence is all around us, being evaluated in a multitude of ways by a multitude of people using different sources of data making similar conclusions supported by experiments and evidence. This is basically how we define "fact". Of course somebody may stumble onto something that blows the whole equation up, but barring that, we have sufficient confidence to say it's fact. Granted the big bang theory is harder to observe, study, and experiment. Doesn't change how it's viewed by science. (TFA opens with this. It suggests the possibility of something that may blow up the equation. Great. Similarly, if somebody can find something that disproves evolution that would be pretty ground-breaking, but the more established a fact, the higher the burden of proof.)
mellosouls 6y ago
TL:DR; despite the title, mostly the theory challenges inflation (which itself was originally partly an attempt to answer predictive flaws with earlier cyclic theories) - the big bang itself is countered in so far as a "single point" state is not required. With this continuous (eternal?) contraction and expansion, I'm reminded eerily of a heart beating, or something breathing...
Zamicol 6y ago
I despise the big bounce because it's dogmatic in origin. "It makes sense that the universe just bounces instead of 'coming from nowhere'!" Every time cosmologists looked, the universe got bigger and suggested growth. The big bounce at no point in history ever looked right. Moreover, the big bounce kicks the bucket down the road. It ultimately has the same metaphysical issues. I find the reasoning poor as well. "I don't like inflation" != "The universe ends in contraction". Yes, it's proven difficult to explain CMB smoothness, but this doesn't mean the big bounce is a better candidate than other non-empirical ideas. I'm confident truth will be far stranger than big bounce fiction.
- mytailorisrich 6y ago
  The metaphysical issues are unavoidable because whatever the theory we come up with or, I think, whatever the reality is, it can only fall within 2 possibilities: - Infinity: There is no beginning and something always precedes the 'current' step (e.g. the Big Bang occurred out of something) - Discontinuity: There is a beginning. Everything suddenly started out of nothing. While both options are hard to grasp for the human mind, the second one, which is the standard Big Bang also sits very uncomfortably with Physics' concepts and is the more 'disturbing' of the two. I think that's why people have been looking for alternatives to the standard Big Bang theory. Infinity, is still unfathomable but at least it is easier to fit Maths and Physics around. Even adding God to the mix still leads to these 2 options, because if the Universe was created by 'God' it implies that the Big Bang is not the beginning and that something (God) pre-existed. The idea that we might be in a simulation is equivalent to a creator God, just more hi-tech. It really seems to me that these alternatives, infinity or discontinuity, are inescapable.
  - mensetmanusman 6y ago
    Yes, it’s silly to think the metaphysical issues would go away if we somehow proved the universe has been bouncing around for infinity amount of time.
    - cthonicthulu 6y ago
Santosh83 6y ago
It is also worth nothing that cyclic cosmogony was envisioned more than two millennia ago in Hinduism. https://en.wikipedia.org/wiki/Hindu_cosmology https://en.wikipedia.org/wiki/Hindu_cosmology
breakbread 6y ago
This seems at least superficially similar to Roger Penrose's Conformal Cyclic Cosmology theory. Anyone here able to weigh in on that?
blocked_again 6y ago
Anyone else when they think about the origin of Universe for a long time, start to wonder how the hell do we even exist and get a feeling like a panic attack? I don't really know how to accurately describe the feeling. Its a very weird sensation. It only happens when I think about the origin of Universe. And its very very hard to arrive at that state. Requires a lot of concentration. I must have experienced it like less than 5 or 6 times in my life so far.
- jacobedawson 6y ago
  I love / hate the sensation when you try to conceive that it (it including whatever includes "it", ad infinitum) has either existed forever or there was a point before anything existed.
- fatnoah 6y ago
  >Anyone else had the feeling where you think about the origin of Universe for a long time, it doesn't make any sense and you almost get a panic attack? For whatever reason, it makes more more anxious than it should. The concepts involved are so far removed from my brain's understanding of reality that it makes me uncomfortable.
- JamesSwift 6y ago
  I think of it as having an "existential crisis". Its not just limited to thinking about the universe for me, but things like eventual death and all those "impossible to understand" topics.
- Sevrene 6y ago
  For sure, I have experienced similar feelings. Good to know it's not just me. It's kind of like a derealization caused by the thought of how absurd or odd it is that we exist at all.
- maze-le 6y ago
  It is called existential anxiety, it shows that you are able to contemplate about your own insignificance in contrast to the grand scheme of things (universe, all of existence, etc.). We all have it on one level or another, I used to have it when looking into a dark cloudless night, realizing that all of the little dots I can see out there could technically be orbited by another planet that bears life, inhabited by millions or billions of other lifeforms that could be able to feel and think. Usually it is nothing to worry about, except when you get obsessed by it and it starts to control aspects of your life because you build a worldview around it or try hard to avoid it or explain it away: then it is called an existential crisis. But what it really means is that the mind gets overwhelmed by the fact that the universe is orders of magnitudes more complex than what the self has ever encountered in our daily lifes. Our brains have evolved so that bipedal apes that migrated from forests into the steppes can survive and cooperate in groups. It was never meant to be confronted by questions of this dimension, but yet here we are. You can make your peace with it, and embrace it. It can also be a source of endless curiosity, spirituality and creativity.
caiobegotti 6y ago
I have never heard about Big Bounce before, honestly, but the illustration at the top of the article basically made sense in a heart beat and I'm impressed how simple yet how much of the idea it conveys, apparently, correctly. Kudos to the visual artist, usually these scientific illustrations used to explain a weird or novel idea are over the top.
- alchemism 6y ago
  I vaguely recall hearing of this from a different field of study. https://www.cs.ubc.ca/~goyal/age_of_universe.php https://www.cs.ubc.ca/~goyal/age_of_universe.php
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JadoJodo 6y ago
Sir Roger Penrose and Dr William Lane Craig had an interesting discussion[0] that included him talking about the Big Bounce (around the 50-minute mark). [0] https://youtu.be/9wLtCqm72-Y https://youtu.be/9wLtCqm72-Y
monktastic1 6y ago
Many comments here address an important issue: the human mind has a hard time making sense of both an eternally existing universe, as well as something-from-nothing. But most of the issues stem from presupposing physicalism. It's understood even by staunch physicalists that choosing this metaphysics is ultimately arbitrary[1]. There's another way to approach all this. Start by asking: what's the one thing I know for certain? It's hard to say any more than it certainly seems like something is happening. Investigate this sheer fact of "seeming." See what the seeming is like before you apply any metaphysics on top of it. What happens when you do this extremely precisely? Suppose that the correct metaphysics is that you are ultimately the primordial ground of being, that (paradoxically) weaves itself into apparent realities. What we think of as physical reality is just one instance. It transcends parameters like time and causality, but can give rise to them of its own will. Being the primordial ground of being, nothing logically prevents you from knowing this ultimate truth directly and unequivocally (unlike if you were really just a human). As it so happens, the preceding paragraph describes how you would (re)arrive at this knowing. Or at least, that's what's suggested by various mystical traditions. As far as I can tell, there's definitely something to it. [1] "There is no way to distinguish between the scenarios by collecting new data. What we’re left with is our choice of prior credences. We’re allowed to pick priors however we want. [...] We have every right to give high credence to views of the world that are productive and fruitful." —Sean Carroll, The Big Picture (p.91)
cloudking 6y ago
There's some interesting theories about what was happening before the big bang in the Joe Rogan interview with Brian Greene https://youtu.be/FHAA_1Guxlo https://youtu.be/FHAA_1Guxlo
Razengan 6y ago
Most human questions about the origin of things assume that the default state must be Nothing. Why can't it be Everything? i.e., instead of imagining the Universe as a white dot on a black canvas, how about thinking of it as a black dot on a white background?

127 points by SirLJ 6y ago

Both theories are somewhat incomprehensible for normal human beings. The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. We humans are inherently bad in dealing with these terms.

Johnjonjoan 6y ago
You're right of course but I find the cyclic version so much more intuitive. The force from the big bang was imparted in an instant yet gravity is a constant force. IANAP but surely at some point the accumulative force of billions/trillions/... of years of gravity overcomes the force imparted by the big bang and the universe compresses into a singularity again? I'd really appreciate someone explaining why this isn't obviously the case.
- coldcode 6y ago
  I'm not sure we can ever tell the difference between the two models. Given the assumption that both produce a "boring" universe, and that models are never completely verifiable, it could be that either pathway appears the same to us at this point in time.
- tyfon 6y ago
  The issue with this view is that in the universe we see today the gravitational force is not strong enough to do what you describe here. There is acceleration of the expansion i.e. energy is added to the system (in the form of vacuum energy possibly). To say it in another way, the energy used to expand the universe today is not only the initial force imparted by the big bang but is added to as part of quantum processes in empty space. However as the universe expands, the amount of matter (dark + luminous) does not increase so the proportion of gravity/matter to dark energy (the force that accelerates the expansion) is getting lower and we get an acceleration. These observations exclude the possibility of a "big crunch". Disclaimer: I am a statistician not a cosmologist but this is how I have understood it.
  - Johnjonjoan 6y ago
    Cheers, I now understand why it's not such a clear case. I fear I may have many more harder to answer questions now though - Thanks none the less!
    - GioM 6y ago
      Take the idea a little further, to the end of the universe, and the rate of acceleration of expansion of space increases so much that stars become isolated from each other, then planets from stars, then molecules from each other, then atoms, and then quarks, the constituents of matter itself, and then.... An interesting thing happens. When you tear a quark away from it's antiquark, you get two quarks. The energy is equal to that required to bring another quark into existence. At this point, the rate of expansion is so vast that every quark in the universe has been forever isolated from one another, and then each bursts into a sea of high-energy quark-gluon plasma. The massive energy of expansion is rapidly consumed generating these quarks, and then the expansion slows, never stopping, but continues at a much slower rate. Wait... we've seen this before. A quark-gluon plasma, rapidly expanding from a single point, in a universe isolated from all others. Only expansion is required to generate new universes, forever.
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- treeman79 6y ago
  Gravity is traveling at the speed of light. Space is expanding. Objects far apart are traveling away from each faster than the speed of light. Or more that the space between them is expanding faster then the speed of light. So those objects will never have any sort of interaction. Only ways around this if space itself start contracting. (No known way for this to happen). Or somehow the universe is a big circle, and going far enough brings you back to the starting point. Negative curvature. We don’t have any good theories on this. Some highly interesting ones that move the problem up a level. For Example one theory is our entire universe is inside a black hole created from the remains of a four dimensional hyper star. The math seems to work. Soo cool. But then where does the hyper star come from? It’s “turtles all the way down”, is the thought to lot of the best theories. Or everything is a simulation, again math kind of works. No direct evidence, but neat idea. But who’s hosting the sever that’s running the universe. Something from nothing problem is a real trouble maker.
  - Johnjonjoan 6y ago
    Objects far apart may be traveling faster than the speed of light but once the universe reaches equilibrium won't there be intermediate masses that gravity will be able to travel through? I was also under the impression that an expansion of space would just reduce the gradient of the gravity along that space and not inhibit its propagation. If like a bubble space has some form of surface tension then would there be a point that it can no longer expand? Gravity could then become dominant and force the contraction. -edit-> I guess that wouldn't contract the space though just the matter? I promise I'm not being pedantic or contrarian for the sake of it but to further my knowledge, thanks for your input!
    - fhars 6y ago
      There is no "equilibrium" the universe is moving towards, it is just expanding, and the "intermediate masses" are getting more spread out the more the universe expands. The expansion doesn't inhibit the propagation of gravity, it just makes the attraction between masses weaker and weaker the further they are apart, until they are so far apart that the space between them expands faster than the speed of light, at which moment they will no longer be able to interact with another, neither by light nor by gravity, and the contracting effect of gravity becomes weaker and weaker the larger the universe becomes. According to out current best cosmological model, Lambda-CDM (which, admittedly, is mostly a phenomenological model for things we only half understand, but still describes our current observations better than any competing model), gravity used to be the dominant force in the universe when it was smaller so that the masses were closer together until quite recently. But now it looks like the expansion, the "Lambda" term in "Lambda-CDM", the cosmological constant of general relativity, has become the dominant force in the universe, and the universe is slated to expand ever faster. It could start to contract if Lambda were closer to zero, but it currently doesn't look like it might move there. But then we don't know why Lambda it there at all and what causes it not to be zero in the first place, as everyone expected it to be until about two decades ago (Einstein himself thought of the introduction of the term into his theory as a blunder, as it would obviously be zero in any sane universe.)
- hacknat 6y ago
  The Universe can be infinite without being cyclic.
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sago 6y ago
I'm not the physicist (my mother was), but as I understand it the 'came into existence' is not part of the big bang model. Big bang only makes sense to a particular energy/time/space limit. All the energy that came to be all the universe already existed. What happened 'before that' doesn't even make sense. I was told that 'creation' type language is a misunderstanding of the big bang. Is that not still the way it works?
- simonh 6y ago
  The Big Bang theory itself doesn't answer the question of where the Universe came from, but I don't think it's stilly to ask what happened 'before' the Big Bang, or when the size of the Universe was near or below the Planck Scale. Relativity by itself predicts a singularity at a finite time in the past, at the beginning of the Big Bang. We know from Quantum Mechanics that Relativity is not complete though so the origin of the Universe and the nature of time through that process is still up in the air.
  - mensetmanusman 6y ago
    How can one speak of the size of the universe before the big bang if the concept of space-time was created during the event?
    - simonh 6y ago
      How do you know the concept of space-time was created during the event though? That's just an assertion. This theory, and the theory of conformal cyclic cosmology proposed by Roger Penrose do not have that feature, for example.
    - MacsHeadroom 6y ago
      Size and progression do not require space or time. The quantity of nodes in a branching tree of causal events can grow larger without time or space if there is no reccurance for any given state to be compared to another. From the "gods eye view" the tree "grows" even if there's no internal information which can be used to recover any space/time prior to reccurance.
state_less 6y ago
A circle doesn’t have a beginning or an end, yet folks seem to be okay dealing with them. Personally, I’m stumbling on understanding physical fields. This looks like another field is being added, which is nice in some sense, but why do we have the number of fields that we do and what conditions are needed to create/sustain physical fields?
- JamesSwift 6y ago
  The issue is not that a circle has no beginning and end, but what led to the creation of the circle in the first place? It didn't materialize from nothingness, I drew it on a paper.
  - state_less 6y ago
    Rather than materialize from nothing, every event would be connected to the next and if you proceed along the events, you'll eventually see the same/similar events again. Sort of like a circularly linked list.
    - pravus 6y ago
      Except now you have a winding number and the two circles aren't equivalent everywhere.
onion2k 6y ago
The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. It's only an issue if you think about space and time as separate things. I find it makes (a little) more sense when you understand that time is a function of spacetime. Therefore if you're happy with space not existing prior to the big bang (which people do seem to be OK with) then automatically time didn't exist either, and hence 'before the big bang' ceases to be a problem.
- simonh 6y ago
  That's just a semantic dodge to avoid answering phrasings of the question that use the term 'before'. However the comment you're replying to didn't use the 'before' phrasing. We can't dodge the broader question of how, or why the Universe came about in the particular form that it did so easily.
  - asdfasgasdgasdg 6y ago
    You can dodge further by saying that causality only exists in space time, so asking what "caused" the start of space time is incoherent. But, "it just did" has never been a satisfactory answer outside the halls of churches and seminaries, so this dodge continues to be unsatisfying.
    - mensetmanusman 6y ago
      The phrasing is worded wrong here: “it just did” has never been a satisfactory answer inside of churches or seminaries. That is why almost all the metaphysical discussion in these areas of human thought are around why we exist (in human terms). “it just did” has been a satisfactory answer outside of churches or seminaries. This is why almost all discussion of why there is something rather than nothing in secular academia is ‘meh, impossible to know, don’t worry about it’
- istjohn 6y ago
  This is what gets me. I can imagine no space and no time. But in a reality without space and time, by definition, nothing happens. There is nothing to act or be acted on. There is no timeline by which to order cause and effect. But the Big Bang posits that, in fact, something did happen: space and time began. The most incredible event imaginable occurred in the most impossible circumstance. It just doesn't compute for me. It's much easier for me to imagine that time is just turtles all the way down.
Santosh83 6y ago
Actually I find an absolute beginning and an absolute ending more troublesome to think about. It is easier to accept that in reality while everything keeps changing and recycling, the sum total has always been.
- stOneskull 6y ago
  why there is something at all, i think we can never know. but yeah, likewise. it seems energy/things existing for infinity is the only thing that makes sense, and something coming from nothing is impossible. i think a part of us wants there to be a beginning but there really can't be.
  - aspaviento 6y ago
    On the other hand, maybe this bouncing is completely deterministic and we are meant to do the exact same things we did trillions of years ago.
    - ssijak 6y ago
      If the universe has infinite bounces than yes, there are countless universes in the past and future where I type this same message.
  - ssijak 6y ago
    “Why there is something at all?” The only answer I can satisfy myself with at least a bit is that there is no option for nothing to exist.
Allower 6y ago
Probably because its a really weak theory..folks in the scientific community are grasping at straws far more than they are willing to admit. For some sense, just notice how rare it is for any so-called "expert" to preface their statements with "as far as we know" or some other similarly appropriate hedge.

oxymoran 6y ago

The universe always having always existed makes slightly more sense to me than it just popping out of nowhere. Sure, from the Big Bang onwards the inflation theory seemed to make sense but it didn’t explain how everything could magically erupt out of nothing or what caused said eruption when nothing existed prior to it. For all the crap that religions get for believing in nonsense, I always felt the Big Bang was a scientific parallel.

augustl 6y ago
The way I'm put together, both ideas makes me uneasy when I _really_ think about them. There used to be no universe? Ugh :( There's always been an universe? How's that possible? Ugh :(
umvi 6y ago
> For all the crap that religions get for believing in nonsense Curiously, Latter Day Saints (aka Mormons) have taught for over a century that essentially the Big Bang theory is incorrect and that matter has always existed and that when the Earth was created God simply "organized" existing matter rather than conjuring something out of nothing. Putting aside their other beliefs I thought this was an interesting curiosity in this context.
- mrkstu 6y ago
  Yep- there is a reason there are so many Mormon sci-fi authors and why Mormons are one of the few religions where engagement increases with education. Growing up LDS there was never any existential angst as I became more educated and there was never a need to overcome any cognitive dissonance as I learned evolution or cosmology- the baseline belief is a very sci-fi one of the first super-consciousness (God) taking upon itself the shaping of spiritual (dark matter?) and then physical matter and making pathways for other intelligences to master the same. No ex-nihilo involved. Even if the LDS specific conceptions have all the details wrong, the overarching idea is completely plausible.
mensetmanusman 6y ago
Religion simply starts with the idea that what we observe is not meaningless. Reality is often stranger and more incomprehensible than fiction.

catmistake 6y ago

As I have long suspected, though computer science is a subset of mathematics, cosmology is actually a subset of computer science.

Johnjonjoan 6y ago
They're both variations on information theory.

ralfd 6y ago

I thought the universe is too big as to contract again?

mabbo 6y ago
The results don't necessarily tell us about the future- but that there may have been a bounce in the past. As far as being too big, that's not quite it. Everything is moving away from each other because of the big bang, but astronomers realized that hey, gravity should be slowing that down. So they tried to measure the deceleration of the expansion of the universe. Instead they found it's accelerating. There's a lot of theories as to why, but right now it's just called "Dark Energy" because no one really has a full understanding of it. Space itself seems to be stretching out, becoming larger. Will the acceleration of expansion continue forever? Maybe someday it will slow and reverse? No one is sure yet.

sliken 6y ago

My biggest problem with the big bang is why didn't the incredible density of energy (it hadn't cooled enough for matter) just turn into a black hole? The big bounce avoids this particular problem.

JesseMeyer 6y ago
Inflationary theory. Someone more educated on the topic can pine in, but my lay understanding is that the output of some form of primeval radioactive decay (Big Bang) caused a phenomenal rate of spacial expansion, which caused space to expand faster than the rate of gravitational collapse in those first moments.
- sliken 6y ago
  It's not the rate of gravitational collapse you have to beat, it's the speed of light. Although I guess that makes sense. After all it's spacetime, not space. So if the expansion rate is higher than the speed of light, then you don't have the black hole problem.
mensetmanusman 6y ago
There has to be spacetime to form a black hole, where would it find such spacetime before the big bang...
- sliken 6y ago
  Well what about 0.000001 seconds after the big bang (add zeros as needed).
LockAndLol 6y ago
Why does it avoid the problem? > Over billions of years a contracting scale factor brings everything a bit closer, but not all the way down to a point. The dramatic change comes from the Hubble radius, which rushes in and eventually becomes microscopic All the matter of universe at a microscopic radius? That doesn't avoid the problem.
6y ago

OneGuy123 6y ago

The bing bang is way too accepted in the mainststream: in reality there is no concrete proof for it. Therefore we can either: a) Fit the models to fit the data. b) Invent more physical phenomena to make it fit the data (quasi particles in physics). There is nothing wrong in doing that, but there is severe arrogance of saying that "the bing bang happened" where in reality we just have a hypothesis. And even "the most widely accepted by CONSENSUS" hyptothesis doesn't make mean is actually TRUE. It's perfectly fine to make new theories, but at the end of the day we simply don't know enough: and yet the mainstream/every kid believes in the the bing bang to the extend as religous people believe in God.

dkersten 6y ago
It was my understanding that physicists have never claimed that the big bang happened. That the big bang itself isn’t really part of the theory at all and that its simply a singularity point, but that some moments before that point, ohysics as we know it breaks down, so we don’t know what happened before and therefore do ‘t know if there was a bang or not, just that after that time, things happened that we can measure. Put another way, the big bang theory doesn’t include the big bang itself (the something from nothing part) but is about the inflation and expansion of the universe. Here are some PBS Space Time videos on the subject: Why the big bang definitely happened: https://youtu.be/aPStj2ZuXug https://youtu.be/aPStj2ZuXug Did time start at the big bang: https://youtu.be/K8gV05nS7mc https://youtu.be/K8gV05nS7mc Whats wrong with the big bang theory: https://youtu.be/JDmKLXVFJzk https://youtu.be/JDmKLXVFJzk “In the beginning, there was nothing, which exploded”, now, a lot of non-scientists like to repeat this statement, but no credible scientist has ever said this, nor believes it. So its unfortunate that this statement is used to deride the big bang theory. The big bang describes a series of events that happened to the universe following its existence in an extremely hot, dense state. We have a ton of evidence that the universe was once in such a state. Perhaps our understanding of this state will eventually lead to a theory of the origin of the universe, but the big bang theory as it stands does not claim to explain such an origin. — Matt O’Dowd, PBS Space Time
ryanianian 6y ago
I mean. Sure? This is how science works. The "theory" of evolution is the same thing. We have no "proof" of it. But of course we do. Evidence is all around us, being evaluated in a multitude of ways by a multitude of people using different sources of data making similar conclusions supported by experiments and evidence. This is basically how we define "fact". Of course somebody may stumble onto something that blows the whole equation up, but barring that, we have sufficient confidence to say it's fact. Granted the big bang theory is harder to observe, study, and experiment. Doesn't change how it's viewed by science. (TFA opens with this. It suggests the possibility of something that may blow up the equation. Great. Similarly, if somebody can find something that disproves evolution that would be pretty ground-breaking, but the more established a fact, the higher the burden of proof.)

mellosouls 6y ago

TL:DR; despite the title, mostly the theory challenges inflation (which itself was originally partly an attempt to answer predictive flaws with earlier cyclic theories) - the big bang itself is countered in so far as a "single point" state is not required. With this continuous (eternal?) contraction and expansion, I'm reminded eerily of a heart beating, or something breathing...

Zamicol 6y ago

I despise the big bounce because it's dogmatic in origin. "It makes sense that the universe just bounces instead of 'coming from nowhere'!" Every time cosmologists looked, the universe got bigger and suggested growth. The big bounce at no point in history ever looked right. Moreover, the big bounce kicks the bucket down the road. It ultimately has the same metaphysical issues. I find the reasoning poor as well. "I don't like inflation" != "The universe ends in contraction". Yes, it's proven difficult to explain CMB smoothness, but this doesn't mean the big bounce is a better candidate than other non-empirical ideas. I'm confident truth will be far stranger than big bounce fiction.

mytailorisrich 6y ago
The metaphysical issues are unavoidable because whatever the theory we come up with or, I think, whatever the reality is, it can only fall within 2 possibilities: - Infinity: There is no beginning and something always precedes the 'current' step (e.g. the Big Bang occurred out of something) - Discontinuity: There is a beginning. Everything suddenly started out of nothing. While both options are hard to grasp for the human mind, the second one, which is the standard Big Bang also sits very uncomfortably with Physics' concepts and is the more 'disturbing' of the two. I think that's why people have been looking for alternatives to the standard Big Bang theory. Infinity, is still unfathomable but at least it is easier to fit Maths and Physics around. Even adding God to the mix still leads to these 2 options, because if the Universe was created by 'God' it implies that the Big Bang is not the beginning and that something (God) pre-existed. The idea that we might be in a simulation is equivalent to a creator God, just more hi-tech. It really seems to me that these alternatives, infinity or discontinuity, are inescapable.
- mensetmanusman 6y ago
  Yes, it’s silly to think the metaphysical issues would go away if we somehow proved the universe has been bouncing around for infinity amount of time.
  - cthonicthulu 6y ago

Santosh83 6y ago

It is also worth nothing that cyclic cosmogony was envisioned more than two millennia ago in Hinduism. https://en.wikipedia.org/wiki/Hindu_cosmology https://en.wikipedia.org/wiki/Hindu_cosmology

breakbread 6y ago

This seems at least superficially similar to Roger Penrose's Conformal Cyclic Cosmology theory. Anyone here able to weigh in on that?

blocked_again 6y ago

Anyone else when they think about the origin of Universe for a long time, start to wonder how the hell do we even exist and get a feeling like a panic attack? I don't really know how to accurately describe the feeling. Its a very weird sensation. It only happens when I think about the origin of Universe. And its very very hard to arrive at that state. Requires a lot of concentration. I must have experienced it like less than 5 or 6 times in my life so far.

jacobedawson 6y ago
I love / hate the sensation when you try to conceive that it (it including whatever includes "it", ad infinitum) has either existed forever or there was a point before anything existed.
fatnoah 6y ago
>Anyone else had the feeling where you think about the origin of Universe for a long time, it doesn't make any sense and you almost get a panic attack? For whatever reason, it makes more more anxious than it should. The concepts involved are so far removed from my brain's understanding of reality that it makes me uncomfortable.
JamesSwift 6y ago
I think of it as having an "existential crisis". Its not just limited to thinking about the universe for me, but things like eventual death and all those "impossible to understand" topics.
Sevrene 6y ago
For sure, I have experienced similar feelings. Good to know it's not just me. It's kind of like a derealization caused by the thought of how absurd or odd it is that we exist at all.
maze-le 6y ago
It is called existential anxiety, it shows that you are able to contemplate about your own insignificance in contrast to the grand scheme of things (universe, all of existence, etc.). We all have it on one level or another, I used to have it when looking into a dark cloudless night, realizing that all of the little dots I can see out there could technically be orbited by another planet that bears life, inhabited by millions or billions of other lifeforms that could be able to feel and think. Usually it is nothing to worry about, except when you get obsessed by it and it starts to control aspects of your life because you build a worldview around it or try hard to avoid it or explain it away: then it is called an existential crisis. But what it really means is that the mind gets overwhelmed by the fact that the universe is orders of magnitudes more complex than what the self has ever encountered in our daily lifes. Our brains have evolved so that bipedal apes that migrated from forests into the steppes can survive and cooperate in groups. It was never meant to be confronted by questions of this dimension, but yet here we are. You can make your peace with it, and embrace it. It can also be a source of endless curiosity, spirituality and creativity.

caiobegotti 6y ago

I have never heard about Big Bounce before, honestly, but the illustration at the top of the article basically made sense in a heart beat and I'm impressed how simple yet how much of the idea it conveys, apparently, correctly. Kudos to the visual artist, usually these scientific illustrations used to explain a weird or novel idea are over the top.

alchemism 6y ago
I vaguely recall hearing of this from a different field of study. https://www.cs.ubc.ca/~goyal/age_of_universe.php https://www.cs.ubc.ca/~goyal/age_of_universe.php

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JadoJodo 6y ago

Sir Roger Penrose and Dr William Lane Craig had an interesting discussion[0] that included him talking about the Big Bounce (around the 50-minute mark). [0] https://youtu.be/9wLtCqm72-Y https://youtu.be/9wLtCqm72-Y

monktastic1 6y ago

Many comments here address an important issue: the human mind has a hard time making sense of both an eternally existing universe, as well as something-from-nothing. But most of the issues stem from presupposing physicalism. It's understood even by staunch physicalists that choosing this metaphysics is ultimately arbitrary[1]. There's another way to approach all this. Start by asking: what's the one thing I know for certain? It's hard to say any more than it certainly seems like something is happening. Investigate this sheer fact of "seeming." See what the seeming is like before you apply any metaphysics on top of it. What happens when you do this extremely precisely? Suppose that the correct metaphysics is that you are ultimately the primordial ground of being, that (paradoxically) weaves itself into apparent realities. What we think of as physical reality is just one instance. It transcends parameters like time and causality, but can give rise to them of its own will. Being the primordial ground of being, nothing logically prevents you from knowing this ultimate truth directly and unequivocally (unlike if you were really just a human). As it so happens, the preceding paragraph describes how you would (re)arrive at this knowing. Or at least, that's what's suggested by various mystical traditions. As far as I can tell, there's definitely something to it. [1] "There is no way to distinguish between the scenarios by collecting new data. What we’re left with is our choice of prior credences. We’re allowed to pick priors however we want. [...] We have every right to give high credence to views of the world that are productive and fruitful." —Sean Carroll, The Big Picture (p.91)

cloudking 6y ago

There's some interesting theories about what was happening before the big bang in the Joe Rogan interview with Brian Greene https://youtu.be/FHAA_1Guxlo https://youtu.be/FHAA_1Guxlo

Razengan 6y ago

Most human questions about the origin of things assume that the default state must be Nothing. Why can't it be Everything? i.e., instead of imagining the Universe as a white dot on a black canvas, how about thinking of it as a black dot on a white background?