5 ms·

Physicists simulate critical 'reheating' period that kickstarted the Big Bang

29 points by dnetesn 7y ago

Thorentis 7y ago
The more we learn about the Big Bang and the way it may have happened, the less intriguing, or put another way, the less satisfying a theory it becomes for me. It just makes me more curious about what happened before the Big Bang, or at least, it makes what happened before the Big Bang seem more important to understanding the origins of the universe.
- sysbin 7y ago
  One possibility is infinite Big Bangs. Universe expands until it reaches a point where it begins retracting, then reaches point where big bang happens and then it repeats all over again for infinity. Basically can result in our lives being repeated for infinity. All the events reoccur to make earth exactly as before and where all forces proceed forward the same as before. Similar the forces could occur slightly different but if this is happening for infinity. I'm assuming irritations would repeat.
  - reading-at-work 7y ago
    This activates my existential dread pretty hard. The idea of never existing again after I die and there being no afterlife is pretty scary by itself, but the idea of this life repeating infinitely is somehow even worse. Though I guess each individual experience in the infinite continuum would be isolated so it's not like I'm remembering all of my past lives, in which case I guess it doesn't matter either way. It's a weird mental rabbit hole to go down.
    - sysbin 7y ago
      You would exist again and after you die from that theory for infinity. I'm confused how you associate existential dread with it?
    - imtringued 7y ago
      I've thought about these things a lot. There are so many logical problems with an afterlife. Heaven/Utopia doesn't make sense because it would have to be based on your current life. (do you arrive old or young in heaven etc) Reincarnation is problematic because you would have to stand in a queue while waiting for your soul to be assigned to a new body. My theory with the least amount of logical flaws is assuming that there is a global soul which is reading the "standard input" from all philosophical zombies simultaneously or it only selects one philosophical zombie. None of this really matters because only depressed people worry about the "meaning" of life, primarily because they have been denied all other sources of "meaning" and therefore cling to the one thing everyone (including themselves) has: a life. It's only human to grow attached to things and our lives are our most priced possessions after all.
      - sysbin 7y ago
        > My theory with the least amount of logical flaws is assuming that there is a global soul which is reading the "standard input" from all philosophical zombies simultaneously or it only selects one philosophical zombie. Can you expand on the only selects one philosophical zombie? I don't really understand what you're attempting to express. I think all people "think" about existence at some point. Maybe sad people think about it more than others.
    - gremlinsinc 7y ago
      Except this could be reincarnation to an extent.. Hell what if the Mandela effect isn't being zapped into a new parallel universe because our planet was destroyed in the early 90's. What if our planet was destroyed...somehow our 'data' was backed up, then billions of years passed, then the big bang happened, then earth came back and we basically came to being in a slightly altered timeline? I'm an exmormon/agnostic that believes in afterlife just not deity. I don't believe 100% just that it's possible, but that there's no pre-requisites to get there and no conditions. Mainly energy that is our 'soul' lives on in some form, or maybe there is quantum imortality where you keep being reborn in 'yourself' in another parallel universe and you retain some memories/essence of your former self, but are always trying to become better. You or someone else could have a child in one universe, not the next. So in some universes you're never even born, some you are, and some people may be born for the first time ever, thus the whole old-soul/new-soul thing. Who's to say though it's not the same universe just it swings back and forth like a pendulum and when it's in the low arc it's our small time here, when it's at the high mark it's sucked back into a dense ball, then it explodes again on the downward arc... I just can't buy that an all-knowing all-powerful being created everything (if anything it was an idiot who blew up all space/time toying with technology they didn't fully understand). This same being is petty, manipulative, and narcissistic and demands our fealty, our faith, our worship else we be cast into a pit of fire. Sounds like something Donald Trump would say to pretty much any Democrat or anyone who doesn't think his shit is made of gold.
      - sysbin 7y ago
        I do toy with that idea of how our thoughts are somehow stored elsewhere and contrary of our memories just being gone at death. I'm trying to make the concept work with the idea of eternal reoccurrence but it's hard to think of a good idea. I'm agnostic as well but I don't rule out the concept of a deity. There could be heaven & hell and even when it's just double predestination. A deity doesn't have to please the whims of what we think of as fair. Anyhow, I could even see eternal reoccurrence working with a deity altering the simulation as it pleases. Btw, simulation is just a word and one I chose to express what we live.
        gremlinsinc 7y ago
    - Scarblac 7y ago
      I have the opposite reaction. I find the idea that we could cause almost all life on Earth to die, while the planet may not have enough billions of years left to evolve something the current biosphere again to be deeply disturbing. We don't even know if other life exists. If universes get reborn ad infinitum, nothing is that final.
- codeulike 7y ago
  Hawking and Hartle said the universe doesn't have a boundary, much like Earth's rounded surface lacks an edge. Hawking likened his no-boundary proposal (aka Stephen-hawking-Hartle state) for the universe to traveling southward until you reach the South Pole. When you reach the South Pole, the term "south" loses its meaning. The same idea is applied to time before the Big Bang -- once you trace back the universe to its beginning, the concept of time (as we define it, at least) becomes obsolete. https://science.howstuffworks.com/dictionary/famous-scientists/physicists/stephen-hawking3.htm https://science.howstuffworks.com/dictionary/famous-scientis...
- imtringued 7y ago
  The one big problem with any theory that tells me that the universe has started and will end is that if this is true then why hasn't it ended yet? (the inverse of "Why has it started?") It hasn't ended yet so it makes sense that either space time is static or that there is an infinite chain of big bang like events.
  - Doxin 7y ago
    That seems to run into the anthropological principle.[1] The universe hasn't ended yet because if it had we wouldn't be able to observe it. Of course that begs the question why humans are a thing that happened now and not some other time, but that's a much less interesting question in my opinion. Humans happened by some fluke, a prerequisite for that is the universe existing.
- acqq 7y ago
  https://medium.com/starts-with-a-bang/what-happened-before-the-big-bang-ef36f2bb2ad1 https://medium.com/starts-with-a-bang/what-happened-before-t... "we not only don’t know whether there was a singularity at some point in the very distant, pre-inflation past, or whether inflation was truly eternal, we don’t even know whether inflation occurred for less than a yoctosecond or more than the present age of the (post-Big Bang) Universe! Our prospects for finding out, furthermore, are quite dim, as — by its very nature — practically every model of cosmic inflation wipes out any information about the Universe that existed prior to the last billionth-of-a-yoctosecond before inflation ended, and our Universe began." "It may have been eternal to the past, there may have been a true singularity before it, or there may have been something else; as far as our current observations go, we haven’t even conceived of a way we could possibly know."
mhartl 7y ago
The article appears to be confusingly written, making reference to a time “before” the Big Bang: Just before the Big Bang launched the universe onto its ever-expanding course, physicists believe, there was another, more explosive phase of the early universe at play: cosmic inflation, which lasted less than a trillionth of a second. But cosmic inflation was part of the Big Bang, not something that happened “before” it. According to the current understanding, the Big Bang included the beginning of time itself—in more technical terms, the Universe has no boundary in time (or space)—so asking what happened “before” the Big Bang is akin to asking what’s north of the North Pole.
- contravariant 7y ago
  The term 'boundary' has a specific mathematical meaning that may or not be appropriate. In particular a ball has a boundary (although a sphere doesn't). The universe may or may not have a boundary at the big bang. Most straightforward theories seem to suggest it does have one. I believe Hawking has a rather complicated theory where it may not have one, but that involves adding an extra time dimension, which is a bit iffy. Regardless, even if an infinite (in space) universe simply sprang into existence at a certain moment, that still doesn't mean it makes sense to ask what happened before. It makes sense to ask what happens at the boundary, but there is not necessarily a before to ask about.
  - PhasmaFelis 7y ago
    I'm curious about the technical difference between a ball and a sphere.
    - xelxebar 7y ago
      Poster is probably using the terms how they are used in Analysis. A sphere is just the surface, i.e. the set of points equidistant from some center. A ball is the entire volume enclosed by said sphere.
      - PhasmaFelis 7y ago
AnimalMuppet 7y ago
> The team found this extreme transformation would have been even faster and more efficient if quantum effects modified the way that matter responded to gravity at very high energies, deviating from the way Einstein's theory of general relativity predicts matter and gravity should interact. > all with known physics Um... I'd like to see their "known" theory of quantum-modified general relativity...
- QuesnayJr 7y ago
  Isn't there a linearized gravity that you can quantize? Like in these lecture notes: http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pdf http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pd...?
  - AnimalMuppet 7y ago
    I think so. But can you (validly) linearize gravity in the circumstances that were thought to exist at the time we're talking about?
    - QuesnayJr 7y ago
      I tried looking at the paper and some of its references, and answering this question is well outside my area of competence.
ivalm 7y ago
There is a bit of conflation of "observable universe" with "universe". The "observable universe" (as observed now) would be absolutely tiny, but the overall universe may be large even pre inflation, we simply don't see anything outside our tiny cone.

29 points by dnetesn 7y ago

The more we learn about the Big Bang and the way it may have happened, the less intriguing, or put another way, the less satisfying a theory it becomes for me. It just makes me more curious about what happened before the Big Bang, or at least, it makes what happened before the Big Bang seem more important to understanding the origins of the universe.

sysbin 7y ago
One possibility is infinite Big Bangs. Universe expands until it reaches a point where it begins retracting, then reaches point where big bang happens and then it repeats all over again for infinity. Basically can result in our lives being repeated for infinity. All the events reoccur to make earth exactly as before and where all forces proceed forward the same as before. Similar the forces could occur slightly different but if this is happening for infinity. I'm assuming irritations would repeat.
- reading-at-work 7y ago
  This activates my existential dread pretty hard. The idea of never existing again after I die and there being no afterlife is pretty scary by itself, but the idea of this life repeating infinitely is somehow even worse. Though I guess each individual experience in the infinite continuum would be isolated so it's not like I'm remembering all of my past lives, in which case I guess it doesn't matter either way. It's a weird mental rabbit hole to go down.
  - sysbin 7y ago
    You would exist again and after you die from that theory for infinity. I'm confused how you associate existential dread with it?
  - imtringued 7y ago
    I've thought about these things a lot. There are so many logical problems with an afterlife. Heaven/Utopia doesn't make sense because it would have to be based on your current life. (do you arrive old or young in heaven etc) Reincarnation is problematic because you would have to stand in a queue while waiting for your soul to be assigned to a new body. My theory with the least amount of logical flaws is assuming that there is a global soul which is reading the "standard input" from all philosophical zombies simultaneously or it only selects one philosophical zombie. None of this really matters because only depressed people worry about the "meaning" of life, primarily because they have been denied all other sources of "meaning" and therefore cling to the one thing everyone (including themselves) has: a life. It's only human to grow attached to things and our lives are our most priced possessions after all.
    - sysbin 7y ago
      > My theory with the least amount of logical flaws is assuming that there is a global soul which is reading the "standard input" from all philosophical zombies simultaneously or it only selects one philosophical zombie. Can you expand on the only selects one philosophical zombie? I don't really understand what you're attempting to express. I think all people "think" about existence at some point. Maybe sad people think about it more than others.
  - gremlinsinc 7y ago
    Except this could be reincarnation to an extent.. Hell what if the Mandela effect isn't being zapped into a new parallel universe because our planet was destroyed in the early 90's. What if our planet was destroyed...somehow our 'data' was backed up, then billions of years passed, then the big bang happened, then earth came back and we basically came to being in a slightly altered timeline? I'm an exmormon/agnostic that believes in afterlife just not deity. I don't believe 100% just that it's possible, but that there's no pre-requisites to get there and no conditions. Mainly energy that is our 'soul' lives on in some form, or maybe there is quantum imortality where you keep being reborn in 'yourself' in another parallel universe and you retain some memories/essence of your former self, but are always trying to become better. You or someone else could have a child in one universe, not the next. So in some universes you're never even born, some you are, and some people may be born for the first time ever, thus the whole old-soul/new-soul thing. Who's to say though it's not the same universe just it swings back and forth like a pendulum and when it's in the low arc it's our small time here, when it's at the high mark it's sucked back into a dense ball, then it explodes again on the downward arc... I just can't buy that an all-knowing all-powerful being created everything (if anything it was an idiot who blew up all space/time toying with technology they didn't fully understand). This same being is petty, manipulative, and narcissistic and demands our fealty, our faith, our worship else we be cast into a pit of fire. Sounds like something Donald Trump would say to pretty much any Democrat or anyone who doesn't think his shit is made of gold.
    - sysbin 7y ago
      I do toy with that idea of how our thoughts are somehow stored elsewhere and contrary of our memories just being gone at death. I'm trying to make the concept work with the idea of eternal reoccurrence but it's hard to think of a good idea. I'm agnostic as well but I don't rule out the concept of a deity. There could be heaven & hell and even when it's just double predestination. A deity doesn't have to please the whims of what we think of as fair. Anyhow, I could even see eternal reoccurrence working with a deity altering the simulation as it pleases. Btw, simulation is just a word and one I chose to express what we live.
      - gremlinsinc 7y ago
  - Scarblac 7y ago
    I have the opposite reaction. I find the idea that we could cause almost all life on Earth to die, while the planet may not have enough billions of years left to evolve something the current biosphere again to be deeply disturbing. We don't even know if other life exists. If universes get reborn ad infinitum, nothing is that final.
codeulike 7y ago
Hawking and Hartle said the universe doesn't have a boundary, much like Earth's rounded surface lacks an edge. Hawking likened his no-boundary proposal (aka Stephen-hawking-Hartle state) for the universe to traveling southward until you reach the South Pole. When you reach the South Pole, the term "south" loses its meaning. The same idea is applied to time before the Big Bang -- once you trace back the universe to its beginning, the concept of time (as we define it, at least) becomes obsolete. https://science.howstuffworks.com/dictionary/famous-scientists/physicists/stephen-hawking3.htm https://science.howstuffworks.com/dictionary/famous-scientis...
imtringued 7y ago
The one big problem with any theory that tells me that the universe has started and will end is that if this is true then why hasn't it ended yet? (the inverse of "Why has it started?") It hasn't ended yet so it makes sense that either space time is static or that there is an infinite chain of big bang like events.
- Doxin 7y ago
  That seems to run into the anthropological principle.[1] The universe hasn't ended yet because if it had we wouldn't be able to observe it. Of course that begs the question why humans are a thing that happened now and not some other time, but that's a much less interesting question in my opinion. Humans happened by some fluke, a prerequisite for that is the universe existing.
acqq 7y ago
https://medium.com/starts-with-a-bang/what-happened-before-the-big-bang-ef36f2bb2ad1 https://medium.com/starts-with-a-bang/what-happened-before-t... "we not only don’t know whether there was a singularity at some point in the very distant, pre-inflation past, or whether inflation was truly eternal, we don’t even know whether inflation occurred for less than a yoctosecond or more than the present age of the (post-Big Bang) Universe! Our prospects for finding out, furthermore, are quite dim, as — by its very nature — practically every model of cosmic inflation wipes out any information about the Universe that existed prior to the last billionth-of-a-yoctosecond before inflation ended, and our Universe began." "It may have been eternal to the past, there may have been a true singularity before it, or there may have been something else; as far as our current observations go, we haven’t even conceived of a way we could possibly know."

mhartl 7y ago

The article appears to be confusingly written, making reference to a time “before” the Big Bang: Just before the Big Bang launched the universe onto its ever-expanding course, physicists believe, there was another, more explosive phase of the early universe at play: cosmic inflation, which lasted less than a trillionth of a second. But cosmic inflation was part of the Big Bang, not something that happened “before” it. According to the current understanding, the Big Bang included the beginning of time itself—in more technical terms, the Universe has no boundary in time (or space)—so asking what happened “before” the Big Bang is akin to asking what’s north of the North Pole.

contravariant 7y ago
The term 'boundary' has a specific mathematical meaning that may or not be appropriate. In particular a ball has a boundary (although a sphere doesn't). The universe may or may not have a boundary at the big bang. Most straightforward theories seem to suggest it does have one. I believe Hawking has a rather complicated theory where it may not have one, but that involves adding an extra time dimension, which is a bit iffy. Regardless, even if an infinite (in space) universe simply sprang into existence at a certain moment, that still doesn't mean it makes sense to ask what happened before. It makes sense to ask what happens at the boundary, but there is not necessarily a before to ask about.
- PhasmaFelis 7y ago
  I'm curious about the technical difference between a ball and a sphere.
  - xelxebar 7y ago
    Poster is probably using the terms how they are used in Analysis. A sphere is just the surface, i.e. the set of points equidistant from some center. A ball is the entire volume enclosed by said sphere.
    - PhasmaFelis 7y ago

AnimalMuppet 7y ago

> The team found this extreme transformation would have been even faster and more efficient if quantum effects modified the way that matter responded to gravity at very high energies, deviating from the way Einstein's theory of general relativity predicts matter and gravity should interact. > all with known physics Um... I'd like to see their "known" theory of quantum-modified general relativity...

QuesnayJr 7y ago
Isn't there a linearized gravity that you can quantize? Like in these lecture notes: http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pdf http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pd...?
- AnimalMuppet 7y ago
  I think so. But can you (validly) linearize gravity in the circumstances that were thought to exist at the time we're talking about?
  - QuesnayJr 7y ago
    I tried looking at the paper and some of its references, and answering this question is well outside my area of competence.

ivalm 7y ago

There is a bit of conflation of "observable universe" with "universe". The "observable universe" (as observed now) would be absolutely tiny, but the overall universe may be large even pre inflation, we simply don't see anything outside our tiny cone.