May 25, 2025 08:01 PM
https://bigthink.com/starts-with-a-bang/...-big-bang/
EXCERPTS: . . . And yet, when cosmologists speak about what happened before the Big Bang — i.e., during the period of cosmic inflation that set up and preceded the Big Bang — time remains present. So why would Hawking state that time itself must come to a stop? Why would he claim that you can’t get to a time before the Big Bang? And why would he state that there was no time at all before the Big Bang?
I hate to say it, but this is because Stephen Hawking is not talking about the Big Bang as we conventionally understand it: the hot, dense, uniformly filled with matter-and-radiation, rapidly expanding state of the early Universe that we associate with the onset of the Big Bang. He’s not talking about the state of cosmic inflation that preceded and set up the hot Big Bang, either. Instead, Hawking is talking about a very old notion of the Big Bang that is currently a very hotly debated topic (and an active area of research) within theoretical cosmology: the idea that “the Big Bang” means the origin of space and time itself.
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This is something that makes sense if you put yourself in the mindset of someone who was learning about the Universe back when Hawking was learning about the Universe: in the 1950s, 1960s, and 1970s [...] This idea, of a singularity, goes back to Lemaître and Gamow, who gave it poetic names such as “the primeval atom” and “the cosmic egg.”
[...] And this is true in general relativity: a singularity truly does define a set of conditions where time and space themselves do indeed break down. Remember, according to our best understanding of physics — which is general relativity for the structure of space and time and what we experience as the force of gravity, along with quantum field theory as the governing rules for particles, antiparticles, and the electromagnetic and the nuclear forces — there are limits to ... and if you go past those limits, the quantities you compute will no longer make physical sense.
[...] When Hawking talks about “the Big Bang,” he uses it in this antiquated sense: assuming that the Universe did indeed begin with a singularity, and that singularity marks the birth of space and time, and therefore there was an “event” of ultimate creation that created space, time, and all the matter and radiation within it...
[...] But that “picture” for the origin of our Universe is more than 40 years out of date, at present. The hot Big Bang — or the notion that the Universe emerged by expanding and cooling from an early hot, dense, nearly-perfectly-uniform state — is no longer considered to be the beginning of the Universe, but rather only arose as the aftermath of an earlier period that preceded it and set it up: a period of cosmic inflation...
[...] From whatever pre-existing state started it, inflation predicts that a series of independent universes will be spawned as inflation continues, with each one being completely disconnected from every other one, separated by more inflating space. One of these “bubbles,” where inflation ended, gave birth to our Universe some 13.8 billion years ago...
[...] You can argue “well, inflation is timeless in the sense that we can only probe the final ~10-32 seconds of it, but [...] time still passes during the inflationary period; the inflationary period was finite, indicating that there was “time” before it as well; and that we have practically no constraints on the pre-inflationary state, meaning that we don’t know whether inflation emerged from an ultimately singular or non-singular state.
Although many still operate under the assumption that there was a singularity from which space and time themselves did emerge — and hence, a “timeless” initial state, after all — the truth is that we have no way to access any knowledge or information about that state [...] Time proceeds as normal during the hot Big Bang and afterward, but also during the inflationary period, and also during whatever period preceded the inflationary one. Whether there was a “timeless” state before that is possible, and some would argue even likely, but it remains unproven.
The possible emergence of time itself is a fun aspect of nature to consider, but we have to do it responsibly: with full knowledge that when even very smart people talk about a “timeless” state, they’re not talking about inflation; they’re talking about the creation/emergence of space and time itself. That may have indeed happened, but if it did, it’s not just before the Big Bang. It’s before the hot Big Bang, before inflation, and before whatever it is that came before even that.. (MORE - missing details)
EXCERPTS: . . . And yet, when cosmologists speak about what happened before the Big Bang — i.e., during the period of cosmic inflation that set up and preceded the Big Bang — time remains present. So why would Hawking state that time itself must come to a stop? Why would he claim that you can’t get to a time before the Big Bang? And why would he state that there was no time at all before the Big Bang?
I hate to say it, but this is because Stephen Hawking is not talking about the Big Bang as we conventionally understand it: the hot, dense, uniformly filled with matter-and-radiation, rapidly expanding state of the early Universe that we associate with the onset of the Big Bang. He’s not talking about the state of cosmic inflation that preceded and set up the hot Big Bang, either. Instead, Hawking is talking about a very old notion of the Big Bang that is currently a very hotly debated topic (and an active area of research) within theoretical cosmology: the idea that “the Big Bang” means the origin of space and time itself.
penzias wilson cmb holmdel horn antenna
This is something that makes sense if you put yourself in the mindset of someone who was learning about the Universe back when Hawking was learning about the Universe: in the 1950s, 1960s, and 1970s [...] This idea, of a singularity, goes back to Lemaître and Gamow, who gave it poetic names such as “the primeval atom” and “the cosmic egg.”
[...] And this is true in general relativity: a singularity truly does define a set of conditions where time and space themselves do indeed break down. Remember, according to our best understanding of physics — which is general relativity for the structure of space and time and what we experience as the force of gravity, along with quantum field theory as the governing rules for particles, antiparticles, and the electromagnetic and the nuclear forces — there are limits to ... and if you go past those limits, the quantities you compute will no longer make physical sense.
[...] When Hawking talks about “the Big Bang,” he uses it in this antiquated sense: assuming that the Universe did indeed begin with a singularity, and that singularity marks the birth of space and time, and therefore there was an “event” of ultimate creation that created space, time, and all the matter and radiation within it...
[...] But that “picture” for the origin of our Universe is more than 40 years out of date, at present. The hot Big Bang — or the notion that the Universe emerged by expanding and cooling from an early hot, dense, nearly-perfectly-uniform state — is no longer considered to be the beginning of the Universe, but rather only arose as the aftermath of an earlier period that preceded it and set it up: a period of cosmic inflation...
[...] From whatever pre-existing state started it, inflation predicts that a series of independent universes will be spawned as inflation continues, with each one being completely disconnected from every other one, separated by more inflating space. One of these “bubbles,” where inflation ended, gave birth to our Universe some 13.8 billion years ago...
[...] You can argue “well, inflation is timeless in the sense that we can only probe the final ~10-32 seconds of it, but [...] time still passes during the inflationary period; the inflationary period was finite, indicating that there was “time” before it as well; and that we have practically no constraints on the pre-inflationary state, meaning that we don’t know whether inflation emerged from an ultimately singular or non-singular state.
Although many still operate under the assumption that there was a singularity from which space and time themselves did emerge — and hence, a “timeless” initial state, after all — the truth is that we have no way to access any knowledge or information about that state [...] Time proceeds as normal during the hot Big Bang and afterward, but also during the inflationary period, and also during whatever period preceded the inflationary one. Whether there was a “timeless” state before that is possible, and some would argue even likely, but it remains unproven.
The possible emergence of time itself is a fun aspect of nature to consider, but we have to do it responsibly: with full knowledge that when even very smart people talk about a “timeless” state, they’re not talking about inflation; they’re talking about the creation/emergence of space and time itself. That may have indeed happened, but if it did, it’s not just before the Big Bang. It’s before the hot Big Bang, before inflation, and before whatever it is that came before even that.. (MORE - missing details)
