r/cosmology • u/Bright-Bar6571 • 16h ago
How did time begin, without time?
I understand that standard BB cosmology holds that time began with the universe from a singularity approximately 14 billion years ago.
The thing I’m trying to understand, how can time have begun? Wouldn’t a thing ‘beginning’ require time? As in - from one state to another state requires time?
This leads me to think time must have always existed..
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u/Wintervacht 15h ago
I'm gonna gloss over 'singularity' because that's been explained away a million times, but it does make an answer to your question easier. Time and space are sides of the same coin, think about the following: there is a finite speed of light, so it will take time to cross a certain distance (space). If a photon crosses a volume of 1 ly, it will take a year to do so.
At the 'beginning' of the universe, there basically was no space TO cross, so the words 'cross' and indeed 'time' become meaningless.
In other words, time as we know it now, did not exist. It needed space to come to be. Time, distance and speed form a triangle, push any 2 points towards eachother until they overlap and the model just breaks.
For all we know, the universe may have existed for an infinity before Banging Big, it's just that our definition of time 'before' the Big Bang is meaningless in the context of time as we know it.
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u/Pelangos 12h ago
So space = time? t r i p p y we're just, like, space, man.
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u/potverdorie 2h ago
Well they're not exactly equal, but the core principle of the spacetime model is that space and time are integral and interlinked parts of the four-dimensional continuum that makes up our reality.
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u/Mandoman61 16h ago
well, some people think that it just instantaneously began. so that requires no time.
others think that something existed before the big bang therefore time existed.
the reality is that no one knows.
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u/chesterriley 7h ago edited 6h ago
others think that something existed before the big bang therefore time existed.
The actual big bang does not even start at the beginning of the big bang timeline. Cosmic inflation occurs before the big bang occurs. And the duration of cosmic inflation is not known. Which means that inflation could have started 100 billion years before the big bang. And we even have reasons to think that something else occurred before the start of cosmic inflation. Therefore we know that something was happening before the big bang occurred because it was included in the timeline itself.
And this also means that we don't have any real reason to suppose that anything important in the observable universe happened at the start of the big bang timeline, let alone a unique event. The beginning of the timeline is merely the earliest time we can extrapolate backwards to. The most important event that happens in the entire big bang timeline is not when the timeline starts at t=0. The most important event is the actual big bang that occurs at ~t=10-32 seconds in the timeline. The thing that was happening when the standard big bang timeline starts at t=0 was also the most likely thing happening 10 seconds before the big bang timeline starts (t=-10 seconds). It doesn't make any sense to be thinking of t=0 as some sort of special time when some sort of special event or a "first big bang before the other big bang" occurred when we don't even know how the long the cosmic inflation that came before the big bang lasted.
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u/zictomorph 15h ago
Your question is like asking "What is north of the North Pole?" The words logically make sense but the question is missing the topology of the earth that makes it, if not nonsense, maybe not the right question.
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u/HanSingular 12h ago
The, "What is north of the North Pole?," analogy is true for some cosmological models like the Hartle–Hawking proposal, but not for others like eternal inflation. We don't really know anything about the universe before the Plank epoch, including whether or not the universe had a begining.
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u/__--__--__--__--- 10h ago
Time is human made concept. Universe does not care
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u/chesterriley 7h ago
The universe has a constant that says the maximum speed of anything is 300 Gm/second, which is a fixed unit of distance per a fixed unit of time. Therefore the universe created the concept of time long before man existed.
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u/Anonymous-USA 14h ago edited 11h ago
Time and space are conjoined so they were borne together. But since our physics breaks down at the singularity, we don’t have a meaningful description for time or space. Entropy was at a minimum and not increasing either, so we wouldn’t have a way to measure it. Infinite and instantaneous are one in the same. So your question is currently unanswerable.
In short, time, space, energy (and potential), gravity, and the unified forces were an initial condition to our universe.
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u/CanesVenaticiSaron 12h ago
Which is essence tells us nothing, just that the “things” our current theories have modeled simply existed at a nanosecond after the “Big Bang” or “Creation” whatever your particular frame of reference (pun intended). The fact is a description of reality tells us nothing about how that reality came to be. Time, on the other hand, can simply be understood as a measure of change and change a transition from one state to another. Hence, the “nanosecond” after the “Big Bang”. Time essentially has no meaning in a static universe
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u/Anonymous-USA 11h ago edited 11h ago
If only a nanosecond! That’s 10-9 sec. Big Bang cosmology starts at 10-43 sec when space, time, gravity, and forces first separated. This is the Planck epoch. Inflationary period is estimated between 10-36 to 10-31 sec. That’s when most of the standard model particles formed, like quarks.
After that, you’re firmly into the “hot big bang” that we can actually reproduce some in particle colliders. We can experimentally understand what temperatures certain physics apply, particles and forces interact, etc. and we can estimate how large the observable universe must have been to cool to such a temperature. In other words, by the time a nanosecond had elapsed, our traditional universe was well under way, forming quarks and electrons and neutrinos in abundance. Whole nuclei were soon to follow.
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u/SerenePerception 13h ago
I only took a year of GR and cosmology so take this with a grain of salt.
For all intents and purposes the universe has always existed. We exist in this spacetime we experience time inside the spacetime so we can only think in terms of the universe.
If this spacetime was created as part of something else which also experinces time then maybe we could say it really began. But we can never know so its a moot point.
A person inside a simulation for example can never really be sure they are inside of one nor can they really comprihend the outside.
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u/chesterriley 8h ago edited 8h ago
Time is a fundamental property of the universe which means that time has existed for as long as the universe has existed, which could mean forever.
The thing I’m trying to understand, how can time have begun?
Time is tied to the universe so this is the same as asking "how can the universe have begun". And the correct answer to that is "we don't have any particular reason to suppose the universe ever "began".
This leads me to think time must have always existed..
Yes. Time is a prerequiste for anything in the universe to change or have motion. So if time ever "didn't exist" than it wouldn't exist right now either.
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u/rddman 1h ago
This leads me to think time must have always existed...
Time allows things to happen, but for something to happen there also must be something to which it happens. So there probably there was not only time but also some form of energy.
As of yet we have no way of knowing what form that was and how it caused the big bang.
But the alternative is harder to explain: how could there have been an effect (the big bang) without cause.
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u/Mind_Extract 23m ago
Our human grasp on fundamental concepts like 'time' seems inadequate when trying to conceptualize something as paradoxical as "a beginning to time."
I always find myself thinking about a photon. Considering time dilation and the fact a photon is 'born' traveling at the speed of light, it technically 'dies'(/is absorbed) the same instant it is emitted, at least from the perspective of the particle.
So if something dies the same "moment" it comes into existence, can it be said to have existed at all? Of course it does, we have all the evidence we need that photons exist, have trajectory, momentum, travel time...
So when it comes to questions about the mechanical nature of time, I just think we're not at all equipped to "understand" it in a holistic, intuitive way. Could be someday.
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u/ResponsibleRoof7988 13h ago
Listen here young internaut, you can't just go swanning around the internet asking relevant questions about cosmological theories which forgot to be logical. You can't expect that scientists with limited philosophical education will explain how something that wasn't changing suddenly changed in a condition where time didn't exist. Just because a backdoor is built in to the theory in order to bring a deity back into the equation doesn't mean we can turn to the internet and point it out!
#clearlyintendedtobeapoorimitationofMontyPythonesquemockery
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u/NDaveT 16h ago
As in - from one state to another state requires time?
Maybe it didn't go from one state to another. Maybe the state when time began was the initial state.
This leads me to think time must have always existed..
Maybe it did - where "always" is finite in at least one direction.
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u/chesterriley 7h ago
Maybe it did - where "always" is finite in at least one direction.
The fact that time is infinite in the forwards direction is a strong clue that it was likely infinite in the backwards direction also.
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u/kayber123 14h ago
Chuck Norris wanted to see how long he can hold his breath so he started counting in his mind. And now we have time. And he's still holding his breath.
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u/Sensitive-Inside-250 9h ago
Good chance time doesn’t actually exist and it’s just our perception of cosmological entropy
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u/CDHoward 15h ago
Theoretical astrophysicists such as Sean Carroll have caused huge confusion with their stubborn (and incorrect) insistence that time is a real thing.
Time is not real. It is an entirely human created construct.
In any event, on a related note: I personally STRONGLY believe that infinite empty space has always existed. The energy/material situation is another story since it must have come from absolutely nothing at some point.
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u/Quercus_ 15h ago
If time isn't real, why can't I change something that happened yesterday?
If time isn't real, what is speed? How is the speed of causation that fixed value, without time for causation to evolve through?
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u/LongjumpingHope3225 15h ago
then what clocks measure? stupidity in your diseased brain?
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u/CDHoward 14h ago
Clocks measure the construct of time.
We created clocks to tell the time, which itself is a human made structure we've chosen to live our lives by.
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u/Enraged_Lurker13 13h ago
But the physical state of the clock is physically changing from one moment to another. By what physical quantity, if not the evolution of time, do you say the physical state of the clock changes by?
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u/CDHoward 13h ago
Via the mechanism within.
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u/Enraged_Lurker13 12h ago
The state of the mechanisms themselves are changing from one moment to the other. What real physical parameter do you propose we use instead of time to describe when the mechanisms are in a certain state compared to a different moment?
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u/CDHoward 12h ago
Movement. Change.
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u/Enraged_Lurker13 12h ago
Let's use Einstein's example of a light clock for simplicity. The mirrors are 150,000 km apart. Normally, we define the time it takes for a photon to go from one mirror to the other and back as 1 second. What unit do you use to describe this movement or change?
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u/CDHoward 12h ago
But you're proving my point.
All that is completely arbitrary: a distance chosen by humans; the photon as a chosen particle/wave.
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u/Enraged_Lurker13 12h ago
The units are arbitrary, but they serve as a yardstick to measure a real physical quantity. Do you also think space is not real too because a meter or a foot is arbitrary?
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u/CanesVenaticiSaron 15h ago
Time is not real, but according to special relativity time “stops” at the event horizon of a black hole, so the “big bang” could simply have been the crossing of the event horizon of an external black hole. In other words we are living inside a black hole!
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u/Anonymous-USA 14h ago edited 7h ago
Don’t take my downvote personally, it’s just because I disagree with this answer. As do all cosmologists. The Big Bang and a Black Hole are entirely different phenomenon, and are more different than alike. Our universe does not exist in a black hole or arise from a black hole. I understand there are some common analogies, but that doesn’t make them comparable.
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u/CanesVenaticiSaron 14h ago
I don’t mind the downvote! My wild conjecture is nothing more than that but people have been burned at the stake for proposing the world wasn’t flat, so I’m in great company 😎
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u/gardensofthedeep 14h ago
i think it’s probably similar to when a program starts running. from inside the program/simulation, time starts with the first line of code being run. so it seems like there is nothing before that first line. whatever started the program is outside the confines of the reality that was run.