How did the big bang have time to happen?

[CumbrianGadgey]

From what I understand, the universe was supposed to have all of its energy and matter condensed into a singularity, just prior to the bang itself.

My first thought was, well if it's a singularity, surely there is no time because it stops at such a point? There is also no space, time or matter outside it to influence it externally.

If there is no time, then matter or anything else can not so much as move, let alone interact explosively.

It's all well and good saying that we understand the universe from 10^-14 seconds after the bang, it's what happened in the previous 10^-14 seconds that counts!

Maybe I'm missing something and my thinking is too simplistic. Can anyone enlighten me on this? I tried writing to Hawking himself on the subject, but just got an automated reply that he is too busy to answer e-mails.

Cheers.

[Qualia]

From my understanding, in the cosmology Hawking describes, the universe does not have a beginning. This does not mean that time extends infinitely into the past. Rather, that like space, time has no edge. Time, then, for Hawking, seems to be finite but unbounded. He likens the idea of the beginning of the universe to a location on earth like the South Pole, and says to ask “What happened before time began?” is akin to asking “What lies south of the South Pole?” The question has no meaning. Because of this, he writes, the universe and all its different quantum histories, is a self-contained object in which scientific laws alone dictate the nature of the various versions of reality. Hence, there is no need to conjure a supernatural creator and no outside intervention is required to make reality what it is.

Along similar lines, if the universe had a beginning, it seems wrong to talk about what happened "before" it began, since most accounts of its beginning entail that time began with the universe. So how can something happen "before" time began?

Another similar argument could be: if there were events or entities in existence before the universe began, then we will never know of them because they occurred outside the limits of the universe, outside the limits of time and space. As we cannot define phenomenon outside these limits, to describe such phenomenon is futile. What happened before time and space can never be put into words. Of course, this fact does not rule out any particular phenomenon that could have started the universe, but it does prevent us from ever knowing, nay, imagining what that phenomenon is.

[ollypenrice]

Excellent answer from Qualia.

I'd just add, though, that I think it is perfectly valid to ask what happened behind 10^-43 second. Just don't expect to get an answer! The great thing about science, and the thing that sets it apart from lesser activities like 'asserting,' is that it is very good at knowing what it doesn't know. And it knows, therefore, that prior to the Planck Time it is like Manuel of Fawlty Towers in knowing nothing!

Olly

[spurius]

Also if nothing, not even darkness itself can escape from a black hole then just imagine all the block holes in the entire universe all merged together. Then on top of these, all the matter in stars, planets, asteroids etc also mixed in. So how was it possible in the first place that stuff could escape from this point of singularity when light cannot escape from a lousy black hole? 

[acey]

The Big Bang is inferred by running backward from present observations (e.g. cosmic microwave background) using known physics (general relativity and quantum theory). The notion that the Big Bang was a "singularity" comes from work by Hawking and Penrose showing that as long as you assume general relativity and quantum theory (along with some other assumptions), the beginning had to be a mathematical singularity. It has always been appreciated that the assumptions might not be valid. Hawking and Hartle proposed "imaginary time" (discussed by Hawking in A Brief History Of Time), so that the singularity would effectively be an accident of co-ordinates, like the north pole of the earth. More generally, it's believed that as you get to very high energy (i.e. very close to the Big Bang), gravity would need to be treated as a quantum effect, i.e. general relativity would no longer apply. String and brane theories are an attempt to deal with quantum gravity - there are other approaches too. The Hartle-Hawking idea came from one of the other (older) approaches.

The scale at which gravity would become a quantum phenomenon is estimated by juggling fundamental constants (Planck's constant, gravitational constant, speed of light), and can be expressed in various ways (thanks to E=mc^2), as "Planck mass", "Planck energy", "Planck length" or "Planck time". The latter is about 5 x 10^(-44) s, so this is taken to be as close to the Big Bang as current physics can take us.

These Wikipedia articles explain it in more detail.

http://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singularity_theorems

http://en.wikipedia.org/wiki/Hartle%E2%80%93Hawking_state

http://en.wikipedia.org/wiki/Planck_time

[jetstream]

Acey,Qualia,excellent information.I love when I've seen interviews with cosmologists on TV and they are asked "illegal" questions and such...some of them have quite good humor.Guth's response..."what banged.what did it bang in and where did it bang?".....that made me laugh.I love Hawkings humor too..

[101nut]

Let me run with this for a moment ...

There is a postulation that black holes can evaporate via Hawking Radiation. This normally relates to spontaneous generation of particulate matter across the event horizon generating apparent "evaporation" of mass but I believe the process can also allow energy evaporation via photon emission ...

There is also a theory where time is 'granular' - time itself is not smooth but almost particulate (for want of a better description). 

Perhaps it would be reasonable to postulate that there is a finite probability that time itself could be created from a "singularity" (or a massless, dimensionless "nothing") via something like the Hawking Radiation mechanism, producing time and anti-time bubbles/particles/granules. The universe as we know it may then be a result of a single, spontaneous "evaporation" event of a time particle from that "nothing". Multiple universes could be postulated by multiple random "evaporation" events ... There would be the necessary creation of a second time granule within the "nothing" as the equivalent anti-particle of time. Quite how time would differ from anti-time, or if it was the same (like photon/anti-photon), would be an interesting question. Perhaps space-time environments are always the same and produced in pairs? Initially time would run frighteningly fast as there would be no gravity to influence it and the space-time entity would inflate giving 'time' to create energy (then particulate matter) as a result of spontaneous creation from the vacuum energy until time itself was slowed by the gravity ... or perhaps the 'large' space-time bubble interracted with a smaller anti-time granule which rapidly reduced the speed of time and ended the rapid inflationary period ... 

This would eliminate the need for a "massive" singularity prior to the big bang, eliminate the need for energy before it was created in the big bang, our space-time entity would not exist before the big bang ... basically it would be everything from nothing, the big bang being a simple, finite probability, spontaneous creation event ...

Ok, I've stopped running ...    Where is the big hole in this?

AndyG

[jetstream]

I have a question,where did the "time particle" come from?

[nucleardwarf]

Ah! I understand now - nobody has the answer!

[Cath]

Ok, I've stopped running ...    Where is the big hole in this?

In the human way of thinking?

[Cath]

Ah! I understand now - nobody has the answer!

[101nut]

I have a question,where did the "time particle" come from?

The "granular" nature of space-time has been hypothesised by several. I'm wondering whether each "granule" could be the result of seperate, spontaneous, space-time creation events rather than being variations of a single space-time continuum ...

It's really the initial nature of time that the op originally questioned and that may be explained by a particulate-time model ... is there any other model for time in the pre-energy-rich and pre-inflationary universe?

AndyG

[jetstream]

I've just learned what a singularity is (kind of) and find it interesting to watch as cosmologists/physicists trace the path back toward whatever "event(s)" brought us and everything else into existence.The concept of what singularities are is crucial to understanding origins of the universe and if the big bang had time to happen,if it happened.I used to think that a singularity was like how you and the OP do. ie "energy and matter condensed into a singularity" or "massless,dimensionless nothing",objectifying the term without taking the math into consideration(myself).Hawking type radiation comes from something,predating the time particle.I find everyones take/interpretation of the subject very interesting and as long as were learnin' we're winnin'