how can you create something from nothing ?

[alpha tech]

How does the laws of physics allow something to be created from nothing?

[Mitchz95]

They don't. Matter and energy can change forms, but they can't be created or destroyed.

[alpha tech]

They don't. Matter and energy can change forms, but they can't be created or destroyed.

yes but before the big bang how could a singularity be created if no space and no time existed?

also the laws of physics would have to change for the big bang be cause it created matter, space, and time.

Edited November 5, 2015 by alpha tech
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[SargeRho]

That's simple to answer: Nothing was never the state of affairs. There was always something, even "before" time and space existed.

[Gaarst]

Depends on what you mean by "nothing" and "something":

If you mean creating mass, then use Einstein's mass-energy equivalency (E = mc²) to convert from one to another. So yes it is possible.

If you mean creating energy from an empty vacuum, then again it is possible thanks to Heisenberg's uncertainty principle: basically, very small amounts of energy are allowed to exist for very short times. There are also other various effects allowing the same kind of stuff (eg: Zero-point energy), but they rely on quantum physics and are way too complicated for me, so you'll have to ask someone else for those.

Precising your question would allow to give a more complete and accurate answer.

[alpha tech]

the big bang was an explosion of space, time and matter. but how do you get the explosion? (think before the big bang.)

Edited November 5, 2015 by alpha tech
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[Gaarst]

yes but before the big bang how could a singularity be created if no space and no time existed?

also the laws of physics would have to change for the big bang be cause it created matter, space, and time.

We don't know. It is as simple as that.

We can't go further than Planck's time because that's when physics really start to do fuzzy things, and we cannot currently describe these fuzzy things, like really not at all. That is until we find a working theory of everything, and even then we might not be able to describe it properly.

[Bill Phil]

Because the sum of everything is nothing.

[K^2]

yes but before the big bang how could a singularity be created if no space and no time existed?

There is no such thing as "before" the big bang. Think of the big bang as the North Pole. The place from which you can only go South. What's North of North Pole? It's a bit of a silly question, isn't it? It's exactly the same way. The only time direction from Big Bang is forward. There is no such thing as time before Big Bang. Does that help?

[SomeGuy12]

There is no such thing as "before" the big bang. Think of the big bang as the North Pole. The place from which you can only go South. What's North of North Pole? It's a bit of a silly question, isn't it? It's exactly the same way. The only time direction from Big Bang is forward. There is no such thing as time before Big Bang. Does that help?

No. K^2, you may be a well educated guy in physics, but your statement is nonsense. Within the universe we are in, something can't come from nothing, and something must always precede something else happening in time. In terms of what we know, the instant the big bang began something impossible happened. Inconveniently, we don't have any at hand means to resolve this paradox.

[Gaarst]

No. K^2, you may be a well educated guy in physics, but your statement is nonsense. Within the universe we are in, something can't come from nothing, and something must always precede something else happening in time. In terms of what we know, the instant the big bang began something impossible happened. Inconveniently, we don't have any at hand means to resolve this paradox.

In terms of what we know ?

Thing is, as I mentioned in my previous post, we don't know what happened at the instant t=0. Conventional physics, including the very notions of space and time, break down around Planck's time (~10^-43 s after the Big Bang) and we need a new theory bringing together quantum field theory and general relativity to only hope to know what happened back then.

This is very similar to the issue with black holes: describing a singularity requires using relativity and quantum mechanics together, which we can't today.

Edited November 6, 2015 by Gaarst

[K^2]

No. K^2, you may be a well educated guy in physics, but your statement is nonsense. Within the universe we are in, something can't come from nothing, and something must always precede something else happening in time.

That's simply because you don't understand what time is. Go take a course in differential geometry. When you're done, we can chat and I'll get into the mathematics of it all. Until then, North Pole analogy is the best you're going to get. If you want to keep insisting that it's wrong without understanding anything about space-time, well, that's a really stupid thing to do. I'm just going to leave it at that.

[PB666]

No. K^2, you may be a well educated guy in physics, but your statement is nonsense. Within the universe we are in, something can't come from nothing, and something must always precede something else happening in time. In terms of what we know, the instant the big bang began something impossible happened. Inconveniently, we don't have any at hand means to resolve this paradox.

As strange as it may sound K^2 is probably right though i cannot agree with the way he said it. The basic problem is that when you say space or time, and we use our best definitions that are not QM we run into both as child processes of space time. Here is an example, suppose i say an apple fell and hit isaac on the noggin. But was its Isaacs nogging that hit the apple. The apple is falling is in the non-inertial reference frame, and the noggin was accelerated by earths surface to the apple.

This would appear to be random, but if we reverse time then all inertias appear to lead to a single point. No problem, our three space dimensions become a point particle, of course with massive particles this is unstable so we make mass disappear. Ok we have a infinite energy density state with no mass, hmmm, theoretically then relativistic gravity just also disappeared, oh damn, and so did space-time and time. So a free unassociated QM sigularity can do sci-fi like stuff, like be at any, all or no space-time all at once. One such state is our known universe.

What happens before CMBR is speculation, before inflation moreso and i remind everyone that when you pull the cord on relativistic gravity, only the undefinable quantum gravity is left; left to act on a single point of infinite energy density. Things like time, space, temperature, polarity and charge become meaningless words.

To rephase what K2 said if you assume that the entire universe originated from a quantum singularity, then at the point quantum mechanics solely defines the state, time becomes meaningless.

[problemecium]

It seems the real question here is "how did the Big Bang occur if the law of conservation of energy / mass dictates that matter and energy cannot arise spontaneously in empty space?"

To answer that is hard. The nature of the Big Bang is, and has for a while been, one of the hardest topics to study in all of science. Here's a few possibilities:

- Time did not exist before the Big Bang, so in a sense there has always been the same amount of matter and energy for all of time.

- The laws of physics only apply within the universe, so talking about boundary conditions at the edge of the universe, outside it, before the beginning, or after the end means throwing all known physical theorems into doubt.

- Another universe existed before our own. Perhaps it collapsed into a Big Crunch and then rebounded; perhaps it moved through a higher dimension of space and collided with our own, transferring huge amounts of energy into it and causing a massive explosion; perhaps our universe was created from something that occurred in the previous universe, artificially or by a natural process.

- Quantum Mechanics suggests that things CAN be created from nothing, if you're really sneaky about it, i.e. create only a little bit of stuff or get rid of it really quickly. And it has actually been calculated that the rough probability of a huge explosion of spontaneous matter and energy popping up out of empty space is such that it might happen once within all the known volume of the universe every 100 trillion years or so... so perhaps exactly that happened 14 billion years ago and the universe was essentially created by the Kraken.

[GeneralVeers]

How does the laws of physics allow something to be created from nothing?

Simple: by separating positive from negative. +1 + -1 = 0. Take away the plus sign in the middle of the equation, and you've got a positive on one part of the page, and a negative on another part of the page. Congratulations, you just created a Universe.....albeit a Universe that only has two particles in it.

yes but before the big bang how could a singularity be created if no space and no time existed?

I think the current hypothesis is that the Big Bang didn't actually come from a singularity. Also, keep in mind that from our viewpoint there are no actual singularities anywhere in our Universe. They're impossible. When an object (such as a star that's too big for its own good) collapses within its own event horizon to form a black hole, the collapse never actually finishes; from our viewpoint that would take an infinite amount of time, because time stops at the event horizon. Every black hole in existence, everywhere in this Universe, is still collapsing; the infalling matter appears to us to be frozen in time, just above the event horizon, falling towards it infinitely slowly.

[YNM]

K^2 analogy of poles is best for layman. For those interested in more logic, I'll just say this : even nothingness wasn't there, emptyness wasn't there, because there's no space and no time to (uh, spacetime) contain them. Even the term "was" shouldn't really apply...

... which is why the math is sooo hairy.

[Yourself]

I think the current hypothesis is that the Big Bang didn't actually come from a singularity. Also, keep in mind that from our viewpoint there are no actual singularities anywhere in our Universe. They're impossible. When an object (such as a star that's too big for its own good) collapses within its own event horizon to form a black hole, the collapse never actually finishes; from our viewpoint that would take an infinite amount of time, because time stops at the event horizon. Every black hole in existence, everywhere in this Universe, is still collapsing; the infalling matter appears to us to be frozen in time, just above the event horizon, falling towards it infinitely slowly.

Which is to say there are no naked singularities.

At least so long as you subscribe to the cosmic censorship hypothesis, anyway.

[cantab]

before the big bang ... no space and no time existed?

There's your problem - that's a contradiction. If the Big Bang is the earliest point in time then there was no "before".

Now causality that doesn't depend on time is possible, but we need to be careful when talking about it.

But my answer to the original question is that the Universe wasn't created or caused by anything. It just exists. And ultimately, no matter the scientific details, there has to be something that "just is", that doesn't owe its existence to anything else. Whether that something is the universe we see, some larger multiverse, or even 'god' I don't know. So I choose to assume the simplest - that it's just the universe we see (and its expected extension beyond our visible horizon) - until I have evidence to the contrary.

[Bill Phil]

There is no such thing as "before" the big bang. Think of the big bang as the North Pole. The place from which you can only go South. What's North of North Pole? It's a bit of a silly question, isn't it? It's exactly the same way. The only time direction from Big Bang is forward. There is no such thing as time before Big Bang. Does that help?

But what, my friend(?), is time?

Therein lies the question. Time is a human concept, describing the change of the universe. Not an inherent property of the universe. Things change, yes, but we only experience these changes in a specific order, even though it may be different.

To use a spherical analogy:

A line on a map may be straight, but on the sphere it is curved.

And going north at the North pole goes South. Also, which North pole?

[PB666]

It seems the real question here is "how did the Big Bang occur if the law of conservation of energy / mass dictates that matter and energy cannot arise spontaneously in empty space?"

To answer that is hard. The nature of the Big Bang is, and has for a while been, one of the hardest topics to study in all of science. Here's a few possibilities:

- Time did not exist before the Big Bang, so in a sense there has always been the same amount of matter and energy for all of time.

- The laws of physics only apply within the universe, so talking about boundary conditions at the edge of the universe, outside it, before the beginning, or after the end means throwing all known physical theorems into doubt.

- Another universe existed before our own. Perhaps it collapsed into a Big Crunch and then rebounded; perhaps it moved through a higher dimension of space and collided with our own, transferring huge amounts of energy into it and causing a massive explosion; perhaps our universe was created from something that occurred in the previous universe, artificially or by a natural process.

- Quantum Mechanics suggests that things CAN be created from nothing, if you're really sneaky about it, i.e. create only a little bit of stuff or get rid of it really quickly. And it has actually been calculated that the rough probability of a huge explosion of spontaneous matter and energy popping up out of empty space is such that it might happen once within all the known volume of the universe every 100 trillion years or so... so perhaps exactly that happened 14 billion years ago and the universe was essentially created by the Kraken.

First there is the suggestion that during inflation and the short period that followed that energy poured into our universe. I neither support or deny the pre CMBR suggestion.

Second, dark energy suggests that energy has poured into our universe.

Both of these may represent transition from energy states we do not understand tobstates we can deduce.

[SomeGuy12]

That's simply because you don't understand what time is

What experimental evidence indicates that differential geometry is anything more than a hypothesis? I have read about precisely none, and in terms of factual validity, these theories are only slightly better than turtles all the way down.

And even if you have a theory that time is a property that is related to the geometry of the universe, what about causality...

[Kerbart]

How does the laws of physics allow something to be created from nothing?

Simple. Take a handful of bankers and add a lawyer or two. Be careful with adding politicians to the mix or you'll end up with way more than what you aimed for.

[Yourself]

What experimental evidence indicates that differential geometry is anything more than a hypothesis? I have read about precisely none, and in terms of factual validity, these theories are only slightly better than turtles all the way down.

And even if you have a theory that time is a property that is related to the geometry of the universe, what about causality...

https://en.wikipedia.org/wiki/Tests_of_general_relativity

If you're looking for something more practical, the accuracy of GPS depends pretty critically on accurate predictions from GR. So, you know, that wouldn't work terribly well if GR weren't a good model of reality.

[K^2]

But what, my friend(?), is time?

Therein lies the question. Time is a human concept, describing the change of the universe. Not an inherent property of the universe. Things change, yes, but we only experience these changes in a specific order, even though it may be different.

So the complication is that we actually say "time" and can mean several of related, but distinct concepts.

1) Time as a parameter in QM. We usually have proper time in mind when we talk about this one.

2) Time as a coordinate in Relativity. This one can be strictly defined in terms of differential geometry.

3) Time as casual ordering of events. This is the trickiest to define properly, and you have to drag entropy into it.

And then you have various cross-disciplines. Relativistic Quantum Field Theory has to deal with both 1) and 2). Which gets really hairy. Statistical Mechanics deals with 1) and 3). There are only two realistic scenarios where you need to talk about all three. That's event horizon of a black hole and the Big Bang. If you have a good grasp of QCD, and Condensed Matter theory, you can have some idea of what's going on in such condition using mean field theory approximations. It's ugly, and our insight into exact physics of it is very limited to say the least.

On the other hand, the precise QM of what's going at these kinds of places isn't really relevant to the discussion. So once we take what we know about space-time geometry of these places, we can talk about time there purely in terms of differential geometry.

And going north at the North pole goes South. Also, which North pole?

Ah, if it only weren't for the dark energy... Having a "South" pole in that analogy would imply a Big Crunch. Which isn't going to happen. I've only used spherical geometry as a most familiar illustration. The "North Pole" still behaves pretty much the same way. But there is no "South Pole". It just stretches out to infinity as far as we can tell.

Which is very grim news. If universe is "infinite" in time span, and we happen to live in its first 14by, this Universe won't be habitable for very long.

[Silver_Swift]

I think the question "what was there before the big bang?" is valid, if worded confusingly. It's all good and well to say that time started at the big bang and there is no "before" that for anything to be in, but that statement itself pre-supposes the laws of physics. Those laws have complexity, order, they can't just have poofed into existence at the start of time with no cause or explanation. If they did, there would be no reason we have this particular set of laws, rather than some arbitrary other set.

Now this is a confusing question, because even if you did find a reason for why we have these specific laws of physics you could just follow the rabbit hole further down (eg. if we are living in a computer simulation, what laws is the computer running on?). There is probably always going to be some point where we are just going to have to admit that we don't know yet.