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kevin1981
2015-Aug-07, 09:29 PM
As i understand it, the big bang theory starts from a very small, hot dense state. And from that state it expanded rapidly. We do not know about T= 0

So, we can not really say it started from nothing because we do not know that. So, is it possible that time still existed before the big bang ? Maybe, time is eternal. Maybe, complete nothingness has never existed.

For me, the big questions are, where did the energy come from and how come there was so much of it !

Cougar
2015-Aug-08, 12:50 AM
So, we can not really say it started from nothing because we do not know that. So, is it possible that time still existed before the big bang ?

Well, we don't know if it did or not. That allows for the possibility, but if there's no way to tell, basing an idea or theory on a pre-big bang scenario, as some cosmologists have done, seems to be off on a bad start. It's unclear whether we'll ever pierce the big bang curtain. :confused-default:

Grey
2015-Aug-08, 12:05 PM
For me, the big questions are, where did the energy come from and how come there was so much of it !There is quite a bit of speculation here. My favorite is the possibility that there actually isn't any. That is, it's possible that all the energy in radiation and matter is balanced by the negative gravitational potential energy of the universe. We don't have enough information to know whether that's really correct or not, but it's possible that the total energy of the universe is zero.

kevin1981
2015-Aug-08, 02:16 PM
Yes, i read that Lawrence Krauss favours that idea. How come we do not have enough information, what information would we need to be able to be more confident that the total energy of the universe is zero ?

WayneFrancis
2015-Aug-09, 05:11 AM
Yes, i read that Lawrence Krauss favours that idea. How come we do not have enough information, what information would we need to be able to be more confident that the total energy of the universe is zero ?
We'd need to be able to see the entire universe and even then we wouldn't "know". What we would have is a model that fits the observations. We have that now. So it is just one possibility. The more we know the more alternative explanations we can rule out.

kevin1981
2015-Aug-09, 08:13 PM
I see. I know one of the requisites is that the universe needs to be flat. And as it stands, the universe does seem very flat according to observations.

I like the idea of some sort of platonic realm. Where the laws of nature exist without the need for anything else. There are formless and take up no space, time or energy.

Like the number One. If there is complete nothingness, then fair enough. But as soon as there is a space/time, then there is One space/time. It seems, the number One was there before the space/time. The number One always existed. Maybe it was not being "used", but as soon as there was the first material substance, numbers came into play. They exist in a formless platonic realm alongside the laws of nature !

Cougar
2015-Aug-11, 11:46 AM
I like the idea of some sort of platonic realm. Where the laws of nature exist without the need for anything else. There are formless and take up no space, time or energy.



"The laws of nature must have existed before even time began in order for the beginning to happen. We say this, we believe it, but can we prove it? No." [Leon Lederman, The God Particle]

PetTastic
2015-Aug-11, 11:52 AM
"The laws of nature must have existed before even time began in order for the beginning to happen. We say this, we believe it, but can we prove it? No." [Leon Lederman, The God Particle]

Could they have any meaning without space and time?
Without space and time you can't even define energy, can you?

Cougar
2015-Aug-11, 01:00 PM
Could they have any meaning without space and time?
Without space and time you can't even define energy, can you?

Unknown. :D

Jeff Root
2015-Aug-11, 03:45 PM
The total energy of the Universe could be zero. In that case,
somehow positive and negative energy got "pulled apart", so
that energy potentials exist and work can be done.

But purely intuitively, it seems like "pulling" the positive and
negative energy apart from each other would be doing work,
itself requiring energy. Which obviously can't be right. Even
if we have no idea what mechanism could have pulled them
apart, can this intuitive objection be explained away?

-- Jeff, in Minneapolis

Ken G
2015-Aug-11, 04:33 PM
The total energy of the Universe could be zero. In that case,
somehow positive and negative energy got "pulled apart", so
that energy potentials exist and work can be done.Energy doesn't have inertia, so does not need to be "pulled."


But purely intuitively, it seems like "pulling" the positive and
negative energy apart from each other would be doing work,
itself requiring energy. Which obviously can't be right.Correct, that isn't right. But the larger issue here is, what difference does it make if we say the global energy is zero or something else? The only principle we have is that energy is conserved in the local processes that occur, it never matters what the energy actually is-- and indeed, it is routine for energy to be different in different reference frames. So there is nothing special about "zero" energy such that we should associate it with "before" there was a universe. If there's no universe there, then it does not have an energy, which is not the same as saying its energy is zero. And if there is a universe there, it can have any energy-- there is nothing meaningful about the energy, only the changes in energy. So if we see a universe with a lot of energy, it's not clear this has any global importance. Conservation of energy is about changes in the form of energy that are happening locally.

Jeff Root
2015-Aug-11, 05:14 PM
The total energy of the Universe could be zero. In that case,
somehow positive and negative energy got "pulled apart", so
that energy potentials exist and work can be done.
Energy doesn't have inertia, so does not need to be "pulled."
That's a non sequitur. The fact that energy doesn't have
inertia doesn't have anything to do with the fact that the
positive and negative energy had to be "pulled apart" in
some way in order for measureable energy to exist.




But purely intuitively, it seems like "pulling" the positive and
negative energy apart from each other would be doing work,
itself requiring energy. Which obviously can't be right.
Correct, that isn't right. But the larger issue here is, what
difference does it make if we say the global energy is
zero or something else? The only principle we have is that
energy is conserved in the local processes that occur, it
never matters what the energy actually is-- and indeed, it
is routine for energy to be different in different reference
frames. So there is nothing special about "zero" energy
such that we should associate it with "before" there was a
universe. If there's no universe there, then it does not have
an energy, which is not the same as saying its energy is zero.
And if there is a universe there, it can have any energy--
there is nothing meaningful about the energy, only the
changes in energy. So if we see a universe with a lot of
energy, it's not clear this has any global importance.
Conservation of energy is about changes in the form of
energy that are happening locally.
If the positive and negative energy are not separated from
each other, there can be no energy potential difference, so
nothing can happen. The amount of stuff that can happen
is determined by the amount of separation of energy into
positive and negative. A universe with no separation of
energy into positive and negative would be unchanging,
and would in effect have zero energy, whether it contains
matter or is completely empty.

I would argue, though, that any universe with matter
must also contain energy, and any universe with energy
must also contain matter.

And further, that any universe with spacetime must also
have matter/energy in proportion to the spacetime.

So I'm saying that the existence of a universe is
synonymous with the existence of a separation between
positive and negative energy. They are the same thing.

-- Jeff, in Minneapolis

Ken G
2015-Aug-11, 08:54 PM
That's a non sequitur. The fact that energy doesn't have
inertia doesn't have anything to do with the fact that the
positive and negative energy had to be "pulled apart" in
some way in order for measureable energy to exist.
Well, pick whatever metaphor you like, but "positive" and "negative" energy never need to be "pulled apart," nor is "extra work" required to "pull them apart." That's all just nonsense.

If the positive and negative energy are not separated from
each other, there can be no energy potential difference, so
nothing can happen. You can think about energy any way that works for you, but if you want to imagine it gets "separated", this can lead you into misconception. To see how, let us take the simplest case we can imagine-- dropping a rock. When the rock is in your hand, we can say the rock has zero total energy if we like-- we can say it has zero kinetic energy (if we are in its reference frame), and we can say it has zero gravitational potential energy (if we choose to count our beans in that manner). Now let go of it-- a short time later, we can say the rock has positive kinetic energy, and negative potential energy. These positive and negative energies do not need to be regarded as "separated", as if they were spatially "pulled apart"-- they are both simply properties of the system. Nor does one need to look for "extra work" to understand how those energies got "separated", the work done in that situation is precisely the reason we have a positive and a negative energy there, and that work is equal to either one of them, depending on whether we regard it as work done on the rock or work done by the rock. That's all the work there, it's fully accounted for by the fact that we started with two energies that were both zero, and ended with one positive and one negative-- that's work. So it's nonsense to go looking around for some kind of source of extra work needed to achieve this "separation", the work is the reason the energy is conserved in the first place, in the way of bean-counting we call "conservation of energy."


I would argue, though, that any universe with matter
must also contain energy, and any universe with energy
must also contain matter.None of which has anything to do with the nonsense above. What universes could or could not contain is a hypothetical issue that is only useful as a device to understand how theories work. For example, the theory of how light works is usually not regarded as a type of "matter", so a universe of pure light would be said to contain energy and not matter. But it is irrelevant to the other things being said about energy.


So I'm saying that the existence of a universe is
synonymous with the existence of a separation between
positive and negative energy. They are the same thing.
How does that have anything to do with your claim above that "But purely intuitively, it seems like "pulling" the positive and
negative energy apart from each other would be doing work, itself requiring energy." That nonsense is all I am talking about here, not what you think of as energy. There are many ways to think of what energy "is", yours may work fine in many situations-- but not if it makes you state the quoted remark, that just isn't how energy works.

Jeff Root
2015-Aug-12, 05:02 PM
Well, pick whatever metaphor you like, but "positive" and
"negative" energy never need to be "pulled apart," nor is
"extra work" required to "pull them apart." That's all just
nonsense.
In post #3, Grey pointed out that "it's possible that all
the energy in radiation and matter is balanced by the
negative gravitational potential energy of the universe."
I agree that that is a neat idea and might even be correct.
If it is, then it isn't possible to have one without the other.
They must always be quantitatively equal. In order to get
equal quantities of "positive" and "negative" energy, those
two quantities have to be coordinated in some way. That
means they are created together and destroyed together.
So the process of creating energy is the act of separating
"positive" from "negative" energy, or "pulling them apart".

-- Jeff, in Minneapolis

GarethMeredith
2015-Aug-13, 11:28 PM
So, is it possible that time still existed before the big bang ? Maybe, time is eternal. Maybe, complete nothingness has never existed.

For me, the big questions are, where did the energy come from and how come there was so much of it !

Time may not even exist in quantized theories of gravity. At least, path quantization and even Bohm trajectory quantizations both lead our gravitational theory into timelessness.

Energy is probably a natural facet of the vacuum, so the real question is where did space come from? Does space hold the same meaning as you wind the clock back and you find geometry missing? Can you describe space without geometry? And perhaps just as important, can you describe such a thing as a beginning without time? If no matter was about, how do you gauge time into your theory since relativity says you cannot measure time without matter? So many questions and little answers.

KlausH
2015-Aug-14, 12:27 AM
This is really not a science question.

It is basically the question about the "first cause".
Whatever "explanation" for the origin of time, space, the BB, etc you come up with - let's call it "bla" - there will always be the subsequent question:
Where did "bla" come from?

Even if you resort to a creator the question remains: where did the creator come from? Who or what created the creator?

Even if you resort to tricks - as Grey mentioned - by declaring the overall energy of the universe to be zero the question still remains where did the laws come from that allow zero energy to be split into a "positive" and a "negative" component?

However you twist and turn it, it always comes back to the question of the "first cause".

And that is not a science question but a philosophical one.
This is the wrong part of the forum for this question.

In fact, given the ignorant hostility this forum exhibits towards anything philosophical, this is altogether the wrong forum for this question.

GarethMeredith
2015-Aug-14, 12:39 AM
Even if you resort to tricks - as Grey mentioned - by declaring the overall energy of the universe to be zero the question still remains where did the laws come from that allow zero energy to be split into a "positive" and a "negative" component?

Its a good question, and particle-antiparticle symmetry isn't the only one. The universe appears to favor symmetries.

Ken G
2015-Aug-14, 01:59 AM
In order to get
equal quantities of "positive" and "negative" energy, those
two quantities have to be coordinated in some way. That
means they are created together and destroyed together.
So the process of creating energy is the act of separating
"positive" from "negative" energy, or "pulling them apart".The "nonsense" I was referring to was your claim that it requires "extra work" to separate them. There is no extra work there, the work is the energy that is being "separated." When you do work, you transfer energy from one form to another, that's what conservation of energy is all about.

As I said above, it is no kind of breakthrough idea that the appearance of positive energy comes along with negative potential energy, that's how the whole concept of potential energy was originated in the first place. So it's no kind of "explanation" to where the energy "came from" to introduce a convenient bean-counting device, and call it potential energy. The question of how the energy was transformed into the form we find it has always been the question, not the bean-counting of how we track it.

malaidas
2015-Aug-14, 07:41 AM
This is really not a science question.

It is basically the question about the "first cause".
Whatever "explanation" for the origin of time, space, the BB, etc you come up with - let's call it "bla" - there will always be the subsequent question:
Where did "bla" come from?

Even if you resort to a creator the question remains: where did the creator come from? Who or what created the creator?

Even if you resort to tricks - as Grey mentioned - by declaring the overall energy of the universe to be zero the question still remains where did the laws come from that allow zero energy to be split into a "positive" and a "negative" component?

However you twist and turn it, it always comes back to the question of the "first cause".

And that is not a science question but a philosophical one.
This is the wrong part of the forum for this question.

In fact, given the ignorant hostility this forum exhibits towards anything philosophical, this is altogether the wrong forum for this question.

Yes ,one the difficult things for some to swallow is that there are questions to which an empirical answer is not going to be forthcoming. This is just such a question. You always run into 2 impossibile answers for our heads to get around.

Eta: indeed just a reasonable consideration of what an empirical answer would need to satisfy, reveals that no such answer can ever be given. This is not a limitation of technology or even knowledge, of things are eternal we can never verify this fact no matter how far we go ba k, and if things did have a beginning then even if we saw it, it would just be curtain beyond which we could never know if something came before it or not.

Jeff Root
2015-Aug-14, 01:36 PM
Ken,

How the energy in the Universe has changed form is one
big bunch of questions; How that energy came to be is a
separate question. I said that creating energy must require
"pulling" positive energy and negative energy apart. That
sounds, intuitively, like doing work. It obviously isn't.
But I don't know how to avoid the impression that it is.

Asserting that I'm asking the wrong question is just evading
the question. Exactly what is required to create energy?
How can positive and negative energy be separated from
each other so as to create energy? I have no clue how to
answer that question, but it is definitely the right question.

Exactly what is required to create spacetime? The answer
to one question is the answer to both.

-- Jeff, in Minneapolis

Ken G
2015-Aug-14, 02:28 PM
How the energy in the Universe has changed form is one
big bunch of questions; How that energy came to be is a
separate question.I don't agree, those are the same bunch of questions. The deepest way to understand conservation laws is as symmetry principles. Conservation of energy can be regarded as a symmetry in time-- it stems from the idea that there is no explicit time dependence in the laws of physics, meaning that if you set up exactly the same universe at any time, it will do exactly the same thing. Put differently, this means there is no "universal clock" ticking in the background, to tell the laws "what time it is."

Now, of course we don't know if that idea is true in regard to the origin of a universe. So we can either throw it out, and just try to make observations that tell us what happened there, or in the absence of those observations, we can keep it and see what ramifications it has. If we keep it, we are saying that there is a sameness in time, that allows us to seek a bean-counting device that if properly chosen, will give us a conserved quantity we can call energy. To make this work, we need a concept of potential energy, otherwise we have not found the correct device to express the time invariance. What all this means is, if we have the right energy concept, we will find it maintains its value. What that value is is rather arbitrary, we can make it zero or we can make it some other constant, and it wouldn't make any difference.

So what all this means is, the overall conservation of energy says that energy is only transformed from one type to another, which is a fancy way to say it is a quantity that sums to a constant answer. We know it is possible to find such a quantity from the time invariance principle (if we choose to adopt such a principle in the Big Bang, which is untested), so all that remains is to figure out what quantity will work, i.e., what are the necessary forms of energy. In the process of determining the necessary forms of energy, we will also need to determine what processes cause this energy to change from one form to another. That is the real question for understanding "where the universe came from," when framed as the question "what processes caused the energy to change form." Once we've answered that, we're finished with the energy issue, there's no additional question like "how did the positive and negative energies get separated", because that's the exact same issue.



I said that creating energy must require
"pulling" positive energy and negative energy apart. That
sounds, intuitively, like doing work. It obviously isn't.Right, so that's why it's not a good language for talking about what is happening there. This is how we identify a bad way to say what is happening-- it is a way that sounds, intuitively, like it would have ramifications that it does not in fact have. So we find a better language, which is, that energy is transformed from one type to another, such that a positive increment of one type implies a negative increment of some other type.


Asserting that I'm asking the wrong question is just evading
the question. Exactly what is required to create energy?Not at all, when I said you were asking the wrong question, I supplied the right question. That's hardly "evading" the question, that's replacing confusing language about "pulling apart" energy with clear language about what mechanisms are capable of "converting" energy from one type to another. That is still the question that needs answering, but it is the right question (at least, as far as we currently understand the value of our concept of energy.)


How can positive and negative energy be separated from
each other so as to create energy? And that, once again, would be the wrong way to frame the question. If "separating" energy gives you the sense that it must be "created", you are not using the energy concept the way that works-- the way that works is that energy is not created, it is converted from one subtype to another. Nothing to "separate" there, but we do need processes that convert it. If take dollars and buy a diamond, I am reducing my bank account but raising the value of my possessions. I have "converted wealth" from one form to another, but should I be asking "how can positive and negative wealth be separated from each other so as to create wealth?" If I framed what I did there in that language, people would have no idea what I was talking about.



Exactly what is required to create spacetime? The answer
to one question is the answer to both.I would call that the fallacy of "reasoning by non sequitur."