Why is our universe the way it is?

[fedorfan]

Would laws be different if the big bang happened a different way? Like, if the big bang happened again would gravity, particles, and anything be different in physics?

 

[DaveC426913]

Yes. In fact, this is a great big-ass deal in Cosmology (if not THE big-ass deal).

The universe is considered to be "exquisitely tuned" for life as we know it.

There are a number of fundamental constants about our universe that, if anyone of which were evenly slightly different, the universe would have developed so differently as to be incompatible not merely with life, but with matter (i.e. atoms).

How our universe has managed to come into existence in its current configuration instead of any of countless other configurations is a question that keeps Cosmologists and Theologists awake at night.

 

[SpaceTiger]

See another recent thread on the topic:

https://www.physicsforums.com/showthread.php?t=127595"

 

[bluestone35]

I am new to the list. Not a scientist in any manner, just an artist w/ great curiosity. Forgive me if I trip over my own ignorance. It seems that the"'exquisitely tuned' for life" idea suggests the anthropic principle. From reading some of the postings, I suspect that Leonard Susskind is not one of the favored gurus, but he does write convincingly regarding the A/P. While I am reluctant to pose such a broad question, I wonder what the current thoughts are regarding the A/P.

Ben Mahmoud
http://benmahmoud.com

 

[franznietzsche]

I am new to the list. Not a scientist in any manner, just an artist w/ great curiosity. Forgive me if I trip over my own ignorance. It seems that the"'exquisitely tuned' for life" idea suggests the anthropic principle. From reading some of the postings, I suspect that Leonard Susskind is not one of the favored gurus, but he does write convincingly regarding the A/P. While I am reluctant to pose such a broad question, I wonder what the current thoughts are regarding the A/P.

Ben Mahmoud
http://benmahmoud.com

Weak or strong?

The weak anthropic principle is tautology. Of course we see conditions that permit life, since there is life in the universe, so conditions in the universe permit life. The strong anthropic principle is theology, not science.

 

[SpaceTiger]

The weak anthropic principle is tautology. Of course we see conditions that permit life, since there is life in the universe, so conditions in the universe permit life.

But the question is the extent to which this is an explanation of what we observe. That it's true is uncontroversial. That it's relevant is not.

 

[franznietzsche]

But the question is the extent to which this is an explanation of what we observe. That it's true is uncontroversial. That it's relevant is not.

I don't see that it can be used as an explanation of anything--unless one accepts the strong anthropic principle as well.

Using the statement 'we observe conditions that permit life because we are alive' as an explanation for why the conditions of the universe permit life confuses cause and effect.

 

[SpaceTiger]

I don't see that it can be used as an explanation of anything--unless one accepts the strong anthropic principle as well.

Using the statement 'we observe conditions that permit life because we are alive' as an explanation for why the conditions of the universe permit life confuses cause and effect.

Suppose there were N self-contained "universes", only one of which could support life. What is the answer to the question, "Why do the conditions of my universe permit life?" Certainly I can correctly say that if they didn't, I wouldn't be around to ask. Granted, that's not a complete answer, because I can go on and ask, "why do the conditions of any universe permit life?", but in this hypothetical case, it tells us something, it tells us why we don't live in one of the N-1 other "universes".

The point is that our observations of the universe might be biased by our very existence. If the above hypothetical case were true, it would be foolish of me to attempt a theory of universe formation that always led to conditions that support life. On the other hand, it's possible that all N self-contained universe can support life. Then, there is no bias and our theories would want to make a concerted effort to explain the parameters of our universe from something more fundamental. This latter case is preferred by scientists because it means that there is more information in our own universe -- studying it will tell us more about how the universe came to be. In fact, many scientists would say that we should always disregard the anthropic principle because it amounts to "giving up". The more biased our surroundings, the less point there is in studying them.

 

[franznietzsche]

Suppose there were N self-contained "universes", only one of which could support life. What is the answer to the question, "Why do the conditions of my universe permit life?" Certainly I can correctly say that if they didn't, I wouldn't be around to ask. Granted, that's not a complete answer, because I can go on and ask, "why do the conditions of any universe permit life?", but in this hypothetical case, it tells us something, it tells us why we don't live in one of the N-1 other "universes".

This of course, supposes that there are other universes--a by definition untestable proposition.

The point is that our observations of the universe might be biased by our very existence. If the above hypothetical case were true, it would be foolish of me to attempt a theory of universe formation that always led to conditions that support life. On the other hand, it's possible that all N self-contained universe can support life. Then, there is no bias and our theories would want to make a concerted effort to explain the parameters of our universe from something more fundamental. This latter case is preferred by scientists because it means that there is more information in our own universe -- studying it will tell us more about how the universe came to be. In fact, many scientists would say that we should always disregard the anthropic principle because it amounts to "giving up". The more biased our surroundings, the less point there is in studying them.

I would argue that the anthropic principle is a waste of time because it provides nothing of scientific value--except the recognition that the fundamental configuration of the universe that we see, may not be the only possible one. But it does not explain anything.

 

[SpaceTiger]

This of course, supposes that there are other universes--a by definition untestable proposition.

The argument doesn't require the existence of other universes, only the possibility of existence given what we know.

I would argue that the anthropic principle is a waste of time because it provides nothing of scientific value--except the recognition that the fundamental configuration of the universe that we see, may not be the only possible one. But it does not explain anything.

How does it provide the "recognition that the fundamental configuration of the universe that we see, may not be the only possible one"? Why is this recognition not possible without the anthropic principle? Why does the issue of bias not arise if there is only one universe? What do you mean by "it does not explain anything"? Is that merely a semantic objection or do you believe that there are no logical connections between our existence and the parameters of our universe?

 

[franznietzsche]

The argument doesn't require the existence of other universes, only the possibility of existence given what we know.




How does it provide the "recognition that the fundamental configuration of the universe that we see, may not be the only possible one"? Why is this recognition not possible without the anthropic principle? Why does the issue of bias not arise if there is only one universe? What do you mean by "it does not explain anything"? Is that merely a semantic objection or do you believe that there are no logical connections between our existence and the parameters of our universe?

I think, my objection may be largely semantic--it depends on the nature of the logical connection you are suggesting--the cause and effect nature specifically. This is something that I am not clear on, and various explanations of the principle suggest differently. Some seem to suggest that our existence causes the parameters of our universe to take the values they do--this is what I am rejecting.

 

[Chronos]

This is a bad argument, IMO. Forcing the laws of the universe to permit our existence is unnecessary and confusing. Obviously, we would not otherwise be here to ask that question. How astonishing is that? I agree to the extent a universe that forbids our existence is illogical. I do not see that it demands our existence.

 

[SpaceTiger]

Some seem to suggest that our existence causes the parameters of our universe to take the values they do--this is what I am rejecting.

I agree with you about the strong anthropic principle -- it is basically a religious statement. I also agree with you that our existence did not cause the universe. However, I stand by my use of the word "explanation". The anthropic principle does not explain why the universe came about in the way it did, but it does tell us why we observe what we do. The latter question is the one the scientific method is directly addressing, though the former is the one we would really like to answer.

If a certain characteristic of the universe is required for us to exist, then our observation of that characteristic tells us nothing. Without being able to observe other universes (or other iterations of our own), the anthropic principle may be the only viable explanation for that observation.

 

[fedorfan]

Ive got a question, if atoms changed, would all subatomic particles change too? If so, why and how would they change?

 

[franznietzsche]

I agree with you about the strong anthropic principle -- it is basically a religious statement. I also agree with you that our existence did not cause the universe. However, I stand by my use of the word "explanation". The anthropic principle does not explain why the universe came about in the way it did, but it does tell us why we observe what we do. The latter question is the one the scientific method is directly addressing, though the former is the one we would really like to answer.

Okay, then I misunderstood what you you were claiming it explained.

If a certain characteristic of the universe is required for us to exist, then our observation of that characteristic tells us nothing. Without being able to observe other universes (or other iterations of our own), the anthropic principle may be the only viable explanation for that observation.

I think I agree with what you are saying--assuming that I understand you correctly--but I think that the wording is horrific. Much better to say that the explanation is simply 'we can only observe universes that allow us to exist' (again, tautology), than the way it is normally posited.

 

[SpaceTiger]

Much better to say that the explanation is simply 'we can only observe universes that allow us to exist' (again, tautology), than the way it is normally posited.

That's rather terse. I wouldn't expect a non-scientist to fully appreciate the consequences of that statement without further explanation.

 

[franznietzsche]

That's rather terse. I wouldn't expect a non-scientist to fully appreciate the consequences of that statement without further explanation.

Further explanation is okay. But the presentation/wording I've normally seen is horrifically confusing and unclear. Saying that we observe conditions that permit life because we are alive, could mean two very different things, depending on whether the 'because' is causal or not. This distinction is not sufficiently clear. If the because is not causal, then its ok. If the because is causal, then I think there are some issues.

 

[fedorfan]

Ive got a question, if atoms changed, would all subatomic particles change too? If so, why and how would they change?

Anybody home?

 

[Chronos]

Assumes facts not in evidence. You need a theory that explains why atoms would change before discussing how they would change. That's a cowpie in my opinion, fedorfan.

 

[fedorfan]

Alright, if the big bang happened a different way, would the atomic model as we know it change? If so why and how, if it did, would subatomic particles change(protons, neutrons, quarks, electrons, neutrinoes,etc)? If so, how and why?
thanks

 

[DaveC426913]

This is the original question, is it not? Yes. If the Big Bang happened again, it would surely produce wildly different results.

It is supposed that Heisenberg uncertainty is responsible** for the universe having anything interesting in it in the first place. The next Big Bang will produce a completely different result.

**(for example, what the Higgs Field value was when the universe "froze out" will be completely different next time)

 

[bluestone35]

This may not be to the point, but I have been thinking about the inflation model. As I understand it, space expanded at a very rapid rate, thereby separating the contents of that space. I think that would mean the spatial relationships between the electron shells and the nuculii would change; the spatial relationships between quarks would change. Does this mean the force fields changed?

 

[fedorfan]

Alright, so the atoms will change, will the smallest subatomic particles change? Like neutrinoes, electrons, quarks etc.

 

[bluestone35]

Yeah, I would think they would if string theory has any meaning. Does the plank length change? Probably. And if not string theory, how about the new idea from Smolin about "braided spacetime"?

Ben

 

[DaveC426913]

This may not be to the point, but I have been thinking about the inflation model. As I understand it, space expanded at a very rapid rate, thereby separating the contents of that space. I think that would mean the spatial relationships between the electron shells and the nuculii would change; the spatial relationships between quarks would change. Does this mean the force fields changed?

Many people think that expansion of the universe is some sort of super-physical force that stretches everything in it. Like, if the universe is expanding does that mean the stars in the galaxies are getting further apart? The Earth further from the Sun? The Moon from the Earth? The atoms in the Earth from each other?

No!

It is not a force over and above other forces acting on matter and energy. And it's a very, very weak force compared to the forces in an atom, and even compared to the force of gravity between stars in a galaxy. It can only have an effect in the vast distances between galaxies where gravity is virtually zero.

That is not to say the the initial inflation of the universe wasn't extremely forceful, but it is not some "uber-force".

 

[fedorfan]

So particles wouldn't change? I wouldn't think that they would, atleast the smallest particles. Because how could quarks change, theyre point objects, I don't understand how they would change except maybe how far they are apart from each other if the universe contracted again. What I am talking about is if they would change in terms of mass and size. I don't see any logical explanation why the smallest subatomic particles would change in terms of size and mass.

 

[DaveC426913]

So particles wouldn't change? I wouldn't think that they would, atleast the smallest particles. Because how could quarks change, theyre point objects, I don't understand how they would change except maybe how far they are apart from each other if the universe contracted again. What I am talking about is if they would change in terms of mass and size. I don't see any logical explanation why the smallest subatomic particles would change in terms of size and mass.

When you say "change" you really should be saying "created".

At the earliest moments in the BB, quarks did not exist. They were created in the process of the BB, dependent on conditions at that time (though I can't tell you what conditions). If creation conditions were different**, the quarks would have no reason to be the same.

**again , it is thought that the HUP applied even in the BB, so we must assume that conditions will never be the same twice.

 

[fedorfan]

Are we evn sure there will be another big bang? Also, what do you mean by created, what created it?

 

[Chronos]

It is, by science as we know it, impossible to know what the initial conditions were during the big bang. It is entirely possible atoms, their constituents and the properties of spacetime itself might vary if initial conditions were altered, but, we don't live in those universes: so the question is not very interesting to me.

 

[fedorfan]

I see what youre saying, but would their be anything crazy like reverse gravity, perpetually making energy and matter, atoms being bigger than the earth, quarks being smaller than nothing(nothing as in it goes past being nothing and into some sort of negative size), or would it only be slightly altered like the speed of light changing, quarks being more numerous in protons and neutrons and being farther apart? Would they change in a big or small way? Or are the possibilities endless?

 

[DaveC426913]

Could be a big way. Possibilities are endless. The things you mention could happen. All ten dimensions could be macro-sized.

Unfortunately, 99.99% of configurations result in universes where nothing interesting can form - like even atoms - they'll be just formless, energized space. Or, you might get Earth-sized "atoms", but they can't form molecules.

This is why it appears our universe is exquisitely tuned. So many dials are set just so.

 

[Chronos]

Still, it more interesting to ask why our universe is so finely as to permit us observers to marvel at its mysteries. Dumb luck is always a possibility, but, not very satisfactory. I'm the devil's advocate, We all can agree our universe has these and those propoperties - but why?