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dapifo
2012-Nov-12, 10:19 PM
Please, could you write down the greatest enigmas in physics today?

Below write down some that come to my mind:

In large dimensions:

- Dark Energy and Dark Mass (we only know 5 % of the Our Known Universe)
- If the universe expands isotropically...then ... where does the Big-Bang start?
- How is it possible that Universe expand quicker than the light speed?
- What there was before the Big-Bang?

In small dimensions:

- What and where are produced the Force fields?
- Why Strong, Weak and EM Force fields are the same field at 10^-30 meters?

Reality Check
2012-Nov-12, 11:47 PM
Please, could you write down the greatest enigmas in physics today?

Below write down some that come to my mind:

In large dimensions:

- Dark Energy and Dark Mass (we only know 5 % of the Our Known Universe)
- If the universe expands isotropically...then ... where does the Big-Bang start?
- How is it possible that Universe expand quicker than the light speed?
- What there was before the Big-Bang?

In small dimensions:

- What and where are produced the Force fields?
- Why Strong, Weak and EM Force fields are the same field at 10^-30 meters?
"Dark Energy and Dark Mass" are not an enigma. They are observations.
"If the universe expands isotropically..." is not an emigma. The answere is everywhere
"How is it possible that Universe expand quicker than the light speed" is not an enigma (special realtivity applies to objects in space-time not space-time).
"What and where are produced the Force fields" is not an enigma. Basically charges and mass create fields.
"Why Strong, Weak and EM Force fields are the same field at 10^-30 meters" this is not an enigma - it looks like a mistake (citation please).

So basically you have one "enigma" : What there was before the Big-Bang?

As for your request - there are so many and opionions will vary on which is the "greatest" so there is no point in listing them.
Especially when there are existing lists, e.g. List of unsolved problems in physics (http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics)

Van Rijn
2012-Nov-12, 11:47 PM
- If the universe expands isotropically...then ... where does the Big-Bang start?


Everywhere. Metric expansion just means the universe becomes less dense.


- How is it possible that Universe expand quicker than the light speed?


Because metric expansion isn't limited to the speed of light. See:

http://www.astro.ucla.edu/~wright/cosmology_faq.html#FTL




- What there was before the Big-Bang?



I'd change that to:

Was there anything before the Big Bang?

Does "before" have meaning in this context?

Jens
2012-Nov-13, 12:11 AM
"Dark Energy and Dark Mass" are not an enigma. They are observations.


That seems fairly picky to me. If you rephrased it, what is dark matter? then I think we do have an important unsolved question in physics, that people are actively working to solve.

dapifo
2012-Nov-13, 12:30 AM
Canceled...see bellow post

dapifo
2012-Nov-13, 12:42 AM
"Dark Energy and Dark Mass" are not an enigma. They are observations.
"If the universe expands isotropically..." is not an emigma. The answere is everywhere
"How is it possible that Universe expand quicker than the light speed" is not an enigma (special realtivity applies to objects in space-time not space-time).
"What and where are produced the Force fields" is not an enigma. Basically charges and mass create fields.
"Why Strong, Weak and EM Force fields are the same field at 10^-30 meters" this is not an enigma - it looks like a mistake (citation please).

So basically you have one "enigma" : What there was before the Big-Bang?

As for your request - there are so many and opionions will vary on which is the "greatest" so there is no point in listing them.
Especially when there are existing lists, e.g. List of unsolved problems in physics (http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics)

Thanks for your link to wiki...it has been very interesting.

Answers to your answers and questions:

- This link propose Dark Energy and matter as enigmas
- How can you say that is no an enigma where was the Big-Bang (Everywhere???)...GOD??
- That Universe expand quicker than the light speed is not an enigma .. it is a need...but it is very strange...and not well explained...possible the enigma is why the speed of light is a limmit constant for Our Universe?
- And who , how and where are created the charges and mass ?...is it an enigma?
- citation please: "The Elegant Universe" chapter 7. http://commons.wikimedia.org/wiki/File:Convergenciafuerzas.jpg

speedfreek
2012-Nov-13, 01:02 AM
- How can you say that is no an enigma where was the Big-Bang (Everywhere???)...GOD??

If, at the Big-Bang, everywhere was at the same place, then the place where the Big-Bang happened was... everywhere.

ShinAce
2012-Nov-13, 01:13 AM
1) proton spin
2) matter antimatter asymmetry
3) quantum theory of gravity
4) neutrinos (I know that many people accept that they have putative masses and anti-particles, but this has not been directly observed)
5) high temperature superconductors (not a problem of existence, but a problem of understanding)

And then there's the wiki list:
http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics

My own personal problem is:
6) why thermodynamics is not time reversible while the laws of nature are

dapifo
2012-Nov-13, 01:34 AM
6) why thermodynamics is not time reversible while the laws of nature are

What do ou mean?... Why Entropy always is positive?

dapifo
2012-Nov-13, 01:35 AM
If, at the Big-Bang, everywhere was at the same place, then the place where the Big-Bang happened was... everywhere.

I agree...but where is it this point now?...we know when...how...but not where ...and why...

ShinAce
2012-Nov-13, 01:45 AM
What do ou mean?... Why Entropy always is positive?

I mean why the laws of physics make sense in both time directions, but thermodynamics doesn't.
http://en.wikipedia.org/wiki/T-symmetry

Jens
2012-Nov-13, 02:00 AM
2) matter antimatter asymmetry


I think this is really one of the big ones today.

dapifo
2012-Nov-13, 02:01 AM
I mean why the laws of physics make sense in both time directions, but thermodynamics doesn't.
http://en.wikipedia.org/wiki/T-symmetry

I donīt understand...the T-symmetry...Please, could you give to me some example (one of laws of physids and other of thermodynamics ?

Laws of Physics...speed ...you can go on and back?

Laws thermodynamics...only Entrpopy....doesīt?

ShinAce
2012-Nov-13, 02:09 AM
Two billiard balls colliding. Whether you look at the collision forward in time or backwards in time, it's the same laws. Conservation of momentum and kinetic energy. Whether I give you the initial velocities or the final velocities, you can solve for the missing one. In thermodynamics, you can't do that. I give you a box in thermal equilibrium and you can't say a darned thing about what it looked like before.

An electron going towards the right is the same as a positron going to the left, as far as charge is concerned. Huge debates have been had about whether power flows from the negative terminal on a battery to the positive, or vice versa. It doesn't matter, since it's symmetrical.

If you're really interested, you can look up time symmetry.

caveman1917
2012-Nov-13, 03:05 AM
Two billiard balls colliding. Whether you look at the collision forward in time or backwards in time, it's the same laws. Conservation of momentum and kinetic energy. Whether I give you the initial velocities or the final velocities, you can solve for the missing one. In thermodynamics, you can't do that. I give you a box in thermal equilibrium and you can't say a darned thing about what it looked like before.

That's also because you are removing the relevant information by presenting it as a thermodynamical box. If you present it as a full description of position and velocity of each molecule in that box one could certainly calculate how it looked like before. It would be the same as the billiard balls, just a lot of them.

pzkpfw
2012-Nov-13, 03:07 AM
... but where is it this point now? ...

In the middle of my head. I am the centre of the Universe.

(The centre of your head too, and you are also the centre of the Universe.)

Centre ends up meaning something different than what might be expected.

You won't find the "centre" of the Big Bang; there is no single "place" (as viewed in the current Universe) where it occured.

Van Rijn
2012-Nov-13, 03:12 AM
If, at the Big-Bang, everywhere was at the same place, then the place where the Big-Bang happened was... everywhere.
I agree...but where is it this point now?


Everywhere. The Big Bang is not an explosion in space, or an event that only happened in some part of the universe. Rather, it refers to the expansion of the entire universe. Just as the laws of physics appear to be the same everywhere we look, large scale expansion appears to be the same everywhere we look.

Perhaps this illustration will help you understand the idea:

http://www.astro.ucla.edu/~wright/infpoint.html

Cougar
2012-Nov-13, 03:16 AM
In general response to your title question, there's a book of answers, aptly named Unsolved Problems in Astrophysics. A little dated now - compiled back in 1997 by John N. Bahcall and Jeremiah P. Ostriker.


- Dark Energy and Dark Mass (we only know 5 % of the Our Known Universe)

As mentioned, you mean dark matter. Actually, that's three apparent "qualities" of our Universe that are pretty enigmatic, dark energy being the most so.


- If the universe expands isotropically...then ... where does the Big-Bang start?

Yes, that is certainly not ultimately solved. Should be added to the list, but the question need not be discussed in this thread, right?


- How is it possible that Universe expand quicker than the light speed?

I think it could certainly be said that inflation is not completely worked out. A lot of it has been that seems to fit together very well. But the period around 10-33 sec. after the "beginning" is not reachable with Earth-bound experiments.


- What there was before the Big-Bang?

I'm probably repeating former comments, but since we don't know whether there was a "before" or not, then the "enigmatic" question should be "Was there anything before the big bang?" (in which case there might not be a "before"). It's possible this question could remain an enigma forever.


- What and where are produced the [four] Force fields?

Or rather, was there any choice in the way these interactions happened to work out?

There are fairly advanced theories, or shall we say, proposed explanations, for many of these questions. Obviously, it's the unanswered questions that scientists are working on.

Cougar
2012-Nov-13, 03:19 AM
Rather, it refers to the expansion of the entire universe...

I'd just add, ...including all the space.

Jens
2012-Nov-13, 04:02 AM
That's also because you are removing the relevant information by presenting it as a thermodynamical box. If you present it as a full description of position and velocity of each molecule in that box one could certainly calculate how it looked like before. It would be the same as the billiard balls, just a lot of them.

But still, what SinAce is trying to say is that it seems a mystery that things seem to be T symmetric except for entropy. It's definitely an observation, I'm not really sure if it would qualify as an enigma. I mean, when you put two gases in a tank, and then remove the divider in the middle of the tank, it makes sense that they will mix up and not revert to their original separated state. So it doesn't seem particularly enigmatic to why it should happen.

ShinAce
2012-Nov-13, 04:18 AM
But still, what SinAce is trying to say is that it seems a mystery that things seem to be T symmetric except for entropy. It's definitely an observation, I'm not really sure if it would qualify as an enigma. I mean, when you put two gases in a tank, and then remove the divider in the middle of the tank, it makes sense that they will mix up and not revert to their original separated state. So it doesn't seem particularly enigmatic to why it should happen.

Maybe it makes sense to you, but it makes no sense to me. Physical laws are mathematically beautiful in their symmetries. Thermodynamics seems to violate this rule. I would much prefer that all laws had strong symmetries instead of most laws.

To me, it would make more sense if a hot spot in a box would oscillate about instead of being damped. But that's a desire, not reality.

But you definitely got the idea. It's a total mystery why physics is so easy to do with T symmetry while entropy is not.

Shaula
2012-Nov-13, 06:32 AM
- The precise details of the Higgs mechanism
- The application of the Higgs mechanism to fermions
- The Strong CP problem
- Why and how gluons apparently carry so much angular momentum
- The Vacuum energy prediction that drops out of QM
- Turbulence. Enough said.
- The Yang-Mills mass gap problem
- What is the relationship between S and T dualities in String theory and can we prove the S-duality extends through the full range of coupling constants?
- Does M theory actually exist and does it properly link the Type I and II supergravity and superstring theories across all energy scales?
- What does the low energy limit of LQG look like?

Ivan Viehoff
2012-Nov-13, 11:31 AM
"Dark Energy and Dark Mass" are not an enigma. They are observations.

I think that an observation which we find ourselves unable to generalise a law from to produce good predictions, is acceptably described as an enigma in science.

Dark energy is code for "the expansion of the universe is accelerating". It is an enigma because it is inconsistent with our laws of physics, and we cannot yet construct an alternative set of laws that works for it. Dark mass is likewise the observation that large scale structures in the universe appear, according to our understanding of gravity, to have much more mass than we can give a consistent explanation of. Again, we have been unable to devise laws of physics consistent with all of our observations.

HenrikOlsen
2012-Nov-13, 01:08 PM
For me, the greatest mystery is: why do people react to an "I don't understand mainstream physics" situation by concluding there's something wrong with mainstream physics?

Hornblower
2012-Nov-13, 01:47 PM
Maybe it makes sense to you, but it makes no sense to me. Physical laws are mathematically beautiful in their symmetries. Thermodynamics seems to violate this rule. I would much prefer that all laws had strong symmetries instead of most laws.
To me, it would make more sense if a hot spot in a box would oscillate about instead of being damped. But that's a desire, not reality.

But you definitely got the idea. It's a total mystery why physics is so easy to do with T symmetry while entropy is not.

My bold. All of us could say that until doomsday, but the universe is what it is and does what it does, and it does not care what we might prefer.

dapifo
2012-Nov-13, 03:09 PM
Everywhere. The Big Bang is not an explosion in space, or an event that only happened in some part of the universe. Rather, it refers to the expansion of the entire universe. Just as the laws of physics appear to be the same everywhere we look, large scale expansion appears to be the same everywhere we look.

Perhaps this illustration will help you understand the idea:

http://www.astro.ucla.edu/~wright/infpoint.html

OK..but you and this figure are suposing that the Whole Universe was already existing before the Big-Bang (that I agee)...but mainstream oesn. t. Mainstream supose that Universe start in the Big-Bang where nothing was before...and nothing is outside Our Universe.

But yes I also agree that we cannot see al Our Universe (78 billion light year )...and only a part of it (Known Universe) is observable (13.7 billion light year ).

dapifo
2012-Nov-13, 03:17 PM
It's a total mystery why physics is so easy to do with T symmetry while entropy is not.

Entropy is the basis ( and possible the origen) of the time...or vice versa. Time and Entropy are linked.

dapifo
2012-Nov-13, 03:24 PM
- The precise details of the Higgs mechanism
- The application of the Higgs mechanism to fermions
- The Strong CP problem
- Why and how gluons apparently carry so much angular momentum
- The Vacuum energy prediction that drops out of QM
- Turbulence. Enough said.
- The Yang-Mills mass gap problem
- What is the relationship between S and T dualities in String theory and can we prove the S-duality extends through the full range of coupling constants?
- Does M theory actually exist and does it properly link the Type I and II supergravity and superstring theories across all energy scales?
- What does the low energy limit of LQG look like?

All these concepts cannot be considered as enigmas of physics or of the Universe.

They are enigmas of the current physics models and patterns...that is very different...They are concepts that scientifics hold to explain the universe...but they are not an enigma in themselve): Higgs, Strog CP, Gluons, Yang-Mills, S and T dualities, M-Theory, LQG.

Possible the unics could be the essence of Vacuum and Turbulences.

dapifo
2012-Nov-13, 03:29 PM
For me, the greatest mystery is: why do people react to an "I don't understand mainstream physics" situation by concluding there's something wrong with mainstream physics?

I donīt think that anybody could say this...but yes that "if there are some insolved problems within mainstream...possibly it is not absolutly closed and could be changed"

Shaula
2012-Nov-13, 04:32 PM
All these concepts cannot be considered as enigmas of physics or of the Universe.

They are enigmas of the current physics models and patterns...that is very different...They are concepts that scientifics hold to explain the universe...but they are not an enigma in themselve): Higgs, Strog CP, Gluons, Yang-Mills, S and T dualities, M-Theory, LQG.

Possible the unics could be the essence of Vacuum and Turbulences.
By your standards neither are any of yours then.

Dark Energy and Dark Mass
- Model to fit observations.

If the universe expands isotropically...then ... where does the Big-Bang start?
- Big Bang is a model - and strictly speaks it includes no bang

How is it possible that Universe expand quicker than the light speed?
- A consequence of the cosmological model used and more fundamentally a feature of the model that includes cosmic expansion

What there was before the Big-Bang?
- Model dependent again

What and where are produced the Force fields?
- the fields are models

Why Strong, Weak and EM Force fields are the same field at 10^-30 meters?
That is modelled, we have never seen that happen

So sorry but pretty much everything you mentioned is model dependent. If you want to get away fro that you should have asked "What are the most enigmatic observations" or something similar.

dapifo
2012-Nov-13, 05:24 PM
Yes...you are right....Every thing is a model...Our Universe is a model....Energy, matter are only models to explain observations....

Possible what I mean is that your enigmas are too focussed on solving the details of the models....and I proposed and ask more for main enigmas to solve coceptual problems of the current theories and models.

Eg M-Theory is not an enigma...it is a modeling problem...that try to explain the current observations by only one model...and not several as now.

Well I recognize that is dificult to distinguish between reality (observations) and model (observations modeling).

ShinAce
2012-Nov-13, 05:26 PM
By your standards neither are any of yours then.

So sorry but pretty much everything you mentioned is model dependent. If you want to get away fro that you should have asked "What are the most enigmatic observations" or something similar.

Absolutely correct.

To the ancients, the motions of the planets defied understanding. Now we have a model(gravity) that explains their motions in the sky. Physics is all about models.

Don't throw out the baby with the bath water.

Shaula
2012-Nov-13, 05:38 PM
Possible what I mean is that your enigmas are too focussed on solving the details of the models....and I proposed and ask more for main enigmas to solve coceptual problems of the current theories and models.
You should have said so then - I would not have replied. Mainly because I am pretty sure that most progress will be made by looking at where these models fail in detail.

ShinAce
2012-Nov-13, 05:45 PM
Absolutely correct again!

When scientists like Lorentz were trying to fix the model of kinematics, it lead to a profound revolution in the understanding of spacetime.

It's almost impossible to understand what you don't understand. We can't always guess correctly which fundamental part of physics has been misunderstood and work from there. Most of the time, we have to work backwards. If we knew exactly which parts didn't work, don't you think we would have fixed them by now?

Van Rijn
2012-Nov-13, 07:31 PM
OK..but you and this figure are suposing that the Whole Universe was already existing before the Big-Bang

:confused: Uh, no, I was most definitely not supposing the universe existed before the Big-Bang, nor did that figure suggest any such thing (the figure was to help you visualize how expansion in mainstream Big Bang cosmology works). Incidentally, if you look at my first post in thread, I commented that one of your questions should be changed to "Was there anything before the Big Bang?" with the follow-up 'Does "before" have meaning in this context?"

Oh, and I would strongly recommend you read the cosmology faq that figure came from:

http://www.astro.ucla.edu/~wright/cosmology_faq.html

It's a good short introduction and covers many common misconceptions (as you seem to have). By the way, another page there discusses the age of the universe:

http://www.astro.ucla.edu/~wright/age.html

. . . and has quite mainstream numbers.

dapifo
2012-Nov-13, 08:04 PM
Really this Wiki list is very good...and cover most and more of the enigmas we talk about...

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

ShinAce
2012-Nov-13, 10:36 PM
You mean the same link I posted 28 posts ago?

Great! Pick your ten favourite and the thread is complete!

dapifo
2012-Nov-14, 12:46 AM
You mean the same link I posted 28 posts ago?

Great! Pick your ten favourite and the thread is complete!

Yes ...yours and Reality Check inthe second post....thanks