What the field of physics knows it doesn't know.

[Ubi]

Can people confirm the following statement is true, or provide links that explain otherwise:

"The laws of the universe appear to be ubiquitous and work isotropically, they appear to move around with the things that they govern, the field of physics cannot explain the mechanics of this phenomena."

Thanks!

 

[Vanadium 50]

You'll have to tell us where it comes from.

 

[ZapperZ]

Can people confirm the following statement is true, or provide links that explain otherwise:

"The laws of the universe appear to be ubiquitous and work isotropically, they appear to move around with the things that they govern, the field of physics cannot explain the mechanics of this phenomena."

Thanks!

You are required to provide an exact reference to the source. You simply cannot quote something and not give us that info.

Secondly, before you decide to do that, please re-read the PF Rules that you had agreed to. Pay attention to what is allowed to be discussed here. If this is from a personal webpage or a dubious (crackpot?) source, then those cannot be discussed in this forum. Period.

Zz.

 

[tiny-tim]

perhaps you're thinking of:

… there are no "knowns." There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know.​

(http://en.wikiquote.org/wiki/Donald_Rumsfeld)

​

 

[Ubi]

Hmm, I suspected my question might be a bit minimal, a brief explanation of my motivation. There are things we know about the universe, there are documentaries and such that explain these topics. I am interested in putting something together about what we don't know, as its less done and I think it is as interesting as what we do know!

If anybody knows of a website that lists things we have yet to explain in physics, that would be very interesting. The basic idea is that as new generations of physicists emerge they will want to know what we don't know as well as what we do, this is especially true once they mature.

As regards where the statement come from, I made it, but it is common knowledge right?

Take gravity, our planet is moving around the sun, and the gravity that keeps us on the surface is moving around with the planet, hence gravity is ubiquitous and works isotropically. It's a fact.

As to the field of physics not being able to explain the mechanics of this phenomena, this is to the best of my knowledge and I am fairly confident it is the case, hence asking the question.

For example, we know the universe 'has' gravity, we just don't know 'why' it has gravity.

There is no forum for the philosophy of physics, so general looked like the right place.

 

[Crazymechanic]

Well gravity is a property of mass , wherever there is mass there will be gravity.
Gravity is not itself like a totally new person which walks around and keeps someone attached to Earth like a paperclip attaches a paper to something rather the paperclip and the paper and the thing those are attached to are all objects made out of matter which has mass and mass gravitates so they tend to attract each other , and we tend to attract more to Earth than to one another just because Earth is so much bigger and heavier than all the other things thus having much bigger gravity.

 

[ZapperZ]

Hmm, I suspected my question might be a bit minimal, a brief explanation of my motivation. There are things we know about the universe, there are documentaries and such that explain these topics. I am interested in putting something together about what we don't know, as its less done and I think it is as interesting as what we do know!

If anybody knows of a website that lists things we have yet to explain in physics, that would be very interesting. The basic idea is that as new generations of physicists emerge they will want to know what we don't know as well as what we do, this is especially true once they mature.

As regards where the statement come from, I made it, but it is common knowledge right?

Take gravity, our planet is moving around the sun, and the gravity that keeps us on the surface is moving around with the planet, hence gravity is ubiquitous and works isotropically. It's a fact.

As to the field of physics not being able to explain the mechanics of this phenomena, this is to the best of my knowledge and I am fairly confident it is the case, hence asking the question.

For example, we know the universe 'has' gravity, we just don't know 'why' it has gravity.

There is no forum for the philosophy of physics, so general looked like the right place.

Please reread you self-made quote and see why it makes no sense.

If gravity defies our understanding of mechanics, then how are we able to use it and make such accurate astronomical predictions?

Zz.

 

[Ubi]

Let me give another example, we can go anywhere in the world and light a fire basically getting the same results, this is because the laws of the universe are ubiquitous (everywhere) and work isotropically (in any direction).

The question is, why is this the case? When Stephen Hawking was asked this question, I believe he said 'its just the way it is'.

Hence, to the best of my understanding, we don't understand why we have the laws we do, we only know we have them and that we can model them mathematically.

I am confident this is the case and I just looking for confirmation (actually I don't mind being told its not the case if I get more information on why). By putting my original question in quotes I maybe gave the wrong impression, it is not a quote, its just a question.

Thanks for the replys.

 

[richlyblessed]

What is unknown, once discovered always creates unknown. This being said, requires a direct look at cause and effect to infinity. Since time to man is linear, we can only chase the cause and effect until we discover the unknown, which points us into the unknown. Everything finite has a place located in the known and unknown. Just as a coin spinning on its axis spins by force, so does the effort to find every cause and effect of a known, the force of the discovery brings new spin to the search for the unknown. Every discovered unknown begets the force to find the next unknown.

 

[dkotschessaa]

Hence, to the best of my understanding, we don't understand why we have the laws we do, we only know we have them and that we can model them mathematically.

This is usually answered anthropically. We have the laws we have, because if we had different laws (one that didn't allow the universe to exist) then we wouldn't be here to ask why we have the laws we have.


See: http://en.wikipedia.org/wiki/Anthropic_principle

-Dave K

 

[phyzguy]

Hence, to the best of my understanding, we don't understand why we have the laws we do, we only know we have them and that we can model them mathematically.

These 'why' questions can never really be answered. Any attempt at an answer just leads to the question, "But why is THAT?". At some point a set of axioms or assumptions is needed in order to start the chain of logical reasoning.

 

[The_Duck]

Let me give another example, we can go anywhere in the world and light a fire basically getting the same results, this is because the laws of the universe are ubiquitous (everywhere) and work isotropically (in any direction).

Physicists usually discuss this fact by talking about "symmetries." We say that the laws of physics have translational and rotational symmetry, or equivalently that they are translationally and rotationally invariant. They won't notice if you translate your experiment 5 feet to the left, or rotate it by 30 degrees. Symmetries play a deep and fundamental role in physics. For example, every symmetry gives rise to a conserved quantity. For instance, the fact that the laws of physics are translationally invariant leads to the conservation of momentum.

The question is, why is this the case?

We don't know. (If you keep asking "why?" in science you will always run into this answer eventually).

The modern approach to particle physics is basically to postulate a certain set of symmetries--including translational and rotational symmetry--as a starting point, and then derive everything else from those.

 

[dkotschessaa]

These 'why' questions can never really be answered. Any attempt at an answer just leads to the question, "But why is THAT?". At some point a set of axioms or assumptions is needed in order to start the chain of logical reasoning.

Yes, scientifically "why" questions have no meaning at all. Philosophically they might not ultimately be answerable, as you've stated, though they can lead to other areas of inquiry that might be helpful.

Or not.

-Dave K

 

[technician]

Phyzguy has hit the nail on the head.
Physics answers 'what' and 'how' questions.
'Why' questions are answered somewhere else.
Ultimately someone will give the answer to 'why...' As ... 'because God wills it to be so'

 

[mrspeedybob]

These 'why' questions can never really be answered. Any attempt at an answer just leads to the question, "But why is THAT?". At some point a set of axioms or assumptions is needed in order to start the chain of logical reasoning.

Asking why a particular axiom is true may however lead to an understanding that reduces the number of necessary axioms. Physicists of the past were not content to measure and quantify the properties of each element and take these properties to be fundamental. They asked why questions. Why does Helium behave similarly to Neon but completely different from Lithium? Answering these "why" questions lead to our modern understanding of the atom and of quantum mechanics.

At some point in the future someone struggling to answer the question "Why does the electro-weak interaction behave the way that it does?" may discover a way to describe the electro-weak interaction in terms of X. Then they will discover that gravity can also be explained in terms of X and then gravity and the electro-weak interaction will be unified under the new theory X. This will of course raise the question "Why X?" but it would have reduced the number of axioms necessary to explain the universe.

I believe that explaining things with the smallest possible number of axioms is a worthwhile pursuit, therefore I see "why" as a worthwhile question, at least until we can build a complete model of physics on 1 axiom.

 

[BruceW]

The question is, why is this the case? When Stephen Hawking was asked this question, I believe he said 'its just the way it is'.

Hence, to the best of my understanding, we don't understand why we have the laws we do, we only know we have them and that we can model them mathematically.

Take the 'cup is half full' attitude. Physicists are always trying to reduce the number of unanswered 'why' questions. For example, electricity and magnetism were modeled as two separate phenomena. So in a sense, we had two 'whys'. but now they are modeled as one electromagnetic phenomena. This is only one 'why', so physicists have decreased the number of 'whys'. Another example, if we have two different theories to explain the same phenomena, then we will choose the theory which has the least number of fundamental physical constants, or the one with the least number of fine-tuned parameters. Therefore, we are reducing the number of 'whys'.

 

[micromass]

There are many excellent answers here. But I think the best explanation I've heard about science and "why-questions" is of course by Feynman.

https://www.youtube.com/watch?v=GqTvGLVwnQ4

In this video Feynman explains extremely well what science is about and not about. I recommend you to watch it very carefully. No need to watch the previous videos to understand this one (although I do recommend watching the entire lecture once).

 

[CWatters]

Hmm, I suspected my question might be a bit minimal, a brief explanation of my motivation. There are things we know about the universe, there are documentaries and such that explain these topics. I am interested in putting something together about what we don't know, as its less done and I think it is as interesting as what we do know!

Every now and again someone will write an article like this one from 2002..

The 11 Greatest Unanswered Questions of Physics
http://discovermagazine.com/2002/feb/cover

I'll let you figure out which if any have been answered since 2002.

 

[mfb]

For less philosophical questions: List of unsolved problems in physics

 

[BruceW]

Every now and again someone will write an article like this one from 2002..

The 11 Greatest Unanswered Questions of Physics
http://discovermagazine.com/2002/feb/cover

I'll let you figure out which if any have been answered since 2002.

I know 4's been answered! hehe. Sorry, your post was probably aimed toward Ubi, but I couldn't help myself.

 

[Ubi]

Thanks for the replies.

This 'why' question can be asked in a 'how' way, such as 'how is the universe enforcing its laws', and it is worthy of some consideration. I would like to ask another question, a more specific one than the first. The laws of the universe are ubiquitous and isotropic, or as physicsts put it, translationally and rotationally invariant.

In layman terms it means 'the laws of the universe move around as much as the things they govern'. But this is a little abstract, if you look at what is going on, the laws of the universe are moving around not only as 'much' as the things they govern, they are in fact moving around 'with' the things that they govern.

Now my question is, taking gravity for an example; is gravity effecting the things it governs, as it appears to do by keeping us on the surface of the planet, or is gravity effected by the things that it governs, as it appears to (and this may be my mistake) be in relativity when the mass of a planet bends spacetime?

Thanks.

 

[Vanadium 50]

In layman terms it means 'the laws of the universe move around as much as the things they govern'.

No, it doesn't. That sentence is certainly not established science, and I doubt very much that it means anything whatsoever.

 

[Ubi]

No, it doesn't. That sentence is certainly not established science, and I doubt very much that it means anything whatsoever.

The force of gravity, which is keeping me on the surface of the planet, is moving through space with the planet. Are you saying gravity does not move around with the planet?

Established science? I am pretty sure it's basically a self evident fact!

 

[mfb]

The force of gravity of some object is not a physical law. The object can move around, while the law does not. Gravity is acting on all objects everywhere, there is nothing to "move around".

 

[ZapperZ]

The force of gravity, which is keeping me on the surface of the planet, is moving through space with the planet. Are you saying gravity does not move around with the planet?

Established science? I am pretty sure it's basically a self evident fact!

You are now tripping over yourself.

The law that describes gravity doesn't change, as far as we know. While gravity itself may vary from location to location, and with time, how gravity is described remains the same!

I've read this whole thread, and there is a really fundamental misunderstanding of NOT gravity, but rather what is meant by a theoretical description of a physical law.

Zz.

 

[Ubi]

I am not getting this, a force called gravity keeps me on the surface of the planet, as I move through space on the surface the force is constantly changing direction to keep me there. To the person experiencing this it appears as if the force is moving. If it stayed in the same place for example, the planet would move away from it.

So I will try and understand it another way, let's say the laws don't move around, but the way in which they act does?

How can the force of gravity be static when it is dynamic (in that it is translationally and rotationally invariant)?

 

[BruceW]

The law that describes gravity doesn't change, as far as we know. While gravity itself may vary from location to location, and with time, how gravity is described remains the same!

that.

Now my question is, taking gravity for an example; is gravity effecting the things it governs, as it appears to do by keeping us on the surface of the planet, or is gravity effected by the things that it governs, as it appears to (and this may be my mistake) be in relativity when the mass of a planet bends spacetime?

yes, both. The gravitational 'field' determines how matter moves, and matter determines the form of the gravitational field. Note that the laws of gravity do not change, it is only the values of the gravitational 'field' that change. p.s. I have used scare-quotes around 'field' because in general relativity, that is not really proper terminology, but you know what I mean loosely.

 

[BruceW]

How can the force of gravity be static when it is dynamic (in that it is translationally and rotationally invariant)?

Ah, but it won't be translationally invariant if you are standing on the earth. The laws of gravity will be translationally invariant, but the actual values of the field are not necessarily going to be. In a (sort of) similar way, the distribution of matter is not translationally invariant, but the laws for momentum are.

 

[ZapperZ]

I am not getting this, a force called gravity keeps me on the surface of the planet, as I move through space on the surface the force is constantly changing direction to keep me there. To the person experiencing this it appears as if the force is moving. If it stayed in the same place for example, the planet would move away from it.

So I will try and understand it another way, let's say the laws don't move around, but the way in which they act does?

How can the force of gravity be static when it is dynamic (in that it is translationally and rotationally invariant)?

When we go to the moon, did the equation describing gravity changed?

Zz.

 

[Ubi]

The gravitational 'field' determines how matter moves, and matter determines the form of the gravitational field.

I think this is what I am looking for, just to make clear, this means the state of one can effect the state of the other and vice versa?

 

[BruceW]

I'm not sure that 'effect' is really the right word. I mean we have Einstein's field equations which contain terms related to the field and terms related to energy, momentum e.t.c. So maybe it is better to say that knowledge of the field tells us about what matter is doing and vice versa.