A Couple More Random Questions

[TheGeckomancer]

Forewarning, some of what I am going to say is speculative, but I am not postulating any of it's true, it's for the purposes of my questions. Regardless, if I rant too much feel free to move this thread.

 

1. Does anyone else have a problem with sharing "space" mentally between the concepts of locality and infinity? To me, the two ideas seem almost mutually exclusive. In an infinite universe the theory of locality implies that there are flat out information disconnects throughout the universe, because you can have empty regions of space so large, the expansion rate is faster than light and no information enters the region or leaves. Places where no information is or ever will be exchanged, and technically everywhere is one of those points to a ton of places. But this creates crap-ton of problems to me. For one, it means we would never actually be able to know if the universe was consistent, only the parts we observe. It would also imply there are things, that exist, that we cannot ever know about. I hope this idea made enough sense to follow, I actually thought about this question all day and couldn't think of a good way to express my thoughts on it. I hope this worked.

 

2. So, I posted on a topic recently explaining to someone else about vacuum energy, or one facet of it anyway. Specifically the pairs of virtual particles that come into existence and annihilate. I have been wondering, couldn't a space be created of intense vacuum pressure, designed to coax these pairs into existence, with electromagnetic shunts basically that funnel them away from each other to prevent annihilation. If so, could work be extracted from this at any point in any meaningful way. As soon as I went to pose this question, I decided to google search first and found a ton of people talking about this, guess some refer to it as zero point energy. I feel I have a pretty solid grasp of physics. To me this idea is sound. HOWEVER, I also know the implications of what this means if it's true. My bet is I am overlooking something, if it seems too good to be true it probably is. It also occurred to me that it may be possible without actually being practical, such as the energy required to operate the system being greater than energy extracted. I would love to hear some people more knowledgeable about this, and if anyone has any some links to credible sources. This is in the perpetual energy category which means I KNOW google searches will just yield quackery which is why I didn't dig too deep.

 

3. I read a really interesting thought experiment posed by someone, not sure if it was on this forum a couple months ago. And it's been swirling around in my head. It was a way of proving there is no minimum unit of time. The idea was you find the minimum unit of time called T, you create a device that can accelerate to .9C in one T, and you have a person outside the device time your travel for one T, at the end of which you are supposed to come to a complete stop. The values won't line up, you will always end out of time with each other. He explained it a lot better than me, and if anyone cares I will TRY to find it, no guarantees. I was wondering if any similar thought experiment could be constructed to establish if there is, or is not, can, or cannot be a minimum value of space. This is a question I think about a lot. Because to me it's an interesting indicator on if we are a computer simulation or not. If we can find the pixel, as it were. The problem is from a programming perspective, I know you could always design the largest interactive pieces of a world to be too large to observe the smallest components. But IF the universe is a simulation then space IS quantized at some point, whether we can ever observe that point is a totally different question. I think the idea that there is no minimum time value has interesting implications for space, but I don't fully understand them, and if someone else wants to take a crack at it I would not object.

 

4. This question is somewhat related to the third. I have trouble with certain properties of space. The biggest one being, it is SOMETHING, it's not nothing, but what is it? I have read some articles suggesting it may be a fluid or sorts, but these articles were very dubiously sourced. Also, does space have friction as an inherent property? I know it would have to be CLOSE to 0 but is it ACTUALLY 0 and do we have a way to tell? And is space MADE of something? I sincerely doubt it has smaller components, but as far as I can tell it doesn't have larger components either, but it can also grow. I hope other people find this confusing too... Also, if space is matter then how can other things occupy it at the same time or nothing? Can other things have any of the same properties as space?

 

I have a couple other questions I will post in separate threads because they DEFINITELY fall outside of physics, these questions totally stretch the topic as it is.

Edited December 6, 2015 by TheGeckomancer

[MigL]

1- I believe I speculated on this in your other thread 'Introductory Question'.

A causal ( information ) disconnect at any time, past and present, leads to failure of the isotropic principle, on which much of modern cosmology is based.

It leads to different 'domains' of our universe, with differing expansions/properties; Which I don't particularly like.

I tend to use it as an argument against an infinite universe, but it doesn't really convince me.

 

2- If you're going to 'borrow' energy from the universe to create a virtual particle pair, and then separate them using electromagnetic means ( for anti-particles of opposing charge ), you will in fact create real particles. But the universe still wants its energy back, and it will take it from the apparatus used to separate the virtual particles. The net effect is that the apparatus supplies the energy for the 'creation' of these particles.

This is basically the mechanism for Hawking radiation, where the apparatus is the Black Hole ( and gravity is the means ).

 

3- At small separations where you would expect this effect, time and energy are related by the Uncertainty Principle. Measuring time that accurately results in an extremely large uncertainty, or fuzziness, of the energy you measure. Energy and speed are related through momentum, so effectively, in that extremely brief ( and accurate ) time slice, you CANNOT know the speed.

( remember to throw all common, everyday sense out the window when dealing with the quantum world )

 

4- All depends on what your definition of 'space' is.

Edited December 6, 2015 by MigL

[TheGeckomancer]

Thank you. Those answers were very informative. For point 2, I kind of figured there would not be a net gain. Point 3, I am not sure I fully understand the relevance to my question, I am asking about space, I just used the time thought experiment as an example. Point 4, space is the place things can exist and move through, when I try to imagine nothingness I usually imagine no space or time, well try to imagine anyway.

 

MigL on point 1 I do remember you talking about this somewhat. I didn't realize my questions would roll back into that, I didn't even know about the isotropic principle. I just know information disconnects seem fundamentally paradoxical and wrong, seriously it upsets me to try to imagine a universe like that. With that kind of a universe you could have huge sections of the universe where magic is the physics and unicorn blood powers starships..... It actually really bothers me to think about that lol. It would also mean everything we know about the universe is fundamentally wrong and only locally right. Which is also really upsetting. And we would NEVER BE ABLE to know what is fundamentally right. But it would be a nice omniverse in universe concept.

Edited December 6, 2015 by TheGeckomancer

[swansont]

 

2- If you're going to 'borrow' energy from the universe to create a virtual particle pair, and then separate them using electromagnetic means ( for anti-particles of opposing charge ), you will in fact create real particles. But the universe still wants its energy back, and it will take it from the apparatus used to separate the virtual particles. The net effect is that the apparatus supplies the energy for the 'creation' of these particles.

This is basically the mechanism for Hawking radiation, where the apparatus is the Black Hole ( and gravity is the means ).c

 

 

Also related is the dynamic Casimir effect

[MigL]

For No.3 the point I was trying to make is that if T is small enough and accurate enough, how would you know you are at 0.9c, or at rest for that matter.

Plug in some numbers for a particular particle of a specific mass; a Planck time unit in the HUP leads to a sizeable uncertainty in the energy, from which you can establish the uncertainty in speed ( for that mass ).

[Strange]

For one, it means we would never actually be able to know if the universe was consistent, only the parts we observe. It would also imply there are things, that exist, that we cannot ever know about.

 

Correct. Which is why we use things like the cosmological principle. We assume (a working assumption) that the universe beyond what we can see is largely the same as what we do see. Now it is entirely possible that immediately outside the observable universe, everything is made of chocolate. But that is a far less useful assumption. So we stick with the simpler one, which allows us to make models of the universe.

 

 

4. This question is somewhat related to the third. I have trouble with certain properties of space. The biggest one being, it is SOMETHING, it's not nothing, but what is it?

 

I don't think there is any reason to think it is "something". It is the distance between things. (I think this is called the "relational" interpretation of space-time).

[TheGeckomancer]

My problem with this is there is not VOID between things. Space is a thing. And space cannot just be the distance between things because it has a fabric that can be warped by gravity.

Edited December 6, 2015 by TheGeckomancer

[Strange]

My problem with this is there is not VOID between things.

 

In relativity it is. (Obviously, once you consider quantum effects, that void is filled with fields, energy, and virtual particles.)

 

Space is a thing.

 

Is it?

 

And space cannot just be the distance between things because it has a fabric that can be warped by gravity.

 

That "fabric" is a metaphor. And a rather misleading one, apparently. What is warped is the geometry of those measurements. (And note that space-time is not warped by gravity, rather the curvature of space-time is what we experience as gravity.)

[TheGeckomancer]

But how does "not a thing" have a curvature for us to experience? Geometry of measurements is abstract, if thats all that were warping we would not experience anything, unless math is a real part of the world. You are DESCRIBING what way space is being warped. Space is being warped.

[Strange]

But how does "not a thing" have a curvature for us to experience?

 

Hmmm.... I sort of see what you mean. But if you have a straight line between two objects, is that straight line a "thing"? If you have three objects, is the triangle that joins them a "thing"?

 

And if you add the angles of that triangle and find it comes to exactly 180˚ is the Euclidean nature of that triangle a "thing"?

 

But if you add the angles of that triangle and find it comes to less than (or more than) 180˚ is the non-Euclidean nature of that triangle a "thing"?

 

Ultimately, the geometry of space-time is about the relationships between events in space-time and how they are changed by the presence of mass-energy.

 

This is a useful introduction: http://math.ucr.edu/home/baez/einstein/

 

Geometry of measurements is abstract, if thats all that were warping we would not experience anything, unless math is a real part of the world. You are DESCRIBING what way space is being warped. Space is being warped.

 

But all GR (and science in general) can do is describe. It sounds like you are asking about some sort of underlying reality. But that is outside the domain of physics; it is more of a philosophical question.

 

There is another thread where a poster asked if gravity can be explained by space "falling". And (in some cases, at least) it can be. So you could say that the "curvature" of space-time is just an interpretation of what is going on. Do we know (or can we ever know) what is "really" going on? Maybe not. All we can do is come up with better descriptions.

[TheGeckomancer]

 

Hmmm.... I sort of see what you mean. But if you have a straight line between two objects, is that straight line a "thing"? If you have three objects, is the triangle that joins them a "thing"?

 

And if you add the angles of that triangle and find it comes to exactly 180˚ is the Euclidean nature of that triangle a "thing"?

 

But if you add the angles of that triangle and find it comes to less than (or more than) 180˚ is the non-Euclidean nature of that triangle a "thing"?

 

Ultimately, the geometry of space-time is about the relationships between events in space-time and how they are changed by the presence of mass-energy.

 

This is a useful introduction: http://math.ucr.edu/home/baez/einstein/

 

 

But all GR (and science in general) can do is describe. It sounds like you are asking about some sort of underlying reality. But that is outside the domain of physics; it is more of a philosophical question.

 

There is another thread where a poster asked if gravity can be explained by space "falling". And (in some cases, at least) it can be. So you could say that the "curvature" of space-time is just an interpretation of what is going on. Do we know (or can we ever know) what is "really" going on? Maybe not. All we can do is come up with better descriptions.

 

 

All of the geometric examples you gave are abstract concepts. We experience, live in, and move through 3 dimensional space. This is what I am not understanding. "the geometry of space-time is about the relationships between events in space-time" this is like a word describing itself. I am not really looking for an underlying reality just a simple fact. We look at everything and we ask what is it. Space is not nothing, cause when any of us get told to imagine nothing we don't imagine space. We can also imagine being trapped in a small closet vs being outside. How can you have more of "not a thing" or less of "not a thing"? Do the fish think water is nothing or just empty space?

[Strange]

"the geometry of space-time is about the relationships between events in space-time" this is like a word describing itself.

 

You missed off an important part of that sentence.

 

All I can say is that GR describes what happens. What you are interested in is not (currently) part of science.

 

There are theories where space-time is an emergent phenomenon from some "lower-level" theory (e.g. causal dynamical triangulation). But that just shifts your question to what is that lower level model "really" made of. So I can't help feeling this line of questioning is ultimately futile.

Edited December 7, 2015 by Strange