...the size of the Universe would compress to zero -- in the direction of travel.

Edit: and no matter how long or far you traveled, you would always be at your starting point.

Well light travels at the speed of light all the time and the universe's size doesn't shrink...forget about "us" travelling and think only of a ray of light.

 

Well light travels at the speed of light all the time and the universe's size doesn't shrink...forget about "us" travelling and think only of a ray of light.

https://forum.allaboutcircuits.com/...ng-in-a-black-hole.143342/page-2#post-1233348

 

https://forum.allaboutcircuits.com/...ng-in-a-black-hole.143342/page-2#post-1233348

Yes, so lets remove that subjective aspect and consider a ray of light travelling through space. In a hypersphere model it could return to it's starting point (neglecting deflections and so on).

Cosmologists are unsure if the curvature is > 0 or < 0 or = 0, but if > 0 then a hypersphere is what we get.

 

Yes, so lets remove that subjective aspect and consider a ray of light travelling through space. In a hypersphere model it could return to it's starting point (neglecting deflections and so on).

Cosmologists are unsure if the curvature is > 0 or < 0 or = 0, but if > 0 then a hypersphere is what we get.

Cosmologists are unsure of lots of things.

 

Cosmologists are unsure of lots of things.

Yes, they're just like all the rest of us.

 

Which, in my understanding, means "there's either a physical (and theoretical) infinite, or there isn't" ... my personal opinion is that we're living in a finite universe, defined by a finite number of fundamental laws ... and I simply don't believe in a so-called "multiverse" mainly because: 1.- It's just a mathematical quirk, and 2.- By definition, the other universes would be so completely isolated from each other as to be inaccessible, so it would be just the same as if they wouldn't exist.

Hi,

Well see again we run into that "current knowledge" conundrum.
Is current knowledge the most knowledge we will ever possess. Are current measurements the best we will ever possess.
In order to take a solid stance on there being no other universes simply because we have not measured them yet, you'd have to believe both of those statements completely.
When we add to that the FACT that physics and cosmology are always advancing, it's impossible to believe that. It's only possible in the temporal sense.

The way knowledge and understanding works is very tricky. Even the famous musician Louis Armstrong had some idea about this. He said, "If you have to ask what Jazz is, you'll never know."

 

It's a Steven Hawking thing.

"Most people, Hawking writes, would find this cosmology ridiculous, but if we take the turtles as symbols of more and more fundamental laws, the tower is not so absurd. There are two ways to view it. Either a single turtle is at the bottom, standing on nothing, or it’s turtles all the way down. Both views are held by leading physicists."

That's cute and kind of funny about turtles.
Mexicans always complain about turtles in their vaginas...

 

I truly don't know what you are upset about.

I answered your question about a relativistic universe in a thread strongly influenced by relativity theory in the best way I could using what little knowledge I have about relativity and its effect on the overall size of the Universe.

Your thought experiment -- how many Earths can fit in the Universe? -- is an interesting question. When you apply relativity (and quantum mechanics) to the question, the answer is the same as "How many licks does it take to get to the Tootsie Roll center of a Tootsie Pop?": "The world may never know."

Or, "Three."

It's just that you seem to be not able to see what they sometimes say is the Forest for the Trees. You cant' see the simple truth, at least not in this matter.
For an illustration, if this might help, I could have already considered your reply yet still stated the same test: fit a number of Earths into the existing Universe when we consider the Universe to be of a size that is most talked about these days. That of course means we don't let the Universe expand when we fit imaginary Earths into it, and this is of course an imaginary experiment of sorts.

Surely if you had a large box that was in the shape of an ellipsoid, you could fit a number of basketballs into it, and it would be a limited number.
Using this idea let's rephrase the experiment...
Using a box that has the current estimated volume of the Universe scaled down to some manageable size, fill it with balls that are scaled down from the sized of the Earth by the same factor. How may balls does it take.

This was not really supposed to be a direct mathematical or cosmological question anyway. It was simply a way to think about how huge the universe is using a reference to something we have at least some idea what size it is and have some rough experience with that. I hesitate to use golf balls or turtles

 

Yes, they're just like all the rest of us.

I used this quote in another post...

The way knowledge and understanding works is very tricky. Even the famous musician Louis Armstrong had some idea about this. He said, "If you have to ask what Jazz is, you'll never know."

 

The universe is (if I recall) regarded roughly as a "sphere" but with a 3D surface not a 2D surface (leaving time aside for the time being) so it has no boundary in the sense the surface of a ball has no boundary Despite the absence of any boundary, a ball nevertheless has a finite surface area and by analogy "space" has a finite volume.

In principle, if we were to travel at the speed of light (well any speed really I suppose) we'd eventually return to our starting point, much as we would if we followed a geodesic path on the surface of a ball.

For all we know, one of the stars we can see in the remotest part of the sky, is our own sun!

That's funny to think about. I wonder if there is any proof of this curvature of sorts.

 

It's just that you seem to be not able to see what they sometimes say is the Forest for the Trees. You cant' see the simple truth, at least not in this matter.
For an illustration, if this might help, I could have already considered your reply yet still stated the same test: fit a number of Earths into the existing Universe when we consider the Universe to be of a size that is most talked about these days. That of course means we don't let the Universe expand when we fit imaginary Earths into it, and this is of course an imaginary experiment of sorts.

Surely if you had a large box that was in the shape of an ellipsoid, you could fit a number of basketballs into it, and it would be a limited number.
Using this idea let's rephrase the experiment...
Using a box that has the current estimated volume of the Universe scaled down to some manageable size, fill it with balls that are scaled down from the sized of the Earth by the same factor. How may balls does it take.

This was not really supposed to be a direct mathematical or cosmological question anyway. It was simply a way to think about how huge the universe is using a reference to something we have at least some idea what size it is and have some rough experience with that. I hesitate to use golf balls or turtles

Your error is assuming there is something definite in the universe called "volume" (or "length", "size", "distance").

There is not. Fundamentally, your thought experiment makes no sense, given what we know about space-time.

That is what is interesting about the question. That is the 'trees in the forest'. When you can wrap your head around it, that is when you'll understand the nature of the questions you are asking.

 

That's funny to think about. I wonder if there is any proof of this curvature of sorts.

That's what I was alluding to a few days ago, the description of nature adopted by GR uses mathematics that is basically non-euclidean geometry.

In SR where acceleration is absent, the geometry is 4D Euclidean, space/time becomes "spacetime" and points in space become "events in spacetime" the relationships between events/space/time can be described in a 4D Euclidean model.

In SR the speed of light is presumed to be constant, all observers always get the same value when they measure that speed, no matter how they are moving relative to each other. The reason it is constant is important to understand.

The speed of light pops out of Maxwell's EM equations, it is a consequence of those laws and SR is predicated on the belief that the laws of physics are the same for all of us, so if Maxwell's equations are always true for all observers then so too must the speed of light be.

People assumed that the speed of light predicted by Maxwell's laws was a speed relative to something and they called that the "aether". But there is no such thing, attempts to observe it failed and the only way to make sense of all that was to do what Einstein did in SR.

The point is SR can be viewed as a geometric theory because relationships between events can be expressed in the same way the relationship between points in a 3D space.

But this nice elegant model no longer work when we introduce gravitation.

https://www.einstein-online.info/en/spotlight/equivalence_light/

 

Your error is assuming there is something definite in the universe called "volume" (or "length", "size", "distance").

There is not. Fundamentally, your thought experiment makes no sense, given what we know about space-time.

That is what is interesting about the question. That is the 'trees in the forest'. When you can wrap your head around it, that is when you'll understand the nature of the questions you are asking.

You seem to be refusing to see the simplicity here, and the reason for it.
There's no error. It makes no sense to YOU, not to ME.

You're again expanding a simple concept into a whole debate involving some of the current knowledge of the Universe. Although that is just fine, just fine, you can't use it as an argument to say the original experiment was wrong, because it was never meant to be right in that context.

So although what you are saying may be true, it does not matter because some of the assumptions you are using were not among the assumptions I was using. This is such a simple concept it is hard for me to believe you are being serious, or just like to argue about things.

Here's a simple example, and if you do not get my point this time there's nothing else to be said I don't think.
I propose that I had measured something that was falling, and the rate came out to 4 meters per second squared. Now you COULD say that since things fall at 9.8m/s^2 that measurement MUST be wrong.
However, you can only say that if your assumptions were different than mine. In the context of my experiment, the measurements were correct.

In any experiment there are always assumptions. The assumptions could be simple (current controlled current source transistor model) or more advanced (full blown spice model). If someone uses the simpler model then you can certainly say it is wrong, but if the idea was to stay as simple as possible then it does not matter if they are wrong or not because the prophecy was fulfilled

If you want to be such a technically accurate disagreeable person (ha ha), why don't you just ask me where I got all the matter for all of those Earths. Did I just magically form new matter all by myself? You can't do that, gee, I must be totally wrong!
You could have even suggested, possibly, that I only use only one Earth and just place it into different positions, remembering where each position was so that I don't place it in a repeated position. That would accomplish the same thing without needing the mass of trillions or more Earths.

 

That's what I was alluding to a few days ago, the description of nature adopted by GR uses mathematics that is basically non-euclidean geometry.

In SR where acceleration is absent, the geometry is 4D Euclidean, space/time becomes "spacetime" and points in space become "events in spacetime" the relationships between events/space/time can be described in a 4D Euclidean model.

In SR the speed of light is presumed to be constant, all observers always get the same value when they measure that speed, no matter how they are moving relative to each other. The reason it is constant is important to understand.

The speed of light pops out of Maxwell's EM equations, it is a consequence of those laws and SR is predicated on the belief that the laws of physics are the same for all of us, so if Maxwell's equations are always true for all observers then so too must the speed of light be.

People assumed that the speed of light predicted by Maxwell's laws was a speed relative to something and they called that the "aether". But there is no such thing, attempts to observe it failed and the only way to make sense of all that was to do what Einstein did in SR.

The point is SR can be viewed as a geometric theory because relationships between events can be expressed in the same way the relationship between points in a 3D space.

But this nice elegant model no longer work when we introduce gravitation.

https://www.einstein-online.info/en/spotlight/equivalence_light/

And it's interesting that gravity affects what we call particles like photons too. I guess it takes a lot of mass to do anything significant though.
While we are at it, a closely related topic is inertia. You could express your ideas about that too if you care to as this is an area I've been interested in for a long time.

 

but we must ask what exactly is an explanation?

I don't know but it I don't think it's limited to formal scientific language. Two examples are religion and story telling. Even at the age of about 5, you are able to understand the story of Pinocchio despite it being completely fictional images or pixels on a screen. Some argue this form of knowledge is baked deep within (millions of years old) and is more real, a sort of "meta-reality" that is more real than scientific reduction-ism. Further, some argue scientific reasoning is born of these meta narratives or archetypes.

For example, one archetype is the hero and the villain. Similarly, another is good or evil, here or there, up or down, us or them. These don't really give reference to the actual reality such as atoms and electrons but somehow this knowledge is just as real and is directly relevant in our lives.

But this is where is gets crazy in my opinion. The archetypes we hold dear to explain one aspect of life also work the other way. Since we are so used to seeing binary code work in a computer with absolute precision or instantly turning on a light with a flip of a switch, we assume this duality must apply to all of reality. However, we know that even a light-switch at the atomic level is never actually 100% on or 100% off which says what we consider to be an algorithm is in practice a heuristic at best. There is a certain absurdity inherit to the structure of reality itself which science cannot hope to explain because it's part of the absurdity. One practical example is you are born, live for maybe 80 years then die. Where is the logic in that? What experiment could you ever perform to either prove or disprove such a scenario...Even logical reasoning fails us in the final analysis because the universe itself seems to be beyond logic. This is what I believe the Buddhists refer in some contexts as the 'self-nature' or 'true reality' which is essentially what is beyond all comprehension. I can certainly understand why many reject this analysis as anti-scientific non-sense because it doesn't seem to have pragmatic value.

So what's my point? Just this, when all you have is a hammer (reductionism), everything starts to look like a nail. Hence we get natural conclusions like, "If the universe exists, it must have a size because everything else has a size". Likewise, "My life must have a purpose because everything else has a purpose". Do you see the problem with this kind of thinking? My primary contention is these questions and answers are often predicated on tool-like categories because we are evolved to use tools (hence the duality of before the tool is applied to after the tool has been applied). Further, I contend that anything that is not a tool is fundamentally an obstacle (useless knowledge). The exception is art and creative expression which seems to branch out from tools but is ultimately an expression of tool use.

Not sure if I'm making sense here because it's an extremely complex topic with many facets and rabbit holes. I'm reminded of my favourite words of Socrates in discussion with Theaetetus on what constitutes knowledge which I think you'll appreciate: The fact is that in our ordinary way of speaking we allow ourselves to be driven into most ridiculous and wonderful contradictions, as Protagoras and all who take his line of argument would remark.

Well we do have history to help I think. Just like when we try to analyze an electronic circuit which we do all the time. We often need to know the initial conditions which is what happened just before we start the analysis. That's the history of the states of the circuit. From that, in many cases we can deduce what is going to happen next (voltage, current, etc.).

When we look back into the history of physics, we see changes in the theories and ideas behind what happens in the universe. If we use that history, we can project that it's going to change again and maybe without end. That leads us to postulate solutions that 'may' be possible in order to possibly help understand what is going to change next and lead to a better understanding. By better understanding I mean we find solutions that match up with more experiments than before, and these would most likely be more recent experiments. Maybe we can call this process projective science or something. We have to acknowledge it in some way or form because if we don't then we basically have to call some good scientists dummies.
Maybe you'd like to call it something like a "religious front porch to real science", but it seems at least a little more concrete than that.

Can we agree truth claims of an electric circuit are of a different nature than truth claims of the universe's size? This is what I refer to as "locally verifiable information" meaning I can personally sit at my workbench and analyse a circuit for truth till the cows come home. On the other hand, I have to take it on faith that Voyager 1 and 2 are at their reported position and are transmitting correct data to which I cannot locally verify. I also cannot build an experiment to see if my Voyager 1 clone will behave like the first one because the initial conditions are now very different (Earth is in a different starting position relative to the sun and so on).

My argument isn't that cosmic science is a useless venture rather some of its core values tend to undermine itself when you run out the logical conclusions. One example is performing an experiment. How do I perform an experiment on the universe to determine its size in a way that controls for all the effects of the universe? Again there is an absurdity here that is inescapable by virtue of having parsed up the world in a dualistic, reductive manner. This is the kind of experiment none of us can perform which means any answer we manage to generate as to the universe's size is not scientific by definition - we cannot apply the scientific method to the entire universe as we do here on Earth. What we end up with is science-like but it's not science as originally defined. As you said in a previous post, something is missing here but I don't think more 'science' will fill the gap.

 

You could have even suggested, possibly, that I only use only one Earth and just place it into different positions, remembering where each position was so that I don't place it in a repeated position.

I was going to suggest a similar experiment, and ask you: "How do you know when you've filled the last position?"

 

Right!

 

I was going to suggest a similar experiment, and ask you: "How do you know when you've filled the last position?"

Exactly!

See there are a lot of ways to knock the idea if you really want to. However, NONE of them apply. That's because it was meant to be a simple comparison of sizes of the Earth to the size of the known Universe.

This type of debate comes up from time to time. It's a matter of one person going general while the other goes detail, or that first person going detail when the other person goes general. There is ALWAYS going to be disagreement then, ALWAYS, and that comes out to one person not being able to understand the other. The assumptions have to be the same and the level of detail have to be the same, and the level of detail may come directly from the assumptions.

What we would see if our Sun was replaced by other objects in the Universe, even a bigger sun. Is that impossible? Damn right it is
But could we at least grasp what it would look like on the horizon? Yes, we can, because humans have more imagination than the Universe.

 

Science develops models, abstract representations that we believe mirror the reality. At the same time history shows that the models always end up being shown to be invalid and so the search for a better model begins.

No model can account for the presence of the universe because science deals with how systems change over time, but until there is a system that exists, science has no role to play.

It seems to me that naturalism (material causality) cannot account for the presence of this universe and its laws, there must be some other explanation like "In the beginning God created" or something. Some say "that's not much of an explanation" but it is, it tells us that naturalism didn't create the universe something more profound did, something that is not reductionist, not causal, not deterministic.

 

It seems to me that naturalism (material causality) cannot account for the presence of this universe and its laws,....

It seems to me that our ability to conceptualise and model is limited by our minds having been shaped by natural selection in a specific physical environment. When we attempt to conceptualise things that deviate significantly from the limits of our minds (eg the very small and the very large) we are reduced to either - using the coherence of mathematical models (so avoiding true conceptual understanding), or - postulating a higher entity that is in charge (handing the problem to some being more intelligent).