Facebook
Google
GitHub
Linkedin
How big is the universe?
- Thread starter joeyd999
- Start date
Thanks for that. Loved the "Occam's factor" argument.
Hi,
I like the fact that he drew an importance between very large objects and very small objects because that highlights every problem we have today. It's all a matter of scale comparisons.
For physical objects it is a matter of distance. That is, distance between two objects or length which is a distance across a single object.
There are many other scale comparisons to consider though, (temperature, pressure, etc.) which highlights the elementary problem we have with understanding physics, and physics is the most basic area of study for everything we know no matter how large or small or how far apart. Well, at least that is what we "believe" for now, and since that's all we have right now we go with that, and that's a form of Occam's Razor right out of the starting gate. In a manner of speaking, we "assume" therefore we "are". This really says that we always fall under the paradigm of Occam's Razon whether we like it or not. Everything we do boils down to some assumption of simplicity, even string theory.
That's one thing we have to remember, but also that Occam's Razor is a heuristic, and if anyone has ever analyzed the game of chess in detail they know that heuristics only go so far ... until we look one more ply deep (one ply is equal to one move by only one side black or white), and then we find that the heuristic either succeeded or failed. Note however that "succeeded" does not necessarily mean that we succeeded for all time, because when we look even one more ply deep we may still find that it's failed, just on a deeper level. Even "failed' is not the end of it, because one more ply deep may show that, given our current analysis heuristic, may have still been wrong.
This is probably the best representation of our dilemma to understanding just about everything there is to know.
As to any of these dimensions (distance, temperature, pressure), we do not know how the extreme of the extremes changes things. There is the possibility I guess that we will never know how all of these changes things. There may be exceptions, such as absolute zero, but that seems to be one thing we can actually measure, even though we may still be wrong in the most obscure sense.
So again we come back to our common experience with reality and how it may different from actual reality, or even if there is such a thing as a constant reality. We use what works for now, that's about it.
BobaMosfet
- Joined Jul 1, 2009
- 2,211
The universe is infinite, and has existed forever (earth & heavens, too- all are same age). This is known and documented. The fact that people refuse to grasp this simply shows how limited man's mind is. And yes, the Big Bang was disproven- foolish notion.
Undoubtedly. I’m convinced by such overwhelming evidence. By the way, where is it (the evidence) again?
Here's a decent review of the latter (big bang) issue. I can't imagine what evidence could support the former.
https://www.researchgate.net/publication/382181821_The_Scientific_Evidence_Against_The_Big_Bang
https://www.researchgate.net/publication/382181821_The_Scientific_Evidence_Against_The_Big_Bang
ElectricSpidey
- Joined Dec 2, 2017
- 3,343
The universe is flat and spinning...nice, now all we have to do is stop the spin, apply the toppings and put it in the oven.
But seriously...was an interesting read.
But seriously...was an interesting read.
Everything else naturally spins probably because there is just nothing to stop it from spinning. It's natural for something to spin unless there is a force preventing that.
Who knows, it could be the universe is rotating around an axis and also rotating around something else too just like planets do.
Spin is something whose essentials I can't wrap my head around ... in an empty universe, if you were into uniform motion you wouldn't know, and you wouldn't even feel it. But if you were spinning, you would certainly know because of the centrifugal force. Linear and angular acceleration you would be able to feel (measure), But constant linear and angular motion behave in different ways, I think.
The problem is the size of the universe vs. its age.
The universe hasn't been around long enough for information at one end to reach the other. So, how is angular momentum communicated across the span of the universe?
(Queue Cosmic Inflation)
Hi there,
Well, I am not sure what point you are trying to make there maybe you can make it a little clearer.
My only thought so far on your comments is that it might be hard to correlate human experience with physics in the most general way, and same even solid objects. For example, if the angular motion is incredibly small or incredibly large you would not even realize it was happening. This might be harder to explain on the micro micro level, but on the very large not so hard at all. On the large involving thousands of light years, any angular motion on a tangent very distance from the center would seem like linear motion. It depends on the radius and the tangential speed. Could that even suggest that we don't ever know if we are moving in a perfectly straight line or on the circumference of an extremely large circle.
Hi,
What do you mean by "angular momentum communicated across the span of the universe" ?
First, tell me what you mean by spin (on a Universal scale) and how do you measure it?
Yes, assuming a Big Crunch at the end [of the universe].
But that no longer seems likely.
The simplest case would be an object that takes a circular path. It does not really have to be circular of course such as with an ellipse.
The global measurement would be something like w=dTH/dt with TH being the angle.
The local measurement would be something like dx/dt or dy/dt or both, over at least three points along the curve.
Intrinsically we can do a unit tangent vector. Curvature per unit length of distance traveled (which can also vary of course). The curvature I think would then be the square root of the sum of the squares of the second derivatives of x and y with respect to distance (length). This is explained in terms of arc length parameterization in Wikipedia.
Are you asking because the distance to the center of rotation could be very large?
It can be large and also non constant but all curves have at least a local curvature. I would not expect any perfectly sharp angles like a perfect right angle because of the way things move when uninterrupted in any way.
Maybe you can explain why you asked this.
This is also interesting coming from István Szapudi of the University of Hawaiʻi at Mānoa: "Panta Kykloutai"
My basic thoughts on this are that if objects interact in an asymmetrical way due to random directional forces, we always see a rotation. That's because when something hits something else it's not usually perfectly head on like two pool balls, which even they can spin due to the interaction of another ball. Another way of looking at this is that many interactions are such that one object sort of side swipes another object, and that would cause at least one of them to spin.
Since we are talking about the universe, we'd probably have to talk about initial conditions and everything that happened right after the start. If everything moved in a symmetrical way, we might see no rotation at all. But since it would be chaotic it would be reasonable to assume it was rotating, at least somewhat, and even if it was slow.
The expansion of the universe may show us something about this. If it was rotating, perhaps that is why it is expanding. No need for dark matter.
Last edited:
