[CPT ArkAngel]

I like the way you say it Bill  [)], but your first assumption is quite a revelation!!!

[Bill S]

your first assumption is quite a revelation!!!

This means that either I have it wrong, or you need to do some more thinking. [] 

Give me an example of something finite that becomes infinite, we can work from there.

[CPT ArkAngel]

I mean this assumption is right: nothing finite can become infinite.

[Bill S]

nothing finite can become infinite

Great! Someone who is willing to put this in writing. Would you also agree about the next step: "Anything that is infinite must also be eternal"?

[CPT ArkAngel]

it sounds very logical to me, but some people might disagree about the properties of time...

And what about something eternal, does it have to be infinite?

[Bill S]

And what about something eternal, does it have to be infinite?

Before I try to answer that one, let me ask you one more question, just to make sure we are on the same page.
What is the difference between infinite and eternal?

[CPT ArkAngel]

Infinite in space and eternal (infinite) in time.

[acsinuk]

We are all playing with words because we just do not know.  But things in this universe are logical and black holes with huge negative masses are certainly not logical; and neither are worm holes to other universes.
There is an alternative electric option. What if super massive black holes are at the centre of every galaxy like a giant magnetic hub around which all the stars rotate in a set order.  The magnetic field not only spins the stars into position [ which gravity cant] but can accept feedback to avoid collisions.  If collisions  occur then the tiny galaxy may turn into a vibrating quasar or a magnetar. What do you think?
CliveS
 

[Bill S]

There is a lot of playing with words, it can be fun, but is usually not very productive.  However, there are also lots of lines of discussion that are less productive than they could be, simply because different people ascribe different shades of meaning to particular words.  Infinity is a concept that suffers greatly in this regard.  For example; it is important to establish if we are talking about mathematical infinities or a physical infinity.  It is also crucial to distinguish between infinite and boundless.  That's before getting into some of the finer points.  Take, for example, ArkAngel's response to my question:

Infinite in space and eternal (infinite) in time

Infinity is not infinite space, nor is eternity infinite time.  We have to think of them in that way because we are unable to even imagine the possible dimensions of infinity.  While there is nothing wrong with ArkAngle's answer in terms of our 4D thinking, it is important to remember that it is a sort of "model", perhaps the nearest we can come to understanding the real thing.  Just think about a spider walking through "Flatland".  []
You raise an interesting point, Clive, but it will take me a little while to get my brain around it.   []

[5nutjob]

Singularities are not necessarily 0-dimensional points; for instance they may well be circles, spheres & hyperspheres; so energy 'density' never becomes infinite.  [:I]

[tbarron]

Infinity is not infinite space, nor is eternity infinite time.  We have to think of them in that way because we are unable to even imagine the possible dimensions of infinity.  While there is nothing wrong with ArkAngle's answer in terms of our 4D thinking, it is important to remember that it is a sort of "model", perhaps the nearest we can come to understanding the real thing.

How can we even know there's a "real thing" to be modelled? Just because we can imagine invisible pink unicorns doesn't mean they exist. Similarly, just because we can grok the concept of infinity doesn't necessarily mean anything actually is infinite.

[Bill S]

just because we can grok the concept of infinity doesn't necessarily mean anything actually is infinite

Perhaps you should start by asking yourself if there can ever have been a time when there was nothing. It's surprising where you can go from there.  [8D]

[peppercorn]

Similarly, just because we can grok the concept of infinity doesn't necessarily mean anything actually is infinite.

A Series can be! [] (tongue firmly in cheek!)
No one can say for sure that anything physical has infinite dimension (gravity, distance, etc).


Re: singularities -
Wikipedia - that bastion of all knowledge [] says of singularities:
"A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system. These quantities are the scalar invariant curvatures of spacetime, some of which are a measure of the density of matter."
It also says there are theories that specify that singularities can not exist. mmmm []

[Bill S]

A Series can be!  (tongue firmly in cheek!)

Very sensible; you knew that would set me off if you said it seriously, didn't you? []

"A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system. These quantities are the scalar invariant curvatures of spacetime, some of which are a measure of the density of matter."

OK. You quoted it, you translate it so the plebs can understand it. []

[CPT ArkAngel]

Is it possible that the universe has appeared from nothing? If not, the universe is eternal (even if maybe discrete in some way). But it doesn't mean it is necessarily infinite in the other dimensions.

It is open to a more casual and funny discussion i hope...

By experiences, Physics tend to say any singularity is very improbable, to say the least...

[joshrego]

I just feel that we all can ever imagine to do with black holes theorize.In fact a black whole is a tunnel between universes.  Black hole attracts matter that does not collapse into a point, as predicted, but a black one out the other end of the "white hole" say, the theory goes.

[Bill S]

Is it possible that the universe has appeared from nothing?

If there had ever been a time when there was nothing, there would be nothing now. Manifestly, there is something now, so something must be eternal.

But it doesn't mean it is necessarily infinite in the other dimensions.

I've been trying to get my head round this for some time.  Does "eternal" automatically imply "infinite"?  I feel it should, but have yet to formulate the necessary argument to my own satisfaction. 

Welcome, joshrego.  Hope to see lots of posts from you. Don't take all of us too seriously, though.

In fact a black whole is a tunnel between universes.

Is this an assumption, or do you have evidence that would make William of Ockham turn in his grave?

[tbarron]

Perhaps you should start by asking yourself if there can ever have been a time when there was nothing. It's surprising where you can go from there.  [8D]

A similar question would be whether there could be a place where there was no time.

In both cases, the answer depends on my assumptions. If I assume that nothing cannot become something, I answer "No, there could not be a time when there was nothing." If I assume that nothing can become something, I answer, "Yes, there could have been nothing at one point in time, and then something at a later point." I'm not even sure what it would mean to have a place without time. How long would it last?

However, when I think of space-time as a four dimensional structure, I can imagine bounds in both time directions.

Of course, I also have to ask whether what I can imagine has anything to do with what is.

[tbarron]

I've been trying to get my head round this for some time.  Does "eternal" automatically imply "infinite"?  I feel it should, but have yet to formulate the necessary argument to my own satisfaction.

I think "eternal" just means "outside time", not "infinite in duration". Something eternal is something that doesn't have extension in the temporal direction. Its value is the same at all points on the time axis. I don't think we'd have any way of observing such an object since our experience is so aligned to the temporal dimension.

Wiktionary offers the following definition for "eternal": "(philosophy) existing outside time; as opposed to sempiternal, existing within time but everlastingly"

[Bill S]

Something eternal is something that doesn't have extension in the temporal direction. Its value is the same at all points on the time axis.

This captures a major factor in the problem. If it "doesn't have extension in the temporal direction", how can it be present "at all points on the time axis"?