Expansion (split from Empty space inside galaxies must be different than empty space outside of them)

[geordief]

2 minutes ago, Bufofrog said:

Galaxies are not moving through space faster than light.  The distance between two galaxies can increase faster than the speed of light because space is expanding without violating relativity.

Do we have evidence that this expansion /inflation was/is entirely  the same wherever we look  in the Universe?

 

On the large scale, I imagine as locally (on small scales)  we don't see it ,do we?

 

I am just wondering if there is a connection between relative motion and inflation  or whether these are two entirely unrelated phenomena.(they do seem awfully similar on the face of it)

 

Is inflation kind of like a background where relative motion does its own thing ? Did inflation come early on and relative motion later on ? Did the former "bleed into " the latter in any sense?

[geordief]

8 hours ago, MigL said:

@geordief
All motion is relative.
Expansion/inflation is not motion.

 

Is inflation/expansion theorized to have started before there was relative motion between objects? (before there were objects?)

Or did the two phenomena start at the same time?

 

Is there any connection at all between the two phenomena or is the similarity** just on the surface?

 

**I mean to an observer (in the layman sense) they seem similar.

[Mordred]

How would you measure inflation or expansion without objects to use as a reference ? 

Though keep in mind the object can also refer to particles.

 

Edited November 1, 2019 by Mordred

[geordief]

53 minutes ago, Mordred said:

How would you measure inflation or expansion without objects to use as a reference ? 

Though keep in mind the object can also refer to particles.

 

Yes, I see that (space seems to be  relative in that sense). Is there a sense in which the object and the Space between them are two sides of the same coin?

 

As there is space-time ,can  there be "space-object"? (not the same "space")

Do objects  actually have infinite spatial extent (except when they interact perhaps)?

 

[michel123456]

These questions are related to the concept of field, I guess.

[swansont]

On 11/1/2019 at 8:54 AM, geordief said:

Yes, I see that (space seems to be  relative in that sense). Is there a sense in which the object and the Space between them are two sides of the same coin?

 

As there is space-time ,can  there be "space-object"? (not the same "space")

Do objects  actually have infinite spatial extent (except when they interact perhaps)?

 

Spacetime is a geometry. Objects are not.

 

"Do objects actually have infinite spatial extent" is kind of a loaded (and vague) question - it depends on what you mean.

[geordief]

34 minutes ago, swansont said:

 

 

"Do objects actually have infinite spatial extent" is kind of a loaded (and vague) question - it depends on what you mean.

Well I think it is accepted that the   object's field* is infinite in extent. Does that mean we can say the same about the object itself? (or at least stop thinking about the object as able to be described as bounded in any sense at all)

 

Since space can be thought** of as the "mortar" between the "bricks " of objects does the above description of objects require a (struggling for the right word...."complementary"?) similar description of space?

Are the "mortar" and the "brick" essentially the same thing?

*hope I am right and that all objects have an associated field
**this is how I have always thought of it.

Edited November 4, 2019 by geordief

[studiot]

2 minutes ago, geordief said:

Well I think it is accepted that the   object's field is infinite in extent. Does that mean we can say the same about the object itself? (or at least stop thinking about the object as able to be described as bounded in any sense at all)

Not necessarily, no.

 

Here is an example.

Mathematically a sine wave goes on forever in both directions along the x axis. It is not bounded in x.

Yet it's value (y) is always bounded by the lines y=+1 and y=-1.

Now the sine wave is very common in mathematical expression where we are modelling something in Physics (particularly fields)
In the physical world we have never seen a sine wave that goes on forever.
The oscillation has a definite start point and points the other way it has not yet reached, or points it can't reach because of a barrier.

So we model the vibrations of a guitar string as a partial sine wave which starts at the bridge and ends at the top fret, although the mathematical sine wave extends beyond this in both directions forever.

This same model come in very handy when modelling an electron in an atom in quantum mechanics.
Here it is called 'particle in a box'.

[geordief]

8 minutes ago, studiot said:

 

This same model come in very handy when modelling an electron in an atom in quantum mechanics.
Here it is called 'particle in a box'.

The "box" in the atom corresponds to the bridge/top fret of the guitar?

 

The discontinuities in QM  work against the idea of infinite spatial extent? (that sounds vague;I am fishing ,I suppose) 

[studiot]

3 minutes ago, geordief said:

The "box" in the atom corresponds to the bridge/top fret of the guitar?

 

The discontinuities in QM  work against the idea of infinite spatial extent? (that sounds vague;I am fishing ,I suppose) 

Fish away, that's great, I'll supply the chips.

 

The ends of the box correspond to the bridge and fret. The vibration  doesn't continue beyond these points, although the string goes a bit further to the anchor points.

But remember this is just an analogy.
It is not exact.

If you add 3 + 5 you get 8.
Simple and precise.
But if you add sin(35) + tan(44) you get something much more complicated.

So the analogy (3+5) is simpler than what it is representing.

[swansont]

12 hours ago, geordief said:

Well I think it is accepted that the   object's field* is infinite in extent. Does that mean we can say the same about the object itself? (or at least stop thinking about the object as able to be described as bounded in any sense at all)

There can be regions where fields are excluded.