Warp wrote:
>   Think about two small spheres connected by a wire on the surface of a
> balloon: Even if you inflate the balloon, the wire will keep the spheres
> at the same distance from each other, against the separating force caused
> by the inflation of the balloon.

Yes, and I'm saying "that doesn't mean the balloon isn't expanding between 
the spheres on wires. It just means the wires are then pulling the spheres 
close together again."

>>>   The same is true at macroscopic levels: The Earth is not expanding because
>>> atomic bonds and gravity are strong enough to stop any expansive drift from
>>> happening. 
> 
>> It doesn't stop the drift. It compensates for the drift.
> 
>   Terminology.

Yes. Just checking we're talking about the same thing. :-)

>>> The Sun's gravity is strong enough to stop planets from drifting
>>> away due to the expansion of the Universe. All the way up to galactic sizes:
>>> The gravity of a galaxy is strong enough to stop stars from drifting away
>>> due to the expansion of the Universe.
> 
>> Sure. That doesn't mean space isn't expanding.
> 
>   But even though new space is forming all the time, that doesn't necessarily
> change units of measurement. The only thing which is changing is the overall
> size of the universe (and given that, as far as we know, the amount of mass
> and energy is constant in the universe, the overall density of mass/energy
> in the universe is correspondingly decreasing).

Correct. That's a different kind of expansion than I was talking about. New 
space vs bigger space.

>>> It doesn't mean that units of distance are changing too. The diameter of
>>> a proton will still be the same in 1 billion years than it is now. 
> 
>> How do you know?
> 
>   Is there any plausible theory, backed up by measurements, that would say
> otherwise? Is there any scientifical reason to think otherwise?

No. The point is that you couldn't tell, without leaving the universe. :-)

>> How would you determine if everything in the entire 
>> universe suddenly got twice as big?  How would you know, for that matter, if 
>> everything in the universe suddenly started going at half speed?
> 
>   By measuring redshift? The speed of light doesn't change, 

The speed of light doesn't change in terms of space vs time. But if space 
gets twice as big *and* the speed of light gets twice as big, then space 
doesn't change.

Draw a ruler on your balloon, and put two dots an inch across. Now inflate 
the balloon. Does the ruler say they're still an inch apart?

>> True, but there may be more than one way in which space is expanding. You 
>> can get more space (which is what seems to be happening between galaxies) or 
>> you can get space that's twice as big (by some absolute measurement we have 
>> no access to).
> 
>   But if you propose that everything is getting bigger in an absolute scale,
> that would mean that also c is getting larger at the same rate (so that we
> are unable to measure everything getting bigger). Is there any reason to
> believe so?

Not that I know of. :-) I didn't know what "SHarkD" meant by "the density of 
space", so I was adding more technobabble. ;-)


-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

Post a reply to this message