cosmology - Universe is expanding at enormous speed

I'm not an expert but I've come to understand that the universe is expanding at enormous speed. That means that all of the visible galaxies are moving away from us at great speed.

I also came to understand that, eventually (in many many years), all the galaxies and all of the rest of the objects outside our own galaxy will move so far away from us that it will be impossible for us to look (or measure) them.

This means that eventually our entire observable universe will be our own galaxy and it will be impossible for us to measure anything else, and scientific measurements at that point in time will not correspond to the actual reality... because data will show that other galaxies don't exist.

But I have two questions regarding this phenomena:

1. 
   

   How is it that the light won't reach us anymore? Is the expansion happening at greater speed than light itself, making it impossible for it to ever reach anything?

   
   


2. 
   

   If scientific measurements, at that point in time, will prove to be wrong, because they will show that galaxies don't exist (while they actually do exist), doesn't that mean that something similar could be happening right now as well? We could be measuring something about the universe that we're dead sure about, but it won't be the actual reality.

   
   

Answer

I'd like to expand a bit on the answer to the second question, but for completeness I'll do both.

1. 
   

   As said in JasonR's answer, the expansion of space isn't limit by the speed of light. So objects can be moving at moderate speeds, but because the space between them and us expands faster than light, it's emissions will never reach us. For this reason, there are already regions of space that are beyond our horizon. Whether or not this will always be depends on what "Big Thing" your cosmology ends with. If it's a "Crunch", then everything comes back together in a reverse "Bang" at the end of time. If it's just a "Freeze", then the acceleration expands and possibly even accelerates forever.

   
   


2. 
   

   Abraham Loeb wrote a curious paper (available on the arXiv) about how to reach cosmological conclusions in the absence of nearby galaxies. About 100 billion years from now, all the galaxies in our Local Group will be beyond the horizon of the Milky Way (or rather Milkomeda, after the Milky Way collides with Andromeda), and the CMB will be at a wavelength longer than the observable Universe. But you'll still be able to reach conclusions about cosmology by using hypervelocity stars being ejected from the galaxy. The point is that you can still get accurate results about the global structure of the Universe using local results.

   
   

   As for our current model, we have a great deal of evidence that the cosmos is structured according to the Concordance Model. You can always say "it might turn out to be wrong", but it can't turn out to be that wrong because of said evidence. It's like GR as a generalization of Newtonian gravity: yes, Newton was "incorrect" but his theory was also quite accurate, to the extent that we still use it for, say, N-body simulations of star clusters.