Does Dark Energy Exist?

I recently watched a TV program about dark energy on the Science Channel.  It was an episode of "Space's Deepest Secrets."  Dark energy was something I'd never paid much attention to before.  Suddenly, I found the subject to be fascinating.  Looking around the Internet, I found some key information HERE about dark energy:

Assuming the existence of dark matter and that the law of gravitation is universal, two teams of astrophysicists—one led by Saul Perlmutter, at the Lawrence Berkeley National Laboratory, the other by Brian Schmidt, at Australian National University—set out to determine the future of the universe. Throughout the 1990s the rival teams closely analyzed a number of exploding stars, or supernovas, using those unusually bright, short-lived distant objects to gauge the universe’s growth. They knew how bright the supernovas should appear at different points across the universe if the rate of expansion were uniform. By comparing how much brighter the supernovas actually did appear, astronomers figured they could determine how much the expansion of the universe was slowing down. But to the astronomers’ surprise, when they looked as far as halfway across the universe, six or seven billion light-years away, they found that the supernovas weren’t brighter—and therefore nearer—than expected. They were dimmer—that is, more distant. The two teams both concluded that the expansion of the universe isn’t slowing down. It’s speeding up.
The implication of that discovery was momentous: it meant that the dominant force in the evolution of the universe isn’t gravity. It is...something else. Both teams announced their findings in 1998. Turner gave the “something” a nickname: dark energy. It stuck. Since then, astronomers have pursued the mystery of dark energy to the ends of the Earth—literally.

The program made it very clear that no one really knows if "dark energy" really exists.  They call it "dark" energy because they don't now what it is, not because it is somehow dark in color.  Everyone seems to realize it could very easily be that they are just looking at things from the wrong angle. 

On the Internet I'd previously argued with people who believe that "the aether" is slowing down light coming from distant galaxies, or gravity from dust particles is slowing down light.  They were usually arguing against the Big Bang theory, not against Dark Energy.  To me, it seemed "obvious" that some misunderstood factor about Time and/or the speed of light was causing the distant supernovae to appear to be moving so fast.  There are lots of things we do not know about Time and Light, so why assume that there is something totally new that is behind what is being observed?

Of course, my ignorance of these subjects is very great, but what I do know says that it makes no sense to assume that anything like "dark energy" actually exists.  Unlike Science Truthers, however, I'm not prepared to argue that the idea is wrong simply because it makes no sense to me.  What I am prepared to do is some "slow thinking" to try to figure out why it makes no sense to me.  Maybe there is something the Nobel Prize winners know that I do not know.  That certainly seems possible.

First of all, I know the official "speed of light" is the speed of light in a vacuum.  And I know that the speed of light is slower through air and water.  In a vacuum the speed of light is 299,792,458 meters per second, while in water it is 225,056,264 meters per second.  And that means that, if the light from a supernova is somehow going slower when it arrives, it would merely appear that the supernova is farther away than it really is, because scientists used an incorrect measurement for the speed of that specific light.     

If it is not possible for light to go slower simply because it is coming from an object that is moving away at a very high speed, then the question becomes: If an object is moving through Time at a much slower rate than we are, wouldn't the light the object emits be slowed down as well?  Is it possible for us to detect a difference between light that travels at a slow speed and light that moves at its maximum speed through a slow tunnel of time?  Does that question even make sense?
 
I did a Google search for "how is the speed of light measured" and found this question and answer:

Is The Speed of Light Everywhere the Same?

The short answer is that it depends on who is doing the measuring: the speed of light is only guaranteed to have a value of 299,792,458 m/s in a vacuum when measured by someone situated right next to it.

Hmm.  Groan!  When I get some free time, I'm going to have to try to find out how the people who dreamed up "dark energy" eliminated all the other (seemingly) possible explanations for why light from a supernova shows that the universe is expanding faster and faster.  When you have an explosion, doesn't the material that ends farthest from the point of the explosion get there because it traveled faster than the other material involved in the explosion?  And who says that the universe has had sufficient time for gravity to start slowing things down?