[thedoc (OP)]

Wayne Inglis  asked the Naked Scientists:
   Dark Energy is proposed as an explanation of why the universe is expanding at an increasing rate.
Why can't a simpler explanation be that a huge unknown mass may exist outside our visible horizon that acts gravitationally to accelerate the galaxies in the same way that a spacecraft from earth initially slows then speeds up as it approaches the influence of the moons gravitational field?

Regards
Wayne (from South Australia)

   
What do you think?

[Space Flow]

Wayne Inglis  asked the Naked Scientists:
   Dark Energy is proposed as an explanation of why the universe is expanding at an increasing rate.

Dark Energy is a placeholder name for "we simply don't have an explanation what is the cause of the acceleration observed."
Dark energy as a placeholder name is in no way referring to anything specific and as such does not offer an explanation. Just a question mark.

Wayne Inglis  asked the Naked Scientists:
Why can't a simpler explanation be that a huge unknown mass may exist outside our visible horizon that acts gravitationally to accelerate the galaxies in the same way that a spacecraft from earth initially slows then speeds up as it approaches the influence of the moons gravitational field?

Because the effect is observed the same in all directions. A huge unknown mass would exist somewhere and give us observations in that direction.
Otherwise to agree with observations we would have to be totally surrounded by an equal amount of huge mass in every direction outside our observable Universe with us precisely positioned in the exact centre so as to see every direction behave the way it does.
Humanity at the centre of the Universe again.
Not likely.