Grammar question: as, than OR both?

[GEK]

Is this ok? The comet is twice as far from the sun than the earth is.

Or

The co
Et is twice as far from the sun as the earth is.

[Jozigirl]

You have to use "as" twice because you are comparing two things. 

The comet is twice as far from the sun as the earth is.

[Jhoanna]

Is this ok? The comet is twice as far from the sun than the earth is.

Or

The co
Et is twice as far from the sun as the earth is.

Your co Et is right. You have to use as instead of than.

[dongpal25]

The second one is grammatically right, I think.

[ame]

Both are correct.  The first is unusual.  The second is more natural.

[Jozigirl]

Both are correct.  The first is unusual.  The second is more natural.

 ???
The first one is incorrect.  "The comet is further from the sun than the earth is" would be correct.  'as' has to be used in pairs when making a comparison; it's a pair like "either...or", "neither...nor", "on the one hand...on the other hand".  Only the second sentence is correct.

[GEK]

Anyone know of a reference from one of your grammar books? Mine is watered down. Trying to get "as-than" accepted...

[Jozigirl]

Anyone know of a reference from one of your grammar books? Mine is watered down. Trying to get "as-than" accepted...

"as-than" is wrong - they can't be used together (in this instance at least).  You can use "further-than" or "twice the distance than" but not "as-than".