opposite that of ...

[giddyman]

Sirs and Madams,

Please help me withe this one simple thing.
What does "that" mean in the following sentence? Thank you in advance.

Buoyancy is an upward force that acts in the direction opposite that of gravitational force.

 

[Rover_KE]

[STRIKE]Sirs and Madams,[/STRIKE] Unnecessary.

[STRIKE]Please help me with this one simple thing.[/STRIKE] Unnecessary.

What does "that" mean in the following sentence? [STRIKE]Thank you in advance.[/STRIKE] Just click 'Thank' when you get a useful answer.

Buoyancy is an upward force that acts in the direction opposite that of gravitational force.

It's a pronoun, avoiding the repetition of 'the direction'.

 

[Matthew Wai]

Buoyancy is an upward force that acts in the direction opposite that of gravitational force.

I think 'to' is missing before 'that', but I am not a teacher.

 

[TheParser]

***** NOT A TEACHER *****


Thank you very much, Mr. Wai, for reminding me about that preposition.

Of course, I checked the "books" section of Google and discovered many examples of the "to" being used.

"Each groove having a rearward lead in a direction opposite to that in which the roll rotates." -- OFFICIAL GAZETTE OF THE UNITED STATES (1911).

"She pushes against the pool wall with her feet and accelerates in the direction opposite to that of her push." -- COLLEGE PHYSICS (2014).

"Movement occurs in a direction opposite to that of the pull of gravity." -- RIGHT IN THE MIDDLE (1990).

I had forgotten about the preposition because I am so used to hearing (and reading) sentences in which the speaker (or writer) leaves it out.

I think that the "to" is now considered to be optional.

I doubt that I'll ever have an occasion to write such a sentence, but if it occurs, I will certainly remember to use the "to" -- thanks to you.