Sentence Correction

Received a PM asking me to respond.

This is an OG question, so I can't discuss it directly, but I can discuss a similar sentence that I make up...

The debate here is between these two "types" of sentences:

1) Light can travel through space for huge distances, its energy prevented from dissipating by X.

2) Light can travel through space for huge distances, preventing its energy from dissipating by X.


Let's start with #1.
The word "prevented" can be a regular conjugated verb or it can be a participle. If it's a participle, it can be part of a verb form (with another conjugated verb before it) or it can indicate a modifier. Examples of the two verb options:

"prevented" as regular conjugated verb: I prevented my paper from blowing away.

Conjugated verb + "prevented" participle: My paper was prevented from blowing away. (The paper was prevented by me.)

Now, what is the difference in those two sentence constructions? The first is active; the second is passive. In the first, the subject (I) is doing the action (prevented). In the second, the subject (paper) is having the action performed on it (I'm still doing the preventing, not the paper).

Could I write: "The paper prevented from blowing away" - meaning, the paper prevented itself from blowing away? Nope. The paper can't prevent itself from blowing away. If we want to use "the paper" as the subject, we have to write this in passive voice.

So. Energy prevented from dissipating by X. Is that a sentence? Can the energy prevent itself from dissipating? No, again. If we want to use "energy" as a subject and have an independent clause here, we have to write this in passive voice, which would be "the energy WAS prevented from dissipating by X."

What does that mean? That word "prevented" is not a conjugated verb or part of a conjugated verb form in this sentence. Therefore, it's a modifier and the stuff after the comma in C is NOT an independent clause - it's the rest of the modifier.

Now, #2.
2) Light can travel through space for huge distances, preventing its energy from dissipating by X.

We have <independent clause>, <-ing modifier>. The -ing modifier needs to modify the preceding clause. Also, the modifier needs to follow from the independent clause; that is, something in the independent clause needs to be doing this "preventing." What is doing this preventing?

Argh. It's the stuff after the word "by." That's not part of the independent clause. Nothing in the independent clause is responsible for "preventing the energy from dissipating." This is a misplaced modifier.

If it's too confusing to understand based on the example above, try this:

Paper can fly through the air for huge distances, preventing it from falling by gusts of wind.

What's preventing the paper from falling? The gusts of wind. But the "preventing" has to refer to the stuff *before* the comma. Nothing *before* the comma is actually preventing the paper from falling.

C is NOT passive tense - that's why.

I was showing that it's not either active or passive - it's not in a conjugated verb form at all. It's just a participle alone, so it's a modifier.

the strange construction being tested here is called an "absolute phrase".

for further discussion of these, see the following thread:
https://www.beatthegmat.com/sc-with-surf ... tml#232639

when you see weird constructions like this, you should be less intent on analyzing their every word, and correspondingly more intent on memorizing the appearance of specific examples of them, so that you know exactly what they look like (even if you aren't able to analyze them with full confidence).

--

Clearly this is a passive voice sentence

this absolute phrase isn't really an example of the passive voice, since it doesn't actually contain a verb.
instead, it just contains a past participle ("prevented"), which functions as a modifier.

note that the passive voice, when it is present, ALSO contains one of these past participles -- so you can think of the two constructions as closely related to each other.
the difference is that, in a genuine passive-voice construction (which must contain a VERB), the past participle is preceded by some form of the verb "to be".

on the other hand, it's incorrect to think that you must have a passive-voice verb whenever you see a past participle; there are all kinds of modifiers that use past participles without passive voice verbs.

probably the most common of these modifiers is an initial modifier containing a past participle:
Dedicated to the recently deceased president, the ceremony was quite emotional.

you may take the same past participle ("dedicated") and place it into a passive-voice construction:
the emotional ceremony was dedicated to the recently deceased president.

you can also do the same with an absolute phrase:
the singer gave an emotional concert, his songs dedicated to the recently deceased president.

again, simply being able to recognize these constructions when you see them ("hey, that looks like some of the other correct answers") is much, much more important than being able to dissect them in excruciating detail.