Stephen Hawking believes that the earth is unlikely to be the only planet ____ life has developed gradually

Question

(I'm reading a grammar textbook, which contains the question and clams it was written for China's National College Entrance Examination in 2010. I checked, and it was.)

Stephen Hawking believes that the earth is unlikely to be the only planet ____ life has developed gradually.

A. that
B. where
C. which
D. whose

The answer is "where", and I understand.

My question is whether "that" works and why.

I think we can say "I will never forget the place where/that/∅ we met for the first time."

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related: Jane is back in May, by____ the new house should be finished

Answer 1

Short answer:

We can't use the word that here.

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Full answer:

Hawking believes that the earth is unlikely to be the only planet ____ life has developed gradually.

Here we are interested in the last part of the sentence. I'll make it shorter, so it's easy to see what is happening:

• Earth is unlikely to be the only planet ____ life has developed gradually.

The second part of this sentence is a relative clause, shown in brackets below:

• Earth is unlikely to be the only planet ____ [ life has developed gradually].

Relative clauses

Relative clauses are very often used to modify nouns:

1. That's the restaurant which [ I like ].
2. That's the restaurant where [ I saw Barrack Obama ]

In the examples above, the relative clauses modify the word restaurant. Usually there is a relative word at the beginning of the relative clause. The body of the clause comes after this word. In examples (1, 2), the relative words are which and where. The clauses after the wh- words are in brackets, [ ... ]. In restrictive relative clauses like these, we can use the word that instead of the word which.

If you look at the clauses inside the brackets, you will see that they have gaps in:

• That's the restaurant which [ I like __ ].
• That's the restaurant where [ I met Barack Obama __ ]

Notice that both the sentences above use the word restaurant. It doesn't matter what the noun before the relative clause is. In both the sentences above, we can think of a restaurant as being a place. So how do we decide when to use which and when to use where?

Well, the word which is a pronoun. The word where is a locative preposition (some people think of it as a locative adverb). If we need to know whether to use which or where, we can look at the gap in the relative clause. If we can fill it with a pronoun like it, then we need to use the pronoun which in the relative clause. If we can fill it with the locative preposition there, we need to use the locative where. Let's split our examples into two sentences so it is easier to see:

• That's the restaurant. I like __ .
• That's the restaurant. I met Barack Obama __ .

If we fill in those gaps we will see that we need to use it in the first sentence and there in the second one:

• That's the restaurant. I like it .
• That's the restaurant. I met Barack Obama there .

We can't do this the other way round!

• That's the restaurant. *I like there . (ungrammatical)
• That's the restaurant. *I met Barack Obama it . (ungrammatical)

So we understand the sentences like this:

• That's the restaurant which [ I like it].
• That's the restaurant where [ I saw Barrack Obama there ]

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The Original Poster's example:

Earth is unlikely to be the only planet ____ [ life has developed gradually __ ].

The gap in the relative clause is at the end here. We can only 'fill it in' with there. We couldn't use it:

• Earth is unlikely to be the only planet ____ [ life has developed gradually there ].
• *Earth is unlikely to be the only planet ____ [ life has developed gradually it ]

For this reason we need the relative locative word where to go with the locative there.

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^{Grammar Note 1}

^{In actual fact, the Original Poster's sentence could also have a gap before the word life:}

^{- Earth is unlikely to be the only planet ____ [ __ life has developed gradually].}

^{We could fill this gap with a possessive pronoun:}

^{- Earth is unlikely to be the only planet ____ [ its life has developed gradually].}

^{This sentence would give us the impression that maybe there were other planets where life developed fast. If the gap represents a possessive pronoun, we need the possessive relative pronoun whose. Remember we use relative whose for things as well as people:}

^{- Earth is unlikely to be the only planet whose life has developed gradually.}

^{Grammar Note 2}

^{Notice that the word place is unusual. After the word place we can use relative clauses with gaps representing locative phrases and we don't need to use the word where. Instead we can use no relative word at all, or we can use the relative word that:}

^{- That's the place we ate last time}

^{- Dublin is the place I want to live.}

^{- That's the place we saw that incredible film.}

^{- This is the place they kept the prisoner.}

^{We can't do this with other nouns:}

^{- *That's the restaurant we ate last time. (ungrammatical)}

^{- *Dublin is the city I want to live. (ungrammatical)}

^{- *That's the theatre we saw that incredible film. (ungrammatical)}

^{- *This is the dungeon they kept the prisoner. (ungrammatical)}

Answer 2

It doesn't.

In this circumstance if you said "that life has developed gradually", this would imply life had developed the planet

"that life has developed ON gradually" is correct.

Answer 3

It is the only pub ________ this local beer is served.

where or that?

It is the only pub where this local beer is served

It is the only pub that serves this local beer.

It is the only pub that this local beer is served at.^{some would call this marginal but it's widely used}

It is the only place __________ the snow never melts.

It is the only place where the snow never melts.

It is the only place that the snow never melts. ^{some would call this marginal}

It is the only place the snow never melts.

Answer 4

There is more than one correct answer (though a bit subjective), but it's not "that".

Stephen Hawking believes that the earth is unlikely to be the only planet ____ life has developed gradually.

A. that
B. where
C. which
D. whose

In order of brevity:

Where

Is correct. "the planet" can be considered a location, so you can say "the planet where life has developed".

Whose

Is also correct, if you consider "Earth's life" to be a valid interpretation. Though it relies on a personification of Earth, that isn't too far-fetched. We can reference mother nature, which is the same (albeit more overt) type of personification.

We say things like "the Earth's crust", "the Earth's atmosphere", ... I consider "the Earth's life" to be equally correct from a grammatical perspective, regardless of it being more poetic than the other examples.

I consider this correct; and I'm interested in anyone who has a specific counterclaim that it is incorrect.

That

Is not correct. However, I do think I see why you think it is. There is a very similar sentence in which "that" would be correct.

This is not correct:

Stephen Hawking believes that the earth is unlikely to be the only planet that life has developed gradually.

This is correct:

Stephen Hawking believes that the earth is unlikely to be the only planet that has developed life gradually.

In this second example, the planet (subject) developed life (object), rather than saying "life developed [itself]" (which is what the original sentence is conveying).

If that is what you want to say, then you can also say "the planet that developed life" or "the planet that has developed life".

This again rests on the implicit personification of the planet, similar to my explanation in "whose", which I still think is a correct interpretation.

However, given the question's specific phrasing, "that" is not a correct answer to this question.

Which

Is not correct. However, there are nearby versions that are correct:

1. Stephen Hawking believes that the earth is unlikely to be the only planet which has developed life gradually.

Similar to my explanation in "that", this relies on the notion that the planet (subject) developed life (object).

2. Stephen Hawking believes that the earth is unlikely to be the only planet on which has developed life gradually.

"On which" is the first thing I though of when I saw your question title (before I read the question body). It is more idiomatic than the given options.

"On which" is correct for the same reason that "where" is correct; because "the planet" can be considered a location. And in English, we say "on the planet", not "in the planet", which is why "on which" is correct and "in which" is not.