Learn Hardcore Indonesian: Ilmuwan muda itu menjelaskan lapisan tanah di dekat gua tua. - That young scientist explains the soil layer near the old cave.

What does itu mean in ilmuwan muda itu, and why does it come after the noun phrase instead of before like that young scientist in English?

Itu literally means that, but in many contexts it functions like the English definite article the.

In Indonesian, itu is a post‑determiner: it usually comes after the noun phrase it modifies.

ilmuwan muda itu
= that/the young scientist
(literally: scientist young that)

If you said itu ilmuwan muda, it would sound more like that is a young scientist (a complete sentence with itu as a pronoun: that), not that young scientist as a noun phrase.

So, for a normal noun phrase:

rumah besar itu – that/the big house
buku baru itu – that/the new book

How does Indonesian show past tense here? Why can menjelaskan mean explained without a past-tense marker?

Indonesian verbs usually do not change form for tense. Menjelaskan is a general verb form that can mean:

explains
is explaining
explained
will explain

The exact time is understood from context or from additional time words, for example:

Kemarin ilmuwan muda itu menjelaskan lapisan tanah di dekat gua tua.
Yesterday the young scientist explained the soil layers near the old cave.
Sekarang ilmuwan muda itu menjelaskan…
Now the young scientist is explaining…

So the sentence without any time word is tense-neutral, and English speakers choose the most natural tense when translating.

What is the difference between menjelaskan and menerangkan? Could I use menerangkan instead?

Both menjelaskan and menerangkan can mean to explain, and in many everyday contexts they’re interchangeable.

Rough tendencies:

menjelaskan – very common, slightly more neutral/formal and widely used in academic or written language.
menerangkan – also means to explain, to clarify, but can have a nuance of making something clear/bright (terang = bright, clear). It’s also used, but in some contexts it feels a bit more old‑fashioned or less frequent than menjelaskan.

In this scientific context:

Ilmuwan muda itu menjelaskan lapisan tanah di dekat gua tua. ✅
Ilmuwan muda itu menerangkan lapisan tanah di dekat gua tua. ✅ (still acceptable)

Both are understandable; menjelaskan is the more typical choice in modern standard Indonesian.

Why is there no tentang (about) after menjelaskan? Would menjelaskan tentang lapisan tanah be wrong?

Menjelaskan already means to explain something, and it normally takes a direct object without tentang:

menjelaskan lapisan tanah – to explain the soil layers ✅

Adding tentang (about) is often unnecessary and can sound redundant, especially in careful or formal Indonesian:

menjelaskan tentang lapisan tanah – literally explain about the soil layers
→ Commonly heard in speech, but many style guides consider it less neat.

If you really want to use tentang, you would usually pair it with a different verb, such as:

berbicara tentang lapisan tanah – talk about the soil layers
menulis tentang lapisan tanah – write about the soil layers

For menjelaskan, the most natural pattern is:

menjelaskan + [object] (no tentang).

What exactly does lapisan tanah mean? Is it soil layers, layers of soil, or something else?

Lapisan tanah is a noun + noun combination:

lapisan – layer / layers / stratum
tanah – soil, earth, ground, land (depending on context)

Together, lapisan tanah is best translated as:

soil layers
layers of soil
in geology: soil strata or soil horizons

Indonesian doesn’t always mark plural with an -s or duplication here. Lapisan tanah can refer to one or several layers, depending on context.

If you wanted to emphasize plurality explicitly, you could say:

lapisan-lapisan tanah – layers of soil (many layers)
But this is not necessary unless you really want to stress “many.”

Why is the adjective muda placed after ilmuwan, and tua after gua? Can I put them before the nouns like in English?

In Indonesian, adjectives normally follow the noun they modify:

ilmuwan muda – young scientist (literally scientist young)
gua tua – old cave (literally cave old)

Putting the adjective before the noun (muda ilmuwan, tua gua) is not standard and will sound wrong or at least very strange to native speakers.

Basic pattern:

noun + adjective
- buku merah – red book
- kota besar – big city
- anjing kecil – small dog

In your sentence:

ilmuwan muda itu – that/the young scientist
gua tua – old cave

Does itu only modify ilmuwan, or the whole phrase ilmuwan muda?

Here, itu goes with the whole noun phrase ilmuwan muda:

ilmuwan muda itu
= that young scientist / the young scientist

The structure is:
[noun + adjective] + itu

So itu refers to a specific young scientist that both speaker and listener can identify from context. It’s not just “that scientist” (any age) or “that young (one)”; it’s exactly “that young scientist.”

Could I drop itu and just say Ilmuwan muda menjelaskan lapisan tanah di dekat gua tua? Would the meaning change?

You can drop itu, but the nuance changes slightly:

Ilmuwan muda itu menjelaskan…
→ The/that young scientist explained…
(Refers to a specific young scientist already known in the context.)
Ilmuwan muda menjelaskan…
→ A young scientist explained… or Young scientists explain… (more general / indefinite).

Without itu, the phrase becomes less specifically anchored. It could be a general statement or it could introduce a new participant (a young scientist, not previously mentioned). Context will still matter, but itu clearly marks a particular, identifiable scientist.

What does di dekat mean exactly? Is dekat a preposition or an adjective?

Dekat basically means near / close.

On its own, dekat is more like an adjective/adverb:
- Rumah saya dekat. – My house is near (here).
- Sekolah itu dekat dari sini. – That school is near from here.
Di dekat functions as a prepositional phrase meaning near / in the vicinity of:
- di dekat gua tua – near the old cave
- di dekat sungai – near the river

In your sentence, di dekat gua tua is a location phrase:
di (at/in) + dekat (near) + gua tua (old cave) → near the old cave.

You could also say dekat gua tua without di in quite a few spoken contexts, but di dekat is the more standard, clear prepositional pattern.

Could I say di gua tua instead of di dekat gua tua? How would that change the meaning?

Yes, but the meaning changes:

di dekat gua tua – near the old cave (somewhere close to it, not inside it)
di gua tua – in/at the old cave (inside or at the cave itself)

So:

Ilmuwan muda itu menjelaskan lapisan tanah di dekat gua tua.
→ The explanation happens near the cave (e.g. at an excavation site just outside).
Ilmuwan muda itu menjelaskan lapisan tanah di gua tua.
→ The explanation happens in/at the cave itself.

Is gua the same as goa? I’ve seen both spellings.

Yes, gua and goa refer to the same thing: cave.

gua – nowadays the more common, modern spelling in everyday Indonesian.
goa – still used, especially in place names and some older or more formal/archaeological contexts (e.g. Goa Gong, Goa Kreo).

In ordinary sentences like yours, gua tua is perfectly natural. Using goa tua would not be wrong, but gua feels more current in general usage.

How would I make scientists (plural) instead of scientist here? Is there a way to clearly say young scientists?

Indonesian often does not mark plural explicitly; context usually shows whether it’s singular or plural.

However, to emphasize plural human nouns, you can use para before them:

para ilmuwan muda itu – those young scientists
(literally: the group of young scientists)

So for a clearly plural subject:

Para ilmuwan muda itu menjelaskan lapisan tanah di dekat gua tua.
→ Those young scientists explained the soil layers near the old cave.

Other options:

ilmuwan-ilmuwan muda – repetition (ilmuwan → ilmuwan‑ilmuwan) also marks plural, but with longer words and in modern usage this sometimes sounds less natural or overly formal. For people, para + singular noun is usually smoother.

Without any marker:

Ilmuwan muda itu…
can still mean either the young scientist or the young scientists, depending on context.