Are these two topics in the same sentence?


For full context:
<http://www3.nhk.or.jp/news/easy/k10011273631000/k10011273631000.html>

The sentence in question:
水族館は、オウサマペンギンが外で散歩をすることができるのは気温が低くなる冬だけなので、いい運動になると言っています。

My attempt at translation: Literal: "Concerning the aquarium, concerning that
the penguins can take a walk outside, they say that it becomes a good physical
exercise,because there is the alone temperature-lowering-winter." More
elegant: "The aquarium says that it becomes a good physical exercise that the
penguins can talk a walk outside because winter alone is bringing temperature
down."

So, First, as the title suggests, I don't really know when two topics are
allowed in a japanese sentence. I also don't really know how to handle them,
how they relate to each other, wether one topic can be subordinated to the
other etc.. I think I understood the sentence contentwise, but I've little
idea how the grammar actually works.

Furthermore, probably because there are multiple topics used to build the
sentence, there is kind of a lack of transitivity...^^ What confused me the
most was 気温が低くなる冬だけなので. I think the ghist of this part is that winter brings
down temperatures, which is a good thing for the physical well-being of the
penguins. However, 冬 doesn't take direct influence on 気温, but instead it is an
attribute of 冬 that expresses "becomes lowering temperature". The problem with
hereby is that 低くなる itself is also a bit confusing since 低く is a noun and not
an adjective. I can follow this logic in some cases, but in this case its a
bit hard because it is not something along the lines of "The swine becomes a
steak" (sorry for the bad humor^^) but more along the lines of "The sun
becomes dark". This difficulty I have stems from the entry on
<http://jisho.org/search/%E4%BD%8E%E3%81%8F> where 低く is categorized as a noun
or suru verb, however the two meanings are no nouns Oo Therefore, my
translation doesn't reflect a "NOUN becomes a NOUN" structure but a "NOUN
becomes ADJECTIVE" structure. Because of that, I feel like I didn't really
understand whats going on in this sentence Oo

I also don't know if I understood the use of だけ correctly. I think that here
it is used to express that only through winter such a drop in temperatures can
be achieved, at least for a "walk outside" (One could also put the penguins
into a cooling chamber for example).




Using two topics is fine when one is in a quote. A simpler example is
私は彼は来ないと思う ("I think he won't come").

And you seem to have failed to notice a [cleft
sentence](https://japanese.stackexchange.com/q/19204/5010) embedded as a
clause. From this sentence:

> 気温が低くなる冬だけ、オウサマペンギンは外で散歩をすることができる。  
>  Only in winter, when temperatures drop, king penguins can take a walk
> outside.

...we can get this cleft sentence:

> オウサマペンギンが外で散歩をすることができる **のは** 気温が低くなる冬だけだ。  
>  It is only in winter, when temperatures drop, that king penguins can take a
> walk outside.

Once you've understood this, the rest should be straightforward to you:

> 水族館は「オウサマペンギンが外で散歩をすることができるのは気温が低くなる冬だけなので、いい運動になる」と言っています。  
>  The aquarium says that it will give king penguins a good workout because it
> is only in winter, when temperatures drop, that they can take a walk
> outside.

気温が低くなる (literally "when temperatures become low") is a small relative clause
that just says 冬 is a cold season. This may seem too obvious, but it
explicitly states that what matters for penguins is temperature.




Using two topics is fine when one is in a quote. A simpler example is
私は彼は来ないと思う ("I think he won't come").

And you seem to have failed to notice a [cleft
sentence](https://japanese.stackexchange.com/q/19204/5010) embedded as a
clause. From this sentence:

> 気温が低くなる冬だけ、オウサマペンギンは外で散歩をすることができる。  
>  Only in winter, when temperatures drop, king penguins can take a walk
> outside.

...we can get this cleft sentence:

> オウサマペンギンが外で散歩をすることができる **のは** 気温が低くなる冬だけだ。  
>  It is only in winter, when temperatures drop, that king penguins can take a
> walk outside.

Once you've understood this, the rest should be straightforward to you:

> 水族館は「オウサマペンギンが外で散歩をすることができるのは気温が低くなる冬だけなので、いい運動になる」と言っています。  
>  The aquarium says that it will give king penguins a good workout because it
> is only in winter, when temperatures drop, that they can take a walk
> outside.

気温が低くなる (literally "when temperatures become low") is a small relative clause
that just says 冬 is a cold season. This may seem too obvious, but it
explicitly states that what matters for penguins is temperature.

