Learn Hardcore Japanese: genzituteki ni kangaeru to, mainiti kaigairyokou wo suruno ha muri da to omoimasu. - Realistically speaking, I think it’s impossible to travel abroad every day.

Nuance: it’s not a hypothetical “if” like もし〜たら, but more like a natural-result “when you think realistically, the conclusion is 〜”. In English we might say:

“Realistically speaking, 〜”
“When you think about it realistically, 〜”

That’s what 考えると expresses here.

Why is there no particle after 毎日?

Time expressions like 毎日 (every day), 昨日 (yesterday), 来週 (next week) often appear without a particle when they simply indicate when something happens.

So all of these are natural:

毎日　海外旅行をする。 – Travel abroad every day.
昨日　映画を見た。 – (I) watched a movie yesterday.
来週　日本へ行きます。 – (I) will go to Japan next week.

You can sometimes add に (e.g., 毎日に), but that usually adds some special nuance and is much less common for a plain “every day” meaning. In this sentence, 毎日 without a particle is the normal, neutral choice.

Why is it 海外旅行をする instead of something like 海外に旅行する?

Japanese often treats some nouns as “action nouns” that combine with する:

勉強をする – to study
運動をする – to exercise
旅行をする – to travel / take a trip

海外旅行 is “overseas travel / an overseas trip”, so:

海外旅行をする = “to do overseas travel” → “to travel abroad / take trips overseas”

You can say 海外に旅行する, but:

海外旅行をする is more set-phrase-like and common when talking about “overseas trips” as a kind of activity.
海外に旅行する is grammatical but sounds a bit more like “to travel to overseas (places)” and is less fixed as a chunk.

In this sentence, 海外旅行をする sounds the most natural and idiomatic.

What is the role of の and は in 海外旅行をするのは?

Here we have:

海外旅行をする – to travel abroad
〜の – nominalizer (turns the verb phrase into a noun-like thing)
〜のは – “the act of doing X / doing X is …”

So:

海外旅行をするのは
→ “(As for) doing overseas trips,”
→ “(The act of) traveling abroad (every day) is …”

Why の?
の nominalizes the entire phrase 海外旅行をする, so it can function as the topic of the sentence.

Why は?
は marks that nominalized phrase as the topic:

海外旅行をするのは無理だ
→ “As for traveling abroad (every day), it’s impossible.”

Compare:

海外旅行をすることは無理だ。 – also correct; こと is another nominalizer.
- の is a bit more conversational/natural sounding here.
- こと can feel a bit more formal/abstract.

So するのは = “doing (it) is …” and sets up what you’re going to comment on.

What exactly does 無理だ mean here? Is it just “impossible”?

無理（むり）だ literally means something like:

impossible / not feasible / unreasonable / overdoing it

In this sentence, it’s not necessarily “physically impossible” in an absolute sense, but more:

unrealistic
not practical
too much to expect / beyond what’s reasonable

So 毎日海外旅行をするのは無理だ could be understood as:

“Travelling abroad every day just isn’t realistic.”
“It’s not feasible to go on overseas trips every single day.”

無理 often carries the nuance that trying to do it would be a strain, too costly, or beyond normal limits.

What is the difference between 無理だ and できない in this kind of sentence?

Both can be translated as “can’t / impossible,” but the nuance is different.

できない – “cannot do,” often more straightforwardly about ability or possibility.
- 毎日海外旅行はできない。
  → “I can’t travel abroad every day.”
  → Focus on “I’m not able to / it’s not possible for me (for practical reasons like money, time, etc.)”
無理だ – “unreasonable / not feasible / too much / unrealistic.”
- 毎日海外旅行をするのは無理だ。
  → “Doing overseas trips every day is (just) not realistic.”
  → Emphasizes that the idea itself is beyond what’s reasonable or feasible.

So 無理だ sounds more like you’re judging the idea/plan as unrealistic, not just stating your own capability.

What does と思います add here? Why not just end with 無理です or 無理だ?

と思います = “I think (that) …”

In the sentence:

無理だと思います。
→ “I think (it’s) impossible / unrealistic.”

Functions:

Softens the statement
- Saying 無理だ alone can sound rather blunt or absolute: “It’s impossible.”
- 無理だと思います sounds more like a personal opinion: “I think it’s impossible.”
Politeness
- 思います is in ます-form → polite speech.
- This fits well with speaking to someone respectfully.
Hedging
- It makes the speaker’s judgment less direct and confrontational, which is common in Japanese.

So the whole sentence is something like:
“Realistically speaking, I think it’s impossible to travel abroad every day.”

Ending with just 無理です would still be polite, but more direct: “It’s impossible.”

The particle と appears twice: 考えると and だと思います. Are these the same と?

They are the same particle form (と), but they have different grammatical functions here.

考えると – conditional と
- Connects “think realistically” to the resulting conclusion.
- Meaning: “when/if you think (realistically), then …”
無理だと思います – quotative と
- Marks the content of what is thought/said.
- Structure: [clause] + と + 思います
- Meaning: “I think that [clause].”

So:

現実的に考えると、
→ “When/if we think realistically,”
毎日海外旅行をするのは無理だと思います。
→ “(I) think that traveling abroad every day is impossible.”

Same particle と, but:

first = conditional “when/if”
second = quotative “that” (marking the thought content)