Questions & Answers about Es imposible terminar hoy.
Because Spanish often uses the pattern es + adjective + infinitive to make general statements like:
In English, we usually say It is impossible to finish today, with a dummy subject it. Spanish does not need that kind of subject here, so it simply starts with es.
Here, ser is used because the sentence is making a general statement about possibility: finishing today is impossible.
With ser, Spanish often expresses definitions, general characteristics, or impersonal judgments:
You may sometimes hear está imposible in everyday speech, especially in Spain and Latin America, but that usually sounds more colloquial and refers to a situation being impossible right now or in practice, for example:
- El tráfico está imposible. = The traffic is impossible / awful.
For this sentence, es imposible is the standard and neutral structure.