• Science has made many major advances this century, and
• Scientists made some fundamental discoveries in the 18th century.
• He puts to good use things that other people have thrown away, and
• I threw away most of my old books when I moved house.
When we report that someone has recently invented, produced, discovered or written something we use the present perfect. When we talk about something that was invented, etc. in the more distant past we use the past simple. Compare: [Quando nós relatamos que alguém recentemente inventou, produziu, escreveu ou descobriu algo, nós usamos o presente perfeito. Quando falamos de algo que foi inventado, etc, no passado mais distante usamos o passado simples. Compare:]
• Scientist have discovered that, all over the world, millions of frogs and toads are dying.
• It is often said that Hernan Cortes ‘discovered’ Mexico in 1519.
• Two schoolchildren have invented a device for moving large objects up flights of stairs.
• Chinese craftsmen invented both paper and printing.
Sometimes it makes very little difference to the main sense of the sentence if we think of something happening in a period of time up to the present or at a particular, finished time in the past: [Às vezes faz muito pouca diferença para o sentido principal da sentença, se pensamos em algo que acontece em um período de tempo até o presente ou num tempo específico, concluído no passado:]
• The research is now complete and the experiment was (or has been) a success.
• Does it concern you that you failed (or have failed) the test?
• I'm sure I read (or I have read) somewhere that he died in a plane crash.
We can use either the present perfect or the past simple to talk about repeated actions or events. If we use the present perfect, we often suggest that the action or event might happen again. [Podemos usar o presente perfeito ou o passado simples para falar sobre as ações repetidas ou eventos. Se usamos o presente perfeito, que muitas vezes sugerem que a ação ou evento poderia acontecer novamente.]
Sometimes we emphasise this with phrases such as so far and up to now. If we use the past simple, it suggests that it is finished and won’t happen again. Compare: [Às vezes, Nós enfatizamos isso com as frases tais como “as far” e “up to now”. Compare:]
• Timson has made 13 films and I think her latest is the best, and
• Timson made 13 films before she was tragically killed in a car accident.
• Lee has represented his country on many occasions, and hopes to go on to compete in the next Olympics, and
• Lee represented his country on many occasions, but was forced to retire after an injury.
We can use both the present perfect and the past simple to talk about states. We use the present perfect to talk about a state that existed in the past and still exists now, and we use the past simple if the state no longer exists. Compare: [Podemos usar tanto o presente perfeito e passado simples para falar sobre os estados. Nós usamos o presente perfeito para falar de um estado que existiu no passado e ainda existe hoje, e usamos o passado simples, se o estado não existe mais. Compare:]
• I have known him most of my working life. (I am still working) and
• I knew him when we were both working in Rome.
• We have belonged to the tennis club since we moved here. (We still belong to it.) and
• We belonged to the tennis club in the village we used to live in.