Study: Time Travel Possible but Cannot Change Past

Category: Human Interest


Unlocking Word Meanings

Read the following words/expressions found in today’s article.

  1. theoretically / ˌθiəˈrɛt ɪ kə li / (adv) – in a way that relates to the ideas about a particular topic rather than the application of those ideas

    Theoretically, prices will go down if there is too much supply.

  2. subsequent / ˈsʌb sɪ kwənt / (adj) – following or happening after something else

    The effect of the economic crisis will be felt in subsequent years.

  3. collide / kəˈlaɪd / (v) – to crash into something with force

    He forgot to hit the brakes and collided with another car.

  4. course / kɔrs / (n) – the path or direction of someone or something that is moving

    The captain planned the ship’s course before sailing.

  5. paradox / ˈpær əˌdɒks / (n) – a situation that consists of two opposite things that seem impossible to exist together

    The idea of drinking hot tea to cool you down is a paradox.


Read the text below.

Researchers are claiming that time travel is theoretically possible but cannot change past events.

According to theoretical physics, if a person traveled to a time in the past and tried to change things, subsequent events would correct any efforts to change the past.

To explain their findings, the researchers used the “billiard-ball model,” which visualizes the idea of “cause and effect” as a series of colliding billiard balls, and a round billiard table as a closed time-like curve. In this model, one can imagine a set of billiard balls placed on the table. If one ball is pushed from a particular position, it moves around the table, colliding with other balls in a certain pattern.

Theoretical Physicist Yasunori Nomura explained that even if the ball’s course is disrupted, its collision with other balls will enable it to return to its original path as if the disruption did not happen at all.

Citing a recent event as an example, scientist Fabio Costa said that if anyone traveled in time and tried to stop Covid-19’s first patient from getting the virus, that person would fail. He explained that preventing someone from getting the virus would create a paradox because interfering with that past event might also eliminate the reason to go back in time and stop the spread of the virus. While the person who went back in time might successfully prevent the actual first patient from being infected, he might get the virus himself and become the first patient, or cause someone else to become that patient.

Viewpoint Discussion

Enjoy a discussion with your tutor.

Discussion A

• Do you agree with the researchers’ claim that it’s impossible to change the past? Why or why not?
• Why do you think some people want to change the past? Explain.

Discussion B

• If time travel were indeed possible, would you like to try it? Why or why not?
• Do you think people should consider past experiences (e.g. previous mistakes, things that worked) when deciding future actions? Why or why not?