Why doesn’t the time run backwards?

Noites no Observatório - Por que não Anda o Tempo para Trás?

Why doesn’t Time run backwards?

By Marina Cortês, of Instituto de Astrofísica e Ciências do Espaço (IA)

Why is future different from the past? The most evident fact about the world around us is that time is always running forward. We remember the past but not the future, we can change eggs into an omelet, but not an omelet into eggs, and our age increases, but never decreases.

However strange it may sound, our theories of contemporary physics have yet no answer to this question. In this talk, Marina Cortês will tell what we know about the origin of the direction of time and how to integrate it into our understanding of universe around us.

After the public talk, there will be a music and effects show projected on the planetary dome, and observations of the night sky with telescopes will run continuously until midnight, if weather conditions allow.

Watch the talk (in Portuguese) on IA’s channels on YouTube and Vimeo.



2.5 hours

Free entrance


Although the entrance is free of charge, the access to the activity requires a registration here.

Due to the growing audience attending our activities and the fact that some people give up without notice, an email will be sent asking for confirmation. The lack of a reply within 48 hours after the reception of this confirmation request will be taken as a dropout and the registration will be cancelled. For this reason, please check your email inbox regularly in order to confirm your attendance in the activity.

The observation of the night sky depends on the weather conditions. As this is run outside, we recommend the use of warm clothes.

The talk is given regardless of the observations. The Calouste Gulbenkian Planetarium will open its doors half an hour before the event starts.

The public talk is given in Portuguese.

Don’t miss an event

Follow us on the IA facebook page, twitter feed or subscribe to our newsletter (web form here on the sidebar or bottom of page if on a mobile device).


Planetário Calouste Gulbenkian - Centro Ciência Viva
Museu de Marinha
Praça do Império

How to get there

By car
GPS – 38.698140, -9.208919

By bus
714, 727, 28, 729, 751 e 201

By tram

By boat
Estação fluvial de Belém ( Transtejo)

Live broadcasting

You can watch the event from home and ask questions to the speaker visiting this online address.

The online broadcasting of the talks has the support of the Fundação para a Computação Científica Nacional (FCCN), a division of the Fundação para a Ciência e a Tecnologia (FCT).