We are in a hallway on the third floor of the NASAL observatory building.<\/p>\n\n\n\n
Banani: But then\u2026 this “universologic principle”\u2026 I don\u2019t even know what that is.<\/p>\n\n\n\n
Papaia: It\u2019s called \u201ccosmological,\u201d Banani! The cosmological principle.<\/p>\n\n\n\n
Banani: We\u2019re about to get fired over something we can\u2019t even pronounce correctly!<\/p>\n\n\n\n
Ravioli: You\u2019re right, Banani! I\u2019d rather it had been for that unexcused absence last Friday!<\/p>\n\n\n\n
Papaia: Look, we haven\u2019t been fired yet. And you should know that the cosmological principle is the foundation of modern cosmology. It states that the universe is both homogeneous and isotropic. <\/p>\n\n\n\n
Ravioli: Homogeneus?<\/p>\n\n\n\n
Banani: Isotropic?<\/p>\n\n\n\n
Papaia: Yes! Homogeneity means the universe looks the same to all observers, while isotropy means the universe looks the same in all directions.<\/p>\n\n\n\n
Banani: Oh! So it\u2019s not as complicated as it sounds!<\/p>\n\n\n\n
Ravioli: True! Why did they use such a difficult word for something so simple?<\/p>\n\n\n\n
Banani: I heard that the farther we look at distant stars, the further back in time we\u2019re looking. Is that true?<\/p>\n\n\n\n
Papaia: You didn\u2019t know that? But that\u2019s something we use every day!<\/p>\n\n\n\n
Banani: Hey! Our agreement is to do what you tell us, not to understand it!<\/p>\n\n\n\n
Papaia: Yes, but I thought\u2026 Never mind, Banani. Just think about this: light moves at a certain speed. When an object is close, we see it in real time, but imagine what happens when we look at a star billions of kilometers away\u2026<\/p>\n\n\n\n
Banani: \u2026 the light has to travel all that distance!<\/p>\n\n\n\n
Papaia: \u2026 and it takes time.<\/p>\n\n\n\n
Banani: I still don\u2019t get it.<\/p>\n\n\n\n
Papaia: When the starlight reaches us, we see the light emitted at the moment it left, not in real time.<\/p>\n\n\n\n
Banani: So you\u2019re saying the sun we see now isn\u2019t the sun as it is now?<\/p>\n\n\n\n
Papaia: By that logic, no. The sun we see on Earth is how it looked several minutes ago.<\/p>\n\n\n\n
Banani: And when we look at the stars?<\/p>\n\n\n\n
Papaia: It depends. We\u2019d see images more and more remote in time depending on the distance\u2014years for closer stars, but thousands or even millions of years for the more distant ones.<\/p>\n\n\n\n
Banani: So, following that logic, if we could look far enough, we\u2019d see\u2026 the universe forming.<\/p>\n\n\n\n
Papaia: That\u2019s the reasoning we use every day in our calculations.<\/p>\n\n\n\n
Banani: But the Hubble tension challenges this reasoning, as do the new discoveries from the Webb telescope.<\/p>\n\n\n\n
Papaia: Light isn\u2019t as simple as we might imagine. For example, it behaves strangely when the gravitational field of a star is very strong. Due to spacetime curvature, we\u2019ve observed the same galaxy\u2019s image copied four times in different positions.<\/p>\n\n\n\n
Banani: That\u2019s really weird! How did that happen?<\/p>\n\n\n\n
Papaia: Didn\u2019t I just explain it to you?<\/p>\n\n\n\n
Banani: So, our reasoning might not be entirely correct.<\/p>\n\n\n\n
Papaia: In Genesis, we read that God created light on the first day. This account suggests Adam could see the stars in the sky from the sixth day of creation, when he was made. Somehow, God made the starlight reach us.<\/p>\n\n\n\n
Banani: How did He do that?<\/p>\n\n\n\n
Papaia: There are various hypotheses, but no one knows for sure yet. Maybe we\u2019ll know when we understand light better.<\/p>\n\n\n\n
Ravioli: Hey, don\u2019t you think we\u2019ve already passed that door?<\/p>\n\n\n\n
Banani: I think we\u2019re going around in circles!<\/p>\n\n\n\n
Ravioli: Look, there\u2019s a janitor over there. Let\u2019s ask him. Maybe he knows.<\/p>\n\n\n\n
The four approach the janitor to ask for directions.<\/p>\n\n\n\n
Banani: Excuse me\u2026 do you work here?<\/p>\n\n\n\n
Janitor: No! I was taking a walk outside the observatory and thought, \u201cWhy not clean the third-floor hallways!\u201d So I went home, grabbed my broom\u2026 and here I am!<\/p>\n\n\n\n
Ravioli (surprised): Really?<\/p>\n\n\n\n
Igor is quietly laughing.<\/p>\n\n\n\n
Banani: Please, don\u2019t joke. The boss sent us here for a test. Do you know where the room is?<\/p>\n\n\n\n
Janitor: Sorry for the joke! Yes, I work here. You want to know where the room is for\u2026 \u201cthe\u201d test?<\/p>\n\n\n\n
The four lower their gaze slightly, embarrassed.<\/p>\n\n\n\n
Banani: Yes, yes! For\u2026 \u201cthe\u201d test!<\/p>\n\n\n\n
The janitor\u2019s smile suddenly vanishes, replaced by an expression of terror.<\/p>\n\n\n\n
Janitor (terrified): Oh! Stop! Keep your distance! Why aren\u2019t you wearing masks?<\/p>\n\n\n\n
The janitor takes a step back.<\/p>\n\n\n\n
Janitor (covering his face with one hand and pointing to a room with the other): It\u2019s over there! It\u2019s over there!<\/p>\n\n\n\n
The janitor quickly walks away down the hallway.<\/p>\n\n\n\n
Papaia: What strange behavior!<\/p>\n\n\n\n
Banani: Maybe he thinks madness is contagious!<\/p>\n\n\n\n
Ravioli (indignant): I\u2019ve never felt so humiliated in my life!<\/p>\n\n\n\n
Igor: Imagine if, besides madness, Papaia\u2019s distraction were contagious\u2026 we\u2019d all end up going in circles\u2026 in the hallway!<\/p>\n\n\n\n