Three scientists\u2014Papaia, Banani, and Ravioli\u2014and their assistant Igor work at the NASAL observatory. They come across some interesting books and start getting into creationism. But their bosses don\u2019t like this new interest and send them to take a psychological test, which they must pass to keep their jobs. But Papaia has forgotten where the psychologist\u2019s office is.<\/p>\n\n\n\n
We are in a hallway on the third floor of the NASAL headquarters, where they are searching for the psychologist office.<\/p>\n\n\n\n
Banani: But then… this “Universologic\u201d principle… 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
\ud83e\udd23\ud83e\udd23\ud83e\udd23<\/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
\ud83e\udd23\ud83e\udd23\ud83e\udd23<\/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: Homogeneous?<\/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… 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…<\/p>\n\n\n\n
Banani: … the light has to travel all that distance!<\/p>\n\n\n\n
Papaia: … 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… 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
Igor: Papaia is explaining to us that light isn’t as simple as we might imagine. <\/p>\n\n\n\n
It reminds me of our everyday troubles.<\/p>\n\n\n\n
\ud83e\udd23\ud83e\udd23\ud83e\udd23<\/p>\n\n\n\n
… Just when you think you’ve figured them out, they start behaving like waves *and* particles.<\/p>\n\n\n\n