Episode 5: The Nurse
We are in the room indicated by the janitor.
The four enter the room. It’s a small waiting area with a closed door at the back. Papaia knocks on the door. After a few seconds, a nurse appears, wearing a mask and gloves.
Nurse: Good morning. How can I help you?
The four look visibly embarrassed.
Papaia (whispering.): The boss sent us here to take “the” test.
Nurse: Ah! I see. No need to be embarrassed. It happens to everyone at some point.
Banani: Really?
Nurse: Of course! Don’t worry. By the way, let me check your names in the registry… Hmm, that’s strange! I can’t find you.
Papaia: What now?
Nurse: Normally, I wouldn’t be able to let you take the test without registration, but since it’s the boss who sent you, I’ll make an exception.
Papaia: Oh, thank you!
Nurse: If you pass me your ID cards I’ll add your names to the registry.
The four hand over their ID cards to the nurse, who writes their names into the registry.
Nurse: All right, before we start, can you please tell me what symptoms you’re experiencing?
Ravioli (embarrassed): Excuse me, but I thought there’d be a bit more … privacy for this kind of thing.
Nurse: Ah, yes, I see! Of course, you’re right! You can enter my office one at a time. Who wants to go first?
None of the four get up from their chairs.
Nurse (pointing at Ravioli): Then you go first!
Ravioli: Me?
Ravioli reluctantly gets up and enters the room with the nurse.
Banani: I’ve never seen such an unusual psychologist before!
Papaia: I agree. The gloves and mask? And the privacy of the session… doesn’t seem optional to me!
Banani (curious): Speaking of masks… Hey Papaia, I’m starting to have a doubt.
Papaia: What doubt?
Banani: You see, earlier, the janitor scolded us for not wearing masks. And now the psychologist is also wearing one.
Papaia: So what? Where are you going with this?
Banani: … Could it be that our problem is really… contagious?
Igor: Oh, yes! Banani’s “problem” is indeed … contagious! And it seems like I’m the only one here immune… to his stupidity!
While Papaia and Banani wait for Ravioli, who is taking “the” test, they seize the opportunity to continue their conversation about Hubble tension.
Banani: Are you sure, Papaia, that you measured Hubble’s constant correctly?
Papaia: I’m 100% sure! We repeated the measurements many times in every possible way. You were there too, don’t you remember?
Banani: Yes, but in the end, what’s the problem if we get two slightly different values?
Papaia: You see, Banani, we measured the same constant in two different ways. The first with redshift, the second with the CMB background radiation. If this constant is truly constant, the values should be very close to each other.
Banani: I still don’t get it.
Papaia: Let me give you an example. Imagine measuring Earth’s gravitational acceleration, which we call “g.”
Banani: You mean the force that keeps us grounded and makes everything fall to the ground?
Papaia: More or less… “g” represents the value of the acceleration caused by that force.
Banani: Pretty much the same thing, right?
Papaia: Not exactly: to calculate the force, we also need mass to do the calculation: mass times acceleration. But in this case, we’re just measuring the acceleration “g.”
Banani: I think I get it.
Papaia: And the value of “g” on Earth’s surface is constant, meaning it doesn’t change over time, and it’s about 9.81 meters per second squared.
Banani: Yeah, I think I’ve heard that number before, maybe at school.
Papaia: Essentially, when anything is in free fall, its speed increases by about 9.81 meters per second every second.
Banani: I think I’m following you.
Papaia: Great! So, we can measure this value in various ways. For example, using the oscillations of a pendulum or a ball rolling down an inclined plane. These are two independent methods to measure the same thing, “g.”
Banani: I see. We’re using two measurement methods to measure the same quantity.
Papaia: Very good, I see you’re getting it now. So, both with the pendulum and the inclined plane, we should, and do, always get the same result: 9.81 meters per second squared.
Banani: But that’s not what happens with Hubble’s constant?
Papaia: Exactly! That’s the issue. When we measure Hubble’s constant with redshift, we get 67.4 km/s/Mpc (kilometers per second per megaparsec). But when we measure it with the CMB, we get 73 km/s/Mpc.
Banani: But those are different values!
Papaia: Exactly, and we have an error greater than 8%!
Banani: Couldn’t it be the instruments, as the boss says?
Papaia: No, Banani! Let me explain. According to the theoretical model, we expect a value of 67.5 km/s/Mpc. This value is perfectly confirmed by the most advanced spectroscopes, which have a maximum error margin of 1%. But when we measure the same constant with the CMB method, using advanced instruments like the Hubble and Webb space telescopes, we get a value of 73 km/s/Mpc, despite their 1% error margin.
Banani: Surely 8 percent is off the charts!
Papaia: That’s why something doesn’t add up in the Big Bang model.
Igor: I agree, the Big Bang doesn’t add up! Just like this situation doesn’t add up. In fact, we have found a nurse… as a psychologist!