Logical Reasoning

PT112 · S3 · Q26 Before 1986 physicists believed they

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Before 1986 physicists believed they could describe the universe in terms of four universal forces.

Curious Fact

Why is there less gravitational attraction between bodies than our theories predict?

Explanation

Maybe there's a 5th universal force, which involves mutual repulsion between particles of matter.

Evaluate

Whenever we're trying to Solve a Causal Mystery and we have a potential hypothesis to do so, we're supposed to consider two different questions:

1. is there some Alternate Way we could explain / interpret the curious fact? 2. how plausible is the Author's Way of explaining it?

How else could we explain why the gravitational attraction between bodies is measured smaller than the predicted amount?

- maybe gravity isn't as strong as we think it is? - maybe the measuring devices were off? - maybe there's some interaction with the other 3 known forces that would explain it?

How plausible is the idea that there is a 5th force that deals with mutual repulsion between particles of matter?

- do any other experiments suggest such a force? - would such a force resolve any other physical mysteries we have? - is there any mathematical modeling of such a force?

Goal

Since this is Strengthen, we want to either rule out an alternate way to explain the curious fact (e.g. ) or increase the plausibility of the presented explanation, that there is fifth force that involves mutual repulsion between particles of matter.

26.

Which one of the following, if true, most strengthens the argument that there is a fifth universal force?

  1. The extremely sophisticated equipment used

    Almost No Impact

    Maybe this answer makes us feel slightly more trust in the accuracy of the measurements? It would be harder to say, "the real reason that gravitational attraction was measured as less than predicted is because the equipment we used to measure it was busted", if we know that the scientists are using extremely sophisticated equipment that isn't even 20 years old. But saying, "this equipment wasn't available before the 1970s" doesn't really tell us anything. Who cares if it was available? It doesn't really matter; we just want to know if we can trust the measurements, and this answer doesn't address the accuracy of the measurements.

    14% picked this

  2. Correct

    No previously established scientific results

    Why this is right

    This weakly strengthens, but it ends up being the strongest answer, since everything else does nothing or goes the wrong way. If we are considering positing a brand new force to explain these mysterious measurements, we would hope that it wouldn't be contradicted by any of our established existing science. This is really just a Necessary Assumption. Whenever the correct answer on Strengthen is a Necessary Assumption, it feels pretty weak (because it is). But you can feel how bad it would be if you negated the answer. If some previously established results would be incompatible (contradictory) with the notion of this 5th force, that would greatly, greatly diminish the plausibility of this 5th force theory. Overall, saying that this new hypothesis doesn't contradict anything that goes before it is not really positive support for it; it's just saying there's no big negative evidence against it. That probably seems like a very weak plausibility strengthener, and it is, but because we're talking about fundamental forces of the universe, it's slightly more impressive than normal. By that I mean, if we were wondering "How come Bob didn't show up to bowling tonight", and I hypothesize "maybe he went to Vegas", it doesn't strengthen that theory much so say, "nothing in Bob's past is incompatible with that hypothesis". But if we were judging something more fundamental and universal to Bob's life, like, "How come Bob has never gotten married?", and I hypothesize "maybe he wants to be a priest", that is a sweeping theory that is more likely to be contradicted by something in his past. If I'm way off, someone else will be able to say, 'Bob? The guy who never goes to church? Who says rude, objectifying things about women? Who doesn't believe in God? Who said he wants to own his own Fortune 500 company some day?' Because the marriage question (and because the future-priest hypothesis) is more fundamental to Bob's entire existence, it's a little more impressive if we say, "You know ... nothing in Bob's past would contradict that idea". So I think that's part of how we're supposed to think this answer choice, which really just says "we don't have any existing science that would contradict this theory", is meant to be seen as somewhat impactful.

    Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.

    71% picked this

  3. Some scientists have suggested that

    Weakens, if anything

    This is an alternate explanation -- "It's not a 5th force that explains this; it's a quirk of gravity we just don't understand, but it's still explainable by the 4 fundamental forces."

    5% picked this

  4. The experiments were conducted by

    Weakens

    This provides an alternate explanation for the curious fact -- the measurement of gravitational attraction wasn't smaller because of a 5th, repellant force, it was because we couldn't really get any precise measurements given the weird gravitational variables where the experiments took place.

    8% picked this

  5. The fifth universal force was

    No Impact

    The fact that this hypothesis was posited during a bold and exciting era of theoretical physics doesn't have anything to do with whether or not this hypothesis is correct.

    2% picked this

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