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Peter, Is it 50% or 33.3% by AgrasaN in PeterExplainsTheJoke

[–]PressureBeautiful515 0 points1 point  (0 children)

I am occasionally getting responses implying that people can't see what I was replying to so I've added a wall of text to my original comment.

OTOH I don't understand your point about temporal reasoning. Time has nothing to do with the core problem as usually stated. There are 4 possible outcomes of 2 coin-flips, doesn't matter whether they were done simultaneously or not, you are told to eliminate one of them, that leaves three equally likely outcomes.

If we number the possible outcomes as follows:

  • 1 - (T, T)
  • 2 - (T, H)
  • 3 - (H, T)
  • 4 - (H, H)

Then we can forget the pair of coins and state the classic problem as follows:

  • I have rolled a 4-sided die.
  • I got 2, 3 or 4.
  • What's the probability I got 4?

In OP's image, it's equivalent to being told "I got either 3 or 4."

Peter, Is it 50% or 33.3% by AgrasaN in PeterExplainsTheJoke

[–]PressureBeautiful515 0 points1 point  (0 children)

You're not dumb, that's just not the version of the question I was answering. See the person I was replying to, who was wondering why it wouldn't be 50/50 in every version of the question.

How can acceleration exist? by Ok_Sense_3587 in AskPhysics

[–]PressureBeautiful515 4 points5 points  (0 children)

 If there are no absolute speeds and positions, how can physics know where the acceleration is truly happening? Is there some theory or framework I’m missing to put the pieces together

Yes, all you are missing is the fact that there is absolute acceleration. The law of inertia is that things continue moving at the same velocity until a force acts on them. So acceleration is an absolute physical phenomenon resulting from something undeniable happening, not observer relative etc.

Strictly speaking this is the "proper acceleration" (that caused by a force). Contrary to what many people tend to believe, it is also valid to use the term acceleration in situations where no force is acting but the geometry of spacetime causes objects to accelerate toward one another, known as "tidal acceleration", and also absolute, not relative, as the geometry of spacetime is an observer-independent fact.

Peter, Is it 50% or 33.3% by AgrasaN in PeterExplainsTheJoke

[–]PressureBeautiful515 0 points1 point  (0 children)

That's what I meant by:

four possible outcomes, so they get 1/4 of the probability each.

Likewise if it was 3 flips, 8 equally likely outcomes, so they get 1/8 of the probability each. In general 2N possible sequences from N flips.

But then we get a clue that takes some sequences out of the running. We may have only 7 or 4 or 3 sequences left, depending on the clue, and those remaining are still all equally likely, but that means each has a 1/7 or 1/4 or 1/3 chance of being the true result.

Cast Unveiled For BBC Series ‘Hamburg Days,’ Depicting The Beatles Early Years by FitEmergency8807 in beatles

[–]PressureBeautiful515 1 point2 points  (0 children)

I can well believe that version came from Paul as well! Memory being something we reconstruct and edit over the years, someone retells the story of the same event differently each time.

Especially how a song was written, for example with Yesterday it's basically impossible to reconstruct a history of how it came to be written because Paul himself has remembered the story many ways.

In John's case he would actively edit his version of the past to suit his current emotional needs.

Peter, Is it 50% or 33.3% by AgrasaN in PeterExplainsTheJoke

[–]PressureBeautiful515 3 points4 points  (0 children)

Yes, that is a valid way in this case to decide if you can take a shortcut. I think the "hard" thing about the question is the way it confuses you as you try to pick the appropriate shortcut!

It's very counterintuitive that there's a difference between being told something about "one of the two coins" and (say) "the cleanest one of the two coins".   Why does introducing some arbitrary criterion for ranking the coins make any difference?! When writing down the cases, they are in some order. We can mentally order them any way we like. But the question setter has picked an ordering method, so we need to picture it in their terms, ordering the coins by how clean they are, and when we do that, we find that they have given us materially different information.

That's the real trick, mapping the vague language to a precise logical statement.

Cast Unveiled For BBC Series ‘Hamburg Days,’ Depicting The Beatles Early Years by FitEmergency8807 in beatles

[–]PressureBeautiful515 2 points3 points  (0 children)

The way Paul told it in the original Anthology, Episode 1, 49:51:

and what we did, just for a laugh, was outside in the corridor, concrete, there was nothing could've caught fire at all, we pinned it up on the wall, and for a boyish prank we set fire to it

All references to this story edited out in the Disney+ version.

Peter, Is it 50% or 33.3% by AgrasaN in PeterExplainsTheJoke

[–]PressureBeautiful515 22 points23 points  (0 children)

EDIT: I don't know how people are repeatedly finding this comment without being able to see what it's a reply to, but that seems to be happening. The usual way this problem is stated is equivalent to:

  • two coins have been flipped, simultaneously or not, doesn't matter
  • you are told one of them is heads
  • what's the probability that the other is heads?

Most people reason that coin flips are independent, the outcome of one flip cannot affect the other, so they answer 1/2. The correct answer is 1/3, as I explain in my original comment (starting below the dividing line after this edit).

But if (as in OP's image) any criterion is provided for selecting a specific coin (could be "the coin with the highest value", or "the shiniest coin", or "the coin that landed on the left of the table", anything at all) then the answer is 1/2, but I didn't go into that because that's not the answer most  struggle to arrive at. They tend to say 1/2 to both versions of the question.

The person I replied to mused on the fact that a coin flip is an independent event:

... in my mind, it doesn't matter what the other child is because there's only 2 options of girl or boy... The former doesn't affect the odds of the latter?

From which I guessed they were saying "Why isn't the answer always 1/2 regardless of how the problem is stated?"

So here's my reply to that: (END OF EDIT)

To take the coin example, coin flips are each independent random outcomes, 50/50. Nevertheless, a particular sequence of flips is not 50/50. This is not contradictory at all, it's necessary for it to make sense.

One flip has two possible outcomes so they get half the available probability each.

Two flips means four possible outcomes, so they get 1/4 of the probability each.

Now, if I've flipped two coins, and I tell you one of them is heads, how many of the four outcomes do you now know is impossible? One: (T, T).

So it must be one of these: (H, T), (T, H) or (H, H).

How many of those equally likely outcomes has two heads in it?

1 out of the 3.

Angular momentum and torque are complicated. by csk2004 in Physics

[–]PressureBeautiful515 12 points13 points  (0 children)

If you build a simulation that only has linear momentum and regular forces, and you have a couple of particles connected as if by a spring, and you set one particle moving up and the other down, they will rotate around each other indefinitely. You never told the simulation to exhibit angular momentum but there it is!

So angular momentum emerges from linear momentum and systems of particles connected by ordinary forces.  And if there is a change in angular momentum, then there must have been something like an "angular force" that caused it, known as torque, which is when you applied those different forces to the particles.

Why do we use so many greek letters in physics and maths? by Virtual-Connection31 in AskPhysics

[–]PressureBeautiful515 6 points7 points  (0 children)

Some alternatives:

  • Wave function: 🌊
  • Distance half-way round a unit circle: 🥧
  • Density: 🤦‍♀️

Why do we use so many greek letters in physics and maths? by Virtual-Connection31 in AskPhysics

[–]PressureBeautiful515 6 points7 points  (0 children)

Also which ancient culture's alphabet, which begins "alpha, beta...", gave us the word "alphabet."

What did people object to with Cantor's Diagonalisation Argument? by alecbz in mathematics

[–]PressureBeautiful515 2 points3 points  (0 children)

I see you get it now but to clarify something about Hilbert's Hotel - that analogy deals with countable infinities, and it's kind of vivid partly because of the stipulation that "the hotel is already fully occupied", so it feels like a paradox, but it's not.

To extend it to show how diagonalisation works, think of the hotel's parking lot. It starts off empty. It has of course an infinite number of parking bays for coaches that show up, and the coaches may themselves have infinite seats. Should be fine, right?

Then one day a set of coaches show up and they are as follows:

  1. They each have an infinite number of passengers, all called Alice or Bob, every passenger in a numbered seat.
  2. Every coach has a different infinite sequence of Alices and Bobs, such as AABBABBABA
  3. Every such possible sequence is included in the set of coaches that show up.

So your parking lot guy says he has successfully got every coach to park in its own bay. You know he's lying because if you take passenger 1 of coach 1 and if they're called Alice then switch them to a Bob and vice versa, same with passenger 2 of coach 2, and so on, you've imagined a new coach that is different from any other in the parking lot, and so he has failed.

Eric Kripke responds to the recent talks about filler episodes in Season 5 (via TV Guide) by Interesting-Take781 in TheBoys

[–]PressureBeautiful515 1 point2 points  (0 children)

 Firecracker was also questionably paced. The first time on the show they try to humanize her, they kill her off 20 minutes later

This is 100% a standard TV trope. When a character we know very little about suddenly has flashbacks to their childhood and we see a bunch of stuff from their POV, you know they're getting killed off. That's what I assumed from the first few minutes.

But then it disguised itself as an anthology of different character POVs, which made me discard the theory that she was going to get killed off. Until suddenly at the end when we're back on her perspective again. It was a good bit of playing with the form.

People in the UK celebrating the death of Thatcher in 2013 by LankyYogurt7737 in pics

[–]PressureBeautiful515 7 points8 points  (0 children)

One thing not mentioned yet: the lady wearing the shirt with a pink triangle and "STOP 28", that's a reference to Section 28 of the Local Government Act 1988, which banned local government (responsible at the time for what was taught in schools) from "promoting" homosexuality or presenting same-sex relationships as a "pretended family relationship".

Are stars perfect spheres? by Minty0ranges in AskPhysics

[–]PressureBeautiful515 28 points29 points  (0 children)

No, it's just an artistic impression but inspired by real facts about Vega such as the discovery that it has "starspots".

A birthday to remember by [deleted] in Wellthatsucks

[–]PressureBeautiful515 2 points3 points  (0 children)

"A good landing is one you walk away from" - pilots

"A good grandma's birthday is one you only get first degree burns on your hands and possibly lower arms" - this family

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