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01

RAP's Core Elements

Definition

Why can't you leave property to 'my descendants forever'?

Just as contract law has statutes of limitations to prevent claims from lingering indefinitely, property law has a rule to prevent ownership from being tied up for an unreasonably long time.

What it is The Rule Against Perpetuities (RAP) is a common law legal principle that limits the duration of contingent future interests in property.

What it does It dictates that 'no interest is good unless it must vest, if at all, not later than twenty-one years after some life in being at the creation of the interest.' This means a property interest is void from the start if there's any possibility it won't become certain (vest) or fail within the…

Why it matters Understanding RAP is crucial for drafting wills, trusts, and deeds to ensure property dispositions are legally valid and achieve the grantor's intent. It applies whenever a property owner attempts to control ownership far into the future, particularly with contingent gifts.

Sources · 8
  • rule against perpetuitieslaw.cornell.edu
  • Understanding the Rule Against Perpetuities for Trustslearn.valur.com
  • Rule Against Perpetuitieslawshelf.com
  • Rule Against Perpetuities Explainedbarbri.com
Read the whole lesson →6 concepts in this lesson
How it works

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1

Hand it a topic

Type an idea or an offhand question. Choose how deep to go and what to explain it through.

Why nothing escapes a black hole
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Explain it through…
Everyday lifeCookingSports
Teach me
2

Read it as the app renders it

Every concept opens with the question it answers and an everyday anchor, then says what it is, what it does and why it matters - with the load-bearing phrases marked.

01

RAP's Core Elements

Definition

Why can't you leave property to 'my descendants forever'?

Just as contract law has statutes of limitations to prevent claims from lingering indefinitely, property law has a rule to prevent ownership from being tied up for an unreasonably long time.

What it is The Rule Against Perpetuities (RAP) is a common law legal principle that limits the duration of contingent future interests in property.

What it does It dictates that 'no interest is good unless it must vest, if at all, not later than twenty-one years after some life in being at the creation of the interest.' This means a property interest is void from the start if there's any possibility it won't become certain (vest) or fail within the…

Why it matters Understanding RAP is crucial for drafting wills, trusts, and deeds to ensure property dispositions are legally valid and achieve the grantor's intent. It applies whenever a property owner attempts to control ownership far into the future, particularly with contingent gifts.

3

Answer it from memory

Every attempt tells Nodebook what to bring back, and when. Try one - it is a real question from a lesson we publish.

Try it yourselfGravity as Spacetime Curvature

A satellite orbits Earth.

Which best explains its path?

A real question from “Light's Inability to Escape a Black Hole”

The receipts

Every sentence has a source. Here's one.

From the lesson “How large language models work”

A large language model takes text, splits it into smaller units called tokens, and predicts a probability distribution for what token should come next.

It generates text by choosing a token, adding it to the context, and repeating the process. It does not retrieve a finished sentence from a hidden book.

Read the whole lesson →
Sources · 3

Not a badge that says “cited”. The actual links, on the actual lesson.

In a 2025 randomised controlled trial, learners who studied with ChatGPT answered 57.5% of a surprise test correctly 45 days later. Learners who studied without it answered 68.5%.

Barcaui (2025), Social Sciences & Humanities Open 12, 102287

One trial: 120 undergraduates, randomly assigned to two groups (p = .002, Cohen's d = 0.68). Directional, not a law - we link it because we'd want to check it too.

See a real lesson →
The part other tools skip

Reading it is not remembering it.

A lesson you read once is mostly gone inside a week. A few well-timed attempts to recall it are the difference between having read something and knowing it.

With Nodebook’s reviewsRead once
allnone
Day 0Day 7Day 14Day 21
Illustrative - the Ebbinghaus shape, not your data. Reviews on days 1, 3, 7 and 16.
How it bends

Recall it, then be asked again.

Two surfaces do the work. One makes you retrieve the idea from memory instead of re-reading it; the other decides when you see it next, per concept, so the ideas you are shaky on come back and the ones you own leave you alone.

Recall LockThe event horizon
Why can light not escape past the event horizon?
Escaping would require moving faster than light, which is not possible.
Ideal answer revealedCompare the idea, not the wording.
Got itAlmostMissed

We'll bring this idea back in 4 days.

You explain it in your own words first, then reveal and rate what you actually remembered. That rating - not a page view - sets the next review. Explore active recall →

Ready to refresh1 concept
Neural Networks
BackpropagationLast recalled 6 days ago
Refresh this memory →

Nothing else needs your attention right now.

When something is due you get one clear action; when your memory map is stable it stays quiet. Prefer to listen? Any lesson becomes chaptered narration, and Audio Recall puts the same pauses between chapters. Meet Audio Recall →

The part that keeps you coming back

Show up. It decides the rest.

You never plan a revision session. Nodebook works out which ideas are slipping and asks about those - so the whole job is to open it and answer.

Today, decided for you
Fourteen cards, three lessonsBayes' theorem · 6 due since TuesdayEnzyme kinetics · 5 due todayNeural networks · 3 new, never tested

Picked from what you have actually started to forget - not a syllabus, and not a quota to farm.

One word, from your lessons
From Bayes' theorem

The word is drawn from your own lessons - the one they lean on hardest - so guessing it is revision. Six tries, one free hint, and the lesson it came from is one tap away.

Answer them in a row
10in a row
  • 3 in a row+5 XP
  • 5 in a row+10 XP
  • 10 in a row+25 XP
  • 25 in a row+50 XP

Only closed-book answers count, so the number means something. A wrong answer resets it; a run carries across days.

Climb the leaderboard
  1. 1Priya18,240
  2. 2Marcus16,905
  3. 3You15,480
  4. 4Ines14,220

Ranked by what you have proven you remember, not by hours logged. Illustrative names and numbers; the board itself is real.

It compounds

Every lesson becomes a node in your book.

Nothing you compile is spent. Each lesson is broken into concepts, and a concept that turns up in a second lesson doesn’t repeat - it connects. Six subjects stop being six folders and start being one book.

Public-key cryptoOne-way functions
Week one · 3 lessons
Public-key cryptoOne-way functionsPhotosynthesis
Week five · 8 lessons
Public-key cryptoOne-way functionsHash functionsNeural networksCross-entropyPhotosynthesisBayes’ theoremEntropy
Week ten · 14 lessons · one graph
ideas within one lesson the same idea in two subjects
Concepts
38
Connections
62
Lessons
14
Busiest idea
6

“Entropy” is doing the most work in this one - it came up in 6 different lessons, which is how machine learning, quantum physics, cryptography and cell biology ended up in the same graph. The library above is an example, not a real person’s. The drawing is not: it is the same layout engine the app runs, over the same shape of data it stores.

Pricing

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OpenTelemetry for LLM observability

Every lesson gets a cover. Pro lessons get one drawn for the topic, so your shelf looks like a shelf.

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The questions we'd ask.

How is this different from asking ChatGPT?
A chat answers and then forgets you. Nodebook writes a finite lesson from sources you can open, splits it into concepts, and brings each one back for a retrieval attempt days and weeks later. That second half is what decides whether you still know it next month. The full comparison →
Does it make things up?
Lessons are compiled from retrieved material, checked against it, and published with the source list attached. No language model is perfect, which is exactly why the links are on the page: you can open a source and check a sentence yourself instead of trusting us.
What counts as a lesson?
One compiled topic, at whatever depth you pick. Every lesson costs the same, so going deep is never more expensive than skimming. Free includes 3 a month; Pro includes 20.
What is Today's Nodle?
A daily word game built out of your own lessons, free on every plan. You get six guesses at a word your lessons lean on hardest; every letter you try comes back green, amber or grey, and one hint is free. Solve it and Nodebook names the lesson the word came from, quotes the sentence it lives in, and opens it in one tap. See today's →
How long does a compile take?
About 90 seconds. You can close the tab while it works - the lesson is waiting in Learn when you come back.
Can I cancel?
Yes, from Settings, in one tap. Pro keeps working until the end of the period you have already paid for, and nothing you have compiled is taken away afterwards.
Is there an iPhone app?
Yes - Download it from the App Store. The web app runs on your phone too, including audio lessons.
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