Improve ledger header diagram, minimize discussion of skiplist which …

…is unused (and broken)

docs/learn/encyclopedia/network-configuration/ledger-headers.mdx

@@ -3,17 +3,49 @@ title: Ledger Headers
 sidebar_position: 30
 ---
 
-Every ledger has a header that references the data in that ledger and the previous ledger. These references are cryptographic hashes of the content which behave like pointers in typical data structures but with added security guarantees. Think of a historical ledger chain as a linked list of ledger headers:
+Every ledger has a header that references the data in that ledger and the previous ledger.
+These references are cryptographic hashes of the content which behave like pointers in typical data structures but with added security guarantees.
+Think of a historical ledger chain as a linked list of ledger headers.
+Time flows forward from left to right, hashes point backwards in time, from right to left.
+Each hash in the chain links a ledger to its previous ledger, which authenticates the entire history of ledgers in its past:
 
 ```mermaid
-stateDiagram
-    direction LR
-    Genesis --> LedgerHeader_1
-    LedgerHeader_1 --> ...
-    ... --> LedgerHeader_n
+flowchart RL
+    subgraph genesis["Genesis"]
+        direction LR
+        prev1["Prev: none"]
+        state1["Genesis state"]
+    end
+
+    subgraph block2["Ledger 2"]
+        prev2["Prev: hash(Genesis)"]
+        state2["Ledger 2<br/>transactions<br/>and state"]
+    end
+
+    subgraph block3["Ledger 3"]
+        prev3["Prev: hash(Ledger 2)"]
+        state3["Ledger 3<br/>transactions<br/>and state"]
+    end
+
+    subgraph dotdot["..."]
+    end
+
+    subgraph blockn["Ledger N"]
+        prevn["Prev: hash(Ledger N-1)"]
+        staten["Ledger N<br/>transactions<br/>and state"]
+    end
+
+
+    genesis ~~~ block2 ~~~ block3 ~~~ dotdot ~~~ blockn
+    prev2 --> genesis
+    prev3 --> block2
+    dotdot --> block3
+    prevn --> dotdot
+
 ```
 
-The genesis ledger has a sequence number of 1. The ledger directly following a ledger with sequence number n has a sequence number of n+1.
+The genesis ledger has a sequence number of 1. The ledger directly following a ledger with sequence number `N` has a sequence number of `N+1`.
+Ledger `N+1` contains a hash of ledger `N` in its previous ledger field.
 
 ## Ledger header fields
 
@@ -83,4 +115,4 @@ The reserve the network uses when calculating an account’s minimum balance.
 
 ### Skip list
 
-Hashes of ledgers in the past. Allows you to jump back in time in the ledger chain without walking back ledger by ledger. There are four ledger hashes stored in the skip list. Each slot contains the oldest ledger that is mod of either 50 5000 50000 or 500000 depending on index skipList[0] mod(50), skipList[1] mod(5000), etc.
+Hashes of ledgers in the past. Intended to accelerate access to past ledgers without walking back ledger by ledger. Currently unused.