What is a 51% attack in layman’s terms

A 51% attack or double-spend attack is a miner or group of miners on a blockchain trying to spend their crypto's on that blockchain twice. ... The goal of this isn't always to double spend crypto's, but more often to cast discredit over a certain crypto or blockchain by affecting its integrity.

In such a scenario, the attacker would have enough mining power to intentionally exclude or modify the ordering of transactions. They could also reverse transactions they made while being in control, leading to a double spend problem

Here is a brief example: let’s say I spend 10 Bitcoin on a boat. The boat gets delivered a few days later, and my Bitcoins are transferred from me to the boat company. By performing a 51% attack on the Bitcoin blockchain, I can now try to reverse this Bitcoin transfer. If I succeed, I will possess both the luxurious boat and my Bitcoins, allowing me to spend those Bitcoins again.

You can reverse a transaction by essentially rendering it obsolete. This entails creating a new chain that doesn’t include the previously recorded transaction you’d like to “reverse.” In doing this, you can end up “spending” the same coins twice.

Can a 51% attack be prevented?

The main thing that helps prevent a 51% attack is the decentralization of miners. As long as no single entity has control of over 50% of the mining power, the network is safe.

Could Bitcoin itself suffer a 51% attack?

To successfully conduct a 51 percent attack on the Bitcoin network would cost an incredible $1.4 billion and consume as Much Electricity as Morocco uses