Why is Block Gas Limit set to 5000?

Question

If you look at the Parity chain spec for mainnet (https://github.com/paritytech/parity/blob/master/ethcore/res/ethereum/foundation.json), you will see this line:

"gasLimit": "0x1388",

But that should mean that the gas limit is 5000? And that's really strange!

Someone is going to say "That is only for the genesis block" and then I will ask them to please answer this question:

Setting Block Gas Limit in private blockchain?

Someone else may say "you can change it to any value you want" but that is not the point.

This is also related:

Parity genesis file - How to set "minimal cost of the transaction" a.k.a. "Gtransaction" value?

Thank you.

Answer 1

This represents the current Ethereum main chain, and the initial gas limit for that chain was indeed 5000, which was too low to send any transactions. This was part of a deliberate process called "thawing", where the gas limit started out very low, and was gradually increased over time as people became more confident that the network was functioning correctly.

See more about thawing here: https://blog.ethereum.org/2015/07/22/frontier-is-coming-what-to-expect-and-how-to-prepare/

Obviously this value would not be appropriate for a private chain.