Bitcoin Forum

are they, or their hashes, usable in bitcoin blockchain,

is that danger to bitcoin blockchain in any way ?

can euro's appear in a dollar bank account? .. no

but people are free to earn bitcoin or alt coins and free to spend each as they like.

bitcoin blockchain (the protocol) wont break, thy are totally separate things, just with similiar features or different features depending on which coin you choose. so dont worry about bitcoin.

i would be more concerned about wasting has power on an altcoin that ends up giving you worthless coins (pump 'n' dump alts)

The idea is that you mine the altcoins and then trade for BTC, immediately.  At least that's what my pool does.

Sure, one could hold onto some altcoins and see if their value increases, but the method I mentioned is what is more commonly done, as I understand it.  That way, there is no worry about "pump n dump" because you already dumped it. 

I know some people think that is "wrong" but it is how a currency exchange or market works, imho.

I am talking about actual numbers that are a block hash,

can they be reused, that hash, to mess with with bitcoin blockchain ?

for eample,
some altcoin miner finds new block and that 000000000000000023494920420402 hash actually fits the current bitcoin blockchain requirement, and uses it to "hurt" bitcoin in some way

I hope I now clarified my question

No. Blocks found on a different chain won't validate and won't be accepted on bitcoin's blockchain.

If it was that easy to mess with Bitcoin, non of us would be using it in the first place.

Hashes are computed using the block header as input. Elements of the block header depend on many things, including the transactions included in the block. In the block header there is some free space that can be filled with any value (the so-called nonce). The goal of the miner is to create a block header in such a way that its hash falls below a certain target value. So while the hash of a blockheader of an altcoin may fall below the target of the bitcoin blockchain, the block that this hash was computed from will not be a valid Bitcoin block, because the difficulty value embedded in its header will be different and the transactions included in the block will be invalid on the Bitcoin network.

ok, now it is much clearer

hash is proof of work, but cant be submitted as the actual work,
work is the block produced,
altcoin miner must be actually mining bitcoin to be able to use finding on bitcoin

No, but maybe some features of alts could eventually be implemented into Bitcoin if they were of value.

No there are no "danger" for bitcoin blockchain, it's not connected in anyway as far as I know.

if some features of alts could  be implemented into Bitcoin it would be a very good addition. Don't you think so?

Good features from altcoins can be implemented in bitcoin.
But that's entirely unrelated to their respective blockchains and doesn't cause any interaction between the 2.

If altcoin X implements something cool, bitcoin devs can just take the code and add it to bitcoin.
Then when everyone upgrades to the new bitcoin version, they have 'something cool' too.

There many altcoins that use the same method for generating public addresses as other alt coins and bitcoin. For example, Teracoin and Bitcoin addresses are 100% compatible. There have been several cases of people sending bitcoins to an address in a Teracoin wallet at BTC-e. They were actually sending to a Bitcoin address because the two systems are completely separate, but you can imagine the confusion it caused.