[galacticpony]

What does that have to do with anything? You don't understand the point.

You go short on one market, while simultaneously going long on the other market. That's how you profit (arbitrage).

[thehardsphere]

"Going short on one market" = "I can expose myself to losing a sum of money that I don't have if it goes tits up"

[galacticpony]

Not if you simultaneously BUY ON THE OTHER MARKET.

Jesus.

You also can't lose money beyond what you put in (on the exchanges that allow for this), your position just gets terminated.