Polling booths opened on Thursday in Scotland's historic referendum on independence, with record numbers of Scots expected to cast their vote on whether to stay or leave the United Kingdom. Voting will continue until 2100 GMT and the result, which opinion polls have suggested is too close to call, is likely to emerge in the early hours of Friday. Scottish residents are being asked one question on the ballot paper -- "Should Scotland be an independent country?" -- and will mark either "Yes" or "No". A record turnout of around 80 percent is expected after an electrifying campaign caused 97 percent of people eligible to vote to register -- almost 4.3 million people. At a polling station in Edinburgh West, one of 2,600 places where votes will be cast across the country, people arrived almost as soon as the booths opened at 0600 GMT. Presiding officer Peter Macvean said: "It's a very special day, one in a lifetime."