Scots begin casting votes in few hours on independence referendum

EDINBURGH, Scotland (CNN) -- Voters in Scotland head to the polls at 6 a.m. Thursday (11 p.m. Wednesday Seattle time) to cast their ballots on independence from the United Kingdom -- England, Wales and Northern Ireland.

Opinion polls put the two sides neck-and-neck ahead of the historic referendum.

The latest poll of polls, released Wednesday by ScotCen, an independent research center, shows "no" at 51% and "yes" at 49%, with "don't know" voters excluded. It is consistent with results over the past week or so, which have indicated the race is too close to call.

Polls suggest around 8% of voters remain undecided, making their votes crucial to deciding the outcome of the referendum.

As the vote nears, emotions are running high on both sides, dividing families and polarizing communities.

The leader of the pro-independence campaign, Scottish First Minister Alex Salmond, will tell "Yes Scotland" campaigners in Perth on Wednesday evening that they have run the "greatest campaign in Scottish history," according to an advance copy of his speech.

"We meet tonight on the eve of the most exciting day in Scottish democracy. We do so to catch our breath for the day ahead -- a day which Scotland will never forget," he will say.

"Tomorrow is the opportunity of a lifetime. A precious chance to leave our mark in the pages of history."

Gordon Brown: This is everyone's country

But former British Prime Minister Gordon Brown, himself a Scot, called on his fellow countrymen and women Wednesday to vote "no" to independence with confidence.

Speaking in Glasgow, he said, "This is everyone's flag, everyone's country, everyone's culture, everyone's street and let us tell the people of Scotland that we who vote 'no' love our Scotland and love our country."

Scotland's many past and present achievements, Brown said, "happen not outside the union but inside the union. They happen not in spite of the union but because of the union."

The issue of spending on social welfare and health care, through the National Health Service, has been central to campaigning. Questions over the economy, North Sea oil reserves and taxation have also been key.

Each side has argued that it is the best equipped to create more jobs for Scotland.

Many questions remain unanswered about what will happen if Scotland votes to go it alone, including its future membership in the European Union and NATO and over the United Kingdom's future defense capabilities.

In an open letter published in UK tabloid The Sun on Wednesday, 14 former UK defense chiefs warned against breaking up the union.

"At risk is the most successful alliance in history and one which has seen men and women from all parts of the country play their part in securing the liberties we now enjoy," they wrote.

"The division of the UK may or may not be politically or economically sensible, but in military terms we are clear: it will weaken us all."

The Scottish National Party has said it wants to remove the UK nuclear submarine fleet from Scottish waters as soon as possible.

More than 4.2 million people have registered to vote, the largest electorate ever in Scotland.

Any registered voter aged 16 or over who is a resident in Scotland is entitled to cast a ballot. Voters do not have to be British citizens; Commonwealth, Irish and EU citizens who live in Scotland and are registered to vote there can do so.

They will be asked the yes/no question: Should Scotland be an independent country?

If Scotland decides to leave the United Kingdom, it leaves behind England, Wales and Northern Ireland.