Whatever the Scottish people decide in the independence referendum, come Friday a few fundamentals will remain.
On a clear day you'll still be able to glimpse Scotland in the distance from vantage points on the County Antrim coast.
Celtic and Rangers fans across Northern Ireland will still follow their teams with fervour.
Ulster Scots folk will still feel a special bond with their kith and kin across the water.
Many of us will still board ferries in Belfast and Larne on the way to visit our family and friends in Glasgow and Edinburgh.
If it's a no vote, the debate about extra powers for Scotland will have clear implications.
Stormont's demand for the devolution of corporation tax is the most obvious point at issue, with senior Westminster sources indicating that, after previous refusals, they are now more likely to say yes.
Whether Stormont's inability to balance its books due to disagreements over welfare reform will have an impact on the corporation tax debate isn't clear. It could be tempting for the Treasury to link the two issues, but so far there's been no public sign that they will.
Full fiscal powers
The devolution of further powers to match any extension of the remit of the Scottish parliament is more contentious.
Sinn Féin wants the transfer of full fiscal powers to Stormont. However unionists are sceptical not only about whether such a move makes financial sense, but also about whether wider devolution would be the thin end of a constitutional wedge.
Also within the context of a no vote, and Holyrood getting "devomax", we can expect Northern Ireland MPs to be dragged into the debate about whether Scottish MPs at Westminster should have their voting rights over English matters curtailed.
Northern Ireland will also be involved in discussions about keeping the Barnett formula, which currently dictates the level of our block grant.
The repercussions of a yes vote are harder to analyse.
There's the obvious psychological blow to unionists who would wake up to find the union isn't the one to which they've pledged loyalty.
Would the union flag remain red, white and blue, as suggested in the Scottish government's white paper? Or would loyalists have to get used to waving a different flag?
I'm not convinced England and Wales would make any immediate move to cut the multi-billion pound subsidy enjoyed by Northern Ireland, that has been suggested elsewhere.
If there's a yes vote in Scotland, Westminster politicians are likely to concentrate on the complex negotiations under way with Edinburgh, rather than provoke a fresh crisis at Stormont.
However, you only have to glance at the map of the two hypothetically divided islands to wonder what the long-term English view would be about maintaining a costly financial link with a place off the coast of an independent Scotland.
No doubt a yes vote would embolden Sinn Féin in its call for a fresh border poll, this time including 16-year-olds.
There's no sign from recent opinion polls that republicans would get the result they want, but under the terms of the Good Friday Agreement they could scratch a "seven year itch" with nationalists seeking to test opinion regularly as the demographics slowly change.
The campaign in Scotland could trigger a series of questions about exactly how a border poll might be arranged.
Is there a need for a matching referendum south of the border? Should that take place at the same time or after a northern poll? Would there be, as in Scotland, a "Yes" and a "No" campaign?
Or, as in 1973, should voters be required to pick option 1 or option 2? Should there be any other options on the ballot paper?
Either way, Friday 19 September promises to be a highly significant date not just for Scotland but for Northern Ireland.
Will it be "Good Friday" or a "19th nervous breakdown"?
That depends whether you happen to be a nationalist or a unionist living on either side of the Irish Sea.
Political editor, Northern Ireland