Simon English: So the NYSE closed. The world carried on. There's a lesson there

Outlook The boss' demands were blunt and direct, as usual. "When the bell rings I want you standing next to it. Inside it if possible. When that market starts trading again it's the free world saying to the terrorists, you can't beat us, you won't win. I want to feel the excitement."

That was September 2001, when the New York Stock Exchange reopened following some local difficulty (it was in all the papers). Closing Wall Street for four days may not have been Osama bin Laden's greatest hit, but when trading resumed it felt like a big deal.

We cheered. We weren't cowed. We had our freedoms and our stock markets. The idea was that the Dow Jones would soar in a defiant roar. In fact, it slumped in a rare example of genuine panic selling: Freedom 0, Terror 1.

This latest closure of the supposedly premier stock market in the world is much less of a big deal, not just because Hurricane Sandy is not as malicious as Osama.

Indeed, the question is raised of what difference it really made. Facebook got two days' grace – its shares fell yesterday, when the market reopened, rather than on Monday – but that's about the extent of it.

The trading world has moved on so much since 2001 that it is now possible to buy or sell more or less whatever you want from anywhere in the world.

If you had decided on Monday that you just had to buy a bunch of Microsoft, well you could have bought the German listing through Interactive Investor at just £10 per trade.

Other brokers offer Microsoft derivatives, or other proxies for the share. If it really came down to it and you had a wizard idea about an American stock on which you had to bet Right Now, well you could always spread bet. Even if it were an esoteric instrument in which the spread betters weren't offering a market, it wouldn't take long to persuade one of them to come up with one.

So where we are is that the NYSE being shut for a few days is bad for the NYSE, and – at a stretch – a blow to New York's status as the leading centre of finance. Beyond that, well the pictures were newsy.

What are stock markets for, anyway? In theory to raise funds for companies that need to expand and as a price discovery mechanism – the continual ebb and flow of trading is how we find out what's valuable and what's not.

At the moment hardly anyone is able to raise funds from the capital markets, so stymied are they by eurozone panic. And the price discovery element doesn't really apply either.

High-frequency trading algorithms – computers trading at laser speed, trying to turn a cent every thousandth of a second – now account for 70 per cent of completed transactions and 99 per cent of all exchange quotes in New York, say my friends at Charles Stanley.

Those computers are weighted towards positive headlines. They buy on the hint of good news.

Jeremy Batstone-Carr of Charles Stanley says: "A positive market reaction launches an armada of media commentators to the floor of the NYSE and elsewhere eager for affirmative "uppish" commentary, innocent from the knowledge that these market practitioners have virtually zero impact on market action anymore no matter how brightly coloured their jackets, braces... or ties might be.

The trouble is, algorithmic vacuum cleaners just don't do good interviews."

Will the NYSE and the London Stock Exchange still exist in 30 years' time?

It's not presently clear why they should.