EARTH'S SPIN SLOWS DOWN, NASA SAYS.

Byline: David R. Baker Daily News Staff Writer

For those of you who feel El Nino has hung around too long, it's actually been longer than you think.

The weather-altering phenomenon actually slowed down the Earth's rotation and made days grow longer, according to researchers at NASA's Goddard Space Flight Center in Maryland.

Not that you'd notice. The change never amounted to more than .6 milliseconds (6/10,000 of a second) per day.

``When you fire a .22-caliber rifle, the bullet gets about halfway down the barrel in .6 milliseconds, so we are talking about an extremely short period of time,'' said John Gipson at Goddard.

During this entire El Nino episode, which started last summer, the world has gained an extra 10th of a second.

Granted, as feared and reviled as El Nino has become, crediting it with longer days may seem a stretch. El Nino is a complex phenomenon - fueled by unusually warm water in the eastern equatorial Pacific - that causes droughts in some parts of the globe and flooding in others.

The explanation of its effect on the length of days lies in the spin of the Earth and its atmosphere.

Both were spinning in space when they formed, and the rotational energy they carry remains fixed. In other words, if part of the earth-atmosphere system speeds up, another part will slow down to compensate, Gipson said.

During an El Nino episode, the atmosphere, charged with energy from the warming ocean, speeds up. The earth slows down, and the days grow a little bit longer.

Then when El Nino dissipates, the earth speeds up again.

``So over the long term, these things just balance each other out,'' said Bill Patzert, at NASA's Jet Propulsion Laboratory in Pasadena.

Spotting the change was no easy task. NASA needed a global network of radio telescopes to do it.