No More Leap Second? 295
WerewulfX writes "CNN reports: "In a phenomenon that has scientists puzzled, the Earth is right on schedule for a fifth straight year." Update yeah, this is a repost. Whatever- it's a holiday. Nothing else to post :)
Re:LAME DUPES, EVEN WHEN TOLD IT WAS SO! (Score:1, Informative)
What the hell is this crap? Redundant???
This isn't a normal "I was too lazy to properly check for dupes" situation.
No.
This is a situation where someone, who is supposed to be ON DUTY and who are supposed to READ their emails about potential problems with the story they just posted, neglecting their duty.
Honestly, the story is posted. They only have to pay attention for a total of 15 minutes until it goes live. Whomever it was, didn't.
I'm quite willing to bet that I wasn't the only person that pre-emptively emailed about this being a dupe either.
HELLO? What is the problem? I doubt I'll donate to Slashdot again!
Re:Can someone please explain to me... (Score:3, Informative)
Re:sun has changed? (Score:2, Informative)
> isn't constant over time,
> try to explain this?
I am a PhD student in mathematical physics, but I'm afraid I don't have a complete answer for you.
Technically the Sun's mass is decreasing due to solar wind, neutrinos and light (light doesn't have rest mass, but it still carries away energy). However, the change caused by this is so minuscule you can neglect it for the purpose of Earth's orbit. The difference will not be measurable.
A change in the mass of the Earth-moon system should not have an measurable effect on the period of the orbit either (as long as it remains small compared to that of the Sun).
General Relativity predicts a decrease in the orbital period, but it's so tiny that the only planet for which this is even measurable is Mercury (because its so close to the Sun). So I assure you that this is not it either.
In conclusion, I don't know why Earth's year had been decreasing, anymore than those scientists know why it stopped. This is not something that is predicted by any theory that I am familiar with.
I have a friend who specializes in solar system dynamics. Maybe I'll ask her if she has heard about this.
Cheers.
Re:Can someone please explain to me... (Score:2, Informative)
This is all about the earth spinning on its axis, 24 hours/revolution. As others mentioned, you can figure out quite precisely when the earth has made one revolution about its axis, by looking at a star.
The point is, slight variations in the earth's rotational speed on its axis mean that it doesn't take exactly 24 hrs 0 min 0.000 000 sec to turn once.
At the end of the year, they take all the variations and add them up. Usually the yearly variation is a fraction of a second, resulting in a possible leap-second. BUT (this news item informs us) the recent variations haven't been big enough to require a leap-second.
The Earth is just a big top spinning on its axis, a mechanical object. An analog object. No wonder its rotational speed varies! It isn't digital!
Re:Can someone please explain to me... (Score:3, Informative)
tm_sec: The number of seconds after the minute, normally in the range 0 to 59, but can be up to 61 to allow for leap seconds.
So it would seem Linux, at least, has provisions for leap seconds. I think the same thing happens on UNIX as well, but I'm not somewhere where I can verify that right now.
As noone got it right in the earlier article (Score:5, Informative)
Particularly, the monsoon season I believe has the largest effect, particularly because the generated winds impact the himalayan mountains.
The combination of a large (albeit distributed) force impacting a large object (himalayas) affects the angular velocity of the earth.
I learned this first because a friend was writing an ephermeris program and got in contact with the guy an NIST who tracks these things. I beleive they can make some predictions of change in rotational velocity based on the force of observed storms.
Also the Navy has built an array of (radio or laser, I forget) interferrometers located in (I believe) the rocky mountains which are used to measure the actual variances against star positions.