another problem to fix, earth slowing!

[stubeeef]

I think they are talking the rotation, not orbit.

Here some more fun.

The Earth’s rotation speed can be measured using different techniques. One of the oldest ways is with multiple radio telescopes all observing the same very distant object. The telescope signals can be combined to give a precise position of the Earth.

More recently, global positioning satellites (GPS) and laser ranging (bouncing a laser beam off of the Moon or a satellite) can also determine the speed with which our planet spins on its axis.

Make that Leap
When changes in the length of the day accumulate, it becomes necessary to add a leap second. The organization responsible for keeping track of this is the International Earth Rotation Service (IERS). Since 1972, the IERS has added 22 leap seconds. The last leap second was on Dec. 31, 1998. Learn More

The rotation data shows oscillations over several different timescales. The one with the largest variation is seasonal: Earth slows down in January and February.

"It turns out that during the Northern Hemisphere winter, the winds – which are predominantly west to east – are stronger," Salstein said.

The more forceful winds double the angular momentum of the atmosphere. Angular momentum is a conserved quantity in nature – the example usually given is the spinning ice skater conserving angular momentum by speeding up when she brings her arms in.

In this case, the whole system – comprised of the spinning Earth and swirling atmosphere – adjusts to the blustery winter months by slowing down the solid Earth’s rotation. This means the days get longer – by a few thousandths of a second.

The winter in the Southern Hemisphere does not produce the same increase in wind because the bottom of the world is mostly ocean and the temperature swings are, therefore, not as great.

Lots more here
Link

Why it matters

Because the dominant relationship in Salstein’s observations is between wind and rotation, he attempts to predict the Earth’s rotation from long-range weather forecasts.

This rotation forecast is important to NASA’s Jet Propulsion Laboratory because they need an exact reference to send out navigation signals to their spacecraft in the far reaches of the solar system. Although a millisecond difference in the length of the day seems like a small change, "at the radius of Jupiter that will be important," Salstein said.

It may not be so simple to say if weather is causing changes in the rotation, as Salstein presupposes, or if rotation drives shifts in climate, as Sidorenkov claims. Although weather might seem to be immune to millisecond changes in the Earth’s rotation, it should be remembered that the Earth’s rotation does play an important part in creating general weather patterns.

For instance, the motion of the jet stream and the counterclockwise-moving winds around low-pressure systems in the Northern Hemisphere (opposite in the Southern) are manifestations of the Earth turning underneath the atmosphere.

It may be that rotation and weather are so intricately tied that it may not make sense to speak of cause and effect. The Earth slowing down may drive a change in wind patterns, which causes another alteration to the rotation, which then kicks up more wind, ad infinitum.

 

[feakbeak]

Eh? I thought pounds were a unit of mass, as well as force. Guess I wasted 3 years at uni. I do like the idea of slugs though - I weigh 6 slugs hmmm have I just lost weight?
We were always taught that kgs were a horrible French invention - now we just remind them of the Olympics, and the celebration in Trafalgar Square

Thanks for the link to the Wikipedia entry - it was interesting. I had always been taught it was a measure of force but not mass. It looks like officially it is a unit of both mass and force but that many physicists don't recognize it as a unit of mass - which is primarily where I obtained that idea as I've taken several physics courses in high school and college.

Although the U.S. National Bureau of Standards has defined the pound as a unit of mass, and the pound-force as a unit of force, this distinction is not widely recognized among working physicists, because the fps system has not been used in physics, even in the U.S., since the early 20th century. When giving data to be used in calculations, it is not a good idea to use the term pound without clarifying whether mass or force is intended. If force is what is meant, the symbol "lbf" or the term "pounds-force" can be used for clarification. For mass, one can specify "pounds-mass."

Oh well, slugs sound more interesting anyway.

 

[witness]

god that movie sucked

I like that film, I even have a copy on DVD. OK it's low budget and the acting isn't great, but I still like it.

 

[aloofman]

Perhaps I'm not understanding...but why add a second? Is the Earth's rotation on its axis slowing, or is its rotation around the sun slowing? If it's the rotation on its axis (thus creating the extra second of daylight mentioned by previous posts), won't adding a second screw up our calculation of the year?

For the same reason that we add an extra day to February in leap years: because the actual duration of a year is not exactly 365 days. It's easier to add a day every four years (usually) than it is to tack on a one quarter-day to the end of the year that would screw up the length of the day.

In this case, we add or subtract a second here and there so that our artificial units of time conform to the actual, astronomical length of the day. Before the modern era -- and for most practical purposes, even today -- this tiny change was not that relevant. But for the various scientific reasons listed above, it matters in the long term.

The funny thing is that most clocks will lose their accuracy over a much shorter period anyway, so people usually have to reset clocks regularly before they would even have to worry about correcting for the added second. As a news story it's really just a public curiosity.

 

[~Shard~]

Although we seem rather clueless about how gravity actually works the equation to calculate the gravitational force between objects works rather well.

The only problem is accurately determining the gravitational constant, G. I find it interesting that more recent attempts to measure G have brought the accuracy of its value into further doubt. Gravity certainly does seem to be an enigma.

Yes, very true, but one also needs to keep in mind that the formula is just that - a formula, a model, of how we perceive things to work, just as physics is on the whole. Yes, is is a damn good model, (Newton's laws rarely seem to fail me ) but a model nonetheless of how we have attempted to understand how the universe works. We can apply theories and models to concepts such as gravity, yet the way the universe actually works is another matter.

As you say, gravity is definitely an enigma - just as dark matter, magnetism and many other phenomenon.

 

[ja0912]

I take this to mean that each day (rotation) has been .00274 .... seconds longer than it should be, so it was corrected at the end of the year.

I'm probably wrong too.

 

[Doctor Q]

Am I remember correctly that the plot of the movie Entrapment involved a leap second, when they were robbing the bank in the Petronas Towers in Malaysia? Making millions of dollars in one second is a nice pay rate and a good way to spend the extra second on New Year's Eve.

A more important question: If triplets were born rapidly as a leap second passed, one at 11:59:59, one at 11:59:60, and one at 12:00:00, for how many of them would the parents be eligible to take a dependent tax deduction for the year ending?

 

[CanadaRAM]

But nobody's talked about HOW we're going to fix the problem.

Here's how: First we get everybody to line up, facing West.
Then all at the same time, everyone jumps westward really, really hard.

That ought to spin the old girl a bit faster.



Oops, this won't work. It's a closed system, whatever we gain when we jump, we lose when we land, with an equal and opposite acceleration. Dang.

OK, so to make this work, you've got to jump hard enough to attain escape velocity. Right then... First we get everybody we DON'T LIKE to line up....

 

[~Shard~]

A more important question: If triplets were born rapidly as a leap second passed, one at 11:59:59, one at 11:59:60, and one at 12:00:00, for how many of them would the parents be eligible to take a dependent tax deduction for the year ending?

Wow, only you would come up with a scenario like this Doctor Q - most impressive.

Let's phone the tax agency and ask. I'm sure they have a form for it...

 

[feakbeak]

Yes, very true, but one also needs to keep in mind that the formula is just that - a formula, a model, of how we perceive things to work, just as physics is on the whole. Yes, is is a damn good model, (Newton's laws rarely seem to fail me ) but a model nonetheless of how we have attempted to understand how the universe works. We can apply theories and models to concepts such as gravity, yet the way the universe actually works is another matter.

Yes, it is rather amazing how we try to understand and explain the workings of the universe. I'm a big math geek and I've always found it interesting how most mathematics has been derived from trying to understand and accurately describe natural events, such as how calculus was needed to help explain the orbits of the planets. That discovery allowed us to throw out the perfect sphere theory of how the planets moved, to be replaced with Keepler's laws, a much simpler explanation.

The amazing thing to me is how in some cases this trend is starting to reverse. As an example, a few years back the importance of group theory was emphasized when some physicists, using group theory, predicted the existence of a particle that had never been observed before, and described the properties it should have. Later experiments proved that this particle really exists and has those properties. The development of pure mathematics is now allowing humanity to understand some of the inner workings of nature before we even observe it which is historically how we've learned about the world around us. Theoretical science and pure mathematics are quite fascinating and I miss college since it provided regular exposure to these topics. Although programming for a living is not such a bad gig eitehr, but certainly not as engrossing, IMO.

Sorry for being off topic, hopefully a few of you (Shard, DoctorQ?) might enjoy my tangent.

 

[Abstract]

THE YEAR OF HQ VIDEO HAS JUST BEEN EXTENDED BY AN ENTIRE SECOND!!!

O <3 Steve!

LOL!!one1!!1!

Too bad the year of the laptop lasted as long as it did.

 

[thedude110]

I really hate summer. I hate leaves, I hate warmth, I hate light.

But this whole "earth is slowing" thing puts it in context. My real problem isn't with summer, it's with the earth.

God. All you have to do is spin, stay tilted and stay in orbit. And you tell me you're SLOWING? And my co-workers think I'm lazy ...

 

[stevietheb]

For the same reason that we add an extra day to February in leap years: because the actual duration of a year is not exactly 365 days. It's easier to add a day every four years (usually) than it is to tack on a one quarter-day to the end of the year that would screw up the length of the day.

In this case, we add or subtract a second here and there so that our artificial units of time conform to the actual, astronomical length of the day. Before the modern era -- and for most practical purposes, even today -- this tiny change was not that relevant. But for the various scientific reasons listed above, it matters in the long term.

Yes, what I trying to get at was that adding a second in order to correct the length of the day due to the loss of rotational speed will only disrupt our calculation of the year...especially in this, a leap year--when we're actually on schedule.

 

[TrenchMouth]

Know what is odd about this? Again, as someone pointed out earlier, this doesnt have to do with the rotation, but rather the orbit.

However, recently it has been determined that the Earth is actually speeding up and for unknown reasons.

its true

so that extra second? well, at the time i was reading it i was traveling at a good speed, i think i have already consumed my extra alloted time.

 

[~Shard~]

<snip>

Sorry for being off topic, hopefully a few of you (Shard, DoctorQ?) might enjoy my tangent.

Absolutely, no need to apologize. I love discussing theoretical physics, the "real" universe, topics such as quantum mechanics/physics, the whole thing! I've always been meaning to start a separate thread on the topic, maybe I'll get around to it one of these days - when I do, I'll let you know. I've got some pretty crazy ideas of my own...

But for now, we probably should stay a little more on topic, although I don't really see this as straying too much...

 

[Flying Llama]

YAY! ONE WHOLE SECOND!!! THIS WILL CHANGE MY LIFE OMG!!11!el11even!!one

llama

 

[stubeeef]

But nobody's talked about HOW we're going to fix the problem.

Here's how: First we get everybody to line up, facing West.
Then all at the same time, everyone jumps westward really, really hard.

That ought to spin the old girl a bit faster.



Oops, this won't work. It's a closed system, whatever we gain when we jump, we lose when we land, with an equal and opposite acceleration. Dang.

OK, so to make this work, you've got to jump hard enough to attain escape velocity. Right then... First we get everybody we DON'T LIKE to line up....

OK, how about this, first we build a really large badger...........

 

[question fear]

Ugh. That movie was full of science fallacies. Yeah, you can really talk to someone who is thousands of miles underground using radio...

Is that where it lost you? When I saw it, my roommate and I loudly proclaimed plot holes starting with the shuttle that stopped directly in front of the guy in LA....and then there's the pacemaker people.....and the indestructible metal....and the NUKES THAT ARE LAUNCHED AT THE CORE OF THE EARTH.....

:-D

 

[MongoTheGeek]

With hours minutes and seconds being precisely defined mathematically and days being dependent on astronomical events which are less than precise there is a need to add in or take off a second. They do this at midnight on new years with the theory of "Hey, lets screw everything up at once."

On average over the eons the earth has slowed down. The inner core of the planet rotates every 18 hours (as determined by seismologist.) The slowing down is likely due to the presence of the moon and tidal attractions. Eventually the earth will slow and have one side always facing the moon. (don't hold your breath)

The effect of the spin causes the earth to be slightly oblate (squished) so that its further around the equator than around the poles. The number is like 2% so you wouldn't really notice it.

The earth can speed up. When water is moved north and south from the equator (trapped in ice caps or behind dams) then conservation of momentum says that the earth must speed up. (Mo = 3D intgreal of rho*r*(d theta/d t)) If r decreases and rho remains constant then the speed must increase. Think ice skater doing spins. I saw numbers once saying that the 3 gorges dam would shorten the day by a millisecond.

As for the effects of the slow down, I wouldn't worry. There is so much variation from things like Ice Ages and continental drift that the slow down is lost in the noise. The earth will be swallowed by the sun before the day even doubles (assuming my math is right) This is something that operates on the scale of hundreds of millions of years. (I'm thinking 1 hour every 300,000,000 years)

 

[aloofman]

Yes, what I trying to get at was that adding a second in order to correct the length of the day due to the loss of rotational speed will only disrupt our calculation of the year...especially in this, a leap year--when we're actually on schedule.

2005 isn't a leap year.

 

[~Shard~]

2005 isn't a leap year.

Correct - the next leap year will not occur until 2008.

 

[Nickygoat]

The effect of the spin causes the earth to be slightly oblate (squished) so that its further around the equator than around the poles. The number is like 2% so you wouldn't really notice it.

The Earth is an oblate spheroid already

The Earth's shape is that of an oblate ellipsoid, with an average diameter of approximately 12,742 km. The maximum deviations from this are the highest point on Earth (the summit of Mount Everest, which is only 8,850 m) and the lowest (the bottom of the Mariana Trench, at 10,911 m below sea level). Thus the Earth is an oblate ellipsoid within a tolerance of one part in about 584, or 0.17 %. The mass of the Earth is approximately 6,000 yottagrams (6 x 1024 kg).

From Wiki. And you would notice a 2% variation.
At last - I've found a use for my Geology course

 

[MongoTheGeek]

The Earth is an oblate spheroid already

From Wiki. And you would notice a 2% variation.
At last - I've found a use for my Geology course

Off by an order of magnitude. Darn.

I really don't think that a 2% difference would really be noticeable except maybe from space.

More stuff to learn