Comments on: FOLLOWUP: Leap seconds

By: 2008 teve um dia e um segundo a mais! Chega! « Comentários, Críticas, Dicas etc.

Mon, 05 Jan 2009 00:26:35 +0000

[...] Bad Astronmer FOLLOWUP [...]

By: Gary Ansorge

Gary Ansorge — Fri, 02 Jan 2009 17:08:53 +0000

Robert Gift: It’s actually a bit more complicated than that,,,ever bit of meteor that falls to earth has to impact the planet with some velocity and, depending on whether it impacts from a trailing direction(ie, coming up on the planet from behind, impacting against or with the planets rotation) or from head on(with the same caveats) they will impart their mass energy to our angular velocity. On average, it all cancels out. Besides, it took over 4 billion years and the ejection of a large mass into orbit(the moon) to slow our planetary rotation from a six hour day to the current 24. I expect life will be long gone due to solar expansion before the earths rotation stops. Too far in the future for even ME to worry about,,,

Gary 7

By: Jack Hagerty

Jack Hagerty — Fri, 02 Jan 2009 08:31:37 +0000

So why doesn’t the international standards committee that makes up the rules just redefine the length of day in atomic clock terms? Move the 1900 standard to 2000? That’s what astronomers did when shifting from the 1950 ephemeris to the 2000.

- Jack

PS – I belive “second” when refering to the unit of time is short for “second minute,” since it breaks the minute into the same number of pieces that a minute breaks an hour.

By: Mojo

Mojo — Fri, 02 Jan 2009 00:44:31 +0000

Phil, you said, “In fact, one is added almost every year now.” Why haven’t we had one since 2005?

By: Haxe

Haxe — Thu, 01 Jan 2009 23:41:31 +0000

There seems to be an error in this followup post. It says:

Imagine you have two clocks. One thinks there are 86,400 seconds in a day, the other thinks that there are 86,401, so the second clock runs a tad bit slower than the first.

Actually, the second clock will only count 86401 seconds per day if it runs _faster_ than the first clock, not slower.

Haxe

By: Robert Gift

Robert Gift — Thu, 01 Jan 2009 21:42:56 +0000

MASS from METEORS and SPACE DUST
is slowing the earth.
So if we launch more rockets to rid ourselves of some of the mass, and launch them in an easterly direction, we will speed up the earth.

Problem solved!

By: IBY

IBY — Thu, 01 Jan 2009 21:08:57 +0000

I wonder in what year will the Earth’s rotation be tidally locked with the moon’s. ^_^

By: quasidog

quasidog — Thu, 01 Jan 2009 20:47:05 +0000

Trebuchet .. I was getting that also and thought “oh no” .. but ti seems to have righted itself now.

By: George E Martin

George E Martin — Thu, 01 Jan 2009 20:08:33 +0000

It should be noted that there is an active proposal to abolish the leap second. The International Telecommunications Union currently has a vote scheduled in 2009 on this.

http://www.newscientist.com/article/mg20026875.400-calls-to-scrap-the-leap-second-grow.html

George

By: Trebuchet

Trebuchet — Thu, 01 Jan 2009 15:38:42 +0000

A little off-topic, but how come this post, and all the previous ones on the page, but not the New Years one, are showing up in a tiny Italic font? My eyes are too old for this!

No Italics on the comments page, however.

By: quasidog

quasidog — Thu, 01 Jan 2009 10:28:09 +0000

.. actually I am making a huge assumption about it the Earth decreasing at an exponential rate in a similar way to a spinning top. It is probably completely different right ?

By: quasidog

quasidog — Thu, 01 Jan 2009 10:24:26 +0000

Thanks Tobojorn … yeah in hindsight I knew it wobbled .. although I didn’t actually think about that when I posted my question, but you say the effect will be increased .. ok cool.

I just imagine a top spinning, and I can see it wobbling even when spinning fast, much like Earth does now over long periods of time. I wondered, as is decreases at an exponential rate, if the wobble would become more chaotic, like the spinning top does.

Thinking about it now I guess the top is being effected by a downward force of gravity from the earth. The Earth on its own and being gravitationally effected by the Sun would be a lot different with its dynamics. I’d love to know if scientists have worked out at what point in the slowdown it would become overwhelmingly noticeable, to the point it would it would endanger life on Earth…. and also with regards to my second question … if this would happen before the Red Giant phase of the Sun in a few billion years time.

Thanks for your answer.

By: Torbjörn Larsson, OM

Torbjörn Larsson, OM — Thu, 01 Jan 2009 05:38:45 +0000

Will the Earth slow to such a point that its centrifugal force (if that is correct) will become so weak that it wobbles uncontrollably

Um, AFAIU Earth wobbles uncontrollably all the time as all planets do. Earth isn’t a perfect sphere, and its mass redistributes over seasons. The AGW should increase the effect.

By: Kaleberg

Kaleberg — Thu, 01 Jan 2009 05:30:38 +0000

This could also be a problem for Star Trek fan fiction writers who want to work a solar eclipse into some exciting tale of Star Fleet action on earth.

By: Kaleberg

Kaleberg — Thu, 01 Jan 2009 05:29:37 +0000

Does this make things hard for astronomers? If I remember my sunrise/sunset algorithms correctly astronomers use the so called Julian calendar which has a year zero for ease of computation. This means I can calculate sunrise, let us say, for some latitude and longitude for a particular day in the year AD 2100, but how do I convert that Julian date and time into GMT if I can’t know how many leap seconds there will be between 2009 and 2100? I could be off by the better part of a minute. Is this a real problem or evidence of a misunderstanding.

By: JoeSmithCA

JoeSmithCA — Thu, 01 Jan 2009 05:19:47 +0000

Phil;

I thought the article was fine. I got it and if there was anything up for conjecture I just comb through the comments and do a little research on my own

Happy New Year to you, your technical editing staff (otherwise known as the people who comment here like Ivan3Man et all) and everyone else who reads your blog

By: Crudely Wrott

Crudely Wrott — Thu, 01 Jan 2009 03:15:01 +0000

“Does anybody really know what time it is?
Does anybody really know?”

Chicago, the band, some while back, if I recall.

Apparently, there’s more than one way to keep time, depending on custom and need.

Actually, there’s more than one way to make time, depending on custom and need.

The two (or the many) are probably congruent, sometime. Probably not lately, though.

No wonder we wish each other Happy New Year! at this time of year. Roughly this time of year. In the middle of winter just as the days begin to grow longer. Somewhen just about now. Oohh, you know when I mean. [grin]

By: Steve Allen

Steve Allen — Thu, 01 Jan 2009 02:51:21 +0000

The history is complex. The ephemeris second was defined as a given fraction of the length of year in 1900 as defined in Newcomb’s tables. Newcomb’s tables were based on observations centered roughly on year 1820, and that defines the length of an ephemeris day. The atomic second was chosen to match the ephemeris second.

By: Phil Plait

Phil Plait — Thu, 01 Jan 2009 02:41:57 +0000

Steve Allen, it’s more complicated than that. The day length was standardized to 1900, then the atomic clocks were set to a different standard. The actual history is a mess.

By: Steve Allen

Steve Allen — Thu, 01 Jan 2009 02:19:32 +0000

The length of the atomic second was chosen such that it matched the length of the mean solar day around 1820, not 1900. See the web page for more details.

By: quasidog

quasidog — Thu, 01 Jan 2009 02:15:39 +0000

wb4 … while I am not scientifically sure about that .. at a guess I would say, No. I am pretty sure this is happening over a much larger period of time than within our own lifetimes to allow 2 seconds to be adjusted. Someone correct me if I am wrong, but I am pretty certain about that.

By: quasidog

quasidog — Thu, 01 Jan 2009 02:10:14 +0000

Here is a question. Will the Earth slow to such a point that its centrifugal force (if that is correct) will become so weak that it wobbles uncontrollably, like when a spinning top slows down, and it begins to wobble out of control?

Also, if it does slow down to such a degree, will this happen before the Sun begins to expand into a red giant, in say 5 billion years or so ? Which will happen first ?

By: Charles

Charles — Thu, 01 Jan 2009 01:53:55 +0000

Was all this, perhaps, managed on a Zune?

By: Oliver

Oliver — Thu, 01 Jan 2009 01:52:07 +0000

“a second from the second clock”

OH English. How about a second from “the latter”?

By: Julie

Julie — Thu, 01 Jan 2009 01:30:18 +0000

To 99.9999% of the population whats 1 second between friends. Give an extra hug to a friend, have another gulp of the New Year Spirit or what ever floats your festive boat!! At the end of our time we’ll all live as long as we’re supposed to, so just go for it, and enjoy!!!! Happy 2009(plus 1second) to all!!