I know I have seen that it is not exactly 24 hours. Something like 23 hours 59 minutes 56 seconds. Anyone know? I have searched my butt off and I can't find it!
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I know I have seen that it is not exactly 24 hours. Something like 23 hours 59 minutes 56 seconds. Anyone know? I have searched my butt off and I can't find it!
:eek: Yikes...I have no idea....but I can spell the word A N A L.;)
Well, I'm not sure, but I'm pretty certain it's 24 hours.
My reasoning, 24 hours is based on the earths rotation. i.e. 1 rotation = 24 hours, but far more conclusively midday would be time shifting by 4 seconds a day, so after a year Midday would be 24 minutes earlier than the previous year which would cause all sorts of problems if allowed to proliferate.
So maybe it's just 24 hours.
SD
Look up siderial day in google
And if you're an Astronomer or a programmer messing with stuff like that, ya gotta know, AR or not AR. All programmers tend toward AR-ness anyway. One tiny error and you code eats the system, and you like &&&&.
Well, it's not that anal. We need it for a chemistry thing. The real thing has to do with how many significant digits there are.
Ex:
24.0?
24.00?
23.58?
:confused:
Of course this doesn't mean you haven't heard it somewhere before. Me and my mates used to go down the pub and make up 'facts' that we would then tell some gullible local. It's amazing what some people believe if 4 or 5 people tell them that it's true.
We even had my sister in-law believing that that the fjords of Norway were carved by Slartibartfast.
She was arguing with us in the pub about it, and we made her phone my mum and ask her who created the fjords. Quick as a flash mum said Slartibartfast (which is what we had been telling her) and she knew there was no way we could have got a message to her so she believed us.
I wonder if the kids are going to be as gullible :)
SD
I hoped you understood that was just a joke....I'm sorry if I offended anyone. I certainly didn't mean too!:(
no offense taken. :D :DQuote:
Originally posted by barrk
I hoped you understood that was just a joke....I'm sorry if I offended anyone. I certainly didn't mean too!:(
Glad to hear it!:D
http://newton.dep.anl.gov/askasci/ast99/ast99464.htm
Google is awesome. This page doesn't give you the length of a solar day, just the length of a siderial day: 23:56:04.06. I'm sure the length of a solar day is out there.
But yes, we not only have leap years where we add a day, we have leap days were we add two seconds.
http://tycho.usno.navy.mil/leapsec.html
This is a bit technical and dry, but it is from the Naval Observatory, so what do you expect.
Thank you everyone. You may have just saved my friend and I on our lab report! :D :D :D :D :D :D :D
Matthew, a solar day is only off by about 2 milliseconds. A sidereal day will be off by more, but it is not sun to sun, it is fixed star to fixed star.
We add (or subtract) leap seconds to compensate for solar deviations.
Sidereal days aren't supposed to be a long as solar days, so there isn't a problem. And I'll explain why. January 1, and you are standing outside at high noon. The sun is directly over head. In six months time, you are going to be on the other side of that sun as the Earth revolves around the Sun. But at high noon the sun will still be over head on July 1. That is how we define solar days. But on July 1 for you to be facing in the exact same direction that you were facing on January first, you will be at midnight. There is some distant star in the line formed by you and the Sun on January 1 that you will face again on July 1. But when you face it, you are facing away from the Sun.Quote:
from USNO
In order to keep the cumulative difference in UT1-UTC less than 0.9 seconds, a leap second is added to the atomic time to decrease the difference between the two. This leap second can be either positive or negative depending on the Earth's rotation. Since the first leap second in 1972, all leap seconds have been positive and there were 22 leap seconds in the 27 years to January, 1999. This pattern reflects the general slowing trend of the Earth due to tidal braking.
I hope that makes some sense. A sidereal day is the time from you facing that star you faced on January 1 until you face it again on January 2. A sidereal day has to be shorter than a solar day (unless the planet was in retrograde spin, but I won't get into that). In one quarter of a year, you had to loose one quarter of a solar day in sidereal days just so you will keep facing that distant fixed point. In half a year, half a day.
If it still doesn't make sense to anyone, try this...
Put your chair in the middle of the room. Stand on one side of it and look at it, and a point on the far wall. If you spin to your left (assuming your head is the north pole. Aussies can spin to your right) you will simulate days. The chair will be the sun as you see it is day. When it leaves your peripheral vision, it is night.
Now if you walk around the chair while spinning (don't fall) you will simulate a year. If you are northern-hemisphere oriented (spinning to your left) then go around the chair in a counter-clockwise motion (I hope I have that right). You will notice that you have to spin a little more each "day" to face the sun. That is the 2 milliseconds that accumilate to our leap seconds.
And if you notice, the size of your spin remains the same to see that spot on the far wall (which will become the near wall and then the far wall again). And it will always be same size spin.
I hope that makes sense.
And I do hope I didn't get any of it wrong.
Thank you for that detailed explanation ciberthug. It was helpful in my understanding of the whole matter!
Thats why I always feel that the day does by quickly. I'm getting gyped on my 2 milliseconds!!!Quote:
Originally posted by CiberTHuG
Matthew, a solar day is only off by about 2 milliseconds
Well, we are in tidal spindown, so its about 2 milliseconds longer. :)Quote:
Originally posted by spetnik
Thats why I always feel that the day does by quickly. I'm getting gyped on my 2 milliseconds!!!