Cecil, and SD readers,
I am told the mass of the earth, is reliably estimated at 6 sextillion, 588 quintillion tons (per SD of course). Now I am told that the earth weighs some trillion tons less than it should (if it was in minute separate pieces, and that the parts have more mass separately than together? What is going on? Is the sum of the Earth’s parts is really greater than the whole?
Is it gravity because I thought gravity had mass itself?
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In my edition of that book, they explain all that.
rocks
[sub]Originally posted by RM Mentock:[/sub]
And that explanation is what???
And the name of that book and edition is what???
Giving a book name reference or explanation would help.
Book or article name and edition, author, pages, publisher, city, year.
Well first of all, weight and mass are not the same thing. Weight (in layman’s terms, which is the only way I know them) is the pull of gravity on mass. That much I remember from HS physics.
As for your question, I don’t know. I’ll have to think about it. BTW, where did you hear this?
God is my co-pilot. Blame Him.
Yeah, the earth only weighs about five pounds.
I turned a bathroom scale upside down–therefore, the entire earth was resting on the scale.
It showed about five pounds.
Wow, that’s light enough to be carried by a swallow!
An African swallow, of course.
Well, maybe two European swallows.
On a line.
Joe Cool
Certainly wouldn’t hurt. Where did you hear it?
rocks
Five pounds sounded on the light side to me, so I also tried this to verify the weight. My only problem was that when my scale was upside down on the ground, I could not read it. How did you do this?
Maybe it was a talking scale?
“I must leave this planet, if only for an hour.” – Antoine de St. Exupéry
Are you a turtle?
Maybe used a second scale.
rocks
Naah - I’ll bet he just moved the earth aside for a second and took a look.
All very good ideas. Being the cheapest idea (I only have one scale, and it has never held a conversation with me), I tried to shift the Earth to the side for a sec to take a peak, but after doing it several times, I started to doubt the results. After all, I was touching what was being weighed. I think the average weight was around 3.67238551 pounds, but how much was I affecting the results? The talking scale thing would be ideal, but since I don’t already own one, it would also be expensive. The two scale set-up is more complicated, but in my price range. My only problem with this set-up is: how can I be sure there are no polarity issues touching the two scales together?
Do you have a glass table handy? You could set the table upside down on the scale, then carefully balance the Earth on the table legs. Repeat the measurement without the Earth, subtract the two and you’re done. 
It is too clear, and so it is hard to see.
HEY, HEY!!! You’ve got it ZenBeam! Thanks. I’ll post my results when I’m done so everyone can see if they agree with Mjollnir’s results.
I heard it on the radio originally. I found the article in Scientific American.
http://www.scientificamerican.com/2000/0200issue/0200scicit2.html
SCIENTIFIC AMERICAN
February 2000
THE NONNEGLIGIBLE LIGHTNESS OF GRAVITY
Physicists verify that even gravity itself has weight
Which states
"Planet Earth is about three trillion tons lighter than the sum of its parts. "
So much for web search engines … I’ll Check SA first.
Thanks…
Three trillion tons still seems a little close to an margin of error.
From the above article:
You know, there are times when I think folks are carrying this precision thing just a little too far.
Absolutely, there is a bit of the suspect in the superaccurate measurement. It’s the opposite of the “Mt. Everest is 29000 feet” problem, where the story goes that someone fudged the value because 29,000 looked like an estimate.
WillGolf & Dullwit, Amen.
This measurement requires a precision of one part in 10 billion. The posts above are saying the Earth doesn’t weigh 6.588 sextillion tons, it weighs 6.587999997 sextillion tons. Forgive me if I’m still skeptical.
Carl
What they are talking about is how much gravitational binding energy contributes to the Earth mass. This is independent of how well the mass of the Earth is known. If you eat a cookie which weighs 1/2 ounce, you know you will weigh 1/2 ounce more after eating the cookie, even if you only know your starting weight to the nearest pound.
It is too clear, and so it is hard to see.