A trivial question but who can answer it ? (Friend from Algeria)

Jimmy

So, would your friend say that the weight of objects is due to the rotation of the planet? If so, how would he explain that things weigh only slightly less on Venus as compared to Earth (90%). Yet Venus has a very slow rotation period of 243 days (.4% of Earth's rotational period). I don't think Venus could hold on to its atmosphere if it had to depend on its spin.

Seems more likely weight is due to surface gravity which depends on the mass and the radius of the planet in question and not spin. Venus is very close to the same size and mass of the earth. Its surface gravity is close to that of Earth as well.

There are endless arguments one could make to refute your friend's belief.

benbr

Thank you very much
I think I can take it from here.
Problem solved. I have what is takes to prove my opinion right.

Astronuc

Objects weigh more at the poles than at lower latitudes. The lighest weight of an object would be at the equator. An object weighs less flying in the direction of rotation than flying opposite.

The earth's diameter is less at the poles than at the equator.

Equatorial radius 6,378.1 km[7][8]
Polar radius 6,356.8 km[9]

[7] "Selected Astronomical Constants, 2011". The Astronomical Almanac. http://asa.usno.navy.mil/SecK/2011/A...tants_2011.txt. Retrieved 2011-02-25.
[8] a b World Geodetic System (WGS-84). Available online from National Geospatial-Intelligence Agency.
[9] Cazenave, Anny (1995). "Geoid, Topography and Distribution of Landforms". In Ahrens, Thomas J (PDF). Global earth physics a handbook of physical constants. Washington, DC: American Geophysical Union. ISBN 0-87590-851-9. Archived from the original on 2006-10-16. http://web.archive.org/web/200610160...5_cazenave.pdf. Retrieved 2008-08-03.

Ref: http://en.wikipedia.org/wiki/Earth

Drakkith

Bam.
http://en.wikipedia.org/wiki/Gravitation

References are in the article.

alialice

http://en.wikipedia.org/wiki/Gravitation
As a reference you can present this: Wikipedia is a virtual encyclopedia. In the section Earth's gravity it is written explicitly that:
Every planetary body (including the Earth) is surrounded by its own gravitational field, which exerts an attractive force on all objects.
Other references:
http://galileo.phys.virginia.edu/cla...tyLectures.pdf from Virginia University
http://www.universetoday.com/26775/g...-of-the-earth/

http://ocw.mit.edu/courses/physics/8...res/lecture-7/

Swankie

If that is his take on physics then ask him exactly how the rotor of a helicopter makes it go into the air =D

Darwin123

The more interesting question here is how this drives you crazy. However, that may be more relevant in the sociology forum.
The fellow is obviously a phony. He obviously has no rational rebuttal to your arguments. In fact, he provides no firm evidence that he believes it himself. Obviously, you are under no obligation to correct him. Yet, you feel bad for not being able to correct him.
I have similar problems. It is common on the Internet, but it is common even in old style informal discussions. I have gotten into screaming fits at people like you described. Afterward, I wonder why I did that. My fit was at least as irrational as his belief. A lot of people on the internet have this compulsion to "convince" loonies. The loonies are obviously stupid. Yet, there seems to be a pathology on the other side. I have often wondered why I feel compelled to argue with these people. And feel bad when they repeat their arguments. Yet, I can't precisely pin down why.
May I suggest that you make a new post in the Section on Social Sciences. Ask why many people like us want to defend their intellects against persistent cranks. Ask why people like this insist on telling people about their hypothesis. I myself would like to discuss this in a public forum.
I wonder if there are any professional studies of this. Psychologists and sociologists must have examined this already. Maybe we should do an Internet search for scientific studies of this social phenomenon.