If the earth has great mountains, such as the Himalayas, in some places and great valleys, such as Death Valley etc. in other places, how does it appear perfectly round and why do all the planets in our solar system appear perfectly round?
2007-10-31 12:18:31 · 6 answers · asked by billie d 1 in Science & Mathematics ➔ Astronomy & Space
It is all a matter of perception.
The highest mountains on the Earth are less than 4 miles high. Yet the Earth has a circumference of roughly
25,000 miles. It is not normal for the human eye to see
imperfections at the level of 4 / 25000 = 0.00016
or at even half that (because you can only see 1/2 of the
Earth at any given moment)...
4 / 12500 = 0.00032
Consider a golf ball...up close you can see the dimples on
the surface. From a distance it appears perfectly round.
Consider a standard baseball... Up close you can see the
stitching higher than the leather surface of the ball. From a
distance, however, the ball looks perfectly round.
2007-10-31 12:36:16 · answer #1 · answered by zahbudar 6 · 3⤊ 0⤋
They aren't perfectly round, but all the planets are almost-perfect spheres. Gravity pulls the material of the planet towards the centre, and that creates a spherical shape.
Mountains and valleys and all the other features on Earth are extremely tiny in comparison to Earth's size, so from a distance (such as the moon or farther) the Earth would appear relatively smooth - those features would just be too small to be noticeable from any distance.
Pictures from the space shuttle and other orbiting craft show that the mountains and valleys and other features really don't show up much.
But some planets (such as Earth, Jupiter, and Saturn) spin fast enough that their equators are "lifted" up a bit against gravity, and so those planets are very slightly squashed spheres (oblate spheroids).
But for Earth, the variation from perfectly spherical is very small - only about 44 km difference between the polar diameter and the equatorial diameter.
2007-10-31 19:29:19 · answer #2 · answered by Anonymous · 3⤊ 0⤋
It is due to the rotational movement all planets posssess....The centrifugl force tries to moev everything away from the planet and the gravitational force tries to grab onto everything....The result is the shape.
The answer to why it appears round even if we have mountains and valleys is because of this phenomenon:
Lets say you took a baseball/cricket ball...What is it like: round right? But look at the center...of the ball..there is some grip around the ball to attain the grip for the bowler...The grip is usually full of crests and troughs....even though they are there..we call it a circualr shape...coz...when compared to the size of the earth which is spherical.........these imperfections won't count.
Hope that helps.
2007-10-31 19:25:04 · answer #3 · answered by That's me ... 3 · 0⤊ 2⤋
because all of the gravity in the planets is pulling toward the center of it with equal force, so it is only natural that the planet looks round, since a the surface of a sphere is equidistant from the center.
2007-10-31 19:24:17 · answer #4 · answered by Anonymous · 1⤊ 0⤋
Most planets are not round but spherical in shape and tend to "bulge" at their equator. This is due to their speed of rotation around their axis.
2007-10-31 20:21:54 · answer #5 · answered by stargrazer 5 · 0⤊ 0⤋
Here's a bad analogy for you:
Why does a basketball appear round with all the divots and bumps all over it?
2007-10-31 19:35:28 · answer #6 · answered by Milo 3 · 0⤊ 0⤋