Earth poser

[cazzz1975]

If the earth is moving at 64 thousand miles an hour around the sun, Why dont we feel the motion?

[Clanad]

A number of reasons... the motion is constant... there is no acceleration or deceleration. Were moving at the same velocity constantly. Additionally, at the equator, the Earth is also spinning at nearly 1,000 mile per hour on its axis. All of these motions are constant and do not impose the sense of motion of the semi-circular canals of the inner ear's vestibular system, since that system require accleration to move the fluids against the tiny "hairs" feeding our brain for a feeling of motion...

[nescio]

Oh come on Clanad - you disappoint me.
Motion in a circle - no acceleration ? Constant velocity ?

Constant speed,yes.

A better answer is that the overall effect of the Earth's gravitational field and the acceleration due to the Earth's motion involved is so smal as to be unnoticeable.

Just to be pedantic

[Clanad]

Equally as pedantic, nesico, the standard definition of acceleration is: The rate of change of velocity over time.... if there's is acceleration (or deceleration) it is so small as to be undectable, especially by the semi-circular motion sensing system inherent in each of us...

Certainly I could have talked about velocity being a vector quantity...the rate of change of velocity over time and speed being a scalar quantity, or how fast an object is moving... but I was choosing to answer the question as simply as possible since the audience was unknown...

[mibn2cweus]

I actually thought Clannads first answer was quite good and would have left it at that but as long as there's a war on . . . count me in.

The Earth is in orbital freefall around the Sun and so are we along with it. The "pull" of gravity is not felt by an object in freefall as other than the unusual sensation of "weightlessness".

There is a slight difference between the mutual attraction between a human or the Earth and the Sun because the Earth with its large mass contributes slightly more to the mutual attraction between it and the Sun than we do but this difference is insignificant compared to the gravitational pull we feel from the much closer Earth. This difference in gravity must however be taken into account when determining the precise orbital path of a satellite around the Earth. An unbalanced satellite will tend to orientate its heavier end away from the Earth.

A much more pronounced effect we do have to compensate for and which in the beginning presents a challenge to us, remaining on our feet by aligning our upright orientated centre of gravity with the Earth's centre of mass, has for most of us become "second" nature.

The effect of Earth's gravity, slightly diminished at the bulging equator is further reduced by the angular momentum contributed by the Earth's daily rotation about its axis. Together this combination reduces ones measured weight as compared to that measured at the poles by less than one percent. The change in weight we experience daily and seasonally as we alter our orientation to and distance from the Sun is much less significant.

On second thought I don�t have time for this right now but it has been interesting to consider some of the more subtle nuances of this question although I might have already gotten myself into more trouble than I can handle.

My oh my, how time does fly ~ ~ ~ ~ ~ ~ ~ <o/"\o>

[heathfield]

Goodness me! And I thought it was Indian lawyers who had the reputation of being able to split hairs to the nth degree!
Clanad's first sentence explains the reason, just as you have no sense of motion when you're in a car, a train, or a plane when travelling at constant speed.