The Earth

[BertiWooster]

OK I Guess to many this is a silly question , but try not be too cutting in your responses .
I need an explanation for a child

The shape of the earth is a sphere , like a football
Hold that football in your hand
Where it is resting in your hand , why aren't things on the surface of the earth there ' hanging ' upside down

[chakka35]

Because what is called gravity is an attraction between something on the surface of the earth, wherever that something is, and the the earth itself.
Ask your child to imagine an iron ball which is magnetic. Wherever you put an iron figure (soldier, ballet dancer) on that ball it will stick,whatever you consider the 'up' or 'down' of that ball to be.

[BertiWooster]

I understand that gravity holds you to the surface .

What i'm getting at is - given that the earth is a sphere in shape - why is it that where ever people are on it's surface -as you look at the sphere - whether it is the top / bottom / sides - you're not in a horizontal to , or upside down position to the surface ; with respect to the side and bottom of the sphere , respectively .

I know what i'm trying to ask but it is difficult to convey - i think coming up with an answer for the financial crisis might be easier

[chakka35]

It's because 'down' is always the direction between you and the centre of the earth,wherever you are.

Take an apple and stick map-pins in it all round. For each map-pin 'down' is between it and the centre of the apple.

[THECORBYLOON]

If a fly were to land on the very top of the football call that the North Pole. If it walked all the way round it to the bottom, the South Pole, its feet would still be touching the surface would it not? The fly hasn't turnt upside down has it? By the same token, that's why folk on opposite sides of the globe have their feet on the ground.

[ChuckFickens]

Up and down are not real measurements or values.(though they are quarks but that's another lesson:)) they only exist in our minds and are relative to our surroundings.

From where you are standing if zoomed out several thousand miles your up would be the down of a person on the other side of the world and vice versa.

You are being pulled towards the middle of the earth by gravity and due to life conditioning you call this "down" but down isn't a real direction, it's just what we have been conditioned to call what the attraction to the nearest big enough mass is (i.e. planet)

Start thinking about more than one planet and the you'll see why up and down don't really exist

[mibn2cweus]

Gravity is an apparent attraction between objects in proportion to how much matter they possess and how close they are to each other. It takes a very large body of matter (such as the Earth) to produce an appreciable gravitational attraction. For a spherical object, of uniform distribution, gravity appears to draw anything on or above its surface towards a point of equivalent mass located at its centre. This is the predominant direction in which objects on the Earth�s surface are pulled.

When your standing on the surface of the Earth your engaging in a complex process of working to maintain your balance and upright position in defiance of the tendency of gravity to pull you toward the centre of the Earth with only the ground beneath your feet acting to impede you from such a journey. This is a skill that for human beings requires many months to acquire but once mastered soon becomes second nature. In a year or two the difficulties of standing upright and balanced in defiance of gravity is now virtually automatic and taken for granted. The same skill must nevertheless always be employed to achieve this feat. If this ability were to abandon you for even a second you would collapse down on and conform to whatever surface you happened to be previously standing provided that it was capable of supporting you in that position.

Once you understand the causal relationships involved it should become clear why wherever we stand on the sphere of the Earth we always stand with our head pointing away from the Earth�s centre . . . unless your standing on your head . . . �

[wildwood]

I think I understand your son's curiosity. The reason people at the Antarctic don't appear to be walking upside down is that it is all a matter of orientation. To give maps a uniformity, the approximate magnetic North of this planet is usually envisaged as being on top to give references of geographical places some perspective, and indeed, the whole universe is referred to in relation to Earth's North being on top. In South America we would also appear to walk upright because we can not see beyond the horizon.

You might be able to explain it to your son by having him turn around a few times blindfolded, and guess which way he is facing.
In jets and spacecrafts a gyroscope is necessary to show which way the craft is banking because we are isolated from gravity and can not see the ground (unless it is a clear day ofcourse), without it we could be flying upside down without knowing it..

[BertiWooster]

thanks to you all folks - i'll have a good read later , when the boss isn't peering over my shoulder .

Just very briefly glancing at the posts , what i was getting at is the anolagy of the fly walking around the football - when it is on top of the football - it is upright as we look at it - however when it reaches the bottom of the ball - it is ' hanging' as we look at it .

What the little one was asking is why people on the earth at the bottom of the ball , dont get the feeling that they are 'hanging off ' the earth

[ll_billym]

Because "up" is the outside of the ball and "down" is the inside of the ball. This is true wherever you are on the ball.

Things on the ball do not feel like they are hanging off it because "down" is always inside the ball.

We are outside the ball so when we look/touch it we have a different sense of what up and down are but to things on the ball, whichever way we look/touch it, we are "up" and the inside of the ball is "down".