How do scientist know exactly how fast the Earth is spinning and when was it discovered that it was spinning?

Answer 1

When they felt giddy and fell over.

Answer 2

A couple of others mentioned how it was proven that the Earth was spinning. The rate of spin can be found by measuring how long it takes to go from local noon to local noon (pretty close to 24 hours).

You rotate 360 degrees (approximately) or 2PI radians in 24 hours. Divide the 360 or the 2PI by 24*60 minutes*60 seconds (there's 86400 seconds in a day) and you have the rate that the Earth rotates.

Technically, you also have to take into account the fact that the Earth is orbiting the Sun, so we actually rotate almost 361 degrees per day, but 360 in 24 hours is close enough for most purposes. Close enough that every 15 degrees in longitude means we need a new time zone (360 divided 24 hours gives you 15 degrees per hour, a much easier number to remember than the number of degrees per second or radians per second).

Answer 3

OK!

They intuitively "know" the same way that you do. The sun reaches its highest position in sky every ~24 hours. Either the sun is actually moving or it *appears* to move relative to the earth. The latter implies that it is the earth that must be moving. The apparent movement of the sun is an arc. Therefore, the actual moverment of the earth must be a turning. If the earth is a ball, that turning is called spinning on itts axis. This is, however, a circumstantial argument with lots of built-in assumptions.

The first *formal* scientifc proof was by Foucault in the 1800's. He used a long pendulum and found that the plane of oscillation of the pendulum changed after a few minutes. Using Newtonian theories of force and gravity, he proved mathematically that the earth must be turning on its axis.

http://www.as.utexas.edu/astronomy/education/spring01/lambert/classnotes4.html


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Answer 4

the first person to PROVE the earth was spinning was gallileo, he hung a pendulem from a room and set it in motion so it brushed against sand, a few hours later the track had moved, because although the pendulem was going the same way the earth had moved, and as for how do they know how fast? by calculating the earths size against the fact that a day is just over 24 hours long, they can work it out

edit: sorry i stand corrected just checked this answer online and it was actually invented by Jean Foucault

Answer 5

They use points of reference to determine how fast it is moving in relation to those points.

Answer 6

The sky at night should give you a clue.