they said the earth is slowing down. how do we measure the speed any way?

Answer 1

It's measured with Very Long Baseline Interferometry (VLBI). Astronomers measure the position of quasars very precisely, and from that they can determine how fast the Earth is revolving. It seems to be slowing down (length of day) about 1 or 2 milliseconds per year. When the daily differences add up to a whole second, the time authorities put in a leap second to keep things lined up.

There is an idea that the changes in the Earth's rotation rate are the result of coupling (friction) between the moving core and mantle.

Answer 2

Just to clarify - Earth's rotation is what is slowing down. Earth's orbit around the Sun is constant and not changing in speed. Not that anyone's noticed, anyway! So the number of seconds in a day is (slowly) increasing, but the number of seconds in a year is staying constant.

Answer 3

if u mean the earth's rotation is slowing down, then days would get longer and longer.

if you mean the earth's revolution around the sun is slowing down, then we can measure the time it takes to get to constellations in the sky for each month, and see how it compares with previous records of how long it took to get to the point where a certain constellation is in the sky.

hope this helps :/

Answer 4

You need a point of reference, such as a far away (for stars) star. Then you measure the time it takes for the star to line up with a a telescope turned into a sight.

Answer 5

By comparing the astronomical year to an atomic clock.

Answer 6

By astronomical observations in different points of time.

Answer 7

The sun, duh.. people were using the sun as a point of reference for time for thousands of years. we know the circumference of the planet due to some geometrical formulas.. if you know the radius then... blah go look it up.