Earth tide

The solid crust is subject to a twice daily tidal wave, the earth tides. Analogous to the tides on the oceans and large inland seas - the so-called Tides and tidal - they are created by the tidal forces of gravity of the Moon and the Sun on the Earth.

Size and measurement

The raising or lowering is about -30 to -60 cm. It is not directly felt by humans. The effect, which accounts for only about one- millionth of the earth gravity, can only be measured with high precision gravimeters ( extremely fine " spring scales " ) and special Erdgezeitenpendeln. The latter operate on the principle of a door Angel: When the axis is just a little out of plumb, the door is often already half open. The Lotrichtungsschwankungen by the moon's orbit, however, be not a few tenths of a degree (such as at a inaccurate battered door ), but only about 0.2 " ( 0.00005 °).

Such measurements are only to completely shock-and vibration-free places to perform, preferably in disused mines or tunnels. Two of these stations are in Schiltach (Baden- Württemberg) and Schlossberg ( Austria ).

Permanent Tide

Geophysical context

The Earth is not a rigid body, but responds elastically to the lunar and solar gravitation. The Earth tides are therefore no "movement" as in short-term earthquake or in the long-term mountain building, but rather a vibration ( Erdspektroskopie ). Against such forces are periodic body of the earth after much more quickly than with long-acting forces such as mountain building, whose effect makes up only a few millimeters per year.

The Earth tides are in addition to seismic waves, a further independent effect, by which the properties of the Earth's crust and the upper and lower mantle (eg, viscosity or sag ) can be explored in the Erdspektroskopie.

• Geophysics
• Geodesy
• Gravimetry