What causes the tidal bulge on the far side of the Earth

OK, everyone i have asked this question to starts by saying thats obvious and it's taught very early on in diver training, but i do believe its a bit more complicated than you might first think. Any soon the people i ask say "oh, i'm not sure"... so here goes.....

Q."When the Sun and Moon are on opposite sides of the Earth you get Spring tides, when the moon is at right angles you get neaps, but why when the Sun and Moon are on the same side of the Earth do you get the tidal bulge on the far side of the Earth?"

Answers range from Centrifugal force, to Newtons Laws of motion to gravity being inversely proportional to the square of the distance.

What are your thoughts......

Ian

Try (for a good explanation)

<a href="http://www.projectsandhobbies.com/Moon.htm" >http://www.projectsandhobbies.com/Moon.htm</a>

or (for a pretty picture)

<a href="http://www.sp.uconn.edu/~geo101vc/Lecture20/sld024.htm" >http://www.sp.uconn.edu/~geo101vc/Lecture20/sld024.htm</a>

OK, everyone i have asked this question to starts by saying thats obvious and it's taught very early on in diver training, but i do believe its a bit more complicated than you might first think. Any soon the people i ask say "oh, i'm not sure"... so here goes.....

Q."When the Sun and Moon are on opposite sides of the Earth you get Spring tides, when the moon is at right angles you get neaps, but why when the Sun and Moon are on the same side of the Earth do you get the tidal bulge on the far side of the Earth?"

Answers range from Centrifugal force, to Newtons Laws of motion to gravity being inversely proportional to the square of the distance.

What are your thoughts......

Ian

Ian, interesting question, did a little research on the internet, the link may help

John

OK, everyone i have asked this question to starts by saying thats obvious and it's taught very early on in diver training, but i do believe its a bit more complicated than you might first think. Any soon the people i ask say "oh, i'm not sure"... so here goes.....

Q."When the Sun and Moon are on opposite sides of the Earth you get Spring tides, when the moon is at right angles you get neaps, but why when the Sun and Moon are on the same side of the Earth do you get the tidal bulge on the far side of the Earth?"

You get springs when the Sun, Moon and Earth are aligned, hence the full or new moon. You get neaps when the Moon and Sun are at right angles to the Earth.

AIUI The opposite bulge is caused by centrifugal force. Simply; the combination of gravitational forces and the centrifgal force from the Earths rotation causes the Oceans to squeeze.

Have a look here;
<a href="http://www.seafriends.org.nz/oceano/tides.htm" >http://www.seafriends.org.nz/oceano/tides.htm</a>
<a href="http://co-ops.nos.noaa.gov/restles1.html" >http://co-ops.nos.noaa.gov/restles1.html</a>

Q."When the Sun and Moon are on opposite sides of the Earth you get Spring tides, when the moon is at right angles you get neaps, but why when the Sun and Moon are on the same side of the Earth do you get the tidal bulge on the far side of the Earth?"
What are your thoughts......

Speaking as a man with a degree in oceanic & atmospheric physics, (most of which has been forgotten years ago) the answer is defintely Centrifugal force. The centre of gravity of the Earth moon system is not the centre of the Earth and so there is a force exerted on Ocean which move it as far as it can from this point, ie the far side of the Earth. The near tide is caused by gravity.

My tutor used the example of Scotsman throwing a hammer to illustrate the point (metaphorically not literally!): his kilt moves outwards directly behind him.

Laters,
Janos

I remember my physics lecturer repeatedly drumming into us that it was Centripetal Force and Centrifugal Reaction. Funny how things like that stick in your brain.

I remember my physics lecturer repeatedly drumming into us that it was Centripetal Force and Centrifugal Reaction. Funny how things like that stick in your brain.

Actually its neither :-)

Space is being bent in a centripetal direction and Newtons first law gives us an apparent reaction

:=I remember my physics lecturer repeatedly drumming into us that it was Centripetal Force and Centrifugal Reaction. Funny how things like that stick in your brain.

Actually its neither :-)

Space is being bent in a centripetal direction and Newtons first law gives us an apparent reaction

Hear hear, just what I was thinking!
What was the question again?
Errrrr....
Can't we just say that it's because the earth 'knows' to have a lump of water on the other side so that it doesn't get into a nasty wobble?
A wobbly earth, scary stuff. We just don't want to go there.
The water is actually trying to leave and the earths gravity is holding on to it, some of it gets missed though, and it runs around the other side of the earth, and tries to get out the back door.
Simple.
;-)

:=I remember my physics lecturer repeatedly drumming into us that it was Centripetal Force and Centrifugal Reaction. Funny how things like that stick in your brain.

Actually its neither :-)

Space is being bent in a centripetal direction and Newtons first law gives us an apparent reaction

My memory was close - It was over 20 years ago !

This might help (then again it might not!!)