Halo
Well-Known Member
If interested see the link below
http://www.bbc.co.uk/programmes/p04...ture&intc_linkname=vidclip_tides_contentcard7
http://www.bbc.co.uk/programmes/p04...ture&intc_linkname=vidclip_tides_contentcard7
AT last a clear explanation of how we get 2 tides per day !
- Thread starter Halo
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Halo
Well-Known Member
bedouin
Well-Known Member
Oh dear - surely someone as clever as Brian Cox knows there is no such force as "centrifugal force".
ex-Gladys
Well-Known Member
And how does he explain those places (Gulf of Mexico or Vietnam) where there is only one tide per day?
oldbilbo
...
Maybe that's down to those 'lazy Mexicans'...
And I s'pose explaining the 240-odd Harmonic Constants and 'resonant chambers' would take up too much broadcast time. So, two beach pebbles.... on an exotic beach.
Pye_End
Well-Known Member
Is it accurate (apart from the centrifugal force terminology)? Does the bulge on 'the other side' occur because it is further from the gravitational pull of the moon, and the difference is significant? Or is it that when you resolve the forces, the component trying to move the sea sideways at that point is virtually non-exisistant?
Halo
Well-Known Member
The reason the clip is brilliant is that it is simple and comprehensible to normal people. Whilst it would be more correct to refer to the reaction to centrepetal acceleration required to maintain a fixed radius from the centre of a rotating object I suspect this would not be nearly as comprehensible to most people.
Halo
Well-Known Member
I think its because the earth is swinging around a point between the earth and moon ( the centre of mass of the earth moon system) and the sea on the far side is at a greater radius from this point and therefore the water is being flung outwards more than that which is nearer the centre of rotation
Blue Sunray
Well-Known Member
Really, I assume that you haven't heard of centripetal force and/or Newton's third law then?
macd
Well-Known Member
It would be even more correct to refer to 'centripetal'
But it's all tosh. There's no gravity: the Earth sucks.
But then there's really no such thing a suction...:ambivalence:
PaulRainbow
Well-Known Member
I think you'll find it's all done with mirrors.
Blue Sunray
Well-Known Member
You what? Centripetal is a direction - the opposite being, of course, centrifugal. Accelerations aren't the things that are generally considered to have reactions, forces however do, per Newton III.
Blue Sunray
Well-Known Member
Rubbish, it's magic.
bedouin
Well-Known Member
There is not really enough information in the video to understand his explanation but I am almost sure he is wrong.
One of the reasons no scientist would talk about centrifugal force is that it doesn't exist - so it tends to be introduced to gloss over a lack of understanding of the forces that are actually acting on a body.
Amulet
Well-Known Member
I think it's a crappy explanation, if not bollocks. The inverse square law is enough to explain the tides.
You could argue that the two explanations are equivalent. If gravity is the centripetal force and diminishes as the square of the distance, then it's less on the far side of the moon. If you are willing to regard diminution of centripetal force as an increase in (non-existent) centrifugal force then you might give some credit to his half-assed explanation.
However, why would you invoke two concepts to explain something that is simple to explain with one? Bad science.
You could argue that the two explanations are equivalent. If gravity is the centripetal force and diminishes as the square of the distance, then it's less on the far side of the moon. If you are willing to regard diminution of centripetal force as an increase in (non-existent) centrifugal force then you might give some credit to his half-assed explanation.
However, why would you invoke two concepts to explain something that is simple to explain with one? Bad science.
Blue Sunray
Well-Known Member
...but of course gravity (g) is not a force.
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Amulet
Well-Known Member
Newtons Law is a good approximation and allows interpretation of gravity as a force. By the same token you can argue that, within the frame of reference of the spinning, centrifugal force exists. My primary complaint about the weak geek explanation is that it invokes two different models where only one is required, and so creates a complex explanation where a simple one would have done just fine.
macd
Well-Known Member
So tides are actually a result of the curvature of spacetime?
That'll set the OP's mind at ease.
Daydreamer
Well-Known Member
Oh the conceit.It might actually be better to talk of Centrifugal effect as with the Coriolis effect. One might well use Gravitational effect as well as they are all fictitious forces.
Brian Cox is attempting to show something less immediately obvious which is the very well understood classical idea of Barycentre. In my opinion this is much better demonstrated by an animation graphic. Google will help
bedouin
Well-Known Member
No - you are missing my point. It is not just about terminology it is about the genuine forces involved.
It might actually be better to talk of Centrifugal effect as with the Coriolis effect. One might well use Gravitational effect as well as they are all fictitious forces.
Brian Cox is attempting to show something less immediately obvious which is the very well understood classical idea of Barycentre. In my opinion this is much better demonstrated by an animation graphic. Google will help
I think Cox is wrong in his explanation and his invocation of a non-existent force is hiding the error in his theory. He needs to be more explicit about what is rotating about what and how fast - there are too many different rotations involved