If the Earth weren't moving during the Venus transit

Insanely Ranted:
The earth is the center of the solat system so it doesn't move...everything
else does...

(Bettrel) wrote in message ...

Well, technically speaking, wouldn't it be true that the frame of reference
consisting of a fixed Earth with everything else moving is as valid as any
other reference frame?

I don't think so. The Earth is spinning, which is a form of
acceleration. This means that the Earth's reference frame is not
inertial, and cannot be considered "fixed" under relativity.

Why is the difference important? Here are a couple of illustrations
that don't require math or anything:

1. Galileo gave this simple illustration of relativity: If one is in
a boat with no windows, it is impossible to tell whether the boat is
stationary or moving in a straight line. However, if the boat is
turning, you can feel it, or even see the chandelier tilting, even
though you can't see outside.

2. Spin around 360 degrees. That should take about 2 seconds. Does
that mean that, relative to you, the Sun has moved up to 940,000,000
km in two seconds? That's more than 3000 times the speed of light!
Although the Earth spins much more slowly than that, i think the
concept can be generalized.

(Someone *please* correct me if i'm wrong or off-base.)


Clear skies!

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------------------- Richard Callwood III --------------------
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Cousin Ricky wrote:
I don't think so. The Earth is spinning, which is a form of
acceleration. This means that the Earth's reference frame is not
inertial, and cannot be considered "fixed" under relativity.

It certainly can. The tensor field has to be adjusted to account
for this, but it can be done. Close to the Earth, it's something
like diag(1+wr*cos(phi), 1-wr*cos(phi), ...); can someone who knows
what they're doing work it out for real?

2. Spin around 360 degrees. That should take about 2 seconds. Does
that mean that, relative to you, the Sun has moved up to 940,000,000
km in two seconds? That's more than 3000 times the speed of light!
Although the Earth spins much more slowly than that, i think the
concept can be generalized.

I forget how this is resolved in GR, but it is resolved.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
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(Bettrel) wrote in message ...
The earth is the center of the solat system so it doesn't move...everything
else does...

Well, technically speaking, wouldn't it be true that the frame of reference
consisting of a fixed Earth with everything else moving is as valid as any
other reference frame?

Hi
The earth is in an orbit. This means it is constantly
in an accelerating field. If we were just moving along
at a constant speed in one direction, then we could
be a reference frame but we keep changing direction.
Dwight

dwight elvey wrote:

(Bettrel) wrote in message ...
The earth is the center of the solat system so it doesn't move...everything
else does...

Well, technically speaking, wouldn't it be true that the frame of reference
consisting of a fixed Earth with everything else moving is as valid as any
other reference frame?

Hi
The earth is in an orbit. This means it is constantly
in an accelerating field.

The Earth orbiting the Sun is being accelerated by the force of gravity
F = ma "accelerating field" is not a term used in physics that I know of.

If we were just moving along
at a constant speed in one direction, then we could
be a reference frame but we keep changing direction.
Dwight

Sam Wormley wrote in message ...
dwight elvey wrote:

(Bettrel) wrote in message ...
The earth is the center of the solat system so it doesn't move...everything
else does...

Well, technically speaking, wouldn't it be true that the frame of reference
consisting of a fixed Earth with everything else moving is as valid as any
other reference frame?

Hi
The earth is in an orbit. This means it is constantly
in an accelerating field.

The Earth orbiting the Sun is being accelerated by the force of gravity
F = ma "accelerating field" is not a term used in physics that I know of.

Thanks for clarifying my poor terminology. I simply meant that
since we were constantly accelerating, it is hard to get the rest of
the universe to wobble around us. While if we were moving along at
a constant direction and speed ( not accelerating ), we couldn't
tell if we were moving or if the universe was moving and the Earth
was a fixed reference.
Dwight


If we were just moving along
at a constant speed in one direction, then we could
be a reference frame but we keep changing direction.
Dwight