Truely universal time and distance

[Gerry]

I get the impression that someone is getting 'g' and 'G' confused.

It does appear to be that way. I expect to hear the sound of goalposts being scraped along the floor any moment now though.

 

[_xxx_]

In the link above, there are neither anomalies or workarounds. They are corrections to the first order approximation that Earth is a perfect sphere of homogenous density.

Oh, such a tragedy, I really didn't bother fully reading a random one of the million links google gave me on this topic. And silly me didn't even bother to double-check every word just to satisfy some internet trolls, imagine that! Duh.

But even a brief look shows the word "anomaly" and "correction" twice in the chapter titles. I guess they call them so because they are "neither anomalies nor workarounds"

nutball: already answered with the link in one of the posts above. There is no consensus on the "correct" g value in today's science as of yet.You may also enjoy this info here:

Anomalies and discrepancies

There are some observations that are not adequately accounted for, which may point to the need for better theories of gravity or perhaps be explained in other ways.

* Extra fast stars: Stars in galaxies follow a distribution of velocities where stars on the outskirts are moving faster than they should according to the observed distributions of normal matter. Galaxies within galaxy clusters show a similar pattern. Dark matter, which would interact gravitationally but not electromagnetically, would account for the discrepancy. Various modifications to Newtonian dynamics have also been proposed.

* Pioneer anomaly: The two Pioneer spacecraft seem to be slowing down in a way which has yet to be explained.[21]

* Flyby anomaly: Various spacecraft have experienced greater accelerations during slingshot maneuvers than expected.

* Accelerating expansion: The metric expansion of space seems to be speeding up. Dark energy has been proposed to explain this. A recent alternative explanation is that the geometry of space is not homogeneous (due to clusters of galaxies) and that when the data are reinterpreted to take this into account, the expansion is not speeding up after all[22], however this conclusion is disputed[23].

* Anomalous increase of the astronomical unit: Recent measurements indicate that planetary orbits are widening faster than if this was solely through the sun losing mass by radiating energy.

* Extra energetic photons: Photons travelling through galaxy clusters should gain energy and then lose it again on the way out. The accelerating expansion of the universe should stop the photons returning all the energy, but even taking this into account photons from the cosmic microwave background radiation gain twice as much energy as expected. This may indicate that gravity falls off faster than inverse-squared at certain distance scales[24].

* Dark flow: Surveys of galaxy motions have detected a mystery dark flow towards an unseen mass. Such a large mass is too large to have accumulated since the Big Bang using current models and may indicate that gravity falls off slower than inverse-squared at certain distance scales[24].

* Extra massive hydrogen clouds: The spectral lines of the Lyman-alpha forest suggest that hydrogen clouds are more clumped together at certain scales than expected and, like dark flow, may indicate that gravity falls off slower than inverse-squared at certain distance scales[24].

http://en.wikipedia.org/wiki/Gravitation

 

[rpg.314]

But even a brief look shows the word "anomaly" and "correction" twice in the chapter titles. I guess they call them so because they are "neither anomalies nor workarounds"

That explains it.

 

[Davros]

Ok I'm going to need the help from the clever people here to check over my calculations and fill in the blanks.
XXX of course knows the forces acting on a pinball are almost negligible and "there's not even a need to bother calculating that, it's that obvious."
Unfortunately I dont posses XXX's superior intellect so i had to do some research and calculations

So how far have we come :

First some constants
Weight of a pinball = 80grams
diameter of a pinball 1 inch
diameter of a baseball 9 inches

According to Nasa 3 major variables affect the force on a spinning ball
they are :
1. Size of the ball
2. Spin speed
3. Speed of forward motion
(there are of course others but they are minor - Cant wait till XXX says "ha who came up with that applet, rocket scientists" Well yes actually they did )


In the picture the strobe is set to 60/sec and we can work out that it takes 30 exposures
for the non spinning ball to reach the top of its flightpath or 0.5 seconds.
We know the pinball has a diameter of 1 inch or 3 pixels and by counting the pixels we can
deduce the height of movement is 336 pixels. 3 pixels per inch = 112 inches in 0.5 seconds
or 224 inches per second.
that gives us a movement speed of 18.66 feet per second or 12.72 Miles per Hour

Unfortunately the applet wont let me enter 12.72mph as a speed (it's a slider and starts at 30mph) but we do know that the force produced is proportional to the speed
(double the speed/double the force - half the speed/half the force) so we can enter 6X the speed and divide the force by 6 to get the correct result.
thats 76.32mph
(because of the slider the closest I can get to this is 76.34mph 0.02mph out but because im calculation a 6th of that speed I will be out by 0.0033(Recurring)mph
so there will be a slight error)

We can figure out that a 9 inch ball traveling 76.34mph spinning at 1,000rpm produces 26.308 grams of force.
first we need to divide 26.308 by 6 to get the true speed that leaves us with 4.38 grams of force.
Next we have to multiply 4.38 by 27 because the pinball is spinning at 27,000 not 1,000 that gives us 118.386 grams of force
finally we have to divide 118.386 by 9 (diameter of a pinball is 1/9th of a baseball) we end up with 13.154 grams of force applied to the spinning pinball

In other words the spinning pinball is generating 13.154 grams of lift or it weighs 66.846 grams (80g - 13.154g)
(Note: of course the spin of the ball is diminishing from the moment its launched and I'm having to assume its constant because I have know way of knowing the rate of slowdown
hopefully its not too much after only 0.5 seconds)

So heres where I need the help of some of the clever people
Would a device capable of launching a ball weighing 80grams 112 inches (9ft 4) into the air
be capable of launching a ball weighing 66.846grams 118 inches (9ft 10)
I'm not sure how to work the last bit out..

 

[WhiningKhan]

I get the impression that someone is getting 'g' and 'G' confused.

Heh, I typed almost the exact same words yesterday in the reply box, but canceled the reply as I thought _xxx_ was annoyed enough already... But now that you did it, what the hell.

nutball: already answered with the link in one of the posts above. There is no consensus on the "correct" g value in today's science as of yet.

You might have wanted to use 'G' instead of 'g' again...

 

[_xxx_]

It is valid for both g and G as already mentioned. Both are not a constant.

But feel free to present any sort of proof which will prove me wrong, anytime.

Davros: don't forget that the pinballs are moving with mere 2-3 m/s here, while the baseball does >100 km/h. That's why I call it negligible in comparison.

 

[Davros]

eh, theres 13grams of force being applied to an object that weighs 80grams thats over 15%

 

[_xxx_]

You are calculating with the wrong speed there, see above. Also this way or the other, that still fails to explain the trajectory - in which direction(s) does that force work?

And can't we move this discussion into a separate topic?

 

[rpg.314]

It is valid for both g and G as already mentioned. Both are not a constant.

For the love of God, why should g be constant?

Davros: don't forget that the pinballs are moving with mere 2-3 m/s here, while the baseball does >100 km/h. That's why I call it negligible in comparison.

What is our criteria for calling something negligible? 2x smaller/5x smaller/10x smaller/ what?

 

[WhiningKhan]

It is valid for both g and G as already mentioned. Both are not a constant.

'g' is not intended to be a constant in the sense you are referring to. It's just a unit for expressing acceleration in reference to a selected fixed value, just like pressure of one atmosphere is a reference value for pressure. Saying that we don't understand g is like saying we don't understand number 6 (which might make sense to Gaius Baltar, though).

 

[_xxx_]

Whining, see topic title.

 

[_xxx_]

For the love of God, why should g be constant?

Read the topic title and the first page of the discussion. We are looking for a truly universal reference for time and distance.

What is our criteria for calling something negligible? 2x smaller/5x smaller/10x smaller/ what?

"Not significantly affecting the result", or the result will deviate very little with or without that parameter involved. In this case, from the top of my head I'd say at least factor 10 difference between these two balls moved with same speed, or much more with the speed difference we have here.

To explain it in a simpler way, throw the pinball ball with the same speed like the baseball and you will see very little influence of air drag on the former in direct comparison.

 

[rpg.314]

Read the topic title and the first page of the discussion. I didn't bring gravity into this topic.

Nice dodge there.

 

[_xxx_]

What dodge are you talking about and why is that relevant? My statement hasn't change ever since the first answer on this OT topic. There is nothing constant about gravity or the speed of light and these can thus not be the reference we're looking for in this thread.

 

[WhiningKhan]

There is nothing constant about gravity or the speed of light and these can thus not be the reference we're looking for in this thread.

The point you missed is that 'g' is not a constant for gravity, it's a unit for acceleration. Its value is only fixed to units of length and time.

Which leads us back to the original topic: You can whine forever about something not being exactly defined since you are never going to reach absolutes for anything with finite measurement accuracy. The only thing that matters is whether the accuracy of the agreed values is sufficient for the purpose they are being used.

It would be interesting to hear why do you think there is nothing constant about speed of light so that it could not be considered as a universally usable value. What could be then? I'm assuming you will answer 'nothing', which again leads the discussion off the topic, from the domain of science and engineering into philosophy and religion.

EDIT: OK, re-reading first page reveals that this gravity stuff started when you replied that gravity influences speed of light. Maybe we shouldn't spin that wheel anymore. Let's just all agree that everything is relative and all values are approximations depending on certain conditions, but taking the conditions into account, acceptable approximations can be found.

 

[_xxx_]

I answered that on page 1, speed of light is affected by gravity and our "constant" c is more or less an arbitrary value just like the rest of discussed values.

Sure we can and do agree on certain references, but the thread question is about finding a better, "correct" universal value that is valid under any circumstances. At least I understood it that way. And my answer to that is, I know of none such.

 

[WhiningKhan]

Sure we can and do agree on certain references, but the thread question is about finding a better, "correct" universal value that is valid under any circumstances. At least I understood it that way. And my answer to that is, I know of none such.

And my final reply to this is, there is no need for such universal references for length and time - arbitrary base units can be selected for them, and speed of light sets their relationship. Until we prove that our current physics model is faulty in that aspect, we can trust this to be the common yardstick in universe.

 

[Davros]

You are calculating with the wrong speed there, see above.

You sure about that...................
In the picture the strobe is set to 60/sec and we can work out that it takes 30 exposures
for the non spinning ball to reach the top of its flightpath or 0.5 seconds.
We know the pinball has a diameter of 1 inch or 3 pixels and by counting the pixels we can
deduce the height of movement is 336 pixels. 3 pixels per inch = 112 inches in 0.5 seconds
or 224 inches per second.
that gives us a movement speed of 18.66 feet per second or 12.72 Miles per Hour

that still fails to explain the trajectory - in which direction(s) does that force work?

Wouldnt someone smart enough to evaluate rocket trajectories know that the force operates at right angles to the direction of spin

 

[_xxx_]

That's not what I meant. I meant the comparison between the baseball speed and pinball speed. You get the effect with the baseball due to lower specific weight and thus more influence due to air drag, but the same effect is at least a magnitude smaller with the pinball when you'd throw it with the same speed. Or vice-versa, whatever you like. Otherwise you're comparing apples to oranges.

I'd still like a direction from you, up or down then? According to your logic, reversing the rotation should produce the opposite direction of the air drag and make it ascend less and fall faster. According to my logic that will not be the case, we will see the same anomaly regardless of spin direction here. But it's just my ass-umption, may be wrong as well.

Whining: I agree with that too, but still that was the topic question, that's why we're discussing it.

 

[WhiningKhan]

Whining: I agree with that too, but still that was the topic question, that's why we're discussing it.

Yeah, and that's what I was replying to.