about Bob's article on absolute or relative time
- Thread starter Adam
- Start date
I am clearly on your side on this issue. But take care, because Stripe has focused on an aspect that he feels falsifies our side. The equations you include are correct, but note they do not specify the actual orbital path that would be observed. They only define the gravitational forces that would be at play.
Take an extreme example – assume the moon suddenly had its mass increased to be 100 times the mass of the earth. Two things would happen:
First - the moon would suddenly become nearly the center around which the earth would orbit. Thus the moon would appear to travel nearly in a straight line (or in its orbit around the sun).
Second – the earth would be drawn very close to the moon, due to the huge increase in gravitational attraction. (Actually the earth would find itself in an elongated orbit swinging close to the moon and then out, similar to periodic comets).
I will post a more comprehensive reply to Stripe dealing with these issues.
If the mass of the moon were to be reduced by a tremendous amount, what changes would be seen in the orbit of the small moon as compared to the original?
It would change.
The elliptical orbit would elongate as the attraction between the two bodies dropped by differing degrees depending on what part of the orbit the moon was in.
The earth's movement around the sun would also be affected.
I wonder if dan1el is willing to admit he was wrong? :think:
Memento Mori
New member
Hey Stripe,
Do you know what geosynchronous orbit is?
According to this, geosynchronous orbits can't exist thanks to masses majorly impacting orbits. And yet all rotating bodies have a geosynchronous orbit.
The Earth's occurs approximately 22,000 mi above sea level.
That little programs doesn't seem to take in altitudes, doesn't properly label, (not to mention the 3-body problem), etc. If you want to prove someone wrong when they've presented a mathematical proof, turning to a little astronomical generator probably isn't your best bet.
An orbit is the path the orbiting object takes. The only thing that keeps the object from traveling off in a straight line is the earth’s gravity. But I thought that one of the insights from Galileo was that the mass didn’t matter in how an object’s motion was altered by gravity (cannon ball and small rock dropped from Leaning Tower of Pisa stayed side by side as they fell).
Can you clarify?
Yes. It's an orbit that keeps an object above the same longitude on the object it is orbiting. Satellites are commonly kept in such orbits by adjusting their position. I guess one way a satellite passes its use-by date is when it is no longer able to be usefully positioned.
:squint:
What?
The earth doesn't have a geosynchronous orbit! Are you sure you've used the right word?
I don't think dan1el's maths is incorrect. It's probably just not applicable to the situation.
If you think the designer of the simulator I linked to has it wrong then take it up with him. I don't have the maths to describe why I'm correct. All I know is that, according to this simulation (and my own common sense), a change in mass will alter an orbit.
The time to impact (not the speed) of the two items falling would be the same to all but the most precise of measurements (I doubt there is any way to record the difference). If you were to drop the rock and the stone at separate times then the gravitational environment would be very slightly different each time. The rock would be attracted toward the earth a great deal and the earth would be attracted to the rock a very little. Upon dropping the cannon ball the earth would be attracted toward the cannon ball a minuscule amount more than to the rock. Thus the cannonball would hit the earth sooner. Not because it was falling faster, but because the earth was moving toward it faster.
On reflection I think dan1el's condition, "Keep the earth still", eliminated this effect and I should not have disagreed with him. But that condition means he is not answering the question.
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You're weird, phy. :chuckle:
I have often seen reference to the earth’s geosynchronous orbit. A Google search with that exact term turned up almost 300 hits, almost all confirming Memento Mori’s data. You have information that falsifies that?
Have you actually run the simulation for the moon and apple orbiting the earth?
Something specific in my post that prompts your reply?
Perhaps MM can explain what earth's geosynchronous orbit is. The only thing I know of that the earth orbits is the sun. If that is a heliosynchronous orbit I'd be surprised. :chuckle:
As for how his post has anything to do with the subject at hand I have no idea. :idunno:
Not necessary. I tested two conditions. The default setup and the satellite at mass 0.1. The orbit is noticably different with that change.
Why? I already said there are hundreds of sites that speak of it.
A couple posts ago you spoke of satellites that are in geosynchronous orbit. Is there something to be gained by this silly pretended amnesia?
So that means you used a mass of 200 for body 1 in both cases, and masses of 10 and 0.1 for body 2. Are those values near the values that would be correct for the earth-moon and the earth-apple system?
Yes, satellites have geosynchronous orbits. Does the earth?
Do you know what 'geo' means?
Who cares? The point is that a change in mass affects an orbit.
In numerous threads people express frustration with your adamant resistance to understand what is clear to others. In this case, you refuse to accept a commonly understood meaning for a term.
The point has been made. Memento Mori’s term is a common one, well understood in academia, NASA, and private industry. But for some unfathomable reason, even after telling us yourself about satellites in earth geosynchronous orbit, suddenly you choose to feign ignorance of what it means. Quote an illuminating illustration of the way you pretend to be discussing an idea.
I was just wondering if you really understood the use of the orbital tool you have referred us to several times. Do you even know how to find what values you should enter in that tool to reasonably represent the moon and apple orbits that you say are different?
From wiki: A geosynchronous orbit is an orbit around a planet or moon with an orbital period that matches the planet or moon's sidereal rotation period
For earth, the math required to find the orbit wherein a satellite will stay in geosynchronous orbit does not include a variable for the mass of the satellite.
The earth is not, itself, in a geosynchronous orbit. However, if the Sun were turning such that the earth was always looking at the same place on the sun, then the earth would have a synchronous orbit.
Much appreciated, I wasn’t aware of that before. It feels very much like these discussions are just a big game in which Stripe enjoys being contrary. I tend to hope they are a bit more serious.
Appreciate the input. Wonder why Stripe can’t (won’t?) find the same info.
S'funny. I agree with Yorzhik. I wonder if that's what MM was saying. If MM was saying that I have no idea why.
I honestly don’t know what your position is on geosynchronous orbits. It seems to flip-flop on some random schedule.
But do you really agree with the middle sentence in Yorzhik’s post? It says the mass of the satellite is not a factor for geosynchronous orbits.
Do know how to find what values you should enter in the orbital simulation tool to reasonably represent the moon and apple orbits that you say are different?