about Bob's article on absolute or relative time

Newman

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What is the difference between time as measured by a clock, and time as sensed by an observer?
Don't know where you are going with this. Most clocks are subject to mechanical forces and relativity. Human perception and aging are only subject to relativity, outside of biology.

OK, then what would happen if the earth were to stop rotating? Would the two clocks then keep identical time?
Don't know where you are going with this, either. I don't think they would keep EXACTLY identical time, due to differences in gravity affecting the mechanics of the clock. But, I mean, it depends on how the clock is constructed, I guess.
 

Stripe

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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.

Yes, I agree. But the consideration of the mass is probably hidden by the consideration for velocity (I don't know the equation Y. is referring to). To attain the velocity required to set a geosynchronous orbit requires an amount of energy depending on the mass of the satellite, right?

If the mass of the satellite in a geosynchronous orbit were to magically change to that of the moon its orbit would also change.
 

ThePhy

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But the consideration of the mass is probably hidden by the consideration for velocity (I don't know the equation Y. is referring to). To attain the velocity required to set a geosynchronous orbit requires an amount of energy depending on the mass of the satellite, right?
I know you object when I point out your lack of knowledge in a subject, but your first statement is wrong, and your second is irrelevant.
If the mass of the satellite in a geosynchronous orbit were to magically change to that of the moon its orbit would also change.
That’s contradicts what Yorzhik said. One post ago you agreed with what he said - that the mass does not enter into the equation.

And (3rd time): 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?
 

ThePhy

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Don't know where you are going with this. Most clocks are subject to mechanical forces and relativity. Human perception and aging are only subject to relativity, outside of biology.
If something in relativity causes a clock to run slower, why wouldn’t that same something make the biological process in a human do likewise? You said gravity would not affect time for an observer. Specifically what determines “time for an observer” if it is immune from time dilation?
Don't know where you are going with this, either. I don't think they would keep EXACTLY identical time, due to differences in gravity affecting the mechanics of the clock. But, I mean, it depends on how the clock is constructed, I guess.
You said the mountaintop clock would have to go faster due to it having to go farther. I am proposing eliminating that to see what happens if the only difference between the two clocks is gravity. And as for the mechanics of the clock, presume the clock heartbeat is dependent on a nuclear process inside the atom. No friction to deal with, no gears, or springs, or such to cause mechanical problems.
 

Stripe

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I know you object when I point out your lack of knowledge in a subject, but your first statement is wrong, and your second is irrelevant.

That's nice, Phy. Could you tell us how and why what I said is incorrect and irrelevant?

That’s contradicts what Yorzhik said. One post ago you agreed with what he said - that the mass does not enter into the equation.

Mass probably doesn't enter into the equation he provided. It would enter into another equation that would also have to be made to get a satellite into orbit. And you're discussing very irrelevant things. It does not matter one bit to this discussion whether Yorzhik and I agree or not.
 

Memento Mori

New member
I brought in geosynchronous orbits to show you that mass isn't considered in many orbits which would include the moon-apple switch, Stripe. If I were to replace an apple with a satellite in geosynchronous orbit with zero change, they why does expanding the belt to the moon suddenly matter with regard to mass?

Also, where did this tangent about orbits occur during relativity discussions?
 

ThePhy

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Could you tell us how and why what I said is incorrect and irrelevant?
Incorrect because synchronous orbits are independent of mass. There are a whole slew of satellites in earth geosynchronous orbit right now, rather closely spaced. They have a range of sizes, yet they all orbit at the same height and speed. Mass isn’t a factor when a satellite is in geosynchronous orbit.

Irrelevant because how a satellite gets put in geosynchronous orbit has no bearing on it’s orbital characteristics. Maybe angels carry it up and throw it into orbit.
Mass probably doesn't enter into the equation he provided. It would enter into another equation that would also have to be made to get a satellite into orbit.
Launching and orbital insertion is not the subject. The effects of differing mass once in geosynchronous orbit is the subject.
And you're discussing very irrelevant things. It does not matter one bit to this discussion whether Yorzhik and I agree or not.
It matters when you say you agree with Yorzhik, and he said mass is not a factor.

And (4th time): 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?
 

Memento Mori

New member
And (4th time): 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?

That simulation seems more bent towards smaller objects. I tried putting in ridiculous sizes to try to simulate it and the program seemed to flip out... I bet it got a negative number or something.

Of course, not adding units kind of destroys credibility...
 

Stripe

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I brought in geosynchronous orbits to show you that mass isn't considered in many orbits which would include the moon-apple switch, Stripe. If I were to replace an apple with a satellite in geosynchronous orbit with zero change, they why does expanding the belt to the moon suddenly matter with regard to mass?

Dude, you need to proofread. I can hardly make you out.

Your point is a re-statement of the original disagreement. I still disagree. Changing a satellite to an apple will change its orbit. All I have to back myself up at the moment is my common sense and the link I provided. If you're going to reject the link then I don't have much left :D

Perhaps you could find a similar program (there are a number out there) that we could use instead.

Also, where did this tangent about orbits occur during relativity discussions?

I struggle to recall myself. I'm sure its a perfectly harmless little side issue that means little at all. :chuckle:

Incorrect because synchronous orbits are independent of mass. There are a whole slew of satellites in earth geosynchronous orbit right now, rather closely spaced. They have a range of sizes, yet they all orbit at the same height and speed. Mass isn’t a factor when a satellite is in geosynchronous orbit.

Once the satellites are put into place their mass is not a factor. Getting them into that place requires a differing amount of energy depending on their mass. Change the mass of one suddenly and its velocity will change to compensate (maintaining the orbit). Change the mass without changing the velocity and something needs to give. This is grade school stuff, Phy.

Irrelevant because how a satellite gets put in geosynchronous orbit has no bearing on it’s orbital characteristics. Maybe angels carry it up and throw it into orbit.

Perhaps you remember a little principle called (IIRC) "Conservation of Energy". :think:

You're right - the means by which a satellite is put into orbit is irrelevant. The fact is though that the energy put in is conserved in the satellite's velocity. Two satellites travelling at the same speed with different masses have different amounts of energy. Reducing the mass of one without altering its velocity means it has lost energy. That lost energy needs to go somewhere .. where will the energy go, Phy?

Launching and orbital insertion is not the subject. The effects of differing mass once in geosynchronous orbit is the subject.

A change in mass will not have no effect. What effect will a change in mass have, Phy?

It matters when you say you agree with Yorzhik, and he said mass is not a factor.

He clearly specified when and why it was not a factor. He did not refer to the question we are pondering. I am perfectly justified in agreeing with what he said and continuing to disagree with you.

Looks like you're in desperate search of anything to hide the fact that you're wrong. If you're right just show me how I'm wrong and I'll happily concede. But as it stands I have my common sense and an independent orbital modeller backing me up. You have a lot of restatements, arm waving and mud stirring, 6 months of inactivity and a couple of inarticulate atheists to back you up.
 

ThePhy

New member
I struggle to recall myself. I'm sure its a perfectly harmless little side issue that means little at all.
Christian memories are such unreliable things. This orbit question is something that Stripe felt he could draw my blood on. He is the one who was interested enough that he pinged me on it several times over the past few months. But now, suddenly, he considers it just a “harmless little side issue”. I wonder why the change of heart?
Once the satellites are put into place their mass is not a factor. Getting them into that place requires a differing amount of energy depending on their mass. Change the mass of one suddenly and its velocity will change to compensate (maintaining the orbit). Change the mass without changing the velocity and something needs to give. This is grade school stuff, Phy.
Maybe you failed grade school. You should have been a student of a physics Prof that I had years ago. He would intentionally provide excess information in test problems. Then he analyzed not only our answers, but how we got them. If we had mastered the material, we would use only the information that was necessary. Those students that were a bit more shaky in their understanding sometimes got the right answer, but it was by a roundabout backdoor method using the unneeded data. Their grades were lowered since they had demonstrated they did not recognize what was pertinent to the problem, and what was not.

Now listen carefully this time, Grasshopper. We are discussing how an apple’s orbit compares with the moon’s.

We start with the moon in orbit, going around and around and around the earth. We figure out where it will be when. We are not concerned with how it got in that orbit. Maybe it condensed directly out of a cloud of space dust. Maybe it was ejected from the earth in some ancient impact. Maybe it was captured as it wandered by. Maybe God thought that would be a neato orbit to put it in. Maybe it is a piece of alien trash that they left behind. Doesn’t matter.

Now I put in a call to Darth Vader Intergalactic Demolition. I promise to deliver ten clones of Carrie Fisher if they will use their death star to vaporize the moon. Zap, it is gone. A bit of dust, a flash of light, a disturbance in Yoda’s “Force”, but no more moon.

Next I hop a plane to Fort Wayne, Indiana, and then on to Moscow. In Fort Wayne I pick a really nice apple from one of Johnny Appleseed’s last trees. In Moscow I pay to have the apple put in orbit – in the same place with the same speed that the moon would have had if it hadn’t been vaporized. I leave it purely up to the Russians as to how they get it up there. They might send it up on the next ICBM test. Maybe they put it in the next cosmonaut’s lunch box. Maybe they make the world’s biggest slingshot. Maybe they take it out past Pluto first. I don’t care, and don’t even want to know. I just want a phone call telling me the apple is in orbit.

Then I watch that apple go around and around and around the earth. I am interested in watching to see if the apple maintains the same orbit the moon had been in for so long.

The one thing we are not doing in any way is transferring the energy from the massive moon to that poor defenseless little apple. Got it?

Looks like you're in desperate search of anything to hide the fact that you're wrong. If you're right just show me how I'm wrong and I'll happily concede. But as it stands I have my common sense and an independent orbital modeller backing me up. You have a lot of restatements, arm waving and mud stirring, 6 months of inactivity and a couple of inarticulate atheists to back you up.

Yup, the common sense of someone who has a tenuous understanding of physics, and an orbital modeling tool that you are assiduously avoiding answering a simple question about how to meaningfully set it up.

Let me hold your hand a bit on the use of your tool. Some good values for seeing what the moon’s orbit looks like:

body 1 (earth)
mass = 100
x and y Positions = 0, and x and y velocities = 0

body 2 (moon)
mass = 1.2
x Position = 160
y Position = 0
x velocity = 0
y velocity = 80

Slide the accuracy control fully to “accurate”.

This will give an orbit that closely scales to the moon’s orbit. Stripe should make a screen capture of that for later use.

Now let’s go to the apple orbit. The only change is the mass of body 2 will be reduced to only a smidgeon of what it was. We will reduce it to less than a billionth of a billionth the mass the moon had. According to Stripe, eliminating most of this mass will show the orbit is changed. In the interactive tool the “body 2” mass field will only display 5 digits, but in fact the value entered there can use many more digits. We will use a small “apple”, say 0.1 kg. When this value is scaled to the same ratio as the earth, in the interactive tool the apple mass will be 0.0000000000000000000000002 (24 zeroes after the decimal, then the 2). (Even if I were off a few zeroes, we have still reduced the “moon” mass by multiples of millions of times.)

Now Stripe, run the simulation with the “apple moon” in place. Best if you do another screen capture, so you can compare it with the one showing the orbit of the regular moon. Overlay the two orbits, and tell us how much they differ.

There are some other ramifications of that tool, but let’ start with the above.

And finally, I must apologize to Stripe. My mother always reprimanded me when I played with my food. I shouldn’t play with you, Stripe. Sorry.
 

GuySmiley

New member
If you magically change an apple in orbit to the moon, the orbit will remain the same*, assuming this magical process also kept the velocity the same, ignoring conservation of momentum.

If our magical process kept conservation of momentum, of course the velocity would change drastically, and drastically altering the orbit.

*ignoring perturbing effects like solar wind, drag, or J2 which may affect an apple differently than the moon. At geosynch altitude these effects would be tiny, really tiny.
 

GuySmiley

New member
Consider all the satellites at Geosynchronous orbit (more accurately Geostationary is what we mean). These satellites all orbit above the equator at the same rate the earth is rotating. They all have the same orbit, but they are all not the same mass. If mass had an effect, they would drift away from their positions.*

*see the star in my previous post.
 

fool

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Hall of Fame
Maybe they make the world’s biggest slingshot.

This would not work if they fired the slingshot from the Earth's surface.
A slingshot imparts all it's energy at the release, so the apple would be going at escape velocity at the launch, atmospheric friction would vaporize the apple and you would wind up with a puff of apple plasma and perhaps some scorched seeds just down range of the launch site.

Perhaps lasers could be fired ahead of the apple to super heat the atmosphere into exploding and the apple could travel thru the resultant cavitation?
 

Memento Mori

New member
Dude, you need to proofread. I can hardly make you out.

Your point is a re-statement of the original disagreement. I still disagree. Changing a satellite to an apple will change its orbit. All I have to back myself up at the moment is my common sense and the link I provided. If you're going to reject the link then I don't have much left :D

Sorry. I was in a rush... It was finals week.

Anyhow, yes. But I'm using a new example. Geosynchronous orbits are not dependent on mass. Just as all other orbits. Geosynchs are not a special case except that their period matches the period of rotation of the planet (in this case).

RE: The Gravity simulation

Do you just hate math or do you not understand it? You've been shown repeatedly a plethora of mathematical equations which you deny. You're willing to deny centuries of mathematical proofs for one simple simulation which is very poorly constructed (for use in giant systems).
 

Stripe

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Christian memories are such unreliable things. This orbit question is something that Stripe felt he could draw my blood on. He is the one who was interested enough that he pinged me on it several times over the past few months. But now, suddenly, he considers it just a “harmless little side issue”. I wonder why the change of heart?

:rotfl:

That is not an explanation for this tangent about orbits during a relativity discussion. You need to learn to read, Phy.

Maybe you failed grade school.

I didn't even go to grade school. :D

This will give an orbit that closely scales to the moon’s orbit. Stripe should make a screen capture of that for later use.

Now Stripe, run the simulation with the “apple moon” in place. Best if you do another screen capture, so you can compare it with the one showing the orbit of the regular moon. Overlay the two orbits, and tell us how much they differ.

Why can't you do it for yourself? :idunno:
 

Stripe

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Do you just hate math or do you not understand it? You've been shown repeatedly a plethora of mathematical equations which you deny. You're willing to deny centuries of mathematical proofs for one simple simulation which is very poorly constructed (for use in giant systems).

OK .. if the simulation is broken then perhaps I'm wrong. :)
 

Stripe

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If you magically change an apple in orbit to the moon, the orbit will remain the same*, assuming this magical process also kept the velocity the same, ignoring conservation of momentum.

I don't agree. I can't argue with the maths because I'm sure you all know it better than I do, but I cannot fathom how the orbit would not be affected.

If you change an object's mass but maintain its velocity you altered the energy distribution in the scenario. Where does that energy come from or go to?
 

Stripe

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Consider all the satellites at Geosynchronous orbit (more accurately Geostationary is what we mean). These satellites all orbit above the equator at the same rate the earth is rotating. They all have the same orbit, but they are all not the same mass. If mass had an effect, they would drift away from their positions.

I think the satellite discussion has confused the issue too much for me. I agree with what you've said here, but it doesn't explain the disagreement for me.
 

ThePhy

New member
Why can't you do it for yourself? :idunno:
My mistake for not being clearer. When I said the “only change is the mass of body 2” I was referring to the only change needed from the values I had just itemized (body 1 mass of 100, zeros for body 1 speeds and positions, etc.

Put the miniscule body 2 mass in that setup and do the comparision.
 
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