Naked Science Forum
On the Lighter Side => New Theories => Topic started by: opportunity on 17/12/2018 05:52:36
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Surely this is one of the most common questions today in physics.
The angle presented here needs to acknowledge "relativity physics".
Cutting to that chase, if a body approaching close to light speed has the idea of time "slow", of course relative to who or what? Atomic clocks can show that satellites travelling faster than normal objects would register a very slighter slower recording of time, yet the recording of time is via radioactive in that description of recording time. Are we suggesting radioactive decay is intrinsic to a standard for a universal measurement of time? So, what is that "universal measurement standard"...."universal"? Outside that box/experiment, our time is as our time, yet another reference depending on its speed, in the speeding box, has its own time. So where's the universal reference?
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No one should be blamed for thinking how "ho-hum" this question is.
Let this question be asked: "the speed of the planets around the sun, surely there are differences in speed of a planet's orbit around the sun?". The point here is, if one were to land on a planet travelling at a higher rate of speed around the sun than another planet's speed, and no, not time it takes to revolve around the sun, yet speed, is there a type of average of the speed of planets travelling in space around the sun, and is that a significant idea?
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is there a type of average of the speed of planets travelling in space around the sun, and is that a significant idea?
The point at which you measure time is somewhat arbitrary.
- On Earth, you may choose to measure it in Greenwich or Paris, for example.
- In Near Earth Orbit, you may choose to measure it in Star City (Russia) or Houston (USA)
- For a Mars rover, you could use Mars time or California time. But since today's rovers need daylight for safe navigation, they use Mars days (which are slightly different than Earth days)
- For a Jupiter probe, you could use time at Earth, or time at Jupiter. But since the majority of atomic clocks are based on or around the Earth, we choose to use Earth time.
- Time is relative, and there are formulas for converting time measured by one observer into time measured by another observer
- There is no "right" or "wrong", but merely convenience
- The one standard we do maintain is that light travels at "c" in a vacuum, in your frame of reference.
Are we suggesting radioactive decay is intrinsic to a standard for a universal measurement of time?
No. Relativity affects all physical (and mental) processes.
However, the effects are so subtle that they are only obvious:
- At extremely high velocities, such as you get with particle accelerators, cosmic rays or radioactive decay
- In deep gravitational wells, such as you get near neutron stars
- With extremely accurate clocks, based on very regular events such as you get with atomic clocks
You can measure some relativistic effects within the Solar System, if you use precise measurements of:
- Bending of light near the Sun (during an eclipse)
- Precession of Mercury's orbit (when viewed over centuries)
See: https://en.wikipedia.org/wiki/Tests_of_general_relativity
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So, what Newton presented with the then revolutions, and those expected masses of planets, did that assume the planets travelled at the same speed?
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I don't measure "the idea of time".
I measure time with a clock.
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Exactly.
Its not like we need to think outside the square though, right?
For instance, who has measured the weights of planets according to Newton....and even then was it assumed the planets moved at the same speed?
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assumed the planets moved at the same speed?
same speed as what?
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As you.
What do you want me to repeat?
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Time seems scary.
So, no one wants to challenge the way its used?
Time is probably bored if it has taken people.
Seriously, who's smart enough to challenge the arrow of time?
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even then was it assumed the planets moved at the same speed
In the ancient heliocentric view of the universe it was assumed that we stayed still and the planets etc moved.
So, plainly, they didn't move at the same speed as us.
Post Copernicus, we accept that all the planets, including the Earth move round the Sun.
And that requires them all to have different orbital speeds.
When Kepler looked into it
https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion
he deduced the relative speeds of the known planets and, of course, they were all different.
And with the measurement of the transit of venus
https://en.wikipedia.org/wiki/Transit_of_Venus,_1639
He was able to measure the actual speeds so, at no point in history was it "assumed the planets moved at the same speed"... "as us".
So why say it was?
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For instance, who has measured the weights of planets according to Newton?
Newton's law of gravitation allowed astronomers to weigh (estimate the relative masses) of any astronomical body with an orbiting satellite.
- It was easy to find the mass of the Sun - it has orbiting planets
- It is easy to measure the mass of Earth and Jupiter, since they have very obvious moons
- With better telescopes, it became possible to weigh Mars and Saturn (they also have moons)
However, it was only with Cavendish's laboratory experiment in 1798 that Newton's "G" was measured, and this allowed the relative masses of the Sun and planets to be turned into actual masses.
So, depending on your viewpoint (theory or practice), the answer could be "Newton" or "Cavendish".
See: https://en.wikipedia.org/wiki/Cavendish_experiment
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It's also fair to say that NASA measured the mass of the moon.
If their value for the mass of the moon had been wrong, they wouldn't have been able to land on it.
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For instance, who has measured the weights of planets according to Newton?
Newton's law of gravitation allowed astronomers to weigh (estimate the relative masses) of any astronomical body with an orbiting satellite.
- It was easy to find the mass of the Sun - it has orbiting planets
- It is easy to measure the mass of Earth and Jupiter, since they have very obvious moons
- With better telescopes, it became possible to weigh Mars and Saturn (they also have moons)
However, it was only with Cavendish's laboratory experiment in 1798 that Newton's "G" was measured, and this allowed the relative masses of the Sun and planets to be turned into actual masses.
So, depending on your viewpoint (theory or practice), the answer could be "Newton" or "Cavendish".
See: https://en.wikipedia.org/wiki/Cavendish_experiment
Yes, quite correct. Yet did Newton take the movement of the planets through space (not the time it takes for them to revolve around the sun) as a constant in order to determine their masses from their calculated elliptical orbits? Who or what first calculated the respective "speeds" of the planets?
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The real question is if Newton knew the planets were a certain distance from the sun, a certain exact distance. If he did, he would know that the planets have a different speed of movement through space (and not solar rotation). But he didn't (or did he?). So, the question is, did he assume with his initial calculations that they move at the same speed through space?
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even then was it assumed the planets moved at the same speed
In the ancient heliocentric view of the universe it was assumed that we stayed still and the planets etc moved.
So, plainly, they didn't move at the same speed as us.
Post Copernicus, we accept that all the planets, including the Earth move round the Sun.
And that requires them all to have different orbital speeds.
When Kepler looked into it
https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion
he deduced the relative speeds of the known planets and, of course, they were all different.
And with the measurement of the transit of venus
https://en.wikipedia.org/wiki/Transit_of_Venus,_1639
He was able to measure the actual speeds so, at no point in history was it "assumed the planets moved at the same speed"... "as us".
So why say it was?
This is the problem. Orbital speed is not "speed through space" as you refer to it re. Kepler. The solar orbital time for each planet is different, of course, yet their speed through space according to contemporary calculations decreases the more we move from the sun (http://planetfacts.org/orbital-speed-of-planets-in-order/). The link is ambiguous with your description of "orbital speed" and Kepler). The question is how actual planetary speed is calculated.
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Take the opposite approach. What best explains the virtual dynamic that incorporates the elusive nature of time. What quantum aspect decoheres time to make it .tangible? The hawking's radiation theory may offer an insight. The three interpretations of this theory support virtual particles. A BH's dissipation is incumbent on the creation of virtual particles. The BH being possibly the largest repository of time makes it a far greater and more precise instrument to measure time accurately. Atomic radiation is sufficient but it's half life is minuscule to that of a BH's life time.
So, according to Hawkings the creation of virtual particles pairs are responsible for the eventual evaporation of the BH. This propagated seed of destruction provides a measurable lifetime, which in turn provides a reliable time chronology, with a higher degree of accuracy than atomic radioactivity. I understand that what is proposed is beyond feasible but the question was in regards to what would be a more descriptive understanding of a time increment then a radioactive clock. The production of virtual particles is no doubt the smallest increment of time conceived to date.
"Physical insight into the process may be gained by imagining that particle–antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles.[9] As the particle–antiparticle pair was produced by the black hole's gravitational energy, the escape of one of the particles lowers the mass of the black hole.[10]
An alternative view of the process is that vacuum fluctuations cause a particle–antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole while the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). This causes the black hole to lose mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. In another model, the process is a quantum tunnelling effect, whereby particle–antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon.[9]"
Another possibility that may have practical applications when atomic clocks are not feasible to accurately measure time differentials. Measuring motions within molecular atoms using absolute zero temperature variables to clock motion activity.
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The question is how actual planetary speed is calculated.
Same as always
Distance divided by time.
For example the Earth's orbital speed round the Sun is about 30 km/s. That's small compared to C so we can ignore relativistic effects (or- if you like, you can calculate them)
It's in free fall, so gravitational effects are small or zero.
We know how far away the Sun is (About 150 million km).
So the circumference of the path is 2 * pi times that (940 Gm)
And we know how long it takes to go round the Sun- a year.
About 31 million seconds
So the speed is 940,000,000,000 metres divided by 31,000,000 seconds.
About 30 km/s
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Today there is no doubt, absolutely no doubt, about the speed of the planets; the Voyager crafts allow us to measure the time it takes to ping an event at each planetary milestone achievement. From that ping time the distances can be measured, and thus speed in knowing solar revolution time. A question is how Newton calculated the distances of the planets from the sun and masses, and of course thus speed; the solar orbital time revolution of the planets was known, that is clear. Their distances from the sun and their speed was the tricky bit. Just to get things clear, who knows how Newton did that?
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A question is how Newton calculated the distances of the planets from the sun and masses, and of course thus speed;
The distances of the planets was found by triangulation.
Newton's work is in the public domain now.
Why not find out how he did stuff by reading what he did?
Incidentally, he didn't calculate the masses except in relative terms.
That had to wait until someone found the mass of the Earth.
https://en.wikipedia.org/wiki/Cavendish_experiment
But it doesn't affect the measurements of the speeds.
Just to get things clear, who knows how Newton did that?
I'm not sure he needed to- the distances may have been worked out before his time.
Certainly, the Earth- Sun distance was known- at least approximately- to the Ancients.
https://en.wikipedia.org/wiki/Astronomical_unit
Why do you think this is some sort of mystery
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Bored chemist, I agree, yet I have said the same. Don't worry about that. Go beyond.
Have you read the Principia?
Do you know the statements? The issue here is how the solar revolution and triangulated distances took either distance or speed.
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Once you know the distance from the Sun to the Earth you can use the orbit of the Earth as a baseline for triangulation (wrt the so called "fixed stars".
That lets you know the distance to the planets.
That lets you know the orbital radii .
You can watch them go round + find out their orbital period.
And then you can do essentially the same bit of arithmetic as I did for the Earth.
None of this is complicated- it's high school maths.Have you read the Principia?
No.
It's in Latin.
But I might find a translation to read over Xmas.
Do you know the statements?
What statements?
Please try to write stuff that makes sense. I can't read your mind.The issue here is how the solar revolution and triangulated distances took either distance or speed.
You seem to think it is an "either/ or" thing.
The measurements give you distance and speed.
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The Principia is an interesting read, and no it wasn't in Latin when I took a look, yet it was written in latin.
The following is a good summary of what I was looking for:
https://www.quora.com/How-did-Newton-calculate-the-distance-between-the-Earth-and-the-Sun-to-calculate-the-mass-of-the-Earth
What I am still looking for is that although Newton the relative distances and speeds, and calculated masses thereabouts of the planets, what did he put the different speeds of the planets down to?