The City College CUNY Class: ASTR 30500 Methods in Astronomy

Centripedal force is not to be confused with centrifugal force.

Orbital decay caused by all kinds of factors. Professor mentioned Einstein's explanation of such by orbital direction change: Orbital Precession. However, I'm unclear as to if this is the cause of the decay, or that they share the same cause.

Side note:
Retrograde orbit: orbiting in opposite direction. As opposed to synchronous orbit.

I still suspect inverse square laws have to do with area of sphere.

Question: How did Kiefer convert G constant to a different unit? (6.67 x 10-11 N m^2/kg^2  or  3.31 x 10-11 ft^2/ lb)

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4 Responses to The City College CUNY Class: ASTR 30500 Methods in Astronomy

  1. timlyg says:

    I found an incredibly thorough text on astronomical optics.
    http://www.handprint.com/ASTRO/ae3.html

  2. timlyg says:

    I believe the Kiefer Constant (Gravitational Constant in US unit) is wrong. It should have been around 106.7 x 10^-11 ft^3/(s^2lb). Or better = around 1 x 10^-9 ft^3/(s^2lb). The Kiefer-Law Constant. But it has been found (1.068846 x 10-9 ft3 lbm-1 s-2)before.

    The key problem is that Dr. Kiefer did not differentiate pound-mass with pound-force (32.174049ftlbm/s2) which yields his result for conversion of Newton in respect of lbm and conversion of kg in respect lbs. Being treated all as lb, he cancelled them off, giving not only the wrong number, but the wrong units as well.

    I do fancy using FPS/US Customary System in this case, even though it is rarely used, because of easy memorization (1 x 10^-9). However, I think due to the fact that lbf (pound-force) is originally an Earth-based unit (involves Earth's gravitational force), it could draw confusion in the scale of the Universe.

    It is interesting that I arrive to this correction via calculus II's Integration Application in Work (Physics), when I contemplated the units for Force (N=kg*m/s^2 and weight=lb), where lb in this case is not mass. kg is not weight, but mass, just as lbm is mass, lbf is weight.

    On the side note: Some say 1lbm = 1lbf on Earth's surface gravitational force. Technically, it is incorrect to say that 1lbm equals 1lbf, but 1lbm weighs 1lbf under standard Earth's gravity.
    . From my own investigation, at the same link above, this has to do with the conversion that involves slug: 1 slug = 32.17405lbm while 1 lbf = 1 slug*ft/s^2, causing the conversion of unit between lbf & lbm accordingly.
    So from this, I conclude that the (double standard kg/lb) weight scale we use on Earth will yield accurate lb (pound force) result on other planet since kg only tells mass and therefore a different mass result the wrong answer for mass on another planet. Unless we strike down kg and relabel it as N (Newton). However, when asked, I would say our weight scales use lbm (not lbf, though appears to be the same and some say lbf) as lb, because we have kg as mass, so lb must be in mass unit (lbm) and not force unit (lbf), it is convenient on Earth since 1 lbm weighs 1lbf.

  3. timlyg says:

    I tried...I give up. Kiefer's answer was to just forget about lbm (it's for engineers, chemists, he said). I am certain he's wrong, but I'll entertain him with his constant in his class. I've come to experience the term: You can't teach an old dog new tricks. I still don't believe it though, time will tell.

  4. timlyg says:

    Inflation of the Universe / Cosmic inflation / Cosmological inflation

    I had misunderstood this as an explosive type of expansion. It is as the balloon illustration, an expansion of all space, not just space between two large objects.

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