Why I disagree with static eternal universe

Sloat, Even if you factor C out of Planck's Constant its still not a dimensionless number. There are mass and time units still in the soup you are brewing. Maybe thats way you have so many problems getting results from all the math calculations.

For once in his life lyndon is being diplomatic.
Question, does Einstein's theory of general realativity require gravity to have a speed?

lyndon ashmore - bringing cosmology back down to earth.

<b>[lyndonashmore] "Question, does Einstein's theory of general realativity require gravity to have a speed?"</b>

Yes, no, maybe so (sorry, but this is just the way it is).

(The speed of light barrier in GR comes from the inherited assumptions of SR.)

===

GR (via SR) requires anything <u>that propagates</u> to have a speed of c or less.

Except, <u>of course</u>, for those (propagating) things which have a speed of c or greater. (Like the tachyon.)

(Speed is either zero, infinite or undefined for things which do not propagate.)

There is a lot of disagreement among the experts (surprise) as to whether or not gravity propagates. In part this is because these same "experts" will not say what they mean by "gravity". The gravitational potential field? The gravitational force field? Gravitational waves? Or something else? The word "gravity", without a modifier, is used carelessly to mean all of these things, depending on what the user needs at the time.

I watched over Tom's shoulder a few times when he challenged an expert on this issue. I was astonsihed to see, more than once, that the other guy seemed to not realize that the word "gravity", without any modifier, is ambiguous. On those occasions when Tom kept pressing for the other guy to be specific, the nost common response was to stop responding.

I'm serious.

Sigh,
LB

Hi Jim, the age of the universe in atomic units being a dimensionless number can throw people i admit but there's really no problems with the maths. If you must have a unit then multiply by 1 and let that number one carry the unit. 3.1415 metres, is pi times 1 metre.

Stoat,

I assume you know that the metric system is a system of units. And that the engineering system is a system of units. And I assume that you know some of the conversion factors from one system to the other. For example, 1 [inch] = 2.54 X 10^-2 [meters] is one such conversion factor that most of us have memorized. And I assume that you know where to look when you need to make a conversion that you have not memorized.

But it appears that you do not know that the atomic units system is also a system of units. Or that it has units for mass, time, length, etc just like all other systems of units. Or that it has specific conversion factors with all the other systems of units. For example, 1 [au] = 5.3 X 10^-11 [meters].

But the atomic units system is a bit confusing. 1 [au] also equals 9.1 X 10^-31 [kilograms]. And 1 [au] = 2.4 X 10^-17 [seconds]. (These numbers are known to higher precision - I'm just rounding off at one decimal.)

When you say "the mass of this particle is xx [au]", what you are really saying is that the mass of this particle is xx times the mass of an electron, because the mass of an electron is the unit of mass in the atomic units system.

When you say "the diameter of that atom is yy [au]", what you are really saying is that the diameter of that atom is yy times the radius of a hydrogen atom's electron orbit, because the radius of a hydrogen atom's electron orbit is the unit of length in the atomic units system.

When you say "the time it takes for light to travel from here to there is zz [au]", what you are really saying is that this time interval is zz times the period of a hydrogen atom's electron orbit, because the period of a hydrogen atom's electron orbit is the unit of time in the atomic units system.

===

It would be helpful if scientist had developed the habit of saying "mass-au" when talking about mass, or "length-au" when talking about distance. But they didn't. Instead they rely on context and expect others to just understand. If you don't, too bad. Professionals tend to develope their own jargon, and they tend to make it cryptic. In some ways it is like a secret handshake.

===

The point of all this is, the age of the universe in atomic units is not a dimensionless number. It is the age of the universe <u>in atomic units</u>. And you can convert between the atomic units system of units and any other system of units just by applying the proper conversion factors.

Regards,
LB

m_e c^3 / e^2 H = the age of the universe in atomic units = 1.06E 40

That is a dimensionless number. i mentioned that one, because it does the most peculiar of the dimensionless numbers.

"Our present description of the physical world is governed by empirically determined constants like the mass and charge of an electron, or the rate of expansion of the Universe, a partial list of these is..." (a list is given of the usual text book sort)

"These constants have dimensions, that is they are expressed in terms of some arbitrary chosen standard units, and so their numerical values have no significance, by changing the reference units we change the numerical value of the constants of Nature. But from these constants we can form pure numbers, independent of any reference standard, these pure numbers contain the real empirical content of the laws of physics. From the constants listed we can form the numbers..."
I. W. Roxburgh.

This is a perfectly legitimate procedure. That the ratio of the speed of gravity to that of light, is going to be a dimensionless number is good!