Dont tell anyone, but I think the earth is flat.

[hpeer]

Originally Posted by deblen

Yes!! You must visit Fogo Island & see for yourself!
https://www.tripadvisor.ca/LocationP..._Labrador.html

Cheers/ Len

Been there done that, Brimstone Head, on my way back from the other side I Guess.

[Snowpetrel]

Originally Posted by adoxograph

Gravity - strictly speaking - is not a force. It is the consequence of the curvature of spacetime, which is not flat because of an uneven distribution of mass and energy.

I guess I'm boring you to death right now ...

If spacetime is not flat but curved, prehaps a curve is actually flat? With enough maths, and enough dimensions almost anything seems possible, prehaps even a flat earth...

[adoxograph]

Originally Posted by sailorchic34

Myself I think it could still be a force, though I do understand about Al's spacetime curvy thingy. It could be that way from a thought experiment. But it does not have to be that way. Sort of still open to speculation now isn't it.

Think quantum gravity. Do you really think a quark deflects spacetime. If gravity did not exist at the quantum level, how did the universe as we know it today form. Quantum Gravity and Unified Theories | Max Planck Institute for Gravitational Physics (Albert Einstein Institute)

Well, we were talking about bricks and needles and planets.

If you unify Quantum Gravity you get the Nobel price for sure. Our understanding of Quantum Gravity is very limited (comparable with Newtons understanding of Gravity. It works - kind of - but is not really right). At quantum level we imagine gravitons exchanging gravitational force like photons work for the electromagnetic force. We do this, knowing it can't be right because this is limited to the magnitude of one Planck length.

The "spacetime thingy" is not really open to speculation (ok in science everything is open to speculation), your GPS for example needs to put spacetime curvature into consideration in order to work. GPS clocks need a precision of 20-30 nanoseconds to give the required accuracy at ground level. However, because the satellites are in relative motion to ground based observers, corrections must be made due to the effects of special relativity. The satellite clocks fall behind by about 7 microseconds per day.

Additionally, as the curvature of spacetime is less that that at the Earth’s surface, the satellite clocks will also tick faster than ground based clocks. In this case, the effects of General Relativity mean that GPS satellites should go ahead by around 44 microseconds per day.

The combination of special and general relativity effects means that satellites clocks will tick faster than identical Earth based clocks by 45-7 = 38 microseconds (or 38,000 nanoseconds) per day. If not compensated they would accumulate an error of 10km per day and soon be utterly useless.

[sailorchic34]

Originally Posted by adoxograph

Well, we were talking about bricks and needles and planets.

Additionally, as the curvature of spacetime is less that that at the Earth’s surface, the satellite clocks will also tick faster than ground based clocks. In this case, the effects of General Relativity mean that GPS satellites should go ahead by around 44 microseconds per day.

The combination of special and general relativity effects means that satellites clocks will tick faster than identical Earth based clocks by 45-7 = 38 microseconds (or 38,000 nanoseconds) per day. If not compensated they would accumulate an error of 10km per day and soon be utterly useless.

The thing is the spacetime deflection caused by mass that may be the cause or action of gravity, does NOT translate to the quantum level. Yet in the end we all exist at a quantum level.

It is obvious that gravity is felt further then a Planck length at the quantum level as we exist and the universe is not just a big mess of quantum partials floating in the cosmos. As it's shown that quantum level particles do not deflect space time, Or rather that the math does not extend to the quantum level, we may not have all the answers yet.

I think your confusing gravity with time dilation at speed. Not really a gravity thingy at all. But due to relative speed of orbit of GPS satellites which orbit at 8600 ish mph and relation to surface based GPS receiver that only moves from roughly +/-1000 mph with a person sitting in a chair to +/-3400 mph (sr71 blackbird) in relation to the satellites.

The difference in time is not gravity based but relative velocity and the very slight time dilation effect due to the higher relative velocity of the GPS satellites. Yes there should be is a slight mass change too, but I'm not sure that effects gravity or space time deflection to any measurable degree.

It all depends on your reference frame. As Al said it's all relative.

[Blue Crab]

So it is flat after all?

[adoxograph]

Originally Posted by sailorchic34

The thing is the spacetime deflection

It is not deflection it is a change in geometry

Originally Posted by sailorchic34

caused by mass that may be the cause or action of gravity

well, in this context I don't understand what you mean by cause or action.

Maybe you meant mass as well as acceleration changes the geometry of spacetime?

Originally Posted by sailorchic34

, does NOT translate to the quantum level. Yet in the end we all exist at a quantum level.

Now you get philosophical. This is out of my expertise, but saying we all exist at a quantum level could lead to the conclusion we do not exist at all. (There are weird things happening in a quantum vacuum).

Originally Posted by sailorchic34

It is obvious that gravity is felt further then a Planck length

Is it? As it is it impossible to determine the difference between two locations less than one Planck length apart, nothing is obvious at this level. Remember Schrödingers Cat?

You yourself said before that at quantum level Gravity is still an unknown. Now you are saying it is still the same gravity?

Originally Posted by sailorchic34

at the quantum level as we exist and the universe is not just a big mess of quantum partials floating in the cosmos. As it's shown that quantum level particles do not deflect space time,

Sorry you lost me completely here. What do you mean by "Quantum Particle" or "Quantum Level Particles". And what do you mean by saying they don't deflect spacetime? Are you saying a photon is not following the geodesic of the curved spacetime? Sorry I can't follow your train of thought here.

Originally Posted by sailorchic34

Or rather that the math does not extend to the quantum level,

It does not? Do David Hilbert and Werner Heisenberg know about this? Could you elaborate please what you mean by that?

Originally Posted by sailorchic34

we may not have all the answers yet.

Yes and that makes it fascinating!

Originally Posted by sailorchic34

I think your confusing gravity with time dilation at speed.

No I don't. Einsteins General Relativity deals with time dilation and lengths contraction caused by gravity or better curvature in spacetime. He predicted over 100 years ago a difference in the passage of proper time at different positions as described by a metric tensor of spacetime and this was demonstrated by the Pound–Rebka experiment in 1959.

Originally Posted by sailorchic34

Not really a gravity thingy at all. But due to relative speed of orbit of GPS satellites which orbit at 8600 ish mph and relation to surface based GPS receiver that only moves from roughly +/-1000 mph with a person sitting in a chair to +/-3400 mph (sr71 blackbird) in relation to the satellites.

The difference in time is not gravity based but relative velocity and the very slight time dilation effect due to the higher relative velocity of the GPS satellites.

Yes and no. Read my above post. There are two components in the time correction of the GPS satellites. A) velocity, B) Gravity. As you go further out in the orbit, general relativity exerts more influence and the shift becomes positive. This is because general relativity dictates that the clock will run slightly slower since the satellite is further out of the gravity well. So the frequency shift depicted just means how much the time of the clock on the satellite has to be compensated for to match the times on Earth. Btw, further out is "easier" because the orbits are more predictable.

Its actually quite simple. Following I used a Lorentz transformation and a Taylor series. I spare you the details as this forum does not have an equation editor:


Gravitational Time Dilation for GPS
Light speed c 3.0000000000E+08
G constant G 6.6730000000E-11
Earth Mass M 5.9700000000E+24
Earth Orbit Radius Re 6.3710000000E+06
Sat Orbit radius Rs 2.6371000000E+07

at Re factor is T (proper) 9.9999999931E-01 secs
at Rs factor is T (proper) 9.9999999983E-01 secs
Delta T 5.2692494812E-10
Loss in day 4.5526316E-05 secs
=45 Microseconds

So the clocks are slower by 7 microseconds due to Special Relativity (SR) due to its velocity and faster by 45 MIcroseconds due to the difference in curverture of spacetime (aka Gravity) as predicted by General Relativity (GR)

You see Gravity plays a major role in us finding our position in the middle of the night on a vast ocean with the help of satellites.

Originally Posted by sailorchic34

and so the Sat clock are set to run slower by 38 ms per day to enable synch with terrestrial clocks

As I explained above this is the result of impact of velocity and gravity

Originally Posted by sailorchic34

Yes there should be is a slight mass change too, but I'm not sure that effects gravity or space time deflection to any measurable degree.

Here you are absolutely right the invariant mass should increase with velocity. Another prediction of SR. However at non-relativistic speeds this change is miniscule.

Originally Posted by sailorchic34

It all depends on your reference frame. As Al said it's all relative.

No it does not. Lorenz transformations work both ways. It does not matter what you consider to be your rest frame, the results are the same. That's the beauty of Einsteins work.

[svmariane]

Originally Posted by Blue Crab

So it is flat after all?

Hmmmm... Hexagon-Tubular, methinks. Still refining the mathematical calculations so the computer generated imagery is a bit rough. We're somewhere in the middle/alongside of the tube's inner edge so that's why we can see the stars. It's also why we can't go sailing off the edge. {The sailing reference is to satisfy the needs of a sailing forum.}

[adoxograph]

@sailorchic34

If you interested how all of this works in detail I found a nice paper by Neil Ashby explaining all of this without the lingo. I think you might be interested in page 11 part B:

https://www.aapt.org/doorway/TGRU/ar...hbyarticle.pdf

PS: I never thought I would have a discussion like this on CF. I'm really enjoying this but I hope I did not come across as a smartass nerd.

[sailorchic34]

Originally Posted by adoxograph

@sailorchic34

If you interested how all of this works in detail I found a nice paper by Neil Ashby explaining all of this without the lingo. I think you might be interested in page 11 part B:

https://www.aapt.org/doorway/TGRU/ar...hbyarticle.pdf

PS: I never thought I would have a discussion like this on CF. I'm really enjoying this but I hope I did not come across as a smartass nerd.

I stand corrected. There is a gravitation frequency shift. Oddly pretty cool.

[Deep Blue Blues]

Originally Posted by jongleur

As someone said, "That's silly. It's
turtles all the way down."

It IS turtles all the way down!

[Deep Blue Blues]

Big ones.

[Deep Blue Blues]

Let's wrap this epic flat round convex gel coated quantum tater tot extravaganza up soon because our new topic of discussion will be on how we will never know if we were successful in making time travel possible because of alternate universe's we create the instant we traveled forward or backwards through time!

That or 10 ways that prove Hillary is the devil.

[StuM]

Originally Posted by adoxograph

@sailorchic34

If you interested how all of this works in detail I found a nice paper by Neil Ashby explaining all of this without the lingo. I think you might be interested in page 11 part B:

https://www.aapt.org/doorway/TGRU/ar...hbyarticle.pdf

PS: I never thought I would have a discussion like this on CF. I'm really enjoying this but I hope I did not come across as a smartass nerd.

And for everyone else:
Short Words to Explain Relativity
and
The Space Doctor’s Big Idea - The New Yorker

[valhalla360]

Originally Posted by StuM

The earth's volume is approximately 1.083e24 liters.

Assume that you pump 1 liter each second.
Before you start to pressurize it, just inflating it will take 34,000 trillion years.

More importantly, why have we defined a gram as the mass of water contained in a cube one - one hundred millionth of the distance from the mythical equator to the pole and liter as the volume of a cube one- ten millionth of the distance from the mystical equator to the pole?

So many things wrong with that. Next you will tell me there is a barber pole with a toy manufacturing plant polluting the arctic air run by small people.

[Deep Blue Blues]

Fascinating.. Tell me more about this arctic toy shop...