Tests of General Relativity

[Boydstun 181]

Gravity Probe B

A drag-free satellite equipped with exquisite monitoring of spin axis of superconducting gyroscopes brings confirmation of two effects of GR.

More on final results of the experiment will be posted soon here at the Stanford site.

Edited May 5, 2011 by Boydstun

[ToyoHabu 3]

This seams to be based on space and time being an existent, right? Is that a valid? Or is it more a matter of convenience like in aerodynamics where the air or the aircraft is assumed to be moving.

[Grames 332]

Space and time are definitely existents. An existent is a much broader concept than entity, and can refer to a thing, an attribute, a relationship, or an action. A non-scientific understanding of space and time refers to relationships between the directly perceived entities given by our senses, and that is still an existent.

(Extending 'existent' to encompass relationships is done by Rand in the appendix to ITOE 2nd ed pg. 241, where she is asked to distinguish between "fact" and "existent".)

So-called "empty space" has other measurable attributes such as vacuum permittivity and vacuum permeability.

There is no such thing as nothingness. Existence, the universe, is a full plenum. Peikoff endorses Parmenides in his lecture course "Unity in Ethics and Epistemology". Parmenides: "What is, is. What is not, is not. What is not can neither be nor thought about." Nothing is not a type of something, leading to the principle that the universe is a plenum, solidly packed.

Peikoff also reports Ayn Rand used a concept of "the little stuff" posited as ultimate constituents of matter, smaller than even subatomic particles (that which is where nothing isn't).

[Boydstun 181]

.

Not only the geodetic and frame-dragging precessions, but Thomas precession is exhibited in GP B (§7).

Here is a nice summary report from Lockheed Martin.

NASA Press Conference – Excellent!

The Paper

What a piece of work is man, how noble in reason, how infinite in faculty. –WS

~~~~~~~~~~~~~~~~

Here is a review of experimental evidence for Einstein’s special relativity and general relativity as of 2005.

Here are experimental tests between the gravity theories of Whitehead (1922) and Einstein (1915), once thought to imply no experimental distinctions.

Edited May 18, 2011 by Boydstun

[Boydstun 181]

A reliable online reference for relativity, special and general, is Einstein Online.

Also, on special relativity, “Space, Rotation, Relativity” – Part 4.

[Boydstun 181]

Of related interest:

Isaac Newton’s Scientific Method:

Turning Data into Evidence about Gravity and Cosmology

William L. Harper (2012 Oxford)

“Newton's method endorses the radical theoretical transformation from his theory to Einstein's. Harper argues that it is strikingly realized in the development and application of testing frameworks for relativistic theories of gravity, and very much at work in cosmology today.”

Edited March 16, 2012 by Boydstun

[Boydstun 181]

Demanding tests for theories of dark energy and the origin of the acceleration of cosmic expansion are being set by precise cosmic distance and size measurements relying on baryon acoustic oscillation signals.

Probing Dark Energy with Baryonic Acoustic Oscillations

Seo and Eisenstein (2003)

Baryon Acoustic Oscillations

Bassett and Hlozek (2009)

Some Results

Anderson et al. (2012)

[Boydstun 181]

.

The Euclid satellite is to launch in 2019 and gather cosmic data bearing on dark matter and dark energy.

[Oscar Munoz 0]

Boydstun, hi.

I wish I knew how to create hyperlinks and embed someone else's quotes in my post

Sorry, but I don't remember you from the past. Can you help me remember? thanks

[Boydstun 181]

Hi Oscar,

It was a long time ago. We never met. We corresponded on issues in relativity (especially GR) and metaphysics between 10/23/88 and 3/28/89. You were a physics major. You lived in Torrance. I lived in Chicago. You had written to me by referral from Ron Kagan. He knew of me because I had written him a letter responding to an essay he had in Objectively Speaking titled “The Foundations of Metascience.”

I still have all your letters and copies of mine. They were all hand written! They are fun reads. In your last letter, you had received a scholar award for graduate school in physics at UCLA. I hope you were able to take some advantage of that, and anyway, I am delighted to see you still have a lively interest in these topics.

Stephen

[Oscar Munoz 0]

Hi, Stephen.

I would love to see some of our correspondence. Maybe you can scan them in one day and email me some copies.

Also, I did go to UCLA a couple of years, but I decided to go into business instead.

I did once want to do theoretical research as a living, but seeing the so-called scientific culture at UCLA was too much to bear. UCLA was inspired me like waiting at the DMV without a reservation inspired me.

Graduate work in Physics is too hard to not love the road you are on.

So now I study Physics as a hobby.

[Boydstun 181]

Faster than Light? is a different perspective on special relativity, light from a deep and twinkling eye.*

~~~~~~~~~~~~~~~~

Oscar, I sent you a personal message over the email service of this site. –S

[Boydstun 181]

Resolution of distance down to the level of about 5 times the theoretical Schwartzchild radius of a black hole has now been attained:

“Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87”

MIT – Doeleman et al.

A future test, by the Event Horizon Telescope, of the GR prediction that only mass and angular momentum (and net electric charge, not likely large) are conserved in black-hole influx is summarized here.

[Boydstun 181]

.

How Einstein Found His Field Equations: 1912–1915

—A—

—B—

John Norton (1984)

Edited November 15, 2012 by Boydstun

[tadmjones 40]

I see time as a mathematical construct. Existence is perceived by the senses ,which always operate on the immediate temporal range. All consciousness must by necessity operate on the same level. Past is an intelligible abstraction, as well as future though present is fundamental.

Time is therefore an abstraction that denotes referents other than the present ,which can either be remembered or postulated.

[Harrison Danneskjold 151]

I see time as a mathematical construct. Existence is perceived by the senses ,which always operate on the immediate temporal range. All consciousness must by necessity operate on the same level. Past is an intelligible abstraction, as well as future though present is fundamental.

Time is therefore an abstraction that denotes referents other than the present ,which can either be remembered or postulated.

 

Time is another dimension, like the three spatial ones.  (I know it sounds like a cliché anticoncept, but it really isn't)  The difference is that you have no choice except to move through time.

You could imagine two-dimensional Mario as having a third, temporal dimension, which would be like depth.  He can move up/down and right/left, but no matter which way he moves, he is constantly moving through time.  It's handy for getting some idea of this fourth dimension.

I won't go into the specifics of it at the moment, but if you'd like I could explain it in more detail at some point.  But Einstein's relativity, which explained that gravity is the distortion of space and time by the presence of matter, identified spacetime as being a single four-dimensional existent.

[tadmjones 40]

Time is another dimension, like the three spatial ones.  (I know it sounds like a cliché anticoncept, but it really isn't)  The difference is that you have no choice except to move through time.

You could imagine two-dimensional Mario as having a third, temporal dimension, which would be like depth.  He can move up/down and right/left, but no matter which way he moves, he is constantly moving through time.  It's handy for getting some idea of this fourth dimension.

I won't go into the specifics of it at the moment, but if you'd like I could explain it in more detail at some point.  But Einstein's relativity, which explained that gravity is the distortion of space and time by the presence of matter, identified spacetime as being a single four-dimensional existent.

Let me start by saying that I would like to apologize to Mr B for muddying his thread with my late night pontifications from a wobbly soapbox. Lacking any theoretic knowledge of physics, and stemming from my purely layman perspective, I tend to flinch at the way or manner time seems to be spoken about in physics. As far as I can wrap my head around the concept of time, it seems to refer to a relation between entities(a desciption of a duration as it relates to specific actions of specific entities) and not a substance in and of itself. I have often wondered if the cosmological constant isn't actually a mathematical correction devise to rectify the noncausual aspect of 'time' in the methodology. I think I have a hard time(no pun intended) of separating science and philosophy.

Edited May 13, 2013 by tadmjones

[Plasmatic 124]

Or rather some scientist have a hard time wrapping their head around philosophy.

[Boydstun 181]

Einstein was the first to realize, in 1916, that his GR equations predicted the existence of gravitational waves under certain conditions. Russell Hulse and Joseph Taylor obtained strong indirect evidence in 1981 for the existence of gravitational waves by observing a reduction in orbital energy from an orbiting pulsar system in the amount predicted by GR for dissipation of that energy in such a system were the energy carried away in gravitational waves.

 

LIGO aims to detect gravitational waves directly using laser interferometers sited far apart in the US mainland. The sensitivity of the LIGO detectors so far has been only enough to detect gravitational waves resulting from pulsar collapses (a big though rare event) at distances from us wherein hundreds of centuries could go by without a collapse. No waves have been detected at this sensitivity. LIGO is now being enhanced to achieve a sensitivity to binary-pulsar collapses in space much farther from us wherein the total volume would have hundreds of collapses each year. The advanced LIGO* is scheduled to get to work in 2016.

 

For a look at future interferometer detectors operating from outer space capable of detecting gravitational waves so pervasive that they could be used to infer activities inside the event horizon of a black hole or to infer conditions in the part of the cosmic expansion before the universe lighted up with what is now known as the cosmic background radiation, see the cover article of the October 2013 issue of Scientific American, authored by Ross Andersen.

[StrictlyLogical 406]

Tadmjones you will glad to know that as one with a physics degree I tend to agree with you.

 

There is nothing in experimental or theoretical physics which relies upon an interpretation of space or time as "entities" in reality, separate and apart from existents, be they tables, stars, or positrons.  Space and time fundamentally are quantifications of relationships between existents.

 

All of physics is entirely consistent with an interpretation of space and time, or any other dimension (e.g. supersymmetry) as values or placeholders which are descriptive of relationships between existents.  A mathematical background which keeps track of those relationships.  To be sure this background is not necessarily "empty" but the activity occurring in any n-dimensional "volume" is to be distinguished from the values we associate with the position and time etc. of those activities. 

 

Those relationships, which we refer to with values of space and time, change in specific ways for specific reasons, but it is not space or time that changes (relativity dismisses any concept such as absolute space or the "ether"), it is the way entities behave in relation to each other under certain circumstances.

 

Length is not a thing, the space between two particles is not a thing, and neither is the position of an existent a thing.   

[Boydstun 181]

Polarization patterns in CMB support trillionth-of-a-second inflationary model of universe expansion just after the initial singularity – 3/17/14!

 

Institute of Physics

 

BBC

Edited March 17, 2014 by Boydstun

[Boydstun 181]

.

Gravitationally lensed supernova is shown, and potential for new way of measuring universe expansion rate is opened.

[frank harley 2]

Tadmjones you will glad to know that as one with a physics degree I tend to agree with you.

 

There is nothing in experimental or theoretical physics which relies upon an interpretation of space or time as "entities" in reality, separate and apart from existents, be they tables, stars, or positrons.  Space and time fundamentally are quantifications of relationships between existents.

 

All of physics is entirely consistent with an interpretation of space and time, or any other dimension (e.g. supersymmetry) as values or placeholders which are descriptive of relationships between existents.  A mathematical background which keeps track of those relationships.  To be sure this background is not necessarily "empty" but the activity occurring in any n-dimensional "volume" is to be distinguished from the values we associate with the position and time etc. of those activities. 

 

Those relationships, which we refer to with values of space and time, change in specific ways for specific reasons, but it is not space or time that changes (relativity dismisses any concept such as absolute space or the "ether"), it is the way entities behave in relation to each other under certain circumstances.

 

Length is not a thing, the space between two particles is not a thing, and neither is the position of an existent a thing.   

The Lorentz coefficient, or 'gamma', when added to the classical Newtonian makes time shrink as acceleration approaches 'C', the speed of light. mass likewise becomes infinite. This is the basic formulation fpr special relativity as cited by Einstein himself.

 

in this sense, yes, time is a reality, or a 'thing'.

 

General relativity puts this equation on a spacetime manifold (with Ricci curvature) and assesses the results with respect to a Riemian 4-tensor: gravity causes light to bend, therefore distorting time.

 

Because our working knowledge of gravity comes from the effect that it has on mass, spacecraft are basically trying to find gravatational waves in places where there is no mass to verify that said waves really do exist. The wave behavior would correspond, btw, to 'Weyl geodesics.

[Boydstun 181]

Mr. Harley,

 

We do not add a coefficient. We multiply it. Accelerations do not approach the limiting velocity c. Velocities approach the limiting velocity c. Relativistic time dilation is not a shrinkage. Gravitational bending of light does not “distort” time. We have established vocabulary and concepts in such well-established physics, and you bring no education in science with your garbling.

 

Stop talking down to people all the time, whether talking of physics or Kant, pretending you know all and people here are just a bunch of ignoramuses from whom you could not learn anything. It’s gross.

[Boydstun 181]

Scrutiny of BICEP2 evidence of cosmic inflation and primordial gravitational waves suggests signals could come from dust in our own galaxy. Science News follow-up is here. Further report from the Planck survey later this year may clear the BICEP2 proposed discovery or take it down.