Ant Sinclair Posted August 20, 2015 Posted August 20, 2015 Below is an extract and below it the Link from where it came. Is the article correct concerning Uniform Gravity Across The Universe - is this what is currently accepted? Astronomers using the National Science Foundation's (NSF) Green Bank Telescope (GBT) in West Virginia and its Arecibo Observatory in Puerto Rico conducted a 21-year study to precisely measure the steady "tick-tick-tick" of a pulsar known as PSR J1713+0747. This painstaking research produced the best constraint ever of the gravitational constant measured outside of our Solar System. Pulsars are the rapidly spinning, superdense remains of massive stars that detonated as supernovas. They are detected from Earth by the beams of radio waves that emanate from their magnetic poles and sweep across space as the pulsar rotates. Since they are phenomenally dense and massive, yet comparatively small - a mere 20-25 kilometers across - some pulsars are able to maintain their rate of spin with a consistency that rivals the best atomic clocks on Earth. http://www.dailygalaxy.com/my_weblog/2015/08/a-distant-pulsar-reveals-gravity-as-constant-throughout-the-universe.html
DrP Posted August 20, 2015 Posted August 20, 2015 Why would it change at all? It is supposed to be a constant (G), no?
swansont Posted August 20, 2015 Posted August 20, 2015 Below is an extract and below it the Link from where it came. Is the article correct concerning Uniform Gravity Across The Universe - is this what is currently accepted? Yes, that is the currently accepted idea. That gravity (as with all of physics) follows the same rules everywhere.
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 I do agree that it is uniform, are magnetic fields a part of the reason the G Constant is the same every where?
Strange Posted August 21, 2015 Posted August 21, 2015 I do agree that it is uniform, are magnetic fields a part of the reason the G Constant is the same every where? G is a universal constant and gravity has nothing to do with magnetic fields(*) so: no. (*) Apart from the fact that magnetic fields have energy and therefore can have a gravitational effect...
swansont Posted August 21, 2015 Posted August 21, 2015 I do agree that it is uniform, are magnetic fields a part of the reason the G Constant is the same every where? No. G is the gravitational constant, and has nothing to do with magnetism (it's in the name. "gravity", not "magnetic")
Strange Posted August 21, 2015 Posted August 21, 2015 And, if anything, this result would show that G is independent of magnetic fields: there is a very weak geomagnetic field on Earth, but very, very strong magnetic fields around pulsars.
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 G is a universal constant and gravity has nothing to do with magnetic fields(*) so: no. (*) Apart from the fact that magnetic fields have energy and therefore can have a gravitational effect... Strange the last line in Your post quoted above beginning (*) - can You explain what it means please!
Strange Posted August 21, 2015 Posted August 21, 2015 Strange the last line in Your post quoted above beginning (*) - can You explain what it means please! All forms of energy (and mass) are a source of gravity. Magnetic fields have energy associated with them (I think) and so will have a (very small) gravitational effect.
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 All forms of energy (and mass) are a source of gravity. Magnetic fields have energy associated with them (I think) and so will have a (very small) gravitational effect. So then strange as We know these days there are magnetic fields Universe-Wide, what constitutes a magnetic-field? - are these fields fields of nothing or do they contain forms of energy, all this energy can be related to mass through Alberts' work, do the magnetic fields relate to a substantial mass?
Strange Posted August 21, 2015 Posted August 21, 2015 (edited) I have no idea what the magnetic field strength in different areas of space is. It will obviously be greater near stars than the interstellar or intergalactic space. And it falls off with an inverse cube law. But I have no idea what reasonable values would be. Looking at this: http://www.scholarpedia.org/article/Galactic_magnetic_fields and doing some rough mental calculations, my feeling is that it would be orders of magnitude less than the interstellar gas (which is a pretty serious vacuum). I don't have time to try and work out more accurate figures now... Edited August 21, 2015 by Strange
swansont Posted August 21, 2015 Posted August 21, 2015 So then strange as We know these days there are magnetic fields Universe-Wide, At issue is their strength, not their existence. what constitutes a magnetic-field? - are these fields fields of nothing or do they contain forms of energy, all this energy can be related to mass through Alberts' work, do the magnetic fields relate to a substantial mass? Since energy is a property, they do not "contain forms of energy". The energy content of a magnetic field is proportional to the square of the field strength, integrated over the volume.
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 At issue is their strength, not their existence. Since energy is a property, they do not "contain forms of energy". The energy content of a magnetic field is proportional to the square of the field strength, integrated over the volume. Whatever the magnetic fields components/properties are, could they be related to mass in any way?
Strange Posted August 21, 2015 Posted August 21, 2015 Whatever the magnetic fields components/properties are, could they be related to mass in any way? What do you mean by "related to mass"? It has a gravitational effect, equivalent to mass but that's all.
swansont Posted August 21, 2015 Posted August 21, 2015 Whatever the magnetic fields components/properties are, could they be related to mass in any way? The energy content of a magnetic field is proportional to the square of the field strength, integrated over the volume. No mention mass anywhere in there.
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 What do you mean by "related to mass"? It has a gravitational effect, equivalent to mass but that's all. The properties/contents of a magnetic field - if theres energy/particles/waves there, through E=MC2 shouldn't there be an equivalent mass of the magnetic fields in the Universe?
Strange Posted August 21, 2015 Posted August 21, 2015 The properties/contents of a magnetic field - if theres energy/particles/waves there, through E=MC2 shouldn't there be an equivalent mass of the magnetic fields in the Universe? The gravitational effect of the energy of the magnetic fields is the same as the equivalent mass. Or to put it another way, if you somehow convert the energy to mass (using magic) then e=mc2 tells you what mass you would get (a really tiny amount as it would be a tiny energy divided by a really big number)
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 A 'tiny' amount of mass ....... mmmm Below is from the Royal Society regarding the left-hand cosmological magnetic field strange! https://www.ras.org.uk/news-and-press/2635-left-handed-cosmic-magnetic-field-could-explain-missing-antimatter
swansont Posted August 21, 2015 Posted August 21, 2015 A 'tiny' amount of mass ....... mmmm Below is from the Royal Society regarding the left-hand cosmological magnetic field strange! https://www.ras.org.uk/news-and-press/2635-left-handed-cosmic-magnetic-field-could-explain-missing-antimatter Sorry, I'm missing where they say how strong the field is, which is the only way to evaluate how large or tiny the energy (and therefore mass equivalent) would be.
Strange Posted August 21, 2015 Posted August 21, 2015 A 'tiny' amount of mass ....... mmmm Below is from the Royal Society regarding the left-hand cosmological magnetic field strange! https://www.ras.org.uk/news-and-press/2635-left-handed-cosmic-magnetic-field-could-explain-missing-antimatter Interesting. But could you explain why you think it is relevant? Sorry, I'm missing where they say how strong the field is, which is the only way to evaluate how large or tiny the energy (and therefore mass equivalent) would be. The linked paper says ~10-14 G. So I think that is equivalent to about 10-48 kg/m3. Or about one electron in a cube 1 km on each side. So not a very significant mass equivalent. (I may well be out by a large factor!)
swansont Posted August 21, 2015 Posted August 21, 2015 A constant 1 gauss field has an energy density of about 10^-3 J/m^3, and the energy varies as the square of the field If I'm doing the math right, the mass equivalent is around a kg per cubic light year, which agrees with Strange's number
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 I'm not sure if I'm doing this correctly but for an approximation is it good? If the radius of the universe is 46.9e9LY, can I then use 4/3 pi r3 formula for the calculation? This works out at approximately 4.321e32 - so would there be 4.321e32KG?
swansont Posted August 21, 2015 Posted August 21, 2015 I'm not sure if I'm doing this correctly but for an approximation is it good? If the radius of the universe is 46.9e9LY, can I then use 4/3 pi r3 formula for the calculation? This works out at approximately 4.321e32 - so would there be 4.321e32KG? 4.321e32 cubic LY is about the mass of 200 suns. There are probably individual stars with that much mass. edit: yes https://en.wikipedia.org/wiki/List_of_most_massive_stars_known#List_of_the_most_massive_stars
Ant Sinclair Posted August 21, 2015 Author Posted August 21, 2015 4.321e32 cubic LY is about the mass of 200 suns. There are probably individual stars with that much mass. edit: yes https://en.wikipedia.org/wiki/List_of_most_massive_stars_known#List_of_the_most_massive_stars In Earth terms it's a large mass, in Universal terms(the Milkyway has a much larger mass) the mass is minor. If magnetic fields are not playing a part in keeping G constant everywhere, what is causing it to be so?
Strange Posted August 21, 2015 Posted August 21, 2015 It is just a universal constant. Like c, α, μ0, ε0, e, etc. There is (as far as we know) no reason for it to change over time or place. (And absolutely no reason to imagine that magnetism has anything to do with it.)
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