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skeldon

Gravity is Dark matter???????????

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Hi all, I am new to all this but have a theory about gravity. 

I dont know if this has been said in the past but I was sat down thinking and I had a thought. Could gravity be dark matter?? I thought maybe space is all dark matter and planets sqeeze into it and rather then gravity pulling us down maybe it is dark matter PUSHING us down??

I don't know any other way to describe but to imagine a rubber band in ur fingers pulled tight and u pull it so its tight. If you push your finger between the to bits it will sqeeze ur finger.

Maybe dark matter is split open and trying to squeeze back hence the round planets .  

Could gravity possibly be pushing rather then pulling???

Thank you for reading this, Steve

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Dark Matter, although of unknown nature, behaves like extra mass in the Universe.  It is detected by such things as anomalous rotation of galactic clusters, and the images of distant galaxies whose light has been deviated in its path.  In fact, most of the mass in the Universe is Dark Matter.  So DM acts - in gravitational terms - like regular matter.  

And just to complicate things, remember that gravity is not actually a force but - according to the General Theory of Relativity - a distortion of spacetime.

Doug.

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Personally, I work on the principle that there are thousands of professional physicists out there who spend their entire academic lives studying these things.  I tend listen to what they have to say on a relevant subject.

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12 hours ago, skeldon said:

Hi all, I am new to all this but have a theory about gravity. 

I dont know if this has been said in the past but I was sat down thinking and I had a thought. Could gravity be dark matter?? I thought maybe space is all dark matter and planets sqeeze into it and rather then gravity pulling us down maybe it is dark matter PUSHING us down??

I don't know any other way to describe but to imagine a rubber band in ur fingers pulled tight and u pull it so its tight. If you push your finger between the to bits it will sqeeze ur finger.

Maybe dark matter is split open and trying to squeeze back hence the round planets .  

Could gravity possibly be pushing rather then pulling???

Thank you for reading this, Steve

This is similar to the speculations I made when about 8 yrs old and thought it was the weight of air pushing down on us. Like my idea yours does not stand up to experiment. The best theory we have is General Relativity where the "force" of gravity is in fact the curvature of space time. Until I see evidence that this theory is contradicted by good scientific evidence I will not be seeking other options.

Regards Andrew 

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14 hours ago, skeldon said:

Maybe dark matter is split open and trying to squeeze back hence the round planets .  

On reflection if this were the case then the force of gravity would be proportional to volume of an object rather than it's mass would it not.

Regards Andrew

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Marvellous, that's changed my whole concept of the universe.  Certainly explains why I feel much heavier when I switch a light off.  

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Gravity is dark matter - no it's not.

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sorry - duplicate post

Edited by saac

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Taking the speculation seriously (and why not?), the claim is that if two spheres A and B experience a force that moves them together, then this is due not to the attractive force of gravity, but instead to a "pushing" force from their surroundings. Then the theory would need to explain why it pushed the spheres towards each other, rather than in some other direction. Having accomplished that, it would need to extend the reasoning to a static cloud of particles, which collapses towards its centre of mass. Dark matter wouldn't accomplish this. Only angels would suffice.

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I don't pretend to understand any of these concepts but like many on this great forum; I do ponder the nature of it all.

so because of a particular explanation, I ask myself, if gravity is indeed the warping of space time, and the force we feel is a concequence of us falling into the well caused by mass.

how does the well change with the stretching of space time? And if space time is stretching what is happening to it...is is getting thinner, as a fabric might.

as you can see it's all strange to my mind :)

Ray

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1 hour ago, libraryman said:

I don't pretend to understand any of these concepts but like many on this great forum; I do ponder the nature of it all.

so because of a particular explanation, I ask myself, if gravity is indeed the warping of space time, and the force we feel is a concequence of us falling into the well caused by mass.

how does the well change with the stretching of space time? And if space time is stretching what is happening to it...is is getting thinner, as a fabric might.

as you can see it's all strange to my mind :)

Ray

Ray - these are extremely difficult concepts to get your head round, and I certainly have difficulties!  I suppose a "well" will be deeper and wider in the vicinity of a greater mass.  As for space/spacetime getting thinner, I'm not sure that has any substance - it just bends as far as I know.  I eagerly await being corrected here!

Consider light.  It travels in straight lines (apart from when it meets a boundary).  But light from "behind" a massive object seems to be attracted to that object, creating the illusion that it has originated somewhere else.  (This is called gravitational lensing.)  It is as if the light continued in a straight line through space, but the actual space was curved.  

Doug.

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Am i alone in thinking a couple of the posts here have been a bit harsh on the OP. The postee has obviously had a thought, expressed it and asked for some thoughts on the matter and some of the answers have engaged him like he was a oddball conspiracy theory troll. Not a great way to to introduce a newbie. Could just be me of course.

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As an aside (and I only know little bits here and there) it is an astonishing concept (assuming I understand it correctly!) that mass (basically) = energy and yet also that something with no mass (e.g. a photon) is pure energy and therefore has no 'option' than to travel (in a vacuum) at the speed of .....well, light. Does this mean that a photon travelling in something less than a vacuum (and therefore I presume not travelling at the speed of light) then develops mass? Or is the energy somehow dispersed within the medium?

In regard to the original post, I don't really know enough to respond in a reasonable way but it's amazing how much we as a pretty hairless ape have discovered and yet in reality, we know almost nothing.

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My understanding is (and again im completely groping in the dark) that even in a motionless state Photons are massless. Recent experiments have indeed completely halted a photon for a minute using cold atoms. Now if if i get this right if the photon had mass based on its energy then when stopped it would be incredibly massive but as far as im aware no changes were detected in the experiments. And i to await to be enlightened.

 

https://www.newscientist.com/article/dn23925-light-completely-stopped-for-a-record-breaking-minute/

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Wow. I know even less than I did before :icon_biggrin:

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@Moonshane A photon essentially has zero "rest mass", but because it has energy when moving, this is equivalent to mass according to the Special Theory of Relativity, and that mass is referred to as relativistic mass.  So a photon does have mass and therefore momentum.  None of this stuff is easy to grasp - I'm still struggling, but also enjoying trying to come to terms with it all!

Another complication here is that E = mc^2 is not in fact the complete equation for the energy of a moving particle.  (Edit: It IS, if the m is the relativistic or kinetic mass, but not just the rest mass.  Those two masses are related by the Lorentz Factor.)

Doug.

Edited by cloudsweeper

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Well... 

If if I was posting for the first time on an astronomy forum and had some of these replies, I don't think I would have come back either.

I'm not saying that the OP is right or wrong, I have little idea to be honest. I also suspect he/she is incorrect, however some of the replies are less than respectful.

 

What happened to friendly and welcoming? Or is that only for people that post up things that are generally considered as correct (according current thinking). Bit of luck that Copernicus didn't have SGL to suggest his ideas that the Earth revolved around the Sun...

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Why can't we settle for the Number 42 and be done with? :icon_biggrin:.

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5 hours ago, Moonshane said:

As an aside (and I only know little bits here and there) it is an astonishing concept (assuming I understand it correctly!) that mass (basically) = energy and yet also that something with no mass (e.g. a photon) is pure energy and therefore has no 'option' than to travel (in a vacuum) at the speed of .....well, light. Does this mean that a photon travelling in something less than a vacuum (and therefore I presume not travelling at the speed of light) then develops mass? Or is the energy somehow dispersed within the medium?

In regard to the original post, I don't really know enough to respond in a reasonable way but it's amazing how much we as a pretty hairless ape have discovered and yet in reality, we know almost nothing.

 

 

Moonshane you are indeed correct that the photon travelling in the vacuum of space has no other option but to travel at the speed it does. That speed is fixed by two particular properties of the medium through which the photon is travelling.  More correctly, it is the property of the medium that fixes the speed at which the  disturbance of the electric and magnetic field are allowed to propagate.  

 

The vacuum permittivity  εo fixes the propagation speed of the electric field while the propagation of the magnetic field is fixed by the vacuum permeability µo.  Together these play in an expression from Maxwell’s equations to provide the maximum speed that the combined electric and magnetic field can propagate through the vacuum or free space:

 

c = 1/√ (εo µo)  where c = speed of light     εo  = 8.8548 x 10-12 F/m                    

 

    µo   = 1.2566 x10-6 H/m  , this fixes the speed of light (all electromagnetic radiation) at approx 300 million m/s

So the reason the photon travels at the speed it does is not really because that it does not have mass as such (although that would prohibit it travelling at 3 x108 m/s), rather it is that this is the speed limit imposed upon it by free space and those particular constants – the wave simply cannot propagate any faster than that. 

 

As for the possibility of photons gaining mass when they travel through a different medium at say a lower speed, then no that would not happen.  The photon has no mass because it does not interact with the Higgs field – it is the Higgs field that bestows the property of mass and not teh speed of the particle.  Irrespective of its speed, say 2 x108 m/s when travelling through glass, a photon still does not interact with the Higgs field and so remains massless.

 

I must admit whenever I look at Maxwell's equations the simplicity is utterly astounding. Any slight variation in those two constants and our universe would be completely different, light nor matter may not even exist!

 

Jim

Edited by saac
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Cheers Jim

What a really helpful post. I think I actually get it!

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Lol, I hope I have got it right then.  seriously though, I remember the first time this was explained to me and the simplicity of that equation and the idea that, what I like to think of as the stickiness of space (permittivity and permeability), fixes the universe's speed limit. It just blew me away it was beguilingly intuitive.  Of course Maxwell was the genius that took us to that point of understanding, no wonder Einstein credited him so much.

 

Jim

Edited by saac
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Indeed Jim. I recently enjoyed a documentary about Maxwell. A truly astonishing mind.

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3 hours ago, ant said:

What happened to friendly and welcoming? Or is that only for people that post up things that are generally considered as correct (according current thinking). Bit of luck that Copernicus didn't have SGL to suggest his ideas that the Earth revolved around the Sun...

Copernicus first came up with a set of axioms that he distributed in hand written form, the "Little Commentary" which was unpublished. Then after years of observation and calculation he published "On the Revolutions". Had he published on SGL I am sure he would have been given a fair hearing. Had he just speculated without any observation or calculation then I suspect not.

I, for one, would prefer SGL not to become a forum for the airing of speculation about Physical Theories. 

If this offends you or anyone else that is not my intention. 

Regards Andrew

 

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dont get too confused about the actual number for the constants..remember this is just what they are in the rather random units we choose. often theorists set them to unity :) . 

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