## Dark matter and curved space

Discussions on classical and modern physics, quantum mechanics, particle physics, thermodynamics, general and special relativity, etc.

### Dark matter and curved space

(I'm starting this thread in the Physics forum because it has something to do with pure curved space, but it is a new way to explain dark matter, so in this sense, it is not really main stream. If it gets too far away from main stream, don't hesitate to put it in Personal Theory.)

Hi everybody! Thanks to the controversial discussion on deformed space with my fellow Andrex, I had the following idea about dark matter.

I think I already explained here that curved space would increase the dimension of the sun's diameter the same way it gives the impression that the stars have moved away from the center of the sun. Here is the drawing that shows what I mean:

The dotted arrows represent the direction the light from the star and the one from the periphery of the sun would follow without gravitation, and the plain arrows represent the same two lights being curved by gravitation. As you can see, the earth observer would see the periphery of the sun where the star appears to be, which means that the sun would look larger than what it really is.

If I am right about the sun, galaxies would also look larger than what they really are, so since we calculate the speeds of their stars out of the distance from their center, and if that distance is really smaller than what we see, we automatically expect them to go slower than they actually go: in other words, they would look too fast for their observed orbital distance. Now, since light bends more where space is more curved, the light from the periphery of a galaxy should bend less than the one from near the bulge, thus those too fast speeds should not vary proportionally to Newton's law. The divergence from the law should be more important for the stars that are close to the bulge than for those that are near the periphery, what should effectively flatten the speeds' curve.

Now if the sun is really smaller than it appears, then its rotation period calculated out of its speed measured with doppler effect should look a bit longer than it really is. Does it?

Inchworm
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### Re: Dark matter and curved space

I said the dotted arrows would represent the direction of light without gravitation, so here is the right drawing:

Inchworm
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### Re: Dark matter and curved space

Inchworm » 01 May 2017, 20:33 wrote:I said the dotted arrows would represent the direction of light without gravitation, so here is the right drawing:

Yes, I think for the Sun this is correct. For galaxy rotation curves, I would doubt it. Firstly, when the rotation curve 'anomaly' was discovered, GR was well established and worked into the astronomical models. Secondly, I think for a diffuse thing like a galaxy, the effect is tiny compared to the rotation speed anomaly, which is rather large. I cannot for one moment think that they did not take all the relativistic effects (lensing and gravitational time dilation) into account.

BurtJordaan
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### Re: Dark matter and curved space

I'm pleasantly surprised that you admit so easily my proposition about the sun looking larger Burt. :0) I never succeeded to convince anybody before, probably because it means that we should shrink it on the mapping of the stars six months later, thus that those stars would not appear to be hidden by the sun anymore, what kind of contradicts the curved space principle. That eventual contradiction doesn't change the main idea though: if the sun looks enlarged, then galaxies should look enlarged too. You say that scientists have probably taken into account GR effects, but if nobody thought about the effect I'm talking about, namely an enlarged sun, then nobody could have thought of applying it to galaxies. You may be right about the importance of the effect though, I did not calculate it, but I still think it is worth studying it since it seems to be able to explain the flatness of the curve. As for the exceeding speeds, if the galaxies would be a lot closer than what they appear for instance, we might actually be exaggerating considerably their real size, what would thus also be adding to the exceeding speeds of their stars.

It is more difficult to explain the flatness of the curve though. What do you think of the idea that the inconstant curved space of a galaxy would flatten the curve? Do you also think the effect is too small to account for the whole phenomenon?

Inchworm
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### Re: Dark matter and curved space

I found some data obtained by doppler effect from the sun's rotation, and guess what, as I hoped, it gives a longer rotation period than the one measured out of the sun's spots: .25 days longer than the published period of 25.05 days, which is about 1% too long. There is a mistake on the published velocity though: it should be written 1,996.944 m/s, and it is written 7.189 10^6 m/s, which is the right speed but in km/h, not in m/s. The author says that temperature, pressure, elemental abundance, density and surface gravity, may affect the width and the height, as well as the shape and position of the spectral lines, but he says they were ignored. If we compare the deflection angle of starlight around the sun (1.75'') to the apparent optical angle of the sun (32'), we get .091%, which is not even close to the 1% longer period, so I'm afraid those ignored factors are too important to help me test my proposition.

Inchworm
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