Black holes - Are they real?

With regard to the Christian Science Monitor website, its not a religious website if that's what you think. Its just another science news website. The same article appears on all the science news websites; blogs.discovermagazine.com/80beats/2010/...heart-of-the-galaxy/

Anyway, You make some excellent points and they are hard to argue with Mark!

One last example that explains my point;

Watch this 30 second Youtube video;
Radial Velocity Method For Finding Exoplanets -




Now everyone looking for exoplanets is now familiar with that very simple animation that shows how the star wobbles a small bit as a planet orbits it. In the animation there are only 2 objects, the star and the planet, both gravitationally bound to each other.

Now, just like that Sgr A* GIF image you posted, imagine we zoom in on that Youtube animation, what would we see? We would only see the star in the middle, the planet would be outside the picture. And what would it look like? Well we would see one very heavy star orbiting "SOMETHING"!!!! What would that single star be orbiting? In the zoomed in animation, you would see the star orbiting around an empty black area of space.

WHAT!!!!! Dam..... That sounds just like a black hole!! The star would be orbiting a black hole that, if we calculate it out, the mass would be equal to the mass of the planet that's currently outside our zoomed in animation image.

Do you get the point i'm making? With only two simple objects, i was able to make a black hole, and i was even able to calculate its mass. You have got to admit Mark, you can't completely rule out what i'm suggesting. Maybe the S2 star in the Sgr A* image is orbiting a focal point and not a black hole that has forever swallowed vast numbers of stars.

Now play the Youtube animation video again, and try ignore the orbiting planet. Imagine you have zoomed in and you can only see the star...... orbiting an empty black area of space that does appear to have a small mass.

Then multiply the animation image by about 200 billion and you have the Milkyway, and a possible focal point with stars orbiting very fast around it.

John.

John - I can see where you are coming from. However, the following thought experiment might help.

Think of a constellation of twelve equal-mass stars evenly distributed as a circle - rather like the configuration on the EU flag. Now place a suitable mass at the centre and consider the ring of stars to rotate about this mass such that each star is in orbit. This is like a constellation of GPS satellites encircling the Earth and I can imagine the twelve stars to continue in this fashion without any difficulty.

Now imagine the same constellation without a real central mass. Again we consider the ring of stars to be initially, at some instant, having a motion that can be considered as rotating about their centre of mass. Can you visualise this being stable and to continue to rotate with the same configuration - I cannot.

We can do a bit of analysis of this and see what we can tweak out. The barycentre - or centre of mass for this system (which has no real central mass) - is bang on centre. We can consider that point as a point-mass of 12 stellar masses when considering another point mass some distance away so we can predict its trajectory with respect to our constellation.

However, if we consider one star of the constellation we cannot compute the gravitational force between that and the centre of mass of the whole. This force is proportional to the product of the two masses under mutual attraction and, in this case, one twelfth of the centre of mass really belongs to the star under investigation. We've accounted for this mass twice and we can't have a star being attracted to itself somewhere else.

Okay - now lets try and get out of this problem by considering the gravitational force between the same star - and the centre of mass of the other 11 stars. Well, that centre of mass is at a different location to the centre of mass of the twelve. The same will be true when we consider each star in turn and each would be orbiting a different point - and therefore can not orbit as a ring of stars. Further, the bigger we make the ring - the bigger the problem. We have - what should be a stable orbital configuration but it cannot be supported with your model.

Does that help?

BTW - I did follow up on the Fermi - bubbles - very interesting - but for another day.

Mark C.

The EU flag stars scenario. I can visualise in a much simpler way.

Put your 12 stars floating in the kitchen sink with the water flowing down the drain in the middle. With the large mass in the middle, the "cone" shape of the sink is very deep and stars fall down the drain quicker. With no large mass in the centre, the "cone" shape of the sink would just be flatter and the stars would just take longer to go down the plug hole.

Either way, i think i made my point here. I think i have clarified in my own mind that my assumption could well be true. I just wanted to see if anyone else agreed and could see the point i was making.

As much as we think we have solved many of the problems in physics today, i think we are only at the tip of the iceberg.

Thanks Mark,
John.