 |
GALAXIES
Pete Thompson - galaxies from the inside
To try to help Robert Poole a a little consider this. We are always looking 'out' at the universe because in a very real sense we are at the center of the universe. The observable universe, that is. In a neat return to our ancestors, who believed the earth was at the center of the universe modern science now says that we are at such a point. The observable universe is all that really matters. Any part of the universe so far away that its light hasn't reached us also means that its gravity, and any means of influencing or interacting with us is non-existent as far as we are concerned. What is left - the stuff we can see, or detect is the observable universe and we are necessarily at its center because light travels equally speedily in each and every direction.
Ingvar Astrand - Redshift
Edwin Hubble discovered that the displacement of the spectral-lines in the radiation from galaxies were proportional to the distance. He didn't understand why and interpreted it as a Doppler effect. Max Planck discovered the same displacement of the heat radiation and interpreted it as quantum change relation between the wave units. The reality is that they misinterpreted the same entropy phenomenon where the radiation dissipates towards equilibrium. See examples on www.theuniphysics.info
Steve Pond-Galaxies
Not sure about being an expert Robert, but here goes. There is no centre to the universe. The big bang was not an explosion but the start of an expansion, with every part of space moving away from every other part, in the light of this there is therfore no centre. This also means that there is no sense in which one looks inwards. Looking outwards is also a misleading concept it would be far more helpful to think of it as looking back in time. Any help? Regards Steve
David Barnett, Ph.D. - Galaxies - expansion of the
Robert Poole asks if the expansion of the universe would look the same from everywhere and if so, where was the "big bang"? The answer is "yes" and the "big bang" was everywhere too. The "big bang" name is unfortunate. It conjures up an image of an explosion of matter IN space. This is not what we believe. The only way such an explosion would give us anything like what we observe is if we were at the centre of the explosion. Even then, the distance-speed relation would not be the linear one we seem to. Instead, there is an explosion OF space itself. Every point in space is expanding away from every other point - rather like the expansion of the surface of a balloon when we inflate it. In other words, there is no centre to the expansion within our 3-dimensional space.
David Barnett, Ph.D. - Flat Disk of a Galaxy
Christopher Boulle asks: "why our galaxy has the form of a flat disk and not a sphere?" The short answer is "rotation". All matter attracts other matter. The force gets stronger the closer two chunks of matter approach. If all the matter started off exactly uniformly spherically distributed and stationary it would collapse uniformly into a sphere. But such a special starting condition is most unlikely. First, any areas of slightly greater density will accumulate yet more at the expense of the less dense - the rich getting richer and the poor getting poorer - gas condensing to form stars and stars congregating to form galaxies. Second, the bits of matter are all in relative motion and any slight asymmetry in the velocity distribution will translate into net angular momentum about some common axis. As the galaxy condenses, the rotation about the common axis will speed up due to conservation of angular momentum [just like a spinning skater who draws in her arms]. Now, rotation opposes the gravitational collapse, but only in the directions perpendicular the axis of rotation. Parallel to the axis, the condensation can proceed unhindered. What is more, the rotation opposition becomes more important, the further the matter is from the axis. The net result is a galaxy with a bulge in the centre of a tapering disk. By the way, this same reasoning is thought to explain why the planets in our solar system orbit the sun in the same plane. There are some very small galaxies which do not have appreciable disks - just galactic centres flattened into ellipsoids by their rotation. Not surprisingly, they are called "elliptical" galaxies.
Christopher Boulle: What causes the flat disk?
Can anyone explain why our galaxy has the form of a flat disk and not a sphere?
Robert Poole. Galaxies
OK - so when we look far away with powerful telescopes we are also looking long ago, and seeing galaxies as they were not long after the big bang. But can some expert please explain why we see this looking OUT and not IN? Surely we should be seeing all this back towards the centre and the origin, wherever that is, not on the distant fringes of the universe where everything is moving very fast and far apart? And does this view look the same from everywhere? If so, where was the big bang and how do we know we're getting near it?
S. Gilpin - Galaxies
Perhaps modern scientific ideas are not as new as the scientists believe? A discussion between an expert on Egyptian Astronomy, Aristotle's metaphysics and a modern Physicist would be interesting. It strikes me that Aristotle's "unmoved mover" and black holes have something in common. While I understand that the Great Pyramid has a shaft pointing to the precise spot in the skies where the Pleiades are found. The Egyptians called the Pleiades "Khema" and for a long time this spot was believed to be the centre of the universe around which everything moved!
Catalina Montesinos Brooker, Galaxies
Wonderful programme. I am a blind artist and have found this last programm inmensely rich in imagery. I would like to have a printed version of thesame but I seem unable to print it , is there a way? Catalina
verrall Dunlop All the programmes
I hope one day some of Melvyn's letters which I so enjoy will be published or put on CD or something. I have tickets to hear him at Edinburgh and if I get a chance to ask him i will do so personally. this is what the BBC is all about. BRAVO
Prof. B Linded Universe and everything
Interesting prog, a little dissapointed that the concept of 'The Liquid Universe' was not included. As its the feature in New Scientist last week I hoped it might be covered. Though contriversial it might be worth a prog in the future (perhaps a prog just about contemporary maverick ideas?) Read it- its a curious idea, it might be correct!
C Graham Programme suggestion
There has already been a suggestion of programmes on cultures at the edges of Classical civilisation - Dacia, Trebizond, Armenia. But how about farther east, into Central Asia, the Sogdians, Kushans, Tokharians.
Chaz York - Galaxies
Gosh! What a lot of work M.Stocker put in to point to the 'bleedin obvious' that a scientific theory is just that - a theory! The fact that it is based upon massive observational and mathematical analyis and is widely accepted as a 'factual platform' does not give it the status of fact. Thus the contributors were perfect scientists. They, in their lanuage, did not treat as a 'fact', and in their 'projections' suitably 'watered down' the 'facuality'. This is normal in science - were you expecting a Monty Python answer to 'The Meaning of Life?' Religion and Despots have always used the opposites to what you complain about. For the last six millenia each 'power' has used the obverse of science - they have all depended on faith, but used the narrative of 'certainty, fact, did, done, happened etc.' In short we now have science - it was a huge leap forward, please do not cry for the past.
léo burton...before the universe?
Listening to the discussion certainly makes what is going to have for lunch seem unimportant... I wonder what the panellists imagine existed before the big bang. Was there energy or "nothing". Can "nothing" become matter? Also, would the calcultions on space and time change significantly if, as Rupert Sheldrake suggests, the velocity of light has not remained constant since the big bang?
Mr D Stewart - Galaxies
I would like to hypothesise that if the Big-Bang occured in total darkness, would not the gravitational pull of the density of darkness therefore pull everything in sphere at a maximum speed. The "Density of Darkness" is something that has never been touched on by science but gives good reason for Dark-Matter to be pockets of this density. It would also conclude that the further out towards the edge of the light of the Universe, would be travelling considerably faster than that closer to the centre. - The unobserved partical that machines cannot measure may just be what we can observe with our eyes in the subtlety of shadow... A question I would have liked to have asked (and I think you did Melvin but they didn't answer) is, why do Planets and Galaxies transform into a flat spin. danstewartis@hotmail.com
Dr Colin Wilson - Dark Matter and the Universe
As a possibility for a further programme, dark matter itself is coming under increasing scrutiny from many astrophysicists. The issue is caused by there being two interpretations of the data. The basic fact is that when the gravitational motions of the stars and galaxies are measured and compared with theory they don't match up. When this was first noted the explanation was to postulate that there was more matter that we couldn't see - dark matter. Now this is a reasonable approach but it isn't the only one. Instead one could postulate that the amount of matter we see is correct and that our theory of gravity is not (at least on cosmological scales). Many attempts to find and define dark matter have failed so a growing number of cosmologists are considering this second option. Milgrom and, more recently, Beckenstein have created TeVeS, an alternative gravitational theory that matches local observations (such as Newton's laws or relativity) but dispenses with the need for dark matter on the galactic and super-galactic scale. Various other alternative gravities have also been put forward. This is beginning to cause a major schism in the cosmological community as dark matter has been the prevailing paradigm for many years and most of the older cosmologists have spent their careers searching for it. As a result discussions of the issue can get quite heated. I'm sure I'm not along in wishing to hear the idea discussed by the people currently working on both sides of the debate. They are all capable and well respected scientists and it should be a fascinating (and possibly firework-filled) discussion.
Tom - Galaxies
Halton Arp has shown definitively that the directness of the supposed correlation between redshift and recession should be doubted. Tom Van Flandern has shown definitively that big bang theory should be entirely discredited. I heard not so long ago that a star had been found that is older than the age, according to big bang theory, of the universe...!
Expanding universe- into what?
In reply to Nicky's comment about what the universe is expanding into, I would suggest that space and the universe are seperate entities. Space is what we inhabit but is itself part of a larger (infinate?) universe. Space then expands within the universe. Regards Steve Pond
Scott Morgan - Red Shift
Why has very little time been devoted to the possibility that light loses energy in proportion to the distance travelled from distant galaxies(through interaction perhaps) - thus providing the redshift and background radiation.
M Stocker - Galaxies
"It seems.." "We think..." "We really don't know about the other 96%" "Some of which has been postulated theoretically.." "If we're lucky we may detect some of these particles..." "Dark matter you can't really observe, but we know it's there..." "Maybe you get a lot of matter funnelled.." "This maybe how elliptical galxies are made...this maybe why you get elliptical galaxies.." "However it began..." "We need to find these very early galaxies." "..and if something happens which we didn't imagine.." "And hopefully.." Is Big Bang Theory science or a philosophy of hope?
|
|
