Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scotty234 on 15/09/2005 21:52:54
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Do you mean, "How long did it take for galaxies to form, and to have a night sky with the same "shape" as we see today?"
That answer is still being sought. We can see back about 13 billion light years and there seem to be plenty of galaxies. The age of the universe is about 14 billion years. So there were definitely galaxies, and a normal looking night sky 1 billion years after the big bang.
Here is a link to the most remarkable image ever taken of the sky. It the Hubble Ultra Deep Field view, and is a 280 hour time exposure from the Hubble Space Telescope.
http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/07/
The second question has an answer much less palatable: The universe got into place VERY quickly with super-luminal expansion. In the beginning, the expansion went through a period known as "inflation" which was a hyper-fast expansion that could not happen today. However, it is still expanding at super-luminal velocities today. How is this possible, when the fastest speed possible is the speed of light? The short answer is that cosmic recessional velocities are caused by the expansion of space itself. Across the universe, space is not "flat", it has a curvature, which has been changing throughout time. Somewhat like a rising loaf of raisin bread carries the raisins apart from each other, even though the raisins do not move through the loaf, the expanding curvature of space carries galaxies apart from each other faster than light, even though their own motions are slow. Here is another link that begins to explain some of this subject:
http://www.astronomycafe.net/anthol/expan.html
Once again, you could Google on "faster than light recessional velocity", and see another 74,999 hits. You can also Google on "cosmic inflation" and get 467,000 hits. This is a fascinationg subject, although very technical.
Your last question has no authoritative answer from science. We don't know what happened before time. There are some ideas about the "multiverse" that speculate on the subject, but I know of no scientific explanation.
"F = ma, E = mc^2, and you can't push a string."
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Suppose that your ancestors had possessed a formula for manufacturing swords of unmatched quality and caliber. The formula was handed down by word of mouth through the ages and when finally you took up the noble art , you found that some of the vital ingredients in the sword making process were lost and that the swords you produced no longer had the same qualities as the original swords. After many attempts and many failures , you stumble across the notes which your ancestors had kept on the sword making process . On studying these notes you realize that several key ingredients and processes were missing from the method you were currently using . What would you do ? Would you alter the whole sword making process or would you like Winnie – the – pooh might have done , just stick things on in any order , on the finished product , with the result that the device that is left is quite weird . It seems to me that in our study of physics we have erred in the manner of Winnie – the – pooh. We formulated a theory of electricity without having any knowledge about photons , and stubbornly stuck to the theory , in spite of every evidence to the contrary , even after the existence of photons had been verified. What is electricity ? The answer is that electricity when we are not referring to , electrical induction ( which is to do with electromagnetic fields ) , has to do with heat. What is heat , it is , as has been verified by observation and experiment , the energy released due to the vibration of atoms and molecules when the electrons of the former absorb low energy photons and rebound from the nucleus. So what in heaven’s name do electrons have to do with electricity , since it is photons and not electrons that are involved in the production of heat ? One frequently given reply to any criticism is : “But it works.” Of course it works , it has worked since Drude and Lorentz first developed an electrical theory in 1900 , when even the charge on an electron was not known or the structure of the atom. The reason it worked is that calculations were made on the basis of tabulated results and not due to the veracity of any theory. I feel the same criticism still holds good. As long as photons are not included in any theories of electricity and electromagnetic radiation , the theories would be faulty.
Because we had resolutely decided to stick with our theory of electrical conduction by electrons , it was now very difficult to explain the phenomenon of electromagnetic radiation , how could we explain this radiation , seemingly identical to light which is made up of photons , without the use of photons. In the end it was decided to explain the phenomena of low energy electromagnetic radiation as being due to “virtual” photons. Even more strange are the reasons given for the manner of propagation of these “virtual” photons. It is held that a virtual photon is formed by the vibration of atoms and ions in the crystal lattice structure , coming into contact with slow moving electrons. What happens next is bizarre , the “virtual” photons spontaneously give rise to electron-positron pairs which in turn annihilate themselves , once more giving rise to a “virtual” photon. Does this make sense. How do these “virtual” photons function with the process of electrical induction , they are supposed to be virtual because (a) they lack enough energy or (b) are too short lived to attract the laws of conservation. Right when this is brought up , the physicist immediately retreats to the tried and tested position of Maxwell’s equations. But here again we return to the original question , how is electricity conducted , since electrons possess a drift velocity of only fractions of a cm / sec , while a current is established near to the speed of light. The answer of course is that electricity has to be conducted through the wire by fluctuating electric and magnetic fields. What then is the displacement current ? And where do photons come into it ? The point I am trying to make is , that perhaps it would be wiser to rethink our ideas about basic concepts , before attempting to explain the Universe. If our theory of electricity and consequently of electromagnetic radiation is flawed , it is possible that even our understanding of gravity might be severely deficient.
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They are galaxies. The furthest and dimmest are 13 billion light years away.
"F = ma, E = mc^2, and you can't push a string."
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quote:
Originally posted by McQueen
Suppose that your ancestors had possessed a formula for manufacturing swords of unmatched quality and caliber. ... If our theory of electricity and consequently of electromagnetic radiation is flawed , it is possible that even our understanding of gravity might be severely deficient.
This reply is off-topic.
"F = ma, E = mc^2, and you can't push a string."
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And its only a tiny piece of the sky, no bigger than what your thumb would cover up if you held it up in front of you
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In physics there is a strange concept of "something" forming from "nothing" that is, a "vacuum" appears to be more active than our usual determination and having a positive level of energy and capable in expressing fluctuations in matter formations. This would generate an even more obfuscating question as to how this "vacuum" first originated along with these "rules" of fluctuation--all of which lead to our present universe.
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"In the beginning there was nothing, which exploded." T Pratchett
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Gsmollin
My apologies. I guess , given the grandeur of the moment my post was out of line. It is an amazing picture , truly awesome. Each of the little whirls and almond shapes represents a galaxy as big as the milky way , it is quite stunning. Even more remarkable is the fact that light from these galaxies has been traveling towards us for the past 15 billion light years. I have been doing some calculations. Light travels approx. 9.5 x 10 ^^ 12 Kms /year therefore in 15 billions years it would travel approx 1.5 x 10 ^^ 23 Kms. which is truly amazing. If we consider the source to be an isotropic radiator , then very roughly it would need 7.5 x 10 ^^ 40 W. to get a millionth of watt reception in the vicinity of the earth. The sun produces about 4 x 10 ^^ 26 W , if we take the number of stars in the Milky way ( approx. 10^^ 11 stars ) as being representative then we have 10 ^^ 37 W. If we factor in the amount of time for which this source has been radiating it seems to be just possible. It is mind boggling , an unbelievable sight.
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Ah, but our picture of those galaxies is 13,000,000,000 years old and those galexies may no longer be radiating, and especially not at that level. I will swing by there and check the next chance I get.[:)]
David