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Re: a universe from nothing
[Re: MMike]
#340085
08/31/10 18:11
08/31/10 18:11
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Joined: Oct 2006
Posts: 1,245
AlbertoT
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Joined: Oct 2006
Posts: 1,245
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My only question is, what is the boundary of the universe if its infinite? how can something have no limit? if its finite, what is the wall that make the universe apart from the otherside?
Well Mr Krauss answered also this question The terms "wall" or "boundariy" assume that you can watch the universe from "outside" but in the theory of relativity it does not make sense to speak of something "outside" the Time-Space Dont think that I really understand what I wrote one line above Modern Physics is not intuitive but it is supported by experimental evidence
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Re: a universe from nothing
[Re: Damocles_]
#340087
08/31/10 18:23
08/31/10 18:23
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Joined: Oct 2006
Posts: 1,245
AlbertoT
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Posts: 1,245
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So as long as there is no direct proove, dark matter" and "dark energy" are just theoretical implications.
well if you mean that the existance of dark matter and dark energy has not been proved yet beyond any reasonable doubt, it is ok but you can not put the 3 alternatives on the same level As I told in my previuos thread the existance of the energy of vacuum is a direct consequence of the Heisenberg's principle of indetermination Kasimir proved in lab that it should really exist Just a few years ago the acceleration of the universe seem to confirm that this strange form of energy is actually is diffused everywhere Pure coincidence ? faulty observations ? Well in theory it may be but alternative a ) is definitely the most likely hypothesis Direct proves are almost impossible in the modern physics but indirect proves are considered as valid as the direct ones
Last edited by AlbertoT; 08/31/10 18:28.
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Re: a universe from nothing
[Re: ventilator]
#340098
08/31/10 18:59
08/31/10 18:59
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Joined: Aug 2003
Posts: 7,439 Red Dwarf
Michael_Schwarz
Senior Expert
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Posts: 7,439
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a thing i didn't quite get... do all supernovae have the same brightness? or what exactly is this standard candle he was talking about? Excerpt from Wikipedia ( http://en.wikipedia.org/wiki/Standard_candle#Supernovae) Type Ia SN (Super Novae) are some of the best ways to determine extragalactic distances. [...] Because all Type Ia SN explode at about the same mass, their absolute magnitudes are all the same. This makes them very useful as standard candles. [...] Therefore, when observing a type Ia SN, if it is possible to determine what its peak magnitude was, then its distance can be calculated. [...] Using Type Ia SN is one of the most accurate methods, particularly since SN explosions can be visible at great distances (their luminosities rival that of the galaxy in which they are situated), much farther than Cepheid Variables (500 times farther). Much time has been devoted to the refining of this method. The current uncertainty approaches a mere 5%, corresponding to an uncertainty of just 0.1 magnitudes.
Last edited by Michael_Schwarz; 08/31/10 19:06.
"Sometimes JCL reminds me of Notch, but more competent" ~ Kiyaku
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Re: a universe from nothing
[Re: Michael_Schwarz]
#340101
08/31/10 19:21
08/31/10 19:21
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Joined: May 2002
Posts: 7,441
ventilator
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OP
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makes sense but is it easy to figure out how old the supernova is? or what state it is in? Therefore, when observing a type Ia SN, if it is possible to determine what its peak magnitude was, then its distance can be calculated. this is what i mean. how is it possible to figure out the peak magnitude? "what if the universe already plays tricks like that on us now?" I think this can't be the case, because we see the microwave background, which is 14 billion light years away, and the universe is 14 billion years old. So there can't be anything invisible to us that was visible before, because it was never possible to look beyond the microwave background. i mean in general. not specific to the age or something. ...what if something else has happened already that distorts the observation of the universe's true nature?
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Re: a universe from nothing
[Re: ventilator]
#340102
08/31/10 19:32
08/31/10 19:32
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Joined: Aug 2003
Posts: 7,439 Red Dwarf
Michael_Schwarz
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makes sense but is it easy to figure out how old the supernova is? or what state it is in? Therefore, when observing a type Ia SN, if it is possible to determine what its peak magnitude was, then its distance can be calculated. this is what i mean. how is it possible to figure out the peak magnitude? You could just read the Wiki link It is not intrinsically necessary to capture the SN directly at its peak magnitude; using the multicolor light curve method (MCLS), the shape of the light curve (taken at any reasonable time after the initial explosion) is compared to a family of parameterized curves that will determine the absolute magnitude at the maximum brightness. This method also takes into effect interstellar extinction/dimming from dust and gas. Similarly, the stretch method fits the particular SN magnitude light curves to a template light curve. This template, as opposed to being several light curves at different wavelengths (MCLS) is just a single light curve that has been stretched (or compressed) in time. By using this Stretch Factor, the peak magnitude can be determined.
"Sometimes JCL reminds me of Notch, but more competent" ~ Kiyaku
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