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Thread: another valid question

  1. #1 another valid question 
    Forum Sophomore Brandon's Avatar
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    How can the universe have an age? how is the age of the universe determined?


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  3. #2  
    Forum Sophomore Brandon's Avatar
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    Wow intellect is an illness now? And I'm considered a crack pot for trying to think of any new ideas about space time.. somehow a mod didn't delete that.. cool I guess.. I see the point of the microwave background, but how can microwaves really tell us the age? By the left over decy of heat signatures? Or is there still more? Why to mentioned you wrote a book I don't really care. Take it to another forum...


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  4. #3  
    Forum Radioactive Isotope MagiMaster's Avatar
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    When we look out at the universe and make careful measurements of the position and speed of all the galaxies around us, we see that they're moving in a particular pattern. If we reverse that pattern and work backwards, we see that everything was in one place around 14 billion years ago.

    Since that discovery, other ways of determining the age of the universe have given the same answer, which reinforces our certainty in its correctness. We don't really know that there was nothing before that, but it would have been something different in any case.
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  5. #4  
    Forum Sophomore Brandon's Avatar
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    I think, straight guess with no proof. 100 bil. years old. Mainly because it would take near infinate time to create near infinate space.. I think instead of calculating the theory of qp an gr. Calculate the exact relationship of space time. Time is created or percieved at the rate at which space is expanding. Very hard to measure tho haha
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  6. #5  
    Forum Bachelors Degree x(x-y)'s Avatar
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    By measuring the red shift of galaxies we can determine how quickly they are moving away from us; we use the relationship



    where v is the recessional velocity, H0 is Hubble's Constant and d is the distance the observed galaxy is away from us. You can work out the value of Hubble's constant from this, and other methods are used too, which allows you to roughly calculate the age of the universe:



    which works out to around 13.7 billion years.
    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
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    Forum Sophomore Brandon's Avatar
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    So the age of the visable matter in our universe is 13.7 billion years old?

    Is there any QP that determine the age of physical matter?
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  8. #7  
    Forum Radioactive Isotope MagiMaster's Avatar
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    It likely wouldn't be a meaningful estimate of the age of the universe, since matter can be created and destroyed. Mass-energy is conserved, but any transformations would erase any measurable age.
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  9. #8  
    Forum Sophomore Brandon's Avatar
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    Thank you magi. very simple and understanding answer haha.. i like those answers hahaha
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  10. #9  
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    Quote Originally Posted by MagiMaster View Post
    When we look out at the universe and make careful measurements of the position and speed of all the galaxies around us, we see that they're moving in a particular pattern. If we reverse that pattern and work backwards, we see that everything was in one place around 14 billion years ago. Since that discovery, other ways of determining the age of the universe have given the same answer, which reinforces our certainty in its correctness. We don't really know that there was nothing before that, but it would have been something different in any case.
    It was not quite that easy. The first estimates came back with an age of about 2 * 10^9 years, way too short fort the Earth to have formed, cooled, and given rise to the organisms we see today. Only somewhat recently has there been good estimates of the factors governing expansion. Fortunately, there are different methods for doing this and they all tend to agree.
    Quote Originally Posted by x(x-y) View Post
    By measuring the red shift of galaxies we can determine how quickly they are moving away from us; we use the relationship where v is the recessional velocity, H0 is Hubble's Constant and d is the distance the observed galaxy is away from us. You can work out the value of Hubble's constant from this, and other methods are used too, which allows you to roughly calculate the age of the universe: which works out to around 13.7 billion years.
    Yeah, this doesn't work out close to this number. Without something driving expansion to accelerate, the number is significantly lower, low enough to cause serious problems with the age estimates of stars and galaxies.
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  11. #10  
    Forum Sophomore Brandon's Avatar
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    That's kinda what I was thinking but I am not a physisct. I was thinking about the time it really takes for a black hole to consume 1 billion suns, in some esimates of black holes. It seems like the age of our visible universe is older than 13.7 billion years. I just now thought, could we be lookin at a time paradox? Since the universe was much smaller and had higher gravity waves, time would be extremely distorted in our perspective. What would the time paradox theory estime the age of the universe at?
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  12. #11  
    Forum Radioactive Isotope MagiMaster's Avatar
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    A 1 billion solar mass black hole never consumed 1 billion suns. Only 1 billion suns worth of matter. Supermassive black holes like that are found at the center of galaxies and are thought to have formed along with the galaxy itself, consuming massive quantities of dust and gas from the proto-galaxy.
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  13. #12  
    Forum Sophomore Brandon's Avatar
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    ah I see. But that would mean that the very first stars going supernova are likely to be the origin of those massive black holes in the center. They would only have maybe 100 solar mass and have to grow to a billion or more. There would be other black holes that merge with it, but it still seems like it would take a lot longer for every phase of the creation to fit in place. But that's just my ignorant guess. How do we know what the exact temp of the bb? is it even possible in a lab yet to recreate that temp?
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  14. #13  
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    Quote Originally Posted by Brandon View Post
    That's kinda what I was thinking but I am not a physisct. I was thinking about the time it really takes for a black hole to consume 1 billion suns, in some esimates of black holes. It seems like the age of our visible universe is older than 13.7 billion years. I just now thought, could we be lookin at a time paradox?
    Don't think of the time it takes for a black hole to consume 1 billion suns. Think of yourself as being at a black hole event horizon, then ascending up into free space. There's a space-time parallel between this and the expansion of the universe. In one situation the black hole stays put and you move outward. In the other situation, it's like the black hole is the whole universe, and it moves outward by expanding whilst you stay put.

    Quote Originally Posted by Brandon View Post
    Since the universe was much smaller and had higher gravity waves, time would be extremely distorted in our perspective. What would the time paradox theory estime the age of the universe at?
    If you say the early universe was very small and dense, something like the "frozen star" black hole interpretation, then there is a scale-change that applies to time. At a black hole event horizon you'd be subject to infinite gravitational time dilation according to outside observers. If you were in the middle of this black hole, you wouldn't feel any gravity, just as you wouldn't feel any gravity in a void at the centre of the earth. But you'd still be subject to the infinite time dilation, and effectively frozen. It would take you forever as measured by me to do anything. In the early universe likened to this black hole scenario you'd be subject to the same infinite time dilation. There's no paradox to this, but on that basis the age of the universe could be infinite. Or maybe it's better to say non-defined. If it helps any, think about working out the age of a clock that's ticking faster and faster. You can maybe work out that the clock started ticking 13.7 billion years ago. But that doesn't actually tell you the age of the clock, or why it started ticking. In similar vein we can only go back so far with the big bang.
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    There are a lot of misconceptions based around the notion that time might have passed at a different rate, earlier in the history of the universe, and one of those misconceptions is that the "true age" of the universe would be larger than we measure it to be today.

    The age of the universe is basically the elapsed time on a clock that was started when time began, and continued to tick until today. A second always lasts a second. But when we compare a second today with a second in the past we find cosmological time-dilation - the further in the past we look, the more time seems to be stretched. However, this does not mean that our current age for the universe is wrong.

    It doesn't matter that events that occurred during, say, 1 second when the CMBR was emitted, would be seen today to last 1100 seconds. Those events took a second, when they happened. The cosmological clock adds up to 13.7 billion years, and that is how many seconds have passed in the universe.
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  16. #15  
    Forum Sophomore Brandon's Avatar
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    I think I understand speedfreak. We percieve 13.7 but with the time dialation more thinks could of happened "faster" considering the time dialation is near impossible to predict exactly. So bb, perception of time is slow, but the energies inside do not feel this and act as normal, therefore getting a lot more done relitive to our perspective of time..? Kind of like the time paradox of falling into a black hole, its all based on where antoher human is watchin from to determine exacly what is happening.
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  17. #16  
    Quagma SpeedFreek's Avatar
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    That sort of sounds right, in a round about way!
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  18. #17  
    Forum Sophomore Brandon's Avatar
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    That's weird though.. the reason for the event horizon is light can not travel through time.. maybe the gravity pulls the light in, but the perception of time doesn't let it out.. awesome thought.. it took me a while to put it into words. So this could explain why our percepton of time is useless in trying to age the universe.. I don't know.. that's hard to grasp.. but explains a black hole better I think?... so if we didn't apply the time dialation the universe would be much older from our perspective of time on earth? But with space time being streched time is actually speeding up relative to space expanding.. so time was much slower then. So the speed of light was actually faster in the past. From our perspective.... crazy.. am I even making any sence?? Haha
    Last edited by Brandon; September 15th, 2011 at 12:50 AM.
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    That's the wrong way round, Brandon. The speed of light would have been slower in the past. But if you'd have been there, you wouldn't have noticed it. It's like the situation with gravitational time dilation. A second down near the surface of a planet is bigger than a second at some higher elevation. The metre is unaffected, because the slower light and bigger second cancel each other out. That means the 299,792,458 m/s near the surface isn't the same as the 299,792,458 m/s at a higher elevation. It's less. But locally you can't tell. You always measure the local speed of light to be 299,792,458 m/s. It's a bit like being a character in a movie. You can't tell how fast the film's being played. Not until you start thinking about inflation. Imagine the universe is expanding at a constant rate, but early on, the speed of light is slow. You don't notice that the speed of light is slow. But the constant-rate expansion wouldn't look constant. The expansion would look as if it was faster early on.
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  20. #19  
    Forum Professor wallaby's Avatar
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    Quote Originally Posted by Farsight View Post
    The speed of light would have been slower in the past. But if you'd have been there, you wouldn't have noticed it. It's like the situation with gravitational time dilation. A second down near the surface of a planet is bigger than a second at some higher elevation. The metre is unaffected, because the slower light and bigger second cancel each other out.
    Light does not change the speed at which it propagates, not in a gravitational potential, expanding universe, or in any other case. Gravitational fields distort spacetime intervals, not just space or just time, as such light leaving the gravitational field of a planet will do so at the same speed as measured by the sender and a receiver. The time dilation effect will result in a frequency shift. This same effect occurs as a result of the expansion of the universe, over billions of years what was once gamma radiation becomes microwave radiation.
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    I'm afraid it does, wallaby. One 299,792,458 m/s isn't the same as another. I know people say the speed of light is constant, but that's the locally-measured speed of light. Take a look at wiki and the parallel-mirror light clock used to explain time dilation and special relativity. Then apply the principle of equivalence and think gravitational time dilation, taking a look at this report on a super-accurate optical clock. It's so precise that you can see two of these clocks losing synchronisation when they're separated by only a foot of vertical elevation. When you simplify the optical clocks to parallel-mirror light clocks held parallel to the ground to avoid issues with radial length contraction, then when they lose synchronisation this is what's happening:

    |--------------|

    |--------------|
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  22. #21  
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    Light travels at c no matter who measures it (no matter what frame of reference is used). This is core Relativity theory which Einstein deduced -- it is necessary so that Maxwell's Equations are the same no matter what frame of reference is chosen. After all, that is basically what Relativity says: All physical laws will be the same no matter what frame of reference is chosen.
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    True, pumaman. I'd say the important point we're talking about here is the bit in Lorentz covariance - Wikipedia, the free encyclopedia
    that says: Local Lorentz covariance, which follows from general relativity, refers to Lorentz covariance applying only locally in an infinitesimal region of spacetime at every point. You measure the speed of light one one elevation within the room you're in, and it's 299,792,458 m/s. You measure it at a higher elevation and it's still 299,792,458 m/s. But there is no inertial reference frame that spans the whole height of the room. You're in a non-inertial frame, and the light-clocks losing synchronisation is displaying a difference in what's usually called the coordinate speed of light. There's a reference to it in Comoving distance - Wikipedia, the free encyclopedia where you can read: Even in special relativity the coordinate speed of light is only guaranteed to be c in an inertial frame, in a non-inertial frame the coordinate speed may be different than c.
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  24. #23  
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    I understand now. So, since space/time are ever so connected. when the earth has gravity, it is slightly contracting space time, which effects all matter around it. Whichs leaves me to further conclude about my old idea, in oder for a black hole to slow down time due to its gravily, leads me to think that black holes consume space, and time. They do not only consume matter but space time as well.. since perspecive of space and time are equal it now seems very possible to shrink space inside a black hole., which causes time dialation. But the million dollar question is, if space is contracted in a black hole, it could hold a lot of matter, but when new matter falls in, it consumes a huge amount of space to put it somewhere, as it pulls in space time, it also pulls in more matter (a disgusting cycle) but when the black hole gets more matter than it can make space for it blows off a huge gama ray burst..?? Essentially it needs to consume more space than matter, and when the load is too much a gamma ray burst is seen across the universe....
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    Forum Professor wallaby's Avatar
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    Quote Originally Posted by Farsight View Post
    Even in special relativity the coordinate speed of light is only guaranteed to be c in an inertial frame, in a non-inertial frame the coordinate speed may be different than c.
    Point taken...also Propagation of light in non-inertial reference frames - Wikipedia, the free encyclopedia.
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  26. #25  
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    Quote Originally Posted by Brandon View Post
    How can the universe have an age? how is the age of the universe determined?
    There's not such a thing as age of the universe. But we can talk about age of the materialized part of the universe which is known (within some approximation).
    I had a dream that on my yard a UFO landed but when I woke up, they hadalready gone
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