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Posts posted by NowThatWeKnow

  1. As we all well know, the sun and it's system of planets are all products of some supernova that occurred long ago...

    So, does anyone have any idea on where or what type of supernova triggered the birth of our solar system?


    I don't ("As we all well know".) :confused: Why would you think there had to be a supernova for our solar system to exist? Did every star have a supernova? Let me see if I understand this. You have to have a star to have a supernova and you have to have a supernova to have a star. So witch came first, the chicken or the egg? Are you guys that far above my head or am I just tired?

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    Since the molecular clouds from which stars eventually condense are so large, and stars don't maintain their relative positions over time (especially over several billion years, which is what we're talking about), would it be fair to say that the sources of the heavy elements in our own sun could be pretty much be anywhere and everywhere in the galaxy?


    now that makes sense to me.

  2. Communication is the number one reason for the acceleration of technology. Ideas went from delivery by foot, mounted animals, to delivery vessels, to a mailing system, to trains, to airplane, to phone, to video, and finally to internet. And on each step knowledge grew exponentially...


    I could not have said it better so why are you arguing with yourself? :cool:


    Step back and take a breath. You can't see the forest because of the trees. My timeline is not what is important as it ended with "a few thousand years" leaving it wide open. Even if my time line is 99% wrong, on a cosmic scale of time, unimaginable advances will happen in thousands of years, not millions. I can not predict when, and I did not mean to imply that I could. I can also not predict what will happen as my link so well explained.


    In cosmology we deal with a lot of theory and not so many hard facts. If my post have errors based on knowledge you have (include link) please point it out. What I do not want to do is argue speculation.


    Now, if you review that vid again, you might notice it says technical information is doubling every two years. Not knowledge...


    Information is knowledge and knowledge is information. :confused:

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    Not necessarily. No amount of knowledge allows you to violate physical laws. There might simply not be any way to do it, and everything we know now indicates that is the case. I hope there's a way, but there doesn't have to be. The universe isn't obliged to provide us a path.


    I agree with what you say except I do not see "No amount of knowledge allows you to violate physical laws" as an absolute. My screen name comes to mind. What we are doing today is with out question, totally impossible in almost everyone's minds of a few hundred yeas ago. It is also important to remember that if you believe you can not do it, you probably can't.


    Getting accross the universe and breaking the speed of light may be two different things. I do not have the answers but few scientist are ready to give up on traveling the stars.


    Did you watch my link? Most think it is neat.

  3. I would think the mass density (+ space density) of the moving object increases in its reference frame, and the observer's mass density (+ space density) decreases from the moving objects perspective. The observer would just see a small dense object flying by, I think.


    My interpretation of Wikipedia. you can look it up.


    You have "rest mass" and you have "relativistic mass". If you set an apple on a scale you get the rest mass. If the apple flies by you at near the speed of light you combine the rest mass and the energy needed for relativistic speed and get relativistic mass. If you take your scale and hop on the moving frame with apple and weigh it you will have your original rest mass weight. I do not think the apple would actually gain density. You just have to add the energy needed for the motion relative to the observer.

  4. Your list of important events are more achievements than knowledge, made possible by discoveries. I'll agree wholeheartedly that our discoveries are multiplying, perhaps exponentially, but knowledge itself is still near to the same old pace.


    ... If so, I'll hazard a guess that knowledge isn't doubling every two years.


    In a fraction of the time it took to type a reply, you could have watched that short Power Point presentation. It is possible the facts you learn may change you perspective just a little.

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    just had a quick look at the net to see if I could find an answer to the original question. In spacetime, it is currently believed that the universe could be saddleshaped (ie a hyperbola) where space curves back. It is a complicated testable hypothesis that is being worked on. In the larger scheme of the cosmos, though, I think it could be just a weird shaped bubble.


    You can only map what you can see and that happens to be a sphere. Figuring out the current location of what we see today already requires some speculation. Mapping what we can't see is pure speculation.

  5. I'm not sure artillery shell type modelling would work, as the shells don't affect each other, in any way.

    I was saying that you consider the forces that apply to the situation.

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    Real, previously-unknown-to-the-world knowledge does not multiply that easily. At least not apparently.


    Let me guess that you are young because exponential growth of knowledge is apparent to me. However, I am old enough that I served in the Vietnam war. No reply to my last post indicates no interest for one reason or another but I ran into something you may enjoy. It is not absolute proof of what I say but is factually reliable. Watch this short presentation. I am certain you will think it worthwhile.




    Remember the checker board where you double something as you go through the squares. Start with 1 penny on square one and the last square is worth $92,233,720,368,547,800.00


    Wouldn't it be neat to talk to Orville Wright after the first flight in 1903.

    Hi Orville, that flight was amazing. Let me show you a picture of a plane with a wingspan longer then your first flight. Then you really need to see this really neat thing called the space shuttle take off. See that young child over there. She will likely be alive to see man walk on the moon and watch robots collect information from the surface of mars. Hang on, my cell is ringing. Hey, it's my brother. He is standing on the great wall of china and there is a picture he just took. Wires??? Why would you have wires on a phone.


    If you don't see where I am coming from that is OK. The short presentation is still worth it.

  6. For example, when an object accelerates towards the speed of light, doesn't the objects density increase from an observers prospective (+ time slows down)? But the "space" of the object contracts .. Isn't that how it works?

    The density does increase from an observers prospective because you have to combine rest mass and the energy required for relativistic speed to get relativistic mass. Now I am wondering if from the objects point of view the observer is equal to rest mass + energy required for relativistic speed. It would seem that the one under power would be the only one with the increased relativistic mass. Help me Martin.


    Not sure about the rest of the stuff you said.

  7. GR's answer is that you shouldn't think of space expanding. You should concentrate on the distance function, the metric. You are encouraged to think of distances expanding. Without attributing any material existence to space. Severian said this rather clearly at the outset....


    I understand what you are saying but I pointed out a few of the many things that seem to contradict it. The first paragraph explaining GR has in it

    "the observed gravitational attraction between masses results from the warping of space and time by those masses." So when we witness gravitational lensing we are warping a metric of nothing (space and time) but still get results. Does that make sense to you?


    We can consistently prove mathematically that space can be bent by gravity. That should be good for a theory showing space has some unknown fabric. There are plenty of photons, gravity and maybe some kind of web or dark matter/energy.


    Beside that, you told me in another thread that "I would urge you to stick to sources that are no more than 4 or 5 years old." GR is a little out dated. :D


    I also recently read Frank Wilczek's new book The Lightness of Being.

    He thinks there is an underlying physical existence to the vacuum and this can be made to include GR...


    I knew it.

  8. Perfect. Now I know who to ask to cover for me, if I want to take a week off!


    That is a nice compliment, especially from you. :D However, you supplied the tool for may answer. Not all my post get a gold star though. :doh: It was kind of neat that we both addressed star vs galaxy and drift vs expansion but you addressed the question from a teachers point of view.

  9. ... Weather imo is actually quite a good example of how bad we are at this kind of system, some of the worlds most powerful supercomputers are devoted to solving it, and we can't predict weather accurately to a town and time. How often are the forecasters wrong?


    Maybe we should look at predicting galaxy movement more like an artillery shell then weather. Artillery can be very accurate when considering wind and distance. In space we consider gravitational lensing and transverse movement from local gravitational forces. But like you said "I don't quite see what you'd hope to see from this".


    I think an accurate current map of the observable universe every so often is all we need right now. With that we can calculate the likely current or future location of any galaxy.

  10. I seriously doubt it. Or even that knowledge doubles every few years.


    Do you have a source for your claim by the way?


    Do a google search "knowledge doubles every" and see what you find. Medical knowledge doubles ever 14 months and other knowledge at different rates. Artificial intelligence will accelerate knowledge significantly in the near future.


    There is some speculation in what I said but I base it on the rate knowledge increases and looking back through history. Think about what we have done in the last 100 years compared to the last 1000 years. How about computers in the last 30 years. I predict that if things continue we will be unimaginable in a few thousand years.

  11. If we can find a way to ride the space expansion, bingo -- we travel faster than light speed without violating any physical laws. And conveniently, it'd be a two-way mode of travel.


    With knowledge doubling every few years and accelerating we will figure out a way to get accross the universe.


    In 60 years we will have 1.5 million times as much knowledge as today.

    In 75 years we will have 12 million times as much knowledge.

    In a few thousand years we will be GOD, created by the universe. then we will travel in spirit form when needed.


    Unfortunately something will probably kill us off before we make it that far.

  12. When a star is said to be five billion LY away is the distance the star has drifted since that light left the star figured in. if not how far would the star really be if drift was accounted for.


    It would be more likely that we would be looking at galaxies that far away rather then stars. Either way, light from a star that took 5 billion light years to make it to us was sent when the star was 4.09 billion light years away and is currently 6.137 billion light years away from us. These #'s are because space had an expansion factor of 1.5 at that distance. There may be some "drift" because of local gravitational effects but it would probably not be significant.


    Edit - I see Martin beat me to it. :)

  13. Doesn't mapping the universe in "real time" have a problem with the relativity of time?


    Isn't "A billion light years" from here "real" time there measured in time units and standards from here?


    There are calculators that will give you past, current and future locations of galaxies from the red shift measurements. With billions of galaxies it would be a monumental task. Any gravitational lensing and transverse movement would also be a problem to predict.


    The light from the distant galaxies we see today are now far enough away that we will never see their current light (Unless expansion reverses). They could be zapped from space today and we would never know the difference so is there a need to map those? Then there are probably the galaxies that are already too far away to see.

  14. Tom C,

    what Severian says here is precisely the idea of space and time we have from classic vintage-1915 General Relativity. GR is still the best theory of spacetime geometry and gravity that we have. I don't see how what Sev says could be improved, as a concise statement.


    Is a particular piece of matter at rest in space or is it moving through space is the real question. If there is a difference, or space is expanding, then there must be a fabric of space but we have not been able to define it yet. Space must be more then just a yardstick.


    A couple of things tell me there is a so called fabric of space. If we look at the balloon with dots explanation of the expanding universe, it would be hard to imagine that matter set in motion could explain what we observe. It seems space is expanding and most matter is at rest in space.


    E=MC^2 tells me that it takes a lot of energy to move matter at Relativistic speed through space. This shows there is a difference between between resting in space and moving through it. I do not think Relativistic speed can be maintained relative to a current location with out energy. Therefore there must be a fabric of space. The teaser is what is the speed relative to. Since space is expanding, speed is only relative to its current location in space.


    Looking in opposite directions we can see galaxies moving away from us at close to the speed of light. Their separation speed relative to each other well exceeds the speed of light. Special relativity says matter can not break the speed of light so space must be expanding. If space is expanding then there must be a fabric of space to expand.


    Where am I going wrong?

  15. You also mentioned 6 billion years. What z corresponds to that? What current distance?


    Your spoiler gave it away but z=.66 and current distance is 7.782 Gly. That is one neat calculator, thank you very much. I plugged in many #'s and came up with a lot of great info. Our current observed universe has actually gotten quite big. I can also see where it would be much more crowded with galaxies billions of years ago. There is no reason to believe that the universe we see is all there is but it can predict the size of the known universe at different times. I went back to the big bang and came up with an expansion factor of 865. I am sure it was not designed for that.

  16. Dear NowThat,


    I would urge you to stick to sources that are no more than 4 or 5 years old.


    Good point. Things are changing quickly. Hence the name "NowThat We Know" (will bite you in the @$$ every time).


    Try Einstein-online. It is up-to-date. The link's in my signature...

    We don't know whether the volume at putative big bang time was finite or infinite. If finite, we have no idea of the size...


    I did go to Einstein-online and I gathered we really do not know the size of the universe in the beginning or now. Good site and I will read more later.


    When you say

    "Distant galaxies we observe today are ...where they were 12+ billion years ago."

    do you mean these objects are still at the same distance from our Milkyway galaxy material?


    Where they were 12+ billion years ago and where they are to day are very different locations as you pointed out. I am sure there current light is permanently off our radar screen because of the expansion of space


    The bottom line is is we do not have the answer to my question. If we went back 6 billion years in time I wonder how we would see that same distant galaxy? Need to think on that for a bit.


    Thanks for your reply.

  17. I am familiar with a balloon covered with dots being used to explain Hubble expansion and I am not trying to defend "singularity". The universe is expanding so in the past it must have been smaller. The size of an atom, our solar system, the milky way or a 12 billion light year radius chunk of space that we observe today.


    It sound like you are saying that distant and infant galaxy 12 billion light years away started there at the time of the big bang and is expanding from that point. I would have thought the red shift would indicate it is moving away and was closer then that in the past.


    My question now is does any one have a clue how big the universe was (give or take a million light years) at any given time shortly after the big bang? Reading about inflation does not leave me with a visual of galaxies popping out all over a space billions of light years accross in a fraction of a second. Where am I going wrong?

  18. Thanks for your reply. It is hard for me to wrap my head around this stuff.


    According to your link:

    "...all of the observable universe originated in a small causally-connected region..."


    Inflation for Beginners" website says:



    "Inflation expands the Universe from a size much smaller than a proton to 10 cm across in only 15 x 10(exp-33) sec. This is possible because it is spacetime itself that is expanding, carrying matter along for the ride; nothing is moving through spacetime faster than light, either during inflation or ever since."


    Could you please point me to a credible theory that explains "the big bang didn't happen at a single point in space but at every point in space at the same time." That would explain why a 1 billion year old universe could have been 24 billion light years accross. Our current observed expansion would not allow it. Our current observed expansion would also, if put in reverse, bring all matter back to one place. I thought the uniformity of the universe was due to all matter being together at one point. Maybe the key is figuring out what size the universe was when the rapid expansion of inflation stopped.

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