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Author | Topic: Doesn't the distance of stars disprove the young earth theory? | ||||||||||||||||||||||||||||||||||||||||
cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
but I'm wondering whether this conclusion is true if we take into account relativity? Distant events already appear to proceed more slowly by virtue of the cosmological expansion/red-shift. If you think about it, that is exactly the cause of red-shift: the peaks of your light wave are arriving further apart than when they were emitted, so you are seeing the light wave "slowed-down".
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
So I guess that means that the rotation speeds we measure for distant pulsars are actually higher in reality? Not usually - most pulsars we examine are not sufficently far enough away to have a dominant cosmological red-shift. The local motion of the pulsar will be a more important factor to take into account. But a distant pulsar, say 100MLyr away, would definitely have a noticable cosmological slowing.
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
The speed at which an object moves from one location to another does not effect the time continuom, in fact, speed will only determine the how fast the object moved from one location to another. There is no "time" continuum. Passage of time is unique to each individual object that travels. And the speed that an object travels has a direct impact on the time experienced by that object. This is the most basic most obvious (4-dimensional) geometry - time experienced is the length of the 4-dimensional path through space-time - and to argue against it is the very essence of stupidity. Every particle accelerator in the world is built taking into account the very fact of time dilation. Guess what? They work.
If time dilation is defined as moving faster equals less time of travel then it is true. No, it is not defined as this. And it is very much true. And is demonstrated 100% true every second of every day that particle accelerators are in operation.
If you're saying I moved so fast in that direction...that I saw the prehistoric Earth...you are wrong...Time did not dilate for you...but the distance for which you have traveled has increased greatly... Time-dilation has nothing to do with seeing the prehistoric Earth - you seem very confused by all of this. Observations of the Moon show the Moon as it was about 1 second ago. The radio delay when the Apollo missions transmitted their communications demonstrates this without question. We see the Sun as it was 8 minutes ago. If it explodes, we won't know until 8 minutes later. With Jupiter, the situation si even more pronounced - and radio signals from our probes can take an hour or more to arrive. When we observe a star at 8000 light years distance, then we are seeing it as it was 8000 years ago. This is the most basic physics, and has nothing to do with time dilation.
You will be seen as the village idiot when you argue these facts in a scientific setting... I'm fairly sure that most of the members of EvC are safe from such accusations. You on the other hand may want to avoid such an environment...
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
the observable universe is 13.5 billion years old by the travel of light. Could our observable universe be part of a larger spacetime that is much older? Many theoretical physicists believe so, some don't. Not quite. The Observable Universe is almost indisputedly part of a much larger space-time, even without inflation. With inflation, it's an unbelievably small fraction of the whole Universe. And there's a good chance the Universe is infinite in extent, in which case what we can see is essentially 0% of what there is! Also virtually indisuptable is that 13.5bn years ago, the Observable Universe was contained within the volume of an atom. Even if the Universe does extend further back past where we usually place the singularity, the Universe has still passed through this "squeeze point".
heck out the wiki page on De Sitter Universe. In this type of universe there is an event horizon which is defined by the expansion of space where the expansion adds up to the speed of light. To be clear, there is no one event horizon in de Sitter Space - every observer has his own horizon. This is unlike the single horizon of a black hole.
Radius. It is 13.5 billion light years in all directions. No, this is a common misconception - understandable, but you need to appreciate the added complexity of our observations being constrained by the speed of light. As we observe further, we are observing the Universe at earlier and earlier times, when it was smaller and smaller. The expansion is also not a velocity and hence not constrained by the speed of light. You may want to ask "how big is the Observable Universe *now*, even though we cannot see it as it is *now*?" The answer is about 46 billion light years in radius.
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
Based on those numbers, how big would our sun have been 4.5 billions years ago? Percy's numbers were not refering to the Sun so largely irrelevant. 4.5 billion years ago is a bit vague so could catch the Sun at various stages from enormous coalescing gas cloud to proto-star to early stages of the Sun proper. This covers a huge range of sizes. BUT the mass would have been the same (within a couple of %) at all stages including today, and it is mass that dictates the lifetime, not volume.
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
Are we limited to seeing only 13.5 billion light years due to a technical limitation? At the moment, we cannot see beyond the "surface of last scattering", which is the point when the Universe went from opaque to transparent. Before this time, the Universe was filled with a proton/electron plasma, hence photons had a very short mean free path. As the Universe cooled, the electrons and protons combined (hence "recombination")to form neutral hydrogen, and the photons were now free ("decoupled") to travel unhindered through the Universe - "vision" became possible. The first photons to fly free form the Cosmic Microwave Background Radiation (CMBR). This occured 13.5 billion years ago, about 400,000 years after the Big Bang. This will always be the limit to our electromagnetic observations (visible, IR, UV, radio, X-ray, etc). There was a much earlier decoupling when the Universe's density decreased to the point that neutrinos could suddenly travel freely. So there is an analagous Cosmic Neutrino Background Radiation there for the detection which will represent an observation of the Universe at a far earlier stage than the CMBR. But we're probably a few thousand year's of technology away from being able to meaure it!!
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined:
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Sorry to dredge this up again, not sure where else to ask. No probklem at all.
If our galaxy takes 250 million years to make one rotation and the universe is 13.5 billion years old does that mean the Milky Way has only made 54 revolutions? Surely not. Yep And as Jar pointed out, it's actually less! When you look at the Universe from the point of view of the galaxies, it is a very different place; it is almost on a human scale: it's age is several tens of "years" (rotations of the galaxies), and distances are typically very local - distance from one galaxy to the next is measured in a few diameters of a galaxy! For example, our sister galaxy, Andromeda, which is essentially the same size and type of galaxy as ours, is only a mere 20 diaimeters of the Milky Way away from us! And there are plenty of minor galaxies at smaller distances. If you could turn up the sensitivity of your eyes, you would see that Andromeda is as wide on the sky as four diameters of the moon!! How about this?
Edited by cavediver, : No reason given.
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
This is my first post. Welcome
Now with the stars being relatively close to each other at one point the light given from any certain star could have been seen from any planet or star. Well, there were no stars at the Big Bang, but even if there were, this is not correct. Two "stars" expanding away from each other would be out of causal contact with each other. You can say that they were travelling faster than the speed of light away from each other, which is sort of true, but please appreciate that it is a "sort of". However, two "stars" expanding in roughly the same direction would not be out of causal contact with each other in the moments after the Big Bang, although this would happen later through inflation - unless they were very very very very very very much expanding in the same direction, in which case they could be still be in causal contact after inflation. These "stars" would be part of what makes up our Observable Universe.
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
It makes my head hurt to think about this, but would there ever have been two stars 'expanding' in roughly the same direction? It's worth the headache because you are quite right! Every point would have been expanding away from every other point. What I am doing is talking about how this would look on a space-time diagram, where the individual light-cones of neighbouring points would be roughly pointing in the same direction, where-as separated points would have their light-cones pointing in very different directions. I'm obviously out of practice with this pedagogical stuff, as that is very sloppy of me!
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined:
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In the context of NoNukes' comments even this clarification puts a picture of a radial event into my head. I know... crap, isn't it?
Could you be a bit pedagogical and elaborate on the difference between light cones and space points? Ok, I'll try... take the classic balloon analogy. As the balloon inflates, space expands, all points move away from each other. Place arrows on a selection of points of interest, such that they are perpendicular to the surface of the balloon - so pointing in the outward radial direction. These are the individual time directions of the inidvidual points. So here is the "real" radial picture - but only apparent in space-time rather than space. So you can see that time-directions of adjacent points diverge slowly, so keeping in causal contact for some time, where-as time directions of separated points are highly divergent and may never have been in causal contact. This gives rise to the "horizon problem", which is solved by Inflation. To get the light-cones, just make little paper cones and place them so that the apex of the cone is on the point and the arrow forms the axis of the cone.
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cavediver Member (Idle past 3674 days) Posts: 4129 From: UK Joined: |
I don't know why this model hasn't occurred to me before. Don't forget that in using the balloon analogy, I am presupposing a closed Universe - something that doesn't look particularly likely now. But if you just consider part of the balloon's curved surface, and imagine it curving away into infinite distance in all directions, then you have a more likely scenario and it doesn't change anything that I've talked about.
As always, you rock. Well, strictly speaking, last night I was post-rock, as I was at an Engineers gig in Southampton. But Tuesday night was Paul Weller in Brighton, and I most certainly did rock
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