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Author | Topic: Universe - Size . . . something doesn't compute ! | |||||||||||||||||||||||
John Inactive Member |
quote: Sure you have, the fourth dimension is called time. Think of it like this. Imagine that you live on a dot. You can't move at all. You live in zero dimensions. Now imagine a line. You can now move in two directions or one dimension. A cube allows six directions of movement, or three dimensions. But wait, in order for you to move at all, you must be able to move through time. Movement is impossible without time-- it is defined as a change of position through time. Einstein envisioned time as a dimension just like the other three. That is the nutshell version of space-time. Moving through time is just like moving left or right, but the motion is through the fourth dimension.
quote: It could possibly explain why gravitational attraction decreases with the square of the distance, but I guess that is another thread. The point is, extra dimensions aren't thrown into the mix for the hell of it.
quote: If the universe is everything that is, how does this question even make sense?
quote: As far as I know, we don't know that it has an edge.
quote: Like a really big grenade throwing shrapnel in all directions? That won't work. Think about how a shrapnel pattern would look-- a loose shell of material flying away from the point of detonation, an egg with a hollow core. That isn't what we observe. Imagine yourself as one of those shrapnel fragments. Objects directly in front of you would be moving the same speed as would objects next to you, almost. However, if you were to look at an object directly behind you and on the other side of the point of detonation, it would be moving away from you at twice the speed you are moving. We observe nothing remotely like that. Nearly everything is moving away from us at speeds which fairly smoothly increase with distance from us.
quote: You are, of course, assuming the universe is infinite. ------------------
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John Inactive Member |
Any hypothetical or mathematical equation which uses long-held human "understanding", again peppered with imagined boundaries, with the purpose again of measuring or labelling the universe as being a set size is simply our inability to grasp the fact that earth is literally nothing in the whole scheme of things.
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John Inactive Member |
quote: Bingo.
quote: Nope. Think about the dot as all-encompassing infinite mass/energy. You seem to understand this as an alternative to having a 'dot' which resides in something. Now, imagine the dot stretched larger, something like a rubber band can be stretched larger. Or imagine yourself small enough to fit inside the dot and look around.
quote: A sphere is finite in surface area, but where is the boundary? See, you are assuming a great deal about the way things are. As far as what is on the outside, if there is an outside, we have no access to it. We are, for the time at least, stuck inside the dot.
quote: We know the universe has an end in one direction, the past. We have pretty good evidence of that. One reason people speculate that the universe is finite is that an infinite universe has serious problems. Imagine an infinite universe. Whatever direction you happen to look, you will be looking directly at a star. I don't mean, more or less at a star. That is the situation we have now. I means that the night sky would be brilliant white. There would be no dark spots. ------------------
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John Inactive Member |
quote: Infinite mass/energy, but zero volume.
quote: Only if the universe has a limited past-- in other words, a beginning. If the universe has an infinite past then light would have had an infinite amount of time to get here from anywhere, so you have a white sky. ------------------
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John Inactive Member |
quote: What you believe contradicts the evidence. As the man said, you can't always get what you want. The universe is expanding. Think back to the grenade analogy ( Frell! You replied to that post. Did I respond? ). Everything moves away from us at apparent speeds which increase with distance. This is consistent with a universe that is expanding. For this to work in an infinite universe that is not expanding, you have to assume that EVERYTHING is accelerating away from the Earth. In other words, the Earth would be at the center and some unknown force is pushing the galaxies away from us at ever increasing speed. In an expanding universe, anyone on any planet would see the same effect. No point is special and no unknown force capable of accelerating galaxies is required. Which is easier to swallow? Take a balloon and blow it up just enough to make it firm. Then mark dots on the surface with a marker of some kind. Now inflate the balloon and watch the dots. They all move away from one another at the same speed and, the further away a dot is from another the faster the apparent motion becomes-- measured along the balloon's surface. This also answers your next question...
quote: Think of the rubber material of the balloon as space. As the balloon gets larger the rubber stretches but the amount of material remains the same. Its just that the material has been stretched. Perhaps if you imagine a rubber ruler it will help. Lay a rubber ruler between two points, then stretch it. If you measure the distance by the marks on the ruler, the distance stays the same. If you measure by some other standard, say, the time it takes to travel from one point to another, then the distance has increased.
quote: There isn't more space. The space that was there has been stretched.
quote: What you call simple and obvious DOES NOT fit the evidence. You are going to have to come to grips with that.
quote: This is nothing but your assumption. You don't have any evidence for it. ------------------
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John Inactive Member |
quote: OK. The grenade idea was yours, though I named it. You propose an explosion in space, much like a grenade. This does not produce anything like what we see. Go back and read that post. This is the reason why your idea that the BB was an ordinary explosion in space is wrong. The balloon analogy is a popular visual. It isn't a proof. The proof is... well, we'll try again...
quote: Ordinary explosions do not produce the patterns we observe. This cannot be the answer. It does not match observation.
quote: If we assume that the Earth is at the center of hundreds of millions of galaxies, then you are at step one of making the idea work. This is pretty hard to swallow. But it doesn't matter anyway, because that doesn't solve the problem. An explosion will produce a dense shockwave of matter moving outward from the point of detonation. We know what ordinary explosion look like. They look like this .mpg ( warning: large file ) . See that ring, or shell? We don't see that in the universe on a large scale. It can't be the result of that type of explosion in space. Now, if we assume that we are living in the very early days of the explosion and thus are living prior to the formation of the shell, we have another easily observable, but by no means the only, problem. If it were an ordinary explosion, everything would be moving away from us at just about the same speed. That is not what we observe. The further away a galaxy is from us, the faster it is moving. In other words, imagine that you measure all of the objects that are one foot away from you and find they are ALL moving away from you at 1 foot per minute. All of the objects two feet away are moving two feet per minute. All of the objects three feet away, and so on... See the pattern? You are adding to velocities, as if each object were pushing off of the nearer objects. You can solve this by postulating some weird and undetected force that causes objects to accelerate at faster and faster rates as distances FROM WHERE YOU STAND increase, or you can accept that space itself is expanding. This is exactly what we'd expect to see if space were expanding. This is what the visual of the balloon was intended to help you see.
quote: Bloody hell! Its a freaking analogy. It is intended to give you an idea. It isn't proof. The proof is mathematical and observational.
quote: What is the force causing them to accelerate? You can't answer, "The explosion." Why? Because the explosion is gone. We don't see it anymore. In a normal exploson, once the initial detonation ceases, things stop accelerating. Oh. And then there is redshift. Cosmological redshift is a directly measurable effect of light travelling through expanding space.
quote: Do you want the math? Start browsing Eric Weisstein's World of Physics.
quote: The analogies aren't proof. They are explaination. If you want proof, you are going to have to study the physics.
quote: I am really beginning to wonder.
quote: The stars? White sky? Remember? That is the best single bit evidence against an infinite, in space and time, universe. What more do you want? Do you see a blinding white sky at night?
quote: Then learn the math. If you don't want the analogies, which are an attempt to make four and more dimensions palpable, then you have no choice. ------------------
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John Inactive Member |
quote: I tend to think Uncle Freddie was much too bright to have meant that literally. As a date said to me once, "Nietzsche wrote philosphy as if it were poetry." I think the doctrine of eternal recurrence ties into his dictum that you should live your life such that you'd wish to repeat it for an eternity. But, that is off topic. ------------------
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John Inactive Member |
Neither solution would sit well with MarkSteven, that is why I didn't offer them as solutions to the problem. The finite and/or expanding universe is precisely what he is arguing against, so I offered a classic problem with the idea of an infinite universe.
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