Exactly. Multiply by -1 and you rewind your life. These are mathematical games that don’t reflect the actual machinery of the universe. Use of math to model the observed workings of the universe is fine, but don’t assume that the universe observes all mathematical constructs. String theory is perhaps the poster child for mathematics run amok.
Ultimately, it may be that the universe is infinitely divisible in space, but that the basic building blocks of matter and energy are not infinitely small and, therefore, you cannot arbitrarily address into that infinitely-divisible space.
As for time, I believe that there’s no such thing. Matter and energy go through state transitions and we perceive the changes in the overall state of the universe as time (which we measure using state transitions). There’s no going back through time because the universe only maintains one state.
To you, that’s just semantics. To those of us not steeped in the mathematics of space-time, it’s an important observation. To say that I don’t believe in time is a statement that I don’t believe in the popular presentation of time as a ‘thing’. That is, a manipulable dimension that we can move through the way we move around a room. Once time becomes a mathematical construct that describes the relative rates at which states transition, yes, it would be viewed as semantics.
Ahh, see, that may actually hinge on how correct, or not, general relativity really is. If space-time is really a good model for the nature of the the universe’s sub-structure, then time-as-a-dimension is actually a good approximation to the real world. The inversion of one of the spatial dimensions and the time dimension is actually the reason why, in GR, black hole event horizons are one-way doors.
@Kichae, I have a question for you. I ask publicly in the belief that others might find the answer interesting.
My understanding of the formation of the solar system is that it all began with dust and gas, with the dust first being drawn together by electrostatic forces to the size of puffy gravel, then gravity took hold and got everything going in earnest. Bodies formed, bumped, compressed, enlarged, crashed, and so on.
Why would the starting point be dust? Planetary nebulae and novas would kick out lots of gas and some dust, but surely a supernova would kick out all sorts of big chunks of stuff, ranging from gravel to planetesimals. Perhaps much larger. It seems like it would be ideal seed stock for gravity-driven formation of larger bodies. Stars, rogue planets, etc.
I figured that a natural starting point for identifying such debris would be metallic asteroids, but Wikipedia tells me that they are the remnants of larger bodies that formed, differentiated and were then blasted apart during the formation of the solar system.
Is there no theory or evidence of supernova debris playing a role in the formation of a planetary system?
That’s the core accretion model, which is both the classical and the dominant model in planetary formation theory, but there’s a competing model called the gravitational instability model which says that over-dense regions in the formation cloud quickly undergo wholesale collapse. As more and more observational evidence of planetary formation starts to trickle in, core accretion seems to be increasingly bolstered, but the gravitational instability continues to maintain its support.
The supernova itself merely expels hot gas. The more massive elements condense into grains of dust as they cool. More massive bodies in orbit around the former star seem to remain in orbit around the supernova remnant, and any largish chunks that don’t hang around don’t get pushed away with enough force to actually have them seed interstellar gas clouds in appreciable numbers. And if supernovae can’t do that, then the expulsion of gas that comes with the formation of a planetary nebula doesn’t stand a chance.
In short, the gravel and larger chunks stay with the dead star. It’s only the dust grains and gas that are light enough to escape the stellar remnant.
Direct evidence is pretty hard to come by, given the time and distance scales involved. From a theoretical standpoint, it’s usually the shock wave from a supernova that is considered a possible, even probable, cause for initial cloud collapse.
Ah, that was the missing link. I was assuming that the ejection velocities would be higher and that the temperatures prior to ejection would be lower. It sounds like all the stuff in the star prior to supernovae remains gaseous.
And as I think about it, I realize how naive it is to think that there would be anything solid. If the pressures and temperatures are sufficient to fuse silicon into iron, certainly they are sufficient to ensure that everything remains in a plasma state. Although now I’m wondering about the behavior of that atomic brew of plasma after the supernovae.
Just for giggles, here’s an image showing iron in the supernovae remnant of B Cassiopeiae.
Exactly! The only thing solid in a supernova are any planets or minor planets that were there before the blast, and were large enough and far away enough to survive. And you probably want to use a fairly loose definition of “survive” here. We’ve found planets in orbit around supernovae remnants, and they’re thought to have been formed from the remnants of significantly larger planets that existed in the system before the star blew up.
I understand what you say, but I think this debate could have … an infinity of steps
More seriously, my problem is exactly on what you pointed out : [quote=“Kichae, post:40, topic:3186”]
That’s the key as to why this works, though. Because it takes proportionately less time to cover a proportionately smaller distance, you’re able to cover those infinite steps in a finite amount of time.
[/quote]
You’re so right, but in the same time look at the paradox ! How could you cover those infinite steps ? Infinity is unreachable by definition, so you cannot see the end of it…
I personally don’t understand how this can make sense, except if I assume that the space-time is discrete… and the concept I have of my universe is exactly the opposite… but now I don’t know… xD
A finite distance can be divided on an infinity of sub-distances, this paradox is incredible. Can the space-time be discrete ? Please HELP ME !!!
It isn’t really a paradox. It is just putting numbers into a finite space. Numbers are a human construct, not perfection.
It’s like taking a one foot ruler and breaking it down for ever… ie 12 inches. it is still a foot no mater how many made up things like numbers is crammed into it.
And on a side note, the real reason I posted not the above:
There are an infinite number of numbers between 1 and 2. That doesn’t mean we can’t count to 2!
There may be a infinite number of steps involved in Zeno’s paradox, but most of them take an infinitesimal amount of time. When you out them together, you get a finite distance and a finite amount of time, which means you can actually reach your destination.
I’m gonna introduce Planck’s Length into the argument, it’s existence hints that space can not be divided into infinite number of smaller pieces for all practical purposes.
You cannot count from 1 to 2 in R (not more between 1.0000000000000001 and 1.0000000000000002 they have the same “Cardinal” (same term than in french ?)).
For Planck’s length, I know it by name but I don’t know what these limits mean. Is it for a practical reason for some formulas or calculation ?
The Planck length is the distance scale over which it becomes impossible to determine the position of quantum mechanical objects. It doesn’t really imply that space is quantized, but it helps string theory out a lot if it is quantized at Planck scales, IIRC.
And yet you can count from 1 to 2. And you can sum from 1 to 200. And you can sum infinite series!
It doesn’t matter how many steps it takes to do it. If the majority of those steps take 0 seconds to perform, you can perform them all.
Quantum teleportation is supposed to involve quantum entanglement of the state of a pair of particles, followed by measurement of the state of one, leading to knowing the value of the state of the other. This works even when the two particles are separated by significant distances.
For some reason, physicists have concluded that the particles are influencing each other at the time of measurement. I’m having difficulty wrapping my head around why that would be true. They already influenced each other at the beginning of the experiment.
As an analogous example, consider that I take a meter ruler and snap it into two pieces at some random point along its length. I put the two pieces into two sealed boxes. I separate the boxes by some distance. Observer one opens box one and finds that there is a section of meter rule that is 23cm long. Amazingly, that observer now knows that the length of the meter rule section in the other box is 77cm long.
Why are the two particles with entangled state not the same as a meter rule broken into two?
I can count from 1 to 2 in N I’m okay but on a Set (N) where “atoms” are integers. In N if I increment 1 I obtain 2. In R, if I increment 1, what is the number I should find ? So how could you count to 2 in R ? “Alef 1” is infinity by definition in R.
in R like in N (with classic axioms ant method of summing) “1 + 2 + 3 + 4 + 5 + 6 + …” goes to infinity. I know its sum, but it doesn’t mean I can count from 1 to infinity.
When I say “you cannot see the end of it” I speak about counting, start counting now and you’ll never going to see the end… We know that the result of “1/2 + 1/4 + 1/8 + 1/16 + …” goes to 1, but on a “physics approach”, The fact that I can reach the next meter, if implying that I saw the end of an infinity of steps, makes me think that I missed something, because it cannot be : I cannot reach end if there"s an infinity of steps between where I start and the end…
You’re trying to help me admitting that because I can reach the next meter, I am able to pass through an infinity of steps to do it… I cannot admit that because of the definition of an infinity of steps… Mathematically it’s okay, but in reality how could it be done ? …
Science speculation :
In String theory, maybe the limit scale is the strings scale or the planck length magnitude and under this scale we are in another universe so we can assume that the number of parts between 0 and 1m is limited because of this ?
I think I’m going to look after the loop quantum gravity closer too, maybe it’s more relevant that I though…
I Imagine my english doesn’t help to understand my point… sorry !
No, I’m trying to make you see that the amount of time it takes you to perform each step matters. You can easily perform an infinite amount of steps if each step takes identically zero seconds to complete.
I’m also trying to suggest that you’re thinking of this backwards. It’s quite obvious that you can move, so your interpretation of Zeno’s paradox must be the thing that’s wrong here. Look at your own assumptions, and figure out which ones might not actually be necessary. I suspect you’re overtinking this a little bit.
Any move, even for 10^-48m takes time, so there’s no step taking zero seconds. I don’t ignore the notion of time in my thoughts, but it resolve anything…
My problem is that there is a possibility where to resolve this paradox you admit that there isn’t an infinity of steps, and this seems (for me, at least) to be the more convincing for the moment (but it is embarrassing because I always defended the infinity of the universe around me…)
But it takes proportionally less time than a larger displacement! So, the total sum of all of the times it takes to perform each step is finite.
The other way of looking at it is that the infinityith step is a movement of exactly 0 metres, which takes exactly 0 seconds to accomplish. Everything scales properly.
Maybe think about the paradox in its original context: Achilles and the tortoise. Achilles is racing a tortoise, but bthe tortoise has a head start. Every time Achilles catches up to where the tortoise once was, the tortoise has moved on. Under what circumstances will Achilles catch up to the tortoise? Under which circumstances won’t he?
Quantized space, or a finite number of steps, aren’t required to put this to rest. Just the acceptance that, eventually, one of those steps will involve moving 0m in 0s.
Honestly, quantum teleportation is a bit above my pay grade. I have a basic understanding of entanglement, but teleportation just seems like black magic to me, and quantum mechanics is pretty far outside of my field.
