Wiploc

I assume matter is grainy. That doesn't mean space is grainy. I even understand that there is a minimum length-of-motion, so that if a particle is at A and wants to move toward B, it has to go all the way toward B; it can't just go halfway. But I don't know of any reason to think that means the place halfway between A and B doesn't exist, or that it couldn't be occupied by something coming from someplace other than A.



Isn't this a bit like saying there are too many grains of sand on the beach to count --- so we're going to say there are ten? Or like saying, we looked diligently for Bin Laden without finding him, therefore he doesn't exist?


I'm talking about actual places. Do we have any reason to believe space itself is grainy as opposed to being a continuum? If it's a continuum, then there are an infinite number of actual places on a line.
crc

Wiploc

Why wouldn't numbers map onto the points of a physical line?
crc

eh

It seems there are 3 main candidates for the existence of a real infinity in nature. They are the infinity of space, the infinity of time, and the question of whether or not space is continuous. Modern cosmology puts doubt on infinite time, and area and volume may be discrete with a quantum theory of gravity. Then I suppose you could still have an infinite number of points on length (loops, strings, etc.) but who knows if that is actually an accurate description of space?

Even if the other 2 infinites are abolished, there still remains the infinity of space. There doesn't seem to be a way to prove either finite or infinite space, and either is consistant with observations from cosmology. But an infinite universe would introduce new infinities, with an infinite amount of mass, galaxies etc.

NearNihil Experience

not one "Actual" infinity I can think of.

Pi is an abstraction, just like all numbers, even "infinity+1".

Xeno's paradox (all the little half-way points between halfway point) aren't actual. they are abstractions of our perceptions a product of our mind trying to impose perceptions on reality. Halfway points exist only whjere they are at. any comparision relatively is an imposition of a relationship that "actually" doesn't exist, especially concerning a singular object and its so-called constituent half-ways.

Absolute zero can't be reached and the speed of light is finite, just really really fast.

Space is grainy, as far as we can tell. Plank structure, Zero-point energy, the electron "jitter" motion point pretty clearly to a grainy structure of space and matter.

my 2 cents.

thomaq

what about time? is it possible for time to stretch infinitely into the past? i dont think so because then you would have an "actual infinite" of something. for instance, if i was standing up, and an infinite amount of people had to sit down before i could, i would never sit down. sounds cheesy but i think it illustrates the point.

AdamWho

No physical infinities.
On a side note: isn't it interesting how difficult it is to transition between ideal mathematical models and physical reality
For instance, lots of infinities exist in the mathematics of physics, such as the infinite range of gravity or infinite width of wave function. But it reality do any of these things actually exist?

eh

Well it would seem the range of gravity is infinite, but is this would seem to be a potential instead of an actual. The idea is if you take 2 masses and seperate them, you potentially can seperate them with an infinite amount of space and will still have gravitational attraction between them.

Shadowy Man

If black holes are found to exist, would the matter density be infinite?

Or would that only be if you found one that wasn't spinning?

Keith Russell

We can only calcuate 'pi' to a finite number of decimal places.

Even if you were using huge, superfast computers to calcuate 'pi', no matter how fast the calculations were being done, at the moment you looked at the display, you would see--even if only for that instant--that the ongoing calculations had reached a whole, finite, number of decimal places.

Sure, in the next instant, that number would change, would increase--but the new number of decimal place calculations, too, would remain a finite, whole (albeit very large) number.

K

thomaq