F
Fi$hy
Guest
and to think, I started this topic via Harry Potter 
sorry to keep dragging this thread on but i just like this stuff!
one thing i dont think anyones mentioned is what actually is time? is it actually something that can be measured like lets say length? or is it only in our minds that time passes?
same thing applies to space, what is space? there are the absolutists that would say space is actually a physical entity (well kind of, think of it as a box with no sides if you like)rather than the relationists that claim space is merely the relation created when objects inside it are brought into consideration. so when you point to a position youre only describing where that place is relative to other objects around it, like lets say a chair and a table, not the actual space itself.
one thing i dont think anyones mentioned is what actually is time? is it actually something that can be measured like lets say length? or is it only in our minds that time passes?
same thing applies to space, what is space? there are the absolutists that would say space is actually a physical entity (well kind of, think of it as a box with no sides if you like)rather than the relationists that claim space is merely the relation created when objects inside it are brought into consideration. so when you point to a position youre only describing where that place is relative to other objects around it, like lets say a chair and a table, not the actual space itself.
gringotsgoblin
In Cryo Sleep
MoTo^ said:
But like most paradoxes it requires a false assumption. You dont *have* to travel half the distance. You *incidentally* travel half the distance. If you were going on a short 20 meters journey and you walked 10 meters. Stopped. Walked 5 meters. Stopped. Walked 2 and a half meters. Stopped. etc yeah you would never get there.
What you actually do is: Walk 10 meters (which is incidentally half way). Walk another 10 meters. Arrive.
It's like the paradox: If there is an Immovable object and an Irresistable force is applied to it, which will win? Will the object withhold the force. Or will the force push the object.
Of course if you define something as being an immovable object there cannot be (by definition) an irresistable force. And vice versa.
The time travel element of this thread seems to be well covered so I wont comment.
S
Pestcontrol
In Cryo Sleep
MoTo^ said:
I asked my physics teacher the same once, it's the latter. Not that he was very bright, but still.
Strictly speaking, the size of the universe is a sphere expanding with the speed of light from the point where the big bang originated, so it'd now have a radius of whatever the age of the universe is, in lightyears. Assuming the speed of light is constant.
Still with me? Leastways, no current theory predicts a boundry of any sort.As for timetravel, it's presumed to be impossible just because of such paradoxes (and there's a lot of them), at least travelling backwards is.
One could view the universe as a static, fourdimensional object, fourth dimension being time. Just like a movie, playing on your computer, time passes at a set rate, but everything is there already. I had the same idea once
Pestcontrol said:I asked my physics teacher the same once, it's the latter. Not that he was very bright, but still.
lol i dont think there is a right or wrong answer here, just different theories. what exactly is the proof of this then?
also as to the paradox i mentioned earlier about points A and B, and never being able to reach B, its not quite as confusing as you may think because the series 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + ...... is exactly equal to 1 and does not go on infinitely. so ye, its not really to do with false assumptions and things, just a play on words really.
gringotsgoblin
In Cryo Sleep
MoTo^ said:
The way I understand it is that the series 1/2 + 1/4 + 1/8 + 1/16... is *almost* equal to 1. And because the difference is so minute it is assumed to be 1.
I dont know about everyone else, but I'm fairly sure when I travel somewhere I dont *almost* get there. I normally arrive exactly there. Albeit late.
I still stand by what I said. The question makes an assumption that your journey involves travelling 1/2 + 1/4 + 1/8 + 1/16... etc. This assumption is false.
I understand where you're coming from but essentially I dont like the mathematical answer because it assumes an infinite number of 'moves'. While Wikipedia does go on about it at length this part sums up what I am (with difficulty) trying to say: "In short, trying to use calculus to resolve the paradox simply reaffirms the idea that space and time are infinitely divisible, and thus still suffers from the basic question as to how one can possibly reach the end of an endless series."
http://en.wikipedia.org/wiki/Zeno's_paradoxes
Piacular
In Cryo Sleep
Pestcontol said:Strictly speaking, the size of the universe is a sphere expanding with the speed of light from the point where the big bang originated, so it'd now have a radius of whatever the age of the universe is, in lightyears. Assuming the speed of light is constant.
Ever heard of the Omega constant?
You know the one they figured out and teach on Astrophysics degree courses?
If Omega is less than 1 the universe will eventually collapse in on itself.
If Omega is greater that 1 the universe will expand forever.
If Omega is equal to 1 the universe will expand to a point where it expands so slowly it effectively isn't expanding at all.
They actually figured it out, I have the equation round here somewhere...
But the answer was 1... +/- their error, hahahahahaha! So infacto we still don't know!
Anyhoo, at least there is a theory about it.
(Damn it, I told myself I wouldn't post in this thread
)
Tetsuo_Shima
In Cryo Sleep
I like to think the universe is infinite. And Ill tell you why.
Cos I like the idea that somewhere out there, every single fictional movie, game, book, imagination, whatever actually exists. Wow, there must be a world where xenomorphs exist, a world where you could maybe slow down time like the matrix, a world without death, a world that tastes of strawberries. Coolio.
Of course, that proably isnt true :/
Cos I like the idea that somewhere out there, every single fictional movie, game, book, imagination, whatever actually exists. Wow, there must be a world where xenomorphs exist, a world where you could maybe slow down time like the matrix, a world without death, a world that tastes of strawberries. Coolio.
Of course, that proably isnt true :/
gringotsgoblin said:
no, it is EXACTLY equal to 1 mathematically. this is similar to saying 0.9999 (recurring) is equal to 1, which of course it is.
the truth about that paradox is that we are wrongly assuming that space is infinitely divisible. it may well be, but again its one of those things that cant really be proven completely.
there are loads more paradoxes that dont have simple answers like this, if youre interested look up Thompson's Lamp as a good example.
Pestcontrol
In Cryo Sleep
I know of Omega's constant, only under a different name. Einstein's universal constant or something.
There's been some recent developments on this field, new measurements seem to indicate it may not be a constant, meaning the current model of dark energy needs reworking.
Again wikipedia has some nice articles on the expansion and eventual death scenarios of the universe ranging from the Big Crunch to the Big Rip
Also, the universe, as far as is currently known, is not infinite in either size or mass/energy.
Moto: As for space being infinitely devisible, scientists prever to call this quantitised, which means you can assign a real number to it (rather than a complex one). I'm not sure what current measurements indicate or theories predict, but if i had to guess, infinite devisions are probably possible. You could ask yourself the same with time, there are seconds, microseconds and picoseconds, but how far can you go? I'm not aware of any limits yet.
And last of all, if i remember correctly one devided by infinity equals zero, even if the answer by common sense is "infinitely small", i remember asking my maths teacher the same question. But i'm not certain of the answer anymore.
There's been some recent developments on this field, new measurements seem to indicate it may not be a constant, meaning the current model of dark energy needs reworking.
Again wikipedia has some nice articles on the expansion and eventual death scenarios of the universe ranging from the Big Crunch to the Big Rip
Also, the universe, as far as is currently known, is not infinite in either size or mass/energy.
Moto: As for space being infinitely devisible, scientists prever to call this quantitised, which means you can assign a real number to it (rather than a complex one). I'm not sure what current measurements indicate or theories predict, but if i had to guess, infinite devisions are probably possible.
You could ask yourself the same with time, there are seconds, microseconds and picoseconds, but how far can you go? I'm not aware of any limits yet.And last of all, if i remember correctly one devided by infinity equals zero, even if the answer by common sense is "infinitely small", i remember asking my maths teacher the same question. But i'm not certain of the answer anymore.
gringotsgoblin
In Cryo Sleep
MoTo^ said:
um...0.999999 recurring is not equal to 1. It's equal to 0.99999 recurring.
Pestcontrol
In Cryo Sleep
If something devided by zero is infinity, then anything devided by infinity must be zero, even though you'd think the answer is "infinitely small".
When you have infinitely recurring decimals of 9, the difference with 1 is infinitely small, too.
I remember now there was a little calculation that showed quite clearly 0.99999 infinitely recurring is equal to one.. let me try to think of it.
Ah yes, i remember:
1/9 = 0.1111111 etc
2/9 = 0.2222222 etc
3/9 = 0.3333333 etc
[...]
8/9 = 0.8888888 etc
9/9 = 1
When you have infinitely recurring decimals of 9, the difference with 1 is infinitely small, too.
I remember now there was a little calculation that showed quite clearly 0.99999 infinitely recurring is equal to one.. let me try to think of it.
Ah yes, i remember:
1/9 = 0.1111111 etc
2/9 = 0.2222222 etc
3/9 = 0.3333333 etc
[...]
8/9 = 0.8888888 etc
9/9 = 1
Wraith
Active Member
Pestcontrol said:If something devided by zero is infinity, then anything devided by infinity must be zero, even though you'd think the answer is "infinitely small".
When you have infinitely recurring decimals of 9, the difference with 1 is infinitely small, too.
I remember now there was a little calculation that showed quite clearly 0.99999 infinitely recurring is equal to one.. let me try to think of it.
Ah yes, i remember:
1/9 = 0.1111111 etc
2/9 = 0.2222222 etc
3/9 = 0.3333333 etc
[...]
8/9 = 0.8888888 etc
9/9 = 1
That doesn't prove that 0.9999(recurring) = 1. It just proves that 9/9 = 1.
If it could also be proved that 9/9 = 0.99999, then you could say that 0.99999 = 1.As I understand it, the logic that you're proving/quoting, actually states that since 0.9999(recurring) is so close to 1, for all practical purposes it can be considered equal to 1. However, it does not exactly equal 1.
(I think
)Wraith
theres another way of showing this too:
(any 0.3333 or 0.999 etc number is recurring)
0.33333 = 1/3
0.33333 x 3 = 0.999999
1/3 x 3 = 3/3 = 1
now in what way does that not prove that 0.9999 recurring is equal to 1? theres nothing about infinitely small numbers etc, in reality it IS equal to 1...
ask any mathematician, he'll tell you the same thing
(any 0.3333 or 0.999 etc number is recurring)
0.33333 = 1/3
0.33333 x 3 = 0.999999
1/3 x 3 = 3/3 = 1
now in what way does that not prove that 0.9999 recurring is equal to 1? theres nothing about infinitely small numbers etc, in reality it IS equal to 1...
ask any mathematician, he'll tell you the same thing