1. ## Random

I've been having this discussion with some friends.

Computers can generate 'random' numbers, but as far as I know, that isn't exactly possible. Maybe the current time is used and ran through some algorithms, but once you know those calculations, you can 'predict' which 'random' number will be generated.

Also makes me wonder if 'random' actually exists in the universe.

If I call out a random number, is it rly random?

If you flip a coin, the way you throw it, the air pressure, the surface, the friction, etc. all have an influence on the outcome - so it isn't rly random, right?

2. Is the amount of effort you put into throwing a coin random or not? Do you specifically seek out to throw it with a certain amount of power as to produce a required result? If not, and you put no thought into the toss, then it is random because the amount of power you put into it is random (regardless of other fixed factors such as air resistance).

3. What you are saying is that with precise enough mathematics, you can predict the future. Scientists and mathematicians have been toying with the idea for a long time, but the level required goes beyond what humans are capable of creating any time soon.

4. Computers cannot generate truly random numbers.

Quantum mechanics has aspects of random (see nuclear decay) so it often deals in probabilities. However, this could just be unknown forces at work.

5. http://www.random.org/

It claims that it has truly random numbers at least.

6. Originally Posted by JW1984BE
I've been having this discussion with some friends.

Computers can generate 'random' numbers, but as far as I know, that isn't exactly possible. Maybe the current time is used and ran through some algorithms, but once you know those calculations, you can 'predict' which 'random' number will be generated.
While true, pseudorandom is way better than that.
http://en.wikipedia.org/wiki/Pseudorandomness

Note that you can buy a card that makes it REALLY random. How?L

Also makes me wonder if 'random' actually exists in the universe.
Maybe. Quantum results appear to be random. They fall along known probability, and they appear to be FUNDAMENTALLY unpredictable.
http://en.wikipedia.org/wiki/Quantum_indeterminacy

http://photonics.anu.edu.au/qoptics/Research/qrng.php

If I call out a random number, is it rly random?
Of course not. You're a determinate machine.

If you flip a coin, the way you throw it, the air pressure, the surface, the friction, etc. all have an influence on the outcome - so it isn't rly random, right?
Correct. Much like the human brain, given the starts, you can calculate the finish. But please check out the physically random generator above- even known the initial conditions, it produces unpredictable results.

7. Originally Posted by JW1984BE
Maybe the current time is used and ran through some algorithms, but once you know those calculations, you can 'predict' which 'random' number will be generated.
There are such things as cryptographically secure random number generators where that isn't currently possible. You can even be shown the algorithm by which they are produced and you will still be unable to predict the next output.

8. Originally Posted by savvasp
http://www.random.org/

It claims that it has truly random numbers at least.
It still uses an equation (a complex one) to generate those "random" numbers. It doesn't just conjure them up.

9. It is impossible for a computer to generate a fully randomized number, a computer needs a set value to work from. You can however have very good pseudo random numbers

10. Originally Posted by fiif
It is impossible for a computer to generate a fully randomized number, a computer needs a set value to work from. You can however have very good pseudo random numbers
Again, with specialized hardware you can generate true random numbers.
http://qrng.physik.hu-berlin.de/

For most applications that need good ones, ones that are statistically random are good enough:
http://en.wikipedia.org/wiki/Hardwar...mber_generator

Statistically Random doesn't meet OP's specifications. Quantum random does.

11. Computers can generate random numbers, but it requires an external random seed such as radio static. Without such an external source, computers can only generate pseudo random values.

12. Originally Posted by Verain
Note that you can buy a card that makes it REALLY random. How?L
Such a card is a hardware random number generator, which collects random numbers from some random physical or quantum phenomenon. Radioactive decay (time between decays is inherently random) and collecting atmospheric noise are common methods.

Also, one can obtain truly random numbers via monitoring various random system statistics, such as ping times and bus errors. This is how /dev/random works on Linux/Unix systems.

13. Originally Posted by Masark
Radioactive decay (time between decays is inherently random)...
In what material? In most cases, radioactive decay is so NOT random that it is used for the most accurate clocks.

14. A computer cannot create a true random number.

Atomic decay is random i think?

---------- Post added 2013-02-04 at 06:16 PM ----------

Originally Posted by Kujako
In what material? In most cases, radioactive decay is so NOT random that it is used for the most accurate clocks.
The decay of the individual atom is random. You only know the probability of it decaying.

15. Originally Posted by Kujako
In what material? In most cases, radioactive decay is so NOT random that it is used for the most accurate clocks.
No, atomic clocks don't use decay.

They operate on hyperfine level transitions, which give off a highly precise and consistent frequency of radiation, and from the period of that radiation, gives you the elapsed time.

For example, the level transition of a cesium-133 atom releases radiation of exactly 9.192631770 GHz.

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