Is there such a thing as truly random? [closed]

Question

I saw a video about random numbers and how the programmer in that video was talking about computers generating pseudo random numbers and that they are not really random. I knew about this.

Then he showed the decay of a radioactive material to generate random numbers where he claimed to be truly random. Is there really such a thing? I mean the process of the radioactive material shooting electrons might seem random but is it? Isn't it just a mysterious black box to us simply because we don't know how it really works?

Or does randomness just depend on the current level of scientific knowledge?

If so, then how come quantum computers are often quoted to be capable of generating truly random numbers? Can they really do this?

Answer 1

All our current theories of Quantum Mechanics suggest that those quantum properties that are random - are truly random.

Some practical applications are the time between decays of atoms in a sample of a radioisotope or thermal noise in a resistor. These are fundementally random.

However you have to be a little careful with actual implimentations of these hardware effects, it's very easy to have a quantization of some timing circuit, or bias in an ADC which reduces the actual randomness.

There are a number of questions on physics.so eg. https://physics.stackexchange.com/questions/317/why-cant-the-outcome-of-a-qm-measurement-be-calculated-a-priori

Answer 2

The short answer is no. By a definition of the word random in this context, it means that, in terms of cause and effect, an effect must occur without any cause. In a deterministic universe, this is impossible.

At least, until you get into quantum theory.

I am not capable of explaining quantum theory to you, but know that it is a lens by which we do not ordinarily look at our world through. Anything we typically use the word "random" to talk about in normal speech is not truly random - it is simply unpredictable beyond our limited perceptions. However, were our knowledge or perception greater, we could find the cause of the effect, as there is one.

This may be a good starting point for further research.

Answer 3

There are random events.

Events such as the decay of radioactive material (hotbits) cannot be predicted. It is random. In the hotbits situation, the random bits are generated by comparing decay events. If the time of the first two events is less than the time of the next two events it is a 0 - if the second pair is shorter than the first pair, it is a 1, and if they are the same, it is thrown out.

These bits are 'expensive' in that there is not a lot of bits out there. Most people use this as a seed to a pseudo random number generator. If the seed is random it becomes very difficult to identify the sequence (most people seed random from the time or the process id or the combination...)

---

There are random sequences (known sequences, but the order of the values is random).

This was largely examined in Can you use Pi as a crude random number generator. The question if the number is normal plays a role (though not all normal numbers have apparently random next digits).

---

There are chaotic events, that while not random are extremely difficult to predict.

Lavarand uses a set of lava lamps to seed a random number generator, much the same as the radioactive decay does. Look at patent 5,732,138 for more on this.

Answer 4

On the macroscopic (i.e. non-quantum) level, things that we think of as "random" are in fact "chaotic." This means that minute perturbations can have non-minute effects on the outcome. For example, you could in theory accurately predict the outcome of a fair coin toss or a fair die toss, but this would take a ridiculous amount of calculation and a slight shift in the air currents would throw all of your calculations off. But the fact remains that in theory you could predict these outcomes, and so the processes aren't truly random.

As Southpaw Hare brought up, quantum effects are truly random, at least by our current reckoning in physics. An electron does not exist in any one place at any one time, instead the electron exists in a probabilistic cloud - at the quantum level, particles exist as both particles and waves. The Heisenberg Uncertainty Principle says that attempts to narrow down the location of an electron are doomed to failure; when you measure the electron's location then you affect its velocity (so the more accurately you know the electron's current position, the less accurately you know its subsequent position). I believe that random number generators based on radioactive decay are tapping into quantum uncertainty and are therefore truly random, but it's been a decade since I took a physics course and so radioactive decay may instead be a chaotic process.