Basic question regarding point of view

[ketamynx]

Hello, people.

I have two questions but first please bear in mind that I have an absolute 0 of theoretical knowledge. I just read what's on the Internet and I'm curious. So here are the questions:

1. Temperature makes atoms vibrate. However I've found out that you can't figure a precise location for one atom. How about when there are -100000ºC? :D Can it's position still not be measured?

2. I watched this: (double slit experiment), saying electrons generate an interference pattern when not looked at, and the two lines when observed. I don't really know any optics nor physics that bad, nor haven't red anything about how the experiment was done, how many times and under what conditions or so, but I do wonder this:
a) Electrons emit a wave, the observer, if it's there, absorbs that wave. If not, only the screen will absorb it and the two lines from the slit should also be visible, overlapping the interference pattern. Did I got it right? Is this correct?
b) If you have a perfect setup and start shooting with matter, why doesn't the dot hit the same place twice? Will it be because of q. 1?

Thanks guys,
Wish you all the best.

 

[Feldoh]

1.) The way temperature is defined you can't go to -100000ºC just to around -273ºC, but you're just asking for something really cold right? If you cool an object down to a very low temperature that corresponds to very little "vibration". However quantum mechanics tells us that there is a fundamental limit to how well we can know the location of an object in relation to it's momentum. So you *can* (theoretically) measure the position of an object with 100% accuracy but you would know nothing about the momentum of the object.

a&b) It's a very hard question to answer without a lot of mathematics. In quantum mechanics we talk in terms of probabilities and interactions with the system (in this case an electron=the system). Interactions with systems change the state. If we interact with the electron before the double slit we change the state of the electron so that it has a much more defined position and a much less defined momentum.

If instead the electron interacts with the double slit it will once again change the state. Then once we finally measure the position of the electron AFTER it has interacted with the double slit we get an interference pattern but once again we know the position of the electron well without knowing it's momentum.

Essentially it all comes down to interacting with the system. If we interact with a system it will change.

 

[BruceW]

ketamynx - the electron in this situation isn't emitting waves, in fact it is a wave. It only becomes 'particle-like' when it hits the screen. The reason the dot doesn't appear in the same place is because the outcome is inherently random.