"The only thing we are absolutely certain about is that nothing is certain." 

-Werner Heisenberg-

Quantum Physics is one of the most difficult things to wrap your head around, in fact, if you’re starting to feel like you understand quantum physics, you probably have no idea at all. The field of quantum physics is on the bleeding edge of human research and knowledge, and there’s more mystery here than in any other scientific field. Some concepts of quantum physics have even reached mainstream vocabulary (though often misused or oversimplified to the extent of being wrong), one of these concepts is the Heisenberg Uncertainty Principle. 

Simply put, the Heisenberg Uncertainty Principle posits that we can never measure an object's position and speed/direction at the same time. Now the nitty gritty logic calculations behind this principle are far too complicated for someone like me, so I will only try to attempt to explain the basic logic of it. 

The cornerstone of quantum physics is that every single thing in the universe behaves like a particle and a wave simultaneously. This seems counterintuitive and impossible from our regular human perspective, but that is exactly what’s happening on a subatomic level. Now particles exist at a definite single point in space and time, but waves are spread out and have inherent momentum to them. These two seemingly contradictory states are a part of every atom that exists. 

Now the Heisenberg Uncertainty Principle suggests that if we want to measure an object's position more accurately, then we will lose certainty about that object’s speed and direction, and vice versa. A good analogy that really helped me to understand this concept is photographing a moving object. Imagine that we’re trying to take a picture of a baseball flying through the air; If we use a high shutter speed to take the picture, the ball would seem perfectly clear and detailed, we can determine its position quite accurately within the time we took the picture, but we don’t know what direction it’s going or how fast. Now let’s try using a slow shutter speed, the thrown baseball would look like a streak of white across the picture, so we can get an idea of the speed and determine where it’s going, but we lose sight of the definite position of the ball, since it looks all over the place within the streak. 

In the end, it’s just an approximation. Because it's important to remember that subatomic particles exist in a state of probability, not certainty. That’s what makes quantum mechanics so difficult to understand, we can never be certain of anything, because the basis of reality at that miniscule level of existence is just so different to what we are used to experiencing. This is just one concept in the wacky world of quantum physics, there are many more mind-bending theories that exists, or maybe, do not exist? 

A cop pulls over a physicist and asks, "Do you know how fast you were going?" 

The physicist replies, "No, but I can tell you exactly where we are." 

The cop says, "You were going 75 miles per hour." 

The physicist throws his hands in the air, and cries, "Oh great, now we're lost!"