The speed limit of the universe is the speed of light, which is a constant of 299,792,458 m/s.
The reason why nothing in the universe can travel faster than light, a both seemingly surprising fact, this conclusion initially comes from an equation. The equation below is called "time dilation equation", it basically states that the faster you travel, the time you experience will inversely slow down. In the equation, the speed of light is represented by "c". "v", is the velocity, in other words how fast the object in motion travels, and "t" is the time experience by you, and "t'" is the time experienced by another person or object that is static.
From the equation, we can see that "v" cannot be larger than "c", for if "v" is larger than "c", then v^2/c^2 will be larger than 1, and the result of 1 - v^2/c^2 will be a negative number. Notice, 1 - v^2/c^2 is under a radical, and we cannot attain a real solution from the square root of a negative number. This is why we cannot travel faster than light.
I know merely stating a deduction from an equation is not a satisfying explanation. Now, I will explain it with "real physics" description. In our universe, everything move through what scientists call “the Higgs field”, and that include photons, the particles which light composed of. Interacting with the Higgs field acquire things mass, but light particles, the photon does not interact with the Higgs field, so the mass of light is 0, and photon is the only thing that does not interact with Higgs field. Since the mass of light is zero, light does not have a speed limit, that's why it acquired the fastest speed in the universe, which is also a constant as mentioned above.
To accelerate a object with mass, it needs energy, but the mass of the object will get larger and larger as the object's velocity approach the speed of light. Finally, Since it requires infinity amount of energy to accelerate an object with infinite mass, if we want an object to reach the speed of light, we need an infinite amount of energy, and that's impossible to achieve even if we aggregate all the energy in the universe. This is hard to imagine, but we can go back to the equation and look at its graph.
In fact, I've already stating the reason in most concise form and least words in the second paragraph in introduction.