No it's not.
Your imagination is wholly dependent on your experiences. Things you have never experienced, directly or indirectly, cannot be imagined. You may be able to imagine a griffin, for example, which doesn't exist, but an eagle and a lion DO exist. You may be able to imagine a tune that has never been played, but the tones that make up that tune already have been.
Try imagining a quantum state, say a particle that is also a wave at the SAME TIME. Or spinning clockwise and counterclockwise at the same time.
Or, as mentioned earlier, a 4-d sphere.
We can talk about these things, and their existence, but it is impossible to pin them down to anything "real" in our world of experience.
We cannot even imagine "3". We must imagine 3 somethings. But we cannot just imagine "3".
You can't imagine 65 million years. You can get that it's a long time, but that's about it.
Indeed, I am sure that scientific concepts like quantum physics, and evolution are real, because we simply couldn't make that shit up!