This was something I mulled over earlier today during what should have been my commute. I say should have been because cars didn’t appear to be moving. Apparently the introduction of a single construction vehicle, block no lanes, was enough to bring I-5 to a pace slower than walking on foot.
There is nothing within Einstein’s equations (or any equations related to physics) that suggest that we cannot travel through time (in either direction). Interestingly the equations don’t even say that nothing could travel faster than the speed of light, the equation itself breaks down the second something is going as fast as light, but if you begin with something already moving faster you can keep making the thing faster and faster as much as you like.
It’s a bit like a bell curve, just the valley of the curve happens to be dividing by 0 which is a big bundle of woops. So you might think, sweet, I’m going to go travel through time once I figure out how to hop over that hurdle of moving faster than light. We naturally will assume for the sake of argument that the fundamental building blocks of your body are not broken down into photons during this transition.
Here you are, soaring through space and time, where would you like to go? Perhaps you would say the beginning of our known universe. There are some problems with this plan. The first is that when you get there, assuming you could stop without exploding yourself (or just dying in general), the universe will be one of two things.
It will either be so insufferably hot that it atomizes you instantly or it will be pitch black. This is the problem with visiting the Birth of the Universe. You could never watch it, the act of seeing it would always place you inside of it and doing so would always kill you. You wouldn’t see it, you wouldn’t hear it, you wouldn’t feel it. You would be for a moment in a strange situation because we need light to see, but there would not yet be any light, and in order for their to be light you would need to be within the universe which…as you likely know, would be hotter than the hottest thing that we’ve ever measured.
There would be no universe and then you’d be dead. The death would be so quick and so complete that you wouldn’t even see it coming. You wouldn’t feel it coming. You wouldn’t even know the end had ever happened. Your thoughts would end in an instant so finite that we can only measure it on paper.
So if you are planning to travel into the past, I don’t suggest you go back to the beginning of the universe. That is, unless you are looking for the most over the top suicide to ever be done. In that case your end would be difficult to top.