The universe as we know it is going to end, and there is literally nothing we can do about it. Unlike religious cults, however, I have science to back me up.
Have you ever heard of that trick where you take a bottle of water, put it in the freezer, and then agitate it and it spontaneously freezes? It's caused by the water attempting to go into a solid state, but lacking a 'seed' to start freezing with. Putting a bubble, imperfection, or something else in the bottle would cause that, and it turns into ice. At least that's just for water, right?
Wrong. You've probably heard of the term dark energy. Chances are you know what it does, but for anyone who doesn't, here's basically what it is. Apparently the vacuum of space has an ambient anti-gravitational effect. No, not free-floating zero G, but rather negative gravity. If you were to be in these spots, you would be slowly pushed apart. However, space is full of this vacuum, and the universe as a result is full of dark energy. Everything is slowly moving apart, eventually leading to a slow and drawn-out death quadrillions of years in the future. However by then we would have become technologically advanced enough to prevent or evade that somehow. (look how far we've come in the last 5,000 years! from learning how to farm to making missions to Pluto.) Besides it's so far away, it's not going to happen for all anyone cares. Well it isn't, because something else is going to happen first.
Recent calculations done by physicists show that this dark energy is in a state of energetic suspension, akin to water below 32 degrees- but just barely. An imperfection in space-time could cause the universe to send a shock wave of pure, utter destruction at the speed of light. It might have already, and we wouldn't know it, and still won't know it until it hits us because nothing can travel faster than light to warn us. The universe would be gone in a flash of light, and we wouldn't know what hit us. Plus, there's absolutely nothing scientifically to suggest an afterlife despite what we'd love to tell ourselves, since it's in our best interest. We would simply die, and that would be the last relic of human civilization, existence, and everything we know- all gone.
They know this happens, because it's already happened. The big bang was one of these, fitting the described phenomenon exactly. And of course we know nothing about what there was before it, because all of that was gone- overwritten. Countless civilizations could have lived and all been wiped out before they even knew.
All of this seems scary enough, but then they further calculated how common these are:
Every 10-20 billion years.
And then you realize that the last time this happened was 13.8 billion years ago.