Can we step twice in the same river? And can we see the same object twice if we look somewhere else in a moment?

The object is much more than some outfit. The internal structure and energy level of the object means much more than just thing that the shape of the object. We can think that computer looks impressive, but without programs and an operating system, it's nothing. 

Can we step twice in the same river? Ludwig Wittgenstein and many other philosophers thought that question. The answer to that question is not as easy as people think. We might think that the river is the frame, and the water that flows in it is the thing where water molecules flow to its end. 

When we think that river is the frame or entirety, or some kind of line we can touch the same river twice. But in other ways, we can think. That the river is the water molecules that travel our past. That means we might touch the river at the same point twice, but the water molecules at that point are changed. 

That means the river might look the same as it was a second ago, but the things that are forming the river are changed. Or at least their position is changed. So we can transform that idea into a macro environment. We can think that the universe is the largest known environment and structure. The universe expands all the time. And that expansion changes the energy level of the universe. 

If we think that energy level is one shape of a particle we can ask: can we see anything twice? The energy level in the universe changes all the time. And that means the shape of particles is changed. 

The change in energy level means that the particle turns different than it was a short time ago. That means twice we cannot look at the same universe. When we see the universe and look away, and then look at it back, its energy level changes. The situation is similar like we would load electricity onto metal bites. Those metal bites might seem similar to others. But they can give electric shocks. 

When we think about the future of the universe. We don't know exactly what it looks like. We know that at some point, the energy level in the universe turns lower. That means the universe might look like the same as it's today. But it's not the same. The universe is not infinite. There is a point when the universe's existence in the form, as we know it ends. Same way if we see something all of our life we can think that thing remains forever. In the universe, nothing remains forever. Not even the universe itself remains forever. 

We can think that some mountain is forever. But the fact is that things like the explosion of Mt. Saint Helens show that nothing remains forever. As time goes even the tallest mountains are falling. And the brightest stars are turning into black holes. We can say that star just vanishes from the sky, but the star remains as a "hole" in the universe. The star exists but it's not the same star. 

Star can be lost billions of tonnes of material every second when that material turns to wave movement. So when we are looking at the star again after a second that star turns to lighter. And that means the star is not the same anymore. It's the lighter version of the star.