grimlove527 said:
right. I forgot that you would have a different memories than you did before you went back in time. I have another question: Do you know anything about wormholes? I already know that they are shortcuts to get to a distance far away. I also know that thet apply to the theory of realitivity. I just can't find out how we came upon them. I heard there is no evidence that they exist.
I can't be very exact with this description but I think you will be happy with it.
I'll describe the effect then describe the cause. A good way to imagine what a worm hole does is to imagine a hallway in your front yard. You can look through this hallway and see out the other side. There is something funny about it though because the hallway is 50 feet long on the outside but inside it is only 5 feet long. Now a wormhole is a bit more complicated (and dangerous) but the effect is about the same. Except it happens in space with no hallway around it. So how can this be with known laws of physics?
Remember above where I said gravity slows time down? Well to the person in the gravity field time is not slow, it's looks to them like time outside the gravity is fast. The person in the gravity field, because they measure time as normal will measure the distances between things as shorter. This means that if your friend is upstairs in a two story house you are closer to your friend than your friend is to you by a very very tiny amount.
Now for a wormhole to make two places a lot closer, if you go through the right invisible hallway, it needs to be a very very powerful gravity field. So powerful that if you got too close the gravity would rip you apart. So how do we get through without being ripped apart?
We'll the first step is to spread the gravity field out over a big area of space. This works because space and time dilation does not depend on how strong the gravity is around you. It depends on how deep in the gravity field you are. For instance, if you were to go to the center of the Earth you would feel weightless as if there is no gravity. However, time will be slowed just as much, and space shortened just as much. So we can have these effects without being ripped apart by gravity. The gravity must still be around you just like in the center of the Earth.
Now to make this hole more like a worm we need to change the shape. The round shape of the Earth doesn't work because you must climb back out the same amount of gravity as you went through going in. So we stretch this gravity out into a long tube such that you are at the center all the way down the center of the tube. Then you can travel a great distance before climbing back out of the gravity on the other end. This distance through this hole will be much shorter than the distance outside the hole just the the hallway in the front yard.
No in the description I give it is normal gravity with normal mass. This means that you may think you went through a short hole in a few minutes but to the people outside you spent many years going through a very long hole. To change this theorist use what they call exotic matter. This is basically matter that has has negative energy density, where normal matter has a positive energy density. This allows for people to get through these wormholes in a few minutes or hours to the people both inside and outside the wormhole. This exotic matter is also thought to help prevent the wormhole from collapsing on itself.
There are theoretical problems.
General Relativity (gravity) does allow these things to exist if you can arrange enough matter in the right way. It does not say whether you can actually arrange matter like this in a stable manner, only that if you did it would work.
This exotic matter is another problem. Exotic matter is thought to have negative mass so the gravity repels instead of attracts. This is how it helps stabilize the wormhole by balancing attraction and repulsion. This is a purely theoretical substance which has never been observed. Though it is unknown whether exotic matter is absolutely required for wormholes.
It is unknown if these solutions will remain valid in a theory that include both General Relativity and Quantum Mechanics.
You are correct that there is no evidence that they exist in a meaningful way. The best we can say is that they are allowed if matter can be configured certain ways. However, in a very limited sense you travel through a hole in space every day. To a person in orbit around the Earth the distance is longer from your house to your school than it is to you on the ground, by a tiny amount. You are going through a tiny wormhole of sorts every time you go to school.
