Okay, from a few other people that work in the field and have some answers given by books they have written.
One is Dr. Hawking, back in 1996, previously from 1988, and a book called a "Brief History of Time".
Time in the future is open. Time in the Past is closed and has to be self-consistent, which means that if you were able to travel back in time, which is doubtful according to Dr. Hawking, then you could not go back and kill your grandfather, since it is clear that you were born, otherwise you would not be here posting. So, if you were able to go back in Time, you would have less free will in what you would be able to do, because you would not want to change anything that would affect you, living in the future when you went back to the future. Now, the future is open, and you have more free will to decide what to do, because the future future is not here yet!
But, in the microscopic realm of particles, virtual particles fly apart into a anti-particle and a particle. The particle is traveling into the future, but the antiparticle may travel into the past. They separate, but then follow a closed-looped curve and come back smashing into each other and annilihate each other when they meet again. Space is made up of virtual particles all doing this all the Time.
SpaceTime can not be separated anymore since Einstein came out with his General Relativity Formula, that links Space (and the three co-ordinates that make up Space --- length, width, depth) with Time (co-ordinate is a measurement when you are taking the measurement). You must talk about SpaceTime, now, and Space is not separated from Time! It can not be, since you need all co-ordinates to tell yourself where you are at in SpaceTime. Enter Quantum Theory where information is thought to also flow, and energy is packets of discrete packets where information is also held. Call it like bits of a computer memory, memory like 1's and 0's and each packet is like a bit of computer memory.
1101 is diffrerent from 1001 is different from 1011 and so on.
Now enter another thought that since virtual particles from above follow this pattern, how is the info flowing from the particle to the anti-particle, since nothing is supposed to travel faster than the speed of light -- proved by Einstein with his Special Relativity formula that came first, 10 years before his General Relativity Formula -- E=MC^2 where E=is energy (amount of work done), and M is mass (the mass not the weight of an body in Space) and C is the speed of light and C^2 is the speed of light squared (or the speed of light times the speed of light) which is a very big number.
After that, enter some other thinking that there are more dimensions --- how many? -- now thought to be ten dimensions with six curled-up dimensions at the Planck's Length which is a very, very small number, something like 10 to the -35 centimeters (or meters, I would have to look it up!)
That means to the scientists, that there is a limit on how -- small -- small can get!
It is a limit like the speed of light is a limit on how fast an object can travel.
There are limits or barriers that can not be crossed, and it is not known whether those limits will ever be crossed and new thinking established.
This leads one to think that ever traveling to the stars will take a long time since one can only approach the speed of light and never really reach it (your mass would become infinite, and the energy to push you up to the speed of light -- infinite, and can not be done!).
So also to Eistein's formula, there is a way to bend Space, so a trip through the bent Space would take less Time -- it is called a Einstein-Rosen bridge -- a bridge connecting two regions of Space, by bending Space, so traveling across this bridge would take less Time, then going the long way through all of Space that is needed to get to that nearest Star -- Alpha-Centauri!
But also at the same time, Quantum Theory describes that particles acting in pairs as those virtual particles do, and acting the way that they do (also they can not get up to the speed of light either, since it takes more and more energy, but since they are way way smaller, they can use a particle accelerator like CERN or Fermilab, and get those particle smashing together at 99.99995% or so to the speed of light) leaves now the thinking to imagine that there may be multiple universes, where the particles are exchanging into and outof multiple universes, perhaps.
It is very much up in the air at this time, and a lot of math, and more experiments to prove anything also has to be done. But at this time there is limit on the technology, as we only know so much.
If there are multiple universes, they may not be similiar to ours, or some think that they could be. If that is true that multiple universes are similiar to ours, since every possibility may happen, or every probability, then there also may be universes that are ahead in some future time, and some also in the Past, and in the past time, from where we are at in time.
That is also very much up in the air, but combining a theory of everything means learning more about another force that is here -- and that is gravity, which is only now being having the technology to try and ascertain some of the answers about that.
The goal of physics is to come up with a unified theory of everything which Einstein tried to do, and could not. Maxwell before Einstein came up with combining Electricity and Magnetism, while Einstein combined Energy and Mass -- leading to SpaceTime.
Now Light and Gravity is also needing to be combined somehow, while Quantum Theory is there making up a mess of things, and is also being worked on!
But if time is only thought to move forwards or in one direction as we preceive it now, living our lives out in this SpaceTime, then having multiple universes or some of this new thinking may lead one to be able to travel back in time, although only to another universe, or forward in time, although only through having multi-universes.
But, according to Dr. Hawking the laws of physics may have some type of chronology protection to it, so traveling to the Past would be kind of forbidden. But according to Godel and others who worked on some math, it is quite clear that Einstein's formula allows a sort of time travel, where it can work with that Einstein-Rosen Bridge -- now called a wormhole through Space, and connect two regions of Space, where it would be possible to arrive at another Star and make it back to where you began your journey, before you left to go on your journey in the first place.
But again, more experiments and thoughts and math have to be done, before any of it moves out of the realm of science-fiction -- including warp drive as in Star Trek, or a Star-gate as in StarGate SG1.