Question

What will happen if we travel at a speed greaterthan speed of light?

Answer 1

Technically no, but we can travel arbitrarily far in a given time period. It's possible, for example, to travel 200 light-years in 100 years because of a phenomenon called time dilation (Time dilation). Practically speaking it would be very difficult and we probably won't accomplish it this millennium, but it's entirely consistent with Einstein's theory of relativity. In fact it's an essential part of the theory of special relativity.

Stephen Hawking explains why in his "Into the Universe" series with the following example. Suppose you're on a very fast train that's going at 99% of the speed of light. If a child within the train starts running fast enough a person standing outside would observe the child to be moving faster than light. The laws of special relativity account for this by slowing down time for the child just enough, so that an observer outside the train would never see the child moving faster than light. This has been experimentally verified by looking at muons (Muon). Muons decay with a certain half-life at slow speeds. But when accelerated to close to the speed of light it takes them much longer to decay. From the muon's point of view it's still the same amount of time but we perceive it to be much longer since we see the muon's time to be slowing down.

The amount of energy needed to accelerate a person to such speeds would be very large, assuming it were practically possible. If you had the entire world's supply of energy for one year, and assuming perfect efficiency which is often very far off, you could accelerate a person fast enough to produce a time dilation of 1 + E_world / (m_person * c^2) = 70. That person could travel 7000 light-years within 100 years. If you could harness the entire mass-energy of the Sun you could travel across the observable universe (Observable universe) in 2 weeks, without violating special relativity. Of course practical issues are another matter.