As of our current scientific understanding, it is correct that we cannot exceed the speed of light in a vacuum according to Einstein's theory of relativity. However, space exploration has taken humans and robotic probes to significant distances in both space and time. Here are some explanations:
Space Travel: While we cannot exceed the speed of light, space travel is still possible by employing various techniques. For instance, space probes like Voyager 1 and Voyager 2 have been traveling for decades and have reached the outskirts of our solar system. They achieved these great distances through long-duration missions and utilizing gravitational assists from planets to gain momentum. Human space missions, like those to the Moon, have also covered considerable distances within our own cosmic neighborhood.
Time Dilation: According to the theory of relativity, time is relative and can be affected by factors such as velocity and gravity. When objects or individuals move at high speeds relative to each other or experience different gravitational fields, time can appear to pass differently for them. This phenomenon is known as time dilation. For example, astronauts aboard the International Space Station experience slightly slower time compared to people on Earth due to their high orbital velocity.
Cosmological Expansion: The universe itself is expanding, which means that distant galaxies are moving away from us. Light emitted by these galaxies takes time to reach us, and as the universe expands, the light waves get stretched or redshifted. By observing the light from distant galaxies, astronomers can effectively look back in time and study the early universe.
It's important to note that while we have made remarkable advancements in space exploration, the distances covered are still minuscule compared to the vastness of the universe. Traveling to other star systems or traversing significant distances in space within a human lifetime remains highly challenging using our current technologies.
The concept of time travel to the past, as commonly depicted in science fiction, presents even more complex challenges and is not currently considered feasible based on our understanding of physics.