The concept of time travel is highly speculative and remains purely theoretical at this point. According to our current understanding of physics, time travel to the past is not possible based on the known laws of nature.
However, for the sake of exploring your question, let's consider a hypothetical scenario where time travel to the past is somehow achievable. If one were to travel back in time, it is true that the Earth, along with the entire solar system, is in constant motion. The Earth orbits the Sun, the Sun orbits the center of the Milky Way galaxy, and the galaxy itself is moving through space.
If you were to travel back in time by a significant duration, such as 400 years, and end up in the same spatial location relative to the Earth, you would indeed find yourself in empty space. The Earth would have moved from its previous position, along with the solar system and the galaxy. This would likely result in a dangerous situation, as you would be left floating in space without any protection or atmosphere.
Moreover, the Earth's position in space is not the only consideration. The configuration of matter and the state of the universe would be different in the past. Planets, stars, and even galaxies may have changed their positions and properties over such a long period.
It's important to emphasize again that time travel to the past is currently considered to be purely speculative. While it makes for interesting discussions and forms the basis of science fiction, no scientific evidence or mechanism has been discovered to suggest that it is achievable within the bounds of our current understanding of physics.