Which is easier to achieve, immortality or traveling through time and space?

Immortality is easier to achieve. Cancer cells are immortal, refer to "HeLa, the Immortal".

But immortality is against ethics and morals. After all, the earth is so big. If people don’t die, where will the reborn people go? Human immortality should occur after humans have opened up the universe and can migrate to the stars.

To travel through time and space, you must understand the rules of the universe. Human beings have not even left the solar system and explored the universe. Not to mention traveling through time and space. In order to realize time travel, Hawking first suggested that people accept the concept of time as the fourth dimension. He gave a very simple example: when people drive a car, going straight forward and reversing backward are the first dimension, turning left or right is the second dimension, and climbing and going downhill on the mountain road is the third dimension. Then time is the fourth dimension. How can we find the path forward or backward in the fourth dimension?