Answer: they bring something that they got in there journey like a rock
Explanation:here a short story that have more info-
The Time Traveller flies into the future with a greater velocity than before. Although he is travelling thousands of years per second, he begins to notice day and night again. The sun grows larger and redder. Finally, it seems that the earth has stopped rotating, and is circling the dying sun as the moon used to circle the earth.
When he brings the machine to a stop, he finds himself on a sloping beach. Vegetation covers every surface facing the unmoving sun; the air is very thin. Behind him he sees a huge white butterfly in the distance, and slowly a red rock begins to move toward him. It turns out to be a giant crab. While he is staring at it, he feels something brush his neck. It is the antenna of a second giant crab, right next to him. He hurriedly skips a month into the future to escape, but finds the beach covered with more crabs. He goes on, stopping every hundred years or so, watching the "old earth ebb away." Finally, thirty million years into the future, he comes to a stop. The air is bitter cold, and the only sign of life is lichen on the beach. Small flakes of snow float in the air. A large disc begins to eclipse the sun; the Time Traveller suspects that some inner planet, perhaps Mercury, which is now much closer to Earth, is passing in front of the sun. An incredible darkness and blackness follows. On the verge of fainting, he climbs back on the machine, and as he does he notices a black blob with tentacles flop over in the distance. It is the only evidence of animal life.