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kasse
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I talked to an astronomy student recently, and he told me that if I travel out from Earth in a straight line, I will finally return to earth. Is this true?
kasse said:But if the universe has a curvature, it will be practically impossible to travel in a straight line and return to earth, no?
That is correct, there are no straight lines in a curved space-time.kasse said:But if the universe has a curvature, it will be practically impossible to travel in a straight line and return to earth, no?
I would not go that far in saying that.HallsofIvy said:If this person told you that would result because the universe is "bent in higher dimensions" he didn't know what he was talking about!
Chronos said:The universe is expanding too rapidly for any traveller to return to their point of 'origin', irrespective of curvature.
You are right. I had interpreted "bent in higher dimensions" as meaning "curled up in some dimensions". I think your interpretation as "embedded in higher dimensions" it better.MeJennifer said:That is correct, there are no straight lines in a curved space-time.
The thing that comes closest is a so-called geodesic.
But even then it is not automatically true that if you travel away from A along a geodesic you will meet A again, even if space-time has a positive curvature.
I would not go that far in saying that.
While it is custom to describe curved space-time as intrinsic curvature, it would not be impossible to embed it in a higher dimension.
kasse said:I talked to an astronomy student recently, and he told me that if I travel out from Earth in a straight line, I will finally return to earth. Is this true?
heusdens said:This can quite definitely be ruled out, because of the expansion of space.
Even when sending out a light signal, it can never catch up with the drift of space at large, because of the space expansion.
So, ultimately, this has the effect of that in all respects, the universe can best be seen as infinitely large.
The exact time it takes to travel a round trip to Earth in a straight line depends on the speed of the spacecraft and the distance between the starting point and Earth. However, with current technology, it would take approximately 8 months to travel to Mars and back to Earth in a straight line.
The shortest distance between Earth and another planet for a round trip in a straight line is approximately 54.6 million kilometers, which is the distance between Earth and Mars at their closest approach. This distance can vary depending on the position of the planets in their respective orbits.
With current technology, it is not possible to travel a round trip to Earth in a straight line without stopping. Spacecrafts would need to refuel and resupply along the way, and the human body is not equipped to withstand such a long journey without breaks for rest and nourishment.
The potential risks of a round trip to Earth in a straight line include exposure to radiation and other hazards of space travel, such as microgravity and isolation. There is also a risk of technical malfunctions or human error during the journey, which could have serious consequences.
Traveling in a straight line to Earth would require a much more powerful spacecraft and advanced navigational systems compared to traditional orbital trajectories. The spacecraft would also need to be able to withstand the intense pressure and heat of entering and exiting Earth's atmosphere at high speeds.