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Some thoughts I've been thinking about.

  1. Sep 21, 2004 #1
    Predisposition's aside, I've been thinking about a whole bunch of stuff. I'm not even sure if they're questions.

    1) If we assume when a spaceship is moving at the speed of light, it has infinite mass. In order for a ship with infinite mass to move, it would require infinite energy. Since the fuel is moving at the same speed, it would also have infinite mass as well. If the fuel with infinite mass is turned into energy, would it not then give us our required infinite energy?

    2) Assuming we did have spaceships which could move at the speed of light, unlike many TV shows/programs, it would not be my great great great grand children to get to the destination, it would be me, even on a trip of several thousand light years. This is because Time onboard the ship would be frozen. I would start the trip, and finish the trip, in less than a blink of an eye.

    Of course, everyone I ever knew has now died of old age. I can not help but think of how a society would function in a state of "Never see the same person twice". You could take a trip to work, and by the time you get there, your place of business could of gone bankrupt 100 years ago. And by the time you get back, you might not even have a house!

    3) It has been talked about before but I never really found an answer; Escape Velocity is a one shove and free ride deal, correct? You can not get away from a black hole because EV is greater than the speed of light. But what if, instead of using just one shove, you use a constant supply of force untill you was safely away? Would that work?

    Thank you for reading this.
  2. jcsd
  3. Sep 21, 2004 #2


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    1) It's not physically possible for something massive to go the speed of light, or to have infinite mass. Since the premise is unphysical, there really is no answer. It's not a valid question.

    2) This is correct.

    3) The escape velocity is greater than c inside a black hole's event horizon. It is less than c outside the event horizon, and c exactly at the event horizon.

    There is no way for any object inside the event horizon to ever escape. However, if you are outside the event horizon, and equipped with a suitably powerful thruster, you can certainly escape.

    - Warren
  4. Sep 21, 2004 #3


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    1) As the vehicle approaches the speed of light, the mass of the fuel (and therefore the energy available form it) does increase. Near lightspeed, the fuel has nearly infinite mass (a meaningless term, but you know what I'm sayin'). The increase in the mass of the ship, and therefore the power requirement to accelerate it, will allways be just a little more than the increase in power output from the fuel. IOW, you'll have nearly infinite mass in your fuel, which can convert to nearly infinite power, which will allways be nearly enough to reach lightspeed. But never quite.

    3) The reason it would not work is because there is more than just plane escape velocity to worry about. Inside the EV, escape velocity is indeed > c. But this fact is just an indicator, pointing to a much greater problem. The reason escape valocity is > c is because of how bent spacetime is inside the EH. It is this curvature with which one must contend, and it creates a most daunting state of afairs. It Means that a person inside the EH exists in a space in which all paths lead to the center. If your route traverses normal spacetime, your course is directed toward the center of the BH. Any thrust you expend will go toward that destination. To escape the EH, you would need to take a route that travells outside of normal spacetime (which is exactly what you'd have to do to Exceed lightspeed, as well).
  5. Sep 22, 2004 #4
    For question 3, I was thinking more along the lines of flying a probe that almost touches it, rather than trying to fly out of a black hole.
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