Speeding into a supersize black hole

In summary, the galaxy NGC4261 is believed to contain a black hole that weighs about one hundred thousand times as much as our sun, with a diameter the size of our solar system. The black hole has a gravitational field that is nearly infinite in magnitude, but the spaceship is not accelerated to above light speed before it falls into the black hole.
  • #1
Anders Lundberg
9
0
The galaxy NGC4261 is believed to contain a black hole that weighs about one hundred thousand times as much as our sun, with a diameter the size of our solar system. (http://www.damtp.cam.ac.uk/user/gr/public/bh_obsv.html)

Now, imagine that we clear the space around the black hole and use some kind of spaceship to first build up a near light speed velocity. Then, from a distance of a few "light days" (we suppose that this black hole has a diameter of almost a "light day") we aim straight at the black hole, turn off the engines and just plainly falls towards it.

My question is; If the spaceship already is at very near light speed, why doesn't the massive gravitational field from the black hole manage to accelerate the spaceship to above light speed before it reaches the black hole? Any relativistic mass increase of the spaceship would not make any difference since it is accelerated by a gravitational field (and not by its engines), so what is stopping it?
 
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  • #2
What happens when things fall in a gravitational field? They gain kinetic energy.

There is no limit on kinetic energy. You can fall towards a black hole and gain nearly infinite amounts of kinetic energy.

But nearly infinite amounts of kinetic energy are not enough to travel faster then the speed of light. Better luck next time.
 
  • #3
Some thought needs to be given as to how the velocity is being measured. For instance, the coordiante velocity dr/dt for an object falling into a black hole will be zero! The most convenient number is not a velocity, but a rapidity - dr/dtau, which is the rate of change of the Schwarzschild coordinate 'r' with the proper time 'tau'.

For more on rapidities in SR see for instance

http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html
 

Related to Speeding into a supersize black hole

1. What is a supersize black hole?

A supersize black hole is a massive and extremely dense object in space that has a gravitational pull so strong that even light cannot escape from it.

2. How fast can one travel while speeding into a supersize black hole?

The speed at which one would travel while entering a supersize black hole depends on the size and mass of the black hole. However, the speed would be incredibly fast, likely close to the speed of light.

3. Is it dangerous to enter a supersize black hole?

Yes, it is extremely dangerous to enter a supersize black hole. The strong gravitational forces within a black hole can tear apart anything that enters it, including stars and planets.

4. Can anything survive entering a supersize black hole?

It is highly unlikely that anything can survive entering a supersize black hole. The intense gravitational forces and radiation would most likely destroy any form of matter.

5. How do scientists study or observe supersize black holes?

Scientists study and observe supersize black holes by using various tools, such as telescopes and other instruments, to detect the effects of their strong gravitational pull on surrounding matter. They also use simulations and mathematical models to understand their behavior and properties.

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