Register to reply

Blackhole can be relative?

by luxiaolei
Tags: blackhole, relative
Share this thread:
Feb28-10, 07:00 AM
P: 75
Hi,all, the problem is:

you and me observe a star, and the star moving with velocity V relative to me, and you are in the rest frame of the star.

Then in my frame of reference, I saw the star length contraction in the direction of its motion relative to me, hence its volume is smaller than its proper volume, and its mass is greater than its rest mass. Then I calculate its gravitational constant, say a.

And you calculate its gravitation constant as well, say you got a'

since i observe smaller volume and larger mass, so a>a'

if a just reach the limit that light can not escape from that star.

Then it will result in, In my frame, that star is a blackhole, and in your frame, that star is Not.

however reality is invariant under lorentz transformation, so this can not be true, but where am I wrong??

Thanks in advance!
Phys.Org News Partner Science news on
An interesting glimpse into how future state-of-the-art electronics might work
Tissue regeneration using anti-inflammatory nanomolecules
C2D2 fighting corrosion
Vanadium 50
Feb28-10, 09:09 AM
Vanadium 50's Avatar
P: 16,321
The answer is on the usenet physics FAQ.
Feb28-10, 09:33 AM
P: 75
Quote Quote by Vanadium 50 View Post
The answer is on the usenet physics FAQ.
@Vanadium; thanks for replay, however the link you gave only refer to the star become a blackhole or not relative to an observer in its rest frame. My question is 2 different observer in two different frame of references, observes same star.
(btw, I dont quite understand under what condition one can form a blackhole)
But thanks again.

Register to reply

Related Discussions
What happens when an anitmatter blackhole collides with a matter blackhole? Astronomy & Astrophysics 6
M87 Blackhole Astronomy & Astrophysics 3
Entropy in a blackhole Special & General Relativity 3
Absorb all sort of matter and radiations and still not releasing out? Astronomy & Astrophysics 13
Yet another blackhole theory Special & General Relativity 5