- #1
Javier Zapater
- 4
- 0
Dear Sirs
My question relates to the recent observation of gravitational waves by LIGO.
The paper PRL 116 "Observation of Gravitational Waves from a Binary Black Hole Merger -B.P Abbott et al"" depicts the chirp signal of the wave detected, where it is seen how both frequency and amplitude increase till coming to an end, where oscillations stop, indicating that both BHs coalesce into single one.
Question: why do we see that end in the gravitational wave signal? in short, why we see the coalesce? I mean, I would have expected (surely wrong) that we, as external observers should have "seen"/detected the two BH, meanwhile approaching both event horizons to the final merge, suffering an increasing redhsift during the collapse that would have prevented us from detecting that one BH crossed the event horizon of the companion, and viceversa. Similar effect as if we, meanwhile remaining in orbit around a BH, see an object falling into the BH. We will see the light emitted by the object gradually and infinitely redshifted meanwhile approaching the event horizon.
Should not the gravitational waves suffer from the same collapse redshift observed as in the electromagnetic waves?
Where is my reasoning wrong?Thanks for your help.
javier
My question relates to the recent observation of gravitational waves by LIGO.
The paper PRL 116 "Observation of Gravitational Waves from a Binary Black Hole Merger -B.P Abbott et al"" depicts the chirp signal of the wave detected, where it is seen how both frequency and amplitude increase till coming to an end, where oscillations stop, indicating that both BHs coalesce into single one.
Question: why do we see that end in the gravitational wave signal? in short, why we see the coalesce? I mean, I would have expected (surely wrong) that we, as external observers should have "seen"/detected the two BH, meanwhile approaching both event horizons to the final merge, suffering an increasing redhsift during the collapse that would have prevented us from detecting that one BH crossed the event horizon of the companion, and viceversa. Similar effect as if we, meanwhile remaining in orbit around a BH, see an object falling into the BH. We will see the light emitted by the object gradually and infinitely redshifted meanwhile approaching the event horizon.
Should not the gravitational waves suffer from the same collapse redshift observed as in the electromagnetic waves?
Where is my reasoning wrong?Thanks for your help.
javier
