Would an object appear frozen while crossing into the threshold

[Cosmo Novice]

Just as a note I am new to these forums and this is my first post after reading for a little while, I have no technical expertise and am a complete layman. So any advice on posting is welcome.

From reading threads on these forums discussing properties of black holes and event horizons as I understand it when an object passes the threshold of the event horizon of a black hole it can no longer escape the gravity of the BH and neither can any photons. Subjectively for the object it would fall into the hole in an ordinary timeframe reference depending on the gravity of the BH. To an outside observer the object would appear frozen on the edge of the BH. I read that theoretically the image would be visible to an outside observer infinitely but surely at some point the last photon emmited by the object as it fell over the event horizon would reach the objective observer? Would the photons emmited become increasingly redshifted?

 

[mathman]

The photons are increasingly red shifted to the outside observer.

 

[Cosmo Novice]

The photons are increasingly red shifted to the outside observer.

But theoretically if you could watch objectively for an immense amount of time in the order of magnitude of however long would be required you would eventually see it cross into the threshold or would it be redshifted to such an extent we cannot perceive it?

 

[cosmik debris]

But theoretically if you could watch objectively for an immense amount of time in the order of magnitude of however long would be required you would eventually see it cross into the threshold or would it be redshifted to such an extent we cannot perceive it?

Yes pretty much, you will never it cross the threshold but the image will red shift until the image is gone.

 

[Chalnoth]

Yes pretty much, you will never it cross the threshold but the image will red shift until the image is gone.

Well, technically, it will never be completely gone. In time, the image will be so redshifted that it is too faint to see in the visible. Then we might still be able to see it in the infrared, then later in the microwave, then later in the radio. At some point it will just be too difficult to detect at all, but it will never be completely "gone".

 

[Cosmo Novice]

Well, technically, it will never be completely gone. In time, the image will be so redshifted that it is too faint to see in the visible. Then we might still be able to see it in the infrared, then later in the microwave, then later in the radio. At some point it will just be too difficult to detect at all, but it will never be completely "gone".

Chalnoth I appreciate what you are advising (that the photons will become increasingly redshifted) until they are no longer detectable. At this point however, once the protons have redshifted to an extent thay are not detectable on the EMS at all then is this just a case that we can no longer detect the photons or that the photons are no longer being emmitted? At some point the last photon must cross the threshold of the EH? Even if this was to subjectively take a near infinite amount of time eventually (Given infinite timeframes) would the last photon reach the observer?

You say the object "will never be completely gone" but the protons traveling from the object prior to its entry into the EH are not infinite in amount, and although timescales tend towards the infinite at some point the image must be completely gone?

 

[Chalnoth]

Chalnoth I appreciate what you are advising (that the photons will become increasingly redshifted) until they are no longer detectable. At this point however, once the protons have redshifted to an extent thay are not detectable on the EMS at all then is this just a case that we can no longer detect the photons or that the photons are no longer being emmitted?

Well, it's not that they stop being emitted. Rather, the photons that are emitted at the time the object crosses the horizon arrive here after an infinite amount of time. So the photons that are emitted as the object was closer and closer to the horizon arrive later and later, after more and more time.

Then all modern medicine You say the object "will never be completely gone" but the protons traveling from the object prior to its entry into the EH are not infinite in amount, and although timescales tend towards the infinite at some point the image must be completely gone?

Well, right. I was speaking in the classical approximation, not about discretized photons. So yes, if you take into account the fact that light is made up of photons, eventually the last photon will arrive. But for the most part the object in question will have become undetectable long before then (and, technically, we will have also all ceased to exist by that time too).

 

[dm4b]

Well, it's not that they stop being emitted. Rather, the photons that are emitted at the time the object crosses the horizon arrive here after an infinite amount of time. So the photons that are emitted as the object was closer and closer to the horizon arrive later and later, after more and more time.

So, they do stop getting admitted within the frame of the object that crossed the Horizon, but time is so incredibly dilated it appears they never stop getting emitted in our frame outside the Horizon. Is that correct?

However, they eventually get redshifted into oblivion anyhow.

Anyhow, I guess that's how I always understood, but wasn't sure if you guys were saying the same thing?

 

[Chalnoth]

So, they do stop getting admitted within the frame of the object that crossed the Horizon,

No, they don't stop getting emitted. They keep getting emitted. It's just that the photons that are emitted after horizon-crossing can never reach us.

but time is so incredibly dilated it appears they never stop getting emitted in our frame outside the Horizon. Is that correct?

This is more or less accurate, yes. We only see the photons emitted before horizon crossing, but dilated so that the arrival of those photons is spread over infinite (or nearly infinite) time.

 

[dm4b]

No, they don't stop getting emitted. They keep getting emitted. It's just that the photons that are emitted after horizon-crossing can never reach us.

Well, I just meant wouldn't they eventually stop getting emitted because the ultimate fate of everything inside the Horizon is the singularity? Once the said object is destroyed, no more emission.

 

[Chalnoth]

Well, I just meant wouldn't they eventually stop getting emitted because the ultimate fate of everything inside the Horizon is the singularity? Once the said object is destroyed, no more emission.

Well, that happens a little bit after horizon crossing. What happens after horizon crossing is irrelevant to these considerations.