[nudephil (OP)]

We had the following emailed in from Marvin:

Imagine standing beside a supersonic aircraft when it takes off. At it accelerates away from us, we can hear the sound intensity slowly fade as it becomes more distant. But the thing is, we can still hear the sound, because sound travels at a speed of 1,234 km/hour (340 m/second). Now imagine the aircraft accelerates to a speed faster than the speed of sound: the sound it makes can't reach us. What has happened is that the aircraft is moving so fast, it has gone past an event horizon.

Imagine the same aircraft flies into the centre of a black hole. It's speed increases to the speed of light (300,000 km/second) and even faster, so that the light it emits is no longer visible to us. That is also called an event horizon; the point when the object is moving away from us faster than the speed of light.

So would you agree that moving faster than the speed of light is a possibility? Just because we can't see or measure something, doesn't mean it isn't there.

Any thoughts?

[Halc]

Imagine standing beside a supersonic aircraft when it takes off. At it accelerates away from us, we can hear the sound intensity slowly fade as it becomes more distant. But the thing is, we can still hear the sound, because sound travels at a speed of 1,234 km/hour (340 m/second). Now imagine the aircraft accelerates to a speed faster than the speed of sound: the sound it makes can't reach us.

You can still hear the receding aircraft, since no matter how far away it is, the sound still comes to you at 340 m/sec relative to the medium (the air). It's the aircraft that can't hear you after it passes, since your sound can't catch up to it.
It is the approaching aircraft that you can't hear until after it passes as it outruns its own sound.
Light isn't like that since there is no medium relative only to which light travels at c. It travels at c relative to any inertial reference frame, regardless of the speed (relative to that frame) of the object emitting the light.

Imagine the same aircraft flies into the centre of a black hole. It's speed increases to the speed of light (300,000 km/second) and even faster.

Its speed is relative to a coordinate system of choice, and without specification of your choice, this statement is ambiguous. The coordinate speed of the aircraft (speed relative to Earth say, in Earth frame) actually decreases and the aircraft never reaches the event horizon in Earth frame.  The speed relative to the aircraft is always zero, by definition, and somebody on it would not be able to tell when the event horizon was crossed as nothing particularly unusual would change at that point.

so that the light it emits is no longer visible to us.

Light (or anything else) emitted by it would indeed be unable to reach us after the event horizon is crossed. This is very unlike the aircraft which can be heard after it passes despite it moving at supersonic speeds. The future light cone of the craft inside the event horizon does not include any events outside the event horizon.

That is also called an event horizon; the point when the object is moving away from us faster than the speed of light.

An event horizon (relative to location Y) is a point where a cause X can no longer have at effect at Y. This is not necessarily light speed. So for instance, the Hubble distance (where stars are receding at light speed) is about 14 billion light years away, but the event horizon is about 16 billion light years away. That means that light currently emitted from stars receding at a bit over c will still eventually reach us, just like light is reaching us now from stars with recession velocities far in excess of C.  GN-z11 for instance is receding at over twice light speed, but we can see it.

So would you agree that moving faster than the speed of light is a possibility?

Depends how you measure it. I'd agree to that. Only locally does light travel at exactly c in a vacuum. I can put a reflector on Pluto and shine a light to it and it comes back in less time that the distance/c. It's because it isn't a local experiment, and most of the trip is done at locations of higher gravitational potential, where light moves faster than c relative to the low-potential frame of Earth.

[Marvin Thunderbolt]

Much respect to OP @nudephil for posting the question I've been contemplating for a while, thanks also for anyone who would like to share their thoughts.

[Bored chemist]

It's speed increases to the speed of light (300,000 km/second) and even faster

No.
Not faster.

the point when the object is moving away from us faster than the speed of light.

No
Not faster.

At the speed of light is enough to make sure the light never reaches us.

So would you agree that moving faster than the speed of light is a possibility?

No.