[ExI] Seeing isn't believing

[BillK]

Weird energy beam seems to travel five times the speed of light.
Joshua Sokol  22 May 2017

<https://www.newscientist.com/article/2131889-weird-energy-beam-seems-to-travel-five-times-the-speed-of-light/>

Quotes:
An energy beam that stabs out of galaxy M87 like a toothpick in a
cocktail olive is pulling off the ultimate magic trick: seeming to
move faster than the speed of light. Almost five times faster, in
fact, as measured by the Hubble Space Telescope. This feat was first
observed in 1995 in galaxy M87,  and has been seen in many other
galaxies since.
It might have you questioning your entire reality. Nothing can break
the cosmic speed limit, right? You can’t just flaunt the laws of
physics… can you?

Explanation:

To understand the illusion, picture a single glowing blob of plasma
starting at the base of this path and emitting a ray of light, both of
which travel towards Earth. Now wait 10 years. In that time, the blob
has moved closer at a sizeable fraction of the speed of light. That
gives the rays emitted from that later position a few light years’
head start on the way to us.

If you compare the first and second images from Earth’s perspective,
it looks like the blob has just moved across the sky to the right. But
because the second position is also closer to us, its light has had
less far to travel than it appears. That means it seems to have
arrived there faster than it actually did – as if the blob spent those
10 years travelling at ludicrous speed.

And although the faster-than-light effect is old hat to her, she still
stops to appreciate it sometimes. Most things we see travelling across
the sky, such as planets and comets, are close to us. But M87 is tens
of millions of light years away. “We can see, over a human lifetime,
things moving,” she says. “Which is crazy.”
----------------------

BillK