APOD: The Changing Surface of Fading... (2020 Feb 17)

[neufer]

Light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002.

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200 days of Betelgeuse observations

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[Guest]

Surely you are not proposing that we should revoke the laws of physics and transport ourselves instantly across the light-years to see what the star or galaxy looks like "now",

Oh, Honey, if only we could! I would give some majorly interesting organs to have an F.T.L. Starship, especially one that could do micro-jumps so we could take a historical animation of distant things as they "really" evolved into what they "are today". Assuming absolute cosmic time is a real thing, which it probably isn't.

or else shut up and admit that we know nothing about the Universe?

Ann

Well, we know a tiny bit about the cosmos and we're fairly sure about a little more but there are vast blank "Here Be Dragons" spaces in the pictures. That's what make Science a career not a way of passing a few hours while you bone up on all of it. We may never know all there could be to know; we may never know even how much there could be to know and how much we do not know [in the 1860's we didn't know that we were ignorant of radioactivity, elemental isotopes and huge swathes of chemistry and biology among other stuff but we did know we were ignorant of a lot of stuff related to the very little we did then know] [ummm, okay, that sounds right ... ]. The cosmos is big and complex and evolving and may poof itself out of existence without warning should it be a false vacuum, we may well never stop having deep and colossal questions about it.

Science is fun.

For an everyday example of what we don't know, we don't know if Betelgeuse is going to kaboom in the Northern Hemisphere Summer but, knowing my luck that's exactly what "happened in 1376". Yet another thing I'll miss. And it's probably raining, too.

[Ann]

Surely you are not proposing that we should revoke the laws of physics and transport ourselves instantly across the light-years to see what the star or galaxy looks like "now",

Oh, Honey, if only we could! I would give some majorly interesting organs to have an F.T.L. Starship, especially one that could do micro-jumps so we could take a historical animation of distant things as they "really" evolved into what they "are today". Assuming absolute cosmic time is a real thing, which it probably isn't.

or else shut up and admit that we know nothing about the Universe?

Ann

Well, we know a tiny bit about the cosmos and we're fairly sure about a little more but there are vast blank "Here Be Dragons" spaces in the pictures. That's what make Science a career not a way of passing a few hours while you bone up on all of it. We may never know all there could be to know; we may never know even how much there could be to know and how much we do not know [in the 1860's we didn't know that we were ignorant of radioactivity, elemental isotopes and huge swathes of chemistry and biology among other stuff but we did know we were ignorant of a lot of stuff related to the very little we did then know] [ummm, okay, that sounds right ... ]. The cosmos is big and complex and evolving and may poof itself out of existence without warning should it be a false vacuum, we may well never stop having deep and colossal questions about it.

Science is fun.

For an everyday example of what we don't know, we don't know if Betelgeuse is going to kaboom in the Northern Hemisphere Summer but, knowing my luck that's exactly what "happened in 1376". Yet another thing I'll miss. And it's probably raining, too.

Trolltunga cliff, Norway.

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Oh, honey (sorry for getting back at you), no, I guess you're right. After all, the diameter of the observable Universe is supposed to be some 93 billion light-years, and then there is all the rest, the parts we can't observe, outside of it. That's quite a lot of cosmic real estate to chart and describe down to its smallest Planck length or vibrating string.

And Betelgeuse hides its secrets behind hundreds of millions of outer layers, which creates an opaque shroud around the blistering core, which is the part of Betelgeuse that decides when the star will go ka-boom, after all. So it's hard to predict just when Orion's ruddy supergiant will go. Let's see... on October 9, 2525, at 3.43 p.m., GMT?

That cosmic speed limit is a dastardly thing, too. Yes, I've read about that false vacuum thing. It's like being caught on a cosmic ledge overhanging an abyss. If that cosmic ledge gives way then we are it, crashing down into that bottomless chasm. More interesting still is the possibility that another part of our Universe may already have "plunged into darkness", creating the most unbelievable cosmic tsunami that would be crashing our way at the speed of light.

And we wouldn't know what was going to hit us until it hit us. Ouch.

Like you said, though. No, we don't know everything. And if you ask me, we never will.

But we may be learning new things all the time, which is incredibly fascinating.

Ann