Drive by science

[Dragar]

Originally Posted by JoeP

HOW CAN THERE BE GAPS IN SPACE?

It's really best not to think of this way at all.

When you write down Einstein's equations for gravity, you have one term that describes the curvature of space time, and one term that describes the combined energy-momentum of matter. So energy/momentum bends spacetime - it gravitates. (The addition to this equation is that the curvature of spacetime describes the way matter moves through it - matter tells spacetime how to curve, and the curvature of spacetime tells matter how to move.)

Now, there's a weird thing where isn't the most general form of the field equations. There's another, perfectly consistent form, which is where you have an extra term - a constant (I'm sloppily describing the mathematics here, but it's good enough).

For small values of that constant, it's pretty undetectable in everyday life. And it can live on either side of that equation. It can be matter, or it can be curvature.

This term, it turns out, perfectly describes the accelerating expansion of the universe - what's now termed 'dark energy'. On large scales (for for a particular sign, depending on which side of the equation it is) it functions as repulsion between matter.

But because we don't have a physical interpretation for this mathematics, you can either view it as some sort of matter with a very odd behaviour (you can't ever 'dilute' it - if you consider it in more space, there's just more of it in terms of its gravitational effect, so the energy density is always the same) or as a sort of intrinsic addition to the curvature of even empty spacetime. Really, we don't know what it is.

Also, space doesn't expand. Stuff gets further apart.

Now, that's dark energy. Dark matter is much more boring. It's just matter that doesn't glow (hence 'dark'). The dark energy was discovered later and seemed to acquire the same moniker, but it's really very different and probably needs a better name (I like Sean Carrol's 'smooth tension', but it never really caught on).

[BrotherMan]

It's tough for a newblet like me to know when I'm getting a good condensed analogy for some of the higher physics.

[JoeP]

Originally Posted by BrotherMan

It's tough for a newblet like me to know when I'm getting a good condensed analogy for some of the higher physics.

This really needs a one-smilie response, but I'm struggling to choose between several obvious candidates. Magic 8-ball? ...

[BrotherMan]

CRIKEY! LOOKIT THE SIZE OF THIS THING.

Divers dwarfed by an enormous sunfish - YouTube

[erimir]

Zelda DX Link's Awakening- Manbo's Mambo - YouTube

[ceptimus]

[Kyuss Apollo]

Having watched pretty much all the worthwhile documentary offerings on Netflix, am now working my way through the collection on Amazon Prime. Thoroughly enjoying Neil deGrasse Tyson on NOVA ScienceNOW.

[SR71]

A Dyson sphere or similar can't be ruled out (yet). There is this star, and the brightness varies a lot on a non-periodic time line, as if something is getting in the way. A new, strange thing in the vacuum of space.

Has Kepler Discovered an Alien Megastructure? : Discovery News

It might be a long shot, and the phenomenon is more likely a clump of comets or some other natural phenomenon that we haven’t accounted for blocking star light from view, but it’s worth investigating, especially if there really is some kind of alien intelligence building structures, or perhaps, ancient structures of a civilization long-gone, around a star only 1,500 light-years away from Earth.

[BrotherMan]

I would think you could easily rule out a Dyson Sphere seeing as a whole sphere would completely obscure the light/energy source.

[Dingfod]

Perhaps an incomplete or derelict ancient Dyson sphere?

[JoeP]

Some kind of Dyso sphere or Dy on sphere, perhaps.

[Dingfod]

Or perhaps just a Dyson Swarm.

[JoeP]

It's a Type II civilisation being attacked by another one.

[Dingfod]

Possible famous last words: "They'll never take the Sphere, Sire, it's impregnable, invincible."

[Dingfod]

Originally Posted by Dingfod

Or perhaps just a Dyson Swarm.

Ringworld!

[BrotherMan]

Could be Galactus.

[SR71]

Originally Posted by BrotherMan

I would think you could easily rule out a Dyson Sphere seeing as a whole sphere would completely obscure the light/energy source.

Well noborty can just complete a Dyson sphere overnight, ya know.
It takes time. The vacuum of space and so forth...

[JoeP]

I see what you did there ... vacuum of space ...

Back on topic, are you suggesting that this signal indicates a nearly-complete Dyson sphere? Soon to be fully operational?

[SR71]

Originally Posted by JoeP

I see what you did there ... vacuum of space ...

Back on topic, are you suggesting that this signal indicates a nearly-complete Dyson sphere? Soon to be fully operational?

It would be really srsly cool if it did, but it's probably just some other mundane space stuff that we haven't puzzled out yet. Whatever it is, it's big! A 20% occlusion is yuge, right? It's got to be something something mundane arranged in dramatic way (unless it's something someborty maded out there ).

[Ari]

Appropriate for this month, a scientist live tweets watching spiders get it on.
Catherine Scott Spent All of Friday Afternoon Waiting for Her Spiders to Have Sex

[JoeP]

We need this smilie - ::::(

[The Lone Ranger]

Originally Posted by Ari

Appropriate for this month, a scientist live tweets watching spiders get it on.
Catherine Scott Spent All of Friday Afternoon Waiting for Her Spiders to Have Sex

I've definitely had days like that.

[Dragar]

Originally Posted by Ari

Appropriate for this month, a scientist live tweets watching spiders get it on.
Catherine Scott Spent All of Friday Afternoon Waiting for Her Spiders to Have Sex

And it leaves it on such a cliffhanger of an ending.

[Dingfod]

Imagine waiting over 50 years for it to happen, and then you die before it does.

[SR71]

EM Drive is reportedly still producing thrust after another round of NASA testing - ScienceAlert

"And yet the anomalous thrust signals remain..." Mach wrote on the NASASpaceFlight forums.

You can't explain that. Nobody can explain it.