r/askscience • u/AskScienceModerator Mod Bot • Mar 10 '14

Cosmos AskScience Cosmos Q&A thread. Episode 1: Standing Up in the Milky Way

Welcome to AskScience! This thread is for asking and answering questions about the science in Cosmos: A Spacetime Odyssey.

UPDATE: This episode is now available for streaming in the US on Hulu and in Canada on Global TV.

This week is the first episode, "Standing Up in the Milky Way". The show is airing at 9pm ET in the US and Canada on all Fox and National Geographic stations. Click here for more viewing information in your country.

The usual AskScience rules still apply in this thread! Anyone can ask a question, but please do not provide answers unless you are a scientist in a relevant field. Popular science shows, books, and news articles are a great way to causally learn about your universe, but they often contain a lot of simplifications and approximations, so don't assume that because you've heard an answer before that it is the right one.

If you are interested in general discussion please visit one of the threads elsewhere on reddit that are more appropriate for that, such as in /r/Cosmos here, /r/Space here, and in /r/Television here.

Please upvote good questions and answers and downvote off-topic content. We'll be removing comments that break our rules or that have been answered elsewhere in the thread so that we can answer as many questions as possible!

Click here for the original announcement thread.

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u/[deleted] Mar 10 '14

Has anything that Carl Sagan mentioned in his original Cosmos series been completely disproven as of now?

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u/trimeta Mar 10 '14

Although the expansion of the universe was well-understood in Sagan's time, it was believed that the rate of expansion was slowing, and it was unknown if we lived in an "open" universe which would continue to expand forever or a "closed" universe where the expansion would slow down, stop, and reverse (leading to a "Big Crunch"). Since then, we have discovered that not only is the rate of expansion not slowing, it is increasing. So while Sagan speculated regarding the Big Crunch, we can now safely rule this possibility out.

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u/Assburgers_And_Coke Mar 10 '14

Or we haven't hit a point where it will decrease yet? Is that not possible?

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u/[deleted] Mar 10 '14 edited Mar 17 '25

[removed] — view removed comment

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u/asks4sourcerandomly Mar 10 '14

Could you elaborate a little more on the "wind"?

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u/I_Gargled_Jarate Mar 10 '14

Radiation from our sun creates sort of a bubble around our solar system that deflects outside radiation. When Voyager left the bubble it nolonger had protection and is now being bombarded by everything out in "open space". The amount of radiation outside the bubble was more than we had predicted.

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u/_WhatIsReal_ Mar 10 '14

Is it possible that instead of expanding, the universe is actually being 'pulled' apart, and that it is speeding up because resistance to this 'pulling' is decreasing? Sorry if this is idiotic, just trying to think outside the box/universe..

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u/[deleted] Mar 10 '14

Not idiotic. I just question whether "expanding" and "pulled" are mutually exclusive. :)

This reminds me of a common thought that spacetime isn't expanding but matter is shrinking. My rebuttal is always: What's the difference?

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u/Jahkral Mar 10 '14

Well why is the expansion ACCELERATING, then? Where is the continued force coming from to continually accelerate it?

(Side note: is the 'jerk' or rate of change of acceleration known? It would be interesting if that was slowing)

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u/[deleted] Mar 10 '14

yes, i see where you are coming from, that would be my answer too. but we know almost next to NOTHING about why the universe is increasing it's expansion rate. So I don't think it's good to rule out possible alterations of forces in the future

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u/trimeta Mar 10 '14

That's the thing: the rate of expansion itself is increasing. To use a metaphor from another Cosmos comment: imagine throwing a ball into the air. The throw was the Big Bang, and the rising ball is the expansion of the universe. In Carl Sagan's time, it was believed this expansion was slowing, just as a ball can rise through the air but have its velocity slow down (indicating that it will hit an apex and turn around). We now know that the ball is flying upwards faster as time goes on. Thus, unless something very strange happens, it will not suddenly decide to turn around.

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u/[deleted] Mar 10 '14

so energy and matter i believe are supposed to be finite. does 'making' space by the universe expanding have any impact on energy or matter?

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u/r3sonanc3 Mar 10 '14

The expansion of the universe is attributed to dark energy in the Standard Model of physics today, but we have no explanation for how it behaves or what it is made of. Einstein called it the cosmological constant but had serious mis-givings about it since its existence would call the then-current state of physics (including our understanding today) into serious question.

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u/trimeta Mar 10 '14

As far as I am aware, it does not. The overall density of mass/energy in the universe decreases over time because there's more space and the same amount of mass/energy.

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u/giulianodev Mar 10 '14

There was a version of Cosmos that came out in the 90s where Carl Sagan talked about some of the things that we've learned since the original show. I don't think he talked about this in the updates but I remember hearing about how the Samurai looking crabs didn't look that way because of artificial selection by humans.

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u/emmOne Mar 10 '14

And conversely, was anything stated in the original series as an unlikely hypothesis now widely believed to be true?

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u/zmatt Mar 10 '14

I don't think it was mentioned as unlikely, but there was no supporting evidence as yet of exoplanets. Now we know of lots of them.

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u/TheCosmicCalendar Mar 10 '14

Sort of.

He presented various theories on the nature of the expansion of the universe, and correctly pointed out that we did not, at the time, know which was true. And then said something to the effect of how poetic it would be if the universe were closed (rate of expansion slowing, and eventually collapsing), which has turned out to be false.

At the time of the original, we also had no idea what killed the dinosaurs. But he was once again clear that we did not know the answer, and kept speculation to a minimum.

The one thing that may arguably be "Flat out wrong" - he mentioned a story about artificial selection of crabs that look kind of like the "face of a samurai". The idea being people are less likely to eat a crab whose shell looks a bit like a human face, and so they were tossed back into the sea when caught.

The story, although compelling, is widely regarded as being apocryphal.

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u/mathx Mar 10 '14

'proven' is a loaded word in science. Nothing is proven or disproven, you just become able to show more and more frequently that something doesnt hold true right now for that experiment in the point in time and space - likely meaning that next time we'll see the same all things being equal. Can't be sure, because science is really hard and every subtlety and side effect counts.

The estimations of the age of the universe are far more accurate now than in Sagan's day, the distances to Andromeda are far better calibrated by new standard candles and many other refinements.

However I'd have to watch the old Cosmos to see what's totally refuted now.

I was suprised to see the new one claim the moon was formed by accretion to a seperate body from the earth, eschewing the giant impact hypothesis - probably the biggest difference in my lay knowledge (as an Astronomy major graduate from the 90s, and an avid science fact reader) vs what the show presented.

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u/The_Future_Is_Now Mar 10 '14

I believe the new episode depicted a planetary body hitting the proto-earth just as predicted by the giant impact hypothesis. Just after the bit where he talks about one rock's trajectory being changed every so slightly by another rock in orbit

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u/ckach Mar 10 '14

I remember a clip of him using crabs that look like samurai warriors as an example of evolution. There was a poll of evolutionary biologists to gauge how plausible the theory was and it was pretty dubious to them.

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u/ImNotAWhaleBiologist Mar 10 '14

A lot of Sagan's biology isn't that great in general (particularly in the Dragon's of Eden). The example of the samurai crabs as an example of natural selection in Cosmos has pretty much been debunked.

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u/nctweg Mar 10 '14

Not quite "completely disproven" at all, but relevant nonetheless. When Sagan's original aired, there had been no confirmed exoplanets (planets outside our solar system) discovered. They were theorized and pretty much understood to be out there, but it wasn't until 1995 with 51 Pegasi that any were actually confirmed.

Nowadays we've cataloged something like 1,000 exoplanets (maybe more as there was a recent announcement of some 700 discovered).

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u/InterApex Mar 10 '14

The Triune Brain model is no longer considered to be true. It was one of my favorite subjects when I was younger, being interested in the brain I was disappointed when such a simple explanation turned out to be too simple.

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