A Visiting Star Jostled Our Solar System 70,000 Years Ago • Hacker News Board

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#71

Post by maze-le » Thu, Mar 22, 2018, 8:31 PM UTC

Santosh83 wrote: post #57

I wonder what its velocity is in relation to the sun. Twenty two light years in 70,000 years seems rather fast!

It seems to be quite fast, but not exceptionally. Lets do a quick calculation, and neglect all aspects of proper stellar kinematics -- Our sun has traveled quite some distance itself during the 70000 years, I don't properly described that motion itself, so take everything with a grain of salt:

Lets call the speed difference of the star with respect to our sun `Δv`

   Δv = 20 [ly] / 70 000 [y] = 0.000285714 [ly/y]

Now, lets convert the unit `ly/y` into a unit that we can relate to, to get a grasp on it: 1ly = 63241.08AU[1].

   Δv = 0.000285714 [ly/y] = 18.0688 [AU/y]

18 AU is about the perihelion of Uranus, a bit smaller still. So the star traveled on average, with respect to our sun, about the smallest distance between the Sun and Uranus in 1 year. To put that in perspective:

   Δv = 18.0688 [AU/y] * 149597900 [km/AU] / 31557600 [s/y] 
      = 85.6550 [km/s]

The LSR[2] is about 220 km/s. The Suns deviation from this value is about +14 km/s[3]. So an object with Δv of about 85.6 km/s is quite fast in comparison. But this is still nothing compared to hypervelocity stars, wich can be more than 1000 km/s faster and are exceeding the escape velocity of the galaxy.

------

[1] : 1 AU (Astronomical unit) is the average distance from Earth to Sun.

[2] : Local Standard of Rest -- average speed of our stellar neighborhood through the galaxy.

[3]: https://arxiv.org/abs/1411.3572

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#72

Post by chasing » Thu, Mar 22, 2018, 8:32 PM UTC

JoeAltmaier wrote: post #64

chasing wrote: post #22

Earlier quoted context omitted.

That's a minuscule number and "influenced" doesn't necessarily mean "aimed them at the Earth." There's a lot of space out there which it takes things a lot of time to move through. It takes the Earth a year to go around the Sun. And the Oort Cloud is, like, 100,000 times further away from the Sun than we are.

They went into 'v' orbits, which as I understand it, means steep highly elliptical orbits that come inside the Earth's orbit? Its a lot more crowded in here.

I'm no space science maker person. So take this all with a grain of salt. But.

Halley's Comet takes 75 years to make an orbit. It goes out to about 35AU. Let's call that 1 year per AU. That rough, rough number would lead one to conclude that anything from the Oort Cloud moving at a similar speed could take, say, 100,000 years to get here even if it was aimed at us. If triggered by something 70,000 years ago, we'd still have a bunch of millenia to prepare.

Anyway. I'm sure I'm completely wrong.

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#73

Post by squozzer » Thu, Mar 22, 2018, 8:46 PM UTC

vkou wrote: post #63

c-smile wrote: post #50

Again: as sooner we start our resettlement to other star systems - the better.

What about the opportunity cost? What about the long-term? Maybe we should make our ecological footprint steady-state sustainable, first.

I think your idea is more practical, given the state of spaceflight technology - BUT, should it succeed, then little incentive would exist to leave Earth.

Given the impulses of people in power now, coupled with whatever steps the future takes to make Earth sustainable, it's hard to imagine a future government allowing people to leave. It would, after all, be setting up a competitor. Paranoid, you say?

Imagine an English king c. early 1600s having a vision of the descendants of his loyal colonists rebelling 170 years later. And the nation founded by the rebels eclipsing England 130 years after that. History might have turned out differently.

The good news is that thanks to France and Spain, the English king had little choice - he had to oppose France and Spain everywhere he could, or risk losing strategic advantage.

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#74

Post by vog » Thu, Mar 22, 2018, 8:51 PM UTC

sjburt wrote: post #52

vog wrote: post #46

Earlier quoted context omitted.

> the theory that we're actually living in a simulation, ... It's basically Creationism in modern form. It's not even modern. It is basically Plato's Cave, which is classic Greek philosophy. https://en.wikipedia.org/wiki/Allegory_of_the_Cave The religious touch of that idea did not become popular until the movie "The Matrix", which originally had allusions to many different religions, but specialized to Christianity…

That is not the meaning of the Allegory of the Cave at all! The metaphor is that human experience is limited by our senses (like living in the cave) and so to understand eternal, absolute truths you need to use pure reason (leaving the cave), not experience.

Not sure what you argue against, but exactly that aspect, "human experience is limited by our senses", means that everything could be a simulation. Plato named those "shadows", but that's only because people weren't used to good simulation technologies back then. Today we have 3D cinemas, flight simulators, VR headsets, etc.

But if you still don't like that example, here's another historic example of a philosopher who published the idea that everything could be a simulation.

The evil daemon by René Descartes:

https://en.wikipedia.org/wiki/Evil_demon

So my point still stands: The idea that everything might be a simulation is as old as humanity. It is neither modern nor based on creationism.

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#75

Post by d33 » Thu, Mar 22, 2018, 9:29 PM UTC

vanattab wrote: post #24

d33 wrote: post #18

Earlier quoted context omitted.

Actually perhaps it's better that way. Otherwise they could base some superstitious thinking on it that would stick if we were unlucky enough and there'd be yet another case of irrational thinking to be undone.

I have never been able to understand why so many other scientists and "rationalist" look back on humans early "superstitious" ideas with contempt. To my mind these superstitious ideas are the beginning of the rationalist mindset. These ideas are people's attempts to explain and understand how the world works. I am certain that some of the ideas that many of us hold now will be thought quite silly in a few hundred yea…

> I have never been able to understand why so many other scientists and "rationalist" look back on humans early "superstitious" ideas with contempt. To my mind these superstitious ideas are the beginning of the rationalist mindset.

First of all, pstuart nailed it: "I would suggest that any contempt of early superstitious ideas has to do with the fact that many live on today.". Also, one could argue that not all modes of thinking eventually lead to rationalist mindset, at least not directly - one problem with superstitions is that people don't have or need proofs for them and that they as memes fight the same space truth does.

True concept of, for example, evolution still is fighting with creationism because they solve the same problem, but one of them was made completely made up and people still believe in it because it was here earlier. I think it would be better if we had no answers rather than ones that are utterly wrong. Especially since people who make them up and believe based on "faith" alone are so convinced that their concept is true that they actually harm the actual, proven truth.

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#76

Post by c-smile » Thu, Mar 22, 2018, 9:41 PM UTC

vkou wrote: post #63

c-smile wrote: post #50

Again: as sooner we start our resettlement to other star systems - the better.

What about the opportunity cost? What about the long-term? Maybe we should make our ecological footprint steady-state sustainable, first.

Why either one of options? Why not to do that at the same time?

Just take resources from military spendings and put them on both tasks. But right, humans need to learn first how to trust each other...

As one wise gentlemen in Russia once said "большая беда нужна" / "we need a big trouble" for all of us to work on such global task. Is this the only option for creating humanity deserving motivations? Not a star but [relatively] small asteroid on crash course with Earth, are we ready?

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#77

Post by NeoBasilisk » Thu, Mar 22, 2018, 9:58 PM UTC

c-smile wrote: post #76

vkou wrote: post #63

Earlier quoted context omitted.

What about the opportunity cost? What about the long-term? Maybe we should make our ecological footprint steady-state sustainable, first.

Why either one of options? Why not to do that at the same time? Just take resources from military spendings and put them on both tasks. But right, humans need to learn first how to trust each other... As one wise gentlemen in Russia once said "большая беда нужна" / "we need a big trouble" for all of us to work on such global task. Is this the only option for creating humanity deserving motivations? Not a star but [re…

The one event that would unite humanity like no other (even taking advantage of our xenophobia) would be contact with other intelligent life.

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#78

Post by baddox » Thu, Mar 22, 2018, 10:20 PM UTC

dboreham wrote: post #43

rhapsodic wrote: post #34

Earlier quoted context omitted.

> am certain that some of the ideas that many of us hold now will be thought quite silly in a few hundred years. Yes, like the theory that we're actually living in a simulation, espoused by Elon Musk and other respected, ostensibly science-minded people. It's basically Creationism in modern form.

It isn't like creationism because it is based on some otherwise currently unexplained observations such as quantum mechanical behavior and magic physical constants. The idea is that these are exactly the sort of observations you'd see if you were in a simulated universe. Now if we were to observe new species being created in N days, for small integer N, then I suppose your assertion about creationism would also hold.

By definition, aren't all attributes of our Universe exactly what we would expect to see if we were in a simulation of a Universe with those attributes?

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#79

Post by [deleted] » Thu, Mar 22, 2018, 10:35 PM UTC

d33 wrote: post #75

vanattab wrote: post #24

Earlier quoted context omitted.

I have never been able to understand why so many other scientists and "rationalist" look back on humans early "superstitious" ideas with contempt. To my mind these superstitious ideas are the beginning of the rationalist mindset. These ideas are people's attempts to explain and understand how the world works. I am certain that some of the ideas that many of us hold now will be thought quite silly in a few hundred yea…

> I have never been able to understand why so many other scientists and "rationalist" look back on humans early "superstitious" ideas with contempt. To my mind these superstitious ideas are the beginning of the rationalist mindset. First of all, pstuart nailed it: "I would suggest that any contempt of early superstitious ideas has to do with the fact that many live on today.". Also, one could argue that not all modes…

[deleted]

Re: A Visiting Star Jostled Our Solar System 70,000 Years Ago

#80

Post by flukus » Thu, Mar 22, 2018, 11:14 PM UTC

> Around the same time our ancestors left Africa, a dim red dwarf star came to within 0.8 light-years of our Sun

So that's within the Oort cloud. If this happened again should we be more concerned about the star disturbing our Oort cloud or about us travelling through the other stars Oort cloud?