The Astronomy Thread

Dandain · Oct 24, 2016

There has always been a subset of humans driven to explore, anyone who falls in that category is willing to put up with seemingly uncomfortable/undesirable situations for extended periods of time. See ocean exploration voyages, mountaineering, and the poles just to name a few in our modern thought. I just tally it up to differences in the people who would have been explorers and those that would rather just not. Someone has to endure the tedium of exploration before we can go on a pleasure cruise through the galaxy with bowling alleys.

Ukerric · Oct 25, 2016

I think it was an Asimov short story (rewritten to be part of a different novel later) where the crew of the first interstellar ship finally arrives at Alpha Centauri... where the millions of inhabitants on the planet spent the last 5 years preparing for the celebrations of their arrival.

(because a rendez-vous in interstellar space with a ship going even at 1% of the speed of light is damn impossible, so you wait for it to arrive at destination)

Dandain said:
There has always been a subset of humans driven to explore, anyone who falls in that category is willing to put up with seemingly uncomfortable/undesirable situations for extended periods of time. See ocean exploration voyages, mountaineering, and the poles just to name a few in our modern thought. I just tally it up to differences in the people who would have been explorers and those that would rather just not. Someone has to endure the tedium of exploration before we can go on a pleasure cruise through the galaxy with bowling alleys.

Obvious short which has to be linked again

TrollfaceDeux · Oct 25, 2016

Dandain said:
There has always been a subset of humans driven to explore, anyone who falls in that category is willing to put up with seemingly uncomfortable/undesirable situations for extended periods of time. See ocean exploration voyages, mountaineering, and the poles just to name a few in our modern thought. I just tally it up to differences in the people who would have been explorers and those that would rather just not. Someone has to endure the tedium of exploration before we can go on a pleasure cruise through the galaxy with bowling alleys.

a lot of those explorations were driven by commercial interest. If we can exploit space resources to its complete effect, humanity will direct their energy towards that goal. Right now, our planet still hosts enough resources to feed select few and keep the rest content. There is no desire to explore the universe when there are no pursuits available currently by the market.

Speaking of which,

If humanity were to survive the trillion year mark and the universe split so wide and long that everything becomes out of reach until everything fades to darkness, can we still survive--provided that we can create stars at will and control composition of the atom? Create something out of...nothing?

Tuco · Oct 25, 2016

iannis said:
That's both true, but also not an unassailable reason to not bother.

Because if we don't bother you'll probably never get warp3.

What it will take, I think, is to find a habitable planet within the near stellar neighborhood. Raw materials will never be enough. What it will require is something colonizable. Because more and more what we are going to lack isn't material or industry but elbow room.

And we won't find one of those for a few generations. If one even exists.

Agree completely. And when asteroid mining makes the path to a generation ship possible by bringing massive amounts of usable resources to LEO, I'll be super happy that we're building a generational ship. Even if there's a 90% chance that we'll beat it to its destination, it's worth doing on the off chance that humanity plunges into another dark age, gets blown up by a meteor etc.

Abefroman · Oct 25, 2016

I think the one thing that is overlooked when it comes to long term space travel and colonizing another planet, especially one already having life is nano technology. We are going to need something to combat new bacteria and viruses and to keep people healthy on long generational voyages. Our drugs will only take us so far until tiny machines will be needed and when that happens colonizing will really be needed due to lifespans going through the roof.

Cad · Oct 25, 2016

Tuco said:
Agree completely. And when asteroid mining makes the path to a generation ship possible by bringing massive amounts of usable resources to LEO, I'll be super happy that we're building a generational ship. Even if there's a 90% chance that we'll beat it to its destination, it's worth doing on the off chance that humanity plunges into another dark age, gets blown up by a meteor etc.

To me the generation ship can't work with our current propulsion tech, and won't be necessary with almost any kind of electric zero-propellant propulsion tech. So it's an in-between type of sci-fi thing that won't ever really be practical.

Tuco · Oct 25, 2016

Cad said:
To me the generation ship can't work with our current propulsion tech, and won't be necessary with almost any kind of electric zero-propellant propulsion tech. So it's an in-between type of sci-fi thing that won't ever really be practical.

Not sure why you'd say that. It's reasonable to assume that a future propellentless drive using physics we don't think is possible would have limits in the form of heat generation or power draw. I'd say that being able to accelerate a ship at 0.1m/s would be pretty impressive for one of these drives.

Let's say we make a trip to Gliese 667 Cc, which is a mere 23 light years or 217 trillion KM away.

A space vehicle would spend the first half of the trip accelerating in one direction, then the second half accelerating in the other direction (or decelerating). Let's assume that the drive is pretty amazing and can generate 1G of thrust, in order to traverse 108.5 trillion KM (halfway), it will take t = sqrt(2 * d / a) or t = 1473091986s = 17049d = 46.7 years. Which means the full trip would be nearly 100 years.

Now, we could cut down on that by slingshotting the spaceship around jupiter first, but any way you cut it having a 0.1m/s drive is going to be slow going. If we start talking 1m/s or even 10m/s drives, it's a different ball game, but even if we could instantly accelerate to light speed, that planet that's 23 light years away is going to take 23 years to get to. And that's one of the closest potential planets. What if we find one that's 100 light years away?

Oh and at that acceleration you'll be going at half the speed of light at the fastest, it could be there's some barriers or limitations that relate to material moving at the speed of light in any reference frame, dunno, I'm not a theoretical physicist.

Cad · Oct 25, 2016

Tuco said:
Not sure why you'd say that. It's reasonable to assume that a future propellentless drive using physics we don't think is possible would have limits in the form of heat generation or power draw. I'd say that being able to accelerate a ship at 0.1m/s would be pretty impressive for one of these drives.

Let's say we make a trip to Gliese 667 Cc, which is a mere 23 light years or 217 trillion KM away.

A space vehicle would spend the first half of the trip accelerating in one direction, then the second half accelerating in the other direction (or decelerating). Let's assume that the drive is pretty amazing and can generate 1G of thrust, in order to traverse 108.5 trillion KM (halfway), it will take t = sqrt(2 * d / a) or t = 1473091986s = 17049d = 46.7 years. Which means the full trip would be nearly 100 years.

Now, we could cut down on that by slingshotting the spaceship around jupiter first, but any way you cut it having a 0.1m/s drive is going to be slow going. If we start talking 1m/s or even 10m/s drives, it's a different ball game, but even if we could instantly accelerate to light speed, that planet that's 23 light years away is going to take 23 years to get to. And that's one of the closest potential planets. What if we find one that's 100 light years away?

Oh and at that acceleration you'll be going at half the speed of light at the fastest, it could be there's some barriers or limitations that relate to material moving at the speed of light in any reference frame, dunno, I'm not a theoretical physicist.

According to this: Space travel calculator

With 1G of acceleration a 23 light year journey would take 6.4 apparent years.

With .1 m/s^2 it would take 92 years. With even 1 m/s^2 it would only take 27 apparent years and hit .89c.

With 1m/s^2 even a trip of 1000 light years would only take 87 apparent years. This is all assuming that you can actually approach the speed of light and take advantage of time dialation; as you point out there might be problems with that that we haven't seen yet.

Valishar · Oct 25, 2016

Well the problem is fuel.

For a 1g spaceship on a trip where you decelerate to arrive there, using 100% efficient matter/antimatter reactions. This is the cost in fuel per Kg of payload.

4.3 ly
Nearest star
38 kg

27 ly
Vega
886 kg

30,000 ly
Centre of our galaxy
955,000 tonnes

2,000,000 ly
Andromeda Galaxy.
4.2 thousand million tonnes

The Relativistic Rocket

Kharzette · Oct 25, 2016

I wonder what the math would be like for a small lithium reactor powering big arrays of 1 newton per KW EM propulsion units. Like how many reactors you'd need and how much mass for the drives and wires, and loss to heat and such.

Cad · Oct 25, 2016

Valishar said:
Well the problem is fuel.

For a 1g spaceship on a trip where you decelerate to arrive there, using 100% efficient matter/antimatter reactions. This is the cost in fuel per Kg of payload.

4.3 ly
Nearest star
38 kg

27 ly
Vega
886 kg

30,000 ly
Centre of our galaxy
955,000 tonnes

2,000,000 ly
Andromeda Galaxy.
4.2 thousand million tonnes

The Relativistic Rocket

At some point you'd hit diminishing returns on crowding c closer and closer and stop accelerating, right? For the 2 million ly journey no way you need to burn the whole time. Your gamma would be insane.

Scoresby · Oct 25, 2016

Cad said:
At some point you'd hit diminishing returns on crowding c closer and closer and stop accelerating, right? For the 2 million ly journey no way you need to burn the whole time. Your gamma would be insane.

Exactly, it would only take a bit over 58 years to hit the Speed of Light if it tracked a linear path. However, as mass increases asymptotically as you approach c, the energy requirements on the top end get ridiculous. Realistically, you'd accelerate / decelerate for ~50 years and the rest would just be time spent floating along in the void.

Valishar · Oct 25, 2016

Sure, but even the low end of 38kg of antimatter per kg of weight for the spaceship, is insane.

Scoresby · Oct 25, 2016

Valishar said:
Sure, but even the low end of 38kg of antimatter per kg of weight for the spaceship, is insane.

1kg of antimatter is insane. We have no way to produce anywhere near bulk quantities. Just goes to highlight how truly extreme interstellar travel is.

As big of a nay-sayer as I may seem, I am not against the idea that there is some FTL travel out there. Now the small task of finding out how it all works (and extend our understanding of the universe significantly in the process).

Cad · Oct 25, 2016

Scoresby said:
Exactly, it would only take a bit over 58 years to hit the Speed of Light if it tracked a linear path. However, as mass increases asymptotically as you approach c, the energy requirements on the top end get ridiculous. Realistically, you'd accelerate / decelerate for ~50 years and the rest would just be time spent floating along in the void.

Floating along in the void with some kind of gigantic magnetic shield I hope otherwise the first dust particle would cleave you in two at .9999c

meStevo · Oct 26, 2016

Saturn's polar hexagon changed color.

Scientists are investigating potential causes for the change in color of the region inside the north-polar hexagon on Saturn. The color change is thought to be an effect of Saturn's seasons. In particular, the change from a bluish color to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017.

Researchers think the hexagon, which is a six-sided jetstream, might act as a barrier that prevents haze particles produced outside it from entering. During the polar winter night between November 1995 and August 2009, Saturn's north polar atmosphere became clear of aerosols produced by photochemical reactions -- reactions involving sunlight and the atmosphere. Since the planet experienced equinox in August 2009, the polar atmosphere has been basking in continuous sunshine, and aerosols are being produced inside of the hexagon, around the north pole, making the polar atmosphere appear hazy today.

Other effects, including changes in atmospheric circulation, could also be playing a role. Scientists think seasonally shifting patterns of solar heating probably influence the winds in the polar regions.

Changing Colors in Saturn's North

pharmakos · Oct 26, 2016

I feel like this is that blue dress / gold dress thing from last year

Tuco · Oct 26, 2016

The takeaway for me is that even with an incredibly impressive propellentless drive we're still very, very far from the stars. We'll need a few massive technological breakthroughs beyond that to reach the stars without a generation ship.

Cad · Oct 26, 2016

Tuco said:
The takeaway for me is that even with an incredibly impressive propellentless drive we're still very, very far from the stars. We'll need a few massive technological breakthroughs beyond that to reach the stars without a generation ship.

For sure thats true but the propellant-less drive is one of the required steps. Can't do without it.

ZyyzYzzy · Oct 26, 2016

Abefroman said:
I think the one thing that is overlooked when it comes to long term space travel and colonizing another planet, especially one already having life is nano technology. We are going to need something to combat new bacteria and viruses and to keep people healthy on long generational voyages. Our drugs will only take us so far until tiny machines will be needed and when that happens colonizing will really be needed due to lifespans going through the roof.

Well there's a good chance that any life we encounter will be incapable of even bnding to and disrupting any cellular processes. This is unless, due to the fundemntal laws of the universe cellular chemistry has evolved similarly elsewhere due just to the constraints imposed by these universal laws or the other life is not carbon based and completely toxic to our carbon based cellular life.

The Astronomy Thread

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