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Old 7th November 2018, 02:44 PM   #1
Wolrab
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Did an Alien Light Sail Visit The Solar System?

Interesting. I'm a bit confused how an object can accelerate like this one is described to.
https://spaceweatherarchive.com/2018...-solar-system/
Here's the paper. It must be bogus because there are all these numbers, letters, and sqiggles but no link to youtube videos.
https://arxiv.org/pdf/1810.11490.pdf
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Old 7th November 2018, 02:47 PM   #2
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Betteridge.
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Old 7th November 2018, 02:50 PM   #3
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Old 7th November 2018, 02:51 PM   #4
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It would be quite the coincidence if the first interstellar object observed in our solar system was from ETs.
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Old 7th November 2018, 03:13 PM   #5
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Outsiders.
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Old 7th November 2018, 03:52 PM   #6
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The guy who "chairs the advisory board for the Breakthrough Starshot light sail project" thinks it might be a light sail, eh?
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Old 7th November 2018, 04:04 PM   #7
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Wow! Another weird coincidence!
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Old 7th November 2018, 04:13 PM   #8
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Nice article by The Bad Astronomer - Dr. Phil Plait.
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Old 7th November 2018, 04:20 PM   #9
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Originally Posted by Wolrab View Post
It would be quite the coincidence if the first interstellar object observed in our solar system was from ETs.
And looked eerily like Rama.
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Old 7th November 2018, 04:22 PM   #10
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Originally Posted by alfaniner View Post
Quote:
traveling through the galaxy for thousands of years at least
Do you think he meant billions? Or at least millions.
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Old 7th November 2018, 04:43 PM   #11
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Just imagine in a billion years a Tesla will pass through a solar system and they’ll wonder if it was an alien probe!
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Old 7th November 2018, 04:50 PM   #12
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Originally Posted by MikeG View Post
Betteridge.
OK.

Did an Alien Light Sail Not Visit The Solar System?
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Old 7th November 2018, 04:51 PM   #13
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Originally Posted by alfaniner View Post

Phil makes two points about the behavior of the object that are worth considering.

First, he points to the estimate of 50m for the size of the object. He then asks why so small if it was a light sail, since bigger is better. I think Phil fails to consider the perspective from which he approaches that critique. He is accustomed to the scale of things based on the technology created by humans. Would technologically advanced ant sized aliens necessarily build on the same scale as we do?

Second, he questions the speed of only 25 kps for the object. If it was a light sail made for interstellar travel, why so slow? Faster is better, after all. If that was universally true then shouldn't the cars on the highway be travelling at 500 mph? Why don't they? Because we have laws we must obey. Therefore, for these aliens, 25 kps is obviously their legal speed limit.


So there you go, Phil's main concerns have all been neatly hand waved away.

Therefore Aliens!

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Old 7th November 2018, 05:02 PM   #14
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There are certain physical laws that even alien technology must adhere to. One of them is that more photons hitting an object will exert more force on it. A bigger light sail will be more efficient and effective than a small one, and make it go faster. No amount of alien technology will change that.
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Old 7th November 2018, 05:14 PM   #15
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Originally Posted by arthwollipot View Post
There are certain physical laws that even alien technology must adhere to. One of them is that more photons hitting an object will exert more force on it. A bigger light sail will be more efficient and effective than a small one, and make it go faster. No amount of alien technology will change that.
You are assuming it is a complete light sail. How about just a small fraction of one that was turn off for some reason. Then it would behave the way it does.
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Old 7th November 2018, 05:15 PM   #16
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I don't know, the way it tumbles I was thinking artificial gravity from the beginning. But I just dismissed that thought as silly wishful thinking. Then it started accelerating away without changing its rotational speed. That's pretty much means it has some sort of drive different than just outgassing randomly.

I honestly can't even conceive of a natural explanation for that. But solar sail doesn't seem likely either. So what could it be?
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Old 7th November 2018, 05:19 PM   #17
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Originally Posted by rjh01 View Post
You are assuming it is a complete light sail. How about just a small fraction of one that was turn off for some reason. Then it would behave the way it does.
It could be a part of one that was destroyed by a collision. That's a good thought.

But, y'know, it's probably just a rock.
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Old 7th November 2018, 05:34 PM   #18
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Phil ain't got nothing without a youtube video. All real science needs a youtube video....and large colored fonts.
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Old 7th November 2018, 05:48 PM   #19
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Originally Posted by arthwollipot View Post
There are certain physical laws that even alien technology must adhere to. One of them is that more photons hitting an object will exert more force on it. A bigger light sail will be more efficient and effective than a small one, and make it go faster. No amount of alien technology will change that.
What if it was using a Galaxy Cluster and Gravytational Lensing to focus more light on its tiny sail - allowing speeds up to the Kessel Run in less than 12 parsecs?
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Old 7th November 2018, 06:06 PM   #20
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Originally Posted by Elagabalus View Post
What if it was using a Galaxy Cluster and Gravytational Lensing to focus more light on its tiny sail - allowing speeds up to the Kessel Run in less than 12 parsecs?
A parsec is a measure of distance, not speed, as explained in the recent documentary Solo.
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Old 7th November 2018, 06:23 PM   #21
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Originally Posted by arthwollipot View Post
There are certain physical laws that even alien technology must adhere to. One of them is that more photons hitting an object will exert more force on it. A bigger light sail will be more efficient and effective than a small one, and make it go faster. No amount of alien technology will change that.
If the object is a probe, as suggested by the original paper, very high speed while passing through our solar system would limit the amount of observation time. Going less than, as fast as possible, would be beneficial.
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Old 7th November 2018, 06:59 PM   #22
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It could be a message of peace. Nothing more and nothing less. They want us to be nice. Pancake rock says be nice to everybody.
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Old 7th November 2018, 07:07 PM   #23
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Originally Posted by Molinaro View Post
If the object is a probe, as suggested by the original paper, very high speed while passing through our solar system would limit the amount of observation time. Going less than, as fast as possible, would be beneficial.
Sure, if you were okay with it taking hundreds of thousands of years to get to its destination.
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Old 7th November 2018, 07:49 PM   #24
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Wait, what? You take 'er up to the Kessel Run in less than 12 parsecs and then when you get to the Solar System ya' cut 'er down to impulse power.
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Old 7th November 2018, 07:52 PM   #25
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Originally Posted by Molinaro View Post
If the object is a probe, as suggested by the original paper, very high speed while passing through our solar system would limit the amount of observation time. Going less than, as fast as possible, would be beneficial.
True, but even there, greater acceleration is still desirable.
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Old 8th November 2018, 12:15 AM   #26
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Originally Posted by arthwollipot View Post
A parsec is a measure of distance, not speed, as explained in the recent documentary Solo.
That doesn't mean that Elagabalus' post had an error. It's the equivalent of saying "Hamilton's car accelerated to 180mph in the back straight", or "Usain Bolt was at full speed before the 25 metre mark".

However, this is wrong:

Originally Posted by Elagabalus View Post
Wait, what? You take 'er up to the Kessel Run in less than 12 parsecs and then when you get to the Solar System ya' cut 'er down to impulse power.
..........albeit it is more a quote than an original error.
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Old 8th November 2018, 12:18 AM   #27
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nonsense.

It's not a Solar Sail, it is the booster stage of a much larger ship decelerating before entering the Solar System.
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Old 8th November 2018, 06:27 AM   #28
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Originally Posted by The Great Zaganza View Post
nonsense.

It's not a Solar Sail, it is the booster stage of a much larger ship decelerating before entering the Solar System.
Interesting idea, except you donít make booster stages much smaller than the craft youíre boosting, the overhead for stage separation makes that pointless.
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Old 8th November 2018, 06:52 AM   #29
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Originally Posted by Ziggurat View Post
Interesting idea, except you donít make booster stages much smaller than the craft youíre boosting, the overhead for stage separation makes that pointless.
But the booster stages are mostly fuel tanks. This could just be the engine after it had already exhausted the fuel that it carried as a cryogenic ball of ices.
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Old 8th November 2018, 07:06 AM   #30
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NVM
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Old 8th November 2018, 07:07 AM   #31
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Originally Posted by Garrison View Post
Well it wouldn't be the first:

Oumuamua
that is the one we are talking about.
from the wiki:

Quote:
In November 2018, astronomers from Harvard University submitted a paper exploring the possibility of ʻOumuamua being an artificial thin solar sail accelerated by solar radiation pressure in an effort to help explain the object's non-gravitational acceleration.[19][20][21] Other scientists have stated that the available evidence is insufficient to draw such a conclusion.[80]
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Old 8th November 2018, 09:23 AM   #32
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It was an alien probe. It picked up a broadcast of a Trump rally, analyzed it, concluded there was no intelligent life in this system, got the hell out and headed for the next system.
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Old 8th November 2018, 09:28 AM   #33
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Originally Posted by Molinaro View Post
Phil makes two points about the behavior of the object that are worth considering.

First, he points to the estimate of 50m for the size of the object. He then asks why so small if it was a light sail, since bigger is better. I think Phil fails to consider the perspective from which he approaches that critique. He is accustomed to the scale of things based on the technology created by humans. Would technologically advanced ant sized aliens necessarily build on the same scale as we do?

Hell, even we don't have to build it on that scale.

https://en.wikipedia.org/wiki/Breakt...shot#Lightsail

Quote:
The lightsail is envisioned to be no larger than 4 by 4 meters (13 by 13 feet),
You'll of course note that this is the group the author is associated with.

This is based off the "Starwisp" concept for a microprobe to be sent to another star system. Such a probe wouldn't be as cool as an actual "ship", but it's actually more realistic to expect a probe like this. So a 50 meter size is totally reasonable.


Quote:
Second, he questions the speed of only 25 kps for the object. If it was a light sail made for interstellar travel, why so slow?

My problem here is that he assumes they also won't slow down. If you're probing a star system, just blazing through it at interstellar speeds is probably less than optimal. If you've got an autonomous space probe that used a solar sail to get up to speed, there's no reason it couldn't also use it to slow down for the fly past. Even at thousands of kps, you're looking at incredibly long mission times, so adding a few years by slowing down for the fly past probably isn't a deal breaker. The only reason we don't do this for our missions like Voyager is that we're still relying on rockets. A light sail makes this kind of slower fly-by mission possible, and maybe even practical.
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Old 8th November 2018, 09:29 AM   #34
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Originally Posted by CORed View Post
It was an alien probe. It picked up a broadcast of a Trump rally, analyzed it, concluded there was no intelligent life in this system, got the hell out and headed for the next system.
Or it realized it would be an illegal alien, feared the possibility of incarceration, and fled.

Trump's plan is working!
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Old 8th November 2018, 09:34 AM   #35
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Originally Posted by Molinaro View Post
First, he points to the estimate of 50m for the size of the object. He then asks why so small if it was a light sail, since bigger is better. I think Phil fails to consider the perspective from which he approaches that critique. He is accustomed to the scale of things based on the technology created by humans. Would technologically advanced ant sized aliens necessarily build on the same scale as we do?
I haven't read all the links yet but do they mean this object >is< a light sail? Or do they mean it was once attached to a light sail? 50M is fine for two of the dimensions of a light sail. But if it's also that thick it's not going to be a sail.

Has someone mentioned this already? Seems kind of obvious.
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Old 8th November 2018, 10:34 AM   #36
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Originally Posted by RecoveringYuppy View Post
I haven't read all the links yet but do they mean this object >is< a light sail? Or do they mean it was once attached to a light sail? 50M is fine for two of the dimensions of a light sail. But if it's also that thick it's not going to be a sail.

Has someone mentioned this already? Seems kind of obvious.
The paper suggests a thickness of 0.9 to 0.3 mm.
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Old 8th November 2018, 11:12 AM   #37
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Originally Posted by Molinaro View Post
The paper suggests a thickness of 0.9 to 0.3 mm.
Yeah, I saw that but initially thought that such a thing was precluded by our observations. Turns out it isn't. It's consistent with our observations, but so are a lot of other other dimensions.
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Old 8th November 2018, 11:17 AM   #38
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Originally Posted by RecoveringYuppy View Post
I haven't read all the links yet but do they mean this object >is< a light sail?
They're suggesting that it could be a light sail.

Here's the issue, in brief. Some force other than gravity is acting on it, a force which has a 1/r2 dependence. Solar influx has a 1/r2 dependence, so this is a likely candidate. Solar influx can produce a pressure in two different ways:

1) Heating from solar influx can produce outgassing from the object. This happens quite dramatically and visibly with comets. Oumuamua might be outgassing, but if so, it's not doing it like comets do.

2) Solar influx can directly produce radiation pressure on the object. This pressure is quite small, and in order to produce the observed acceleration, the object would have to be VERY light. A solar sail could be that light.
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law
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Old 8th November 2018, 11:46 AM   #39
Elagabalus
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The solar sail is actually a drag chute capturing the flow of the Dark in order to slow down to impulse power.
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Old 8th November 2018, 11:53 AM   #40
Hellbound
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Location: Not in Hell, but I can see it from here on a clear day...
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Originally Posted by Elagabalus View Post
The solar sail is actually a drag chute capturing the flow of the Dark in order to slow down to impulse power.
*Hellbound pulls out a rolled up newspaper*

Bad Elagablus! Bad!
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