Astronomers substitute "lots and lots of similar objects at different stages of evolution" for time. Most of the timescales involved are longer than the time humans have existed on Earth and much longer than civilization.
AFAIK, not directly. The only way possible would be to observe one behind a gravitational lens. That would appear as multiple sources, allowing us to observe the object from slightly different directions, confirming that the flashes are indeed at least cone-shaped.
The thing with these is that they have to be very directional to even reach us, and (in the article), it mentions the bursts have the energy of a century of our sun's output; if it is alien networking gear, they'd have to be able to generate that power somehow. Dyson spheres wouldn't cut it.
Could it be, hypothetically, that there are so many layers in the swarm that the radiation that will get eventually be emitted is outside of what we can detect?
No, given that we can map the dark matter density in galaxies - having a bunch of dark matter galaxies wouldn't explain the shapes of what we actually observe.
Thermodynamics doesn't require isotropic radiation. If you're going to shed a lot of waste heat, why not aim it out of the galactic plane, so as to avoid calling unnecessary attention to yourself?
No. One of the issues with current understanding of galaxies is that our understanding of gravity does not fit the rotation of the galaxies we are observing. To explain this, and other effects, we use dark matter.
There was a theory that the reason for the discrepancy is that our understanding of gravity is wrong, and that it is in fact a calculation error on galactic scales. The problem with this is that apparently there are galaxies which seem to have very little dark matter and are much closer to expected behavior than other galaxies. So we are left with the dark matter explanation so far.
The flashlight fits Occam's Razor much more neatly. A pulsing lamp that goes from nothing to nova intensity with a nice neat period requires a lot more assumptions.
Something highly directional is much more likely to be something intelligently-designed, so the razor cuts both ways here. Not trying to argue btw, genuinely just discussing.
Not necessarily, we already have a lot of natural directional phenomena, like pulsars in particular. The really strange thing about this is the long period.
What if it's something simple like a galactic lighthouse of sorts? Not sure why I'm being downvoted. Lighthouses use directional light and if you're stationary you'll see the light at certain increments of time. An advanced race might be saying "don't go here" or "be careful." Just like we do for ships here.
There are lots of naturally occurring ones such as pulsars, enough to the point they could be used for 3D navigation, if you can find your distance to them.
It's an old idea: Pioneer and later spacecraft have a plaque showing our location relative to distances to pulsars we can see from Earth.
edit: I guess if you're a Type 3 civilization with nothing better to do, you wouldn't have to set up lighthouses but you could better direct your attention to moving galaxies around or whatever.
> There are lots of naturally occurring ones such as pulsars, enough to the point they could be used for 3D navigation, if you can find your distance to them.
There's work towards this, from the X-ray emission of pulsars[0]. I don't think you'd need a precise distance to the pulsars to measure your own position, as long as you're measuring your own position relative to some other object (e.g., Solar System barycenter). If it's a relative measurement then you should be able to determine that by comparing the time-of-arrival (TOA) of the pulsed emission from multiple pulsars with the TOAs at Earth.
And pulsars spin rates slowly change over time do to energy losses.
But I don't think these things would cripple a pulsar-based navigation system. Presumably any network of pulsars used for this purpose would be regularly monitored and timing solutions would be updated regularly. The updated timing solutions could be transmitted as-needed.
At any rate, a robust navigation network of pulsars would need a sufficient number of sources to guard against glitches breaking the navigation system.
Also, in context of an alien civilization finding our XX century probes a million years from now, I think they could reconstruct the location anyway - I'd assume there would be only one combination of pulsars you could pattern-match to what's on Voyager plaques, even if each of them shifted in frequency a bit.
The idea that aliens would use these to propel ships is rather ludicrous, and highly unlikely. The nearest galaxy is 25k light years away so even at the maximum speed it would take 25 thousand years to travel here.
That being said, it must be something exceptionally energetic.. wish I could see it.
> The nearest galaxy is 25k light years away so even at the maximum speed it would take 25 thousand years to travel here.
Given your arithmetic, I assume by "maximum speed" you mean the speed of light, in which case travel wouldn't take 25k years. It would in fact be instantaneous. At relativistic speeds, distances contract and time dilates.
Now, this is all moot because this:
> The idea that aliens would use these to propel ships is rather ludicrous, and highly unlikely.
... is absolutely correct. No amount of energy will propel a massive object to the speed of light.
edit: I realized I may have misinterpreted. From the perspective of someone watching their own kind travel that expanse, it would indeed appear to the outside observer to take 25k years to travel.
Plus reaching the speed of light requires infinite energy, literally. You have to settle on some small fraction of the speed of light, depending on how much mass and energy you have.
It's pointless to travel at speed of light to get instantaneous travel when you spend half an hour boarding rocket and 2h in traffic from the city to starport.
As long as we're being pedantic, the trip is only instantaneous if you're able to instantly accelerate to c. Otherwise, it would take around two years for the occupant (one year to accelerate to c upon departure and another to decelerate on arrival), assuming acceleration at 1G.
Ahem. To add yet more pedantry, one year of acceleration at 1G doesn't get you to c, but only fairly close. (I worked that problem nearly 40 years ago, so my memory of "how close" is a bit obscure.)
Why do you assume they need to travel between galaxies? They could be going to the next solar system over and we're simply seeing the leakage of their propulsion. Just because the light travels across galaxies doesn't mean it's purpose is to travel across galaxies. Moreover, a species that can unleash this much energy has probably conquered such things as mortality and age related decay.
you also assume they're traveling AT or NEAR light speed, they could be traveling many times that OR not traveling via speed at all, but warping space and literally folding it over on itself and going THROUGH space like basically creating a controlled wormhole.
the suggestion is that they would be gathering the waves in a light sails. Also you can't travel faster than light, end of story. Warping space or traveling through "wormholes" is not faster than light travel.
Oh man, I don't want to get into an argument on HN. But you didn't really read the previous comment with a generous eye. The poster never mentioned "faster than light" travel at all. In fact, they specifically called out AT or NEAR light speed, and then gave wormhole travel as an example of "not traveling via speed".
gremlinsinc literally said "they could be traveling many times that" in respect to "AT or NEAR light speed." As in they could be traveling many time faster than light. He didn't use the exact phrase "faster than light" but his meaning is pretty clear.
Transportation technically is faster than the speed of light, because if travelling at the speed of light you get to point B in 5 years, and by using a warp drive/worm hole device you get their in 3 days, you've traveled faster than light, doesn't matter if you cheated using physics, you still got their in a fraction of the time. Sure you're 'speed limit' didn't exceed the speed of light, but the distance/normal travel time DID exceed the speed of light, so it's just semantics.
I think it's extremely unlikely to be aliens, since each time in the past something like this has come up a non-aliens explanation has been found.
That said, I don't think distances/timescales is a great argument against aliens, since it makes a lot of assumptions. They could use robotic ships, or generation ships (no telling how long their generations might last.) If they're moving at a significant fraction of the speed of light, relativistic effects could be dramatically reducing their perceived mission duration. Maybe the biology of their species is such that cloning or suspended animation is straight forward.
>> The nearest galaxy is 25k light years away so even at the maximum speed it would take 25 thousand years to travel here.
We're talking about aliens, right? Who says they must have human life spans? Perhaps a 25k year trek is a walk in the park for them.
I find this assumption (that life on other planets will have the same duration as life on Earth) very often in discussions of possible discovery of or interaction with alien civilisations. It is a huge assumption, on par with assuming that aliens must have a head, two hands and two feet and communicate by making sounds, like we do.
Accordingly, the fact that we are limited in our ability to travel from star to star because of short duration of our life spans relative to the speed of light, is not to be taken for granted as a universal characteristic of all life in the universe.
Here is an index of different theories that astrophysics departments have developed to explain these FRBs (Fast Radio Bursts): https://frbtheorycat.org/index.php/Main_Page. There are links to all of the corresponding papers as well.
> Researchers monitored the known repeater FRB 121102 with the Lovell Telescope, a 250-foot-wide (76 meters) radio dish at Jodrell Bank Observatory in England, over the course of five years. They found strong indications of a 157-day activity cycle; 121102 seems to flare up for 90 days and then go silent for 67, the team reported in a new study.
> It's unclear what's behind such cyclic activity, though scientists do have a few ideas. For example, periodic flare-ups could be caused by a wobble in the rotational axis of a highly magnetized neutron star known as a magnetar. Or they could be linked to the orbital motions of a neutron star in a binary system.
Could this be the Dzhanibekov Effect ? Funny I just stumbled upon it today!
If Earth can maintain a stable axis, such wobbly oscillating axis could be that star's "normal". Just guessing! Or may be am too wrong. I am not a physicist!
"They found strong indications of a 157-day activity cycle; 121102 seems to flare up for 90 days and then go silent for 67, the team reported in a new study."
Maybe there's nothing to it, but both 157 and 67 are primes.
They may be primes, but they are primes of an Earth day, which, as far as I am aware, is the only place where those numbers would be 157 & 67.
As an example, our day on Earth is roughly 1440 minutes, while on Mars it is 1477 minutes. So on Mars it would be 153 & 65 day intervals.
I deliberately chose the closest comparison to Earth. Had I chosen any other planet in our solar system, the numbers would have been much, much more different (on Jupiter it would be 406 & 173 days, respectively).
A "day" has no meaning anywhere but on Earth. So if you are going to make the leap that the usage of primes is a sign of intelligence, you would also have to believe that this message was meant for us and only us. However the burst seems to originate from 3 billion light-years away so they would have had to start sending the message very shortly after life began on the Earth. Seems incredibly unlikely.
EDIT: Also an Earth day is not a constant value. It would have been much shorter 3 billion years ago and this cycle wouldn't be repeating in prime numbers. This theoretical alien intelligence would therefore need to not only be able to recognize life on Earth in the first few hundred million years it existed. It would also need to be able to accurately model the Earths orbit over the next 3 billion years in order to customize the message for when it would be received. All that work to send the message and they still needed to luck out that the 3 billion year journey happened to reach us at nearly the perfect time for our technology to advance enough so we could hear it.
It wouldn't have to do any of that if it was simply keeping an activity:non-activity ratio that resulted in 2 primes. I'm not sure to what degree of precision this flashing is happening but if it's very precise then there you go. 2 primes result no matter what your day/timescale/number system is.
Also they would have had to infer our day cycle from observations originated 6 billion years ago, which would be strange because the age of the solar system is estimated to be 4.5b years.
90 comments
[ 4.2 ms ] story [ 159 ms ] thread"At its equator it is spinning at approximately 24% of the speed of light, or over 70,000 km per second."
https://en.wikipedia.org/wiki/PSR_J1748%E2%88%922446ad
Magnetars, even more so - and can have a measurable effect on the Earth's atmosphere:
https://slate.com/technology/2012/12/cosmic-blast-magnetar-e...
https://en.wikipedia.org/wiki/SGR_1806%E2%88%9220
Edit: clarified
There was a theory that the reason for the discrepancy is that our understanding of gravity is wrong, and that it is in fact a calculation error on galactic scales. The problem with this is that apparently there are galaxies which seem to have very little dark matter and are much closer to expected behavior than other galaxies. So we are left with the dark matter explanation so far.
It's an old idea: Pioneer and later spacecraft have a plaque showing our location relative to distances to pulsars we can see from Earth.
https://en.wikipedia.org/wiki/Pulsar
https://en.wikipedia.org/wiki/Pulsar#/media/File:Pioneer_pla...
edit: I guess if you're a Type 3 civilization with nothing better to do, you wouldn't have to set up lighthouses but you could better direct your attention to moving galaxies around or whatever.
There's work towards this, from the X-ray emission of pulsars[0]. I don't think you'd need a precise distance to the pulsars to measure your own position, as long as you're measuring your own position relative to some other object (e.g., Solar System barycenter). If it's a relative measurement then you should be able to determine that by comparing the time-of-arrival (TOA) of the pulsed emission from multiple pulsars with the TOAs at Earth.
[0] https://en.wikipedia.org/wiki/X-ray_pulsar-based_navigation
I'd worry about pulse identification over any significant period of time.
But I don't think these things would cripple a pulsar-based navigation system. Presumably any network of pulsars used for this purpose would be regularly monitored and timing solutions would be updated regularly. The updated timing solutions could be transmitted as-needed.
At any rate, a robust navigation network of pulsars would need a sufficient number of sources to guard against glitches breaking the navigation system.
That being said, it must be something exceptionally energetic.. wish I could see it.
Given your arithmetic, I assume by "maximum speed" you mean the speed of light, in which case travel wouldn't take 25k years. It would in fact be instantaneous. At relativistic speeds, distances contract and time dilates.
Now, this is all moot because this:
> The idea that aliens would use these to propel ships is rather ludicrous, and highly unlikely.
... is absolutely correct. No amount of energy will propel a massive object to the speed of light.
edit: I realized I may have misinterpreted. From the perspective of someone watching their own kind travel that expanse, it would indeed appear to the outside observer to take 25k years to travel.
https://www.space.com/35996-fast-radio-bursts-powering-alien...
the suggestion is that they would be gathering the waves in a light sails. Also you can't travel faster than light, end of story. Warping space or traveling through "wormholes" is not faster than light travel.
That said, I don't think distances/timescales is a great argument against aliens, since it makes a lot of assumptions. They could use robotic ships, or generation ships (no telling how long their generations might last.) If they're moving at a significant fraction of the speed of light, relativistic effects could be dramatically reducing their perceived mission duration. Maybe the biology of their species is such that cloning or suspended animation is straight forward.
We're talking about aliens, right? Who says they must have human life spans? Perhaps a 25k year trek is a walk in the park for them.
I find this assumption (that life on other planets will have the same duration as life on Earth) very often in discussions of possible discovery of or interaction with alien civilisations. It is a huge assumption, on par with assuming that aliens must have a head, two hands and two feet and communicate by making sounds, like we do.
Accordingly, the fact that we are limited in our ability to travel from star to star because of short duration of our life spans relative to the speed of light, is not to be taken for granted as a universal characteristic of all life in the universe.
https://ui.adsabs.harvard.edu/abs/2017ApJ...837L..23L/abstra...
> It's unclear what's behind such cyclic activity, though scientists do have a few ideas. For example, periodic flare-ups could be caused by a wobble in the rotational axis of a highly magnetized neutron star known as a magnetar. Or they could be linked to the orbital motions of a neutron star in a binary system.
Could this be the Dzhanibekov Effect ? Funny I just stumbled upon it today!
https://www.youtube.com/watch?v=1VPfZ_XzisU
If Earth can maintain a stable axis, such wobbly oscillating axis could be that star's "normal". Just guessing! Or may be am too wrong. I am not a physicist!
Man, don't be too modest. With these few lines I'd be tempted to award you a Nobel prize if I were the judge :)
(exaggerating a bit, but more seriously: you seem to have your chops in this department).
Maybe there's nothing to it, but both 157 and 67 are primes.
As an example, our day on Earth is roughly 1440 minutes, while on Mars it is 1477 minutes. So on Mars it would be 153 & 65 day intervals.
I deliberately chose the closest comparison to Earth. Had I chosen any other planet in our solar system, the numbers would have been much, much more different (on Jupiter it would be 406 & 173 days, respectively).
EDIT: Also an Earth day is not a constant value. It would have been much shorter 3 billion years ago and this cycle wouldn't be repeating in prime numbers. This theoretical alien intelligence would therefore need to not only be able to recognize life on Earth in the first few hundred million years it existed. It would also need to be able to accurately model the Earths orbit over the next 3 billion years in order to customize the message for when it would be received. All that work to send the message and they still needed to luck out that the 3 billion year journey happened to reach us at nearly the perfect time for our technology to advance enough so we could hear it.
https://arxiv.org/pdf/2003.03596.pdf