This would better explain some evidence that the K-T boundary wasn’t a sharp line of demarcation, but an extended event.
One has to wonder whether we’re being too restrictive in our thinking about the source of extraterrestrial bombardment. Our own solar system is full of objects in orbits whose eccentricity ranges from 0 to 0.9999… Given the right gravitational encounter with one of the planets, an object with e = 0.9999 could easily just leave the solar system altogether.
By the same token, other solar systems (which are more and more looking like the norm, rather than the exception) could shed accreted bodies. How many extra solar bodies are out there? How many might cross through our solar system without our knowledge?
I still think the idea that encounters with interstellar dust clouds is a reasonable hypothesis for explaining extreme ice ages. It seems to have lost favor. But astronomers are finding so much dust everywhere they look that it almost seems like it should be common…
astronomers are finding so much dust everywhere they look
Is that what keeps them from being able to find Dark Matter?
I still think the idea that encounters with interstellar dust clouds is a reasonable hypothesis for explaining extreme ice ages. It seems to have lost favor. But astronomers are finding so much dust everywhere they look that it almost seems like it should be common…
There’s two problems with that. First, the Sun produces a lot of pressure (solar wind and EM radiation) that would push aside low density has. The heliosphere boundary (in the direction of the Solar System’s travel) is a considerable distance away (at 75-90 AU). To push it within the orbit of Earth, you’d need some sort of momentum density at least three orders of magnitude greater than interstellar medium. Having said that, a knot of dense gas heading in the opposite direction at the same speed as the Sun travels (225 km/s) would take only about nine months to a year to reach Earth from first contact with the heliopause (assuming it wasn’t slowed down in the least by its interaction with the solar wind/light pressure from the Sun).
The idea, as I see it, would be that the actual diminution of the Sun’s light with Earth would be due to the heliopause getting pushed to between Earth and the Sun (and becoming far denser and opaque than it currently is).
The second problem is that we don’t see many of these knots of dark gas. Interstellar space must be pretty clear of such things else we wouldn’t see so much of the galaxy.
For example, if the last ice age were triggered by a nebula going in the opposite direction, where might the cloud be now? Glancing at Wikipedia, it appears that the start of the last ice age was about 120k years ago. Assuming the cloud and the Sun were traveling in nearly opposite directions, a 450 km/s difference, that means that the cloud is traveling away from us at 0.0015 C (0.15% the speed of light) or 1.5 lightyears every millennium. That means it’s around 180 lightyears away from us now somewhere behind us. That’s pretty much the worst case scenario.
I have no idea how large and dense such a nebula would need to be to collapse the heliopause to under Earth’s orbit, but my take is that it probably would still be visible from Earth, even at 180 lightyears away.
This site lists nearby dark nebula. None of them are closer than roughly 330 light years to us.
Dinosaurs had labor unions?
Come to think of it, that makes sense.
This would better explain some evidence that the K-T boundary wasn’t a sharp line of demarcation, but an extended event.
One has to wonder whether we’re being too restrictive in our thinking about the source of extraterrestrial bombardment. Our own solar system is full of objects in orbits whose eccentricity ranges from 0 to 0.9999… Given the right gravitational encounter with one of the planets, an object with e = 0.9999 could easily just leave the solar system altogether.
By the same token, other solar systems (which are more and more looking like the norm, rather than the exception) could shed accreted bodies. How many extra solar bodies are out there? How many might cross through our solar system without our knowledge?
I still think the idea that encounters with interstellar dust clouds is a reasonable hypothesis for explaining extreme ice ages. It seems to have lost favor. But astronomers are finding so much dust everywhere they look that it almost seems like it should be common…
Is that what keeps them from being able to find Dark Matter?
I still think the idea that encounters with interstellar dust clouds is a reasonable hypothesis for explaining extreme ice ages. It seems to have lost favor. But astronomers are finding so much dust everywhere they look that it almost seems like it should be common…
There’s two problems with that. First, the Sun produces a lot of pressure (solar wind and EM radiation) that would push aside low density has. The heliosphere boundary (in the direction of the Solar System’s travel) is a considerable distance away (at 75-90 AU). To push it within the orbit of Earth, you’d need some sort of momentum density at least three orders of magnitude greater than interstellar medium. Having said that, a knot of dense gas heading in the opposite direction at the same speed as the Sun travels (225 km/s) would take only about nine months to a year to reach Earth from first contact with the heliopause (assuming it wasn’t slowed down in the least by its interaction with the solar wind/light pressure from the Sun).
The idea, as I see it, would be that the actual diminution of the Sun’s light with Earth would be due to the heliopause getting pushed to between Earth and the Sun (and becoming far denser and opaque than it currently is).
The second problem is that we don’t see many of these knots of dark gas. Interstellar space must be pretty clear of such things else we wouldn’t see so much of the galaxy.
For example, if the last ice age were triggered by a nebula going in the opposite direction, where might the cloud be now? Glancing at Wikipedia, it appears that the start of the last ice age was about 120k years ago. Assuming the cloud and the Sun were traveling in nearly opposite directions, a 450 km/s difference, that means that the cloud is traveling away from us at 0.0015 C (0.15% the speed of light) or 1.5 lightyears every millennium. That means it’s around 180 lightyears away from us now somewhere behind us. That’s pretty much the worst case scenario.
I have no idea how large and dense such a nebula would need to be to collapse the heliopause to under Earth’s orbit, but my take is that it probably would still be visible from Earth, even at 180 lightyears away.
This site lists nearby dark nebula. None of them are closer than roughly 330 light years to us.