Ask a physicist anything. (8)

[pgp_protector]

What would happen if an anti-proton came in contact with a neutron?

You really can find almost anything with Google

5 Protonium and antiprotonic deuterium

 

[essentialsaltes]

What would happen if an anti-proton came in contact with a neutron?

If the two particles were essentially at rest, I think the most likely thing would be for two pions to be emitted. One would be a negatively charged pion, while the other would be a neutral pion. Because the antiproton and neutron have more rest mass than the pions, the pions would come out with a lot of kinetic energy, so that the total energy was conserved. Pions are not stable, so ultimately they would decay as well.

If the antiproton was fired at the neutron at high energy in an accelerator, then all sorts of things could happen, since there would be additional energy to make all sorts of particles.

 

[Sofaman]

Kind if a question but more something to ponder.

I'm effectively a layman when it comes to physics and science but with a developing amateur interest and deep regret that I didn't pursue an education in science in my school days.

It's something that I thought of when watching a documentary on the acceleration of the expansion of the universe and really the lack of understanding we currently have. Correct me if I'm wrong but I think it may be put down to dark matter??

What if there's another explanation. What if, our four dimensional universe is the product of a super massive shockwave of a star going supernnova within another 5 dimensional universe and the increase in expansion is that shockwave getting further and further away from the resultant black hole within that 5 dimensional universe and therefore escaping it's gravity. Thus removing the need for an explanation of the acceleration of the expansion.

I think I've read somewhere that it's hypothesized that if an object were to fall into a black hole, from the outside observer, an image of that object would be preserved forever in 2D on the event horizon. I think it may have been Neil Degrasse Tyson who said it. Hence my 5D to 4D in my quandry (if you include spacetime).

Anyway, thoughts?

If I've just written a load of gibberish, just say so, I have think skin!

 

[Chesterton]

If I've just written a load of gibberish, just say so, I have think skin!

No, not at all. Stick around this forum awhile if you want to see some real gibberish.

 

[Wiccan_Child]

Kind if a question but more something to ponder.

I'm effectively a layman when it comes to physics and science but with a developing amateur interest and deep regret that I didn't pursue an education in science in my school days.

It's something that I thought of when watching a documentary on the acceleration of the expansion of the universe and really the lack of understanding we currently have. Correct me if I'm wrong but I think it may be put down to dark matter??

Dark matter is inferred to exist because galaxies spin faster than they should, implying there's more mass, but we can't see it, so it's dark - hence, dark matter.

Dark energy is the energy that goes into the metric expansion of spacetime. Again, only theoretically inferred, hence 'dark'.

What if there's another explanation. What if, our four dimensional universe is the product of a super massive shockwave of a star going supernnova within another 5 dimensional universe and the increase in expansion is that shockwave getting further and further away from the resultant black hole within that 5 dimensional universe and therefore escaping it's gravity. Thus removing the need for an explanation of the acceleration of the expansion.

I may have seen the same documentary Two membranes collide, and at the point of collision there is a ripple that spreads outwards. Only now the membranes are superhuge and the collision is hyperdimensional and the ripple is our universe - the collision was the Big Bang.

But this doesn't solve the problem. Ripples from a collision travel at the speed of sound in that medium; they don't accelerate. But the expansion of the universe is accelerating - why? Where's the energy coming from? The 'm-brane collision' hypothesis explains the origin of the universe and why it's expanding... but not why it's accelerating.

Unless extra-universal collisions between hyperdimensional m-branes don't operate the way we think

I think I've read somewhere that it's hypothesized that if an object were to fall into a black hole, from the outside observer, an image of that object would be preserved forever in 2D on the event horizon. I think it may have been Neil Degrasse Tyson who said it.

He's right. Objects falling into a black hole experience tremendous time dilation and length contraction to an outside, such that you never see them actually hit the centre - they get slower and slower, flatter and flatter, forever.

 

[Sofaman]

But this doesn't solve the problem. Ripples from a collision travel at the speed of sound in that medium; they don't accelerate. But the expansion of the universe is accelerating - why? Where's the energy coming from? The 'm-brane collision' hypothesis explains the origin of the universe and why it's expanding... but not why it's accelerating.

I'm imaging the universe as a bubble or balloon expanding away from the remnant of that collision, a really really big black hole say. The universe would be the rubber of the balloon, the inside of the balloon would be outside of our universe. The universe has a certain amount of outward momentum. As it expands, it gets further and further away from the black hole so it has less gravity pulling on it and therefore the momentum can takeover and accelerate the expansion.

 

[Wiccan_Child]

I'm imaging the universe as a bubble or balloon expanding away from the remnant of that collision, a really really big black hole say. The universe would be the rubber of the balloon, the inside of the balloon would be outside of our universe. The universe has a certain amount of outward momentum. As it expands, it gets further and further away from the black hole so it has less gravity pulling on it and therefore the momentum can takeover and accelerate the expansion.

Momentum doesn't work that way In that scenario, it will constantly lose momentum, but the further away it goes, the more slowly momentum is lost. But there's never a point where it starts gaining momentum, unless there's a force involved (such as a second black hole further away that we then begin accelerating towards).

As well, the universe isn't expanding away from a fixed point in space - you can't fly to the centre of the universe and say "Aha, everything's moving away from this point". Every point is moving away from every other point, every galaxy is receding from every other galaxy. There is no centre of expansion, because everywhere is expanding at once. Which begs the question... why? And why is it getting faster?

And then there's inflation, which is just plain Lovecraftian in its weirdness.

 

[Sofaman]

I take your point about momentum but fixed point in space element is exactly what you would see if our universe were expanding as a balloon. If you were to draw a grid of dots on a balloon and blew it up the further away from each other they would get. The bigger the bubble got, the quicker they would seem to move from each other giving the illusion of acceleration.

The expansion from a fixed I was talking about would mean the fixed point would be outside of the universe (the rubber of the balloon); or right in the centre of the balloon if you get me?

 

[Wiccan_Child]

I take your point about momentum but fixed point in space element is exactly what you would see if our universe were expanding as a balloon. If you were to draw a grid of dots on a balloon and blew it up the further away from each other they would get. The bigger the bubble got, the quicker they would seem to move from each other giving the illusion of acceleration.

Well, it's not that they would seem to accelerate, they would accelerate. But the problem of energy yet remains: increasing the radius of a balloon linearly needs more than a linear input of energy. You need an exponentially larger input of air, and an exponentially stronger force to combat the reactive elastic of the balloon's material.

In general terms, to exponentially increase the surface (or volume, in the case of the universe) requires an exponential increase in the energy needed to do the expanding.

The expansion from a fixed I was talking about would mean the fixed point would be outside of the universe (the rubber of the balloon); or right in the centre of the balloon if you get me?

Sure - the universe could be a 3D volume expanding into 4D space, just as a balloon is a 2D surface expanding into 3D space. But then 4D topology gets involved and it's not quite as simple as looking at 3D space and drawing an analogue. Adding an extra spatial dimension, and having an even number of dimensions, makes things behave all sorts of weird (no solar systems, for instance!).

 

[Seipai]

I just saw this article:

http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html

Magnetic monopoles have been observed. What will that result in?

 

[Justatruthseeker]

Well, it's not that they would seem to accelerate, they would accelerate. But the problem of energy yet remains: increasing the radius of a balloon linearly needs more than a linear input of energy. You need an exponentially larger input of air, and an exponentially stronger force to combat the reactive elastic of the balloon's material.

In general terms, to exponentially increase the surface (or volume, in the case of the universe) requires an exponential increase in the energy needed to do the expanding.


Sure - the universe could be a 3D volume expanding into 4D space, just as a balloon is a 2D surface expanding into 3D space. But then 4D topology gets involved and it's not quite as simple as looking at 3D space and drawing an analogue. Adding an extra spatial dimension, and having an even number of dimensions, makes things behave all sorts of weird (no solar systems, for instance!).

Yes, that is the problem with not just expansion, but accelerating expansion. The energy input must be increasing, violating all the known laws of physics.

The other problem is theorists seem to have nothing better to do than dream of extra dimensions, wormholes, etc, etc, when they need to be worring about the thigs we take for granted yet have no clue as to how they really work.

 

[Wiccan_Child]

Yes, that is the problem with not just expansion, but accelerating expansion. The energy input must be increasing, violating all the known laws of physics.

It violates no law of physics. A system can accelerate so long as it is given energy. We don't know much abut this energy, hence the term 'dark energy'. But there's no violation of any law of physics - it's just energy from an unknown source. Maybe it's extra-universal. Maybe it's hyper-dimensional.

Of course, maybe it's because expanding spacetime continua don't obey the laws of thermodynamics, meaning it does indeed break the known laws of physics - because we got them wrong. The laws of physics are not sacrosanct, and if we got them wrong, so be it. Particle physics overturned classical mechanics, so perhaps cosmology will overturn classical thermodynamics. But the point is moot - as it stands, dark energy doesn't violate "all known laws of physics", nor indeed a single one.

The other problem is theorists seem to have nothing better to do than dream of extra dimensions, wormholes, etc, etc, when they need to be worring about the thigs we take for granted yet have no clue as to how they really work.

I'm sorry, but who are you to tell people what field of study they should be interested in?

 

[Michael]

I just saw this article:

http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html

Magnetic monopoles have been observed. What will that result in?

If it's ultimately shown to be true, it would result in minor changes to Gauss's laws.

It's hard to say much since I haven't read the full paper yet, but looking at the images of the condensates, it's looks to me like the whole condensate has taken on a type of polar "charge", with red and green regions representing different charge states in the condensate, with a blue "ring" representing a more neutral region separating them. They show several images of the condensate "ball" (for lack of a better term) from several angles, and that's kind of what it looks like to me anyway. I wouldn't jump to a lot of hasty conclusions yet based on one paper, but it's an interesting paper, and thanks for posting it.

 

[Michael]

I would add that if the condensate is acting as a moving 'conductor', in a magnetic field, ordinary induction might explain the polar charge build up on the condensate. Like I said, I wouldn't read too much into a single paper just yet.

 

[Justatruthseeker]

I would add that if the condensate is acting as a moving 'conductor', in a magnetic field, ordinary induction might explain the polar charge build up on the condensate. Like I said, I wouldn't read too much into a single paper just yet.

Oh, but modern science has a tendency to jump to conclusions. Just as with the Higg's Bosun. Not that I am against the idea of it at all, as standard theory predicts it, but one maybe out of 50,000 negative results does not a conclusive positive make, yet it is toted as a fact of discovery, not a maybe that needs more experimental verification. A test that to date has not been able to be reproduced, by even the same laboratory that produced the first maybe.

of course they got their continued funding after the first claim, so I expect we won't hear anything until it is time for funding once again.

 

[Wiccan_Child]

If it's ultimately shown to be true, it would result in minor changes to Gauss's laws.

It's hard to say much since I haven't read the full paper yet, but looking at the images of the condensates, it's looks to me like the whole condensate has taken on a type of polar "charge", with red and green regions representing different charge states in the condensate, with a blue "ring" representing a more neutral region separating them. They show several images of the condensate "ball" (for lack of a better term) from several angles, and that's kind of what it looks like to me anyway. I wouldn't jump to a lot of hasty conclusions yet based on one paper, but it's an interesting paper, and thanks for posting it.

The article I read implied it wasn't magnetic monopoles that were discovered (which would be monumental, even if, as you say, we'd only a minor change to EM laws), but that they were able to simulate one with a BE condensate. Which is still pretty cool.

 

[Seipai]

The article I read implied it wasn't magnetic monopoles that were discovered (which would be monumental, even if, as you say, we'd only a minor change to EM laws), but that they were able to simulate one with a BE condensate. Which is still pretty cool.

The original article that I saw and linked said that they observed the "controlled creation" of Dirac Monopoles in a BE condensate. To be fair I could read only the abstract:


http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html

This article said that they "emulated" monopoles:

Bose-Einstein condensates used to emulate exotic magnetic monopole | Ars Technica

 

[Justatruthseeker]

The original article that I saw and linked said that they observed the "controlled creation" of Dirac Monopoles in a BE condensate. To be fair I could read only the abstract:


http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html

This article said that they "emulated" monopoles:

Bose-Einstein condensates used to emulate exotic magnetic monopole | Ars Technica

Yes, got a result that appears the same, but appearances can be deceiving. And if we are going to take computer simulations as fact, then we need to throw out supernova.

For over 25 years that model has failed to work.

http://science1.nasa.gov/science-news/science-at-nasa/2010/07jan_nustar/


Why Won't the Supernova Explode? - NASA Science

 

[Jonathan Jarvis]

New Question:

What evidence is there left of the star that spawned our sun and solar system.

I understand that our sun is not large enough to create sub ferrous elements so the existence of heavy elements must be one. Are there any others?

Also what do we know about it and has anyone given it a name?

If the universe is just over 13 billion years old and the earth about 4.5 billion years old what would roughly be the timescale of this star's existence.

 

[Wiccan_Child]

New Question:

What evidence is there left of the star that spawned our sun and solar system.

The remnants became the Sun, planets, moons, and asteroids. Evidence exists in the ratio of elements that exist in the solar system: we have uranium, after all.

I understand that our sun is not large enough to create sub ferrous elements so the existence of heavy elements must be one. Are there any others?

The asteroids are another; that they have the same material, ratios, ages, etc, confirms the nebular hypothesis.

Also what do we know about it and has anyone given it a name?

Not to my knowledge.

If the universe is just over 13 billion years old and the earth about 4.5 billion years old what would roughly be the timescale of this star's existence.

Unknown, though it's thought our sun is a 3rd generation star.