**Ask a monkey a physics question thread**

[OngBonga]

so i hear that there is no edge to the universe and that physicists don't know if it's finite or infinite. doesn't the universe not having an edge mean it's infinite?

Does the surface of a sphere have an edge? Is it infinite?

[wufwugy]

Does the surface of a sphere have an edge? Is it infinite?

it does, but one that can only be perceived in at least 3 dimensions.

If it's finite but edgeless, then it wraps around.

are you saying that if we were an infinitely cloned ftl spacecraft, we could travel from an origin into every 3d direction and eventually run into each other?

[OngBonga]

it does, but one that can only be perceived in at least 3 dimensions.

Yeah there's limitations to that analogy, but it at least demonstrates that boundless does not equal infinity.

I have a phsyics question... how does a dead woman cure a brain tumour?

[wufwugy]

im assuming boundless as well as whatever it is when you call not reaching a previous point by moving in one direction. an ant on the balloon can discover the surface is not infinite just by walking in singular directions. afaik, physicists do not believe that a super spaceship that can cover the universe could do the same. so that's where im scratching my head. doesn't this necessitate infinity?

[MadMojoMonkey]

so i hear that there is no edge to the universe and that physicists don't know if it's finite or infinite.

The collective IDK is the important thing to take from this.

If there is an edge, it has not yet been detected.

doesn't the universe not having an edge mean it's infinite?

Not necessarily. NG and ong both make interesting points.

The surface of a sphere has no edges, but is a finite area. Same for a torus.

Fractals are mathematical objects with interesting properties. They can have an infinite perimeter enclosing a finite surface area.

An "infinitely bumpy" surface may have infinite area, yet enclose a finite volume.

All of this is easily extrapolated into higher dimensions mathematically. The fact that all my examples are about area, and not volume is intentional. It's hard (impossible?) to visualize a volume as the infinite bound of a finite 4-dimensional object. Still, there is no reason that is not a valid description of the universe.

Valid doesn't mean correct, merely possible given our current understanding.

[wufwugy]

where most of my confusion arises is how the ant on the balloon can travel in a constant direction and reach a spot he was before while a man in a magic-fast spaceship (presumably) cannot.

[wufwugy]

unless the balloon is constantly inflating. then the ant never reaches the same point twice.

that makes sense, but i guess im confused on how that doesn't make the balloon surface infinite.

[wufwugy]

i mean, if there is always a new point in spacetime, that means there are infinite points in spacetime, which means spacetime is infinite right?

[OngBonga]

I would have answers which correspond with my idea of the universe. I would say that a spaceship that has infinite time and infinite fuel travelling in a straight line will eventually reach the same point in space again, provided in can stand the pressure of the big crunch - big bang in the centre of the universe, which I doubt.

[OngBonga]

The surface of a sphere has no edges, but is a finite area. Same for a torus.

Bolded goes along my stoned line of thinking.

[wufwugy]

that makes me think of something else. a while back i read (from hawking i think) that if the universe started deflating instead of inflating, maybe things would be really funky like time moving backwards. what does this mean?

[OngBonga]

I think it helps to understand that spacetime itself is curved.

We like to think that the moon orbits the Earth by following a curved path around us that draws a circle... well, an ellipse... but this model isn't actually correct. The moon follows a straight line through curved spacetime, it is the Earth's gravity that curves spacetime. If the moon was constantly turning towards us, it would constantly lose momentum. It isn't losing momentum (aside from the tiny effects of tidal forces, but forget that), so it's going in a straight line. But we can see it isn't.

As we go away from the centre of the universe, we might be travelling in a straight line, but we're probably always travelling through curved space. So, an observer outside of the universe might not see us travelling in a straight line, even though we are. Like the moon is.

[MadMojoMonkey]

where most of my confusion arises is how the ant on the balloon can travel in a constant direction and reach a spot he was before while a man in a magic-fast spaceship (presumably) cannot.

Don't be so positive about that spaceship. Space contraction and time dilation could give him a serious advantage.

As you move closer and closer to the speed of light, distances in your direction of travel are contracted. The universe becomes pancaked in your direction of travel. Also, clocks outside your ship tick more slowly. So the rate of the universe's expansion would be slowed as well.

Now to create a ship that can hold a constant acceleration indefinitely and see if it can accelerate enough to overcome the universe's accelerating expansion.

unless the balloon is constantly inflating. then the ant never reaches the same point twice.

that makes sense, but i guess im confused on how that doesn't make the balloon surface infinite.

How can that be confusing? It's just a balloon that is inflating. Still finite at any finite future time.
(We must assume this balloon is made of some material with infinite stretchiness and infinitesimal thickness.)

i mean, if there is always a new point in spacetime, that means there are infinite points in spacetime, which means spacetime is infinite right?

There are always more numbers between 0 and 1 than can ever be listed, therefore the distance between 0 and 1 is infinite, right?

No.

[OngBonga]

Yeah the inflating balloon has infinite potential surface area, but it's finite at any given moment in time.

[MadMojoMonkey]

I would have answers which correspond with my idea of the universe. I would say that a spaceship that has infinite time and infinite fuel travelling in a straight line will eventually reach the same point in space again

I don't see any good evidence for or against this. It's not like we can point a telescope in some direction and see the Earth really faint in the distance.

Yet.

Figure out how to test this and earn yourself a Nobel Prize.

provided in can stand the pressure of the big crunch - big bang in the centre of the universe, which I doubt.

Not the center of the universe. The whole universe.

The story goes that the universe has stopped expanding and then contracts again. It's not moving back through itself; it's contracting.

When the Big Crunch happens, it will happen everywhere, all at once. Just like the Big Bang. It didn't happen at the "center" so much as it WAS the universe. The entire universe was the entire Big Bang.

The Big Bang isn't something that happened to the universe any more than being a toddler is something that happened to you.

(Bear with me on this one, despite it's flaws, I think you'll like it
Where did your toddler take place? Was it in your head? Your belly? No. It was happening everywhere, to all of you. Did you expand into something else as you got bigger? No, you expanded to a bigger you.

(Obv. this is a very loose metaphor, please don't take it any further than this.)

[wufwugy]

Don't be so positive about that spaceship. Space contraction and time dilation could give him a serious advantage.

As you move closer and closer to the speed of light, distances in your direction of travel are contracted. The universe becomes pancaked in your direction of travel. Also, clocks outside your ship tick more slowly. So the rate of the universe's expansion would be slowed as well.

Now to create a ship that can hold a constant acceleration indefinitely and see if it can accelerate enough to overcome the universe's accelerating expansion.

it's not reasonable to think that something with infinite speed and 3d travel facilities can't reach every point in space at any given time?

How can that be confusing? It's just a balloon that is inflating. Still finite at any finite future time.
(We must assume this balloon is made of some material with infinite stretchiness and infinitesimal thickness.)

so for something to be infinite, it has to be infinite at any one point in time?

There are always more numbers between 0 and 1 than can ever be listed, therefore the distance between 0 and 1 is infinite, right?

it's intuitive. what i think i dont understand is this: there are an infinite many numbers between 0 and 1. this suggests to me that something that travels to each of those numbers can never reach them all. from his perspective, he is traveling infinitely and reaching new places. if so, why can't we say that the distance he is traveling is infinite?

[MadMojoMonkey]

that makes me think of something else. a while back i read (from hawking i think) that if the universe started deflating instead of inflating, maybe things would be really funky like time moving backwards. what does this mean?

Sounds like nonsense to me.

It wouldn't mean anything on the QM level, and everything above that is just a statistical amalgamation of the underlying particles doing their thing.

Every process in QM is time symmetric. Meaning that if it happens one way, you could play the recording backwards and nothing would look odd. Every Feinman Diagram which shows an observed phenomenon in the universe can be read backwards along its time axis and it will still describe a phenomenon which is observed in the universe.

So my question is: How would we even notice if time was flowing backward? Would the Laws of Thermodynamics break down? Would Entropy be never increasing rather than its current state of never decreasing?

[MadMojoMonkey]

it's not reasonable to think that something with infinite speed and 3d travel facilities can't reach every point in space at any given time?

I don't see how any macroscopic thing can be in all the places at one time. Even with particles, we're talking about their wave function being non-zero over any volume, but it's so damn near to zero over most of the universe. "Most" being an understatement of universal proportions. The probability of finding an electron which is bound to an atom further than 1 nm from that nucleus is nearly infinitesimal. It drops off exponentially. While it is non-zero everywhere, it is ridiculously small even a few atomic radii in distance from the parent nucleus.

so for something to be infinite, it has to be infinite at any one point in time?

I'm saying the balloon is finite in surface area at the beginning of our little thought experiment. Its rate of expansion is always finite. Therefore, it can only be of finite surface area after any finite amount of time passes.

I would say that the only way this balloon can have infinite surface area is if an infinite amount of time passes. When I use infinite here, I mean the non-number version if infinity which is a concept of unendingness.

I'm basically calling BS on your notion that the balloon is infinite at any "real" time, but not on your notion that the idea of infinity is not completely discarded from this balloon's state in some arbitrarily distant future.

it's intuitive. what i think i dont understand is this: there are an infinite many numbers between 0 and 1. this suggests to me that something that travels to each of those numbers can never reach them all. from his perspective, he is traveling infinitely and reaching new places. if so, why can't we say that the distance he is traveling is infinite?

... but the distance between the numbers is infinitesimal.

So, sure, you can say he's traveled infinite distance, but does it hold significant meaning?

There are many uses of infinity. Even mathematically, we acknowledge that not all infinities are equal. Sometimes we treat infinity like a number, especially when doing integrals, but there are so many other examples.

The various uses of infinities are appropriate in their own contexts.

[OngBonga]

Figure out how to test this and earn yourself a Nobel Prize.

I would get a great deal more pleasure turning down a nobel prize than accepting one. Look, I don't even use a capital letter for nobel. Fuck you alfred.

I have no idea really. I mean the torus is such a great model, and corresponds perfectly with our ideas of conservation of energy, and equilibrium... it's so perfect. Well, nearly. The expansion of the universe appears to be increasing, which I can't get my head around in any model really. There must be a reason for this, and I think it's geometry.

[OngBonga]

The idea of time flowing backwards in fundamentally flawed. The word "backwards" is immediately reliant on a relative state. You're only going backwards if something comparable is going in another direction. So you mean "backwards" relative to now time? What, your time? Or mine? Because I'm pretty sure we're moving at very slightly different velocities through spacetime, thanks to our different altitudes and slightly different distances from the sun, moon and planets, as well as the near zero (but not actually zero) effect that standing by a hill makes. All these means we're actually travelling through spacetime at very slightly different rates.

Time isn't a straight line where it's one way or the other.

[MadMojoMonkey]

Gravitational Waves confirmed!

The LIGO (Laser Interferometer Gravitational wave Observatory) scientists report the first ever confirmation of gravitational waves. They detected an event on September 14, 2015 during a non-science test of the facilities' updated equipment. After months of ensuring that what they detected (nearly simultaneously at both facilities, thousands of miles apart) was not a fluke or mistake, and having their findings peer-reviewed, they have announced their discovery.

The peer reviewed paper has just been published and I have not yet read it.

A bit more info about what was observed:
The event happened 1.3 billion light years away/ago. It was a merger of 2 black holes, both near 30 solar masses, into a single, larger black hole. The event emitted more power than all of the stars in the universe combined for ~20 milliseconds. The final black hole is 3 solar masses less than the combined masses of the 2 "parent" black holes. This difference of 3 solar masses is the amount of energy that was released in the form of gravitational waves during the event. I.e. 3*mc^2, where m is the mass of the sun, energy was converted from mass energy to gravitational wave energy in ~20 milliseconds.

Wowwee!


This is effectively the first thing we've seen with this new kind of eyes we made.

[oskar]

How do they go from seeing some particles move to pinpointing the exact place and distance of the double blackhole system?
And what would such an event mean for a solar system that was, let's say only 1 million light years away from that thing?

[Eric]

Yeah, this is all over the news. Very exciting!

[MadMojoMonkey]

How do they go from seeing some particles move to pinpointing the exact place and distance of the double blackhole system?

We don't know the exact place of the event. We know the distance (more or less) and an area of the sky in which it most likely occurred - kind of a long arching crescent shape in the southern sky near the large magellanic cloud.

Basically, it's not too dissimilar to radar. One radar can tell you the distance, but that still leaves you with a circle around you where it could be anywhere on that circle, since all of those locations are the same distance. However, introduce a second radar station which identifies the same event, and you have 2 overlapping circles, one from each radar station. So you've narrowed it down to only 2 locations. With a third station, you can pinpoint the exact location because its circle will only intersect one of the two points created by the other 2 circles.

They were able to determine the size of the 3 black holes from the data - parents were 29 and 36 solar masses, the daughter is 62 solar masses - as well as the distance. This is done by matching up the predictions made by Einstein's Field Equations about this kind of event to the actual observations. My guess is that the 2 observatories both measured the distance and the discrepancy in their timing has left us with a kind of wedge shaped piece of the sky which is where our "radar circles" overlap. It's noteworthy that our 2 "stations" are really close together compared to the distance of the signal. So the circles are very nearly identical and their crossing is like 2 nearly parallel lines with only a very slight angle between them. This is why we've narrowed it down to a wedge shape, but not an exact location.

And what would such an event mean for a solar system that was, let's say only 1 million light years away from that thing?

As far as the gravitational waves are concerned, practically nothing. We're not talking about any kind of visibly noticeable effects. What LIGO detected was a change in lengths of about 1/1000 the diameter of a proton over 4 km. That's equivalent to measuring the distance from the sun to it's nearest starry neighbor to within about 1/2 the diameter of a hair.

In general, being close to a black hole is pretty dangerous, especially so if that black hole has an accretion disk. They tend to emit a lot of high energy particles and rays which are quite destructive to ... well, atoms - aka all the things.

I honestly don't know how close you would need to have been to have seen any noticeable effects.

[OngBonga]

This is done by matching up the predictions made by Einstein's Field Equations about this kind of event to the actual observations.

Does this not bring in a natural bias towards confirming what you expect to confirm? How can we be sure that what was measured was the result of gravitational waves from 100 billion light years away or whatever, and not as a result of something else, such as a small earthquake in China, or something ridiculous like that?

It seems to me that we're confirming gravitational waves based on some heavy assumptions. We seem to be "proving" Einstein's equations simply by applying them.

I'm not for a minute suggesting they're wrong, by the way. I'm just don't understand how they can use theoretical equations to confirm the theory which those equations are based on. Something doesn't add up, and I can't quite put my finger on it.

[CoccoBill]

NDT to the rescue:

https://www.youtube.com/watch?v=DoOPEPVYAnU

[Eric]

Are there any cliff notes on gravity waves? What would happen if our sun were to evaporate?

[OngBonga]

Evaporate? You mean cease to exist? That's a mere thought experiment that cannot happen in the real world. Matter doesn't just disappear, its gravitational influence will always exist. The sun will "evaporate" over a period of hundreds of billions of years. As the sun expands, its density will reduce, and as such it will warp spacetime to less of an extent... it will decrease in gravity. But this will be the least of our problems on Earth, we'll be long gone before the decreased gravity results in our planet drifting away from the sun.

Trying to imagine the gravitational consequences of the sun suddenly disappearing is a waste of time. You'd be better off trying to figure out how to rig the lottery... at least that might be possible.

[MadMojoMonkey]

Does this not bring in a natural bias towards confirming what you expect to confirm?

I think you missed the line where this data wasn't even acquired on a "science" run of the equipment. They were performing a test of the equipment at the time the event was recorded. This sheds even more doubt as to the accuracy of their finding.

This doubt has been through the ringer as to trying to find any alternate explanation that makes better sense of the findings. Were they a fluke of the equipment? No. Were they some unfiltered noise? No.

How can we be sure that what was measured was the result of gravitational waves from 100 billion light years away or whatever, and not as a result of something else, such as a small earthquake in China, or something ridiculous like that?

I haven't yet read the peer reviewed paper, but it seems that they have identified all of the other wave signals they were receiving, and subtracted them from the overall signal. The event's signal is what's left after all the stuff we know about and can account for has been accounted for.

Also, the LIGO experimental setup is far and away the highest precision measuring device ever constructed, and it is definitely sensitive to earthquakes. It is the most precise seismometer in the world, as a matter of fact. They know this and they are more clever than I even know at isolating out these Earth-born effects.

It seems to me that we're confirming gravitational waves based on some heavy assumptions. We seem to be "proving" Einstein's equations simply by applying them.

I'm not for a minute suggesting they're wrong, by the way. I'm just don't understand how they can use theoretical equations to confirm the theory which those equations are based on. Something doesn't add up, and I can't quite put my finger on it.

I feel like we've been through this before, you and I.

I can tell you that F = ma and that acceleration due to gravity near the Earth's surface is 9.8 m/s^2. Then I draw you a diagram of a pendulum. With a bit of knowledge about trig. and algebra, you could make a prediction for the period of oscillation of that pendulum.

Now... you go out into the world and you find a pendulum. Someone tells you it's waving 'cause of gravity. You do the math, and you find that you calculate the period of oscillation that you experimentally observe.

The description fits the results, even though the description was not about "this" pendulum. It wasn't even about pendulums, it was about forces and accelerations. Is this not a compelling reason to think the theory is at least robust enough to describe this phenomenon?

Basically this is what's happened. We made a device to measure unbelievably minute amounts of strain. We expected to use it to see gravitational waves. Then we see a thing. We do the math, assuming that it's what we think it is, and we find that the description is robust enough to explain this thing.

It's not proof, by any means. It is a strong indication that the theory is at least robust enough to pay attention to and do some more observing and mathing.

[OngBonga]

The description fits the results, even though the description was not about "this" pendulum. It wasn't even about pendulums, it was about forces and accelerations. Is this not a compelling reason to think the theory is at least robust enough to describe this phenomenon?

Yeah cool, you're making a very clear distinction here between compelling evidence and proof. I think my assumption was that they were ready to prove graviational waves based on the first physical indication they exist. I'm happy that what they've published so far is compelling and worthy of further investigation, but neither would I be surprised if they said the anomoly was caused by lightning or some other totally random factor.

[NightGizmo]

So if there are gravitational waves, does that mean that there are associated gravity particles? If it was this hard to find the waves, how hard would it be to find evidence of gravity particles?

[MadMojoMonkey]

Are there any cliff notes on gravity waves? What would happen if our sun were to evaporate?

Cliff notes on gravity waves.
Einstein's General Relativity says that matter tells space-time how to curve and curves in space-time tell matter how to accelerate.

There are more pithy statements, but I like this one for right now.

If you are prepared to accept this point, the gravity waves are already in there.

Space-time is curved by a certain mass at a certain location. The curvature accelerates that mass, meaning that it is no longer in the same location, and the source of the curvature has moved, so the curvature must have changed. The propagation of this change in the curvature is a gravity wave.

***
The sun evaporating is tricky to answer, because where and how that mass-energy is dissipated makes a difference.

If the sun completely evaporated into gravitational waves (by some unknown mechanism), then it's a different story to if the sun "burns out" or expands to the point of evaporative cooling.

This one is probably the most like the "What if the sun were suddenly and inexplicably gone?" question.

Everything in our solar system would stop orbiting the sun (which isn't there to orbit anymore). It would instead start orbiting the next largest gravitational center, which would be the center of the Milky Way. It would all get very cold and very dark all of a sudden. There is little likelihood that anything that is not already a bound planet-moon system would become so bound. That is, Jupiter, for instance, would be orbiting the galactic center, with all of it's moons, but not it's Jovian Asteroids (which are bound to the lagrange points associated with the Jupiter-Sun system).

I'll have to learn about the intensity of gravitational waves when you're up close to them. I expect to see an increase in seismic activity resulting from treating planets like a stress ball. I'm sure it would if the effect is large, but it could be quite small, even up close. I have no idea.

[MadMojoMonkey]

So if there are gravitational waves, does that mean that there are associated gravity particles? If it was this hard to find the waves, how hard would it be to find evidence of gravity particles?

Huh...
Well, either gravity waves are wave-particles, or they're not quantized. I mean, we have either (almost definitely) already detected them, or they're not there to be detected. The subtlety would be in teasing out a particle-like behavior from them.

Einstein's GR has no quantization in it, and these waves are predicted by GR. That said, there's no quantization in Maxwell's Equations or Lenz's Law, either, and we know that electromagnetic fields are quantized.

If we can demonstrate some phenomenon, like blackbody radiation, which cannot be easily explained or understood without quantization, then we'd be well suited to start really exploring a physical theory of quantum gravity.

***
For the record, I'm loving these questions. They are highlighting how new this discovery is and how little I know about it so far.

[Chusko]

If only we could pass G-waves through a slit...

This is a really good question and we're talking about an unprecedented phenomenon. We're now accustomed to quantized players in the spacetime theater, but now we're talking about spacetime itself. Who knows?

[MadMojoMonkey]

Evaporate? You mean cease to exist? That's a mere thought experiment that cannot happen in the real world.

No. The sun is "evaporating" in multiple ways.
Yes. None of these ways will cause the sun to cease to exist - as such.

As a back of the envelope calculation, it gives off over 4 million tons per second in light energy by nuclear fusion converting mass into heat and light.
As a back of the envelope calculation, it throws off over 1.6 million tons per second in protons, neutrons and electrons.

As a simple observation, these numbers are so many orders of magnitude smaller than the sun's mass that the sun is within 0.05% the mass it had 4.5 billion years ago, counting only these losses.

Matter doesn't just disappear, its gravitational influence will always exist.

Definitely no. Mass-energy changes forms from one expression of mass-energy to another and back again all the time.

All
the
time.

The sun will "evaporate" over a period of hundreds of billions of years.

Well, given stellar evolution, this is mostly true. The sun will eventually start fusing helium and become a red giant, and ultimately will experience significant mass loss during the later stages of this process, leaving behind a white dwarf.

As the sun expands, its density will reduce, and as such it will warp spacetime to less of an extent... it will decrease in gravity.

This is a very confusing topic to find good information on as a layman.

I suspect there are many planets worth of heavy metals in the core of any non first generation star like our sun. When people talk about the core of a star, they're not talking about this. They're talking about first generation stars which started as mostly pure Hydrogen with a smattering of pre-fused Helium in the core. Meaning that the only components of the star's core are it's own fusion products.

Regardless:
The core is increasing in density over time.
The fusion processes increase in activity over time.
The outer layers are pushed harder by the increased activity, so the size of the star increases.
More material is ejected as more energetic fusion processes occur in the core.

The inner part of the star is getting more dense, but the overall size of the star is increasing. The rate at which it loses mass increases, too. The total density goes down and the total mass goes down. Then at the end of the star's evolution, it sheds its entire "atmosphere" causing its total size to drop dramatically, leaving only the core. Its total density goes up dramatically.

Density is only related to gravity when you're up close.

Far away:
If the sun were replace with a hypothetical equivalent mass of different density, the Earth would orbit that object just the same. Replace the sun with a black hole. Earth don't care that it's much more dense than a star, just that the total mass is the same and in the same place.

Up close
To a very good approximation, stars are made of shells which have nearly constant density throughout that shell. The symmetry of that situation means we can treat the mass like a single particle. That is, the density is a function of the radius from the center and how much mass is in the imaginary sphere represented by that shell, M. All the mass outside that shell cancels out, due to [mathematical awesomeness]. The gravity felt at any position on the shell is that of a single particle with mass M located at the center of the shell. So the density of the shells inside effect the gravity, but not the density of the shells outside.

But this will be the least of our problems on Earth, we'll be long gone before the decreased gravity results in our planet drifting away from the sun.

The Earth is already drifting away from the sun.

I mean, real slow like.

It's gonna end up inside the red giant version of the sun, even though it will be receding more quickly then. Once it gets close enough, friction will drop it to the core to hang out with Mercury and Venus.

Trying to imagine the gravitational consequences of the sun suddenly disappearing is a waste of time. You'd be better off trying to figure out how to rig the lottery... at least that might be possible.

Don't be jaded, man.

There is so much to gain by asking these kind of hypothetical questions. Sometimes you don't even know where to start, so you start somewhere you know is silly, but you then take it seriously and see what you learn.

[OngBonga]

Well that's me told!

As a simple observation, these numbers are so many orders of magnitude smaller than the sun's mass that the sun is within 0.05% the mass it had 4.5 billion years ago, counting only these losses.

Yeah I guess I was being pedantic about the use of the word "evaporate", I mean that word either means to turn from liquid into vapour (which isn't relevant in the case of the sun), or to "cease to exist", which, in the case of the sun, will take a very long time indeed. I'm evaporating faster than the sun!

Definitely no. Mass-energy changes forms from one expression of mass-energy to another and back again all the time.

Sure, but it always has gravity, surely? My point is that matter (or energy, same thing) maintains its gravitational presence, whatever form it's in. My language isn't nearly as accurate as yours, but I'm refuting the idea that the sun's gravity can just "switch off" in an instant.

The core is increasing in density over time.

I didn't know this, and actually it surprises me as the sun expands into a red giant; my assumption (heh that word again) was that increased volume meant reduced density, and hence reduced gravity. But if the core is getting denser, well that will increase the gravity of the sun, right? So it will effectively "suck" the planets in? I figured after we'd burnt to a cinder, we'd drift away from the sun.

[OngBonga]

I didn't actually mean to hit submit there, I haven't read the whole psot!

[OngBonga]

Density is only related to gravity when you're up close.

This I wasn't aware of either. I assume this isn't 100% accurate... it seems more logical that density has negligable infleunce at long distance, rather than none? Or am I wrong and that it's a quirk of "nearness"? If so, where's the line that defines "near" and not?

There is so much to gain by asking these kind of hypothetical questions. Sometimes you don't even know where to start, so you start somewhere you know is silly, but you then take it seriously and see what you learn.

Yeah my language wasn't the best. It's not a waste of time at all. Here I am arguing shit that I have no idea about, who the hell am I to say what is and isn't a waste of time!

[MadMojoMonkey]

Well that's me told!

I hope you know that I was explaining all that with a big smile on my face and plenty of hand gestures.

Yeah I guess I was being pedantic about the use of the word "evaporate", I mean that word either means to turn from liquid into vapour (which isn't relevant in the case of the sun), or to "cease to exist", which, in the case of the sun, will take a very long time indeed. I'm evaporating faster than the sun!

You're right that I was interpreting "evaporate" with a dose of metaphor.
It's hard to know exactly what Eric meant by his question, so I made my best guess and ran with it.

Sure, but it always has gravity, surely? My point is that matter (or energy, same thing) maintains its gravitational presence, whatever form it's in. My language isn't nearly as accurate as yours, but I'm refuting the idea that the sun's gravity can just "switch off" in an instant.

Photons are massless by every theory and experiment yet devised.

Now, we can never measure anything "exactly." There is always a range of values in our measurement. No matter what we're measuring and no matter what tools we use, we will always have a range. This is nothing to do with quantum uncertainties, it's just the result of using tools to make measurements. This is separate from, and in addition to, the observer effect, which says that by measuring a thing you change the thing. (I.e. if you use a pressure gauge to check your tire pressure, then you must let air from the tire into the gauge in order to obtain your measurement.)

We haven't measured the mass of photons to be exactly 0, but we know that if they have any mass, then it's no greater than [a very tiny number]. I left out the number 'cause there's a lot of numbers out there based on different applications of theory, but all of them are quite small. The important take-away from this is that there is no experimental or theoretical evidence which suggests that photons have non-0 mass.

I didn't know this, and actually it surprises me as the sun expands into a red giant; my assumption (heh that word again) was that increased volume meant reduced density, and hence reduced gravity. But if the core is getting denser, well that will increase the gravity of the sun, right? So it will effectively "suck" the planets in? I figured after we'd burnt to a cinder, we'd drift away from the sun.

Like I said, it's difficult to find quality information on this as a layman.

Just so you know, what's going on in the core of stars is complicated and I had to make a LOT of generalizations to squeeze that paragraph down to a manageable size.

Also, everything anyone says about what's going on inside a star is theoretical. We're talking Standard Model theories and not the casual use of the word "theory," for sure. Just know that we cannot see past the outermost layers of the star from the outside. Also, we have no idea how to send a probe inside, have it not melt, and come back out to send us the data it collected.
The not melting is the hard part.

FYI, getting to the sun isn't as easy as you might imagine. The Earth's orbital speed is ~30 km/s. If you send a space ship or probe out of Earth's orbit, it's still in orbit around the sun at ~30 km/s. If you want to go to the sun, then you need to stop orbiting and start falling. The cheapest way to do this is to fly out to Jupiter, and use it as a gravitational brake to shed some speed and then start falling back to the sun.
In order to go to the sun, you have to get to Jupiter first. Weird, right?

[MadMojoMonkey]

I didn't actually mean to hit submit there, I haven't read the whole psot!

This I wasn't aware of either. I assume this isn't 100% accurate... it seems more logical that density has negligable infleunce at long distance, rather than none? Or am I wrong and that it's a quirk of "nearness"? If so, where's the line that defines "near" and not?

Good catch. You're right. I over-stated the situation.

Yeah my language wasn't the best. It's not a waste of time at all. Here I am arguing shit that I have no idea about, who the hell am I to say what is and isn't a waste of time!

I think the attitude you expressed is a common one, though.

EDIT: to demonstrate EDIT.

[MadMojoMonkey]

Hmm.

If photons have non-o mass, then the Law of Conservation of Electric Charge would break down.
Also, the force between charges would diminish at a greater rate than the 1/r^2 relationship we observe.
The gauge invariance in Quantum Electrodynamics would no longer hold.

Probably more.

I say this to convince you that photons are highly likely to have 0 mass, since these theories are quite robust, and have been experimentally confirmed for decades.

The upshot is that when matter changes form into energy, that mass is no longer expressed as mass, and does not influence things gravitationally.

So the idea that mass - I.e. gravity sources - can be destroyed is fully consistent with the Standard Model.

[OngBonga]

Also, the force between charges would diminish at a greater rate than the 1/r^2 relationship we observe.

But how accurately can we actually measure things like this? Our observations might be within the parameters that allow such a negligable mass to go unnoticed.

I can't get my head around the idea of gravity just disappearing.

[MadMojoMonkey]

But how accurately can we actually measure things like this? Our observations might be within the parameters that allow such a negligable mass to go unnoticed.

I can't get my head around the idea of gravity just disappearing.

You're asking a great question.

An accepted upper bound for the mass of a photon is 10^-18 eV/c^2 which is ~2*10^-54 kg.

eV/c^2 are units of mass that are commonly used in particle physics.
If E = mc^2, then E/c^2 = m

eV means electron Volt. It is the amount of kinetic energy an electron gains having traversed a potential difference of 1 V. Interestingly, the amount of space and time required to do so is not relevant.
1 eV = 1.6*10^-19 J

1 eV/c^2 = 1.6*10^-19 J / (3*10^8 m/s)^2 ~= 1.8*10^-36 kg


The simple fact is that even if photons have a mass as large as 10^-18 eV/c^2, it's nowhere near enough to account for the mass annihilated in, say an electron positron collision.

mass of electron + positron prior to collision: ~10^6 eV/c^2
mass of 2 photons moving in opposite directions after annihilation: ~2*10^-18 eV/c^2

That's 24 orders of magnitude in difference between the starting mass and the ending mass. This process (electron / positron annihilation) is well known and studied.

While the energy is conserved, mass is not conserved. While the total energy of the resulting photons is equal to the total energy of the initial particles, it is no longer expressed in terms of mass. If no mass, no gravity.

[Eric]

Thought Experiment: The black hole at the center of the Milky Way instantly disappears.

How long does it take for things to change for our solar system and our planet such that they no longer orbit around the center of the galaxy? How are gravity waves part of the change?

[OngBonga]

While the energy is conserved, mass is not conserved. While the total energy of the resulting photons is equal to the total energy of the initial particles, it is no longer expressed in terms of mass. If no mass, no gravity.

I still can't accept this. I feel like energy is being lost in the form of gravitational potential energy or whatever. I feel like this is a quirk of our limitations on understanding.

idk, once we thought that gravity was a force, carried by a particle, but now we understand it as a consequence of warped spacetime. Maybe the photon plays a similar role... maybe electromagentism isn't a force, maybe it's a consequence and we're just doing it wrong.

It seems logical to me that, if photons are massless but have an energy value, anything emitting photons is losing mass, and therefore gravity.

I feel like if a photon is a particle, then it must have a non-zero mass, just perhaps a mass so small as to be immeasurable. Otherwise, I'm inclined to think the fate of the universe is graviational decay, as matter slowly decays into photons.

Can photons turn into matter? A quick google search seems to imply this is theoretically possible. If two photons collide, then we have an electron and a positron. That's two particles with mass that interact with one another graviationally, created from two particles that apparently don't interact with one another gravitationally.

That "missing" gravity must exist somewhere in some form, imo. Maybe in the case of the photon, gravity is turned into electromagnetism. Maybe our missing "mass" is how we can prove gravity and electromangetism are one and the same.

Well this is a nice start to my sunday. I'm still in bed with a spliff, talking shit about the most complex of subjects. All that's missing is tea...

[OngBonga]

Electromagnetism is just gravity at light speed.

You heard it first from a stoner in England.

[MadMojoMonkey]

Thought Experiment: The black hole at the center of the Milky Way instantly disappears.

How long does it take for things to change for our solar system and our planet such that they no longer orbit around the center of the galaxy? How are gravity waves part of the change?

The solar system, i.e. everything inside the sun's sphere of influence, wouldn't really notice the difference aside from the dramatic changes in the appearance of the Milky Way as it expands and diffuses across the sky. The Earth is orbiting the sun, and so it doesn't really feel the gravity of the galactic center. There will be tidal forces, but at the distance the sun is from the galactic core, those are negligible. I mean, the moon's tidal forces are quite noticeable on Earth, but the tidal forces on Earth due to the sun are difficult to measure.

The sun will cease to orbit the galactic center ~27,000 years after the black hole annihilates, as it is ~27,000 light years from the center and gravity waves propagate at a rate of 1 light year per year (I.e. the speed of light).

Gravity waves are kinda like this:
Think of a trampoline. (Yeah, this again.)
I'm not re-stating all the pros and cons of this thought experiment; be aware that this is just a basic visual aid,

The galactic core is like a huge weight in the center of the trampoline. The weight sags down and sits at the bottom of a very curved pit in the trampoline. This curvature represents the effect of mass on space-time.

For the purposes of this visualization, replace the weight with a taught rope pulling down on the trampoline from the other side.
Then cut the rope.

The trampoline sheet will spring up. The wave of this up-springing will travel out from the center at the speed of sound in the trampoline sheet.

This is like the way the curvature of space-time would respond to the annihilation of mass. It springs back to the state of having no source of curvature. It overshoots that equilibrium position and then experiences a decaying oscillation as it settles down.
This creates ripples moving spherically outward.

I can't help but think of the ripples in a still pond, if I were to throw a rock into it. At first, the rock displaces the surface into a bowl shape, but then it releases that pull. The resulting waves (not of the impact, but of the release) are probably not a terrible way to visualize 3-d waves in 2-d. You just have to remember that space-time is 3-d and these waves are how the space-time stretches and compresses.

[MadMojoMonkey]

@ong: how about this little tidbit:

note: You can scan back to some of the earliest discussions in this thread to brush up on the relativistic gamma factor, but it works like this:
The faster you go, the more space is contracted in front of you, the more time is dilated all around you, and the more force it takes to accelerate you. That last one is known as the increase in relativistic mass.

As an object's speed approaches the speed of light, that object's relativistic gamma factor approaches infinity. Meaning that the amount of force needed to accelerate it AT ALL is approaching infinity. The result is that nothing with mass > 0 could possibly ever be accelerated to the speed of light, as it would require more energy than the universe (or any universe) can produce by any fathomable means.

Furthermore, if anything which has mass > 0 is actually moving at the speed of light, then it has infinite relativistic mass, and would exert infinite gravitational effect on the universe.


If photons have non-0 mass, then they MUST travel at less than the speed of light.
QED

In order to argue that photons do not move at the speed of light in vacuum, then you need to unravel Einstein's GR. GR is widely accepted as the most elegant theory in all of human history. It is entirely built on the most basic and simple assumptions and it gives us so many predictions. Plenty of these predictions were considered absolutely not physical 100 years ago. Yet, 1 by 1, every one of the predictions to be explored has turned out to be an observable physical phenomenon.

This is not to discourage you. It's to tell you where to start on that Nobel Prize you'll earn for getting this right.

[MadMojoMonkey]

I still can't accept this. I feel like energy is being lost in the form of gravitational potential energy or whatever. I feel like this is a quirk of our limitations on understanding.

idk, once we thought that gravity was a force, carried by a particle, but now we understand it as a consequence of warped spacetime. Maybe the photon plays a similar role... maybe electromagentism isn't a force, maybe it's a consequence and we're just doing it wrong.

Of course, this is always possible - expected, even. However, we're at the point of refinement. What we've figured out is demonstrably repeatable, and makes precise predictions.

We're trusting the theories and looking for things that seem impossible, and we're actually seeing those things.
The theories are at least robust enough to trust in this regard. New theories must agree with these theories where they describe the same things. If a new theory says our old data is wrong, then that's a bad sign for the new theory. The data is there.

It seems logical to me that, if photons are massless but have an energy value, anything emitting photons is losing mass, and therefore gravity.

Yes.

I feel like if a photon is a particle, then it must have a non-zero mass, just perhaps a mass so small as to be immeasurable. Otherwise, I'm inclined to think the fate of the universe is graviational decay, as matter slowly decays into photons.

This argument is lost on me. What evidence do you have that this is not the eventual fate of the universe?

Can photons turn into matter? A quick google search seems to imply this is theoretically possible.

Yes.
It's not theoretical. The 1948 Nobel Prize in Physics was awarded for demonstrating pair production.
It is well known and studied.

If two photons collide, then we have an electron and a positron. That's two particles with mass that interact with one another graviationally, created from two particles that apparently don't interact with one another gravitationally.

Well, photons don't really collide. They are Bosons. Bosons tend to pull each other into sharing the same state at the same time. This effectively means that they pass right through each other if they are on a collision course.

A single photon in an electromagnetic field can experience pair production.

The pair production doesn't have to be electron-positron, but it is always particle-antiparticle. All the conservation laws are followed. I.e. conservation of charge means if one of them has +1 charge, then the other must have -1 charge.

Also, the conservation of energy means that the photon which annihilates must have at least some minimum threshold of energy. This minimum threshold is equal to mc^2, where m is the rest mass of the particle-antiparticle pair. Any energy above this threshold is transformed into kinetic energy of the created particles.

The rest mass of an electron or positron is ~0.511 MeV. So any photon with less than (2 x 0.511 MeV = ) 1.02 MeV cannot undergo pair production into an electron-positron pair.

That "missing" gravity must exist somewhere in some form, imo. Maybe in the case of the photon, gravity is turned into electromagnetism. Maybe our missing "mass" is how we can prove gravity and electromangetism are one and the same.

The conservation of mass-energy is stronger than either the conservation of mass or the conservation of energy.

The notion that energy changes forms is not foreign to you. Just get comfortable with the fact that mass is another form of energy. While energy is never created or destroyed, it changes forms all the time. Furthermore, relativity says that the form that energy expresses itself may not even be the same in all reference frames, but the total energy is the same.

Well this is a nice start to my sunday. I'm still in bed with a spliff, talking shit about the most complex of subjects. All that's missing is tea...

I'll hook you up

[OngBonga]

Could you please explain,
Electromagnetism,
In Haiku form, thanks.

[MadMojoMonkey]

Could you please explain,
Electromagnetism,
In Haiku form, thanks.

Gauss and Ampere's Laws
Brought together by Maxwell
Also Lenz's Law

[Eric]

The solar system, i.e. everything inside the sun's sphere of influence, wouldn't really notice the difference aside from the dramatic changes in the appearance of the Milky Way as it expands and diffuses across the sky.

How quickly would the dramatic changes in the appearance of the Milky Way happen?

[MadMojoMonkey]

How quickly would the dramatic changes in the appearance of the Milky Way happen?

You wouldn't see anything for 27,000 years. Same as the time it takes to notice anything at all that is 27,000 light years away.

I've looked into some numbers and I'm now a bit skeptical how dramatic the changes would be. In fact, let me take back all the stuff I said about this earlier. I was comparing it to the "solar system w/o a sun" scenario and that's just no good here.
mass of Milky Way: ~10^12 solar masses
mass of Sagitarius-A: ~4.3(10)^6 solar masses

Sagitarius-A is the name of the suparmassive black hole in the center of the Milky Way. It's only 4 millionths the mass of the Milky way. This is really not even close to our previous discussion. The sun is well over 99% of the total mass of the solar system. Given this, I think most of the objects in the galaxy would remain gravitationally bound to each-other as a galaxy.

The objects bound tightly to the core would likely be flung out, but it seems not very likely that many of them would have escape velocity of the now less massive galaxy. They would have to be quite near escape velocity already.

My current guess as to what we'd actually see in the night sky is that the bulge in the Milky Way toward it's center would become slightly bigger and less bright as the objects orbiting the center would acquire more eliptical orbits as they responded to the change in gravitational potential.

[Eric]

You wouldn't see anything for 27,000 years. Same as the time it takes to notice anything at all that is 27,000 light years away.

Right, I understand that we won't see a change in something that is 27,000 light years away for another 27,000 years. I guess the question should be, how quickly would the changes in the geography of the Milky Way happen? In other words, suppose a given star is 15,000 light years from the center of the Milky Way. Will it start drifting out more then 15,000 light years from the center the very second the black hole disappears or will it take longer for it to lose its gravitational attraction and drift out?

[OngBonga]

Given this, I think most of the objects in the galaxy would remain gravitationally bound to each-other as a galaxy.

I don't, not indefinitely anyway. I just imagine that it will take a very long time for the galaxy to fall apart. But ultimately, I would have thought that SMBH's play a critical role in holding together their respective galaxies. That's a serious distortion of spacetime, even if it is a mere fraction of the overall galaxy mass. It's certainly going to influence anything close to it, which in turn influences anything close to that... the drift will be contagious. 4 millionths of the mass of the galaxy? Yeah, a very long time indeed. But it'll fall apart imo.

Bravo on the haiku.

[OngBonga]

If you took away the SMBH in our galaxy, what is the galaxy rotating around? Nothing? That isn't going to work out well in the long run.

[MadMojoMonkey]

Right, I understand that we won't see a change in something that is 27,000 light years away for another 27,000 years. I guess the question should be, how quickly would the changes in the geography of the Milky Way happen? In other words, suppose a given star is 15,000 light years from the center of the Milky Way. Will it start drifting out more then 15,000 light years from the center the very second the black hole disappears or will it take longer for it to lose its gravitational attraction and drift out?

It will take 15,000 years for it to lose the gravitational attraction.

[MadMojoMonkey]

If you took away the SMBH in our galaxy, what is the galaxy rotating around? Nothing? That isn't going to work out well in the long run.

It'll work out fine.



Things orbit around a center of mass. It is not relevant whether or not there is any mass at that point.

[OngBonga]

But they're still orbitting each other. It's not like they were orbitting something that was where the x is, and now it's gone.

[MadMojoMonkey]

But they're still orbitting each other. It's not like they were orbitting something that was where the x is, and now it's gone.

They're orbiting each other PLUS a thing at x.

That thing at x is many orders of magnitude smaller than the combined center of mass at x.

EDIT: So if you take away the thing at x, you really haven't changed much of anything.

[MadMojoMonkey]

Keep in mind that the stars and gas clouds that are in the galactic core will move about a bit.

I don't disagree that there will be long lasting consequences, but I don't think those consequences will amount to the dispersal of the galactic core. The escape velocity argument is too strong.

[Eric]

It will take 15,000 years for it to lose the gravitational attraction.

Makes sense, thanks for the clarification. Today I re-read a 2003 New Scientist article that reports on the 2002 measurement involving Jupiter:

The speed of gravity has been measured for the first time. The landmark experiment shows that it travels at the speed of light, meaning that Einstein’s general theory of relativity has passed another test with flying colours.


Ed Fomalont of the National Radio Astronomy Observatory in Charlottesville, Virginia, and Sergei Kopeikin of the University of Missouri in Columbia made the measurement, with the help of the planet Jupiter.

[OngBonga]

Pretty sure this is physics.

Why do eggs taste so much better than they smell?

[MadMojoMonkey]

Pretty sure this is physics.

It's mostly psychology, but there's some physics in there, I'd wager.

Why do eggs taste so much better than they smell?

I can't find any documentation on people claiming fresh, uncooked eggs smell.
So... you're just a weirdo.

On the other hand, there is something to say about old (rotten) eggs, which is basically the same as over-cooked (usually over-boiled) eggs.
The rotten egg smell is caused by the breakdown of protein. This can be caused by heating the egg past its standard cooking suggestions, or by bacteria which are small enough to get into the egg through the shell. The protein breaks down into Hydrogen Sulfide and other compounds.

An egg dehydrates through its shell over time. That air sac in the egg is a bit of a litmus test for the egg's freshness. If the air sac is big, that's evidence of a lot of water having leached out of the shell. This takes time, and more time means more opportunity for bacteria to infiltrate. All of this is qualitative, as there is a lot of variance in eggs. Still, for any given egg... larger air sac = older egg.

If all of your eggs stink, you may be over-cooking them, or getting them from a super-market. Try to find a local seller of "pastured" chicken eggs for the freshest eggs. If someone you know keeps chickens, ask if you can buy a few eggs. Cook and eat those eggs right away. I am confident you will taste the difference.

If at that point, you still think eggs smell bad, but taste good, then it's all in your head, man*.

*citation needed

[OngBonga]

I'd much rather be eating fresh eggs from a farm, sadly I live in town centre and it's much more practical to go over the road to the shop and buy them from there. I tend to buy the highest quality free range eggs available... but the options are limited and obviously they're not fresh off the farm.

I don't think I overcook eggs. I boil them for six minutes, ideally I want a solid albumen and a runny yolk. It's just that after I've eaten, I go to wash up, and the kitchen stinks of eggs. It's not actually my breakfast that smells, it's the kitchen. And it never smells nice, even though my eggs always taste great.

I know all about the air sac, I didn't know exactly why (dehydration!) but I certainly don't eat eggs that float.

[OngBonga]

Thing is, with most food items, I can usually tell if I'll like the taste of something based on the smell. Eggs are pretty much the only exception I can think of right now. Oh and cheese.

[Savy]

6 minutes to soft boil and egg? Seems a long time. Is there any chance that the shell continues to cook after it's been taken off the egg? Maybe try putting the egg shell outside to see if that's what the smell is.

Fresh farm eggs also don't really make any difference. Although if you ever get the chance duck eggs are much better than chicken. They taste pretty similar but so much more yolk (i.e. the best bit).

Thing is, with most food items, I can usually tell if I'll like the taste of something based on the smell. Eggs are pretty much the only exception I can think of right now. Oh and cheese.

Fish?

[MadMojoMonkey]

I tend to buy the highest quality free range eggs available... but the options are limited and obviously they're not fresh off the farm.

I hate to bring this up, but there's a few different labels that get put on eggs and they are not synonymous.

Pastured chicken eggs are the gold standard. This means that the chickens live in a pasture (perhaps with a coop to offer protection from predators) and they mostly eat bugs, as they want to do. They are usually given chicken feed to supplement their diet of bugs, but they rarely eat the feed, 'cause they're fat on bugs. These chickens are making what most people consider to be the most tasty and least smelly eggs.

Organic is a meaningless label. Plenty of stuff that is bad for chickens to eat and which affects the flavor of their eggs is under the banner of organic. Ignore it, and generally distrust any company trying to sell you eggs with this emotive, but factless, label.

Free range is also a misnomer. It means the chickens are kept in a warehouse-type farm which has a door out to a 15' x 15' plot which the chickens never use or explore. There is no real way of knowing what they're being fed. That said, if the egg seller isn't bragging about vegetarian-fed chickens, then there's a high likelihood that the chickens are being fed chicken, not to mention plenty of other waste "foods" which are discarded or unusable for other purposes. The food a hen eats has can have a dramatic effect on the smell and flavor of her eggs.

Even the vegetarian fed label is misleading, because the farmer is bragging about not letting the chickens eat bugs, which is what chickens want to eat, after all.

To be clear... I don't care about the living conditions of a beast which has been selectively bread for centuries to be delicious on my plate. A super-market egg is still a delicious food to me. The idea that chickens live in "unnatural conditions" in warehouses is perfectly fine with me. My palate is not refined enough to even be bothered by eating a month-old egg.

What is "natural" anyway? If humans are beings in nature, then the things humans do are natural.


***
Curse you for making me curious about this stuff.

I don't think I overcook eggs. I boil them for six minutes, ideally I want a solid albumen and a runny yolk. It's just that after I've eaten, I go to wash up, and the kitchen stinks of eggs. It's not actually my breakfast that smells, it's the kitchen. And it never smells nice, even though my eggs always taste great.

... dead rat behind the cabinets?

Some other reason your kitchen actually always smells and it's only when you're cooking that the smell seems less repugnant?

Some chemical reaction between your cooking ingredients / utensils and your cleaning products?

You make eggy farts in the kitchen after you've eaten the eggs and you've made a false correlation between the smell and your kitchen?

I certainly don't eat eggs that float.

Use 1 Tbsp of salt per cup of cold water to test this... or so I read on the internet today when I wanted to know what you were talking about with floating eggs.

[MadMojoMonkey]

Thing is, with most food items, I can usually tell if I'll like the taste of something based on the smell. Eggs are pretty much the only exception I can think of right now. Oh and cheese.

This reminds me of my 2 general rules of thumb for choosing the best produce.

1: Choose a fruit/veg which is heavy for its size. You want the most dense one available. This is because the primary thing which contributes to the weight of fruits and veg is the water in them. In general, the more healthy the parent plant, the more efficient it is at growing a fruit/veg. That means that the fruit/veg has higher concentrations of vitamins and minerals and, generally, flavor - which are all indicated by the overall water-weight.

This works for all kinds of produce.

2: Choose a fruit/veg that has a strong smell of what it is... that is, a good orange smells really orangey, a good pepper smells really peppery. A good melon smells really melony, even through the rind.


When in doubt, trust your nose. I.e. trust rule 2 more than rule 1. Maybe I shoulda switched the order.

A farmer's market is simply brilliant to show you what you're missing in regard to delicious onions and garlic. Well worth it, IMO.
Of course, just tell the farmer (so long as they're the seller) when you want to eat the various items you purchase and they'll hook you up with everything reaching its peak flavor on the correct day. So so so worth it.

[OngBonga]

6 minutes to soft boil and egg? Seems a long time. Is there any chance that the shell continues to cook after it's been taken off the egg? Maybe try putting the egg shell outside to see if that's what the smell is.

Fresh farm eggs also don't really make any difference. Although if you ever get the chance duck eggs are much better than chicken. They taste pretty similar but so much more yolk (i.e. the best bit).



Fish?

Duck eggs are great, but they don't sell them across the road. Plus they're more expensive, rarely can I afford premium food.

I'm not a big fan of fish and seafood. I don't mind fish and chips (cod), but that doesn't have a strong smell, at least when cooked.

[OngBonga]

That paragraph about free range and organic stuff really doesn't surprise me. The eggs I buy from across the road are the "happy eggs", they're the most expsensive ones available there and are marketed as free range. The alternative eggs there are cheaper and smaller, less yolk, not as tasty. It's not down to morals that has me eating free range, it's pure taste. I don't have a problem with hens being kept in what we consider to be inhumane conditions... hens thrive as a species because of our taste for eggs and chicken... without humans, hens are fox food.

You make eggy farts in the kitchen after you've eaten the eggs and you've made a false correlation between the smell and your kitchen?

I laughed!

The kitchen only smells of eggs after I've cooked eggs, not after I've cooked bolognese and garlic bread, for example. When I cook that, the kitchen smells fucking great.

[Keith]

I hate to bring this up, but there's a few different labels that get put on eggs and they are not synonymous.

Pastured chicken eggs are the gold standard. This means that the chickens live in a pasture (perhaps with a coop to offer protection from predators) and they mostly eat bugs, as they want to do. They are usually given chicken feed to supplement their diet of bugs, but they rarely eat the feed, 'cause they're fat on bugs. These chickens are making what most people consider to be the most tasty and least smelly eggs.

having difficulty believing that , sounds more like propaganda put out by the animal welfare lobby, given the choice most chickens ill happily easily accessible food .

Organic is a meaningless label. Plenty of stuff that is bad for chickens to eat and which affects the flavor of their eggs is under the banner of organic. Ignore it, and generally distrust any company trying to sell you eggs with this emotive, but factless, label

only difference with organic is that the feedstuffs that they are fed on a predominantly organic , so more likely to have slightly mouldy feed and aflatoxins depressing animal performance , since the organic cereals won't have been sprayed to stop the moulds and fungii growing on the crops.

Free range is also a misnomer. It means the chickens are kept in a warehouse-type farm which has a door out to a 15' x 15' plot which the chickens never use or explore. There is no real way of knowing what they're being fed. That said, if the egg seller isn't bragging about vegetarian-fed chickens, then there's a high likelihood that the chickens are being fed chicken, not to mention plenty of other waste "foods" which are discarded or unusable for other purposes. The food a hen eats has can have a dramatic effect on the smell and flavor of her eggs.

There's a difference between the US and europe here . Meat and bone meal is banned from use in europe in animal feedstuffs as a result of BSE. in fact , feathers from uk chicken slaughterhouses are processed to remove the protein ( rich protein source) and then exported to the US to be used to feed mink.

[OngBonga]

My mate's Dad has a place in the woods, and has chickens, amongst other animals. He feeds them a mix of waste human food, egg shells and spent tea bags. Apparently, the egg shells give them back the essential nutrients they need to make more shell, and the caffiene in the tea bags is good for their metabolism. So he said, anyway. There would have been plenty of bugs around for them too.

I do recall those eggs being fucking fantastic though.

[MadMojoMonkey]

having difficulty believing that , sounds more like propaganda put out by the animal welfare lobby, given the choice most chickens ill happily easily accessible food .

You're probably more right than wrong, here. I'm no expert on any of this stuff.

I did a quick internet search on this to answer ong's questions.

I have no idea how regulated these terms are.

[OngBonga]

You mean you didn't have to study the physiology of eggs (is that the right term?) to get your physics degree?