Ask a Physicist!

[Slenn]

1. Graviton
Is it a thing? Has it a been found or is it still stipulation? Where and how would one "presumably" look for it?
If found, would that turn Gravity into a function of emmittence speed/reach?

It's hypothetical. We still don't have a working model for gravity at the subatomic level. Presumably we would find it if we had enough energy that's akin to the beginning of the universe.
"Emmittence"? Do you mean "immediate"? Gravity's influence travels outward at the speed of light, if that's what you're asking.

2. Space Flight vs. Radiation
To my understanding space is mostly filled with EM-radiation and the occasional hydrogen proton per km³. If that is correct, wouldn't moving at ludicrous speeds (say close to lightspeed) by a big risk due to the amount of radiation encountered over distance for radiation absorbent bio mass (i.E. humans)? Also, wouldn't the hydrogen particles encountered at close to lightspeed become a risky kinetic impact?
I have read that basically having a large tank of water in front of the movement direction would be a sufficient/good radiation protection. Would that really work?

Actually, if I remember correctly, there's one hydrogen atom for every 10 cubic cm. But it at large speeds this doesn't hinder spacecraft in any way. A shuttle in space experiences nearly no drag. But once in the atmosphere it experiences a friction burn from reentry and drag upon liftoff. At relativistic speeds, a fusion reaction in space from one hydrogen atom onto the spacecraft's atoms would be negligible since there's no chain reaction to worry about. A hydrogen bomb has a much greater density of hydrogen than the hydrogen in space.

Water is used in nuclear reactors as a neutron absorber. So I can imagine something along those lines could be used.

3. Electricity Generation
It seems to me that most of the major electricity generation is done via pumping heated water through turbines. It seems a bit ludicrous to me that we have to rely on boiling water (via burning fuels, coals, trash or via radioactivity) to spin magnets in coils.
Have there been any rivaling concepts/technologies for electricity generation on that scope and scale?

Wind energy. Which has become more and more common here in the Great Plains of North America.
Hydroelectricity. Depends on if you can find a big enough place with a river to build a dam. They do give off a lot of power. But for places in the desert, there needs to be a better source.

4. Fourth Space Dimension
That one is a big question mark to me. Is it an actual "thing" or just an intellectual crutch or something else?
Ever since I heard of this and saw the rubber-matt animations of spacetime, I kept wandering if our 3d universe is the skin on an expanding 4d sphere. Which would mean that endlessly walking in the same direction, would make you walk in circles on the spheres skin, there'd be a center from which the universe "bang-ed", black hole might actually be "oriented down" to a center, black matter/energy would be effects from the other side of 4d spacial expansion, ....
am I complete of my rocker?

As far as I know, it's only conceptual. Our brains aren't trained to see in an extra physical dimension. There are a lot of things out there in the realm of physics that treat time as a fourth dimension. Where instead of having a position vector with {x,y,z}, we have {ct,x,y,z}, where c is the speed of light.

I'm a little confused by your analogy. You used the words "4D sphere", but then later you said there's a center of this sphere where the universe started. Are you referring to a dimension that encapsulates the universe at different points in time?

 

[AngronIsAngry]

1.Graviton
I meant emittance as in emitting gravitons. I'm sure I heard about gravity affecting at the speed of light, I just didn't have it at the front of my mind. Ty.

2.Space Flighte vs Radiation
I wasn't even thinking about fusion and chain reactions, more along the lines of abrasion; but that seems to thankfully not be a problem. Ty.

3.Electricity Generation
Ty.

4.Fourth Space Dimension
It's no wonder that this gets confusing, as I am myself confused by it.
I guess, analogus to a cube (dot -> line -> square -> cube -> hypercube), there might be a progression
for a round object (dot -> circle -> sphere/ball -> 4D sphere).

Are you saying that a (conceptual) 4d sphere would not have a center?

 

[The Almighty Aardvark]

You have the basic understanding of it. The idea comes from the fact that if you had an electron orbital with two electrons, one has to point up and the other has to point down in terms of spin. (If you want to know more details, I'd be happy to explain the details of fermions and why they must have asymmetric wave functions.) If the electrons across the universe are really that sensitive when it comes to spin, then quantum entanglement proposes you could flip the orientation of one electron and that flips an electron miles away instantaneously. Not at the speed of light. Some people don't particularly like this idea because the electric field that's felt by an electron around one atom is going to be negligible for an electron around another atom. Some other people don't like this for the reason that the information transfer might be instantaneous, which is understandable. That's why it's somewhat of a big deal. Although I haven't heard much in the way of news about it.

Thanks for the response, it clears up quite a bit.

One thing I noticed though, is that you speak about it like it's not a verified occurence. From what I've read on it, I haven't really heard any doubt as to whether it happens or not. Is it not something that's confirmed to happen?

 

[bauke67]

Ahh. Yes, mesons are made of two quarks and baryons are made of 3. They aren't fundamental particles because they can be split further.

And yes, neutrons and protons are baryons, they are the simplest and most stable ones so they are the ones we see most often.

We generally get more exotic mesons and baryons in high energy enviroments only. Places where E=MC^2 can allow energy to become matter. Then, this mass combines to form the particles we see. You can't really separate quarks because the energy required to pull a meson or baryon apart creates new quarks that bond with the separated ones. But you can make new ones that then bind themselves into these two groups.

and no, pretty much everything except for Protons, Neutrons and Electrons decays really rapidly, so rapidly in fact that when it comes to Top quarks and Tau particles and other high mass particles, we can only observe the spray of particles that results from their decay and not the particles themselves. that's why the detectors round particle accelerators are so huge.

As to what are they? They are simply other fundamental particles. They pretty much all follow the same rules except for Strange quarks who have a property called Strangeness that causes them to decay slightly slower than they should (It's still phenomenally fast)

Nope. Mesons and baryons are not elementary particles, and they are made of quarks. What's shown in the graphic are some of the familiar mesons and baryons that are composed of quarks.

Leptons are categorized as having spin 1/2, which means that there are two spin states that they can have (If you want to know more about spin, just ask me). They also have no color charge, which means they don't interact through the strong nuclear force. They do have flavor, which means they interact via the weak nuclear force.

An example of a lepton is an electron, which is found around nearly every atom. The other two, muon and tau, are a bit harder to find unless you're in a laboratory setting. Same goes for the neutrinos, but the fact that they have no electric charge makes them difficult to detect.

If you read the graphic closely, it says that quarks cannot be found by themselves. This is due to the fact that the strong nuclear force demands that sets of quarks must have neutral color. I mentioned color charge earlier. What this is is an abstract label that physicists assign to quarks. A proton will have three quarks, and one of them will be red, another green, and the third is blue. Their total color is white, or neutral. If you had a meson and you tried to pull away the two quarks, the energy needed would end up creating a third quark. I know it's sort of bizarre.

As for meson and baryon decays? It depends, as their decay lengths can vary. J/Psi, which is a charm-anticharm meson, has a pretty small half life that's a tiny fraction of a second. While neutrons are baryons that have a half life of 800 seconds if left alone by themselves (if in an atomic nucleus, the neutrons last indefinitely.)

I hope that does help!

Thanks again! I think I pretty much get all that now. Spin is just how quickly a particle rotates right? And this is at a certain set speed for every particle. What causes neutrons to not decay while they're in an atomic nucleus? Because they can exist in large quantities without many protons or electrons in a neutron star right? Too bad all these particles decay so fast, it'd be awesome to see what sort of larger structures they could combine into.

 

[Batou667]

OP, I would like to challenge you with a riddle.

A monk sets off on a pilgrimage to a temple on top of a mountain. He starts at the foot of the mountain at sunrise and climbs a long, winding and incredibly narrow path all the way to the top. He reaches the summit at sunset, and spends all night meditating. The following morning he starts the descent at sunrise and uses the same route to return to the bottom - but because this time gravity is in his favour, he reaches his destination well before sunset. The question is: what are the chances that he occupied the exact same position on the path at the exact same time on the two consecutive days?

Please take the riddle at face value, i.e. there is no intentionally misleading wordplay at work here, and no withheld information like an elevator or hang-glider being present. There is only one path on the mountain and is so narrow we can assume it is one-dimensional.

 

[retsupurae yahtsee]

I am watching episode 198 of the podcast, which I never watched before, and it said that scientists were able to use a computer system to reattach a crippled nervous system, but that the procedure was illegal in America because of dubious claims of health effects by the F.D.A. How does that work, what do you think of the procedure, its results, the dangers, and do you think it could make the head transplant safer and possible at a higher temperature?

Regarding the nostalgia mentioned in that podcast: Do you have any theories that have existed for many years but have not been been proven or discredited for which your opinion has changed over time, either due to new evidence or your changing perspective as you became more experienced with science?

What part of the Mohr's scale of sci fi hardness do you prefer? I like fantasy in all media except books so I prefer soft science fiction like Star Trek, Star Wars, Philip K. Dick movies, William Gibson stories, Bionic Commando, scrolling shooters like The Guardian Legend, Gun Nac and Gradius; parody science fiction like Hitchhiker's Guide to the Galaxy, Discworld, Rift, Twinbee, Parodius, Beyond Good and Evil and Space Quest; and my only experience with hard sci fi is Arthur C. Clarke. I would think that hard sci fi would be a busman's holiday for a scientist, but Tyson seems to prefer it.

Related to the previous paragraph, do you think that adding too much realism could suck the imagination out of sci fi? I never saw Interstellar, but I loved Inception, except that it went too far in applying real world rules to the dream world and lacked interesting dream imagery. I would have thought the movie was perfect if it did not feel like the creators had Alexythemia.

 

[retsupurae yahtsee]

I know that the reason planets have atmosphere is that they took gas from the sun, thus the outer planets have very thick atmospheres due their high gravity, but why is Mercury in a virtual vacuum despite being so close to the sun? Did it not have enough mass to pull in gas from the sun, or did he radation and heat from the sun cause the gas to dissipate?

 

[Slenn]

4.Fourth Space Dimension
It's no wonder that this gets confusing, as I am myself confused by it.
I guess, analogus to a cube (dot -> line -> square -> cube -> hypercube), there might be a progression
for a round object (dot -> circle -> sphere/ball -> 4D sphere).

Are you saying that a (conceptual) 4d sphere would not have a center?

I wasn't saying that. I was just confused as to why do you define the big bang as the center of the 4D sphere. Could you elaborate on your reasoning behind that?

 

[retsupurae yahtsee]

A more abstract question: Where do you think the line is drawn between curiosity and scientific research? Is science simply looking for answer in the uncertain or unknown; is learning about things that are already known, but which might have new facets the edge of science; or is simply looking for things that are fun but unlikely to lead to any significant discoveries, like when I look through my ROMs for obscure, fun old games a kind of science?

 

[Slenn]

How hard is it to create a Foucault pendulum? Could I place a metronome in a plastic bag and put it on a level surface, or would there still be too many outside factors?

What do you think will be the next big leaps in entertainment and technology in general? Are there any fields that you think have the potential for such development, but receive poor funding and research? Most of the things we take for granted now were unprecedented 150 years ago and there have been a lot of interesting discoveries recently, so I am hopeful that things will develop.

Could anything knock the Earth or the sun out of its orbit? How far could the Earth and the Sun be pulled out of their positions before the Earth became uninhabitable?

It's not that hard. I have no idea what you mean by placing a metronome in a plastic bag. Could you elaborate?

I think that we'll definitely see some improvements in virtual reality and prosthetics. This is based on what I've seen with the popularity of the Occulus Rift and the 3D printers. Maybe something with high temperature superconductors will also come up in the next 50 years.

At this point in time, only an object the size of a planet could substantially deviate Earth's orbit. The largest objects to hit the Earth since its formation aren't even close to moving it by a significant margin. The Earth's orbit varies by 4.8 million kilometers out of its average orbital distance, 150 million kilometers. I would estimate if it varied by 10 million km, that it would make a noticeable change in the climate. This is a good question, but it's only a guess.

 

[Slenn]

Thanks for the response, it clears up quite a bit.

One thing I noticed though, is that you speak about it like it's not a verified occurrence. From what I've read on it, I haven't really heard any doubt as to whether it happens or not. Is it not something that's confirmed to happen?

You're most welcome!

I just haven't seen any particular news on it as of late. There has been research regarding it, but I haven't heard anything in the physics colloquiums I attend. It may just be lack of information flowing.

 

[Slenn]

OP, I would like to challenge you with a riddle.

A monk sets off on a pilgrimage to a temple on top of a mountain. He starts at the foot of the mountain at sunrise and climbs a long, winding and incredibly narrow path all the way to the top. He reaches the summit at sunset, and spends all night meditating. The following morning he starts the descent at sunrise and uses the same route to return to the bottom - but because this time gravity is in his favour, he reaches his destination well before sunset. The question is: what are the chances that he occupied the exact same position on the path at the exact same time on the two consecutive days?

Please take the riddle at face value, i.e. there is no intentionally misleading wordplay at work here, and no withheld information like an elevator or hang-glider being present. There is only one path on the mountain and is so narrow we can assume it is one-dimensional.

My guess is that only at some point in the middle of the path. He will have occupied the same point at the same time of day, but on two different days.

 

[retsupurae yahtsee]

A sealed plastic bag is a vacuum, so that should prevent wind resistance; or would there still be wind resistance?

 

[vallorn]

I know that the reason planets have atmosphere is that they took gas from the sun, thus the outer planets have very thick atmospheres due their high gravity, but why is Mercury in a virtual vacuum despite being so close to the sun? Did it not have enough mass to pull in gas from the sun, or did he radation and heat from the sun cause the gas to dissipate?

Yeah you pretty much got it. What we call the Solar Wind is a stream of high energy particles that are emitted from the sun, they react with our planet's magnetosphere and atmosphere to form the northern and southern lights.

So when you have a really small planet like Mercury so close to the sun, it's gravity can't hold the atmosphere on there in the face of such an intense wind of particles that just strip the atmosphere away a bit at a time. That's not the case for outer planets like Pluto where the atmosphere just freezes anyway.

 

[Slenn]

I am watching episode 198 of the podcast, which I never watched before, and it said that scientists were able to use a computer system to reattach a crippled nervous system, but that the procedure was illegal in America because of dubious claims of health effects by the F.D.A. How does that work, what do you think of the procedure, its results, the dangers, and do you think it could make the head transplant safer and possible at a higher temperature?

What podcast are you talking about? I can't tell you how I think it works unless you give me more specifics. What part of the nervous system are you talking about?

Regarding the nostalgia mentioned in that podcast: Do you have any theories that have existed for many years but have not been been proven or discredited for which your opinion has changed over time, either due to new evidence or your changing perspective as you became more experienced with science?

Sure, plenty of times. The list is too long though. That's not being lazy, it's just a fact of science. Science is a self correcting process, and I'm always learning new things.

What part of the Mohr's scale of sci fi hardness do you prefer? I like fantasy in all media except books so I prefer soft science fiction like Star Trek, Star Wars, Philip K. Dick movies, William Gibson stories, Bionic Commando, scrolling shooters like The Guardian Legend, Gun Nac and Gradius; parody science fiction like Hitchhiker's Guide to the Galaxy, Discworld, Rift, Twinbee, Parodius, Beyond Good and Evil and Space Quest; and my only experience with hard sci fi is Arthur C. Clarke. I would think that hard sci fi would be a busman's holiday for a scientist, but Tyson seems to prefer it.

I really like the Foundation series by Isaac Asimov. He is my favorite.

Related to the previous paragraph, do you think that adding too much realism could suck the imagination out of sci fi? I never saw Interstellar, but I loved Inception, except that it went too far in applying real world rules to the dream world and lacked interesting dream imagery. I would have thought the movie was perfect if it did not feel like the creators had Alexythemia.

I don't really think it does. Because you shouldn't expect people to not think about the movies they're watching. Sci fi can be imaginative and still be realistic. The whole point of sci fi is to deliver a "what if" scenario to the audience. The book, I Robot, was really good at it and so was Prelude to Foundation. The Terminator movie was really good, as was its sequel. It was explosive, but it wasn't mindless action. It was a really nice scenario with robots.

A sealed plastic bag is a vacuum, so that should prevent wind resistance; or would there still be wind resistance?

A metronome wouldn't work with or without the bag because the pendulum is fixed so that it can only swing in one direction. You need a heavy ball attached to a string and fixed to a ceiling. The string allows the pendulum to swing wherever it wants. Since the Earth is rotating, the pendulum will move gradually in a circle. If you line 24 nails in equal spacings in a circle around the pendulum, it will knock one nail down each hour.

 

[retsupurae yahtsee]

I mean episode 198 of the Escapist podcast.

 

[freaper]

As a physicist, what do you find the most effective way of activating your chakras?

 

[Slenn]

I mean episode 198 of the Escapist podcast.

You still need to specify what part of the nervous system was worked on. It's lots of parts. Was it part of the brain? The spinal column?

As a physicist, what do you find the most effective way of activating your chakras?

You mean metaphorically or literally?

 

[retsupurae yahtsee]

It said that the treatment was used on someone whose legs and brain were poorly connected.

 

[Dalisclock]

Do you play Kerbal Space Program or are you familiar with it? If so, do you feel it's reasonably accurate as far as flight physics are concerned?

On the other side of the coin, does the use of Quantum Physics and Time Travel as a substitute for magic in some sci-fi stories, such as Bioshock: Infinite, annoy you? Or in situations like that do you just roll with it and judge the work on it's other merits?

I worked with Nuclear Power for several years and got my degree in it, so some depictions of Nuclear Power/Reactors/Weapons annoy me and others I'll let slide depending on how much I like the work overall.