Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science

Submitted by AutoModerator t3_125oxyo in askscience

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Physics, Astronomy, Earth and Planetary Science

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

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tmoore82 t1_je563ql wrote

Scientists talk about things "warping spacetime," like the way light is "bent" near a large mass--except it's traveling along a curve in spacetime. While that is helpful to visualize, it always leaves in my mind the impression that spacetime is something other masses are on or in, like a stapler inside jello.

But I keep wondering if spacetime is also, for lack of a better word, in everything? Does an atom displace spacetime? Is spacetime between the nucleus and the electrons? Or is it also inside the nucleus?

Maybe a bigger example. Is Earth in but separate from spacetime? Or is spacetime right beside me when I'm sitting in my living room?

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Okonomiyaki_lover t1_je8hhs1 wrote

Spacetime is just the grid we exist on. Every object can have an x, y, z, and time coordinate to describe its location in the universe. While all mass warps space time, very massive objects produce enough warp to be easily seen.

The earth would fly off in a straight line if the sun disappeared. But the sun warps spacetime so the earth orbits this warped part of spacetime.

Spacetime is everywhere (except maybe inside the event horizon of a black hole). Even where matter is. If you had an x/y plane and put a point on it. That point is not separate from the grid.

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tmoore82 t1_jebq2hf wrote

>If you had an x/y plane and put a point on it. That point is not separate from the grid.

This is part of what I'm struggling with. I'm a mass. If it's just me and spacetime, I'm warping spacetime... around me?

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Okonomiyaki_lover t1_jebszo2 wrote

The usual example is like standing on a trampoline or something. You put a dent right under your feet. The further away from you on the trampoline, the flatter the surface becomes. It's pretty much the same but in 3 dimensions instead of 2. You do warp spacetime but you're _very_ small and not very dense so you don't cause any amount of warping that matters.

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tmoore82 t1_jeby4dz wrote

I think that the translation from 2 to 3 dimensions is what gets me. The trampoline example makes sense. But when I try to go 3D, I can only imagine it like a pool, where I'm displacing something else. But another response said that matter doesn't displace spacetime. And you said that a dot on the grid isn't separate from the grid.

I spacetime more like a magnetic field? Defining contours and routes, as well as permeating things that are in its influence?

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Okonomiyaki_lover t1_jec0bbn wrote

Spacetime is the trampoline. The universe is the trampoline. All you do is move through it like you would move over a trampoline.

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mfb- t1_je5b6p6 wrote

> Does an atom displace spacetime?

No.

> Is spacetime between the nucleus and the electrons?

There is space between them, i.e. they have some distance to each other (ignoring some technical details from quantum mechanics). That applies to all times, so you could say that there is "spacetime between them", but I don't think that's a useful way to view it. The same applies to all extended objects, including nuclei.

> Or is spacetime right beside me when I'm sitting in my living room?

Is "beside you" a place? Yes. That's part of space, which is a part of spacetime.

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affablerecluse t1_je5aguz wrote

If I were standing on a giant neodymium magnet the same diameter and mass of the Earth and dropped a rubber ball, would it fall at the same rate as it would on Earth?

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Weed_O_Whirler t1_je66o2j wrote

Mostly.

That strong of a magnet would actually probably magnetize the rubber ball. Every material magnetizes under a strong enough magnetic field, but without knowing the specifics, it would be hard to calculate the effects.

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TitleFlimsy t1_je68ho5 wrote

Would a magnet that size have any impact on the iron in our blood?

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Weed_O_Whirler t1_je6a94c wrote

Oh yeah, a magnet like that would kill you in so many ways, so fast. Of course it would rip the iron out of your blood, but that's child's play in the ways you'd died. Your neurons would become polarized and unable to fire. The cells in your body would all magnetize, ceasing any and all functions. You're toast.

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mfb- t1_je7r7om wrote

A neodymium magnet won't produce a field stronger than 1-2 T. We have MRI machines that are significantly stronger than that, and they don't kill their patients.

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Weed_O_Whirler t1_je8e4g9 wrote

So I'm honestly curious - is 1-2 T the theoretical max for how strong a neodymium magnet can be? Or is there an easy, back of the envelope, way of calculating it? I tried to scale up a small one to the mass of the Earth, but couldn't find any easy way of doing it, but my estimate made it quite large.

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mfb- t1_je8wf3w wrote

Permanent magnets have a saturation magnetization. Trying to apply stronger fields doesn't magnetize the material more, and if you drop the external field then the field of the magnet decreases, too. In practice you get around 1.3 T for neodymium magnets, theoretical values might be slightly higher. This publication calculates 1.32 to 1.38 T.

The size of the magnet doesn't matter, you just scale up everything linearly in space and the field gets larger but not stronger.

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phlpnow t1_je58rmy wrote

How is the distance of stars determined? Clearly you don't have two angles to do this

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mfb- t1_je5caed wrote

> Clearly you don't have two angles to do this

For nearby stars you do. You measure their position in the sky, and then you measure again 6 months later when Earth is on the opposite side of the Sun. Twice the Sun/Earth distance is a short baseline compared to the distance to stars but angle measurements are precise. Stars move relative to the Sun so you need at least three measurements, and in practice you try to get even more to reduce uncertainties.

That method works up to ~10,000 light years or so (with a somewhat lower precision for distances beyond that). For stars farther away you use the cosmic distance ladder, which uses stars with well-known behavior nearby to determine the distance of equivalent stars farther away. Objects next to these can then be used to estimate the distance of even farther objects with the same method.

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Omepas t1_je572q2 wrote

if you cross 2 incredibly long lines next to each other which both rotate clockwise and counterclockwise the point at which they cross increases exponentially. can the crossing point exceed the speed of light? if so does this mean you can essentially send information faster then the speed of light?

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Weed_O_Whirler t1_je5m1in wrote

> can the crossing point exceed the speed of light?

Sure.

> does this mean you can essentially send information faster then the speed of light?

No. While there's no limit to how fast that "point" can move (since that "point" isn't a physical thing, just a concept), there's still a lag between you moving your levers, and the point of crossing moving.

A similar example, that is perhaps easier to understand- if you shine a really bright laser pointer at the moon, and then flick your wrist, you can make the "dot" of the laser pointer move across the surface of the moon as quickly as you want. That dot could move way faster than 'c'. But it doesn't break anything- because there's still the lag you'd expect from the time you pushed the button on the laser pointer, until the dot hit the moon to begin with.

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Omepas t1_je5t7bf wrote

Awesome, still hard to grasp but its been on my mind for like 30 years. the lag thing is still confusing, esp since it doenst mean you will have to send info back, but only forward to someone else. I'll ponder it and try to grasp it.

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Weed_O_Whirler t1_je66wq9 wrote

It helps to think of how you'd actually send information via crossing two long sticks. Any method you actually come up with, will end up taking longer than just shining a light at someone.

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Muhabba t1_je57tyl wrote

Why is the solar system on such a flat plane? Shouldn't it be more of a sphere with the sun in the middle?

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mfb- t1_je5bjqa wrote

That's the natural arrangement of a system with non-zero angular momentum where objects collide with each over time: A disk is the configuration you get after everything not in the disk collided with other particles. Planetary rings are pretty flat for the same reason: Here is a video explaining the concept.

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FlattopMaker t1_je5cjyl wrote

Are there any types of rocks that do not eventually turn into sand?

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CrustalTrudger t1_je5th5x wrote

Sand is just a particular grain size for a material, but for a rock having been broken into sand sized particles reflects that it has experienced a combination of weathering and erosion. No rocks (at the surface) are immune from weathering or erosion, but some minerals that make up rocks are less stable at surface conditions and so will not persist as sediment (sand sized or otherwise) for too long, though when thinking about geologic time, a short time can still be hundreds of thousands to millions of years. Minerals that easily dissolve in water or weak acids (e.g., halite, calcite, etc) or generally tend to react easily at surface conditions and form other minerals (e.g., olivines, pyroxenes, etc) are all components of rock that you wouldn't expect to make up large components of your average sand. But there are definitely exceptions, e.g., sand formed from the weathering of basalts can be predominantly olivine and pyroxene. It's more that all told, these are not particularly stable minerals at the surface so these don't make up much of sand on a global scale.

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Front_Card_2371 t1_je5e5xt wrote

I heard at startalk from Neil Tyson that after fusion of hydrogen it will fuse Helium then carbon etc upto Iron with favourable conditions before becoming supernova( bam). My question is why would the Sun will become red giant? Shouldn’t it shrink in size to continue fusion due to more pressure?

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Weed_O_Whirler t1_je5nsop wrote

The Sun will not supernova, but it will red giant. The reason being as the sun "uses up" it's hydrogen (in reality, it will only fuse about 10% of the hydrogen before transitioning), it will transition to new fusion chains which don't last nearly as long, but create energy significantly faster.

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wolfcede t1_je5n855 wrote

There’s been lots of talk about micro plastics being of measurable quantity in the human body. Do we have a more precise instrument recently for observing these micro plastics or was this known before and just not widely discussed? Is it a new blood test? What’s the instrumentation needed to observe this phenomenon and how accurate is it? Is it possible that plastic is being stored in parts of the body other than blood that we still can’t observe accurately?

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Indemnity4 t1_je89ood wrote

The new blood test is an old test that has been used for environmental monitoring, but not human blood. The neat part of the study was separating the plastics from the blood.

There is no useful measurement for microplastics inside the human body.

For instance, they are mostly inside your gut and lungs. Currently, to measure microplastic exposure involves taking your poop dissolving it and separating out the tiny pieces of plastic from all the food stuff. Not easy to do, but also not very useful information.

We think you have about 100,000 plastic microparticles enter your body everyday. The plastic particles are only about 4% of all the total microparticles per day you are exposed to, the rest mostly being "natural" particles of things like fine sand, dirt, biological materials etc.

When you die, we think about only 1000 will be inside your body. That is from autopsies, so not a lot of information but even order of magnitude it is <<< than your daily microparticle intake. They may be stuck in lesions in your lungs or little blister-things in your gut. Maybe some have crossed the gut to get stuck in some organs. But vast 99.999+% just pass through you like ghosts through a wall.

Everything else - we don't know. We don't know if they are neutral guests along for a ride and doing nothing, if they do anything "good" or anything "bad", if they are correlated with anything. That's an important question: the old prove it doesn't hurt me versus prove it is safe. There are lots of natural things we haven't proved are safe, but we also haven't found anything harmful either.

The conclusion of the linked article is keen to point out that they don't know if the particles are floating in your blood or carried inside cells. They don't know the fate of the particles. They have no way to link blood numbers to any sort of health outcomes or even to ongoing monitoring.

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DeadlyHigh t1_je5wx6a wrote

We all know about the lowest temperature possible, but is there such thing as a maximum temperature possible?

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ffenliv t1_je63gp7 wrote

While waiting for a proper expert to weigh in, I was curious about the same thing some time ago. This Nova piece on 'Absolute Hot' was interesting. Caution: like all things incredibly big or small, it's a tough thing to put perspective to from a human point of view.

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FlattopMaker t1_je5yapj wrote

Is there an efficient and effective way to trap various greenhouse gases in manmade building structures?

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the_geth t1_je6roq1 wrote

The long answer is long, but in short: No.
Google "carbon dioxide capture via air filters" for instance, and you will see that the problem lies in efficiency: You need a huge amount of energy to make a dent into what has been released already, and that energy is likely carbon intensive in the first place.

The scale is insane too: see here how they talk about a hypothetic future plant capturing 1 million ton of CO2 per year. It would still take 32 000 of those hypothetic plants to cancel out the world's CO2 emissions for 2021 (32 billion tons), not accounting for CO2 produced by the construction of those plants and most importantly not accounting for the CO2 produced by the energy needed to capture and store this CO2.
Also, those plants requires chemicals which may be a problem in itself.

It takes about 10Giga joules per ton of CO2 to treat and store the CO2.
So, based on the 32 billion tons of CO2 figure, it would take 320 billion gigajoules to treat all the CO2 emitted by other sources.
That's about ~89 000 terawatt-hours, which is about 3 to 4 times the total consumption of electricity of the entire world in a year.

So... nope.

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atomfullerene t1_je6zurz wrote

I mean, you can build things out of wood, and as long as the wood doesn't rot that represents stored carbon. But you can't solve climate change just with wooden buildings, if that's what you mean.

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Indemnity4 t1_je8bccp wrote

Oh yeah, it's easy. If you have ever seen a gas BBQ bottle or carbonated drink cartridge, it's basically bigger versions of those.

Laughing gas is a potent greenhouse gas, but you can get a cylinder of it in your whipped cream can. A hospital can get a giant tank of it to disperse into regulators for pain relief.

However, if your question related to climate change the answer is no. The scale of the problem is mind boggling huge. You just have to picture every fuel station you see and replacing their storage tanks, but instead now they are filling a new one every few days and simply leaving it in some empty field to hold the gases, forever, with ongoing maintenance.

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FlattopMaker t1_je5yl0c wrote

what is required for mankind to harness and store energy from hurricanes?

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loki130 t1_je6p1zg wrote

I suppose a really robust windmill could do it but it’s just not really practical compared to more consistent energy sources

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Mad_Dizzle t1_jee667q wrote

I guess if you covered the coast in tons of wind turbines, you could capture the energy just fine. The issue with energy sources like wind and solar is storage. These sources are not consistent, so storage devices are needed to contain energy so we can use electricity when the wind isn't blowing. We do not have good enough battery technology to compensate for this, and it would be prohibitively expensive.

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nogoodusernameslft99 t1_je606du wrote

is the Physics they talk about on The big bang theory tv show real Physics, or is it made up?

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quarkengineer532 t1_je7qs2h wrote

Yes and no. There is a lot of real physics. They had physicists check on it. I had colleagues who had their research either talked about or on chalkboards / whiteboards. But things are also no real physics but parodies of it. Like super asymmetry.

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mfb- t1_je7s8lg wrote

It has some connection to real physics. Some parts are made up for the story, but you can clearly see that the writers listened to physicists in many places.

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CivilTowel8457 t1_je610w0 wrote

I am interested in Gravitational physics, Astrophysics, theory of relativity and String theory and i wanna work on one of these topics for my phd. I'm a first year masters student and i wanted to do a project / write a review paper on one of the following to get a head start but I'm confused where to start. Any ideas on specific topics where I can start reading before I decide on a particular topic?

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Redbiertje t1_je92cup wrote

Review papers are typically written by experts in the field (and even usually upon request from a journal), so this is not something you should aim for as a MSc student.

What I can recommend is that you email a few professors at your institute and say that you are orienting yourself for a possible future PhD, and you would like to ask if they have 15 minutes to talk about the current state of their field of research (or maybe they can direct you to one of their postdocs). That way, you get a basic idea about what the main questions are they are working on, and then you can decide which of those you find interesting.

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IamtheBoomstick t1_je64fkp wrote

Would it ever be possible to 'mine' the Sun for Helium?

I've read articles that we are running out, which is worrying as I know that many machines/processes use different forms of helium.

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katinla t1_je6jpna wrote

Considering the extreme temperatures, I'm having a hard time trying to conceive any way of getting even close to the Sun.

If the idea is mining helium from extraterrestrial sources, I'd rather point at the gas giants. You get manageable temperatures and much lower delta-vs (which translates directly into fuel requirements).

But still, this would be an extremely expensive (i.e. unrealistic) mission, not only in terms of money, but also in terms of resources such as materials and fuel. Consider that a round trip to an outer planet does not cost twice as much as sending a probe to stay there, it costs a lot more because fuel requirements grow exponentially with delta-v. This is in addition to the fuel required to lift off from a giant planet.

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loki130 t1_je6nw5i wrote

In principle there are ways to use the sun’s energy to create magnetic fields to lift away some material, but there are far easier ways to get helium

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atomfullerene t1_je70771 wrote

There are some very speculative far future scifi ideas for mining the sun, it's called starlifting.

This is not the sort of thing you'd use to solve a helium shortage, though! It'd be like mining ice from Pluto to chill your drink.

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Indemnity4 t1_je8byp8 wrote

We are running out of cheap, easily available, high-purity commercial helium.

Helium mostly comes from natural gas / fracking. The US gas reserves are naturally rich in helium, which is why they are the largest global producer. It will be something like 1-4% of the gas in a given gas well, but can be up to 10% of the gas well by volume. Before they put it in the pipeline and send natural gas to your house, they separate out all the other gases such as carbon dioxide, oxygen, nitrogen, and helium.

What USA government used to do was require the few giant mega gas producers to separate the helium and send it to a central facility. Now that gas producing regions have relocated and split into multiple smaller units it is no longer financial sense to do the separation and transport.

Unfortunately, helium is still really cheap. It's only $7 cubic meter! It is not worth the cost of running the separator and a bottling plant just for helium. Instead, it gets released to the atmosphere.

Future developments include the price of helium increasing to the point it does make financial sense to separate helium from smaller gas wells. Also, potentially direct helium mining. There are some areas in the world where there are underground caverns full of concentrated helium that could be mined and captured.

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mrxexon t1_je66k7z wrote

Earthquake swarm at Yellowstone this morning. Magma on the move?

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loki130 t1_je6m9dk wrote

Without looking at the specific news, most activity we’ve seen at yellowstone so long as we’ve been monitoring indicate movement of hydrothermal fluids (superheated water mostly), not magma

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Bromaker17 t1_je66rrg wrote

What are the potential implications of supersymmetry for our understanding of string theory? Is it possible to prove supersymmetry?

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Bandersnooty t1_je6bggx wrote

Does quantum entanglement and the apparent lack of time passing between cause and effect indicate the existence of something smaller than quarks (that facilitates a faster than quark speed of reaction)? If not how do theorists explain it?

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Leemour t1_je6sywu wrote

It's just how the wavefunction predicts it. We are unfortunately not able to directly observe the wavefunction, so most statements one is tempted to make about its "true" nature are conjecture.

The quantum bomb experiment is even wonkier and still doesn't prove any "spooky action at a distance".

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mfb- t1_je7sqpn wrote

The speed of light as speed limit for information transfer has nothing to do with the size of particles. You cannot transfer information faster than light, no matter which particles you use and no matter which particles exist, entanglement doesn't change that.

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Bandersnooty t1_je7wp97 wrote

What I'm asking is whether or not it is possible that there is a form of energy so far undiscovered that registers at a quark or subquark level that can travel faster than light.

Light is the current known standard by which to measure speed, but photons are comprised of "bundles" in the electromagnetic field being transferred super fast from one point in the field to another point in the field.

"The field" itself is what I would like to know more about and understand its role in energy transfer.

Quarks are theoretical and considered so bc there isnt concrete physical evidence for them, but if thats the case, its entirely possible that there are even smaller units than quarks that are undetectable due to limits in current technology.

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mfb- t1_je89fs0 wrote

> What I'm asking is whether or not it is possible that there is a form of energy so far undiscovered [...] that can travel faster than light.

That is possible, but it looks very unlikely. And it's not related to entanglement.

> that registers at a quark or subquark level

That part doesn't make sense.

> Light is the current known standard by which to measure speed, but photons are comprised of "bundles" in the electromagnetic field being transferred super fast from one point in the field to another point in the field.

No, the speed of causality is a far more fundamental concept. Light travels at that speed, and we call it "speed of light" for historical reasons, but the speed limit is much more general than light.

> "The field" itself is what I would like to know more about and understand its role in energy transfer.

The electromagnetic field? That's again not a question about entanglement.

> Quarks are theoretical and considered so bc there isnt concrete physical evidence for them

Are you commenting from the 1950s? That's a time where such a statement would have been reasonable. We have studied quarks routinely for decades now.

> its entirely possible that there are even smaller units than quarks that are undetectable due to limits in current technology.

That's unlikely but we cannot fully rule it out. But again, this has nothing to do with anything else in your comment.

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someon332 t1_je6e7r8 wrote

Why can’t anything escape from inside a black hole? I hear that it’s because “escape velocity is equal to the speed of light” but an object dosent have to exceed the escape velocity to escape the objects gravitational pull. I’m wondering if it’s a physics problem (in that some physical law is stopping us) or an engineering problem (in that it’s just difficult to imagine a system that could output enough energy to counteract the pull).

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loki130 t1_je6ndgd wrote

The distortion of spacetime in the black hole is such that it’s geometrically possible to move outwards (or even remain still). It would be like trying to go north from the north pole.

Also the thing about not having to reach escape velocity is only sort of true. If you start near a planet and start moving at less than your current escape velocity, you could indeed escape the planet, but escape velocity drops as you get further from the planet, so you would have to cross that escape velocity at some point.

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someon332 t1_je7polu wrote

Could you expand a bit more on it being “geometrically impossible”? As in, what makes it so? Is it just how the math works out, that standing still or escaping such bent spacetime would require infinite amounts of energy?

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mfb- t1_je7szo5 wrote

It's like trying to reach last Monday. In which direction would you walk? Similarly, avoiding the singularity is as impossible as trying to avoid reaching the next Sunday.

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the_geth t1_je6knrq wrote

About ultra-massive block holes like this one or TON 618 which is even bigger, at 66 billion solar masses:
Since there are so, so big and it would take ages to travel to their centers from the event horizon itself , would it be possible to be inside the event horizon in orbit?
For how long, in theory (I imagine that orbit wouldn't be stable)?
Last but not least, would you be able to see the singularity from there?

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Kyrsatile t1_je8ujy5 wrote

This is kind of both a physics and astronomy set of questions.

In Mass Effect 2, there's a planet called Hagalaz that is described as having a constant lightning storm happening right where the sun is setting where hot and cold air meet. This storm is caused by "the ocean boiling during the day, only to snap freeze 10 minutes after sunset." I understand it’s science fiction, but it’s been driving me crazy.

Here is all of the information about the planet I can find:

Hagalaz has a radius of 6,309 km, a day length of 98.3 Earth Days with an orbital period of 1 Earth year, an atmospheric pressure of 0.83 of Earth, an average surface temperature of 72 °C (day) and −64 °C (night), a surface gravity of 0.69 g, and a mass of 0.67 Earth Masses. It has an orbital distance of 0.95 AU around a star with a stellar mass of 1.01 compared to our sun. It is not specified if Hagalaz’s oceans are salt or fresh water, nor the temperature of the star, though it appears to be roughly half the size of our sun. Hagalaz has a nitrogen-oxygen atmosphere and is apparently a garden world capable of supporting life.

With all of the necessary information about the composition of the planet aside my questions are - would the storm that is supposedly spanning at least most of the circumference of the planet and constantly chasing the sunset even be possible? Would it be possible for water, any water, to boil at 72C and snap freeze in 10 minutes after sundown in these conditions? Would this planet even have any water left?

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napdmitry t1_je95ym2 wrote

What might the energy partitioning be, when the equipartition theorem is not applicable?

Question background. There is an equipartition theorem, and it is without doubt correct. But it has its conditions of applicability, which are not always satisfied. There are well-known examples of a chain of connected oscillators, the spectral density of a black body, the new example of an ideal gas in a round vessel. How may or may not the energy be partitioned in such cases, when the equipartition theorem is not applicable? Can anyone provide more systems with known uneven laws of energy partitioning?

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Flyingtorooftop03 t1_je8ro0l wrote

Is it possible that metal is more attracted to the earth than other material, because of the magnetic field of the earth?

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kompootor t1_jefdd2k wrote

Are you talking about at the time of Earth's formation, as in, early Earth gets a magnetic field, which attracts more iron and nickel to the core as it's forming? That seems unlikely, since the Earth's magnetic field is caused by convection currents of iron around the core, which requires the immense heat and pressure of an entire rocky planet around it to work. (But I don't know.)

Are you instead asking whether metal would be attracted to Earth since after Earth's formation through today? In short, yes. Our magnetic field has components both inward toward the core and parallel to the Earth's surface. On the surface we humans mostly can see the effects of the magnetic field as exerting a force on a compass needle. The needle is very light, carefully balanced, and shielded from the air so that there are as few additional forces involved that could overwhelm or resist that caused by Earth's magnetic field. Also, a compass needle is magnetized so that it aligns correctly and at maximum force with magnetic North. In principle a non-magnetized iron (or other ferromagnetic) needle can also be used in a compass, following recalibration. [See a StackX explanation on this, though the answer appears to be interpreting the necessary energy as that needed to permanently magnetize a needle, as opposed to simply the Zeeman energy, which is a net gain when the sum of alignment directions of its tiny component magnetized crystals with respect the external magnetic field is calculated. Thus as long as resistance in the compass chamber is minimal, the needle should eventually align. Magnetite as lodestone, incompletely magnetized, was used in this way.]

Note that in orbit the magnetic field is only about half as strong as on the surface (where it is already quite weak by human observation standards), and it decreases steeply further out, but low orbit is perhaps the first place where you might first think of a free unmagnetized iron or nickel (a ferromagnetic metal) object being noticeably affected by Earth's magnetic field. There's a lot of subtleties here that I'm sure I'll miss, but let's try a calculation: taking magnetic saturation into account (thanks u/mfb- ), the max magnetization of steel is 2 T, and if we have a 1 m^3 block of steel in space then that's a magnetic dipole moment of 2 A m^2, so with a magnetic field in orbit of 35 * 10^(-6) T, the forces experienced in orbit are at max 7 * 10^(-5) N. Compare this to, say, the total drag forces in orbit, say at ISS orbit at 400 km (p. 14) ~ .001 dynes/cm^2 * 100^2 cm^2 * 10^(-5) N/dyne = 10^(-4) N. So at most, the magnetic forces on this (unrealistically) enormous metal block in orbit would be of comparable magnitude, a bit less, than the not insignificant drag at the ISS, which is more significant than I expected if I took into account everything needed (which is a big "if").

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mfb- t1_jefh2nx wrote

I'm not sure how you got the dipole moment. The uniform component of Earth's magnetic field is only changing the energy of the arrangement, the force comes from the inhomogeneity. As an order of magnitude estimate, the force will be F = B_1 V B_E / (R_E mu_0) with B_1 and B_E being the two magnetic fields, V being the volume of the steel block and R_E being the radius of Earth (as scale of the variation of Earth's magnetic field). mu_0 is the vacuum permeability. Coincidentally, it's comparable to the number you got, 10^(-5) N.

If we don't divide by the radius of Earth we get a (sort of) potential energy, which is tens of joule. Completely negligible compared to hundreds of gigajoule of kinetic energy.

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MrDeltoit t1_je62t4e wrote

On the subject of gravity creation devices as described by Bob Lazar - what's your take on it? Is it theoretically possible? Has anyone in science fiction developed a probable design for such a device?

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Mad_Dizzle t1_jee5l1l wrote

Bob Lazar is a nutcase, and gravity generators aren't possible. It's just not how gravity works.

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