1

Physics, Astronomy & Cosmology / Re: How can we identify parallel universes?

« on: Yesterday at 17:43:31 »

Firstly, we haven't got any hard evidence for parallel universe(s), just some theories that involve them.

Tegmark enumerated four different 'levels' of multiverse. Only one of them might be described as 'parallel', which is, yes, MWI. For instance, the first level is other visible-universes which are 'elsewhere', not 'parallel'.

Mukal seems to be imagining a sort of literal interpretation of the Newtonian rubber-sheet analogy, which is a model of curved space, but not of spacetime at all.

Firstly, this entire concept of spacetime as some sort of fabric is intended only as a visualisation of what is happening and it's nothing more than that.

Yes. It is a cheap visualization of bent space, but not of bent spacetime since time is not represented.
The idea of a universe on the other side of it seems motivated by fictional descriptions of the 'upside down' in popular, if not scientifically sound, television series.

So a hill would presumably be some area or region that repels ordinary matter or opposes conventional gravity.
    We haven't found a region of space where matter is obviously repelled from that point of space.

We have!
The Dipole Repeller and Cold-spot Repeller are two such 'hills' which repel all matter (galaxies) near them.

This can actually be modeled with the rubber sheet. Given an infinite sheet will balls distributed perfectly evenly over it, none of the balls will be attracted in any particular direction. Take one ball away and all the ones nearby will be repelled from the 'hill' that forms in its absence.

However space is big and there would always be problems determining if something was repelled from one region or if it had just been attracted to some other region.

Same thing, literally.  Gravitational attraction one way can always be spun as an absence of as much attraction in the other direction.
Is wind attracted to the eye of a hurricane, or is it just pushed there from outside?  The push is always there, but the eye is not, and the fierce wind results only from the eye, the absence of pressure.

2

New Theories / Re: Do rocket engines violate the equivalence principle?

« on: 28/11/2021 17:35:08 »

I can't think of any propulsion system that doesn't consume fuel of some sort, and conserve momentum.

If you can define a closed system, then yes, the momentum of that system will be conserved. Most rockets are not considered closed systems.

The definition of a fool is someone who doesn't understand newtonian physics.  If you are burning fuel, you must be producing thrust, so you must be accelerating

Alan, what is your purpose in obfuscating the physics of the equivalence principle? This [was] a mainstream thread and you're pushing very wrong physics in it. Newtonian physics does not conclude that thrust must result from the consumption of fuel, as BC has pointed out.
This is a thread about the EP, and to be equivalent, you must compare apples to apples, and your comparison of apples to oranges only serves to obfuscate. If you want to compare a rocket in space consuming fuel to accelerate at a constant proper 1G, then you need to compare it equivalently. So if you want to compare to a rocket in a vacuum at the surface of Earth consuming fuel to accelerate at a constant proper 1G. The one on Earth will not undergo any coordinate acceleration (as measured by a distant inertial observer) and the occupants of both rockets will be unable to tell via any local test which is which.

I said this as much in my first reply to you, which I notice you ignored. Why do your posts belong here? Why shouldn't I move all this nonsense to the lighter side?

BC, you're allowing yourself to be led by the nose by Alan. Your post about certain vehicles with propulsion at one end or the other is entirely irrelevant to the equivalence principle. If you want to take apart Alan's assertions, keep it to the parts that are relevant to the topic.

3

Physics, Astronomy & Cosmology / Re: Cosmic inflation, before or after the big bang?

« on: 25/11/2021 14:14:55 »

Is it now agreed that cosmic inflation occurred before the big bang and if so does it make a big difference to our original understanding that inflation occurred after the big bang?

From what I can tell, there is but the one mainstream model which is not ambiguous on the ordering of the epochs. The only difference is semantic: which exact moment in time (before inflation, and how much before, or after it) to assign the label 'Big Bang'.
It is legitimately questionable since time as we know it, measured in seconds and such, isn't really a meaningful measure when describing the inflation epoch. Hence the reluctance to assign 'time zero' to the point at which things were most compact.

4

Physics, Astronomy & Cosmology / Re: The equivalence principle and experiments concerning it?

« on: 24/11/2021 17:03:27 »

But if we wait long enough experiencing constant 1 g, can't we be sure that we are not linearly accelerating in free space because we would exceed the speed of light?

Proper acceleration (which is the 1g being felt by your guy) measures the rate of change in rapidity, not in velocity.  Rapidity is not limited by c, which is why I can get to Betelgeuse before I die if I go fast enough, despite it being over 600 light years away.

Acceleration (as opposed to proper acceleration) is frame dependent measures the rate of change in velocity. Velocity (relative to a given inertial frame) cannot exceed c, and thus acceleration is limited in frames where the velocity is already near c.

Assume a rocket with a very large but finite amount of fuel, accelerating at 1g. The occupant feels as though he is standing on a planet, but knows he is accelerating because his fuel gauge is decreasing.

Ah, but the same guy hovering with his rocket a meter above Earth is also watching his fuel gauge decreasing. Both measure the same thing if they're equivalently set up.

5

Physics, Astronomy & Cosmology / Re: How long does a gravitational wave last?

« on: 24/11/2021 03:25:56 »

I am still  wondering if we can still say  that these very asymmetric  "rings" carry away their  energy without  any loss of power at all  as they encounter obstacles in their path.

A spiral is still symmetric, just not spherically symmetric.
By time-symmetry, if matter (say a binary star) can emit gravitational waves and lose energy in doing so, then such a system can hypothetically absorb them, gaining energy in the process, but the passing wave is not going to be focused in such a way that any measurable effect will occur. It would have to look like the time-reversed wave spiraling in, which isn't how it looks when it was emitted from afar.

So would a neutron star or another black hole absorb their energy?

A lone mass like a  neutron star which seems no more capable of absorbing them as emitting them. Any mass will however deflect the waves, breaking the symmetry like water waves crossing a shallow spot. A black hole must absorb the energy as there is no worldline through them. They're also the only things that absorb dark matter.

Or does the gravitational wave go through these objects as if they were not there?

Like dark matter, it goes through them like they were transparent, but still deflected by the gravity.

6

Physics, Astronomy & Cosmology / Re: Clarification of time dilation please

« on: 24/11/2021 01:05:29 »

I start by synchronising three identical atomic clocks in my sitting room.

Just saying, a clock is a clock, atomic or otherwise. Atomic clocks have the accuracy needed for some experiments, but relativity affects paint peeling just as much as it does any other clock. We assume they all measure time, and you don't need an atomic clock to show that one twin measured half the time of the other.

Relative to me sitting at home at ground level watching TV and keeping my eye on my super accurate atomic clock, I know that other clocks at a lower altitude than mine run slower than mine because the Earth’s gravitational field is stronger at lower altitudes than me, and conversely, those clocks at the top of a tower block run quicker than mine because the gravitational field (acceleration field) is not as strong as it is for me.

It is not the acceleration field that causes this, but rather the gravitational potential field. The rate at which clocks run is a function of potential, not acceleration, so a clock on the surface of Mercury will run much slower than one of the surface of Earth despite you weighing less (lower acceleration field) there.

From now on the thought experiment and discussion is done at precisely the same gravitational field, or the results are modified appropriately to rule out the effects of any different gravitational fields.

That would mean there's no significant gravity at all, yielding flat Minkowski spacetime.

Any acceleration, either speeding up or slowing down, causes the atomic clock undergoing this activity to slow down relative to my own in my sitting room.

No. I can put one clock in a parked car on the equator of Earth and another one accelerating furiously at a linear velocity of 1600 km/hr in some centrifuge at the pole. The one at the pole would accelerate thousands of times as much the one sitting in the parking lot, but when brought together they will still read the same time.  Acceleration doesn't directly cause time dilation. Both clocks are moving at the same speed relative to the inertial frame of Earth and are at the same potential, so they'll not run at different rates.

Here is my problem:-
Now I’ve heard from two authoritative sources, Dr. Pamala Gay (Universe Today podcast Astrocast) and Dr. Daniel Whiteson (Daniel and Jorge Explain the Universe)  that the only occasion when velocity can induce time dilation is when the clock accelerates or decelerates.

Very poorly worded. For one thing, there is no 'decelerate' in physics. It's all acceleration, which is defined in physics as a vector change in velocity. They seem to be using the common language definition where acceleration is a scalar increase in speed relative to an implied frame, and deceleration being a decrease in speed.

One clock X moving relative to another clock Y will be dilated (slower) in the frame of Y. No acceleration is required. Acceleration of one or both is only required to separate them and then bring them back together again.

Both of these will cause time dilation, slowing relative to my clock, regardless of the direction of the acceleration.

This is wrong, as illustrated by example with the centrifuge at the pole.

But for years it’s been drilled into me that a clock in a spaceship travelling at relativistic velocities relative to me at home, undergoes time dilation.  We have all read that if Alice and Bob are twins and Alice goes on a 10 year high speed space trip when she comes back the Earth Bob is many years older than Alice.

So far so good.

So is this age difference due solely to the four periods of acceleration (speed up, slow down, turn around, speed up, slow down) that Alice underwent?

No, because I can do that same series of acceleration without the dilation. There are many 'correct' answers to what exactly causes the dilation, but the primary one (and probably least helpful) is that Alice's worldline between the departure and reunion events has a shorter temporal length than does Bob's.
A more helpful explanation is that relative to any one inertial frame, Alice usually is moving faster and is more dilated.
It can be explained by relativity of simultaneity (something that should never be overlooked), or by moment-of-acceleration which is acceleration time distance, sort of like torque.

If Pamala and Daniel are correct, it doesn’t matter how long Alice was away from Earth, only her four periods of acceleration or in other words the top velocity she achieved, not how long she coasted before slowing down.

They'd be wrong about that. Alice isn't going to be 5 years younger if she does those same accelerations but only goes to Pluto and back.

Let’s take triplets. Triplet A stays on Earth.   Triple B and C accelerate close to the speed of light

This suggests absolute speeds. Velocity is relative, and so you must specify 'close to the speed of light relative to frame X. The statement is meaningless without it. I'm moving at close to the speed of light relative to some frames right now and it doesn't bother me at all.

over a period of one hour

Again ambiguous without specifying the frame in which this hour is measured. I'm guessing B's proper time here: as measured by B's watch. The description below implies that.

Upon return to Earth, Triple B reads his atomic clock and it reads start time plus 4 hours as expected.   Triple A, reads triple B’s clock and let’s say he reads 10 hours have passed (or whatever you like but it’s more than 4 hours).

If both of them are in each other's presence and looking at the same (B's) clock, then they're not going to read different values. Both A and B read 4 hours on B's clock. A's clock will read more, and they both can read that as well.

The clocks are different because of the acceleration undertaken by triple B.

Not because of that, no. The acceleration is only necessary because without it, B would not have come back to A's presence.

Triple C takes off at exactly the same time as triplet B, accelerates for one hour but instead of immediately decelerating, he decides to turn off the engine and just cruises.   After 20 hours, triple C decelerates, turns round, accelerates over and hour then cruses for 20 hrs, then decelerates over a period of an hour and he is then back on Earth.

So triplet C sees that the following time has passed, 4 hours for acceleration and deceleration, plus 40 hours for the two cruise periods.  44 hours in total.

OK.

Triple A reads the clock of triplet C and reads 10 hours (the same as triple B for the acceleration and deceleration period) PLUS 40 hours (covering the two cruise periods) =50 hours.

No, he reads 44 hours. They're looking at the same clock. They can't see different times.

I believe you said that

Who said? This was your first post ever. Nobody has said anything to you except perhaps Pam and Dan above whom you don't appear to be addressing.

during the cruise period of triple C, time for A and C run at the same rate. Is this correct?

The time rate for any particular clock is frame dependent, and none was specified, so the question is ambiguous. Relative to the inertial frame of either A or C, it’s the other one that’s moving and thus the other clock that runs slow.

Until just recently I’ve always heard that the longer people are travelling at relativistic speeds, the more the time difference mounts up when they return to Earth.

Until recently then, you had it right.

But from what you said, that is not true.

You seem to be replying to a comment made by somebody selling you nonsense.

Daniel said this :-
‘ When you bring everyone back to Earth so they have the same velocity, the only thing that matters then is how much acceleration they have experienced. So B and C will be the same age relative to A because they've had the same acceleration.’

Totally wrong. Daniel doesn’t know his stuff at all. Anybody can put out a podcast. It doesn't make them right.

I posed another question about GPS orbiting satellites to examine this further.  I said that I’ve heard it said that the high altitude of the clocks makes GPS clocks run faster (less gravitational acceleration)  but their speed slows them down so although they do run faster than clocks on Earth, they don’t run as fast as one would expect if only altitude was taken into account.   So this means that their ongoing high speed relative to me on the ground does cause an ongoing time dilation effect and it’s not just the initial launch of the satellites that caused an initial offset.

All correct. The launch has almost zero effect. They’re so high up that the dilation (slowing) due to their slow orbital speed is far less than the speedup from the gravitational potential difference, as you described.

Daniel said that while the two clocks, one on Earth and the other orbiting, are at different velocities it’s a symmetric system and it’s only when the travelling clocks come back to Earth that a proper analysis can take place.

No, there’s plenty of ways to do a proper analysis of their rates while still in orbit since they return to the same relative separations at regular intervals.

So I’m puzzling the following.  Is it the case that while the GPS satellite is orbiting and its radioing its clock’s time down the Earth, that Earth sees an ongoing velocity discrepancy accruing (we are not talking altitude dilation but speed only), that should the satellite be captured and brought back to NASA for analysis, that the GPS clock shows an offset due to the time spent at altitude, plus the launch acceleration and recovery deceleration phase only but not the 20 years of accrued dilation caused by the speed.   Isn’t that a lot of accrued time to loose on the homeward journey?

No latent accrual will take place on this journey of far less than a light second. Daniel is telling you more nonsense I see.

So on the one hand I’m being told that cruising at high speed doesn’t cause time dilation and on the other that it does.

Speed is frame dependent, so I’d reword it as: “Cruising at high speed relative to a given inertial frame causes time dilation relative to that same frame.

Gravitational dilation is less frame dependent. Two clocks at different potentials will objectively run at different rates, all else being equal.

Hope this helps.

7

Physics, Astronomy & Cosmology / Re: How long does a gravitational wave last?

« on: 23/11/2021 15:59:29 »

LIGO has a frequency range to which it is sensitive, about 10 hz to 10k hz, no so different from the range of sound detectable by people. So if the massive objects orbit slower than a 5th of a second, LIGO isn't going to pick it up. Near the merger, the frequency rises very rapidly, resulting the characteristic 'chirp', after which the signal is no longer detectable.
It apparently takes under a second for an orbit to drop from a 5th of a second down to at least the photon-sphere, after which the wave signal fades away.


The waves do 'last forever' in the sense that they keep traveling past Earth out forever, always getting weaker by distance per the inverse square law.

8

Physiology & Medicine / Re: Do memories exist after death?

« on: 17/11/2021 21:50:00 »

The color of my eyes, my skin tone & possibly the nose that sits on my face...All bear resemblance to my Ancestors.

Can these things be also classified as Memory?

It's classified as information. All memory is information, but if you classify all information as memory, then there seems to be no point to having two distinct words to describe the same thing. So it seems that memory is a specific kind of information, and whether a seed constitutes memory or not depends on where you draw the line between your definitions.

So again, a dead person's memories might be gone, but the information possibly isn't, at least not right away. But there seems to be no simple way to read this information, just as you can't easily tell from a DNA molecule what sort of thing is described by it. A good biologist can get pretty close though, at least if it's something related to a life form that he's worked with before.

9

The Environment / Re: Is Rising CO2 level a Problem?

« on: 16/11/2021 22:09:03 »

yaa once in a while, a troll does accidentally say stuff that ends up making logical sense.

Maybe not accidentally. Some of the most effective trolls do their work with completely valid logic.

I have never ever observed MODS disagreeing among themselves publicly.

You need to read posts more often. I correct other mods about as often as they correct me. None of us is always right. Maybe Janus, but he's not a mod, and yes, I've disagreed with Janus once in a while.

Mods should probably have a MOD Room, where only Mods can hangout.
Y'all could discuss All you wished in private & come to satisfactory conclusions.

There is one, but I've not ever seen it used to discuss science or present a unified front on scientific topics. We discuss Y'all there. Every forum/chat site has such a room if there's more than one mod.

United You Stand...Divided...it's anyone's guess.

Some of the biggest advances in science has been from those breaking new ground, not staying united with the crowd. So united we stand, divided we advance (or retreat if you don't know where you're going). But nobody with a new revolutionary breakthrough publishes it first on a forum. So those that claim such things here are invariably mistaken, pretty much by definition.

10

The Environment / Re: Is Rising CO2 level a Problem?

« on: 16/11/2021 14:12:24 »

I seem to have missed your excellent point

I seem to remember just asking a question and not so much making a point, excellent or otherwise. But you answered it with "outcome for humanity", something not specified in your topic.

I suspect that the "best" outcome for humanity will be the one in which our environment changes the slowest.

OK, I can buy that, but the way to change it most slowly is to stop changing it. Whether that would be a good thing for humanity I think depends on one's vision of future humanity living in a sustainable manner. Assuming we've not totally poisoned the environment with radiation and such, do you see a low-tech life (essentially living like people did before the bronze age) or a high-tech one where there's still knowledge, internet, and industry and (importantly) globally enforced peace, without which the low-tech future is inevitable.
There are other alternative futures such as one where humanity very rapidly evolves to the new state of things, but that would probably drive the extinction levels to well above 85%.

There is plenty of room for debate on what the exact trade off is between our present economy and our future economy (often called the discount rate — ie "ok, putting carbon dioxide into the atmosphere is bad, but if we can make enough money now by doing it, we may be in a better position to pay for solutions later.")

People, countries, and corporations rarely willingly part with money to benefit a vision of the future. It is actually probably the economy, based on growth, debt, and limited resources, which will cause the population to abruptly fall to a fraction of its levels. Global warming may or may not be the straw that breaks that camel's back, but the back must inevitably be broken, and the state of the environment at that time probably will be a significant factor in the survivability of those that remain. Hence the importance of preservation of the environment, because it's those people that are 'humanity', and not the ones with the money.

I bring this up because people, by nature, have almost zero interest in this group of people. Our morals are based on completely different goals. The moral code pushed by the religions seem designed to force God's hand, to maximize the calamity and thus force the prophesied end-times. It would be considered a completely immoral act to take actions 'for humanity' as outlined above.
And that brings me to the point I meant to spell out in the other thread: This is the lack of actual solutions from both scientists and leaders today. Viable solutions are considered immoral, so with hands thus tied, humanity is actually incapable of acting for its own benefit. If there's aliens watching us, waiting for us to mature before being invited into the 'federation of planets' so to speak, then it's probably this level of maturity that they're waiting for, and are unlikely to see.

The other problem is that so much of the damage has already been done, that we may feel like we are "in for a penny, in for a dollar"

Yes, the damage has long since passed the point of irreversability. Sure, the climate might eventually return to something resembling what it was like around 1900, but it might take hundreds of millions of years. No creature evolved for 1900's climate will be around then, still waiting for it to be nice outside. That's not how evolution works. Evolution will indeed fix this 'problem', as it has all the others.

11

The Environment / Re: Is Rising CO2 level a Problem?

« on: 16/11/2021 13:07:29 »

I have a humble Request, let's Please not make this personal.
Let's Please just stick to facts & evidences.

Careful. Most of your post was personal, which I shall try to ignore.

Reverting back to the Topic...

1) Rising CO2 feeds the loop...
Making drastic changes in weather patterns.

Rising CO2 raises global temperature. There's not much loop to that. Methane is something else. It also has that effect, and rising methane causes more methane to be released into the atmosphere, which is a feedback loop of sorts.

But climate anywhich ways is Unpredictable, Right?

Long term climate is very predictable. We know the oceans are heating up and that there will be more hurricanes and more severe ones. We can predict that this area will receive less rain than it used to, and this other area will get more. These cities (or whole countries like my ancestral one) will have to be abandoned.
What is unpredictable about the weather is exactly which days the storms will hit, but it is the average that matters here, not the specific schedule of the weather.

2) Would people in North Americas or specifically in the E.U. mind or dislike warmer climate?

It will disrupt the food supply for one thing. The extinctions will destroy the ecosystem upon which we depend. Bees in particular are a critical part of the process and are very much threatened by global warming.

i feel it's not the kind words the plants are reciprocating to, rather it's the CO2!

Plants do like it. I imagine that once the people go extinct, the plants will probably come back at a level not seen in millions of years. The oceans are another story. Something needs to replace the coral reefs which are too fragile to withstand a significant temperature change. But nature will find a way to fill the vacancy.

12

Physiology & Medicine / Re: Do memories exist after death?

« on: 15/11/2021 19:43:42 »

So, the answer to the op comes back to how we define death.

This definition seems to change over time. It usually means 'non-functional beyond the point of healing', which changes as technology improves to the point of reviving somebody who would previously have been considered dead.

The problem can be resolved if we can find a way to make someone die without causing oxygen deprivation.

Can you think of one? I mean, doctors are known for saying that actual cause of death is never from heart failure, drowning, cancer, or whatever. It's always lack of oxygen to the brain that finishes you off. This of course isn't strictly true. A grenade going off by your head will surely kill you before the oxygen deprivation even begins, but it isn't going to leave the memories intact.

If it requires irreversible destruction of  someone's memory, then the answer would be no.

But per my prior post, is the destruction irreversable? The guy has lost them, but is it lost to somebody doing a scan? It's not like anybody can look at the scan data (even of a live person) and know what his memories are/were. How might one glean memories from such data, scanned from a person dead enough that they're gone to him.

13

General Science / Re: Matter is Apparently Made of Fields, But How the Heck does that Work?!

« on: 15/11/2021 19:10:15 »

Ok so, around two-ish months ago, I was told by a Cosmologist that what we perceive as matter doesn't actually exist and that the alleged particles that we think it's comprised of are actually "Excitations of fields intrinsic to the universe."

It means that fundamentally, matter isn't the stuff with classic properties that we might find intuitive.
Note that matter is made of 'excitations', not made of 'fields' which the title suggests.

Where are these fields even located anyway?

Colin2B gives a good reply to this reference to fields as existing objects, which doesn't work.

Did these fields always exist

A field doesn't seem meaningful outside the context of what is our spacetime. As to 'always', um... there is not a time in which say one could not meaningfully express a measurement of a particular field. This is debatable. Just after the big bang (well under one second), the 'fundamental forces' had not yet separated into those that we know today, and thus their fields may not have been meaningfully distinct at the time.

Are there fields for antiparticles as well as regular particles?

I'm not sure of this. I had understood that a particle and its antiparticle are different excitations of the same field, but it could also be that they're separate fields with symmetric properties.

Does Dark Matter get its own field as well?

Jury out. There's no viable theory of the nature of dark matter at this point. It seems to affect spacetime, which involves gravitations fields, but it seems to not involve other known fields nor even new ones since except gravitationally, it seems not to interact with itself in any way.

What about Atoms and Molecules? Where do they fit in all of this?

Same as people. They're complex things composed of simpler things. They ride the line of classic physics.

Seriously, I cannot stress how much this single statement destroyed everything I thought I previously knew about matter and the sub-atomic world.

Why? What did you 'know' before? The nice classic model of atoms made of nice colored balls with orbiting electrons? That went out the window quite some time ago.
Even the model above (excitations in fields) is more classic than is suspected. It suggests that the field is always in some objective state, however much known or not. This is probably not the case, but some suggest that it is, preferring to abandon rules like cause preceding effect, which I personally find distasteful.

Soooo... fields, as I've described them in my question don't actually exist and are just an easy way to describe how something in the physical world works and behaves?

We measure their values, so that's existence in my book. I suppose it depends on your definition of 'exists'. A field usually cannot be measured directly. Only excitations (differences in the fields at different events) can be meausred. For instance, I cannot measure the gravitational potential of Earth at sea level, but I can measure the change in that potential between sea level and 100 meters up.

14

Physiology & Medicine / Re: Do memories exist after death?

« on: 14/11/2021 16:58:53 »

In biological brain, it's mostly about connections between neurons.

Possibly, especially in the hippocampus, which is sort of short term memory. The synapses need to be further strengthened by immediate exercise of the pathways. In this manner it would seem that important things might be remembered later on, and unimportant things promptly forgotten.
Long term memory has to work in at least a somewhat different manner, because it needs to be more non-volatile as you put it. Some childhood memory may not have been accessed in decades, yet it is in there, more firmly even than more recent memories, as evidenced by Alzheimer patients who steadily forget their lives in reverse order, with the oldest memories being the last to go.

The connections, or rather the information contained in the strength of those connections, seems to vanish before actual death, as evidenced by memory loss from people revived from oxygen deprivation. This is evidence, but not hard evidence, that memories become irretrievable before death occurs, at least by the subject. Perhaps a hypothetical molecular scan might still find vestiges of the state of those failed connections despite their lack of functionality to the damaged brain. Information in theory cannot be destroyed, so past state can be constructed in principle.
I don't think Heisenberg's uncertainty prevents a scan of a person. You don't much care about momentum or exact quantum state of anything, just sufficiently detailed state at a given moment. And molecular detail is probably an overkill, but a scan down to the cellular level is not enough.

So now you have state of a dead being, complete with probable description of connections that might have been not too long ago. Nobody can read that, so you need to somehow print that state on a brain that's in a different (live) state, sort of like transferring an odometer reading from a crashed car onto a replacement model built with all the wear and tear of the car just before the crash. It's a poor analogy because a car isn't something that can be dead. Only damaged. One presumes that an undamaged biological being would be alive, but nobody has ever built one, however crude.
Also, we're talking death of the system, which is different than cellular death. People are alive in more than one way, and the death of one way is not necessarily the death of the other. Organ transplants would not work if they were biologically dead, despite their being taken from dead people.

15

New Theories / Re: Is it Possible to Contain Infinity in a Finite Region of Space?

« on: 12/11/2021 18:03:23 »

They say a black hole warps spacetime infinitely. Does this mean the distance between space points in a black hole is somehow infinite?

It doesn't mean that, but if you're inside a black hole, there's no spatial limit to your ability to travel. There's no spatial boundary against which you can bump.

To some alien existing in a black hole it would look like he's in an infinite universe

Not true. There's a limit beyond which he cannot see, just like there is for us on Earth. There are places you can see that you can never visit. Things aren't going to suddenly appear larger just because you crossed some arbitrary event horizon.

but we, outside the black hole would think he is in a finite region.

A black hole is not a region of space, finite or otherwise, at least not in the usual coordinate system (where 'meters' are meaningful) to us on the outside.

16

Physics, Astronomy & Cosmology / Re: The Physics of Neutron Stars

« on: 11/11/2021 20:56:26 »

Oh. So... it's NOT made only out of Neutrons? That's... honestly really lame, ngl.

Apparently the protons (or more accurately, positively charged 'quark soup' as evan points out) and electrons can't get to each other, preventing further reactions that would make more neutrons. Still, how do the protons end up in the middle instead of mixed through the neutrons like they are in a large nucleus? Under such conditions, they are perhaps more dense, allowing more mass to pack into less space, and hence the neutrons buoy up forming the 'insulating' layer outside. I can't say for sure.

Does Dark Matter even react with ANY of the four forces?

Just gravity, and if you don't count that as a 'force', then there's only three forces and dark matter doesn't interact via any of them. But dark matter still causes gravitational time dilation if you concentrate it somewhere, so that's a gravitational effect.
Dark matter shoots straight through a neutron star and back out, but if it comes within the photon-sphere of a black hole, it's not ever coming out, and it adds to the mass of the black hole.

I've been led to believe that all of the Sun's energy came from the nuclear fusion processes happening in its core where Hydrogen atoms are fused together into Helium.

That's a very short description, but hydrogen is made of just a proton, and the neutrons need to come from somewhere, so the process has to involve the creation of them if it is to make helium, which is two of each. That's why our attempts to fuse hydrogen on Earth first has to find the rare isotope of hydrogen ²H with the neutron already present. ¹H (a lone proton) just doesn't fuse to anything.

Not too long ago I was told that the Sun also produced Antimatter.

Yes, as part of the neutron-creation process. Two protons collide and one emits a neutrino and a positron, leaving a neutron behind. Charge/lepton-number is nicely preserved. Everybody goes home happy.

Is there anything ELSE that the Sun does that I don't know about?

We all could spend a lifetime and still not know all about the sun, or about any other subject for that matter.

I didn't mean ignore as in get rid of. I meant ignore as in you, the person touching it, weren't affected by the things whatsoever (basically Superman).

Hard to say. What are you touching? The outermost layers? That's like touching Earth by colliding with one upper-most atmosphere atom. You'd not notice.
With a neutron star, it would be fatal to a human to even get close to it, like in low orbit or something. So you'd need to be superman just to be there, let alone actually contact anything.

So I said it was 'hard'. You'd not be able to move the surface, except to make waves of some sort in the atmosphere.

Engineer was the wrong word. I meant extracting pieces of a Neutron Star with a giant megastructure of sorts and then building materials and objects from that. Would that be slightly more plausible?

You'd have to use something like EM force to do it, and it obviously is being dwarfed by the other forces, so no way to touch it with any tool without the tool just becoming part of it.
If you had a piece of it, it wouldn't be stable for even an instant, and would probably act like a bomb or something. It needs the pressure to be stable.

17

Physics, Astronomy & Cosmology / Re: The Physics of Neutron Stars

« on: 11/11/2021 18:03:31 »

Question 2. Assuming Neutron Stars really are made up of only Neutrons, what exactly holds them together and keeps them stable? I mean, it can't be the Electromagnetic force if it's made up of only Neutrons, right?

Gravity holds them together. They're stable because there's nothing else they can be. It would require energy to say decay them into a proton/electron since there's no room for that pair. So it's stable.

It's not just a solid ball of neutrons. The inner crust is made of essentially superfluid neutrons. The outer crust has ions and electrons. The outer core has protons of all things, implying a massive charge imbalance between the inside and outside.  See wiki page showing pictures of the how the more current models lay it out.

Question 3. The reason why we're not able to see Dark Matter with our eyes or our various forms of technology is because it doesn't interact with the Electromagnetic force and therefore doesn't emit, reflect or even absorb light. If Neutron Stars had a similar thing going on, it would be logical to assume that they too don't interact with light in any way shape or form and would therefore be invisible as well.[/quote]Of course they interact with the various forces. Something needs to keep it from collapsing, which is mostly the strong force. Dark matter doesn't interact with the strong force, and would pass right through a neutron star and out the other side. Light does not do this, so a neutron star doesn't behave at all like dark matter. They emit/reflect light just fine, so you can see them.

Question 4. According to a YouTube video I found online, Neutron Stars form when the pressure of a collapsing star gets so great, that Protons and Electrons fuse together into Neutrons. Assuming this information is correct, how the hell does this not violate conservation of Baryon and Lepton number?

This goes on all the time in our sun, creating neutrons at the rate of tons per second, and no violation occurs. It does involve creation of a neutrino which probably exits the star. See proton-proton reaction.

Question 5. What would a Neutron Star feel like to touch? Obviously we would have to ignore the existence of the insane thermal radiation, blinding light, super strong gravitational field and super strong magnetic field

That eliminates pretty much all of what it would be like. It's just a hard rock with all that taken away, despite it being liquid on the surface.

but would the star itself feel like normal, gaseous plasma stars, or something else entirely?

There is an atmosphere if that's what you're asking. The hard part is below that. Our sun is pretty much all plasma

If it really is made up of only Neutrons, would you just fall right through it

Of course not. The other forces would prevent you from penetrating, else it would fall into itself.

the lack of the Electromagnetic force simulating the sensation of touch (this is after all, the force that allows things to touch each other in the first place).

That's because EM stops you before your atoms get close enough to the door knob to allow other forces to come into play.

Questions 6. How feasible on a scale of 1 to 10 would it be to engineer everyday objects and materials out of the same stuff Neutron Stars are made of?

Would think not at all. It isn't stable without the pressure, and there's no EM way to generate that sort of pressure.

No idea about strangelets.

18

Physiology & Medicine / Re: Do memories exist after death?

« on: 10/11/2021 16:10:37 »

If that could work it would be because the animals were not dead.

It's a technical problem. Let's say that the technology is advanced enough to scan and record all molecules of the hamster, and then restore it to the original state before it was properly killed. Does it ever die?

If you're scanning a live hamster, then sure, you get one (or many as you want) new live hamsters, complete with memories, by (instantly) 3D printing some molecules in the exact same state. Whether the original scanned hamster is still alive or not is irrelevant.

In the frozen hamster case, in principle you can cut off its head, so some of us will say that it's dead.

A severed head is not dead. If not frozen, it soon will be without decent life support.

So the severed head must still contain the memory.

Even not frozen. People with severed heads have been known to still look around and/or attempt to speak, but the loss of blood pressure tends to make one lose consciousness in a few seconds. Death takes place several minutes later. The memories are lost before death takes place, as evidenced by those who have been revived from sufficiently near-death states.

- - -

In support of Paul's query, some memories are stored apparently as chemicals. I remember an experiment where they taught some flatworms to perhaps run a maze or some task requiring memory. Then they ground them up and fed the slurry to other flatworms. The flatworms that ate this stuff were able to better perform the task on first try than those that ate similar food without the 'memories'.

19

Just Chat! / Re: Why do we have world problems?

« on: 07/11/2021 14:33:40 »

Why do we have world problems is it due to smart people not being as smart as is needed or is it due to the population of less than smart people.

I can argue that people are probably smart enough, but their priorities do not include the problems of 'the world'.
On the other hand, perhaps we're not smart enough, because while I see no end of topics identifying world problems, I don't see any with real solutions to them. At best, they posit ways to delay the inevitable. If we were smart, we'd suggest real solutions, however unlikely they are to be implemented. I don't see that happening.

We still have them because
- - -
- we had incorrect priorities of which problems to solve first.

Exactly

20

Technology / Re: What are some low-tech ways to address climate change?

« on: 05/11/2021 01:23:15 »

Rather than just list some feel-good actions one can personally take (sure, renewable energy is better than consuming fossil fuels), I think you need to start with identifying some specific goals we're trying to achieve with the solutions being discussed. I say this because without it, all you're doing is causing a delayed and more thorough destruction of what you are probably intending to not destroy.

Since it seems that there is not yet enough political or economic will to ...

There will never be any such will. The politicians are interested in short term gain for the people and the economy. The scientists point out the problem, but offer few if any real solutions. I'd be hard pressed to suggest specific actions without said statement of goals.

like population control, limiting meat-based agriculture/diet, not clear-cutting our forests, different approach to transportation, less materialism etc.

The problem with any of these actions is that it makes you less fit. A country that limits births and keeps its forests will be taken over by the countries that burn the candle at both ends and consume the resources declined by the country doing the better thing. So my contribution is a world government with real authority, that has yet-to-be-identified goals in mind and not necessarily the immediate comfort of votors. Thus it will probably not consist of elected leaders. Such a thing would form if there were a common enemy such as aliens, but we apparently don't consider climate change to be such a common enemy.

While heat pumps, solar heaters are better than gas-, oil- or coal-powered heaters

Maybe. Electricity is notoriously expensive, so a 200% heat pump might still consume more resources than direct burning of fuel. Wood is renewable, so burning it adds carbon-free heat for free so to speak. Oil/gas does not of course. I agree on the insulation bit. Easier said than done since it isn't trivial to insulate an older building.

wind-powered heaters may well be the way to go. Essentially, the mechanical energy of the rotor can be converted directly into heat either by using a Joule heater (like a water brake) or an induction heater (spinning a magnet around near a conductive material to produce eddy currents)

Those are not even 100% efficient. The wind power is kinetic energy. That should directly drive the compressor on some sort of no-electricity heat pump, yielding better than 100% efficiency of wind directly to heat. Consider that one of my contributions. But who wants heat that only works when the wind blows? Needs backups.

We might be able to send some energy back out to space more efficiently.
Just simple mirrors or white paint over dark surfaces that get direct sun would be useful.

We don't want to throw it away like that. Put a solar panel there, or a tree. Use it. All the solar energy coming in ends up in space anyway, so said mirrors are not going to change the planet temperature except during a brief moment while the new equilibrium is set up.

Also, to increase the rate of energy loss from the ground during the night time, wind, hydro, or thermoelectric power could extract usable energy out of the surrounding environment and be used to power LEDs or lasers that can be used to emit visible light into space.

You want to generate power and eject it instead of put it into the grid? That's just backwards...