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# Dagl1

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## Posts posted by Dagl1

### Question about length contraction and motion

Sorry , I have not forgotten about the thread, but am a little busy with some reallife things, will respond as soon as time allows me to sit down and think about the topic once more!

### Question about length contraction and motion

I see, that's a good point; didn't think of that, thanks!

### Question about length contraction and motion

Hmmm, I realise my words are pretty fuzzy when I describe it, but here it goes: A frame is a particular set of I suppose coordinates that are based upon a specific observer. I would say that a grid centered around a specific observer is a frame of reference. Inertial would then imply that it isn't accelerating (but that part I still don't really get, as you can always set yourself to be non-moving and non-accelerating by just thinking of your surrounding as decelerating).

That is a pretty ambigious definition; I never really thought of the definition as described in words; If I am on Earth, then since the Earth is moving with me (ignoring its rotation and stuff, because I suppose that might give some additional problems) the Earth and I are in the same frame of reference. A rocket flying away from me, or a person on a train (very fast moving) is in a different frame of reference.

Is this correct, or am I missing it;/

Regarding the proper distance, so far I can understand (I think); with no movement relative to two points, we find the proper distance, which is also the largest (with all movement reducing the distance?). If I moving with the speed of light, that then also means there is no distance right? Constant * sqrt(1-(1/1)) = Constant *sqrt(0) = 0 right?
And any speed in between 0 and c will be between the proper distance and 0, relatively?

I see now that this also answers my question regarding how we know this distance is the actual distance, as this function doesn't really allow for anything bigger than Constant*1, and therefore that is the proper distance (hope I am correct here).

Still very interested in what you can then tell me about the proper length!

also thank you for the continued responses!

### Question about length contraction and motion

6 minutes ago, studiot said:

The negative is how we show which side of C the approach is made.

Never be afraid to draw yourself a simple sketch.

Have we got this straight now?

I would like to move on to the next item in my calculations and I can then use this sketch to show what I am doing with the formulae so you can do less translation and concetrate on the physics/maths.

The problem wasn't the sketch, I see now that the difference between speed/velocity was something I wasn't really taking into account. Yes we got it straight;p

### Question about length contraction and motion

As long as we understand each other now;p I feel my sentence meant that, but I see it can mean multiple things, sorry for being vague. The semantics discussion are not as important for this thread.

Edit: changed sentence

### Question about length contraction and motion

3 hours ago, swansont said:

They must be at rest with respect to each other to be in the same frame

Is that not what this means? If I am not moving, and I see you not moving, then we are both in the same frame? How could it otherwise be? If A sees B not moving, and B sees A not moving, assuming both take themselves to be at rest, is there a possibility for them to not be at rest? This is what 'two observes that are in their frame both at rest' means or can it be taken differently? Am I still missing something or is this just more semantics?

4 hours ago, studiot said:

Since you are listed as still online, let's try and deal withthis one quickly.

Sorry Studiot! I come and go, didn't notice your message earlier;

I can definitely go with your explanation of East and West and using negative there, maybe it was a bit pedantic of me, but approaching has no directionality (as far as I understand the term).
Anyway, for S who is in the East, S will see T is moving East, or S is the one moving Westwards to a stationary T?

### Time dilation, electrons, and quantum mechanics

Thanks, I understand that it is a classical (non QM) thing, but my questions about the synchroton are more regarding relativity and the length contraction, I suppose I might think about it a bit longer and then maybe ask it as a seperate question. Either way thanks for everyones explanations

### Question about length contraction and motion

I was not very careful in that last response;

Two observers that are (in their frame) both at rest, are in the same frame. If from the perspective of one of them, the other is moving, then they are not in the same frames. This is at least how I understood it, but I see now that my response is not saying that. What I meant with "If the T and S are not moving at the same speed relative to each other, they by definiton can't be in the same frame right?" is that if they aren't at rest (both moving along line A-B at the same speed so that the distance between them does not change), they must be not in the same frame. But I see now that what I said was pretty vague/incorrect, my bad.

Okay just to reiterate what you said (to make sure that I am following you). Each observer has its own frame, and one observes movement relative to their frame.
I thought I understood inertial frames, but even if you are accelerating, you can just take your own frame as inertial right, and thus say that whatever you are comparing your frame too is decelerating (or vice versa)?

If I am in my own frame, and I observe someone moving accelerating towards me, am I not still in my own inertial frame though?

On 9/3/2021 at 2:24 PM, studiot said:

So if T sees S approaching at velocity v (in this case 0.8c), then S sees T appoaching at -v (or -0.8c)
(Note that we are saying T sees S approaching, it does not see itself as travelling it sees itself as at rest)

Which is what I said, but not what you said. It is important to get this straight, before moving on to proper distance and proper length.

This I cannot understand, how can one approach at a minus velocity, they both see each other approaching at 0.8c? Maybe this is the big hiccup but... if I run towards you at 5 km per hour, then you are approaching me at 5km per hour, from your perspective you, I would be approaching you at 5km per hour. Ignoring that in this example I am obviously the one running, but let's say we are in space and neither of us is doing anything, we are just in motion. Why would one of us think the other person is going backwards (this is what negative velocity implies, or at least how I interpret it, but that is probably wrong then).
You call it the relative velocity, but that relative velocity must remain a positive number right, otherwise one would think someone is receding while the other thinks they are approaching?

On 9/3/2021 at 2:24 PM, studiot said:

1) The calculations come to the same figure whether you use v or -v since it is squared.

If v has a value other than zero T and S are moving relative to each other but calculations in either frame will give the same result ie S measures the same distance to T as T measures to S.

I suppose as you said, I should first understand the previous points, but this makes sense a little. If I move towards a star at 80% the speed of light, and I measure the distance to be 6LY, then if I moved very slowly towards it it would have been 10LY? And measured from the star, I too am 6 LY away when moving at at 0.8c, right?

On 9/3/2021 at 2:24 PM, studiot said:

2) If v = 0 then T and S are not moving relative to each other, and the measured distance between T and S is a maximum.

This distance between them is not changing with time as the movement occurs.

This maximum distance is called the proper distance.
I will state that the proper distance has the same numerical value measured by all observers, not just T and S.

Since T and S are not moving then they are in the same frame.
That is we have reduced or transformed the motion of T to the S frame or S to the T frame.

The proper distance is the distance measured between any two points in the same frame, ie at rest with rspect to each other.

Okay! That is pretty understandable. How does gravity (acceleration) then come into play with distances (although maybe that is a question I can ask in another thread afterwards, after making sure the last points were understood).

Thanks everyone for their answers and continued responses!

### Question about length contraction and motion

Yes this seems to be clear, as each has its own relative motion, they are in differnt frames.

If the T and S are not moving at the same speed relative to each other, they by definiton can't be in the same frame right?

### Question about length contraction and motion

23 hours ago, md65536 said:

Yes, the distance to the star is different in the different frames of reference. There are invariant measures of distance, eg. the "proper length" of a 1 m stick at rest is always 1 m and everyone will agree on that, even if the stick is moving relative to some observer and is length-contracted ie. has a coordinate length less than a meter in that observer's coordinates.

I generally understand your responses to my initial question, but now I wonder how we can even have any 'proper length', of course in 1 frame of reference we can agree on a specific length. But within the universe is there then anyway to say what 'proper length' is, if the distances are all different from different points of view. Is there ever a way to get down to a 'universal length', as this is what 'proper length' implies for me. But I thought that was one of the things that relavivity brought us, that there is no one main frame of reference, and thus also no one main of distance between points?

Studiot seems to be providing me at least in part with an answer:

21 hours ago, studiot said:

So we must convert the 3Ly separation to one frame or the other the T frame or the S frame, it does not matter which.

This will give us the 'proper distance' between T and S. The proper distance Lo is always longer than the measured distance between moving objects and is the same in all frames.

Although I still don't entirely get how this is a 'proper distance', does the proper distance represent the amount of protons I could put in a row to reach such a point? But even those can get length contracted? How do we know that the proper distance is not actually still measured from a moving frame, or that there is even a 'stiller frame'?

21 hours ago, studiot said:

his is what I mean by your original statement was incomplete.  (no criticism intended I am being detailed in order to help)

No criticims perceived , I love the detailed responses and am happy you guys are sticking by me even as I am floundering through incomplete comprehension!

I then also have another question as to how the expansion of the universe comes into play with this, how does length contraction work for galaxies far away and which are accelerating away from us, already at speeds faster than the speed of light. When we say nothing can go faster than the speed of light, I am aware that due to how this is calculated the 'actual speed' of two things at relative speeds is never faster than the speed of light (I hope I am correct in my understanding here?), so I suppose we use that calculation for length contraction?
What I am getting at is that in my mind, given that galaxy A and galaxy B are already at such distances that the expansion of the universe leads to faster movement away from each other than light will be able to travel (so the galaxies that are on the edge of the observable universe and will then 'move out' of that bubble). How does lenght contraction not lead us to say that these are actually very close (because relatively we are moving at enormous speeds)? I really seem to have some trouble with this whole concept;p

### Time dilation, electrons, and quantum mechanics

@swansont Your explanation made it quite clear what the problem with this idea about speed of electrons is.

I then do wonder why this wouldnt apply to synchrotons? Or I should clarify, when you said that synchrotons are classical and we can speak of the speed of electrons, does that mean that the book didn't water down that explanation (so a higher frequency of radiation is observed because the electrons are moving at relativistic speed and as such the frequency is higher than just the regular amount of times of orbiting per second?) That to me still seems a little illogical (and thus I probably misunderstand it), as even if space is warped, the amount of times it should go around 360 degrees should not change even if it goes at very fast speeds?

I feel either this is another piece that I have to get my head around, or my assumptions might be wrong. So to reiterate; if a electron moves 30000 times per second around an synchroton, and it is moving at relativistic speed (99% the speed of light for example) (ignoring that for such amount of orbits per second the synchroton might be necessary to be super large), does that we observe a higher frequency than 30000, because it has more energy, or because it somehow manages to pass a point (let's say at 0 degrees of the orbit) more than 30000 times because the space is contracted? For me this doesn't make much sense so I hope you or someone else can shed light on this!

Thanks everyone already for their responses!

### Question about length contraction and motion

Thanks! I will read and digest the information in detail later today!

### Time dilation, electrons, and quantum mechanics

Thanks everyone! Later today or tonight when I have more time I will go over your responses and actually stand still to think about them!

### Time dilation, electrons, and quantum mechanics

Okay thanks, I will try to look more into it! Thus far it is not yet completely understood by me, but maybe I need to read a bit more into this if I want to really understand it.

### Existence is...the Absolute Singularity.

23 minutes ago, WendyDarling said:

Existence in and of itself, every variation is intelligence formed into an order, a pattern.

Patterns and order, complex systems interacting with other complex systems is intelligence actualized.

Be absurd to say out of non-existence popped existence in all its splendor.

Be equally absurd to say all is random, chaos, chance...none of which exist.

All is imperfect order. Order requires intelligence.

If all understanding ceased to exist, chaos would exist.

It seems you and I don't use the same definition of intelligence...

Chance, chaos, they don't exist? I really am unsure why or how you get these ideas. I don't think these ideas hold up to scrutiniy, but I also realise that this is the extent to which you answer, so it might not be a very fruitful discussion. Things like 'be absurd' are... well your opinion. You like to state the way things are, but don't provide evidence or even follow sound logic that makes sure there are no other possibilities. It might be a good idea to focus on explaining your concepts in more steps, explain why things are like this and not in other ways. Thus far you did not seem to answer my question, or those of other people. I asked "Why does intelligence have to have always existed, what evidence is there for this. What evidence can you provide that goes agains the claim 'intelligence has not always existed' or 'there was no intelligence on Earth before life'. "

One can only find several extra statements from which to understand that your definition of intelligence is different from that of other peoples. It might be good to give a proper definition of the words you use. Are they different from what some dictionaries propose, if so,  you should note this down so we can understand.

### Existence is...the Absolute Singularity.

Why does intelligence have to have always existed, what evidence is there for this. What evidence can you provide that goes agains the claim 'intelligence has not always existed' or 'there was no intelligence on Earth before life'.

You keep repeating that your logic is simple, but for those reading this thread it is not, and it seems quite flawed. People in this thread have asked you to clarify things, but you seem to not entirely engage with their arguments.

It might be a good idea to go back into the thread and from page 1 check which definitions have not been given, or which comments you have not fully engaged with yet. This will help both the discussion and the will of other people to participate! Good luck

### Help PCR fungi

40 minutes ago, Alex007 said:

thanks a lot. unfortunately, however, I cannot understand the steps following the electrophoresis. If you give me a summary I am grateful

Could you give me a bit more information regarding what is not clear? How far do you understand this?
There are not that many steps after this, so you might gain a lot by going over what parts you do understand as a learning experience;

After gel electrophoresis we have:
1. DNA samples with no visiblebands were re-amplified with 35 cycles and DNA samples
with strong bands were re-amplified with 25 cycles. Both negative and positive controls were included in PCR and sequencing runs.

2. PCR products were pooled at approximately equimolar ratio as determined by gel band strength.

3. Samples were combined into two libraries that were purified by FavorPrep™ Gel/PCR Purification Kit (Favorgen-Biotech Corp., Austria), following the manufacturer’s instructions.

4. DNA from each library was quantified using Qubit® 2.0 Fluorometer (Invitrogen, Life Technologies, CA, United States) and dsDNA High Sensitivity assay kit (ThermoFisher Scientific, Waltham, United States).

5. Amplicons were pooled into two libraries and subjected to adaptor ligation and Illumina MiSeq sequencing (2 × 300 paired-end) in NERC Biomolecular Analysis Facility (Liverpool, United Kingdom).

I assume this is either homework or you are trying to apply this, in both cases it helps to explain the steps up so far you do understand them, and explain which parts are unclear regarding each following step. This might give you pointers at what to look up yourself. What is your background?

Point 1 and 2 should be clear as they are just using definitions, point 3 has the word library in it, but you could just use collection. Point 4 are technical ways of measuring DNA quantity, point 5 is about Illumina sequencing. You might want to watch a video regarding it if you are unsure how this works, you might also want to look up the difference between single and paired-end sequencing, as they use paired-end sequencing!

There is also this much longer workshop, which goes over everything in much more detail (have not watched all of it):

### Time dilation, electrons, and quantum mechanics

1 hour ago, swansont said:

There are relativistic corrections to the energy, which do not explicitly require having motion.

The explanation that it’s relativistic speeds is pop-sci/watered-down. QM uses things like energy and momentum operators, and you solve for energy eigenstates. Which differ when the energy gets to be an appreciable fraction of the rest energy.

I hope I understand you correctly, do you mean because the energy of the electrons is higher because they are moving at relativistic speeds, there is therefore a correction necessary, however this correction is a correction to the energy? Does that mean that in the synchroton example, the higher frequency is also due to this energy correction (that feels a bit strange, as frequency is directly correlated with rotations in this case right?)?
Maybe my question is better asked this way: are corrections to the energy (due to being closer to the rest energy) different from corrections to time, due to speed?

I still am not entirely sure how to interpret your answer in regards to a probability cloud, other than that I can mentally accept that things in this cloud may have high energies, but you do mention momentum operators. Does something which only exists at certain positions at certain times also have motion? Is that then independent of the probability?

Sorry for not getting your answers;/

### Help PCR fungi

So after PCR, they took 5 microliter and ran it on a 1% agarose gel (which is as you say gel electrophoresis). Although this does not tell you the amount of DNA in micrograms, the relative quantity (so between the replicates) can be estimated by looking at the gels. They then use the band strength to decide on how many extra cycles of amplification is needed.

Does that make it clear to you or was your question pertaining more of the steps?

### What is the Difference Between a Cold and the Flu?

What exactly is the question? They are diseases caused by different types of viruses (Rhinovirus vs Inflenza). They also have, as you alreayd note, different symptoms associated with infection and different rates of severe problems.

What difference would you like to know more about?

### Time dilation, electrons, and quantum mechanics

Hey Joigus, its been a while, been lurking around here and there, busy with life^^.

Thanks for your answer!
Hmm I will have to look a lot more closely at the mathematics, which might help, but so far I don't think I completely get your explanation. Would it be possible to word it differently. If I have a stationary fluid, then the individual particles inside the fluid are all moving in random Brownian motion. So the fluid as a whole is stationary, but the particles inside are not (I know that is a bit pedantic but I think it is stopping me from understanding your explanation in more detail). How then does this relate to the electrons. Should I think of the electrons as being stationary as a whole (the system), but parts of it are moving?
How does that reconcile the 'movement of electrons at relativistic speeds' and their probablity cloud. I think what I am asking is; do the darn things move or are they just at specific points (I think you answered this, but I just don't get it yet). If they don't move, is what is said in the book regarding the physical/chemical properties of these atoms being dependent on understanding that electrons move at relativistic speeds still true?
I suppose it is not as simple as 'they move' or,  'they don't move' ;/

Anyway I will reply later today, time to go to work and already thanks in advance for any potential answers!

-Dagl

### Time dilation, electrons, and quantum mechanics

So I have been reading a book about relativity by Paul Davies ("About Time"). In this book he mentions that in order to fully understand the physical (or chemical) properties of heavy atoms such as gold and uranium, one has to take into account that electrons move at relativistic speeds around the nucleus. Additionally he mentions synchroton radiation (which might be not entirely related to my question). My question is that I was under the impression electrons do not actually move around the nucleus at all, but just 'are' at specific locations around a nucleus, based on the probability cloud of electrons in that specific shell. This does not really fit (for me) with what is said about electrons moving at relativistic speeds, as in that view there is no motion at all?
He mentions as well that synchroton radiation is at higher frequencies than would be expected from the speed at which electrons orbit the machinery, because they are moving at relativistic speeds and thus the radiation pattern is at a much higher frequency. I am not sure if synchroton electrons also follow the quantum mechanical probability clouds, and thus not sure if this might not be related to my initial question.

Could some helpful members show me which assumptions are wrong or provide me with a better way of thinking about these things. I do realise that this also might be a case of where quantum mechanics and relativity don't merge yet, but I don't wanna come to that conclusion yet as it is much more likely I just don't understand the concepts well enough.

Kind regards,
Dagl

### Question about length contraction and motion

Hi there,

I have been reading a book about time (with an equal name, by Paul Davies). In it he explains time dilation and parts of relativity. I have two questions regarding what I have read so far, one for another thread. My current question is regarding the perceived difference in distance when two observers are in relative motion to each other. A star 5 light years away from the earths point of view, might be only 3 light years away for someone traveling at 80% the speed of light towards this star, if I understand the physics right. This alone I can understand, however I cannot seem to then comprehend how this would work for motion between other observers.
Even in writing my question I notice that the ideas are very fuzzy as I keep rewording my question: If I have a map with the 'position' of different stars around the galaxy, or different galaxies in the observable universe, and we assume these bodies are moving at high speeds relative to each other, does the distance between two galaxies depend on the specific galaxy I measure these from?

I am sorry for my very fuzzy question, it is obvious I haven't wrapped my head around the length contraction yet. I think I am trying to ask what happens to the distance between different points if the motion of the observer relative to these point is what determines the distance. Does this mean that if I am in the Andromeda galaxy (or a theoretical one that is moving at very high relativistic speeds to ours), I would calculate different distances between points in the universe.
If so then is there any 'absolute' distance between any points? Does it make sense to say that a star is x light years away, if by speeding up or slowing down, that distance is changed.

An additional question: let's say there is a galaxy A some distance from ours, and in its extension (so in the exact same direction but further away) there is a galaxy B, 'twice as far' as galaxy A is. Galaxy A is not moving relative to our Home galaxy, while galaxy B is moving at 99% the speed of light, wobbling back and forth. What are the implications for the actual distances between the galaxies. Galaxy B's distance should not change as it moves (through some unknown means) away, and then back to us. In my head, which I think is the wrong way to think about it, I would say that by measuring the distance between Home galaxy and B, I would see a much smaller distance than 2xA, while in reality they are just twice as far away from each other. I suppose the reason is that because galaxy B is in motion, we cannot say it is twice as far away from us, as we can only measure things from one frame of reference.
However my mind remains fuzzy regarding these concepts, if some people would be willing to educate me and show me the errors of my thinking, that would be greatly appreciated!

-Dagl

### Cell counting

An hemocytometer, microscope, tally counter in hand, oh and trypan blue if I really need it (depends a bit on your cells, and how important the counting is, no reason to not use it other than that you have to find where your labmates have hidden it).

We also have some fancier machine, but it isn't calibrated for my cell types so haven't used it. Do you want to know the brand of some automated counters like that, or this question is just about how to count your cells?

### Chromosomal segregation and homology directed repair, how?

Hi there,

I have been recently been thinking about the determinant chromosomal positions we see for each chromosome within a given cell type, many of the chromosome pairs are quite far away inside the nucleus, and these positions seem to not be moving that much at all (that is, we can consistently find the same/similar topology in a given cell type). Now that is all good and nice, but it breaks my expectation of homology directed repair (HDR) a bit. In HDR, a double-stranded break on one chromosome is fixed through the recruitment of the other chromosome, and while I am aware that HDR is not as frequently employed within a cell as NHEJ (non homologous end joining), text books and research will still show that HDR exists.
How can the segregated chromosomes still facilitate HDR, does the whole chromosome move or is only a specific region of chromosome xA moved to chromosome xB? If so, how does the cell know where to go, and how can in this time frame NHEJ not already have fixed it?

The only thing I can personally think of, is that HDR is only likely in proliferating cells, where the chromosomal topology changes during M phase? or during the S-phase and G1 as then each chromosome has a duplicate closeby (which would mean HDR has only a small window to work in)?

Kind regards,
Dagl

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