« on: 24/06/2022 15:04:34 »
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No, anything does not go.Why do we have to be subjected to such juvenile garbage on a science site???It's the "Just Chat" section of a science sight. Anything goes, as the description pretty much states.
Also, I do for some levity.Levity is one thing, but you often use this section for posts in bad taste and/or of a sexual or crude nature. That’s not what this section (or any other) is for.
Hi.Yeah this makes sense to me. Thank a lot.Is your origin (0,0) at the very back of the back fin of the ship like in the video?Yes. The origin is intended to be exactly where they placed it in the original video (although I only sketched it, I didn't get a ruler and compass).
The planet based observer says the back of the fin is at x= 0 when t =0. Spaceman says the back of the fin is at x'=0 when t' =0.
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Just to emphasize one issue, although in my diagrams it looks like the x and x' co-ordinates of the rock collision event are both +5, they aren't actually exactly the same. That's just that the diagram is only a sketch and I haven't placed all the gridlines exactly the same space apart etc. I just want to dispel the notion that there was any reason why they had to agree on the spatial location of the event... there isn't.
I've run the precise calculation with these figures (they are roughly what was used in the video).
Set the velocity of the rocket = half the speed of light.
Use units for measuring time and distance so that the speed of light, c = 1 in those units (Just to be clear that's not going to be seconds and metres. It's just conventional to set c = 1).
Set the rock collision event to co-ordinates (x, t) = ( +5.00 , +1.00 ) as was shown in my diagram for the planetary observer.
This becomes (x', t') = ( +5.20 , -1.73) in the spacemans co-ordinate system.
So, with these figures, the spaceman and planet based observer disagree on the both the location and time of the collision event.
Is your origin (0,0) at the very back of the back fin of the ship like in the video?Yes. The origin is intended to be exactly where they placed it in the original video (although I only sketched it, I didn't get a ruler and compass).
You are wrong about GRAVITY per Einstein!
Acceleration is one part distance and two parts time.You keep saying that. It still doesn't make sense.
he bending of light is actually connected to the second time vectorTime is still not a vector.
The problem physics has created for itself is in not recognizing how gravity and the pressures it generates impacts the phase characteristics of the matter contained.Nonsense.
the layers of the earth; oceans/crust, mantle, inner core and core seem to coordinate with different phases of water.It only seems that way to you.
This has little to do with space-timeSo why do you mention it?
second time vectorTime is still not a vector.
Oh please, don't give me the wrong advice of explaining reality and don't use Darwin's invented criteria of falsification. To falsify ToE, you need to use this approach: ToE vs reality, and never, ever rely on Darwin's idea. Behe had done that. He was ashamed.You claim to have reviewed all ToE papers and falsified them. You have 24hrs to provide the list you claim or you posts will be locked until you provide that list.
Anyway, point being, on the earth's surface you don't get the swimming up and down a river effect, so Michelson's experiment would not show earth rotation effects on light, but would it show effects from earth's orbit around the sun?It was designed to detect motion relative to the medium (aether) in any direction. If there was such a medium and the current Newtonian model was accurate, all orbits, spins, etc would involve daily and annual variations due to changes from spin and orbit. The instrument was sufficiently sensitive to detect 1500 mph changes, which is the typical change in velocity over the course of 12 hours.
So Michelson did prove a lack of aether but not a lack of Sagnac effect from earth's rotation.Yet again, no proof of lack of aether was made. It was simply demonstrated to be superfuous. No test for Sagnac was made since the experiment didn't involve a loop enclosing an area.
Apparently you agree that said Sagnac effect existsIt had better. There are devices in use every day that depend on it.
but you explain it as a relativity consistent effect because it involves a rotating frame.One can explain any situation using one's choice of frame. Sagnac is no exception, and can be explained via the properties of rotating frames, or it can be explained using only an inertial frame.
It doesn't actually confirm relativityRelativity has little to say about the Sagnac effec that Newtonian physics didn't already explain. Unless the device is rotated at relativistic speeds, there's no need to invoke relativity theory to predict the Sagnac effect, so no, it isn't really a test of relativity since relativity doesn't predict anything different.
Einstein just gave himself an out by saying that rotating frames are not inertial.Newton said that actually. He demonstrated that rotation is absolute, while linear velocity is not necessarily so (per Galileo).
Now there's the conundrum of why a rotating frame can be confirmed to be in rotation like that, what is it in rotation relative to?No relation needed in the case of rotation. That's what it means to say rotation is absolute. The rate of rotation of a closed system can be determined from within a box.
The same would apply to binary stars in orbit with each other, what are they rotating in relation to? Presumably an imaginary point between them called the barycenter, but how is the barycenter a stationary reference? It seems counter to relativity theory.Well, for a closed system, there is a frame independent worldline for the center of gravity of the system which does not accelerate, so is stationary in the frame of the system. The word 'barycenter' only applies to two-body system since with more bodies, nothing necessarily moves in a predictable path about the center of gravity, nor is even particularly attracted in its direction.
If there are two equal disks with the same axis, with a space between the two, what is the difference between one being stationary and the other rotating and the other way around, or both rotating in opposite directions at equal angular velocity?The first system has nonzero angular momentum. The 2nd system has zero angular momentum. Remember that momentum, like velocity, is a vector, and one must use vector addition when adding up the momentums of the respective parts.
The only difference between the two disk frames is that an observer on one would perceive centrifugal force and one on the other would not.There you go. It's not the only difference, but it's the most obvious. You could do really subtle special relativity stuff like measure the diameter and circumference of the disk, which will have a ratio of π only for a non-rotating disk, but to get a measurable difference with say just a tape measure, you'd have to spin it at a rate which would kill a human.
The use of energy to create force to produce rotational motion in one.Force (torque actually) is only needed to change the angular momentum of the thing. No torque is needed to keep it spinning, per Newton's laws.
Kinetic energy had been stored in the disk as inertial motion. The disk would continue to rotate, assuming no external friction or resistance, until that kinetic energy was transferred to another mass by exerting a force moving it outward from a position close to the axis to one farther away from it.To move mass inward, energy needs to be imparted to the system. The ice skater needs to perform work to pull her arms in and spin faster. Likewise, to move outward, excess energy must go somewhere. So for example, the spin of Earth momentum is slowly being transferred to the moon, raising its orbital radius. Of all the energy Earth loses in this process, only about 3% of it goes to the moon (a higher radius orbit is a higher energy orbit) and the excess is radiated away as heat.
"How much time have we, as humanity, left to prevent the point of no return for our climate?"
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:-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.
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.
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.
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 lightThis 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 hourAgain 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.OK.
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.
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 thatWho 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 :-Totally wrong. Daniel doesn’t know his stuff at all. Anybody can put out a podcast. It doesn't make them right.
‘ 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.’
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.
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?They don’t exist in the way you think about them, but what they measure and model are real enough.
this kind of neutrinos came to Earth from that supernova earlier than photonsYou are talking about SN1987A - the only supernova to date where we have linked a neutrino burst to visible observations.
You know, it's funny. I LITERALLY just had an online chat with a cosmologist yesterday evening and one of the things he said to me was that matter, as we currently know it, may not actually exist at all. Fields exist, and particles such as Protons, Neutrons and Electrons are merely excitations of those fieldsI agree with @Halc on this, but I think you need to sit down and think what you mean by the word exists.
At any rate though, I do understand most of what you're saying. Mostly that we have very little idea what light actually is.Actually we we know a great deal about what light is, how it works etc. It is another of those “merely” excitations of a field, and that means we can understand it in ways we couldn’t before.
The next important thing is that you have probably read or been taught that momentum = mass x velocity. This is probably why you are concerned about the photon having 0 mass but still having a non-zero momentum.I may be misreading what you say, but it implies that relativistic mass was ‘developed’ in response to the ‘rest mass’ of the photon being zero, and hence to maintain the concept of momentum for the photon.
There are at least two ways we can address this issue. The first is to say that many physicists were also troubled about this. It's a very good question to ask and something that does seem quite puzzling.
Physicist's were sufficiently determined to maintain this simple concept of momentum that they developed a quantity called "relativistic mass". They accepted that the invariant mass of a photon wasn't anything you could ever really measure, it certainly wasn't going to be measured as the mass of the particle when it was at rest in some inertial frame. So they determined that the invariant mass wasn't something that should be used in that formula momentum = mv.