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Dont say centigrade, the correct term is Celsius.Well, when talking about temperatures in the millions, the correct term is Kelvin. Celsius is only for temperatures meaningfully compared to the human habitat.
Two black holes spinning around each other, faster & faster...converge...beep!Of sorts, perhaps. The difference is that I can reach out of a boat and feel the water and detect if I am still or moving in that water. You can't do that with space, per the principle of relativity. The best they've been able to do is note the mean velocity of everything in sight and assign 'stopped' to that otherwise arbitrary velocity.
It sends ripples of gravitational waves out into space, Right?
A pebble/stone thrown in a pond, generates ripples.
Hence even though Water being transparent & tasteless it's still a Substance/Medium.
If those gravitational waves are travelling through space, is not Space a medium or substance of sorts???
Are G waves travelling thru a gravitational force field in space & not just simply space itself?They travel through space. A field is not a thing, it is a mathematical abstraction, a value assigned to the relative depth of the gravity at every point in spacetime. That slope of that depth determines the force that accelerates something at that point. A flat depth would entail no acceleration, but it would still be a nonzero depth.
Is there a grav field all over n evrywher in space, even in super voids?Yes, there is. The field may be relatively flat there, but it is anything but zero.
P.S. - n Y did or rather wen did Einstein say if u remuv d earth below our feet, v wuld xperience free fallin???That's what free fall is: Not having a non-gravitational force acting on you. Here we have the Earth below us putting a non-gravitational force upward on our feet and preventing our free fall.
Dat dosnt sound rite, Right?
Y wud v or an object free fall, fall is downwards rite, but no up & down in space...y won't v or d object just float freely in space?
Cherished light planes still take people to work after 50 years, and one occassionally encounters "warbirds" comprised mostly of bits of WWI hardware in the sky. GPS? Some of them don't even have electricity!They have a 1909 Bleriot near me, claimed the oldest flying aircraft in the western hemisphere. I've seen it in the air. No, it isn't a reproduction, and indeed, it certainly doesn't have GPS or probably an altimeter of any kind for that matter.
We know that liquids in space will be spherical and solids don't lose shape.Liquid (water at least) turns into frozen mist in space that quickly sublimes to gas. You're apparently thinking about zero-G such as the environment inside the ISS, which is not in space any more than I am.
What about foams? What shape will they take if they were in a zero gravity environment?Most foams (shaving cream, the foam insert in my sofa cushion) retain the same shape in zero G. A pile of shaving cream (and the cushion for that matter) will squash out under enough gravity/acceleration, while in zero-G it could probably be sculpted into whatever fragile shape you like.
In simple words ' what is the multiverse theory'??There are a lot of theories which claim the term. In short, a definition of 'universe' is given, and then for that universe to be consistent with some theory or interpretation, it turns out that other such universes need to exist.
Well, we don't experience living on a mathematical point, so no, it wouldn't be the solar system we experience.Quote from: HalcIf you treat objects as mathematical points, then there is no combustion and no tidal drift. The reversed solar system would be mathematically perfectly a rewind of prior state.True, but it would not be the solar system we experience; would it?
I have had ,in the past the belief that time required motion to exist.However I have been assured that clocks that rely on radioactive decay show that this is not the case.(no motion)I had responded to the posted question, but not so much to the thread title. This is an interesting point.
On a large scale, the world we exist in and the universe our world exists in has been, and as far as I am aware is forever changing. Using a second as a measurement for instance, our universe has been changing every second since the big bang, it is changing every second as I sit here typing this, and will continue to change every second into the future. Would this be a legitimate way of describing what is meant by a past, present and future? Past, present and future = change? If so, would the same be said of the quantum world?Time is change. Without change, there would be no meaning to time.
So, a clock in the lab here ticks 0.9999999993 times for every tick of a theoretical clock completely outside of a gravity well (and stationary).Completely outside Earth's well. Earth is a very small fish in a huge pond. That value is not 'completely outside of a gravity well'. You lost track of the condition upon which the value was computed, which was "Considering only Earth's gravity".
However, if that clock is in the solar system, its distance from the Sun also matters! On the surface of the Earth, the contribution from the Sun's gravity means that clocks are ticking about 0.00000000494 times slower than in "outer space", far from the Earth and the Sun. So the Sun actually slows clocks down more than ten times as much as the Earth, relative to clocks in deep space.Removing just one more object is still not 'deep space'. Just like the sun as 10x the dilation effect here as does nearby Earth, the sun's effect is dwarfed by the additional mass of what you're labeling 'deep space'. There is no such thing because it really is impossible to get anywhere close to being out of that well, even between galactic superclusters.
If the universe was 'flat' then I assumed that there must be an observational spatial direction in order to determine it was flat.Flat means that parallel lines stay the same distance apart, in any direction. Yes, direction matters, but our space seems symmetrical this way. With positive curvature (like the balloon), parallel lines meet. With negative curvature (like kale), parallel lines diverge.
If the universe is flat then is it possible to detect a direction in which the expansion is travelling? Perhaps taking the earth/solar system as a point of reference.From any spatial point of reference, like here, the universe spatially expands equally in every direction.
As the title says, if the universe were to slow down and perhaps even reverse direction, what would happen to light that was and is now travelling towards the edge of the universe?The expansion of the universe isn't a speed that is measured in distance per second. It doubles its dimensions every 2x amount of time. You can't technically double that.
As I understand it, the universe is expanding faster than the speed of light.
A “timely” thought experimentThis last one is unrealistic unless both clocks are stationary relative to each other, in which case both clocks will run at the same pace in any frame.
“In a galaxy far away”, there exists a star identical to our sun, with an identical “solar system”.
Earth is planet A with physicist A (PA) and clock A (CA).
Earth’s twin is planet B with physicist B (PB) and clock B (CB).
Each physicist can see his own clock and the other’s with no time delay for information transfer.
2. Each physicist sees the rate of time on the other’s clock as unaffected by gravity.No. If there was another clock in the same frame as the distant clock but not as deep in a gravity-well such as these planet-bound physicists, the clocks on any planet would appear to run slower. Hence they all appear to be affected by gravity, but equally since both CA and CB are in similar gravity wells.
3. Any difference between the perception of the rate of time between CA and CB, observed by either physicist, will be due to the degree of relative motion between the two galaxies; or relative motion resulting from differential motion within the individual galaxies.Yes.
If a photon has mass does it too increase when it travels at light speed?It doesn't increase with speed since it always moves at c. It increases with frequency, which makes the photon mass still frame dependent.
I’m just trying to get my head round the idea of proper mass, inertia etc, in another thread; so I’m going to have a go at this, to see how I’m doing.They're the same, yes.
I may be confusing “rest mass” with “proper mass” (possibly they are the same), but let’s start with rest mass.
This is the mass of an object as measured by an observer who sees that object as stationary. We can never observe a photon as being stationary, so we cannot assign it a rest mass.All sounds pretty good to me.
However, the photon has inertia, so it adds to the inertia of any system of which it is a part. Because of the relationship between inertia and mass, the photon must, therefore, contribute mass to that system.
I recently got into a debate at work regarding how mass can change in general relativity. In my feeble understanding of general relativity, an object with more energy bends spacetime to a greater magnitude, and so in terms of gravitation it behaves as if it has more mass.It does have more mass. Mass and energy are the same thing, so adding energy is the same as adding mass, and mass bends spacetime, so energy does as well.
But if this is true, does it also work for potential energy - If you lift an object up you put work into it.Yes! This is unintuitive, but if you lift an object, you have expended energy from elsewhere to the object, and it now masses more.
But does it now weigh more (or perhaps more than one would expect compared with simple Newtonian gravity)?The weight doesn't go up since you've moved it away from whatever gravity well defines 'down'. So the mass goes up a tiny bit, but the weight (gravitational force) still drops. If you have impossibly accurate weight and mass scales (spring and balance respectively), you'd measure more more mass but less weight at the top of a building.
Another possible scenario is when the Moon was much closer than it is now.Interesting choice of distance. At 10x closer, it puts the moon about exactly at geosync, so there would be no tides at all. If it was just a little off, yes, there would be time to form tides at full height, but also the crust of earth would bend back and forth, heating it dramatically. Maybe the heat of that would boil away the water.
Tidal forces follow an "inverse cube" law, so when the Moon was 10x closer, tidal forces would have been 1000x stronger - imagine a +/-1km tide! That would create an incredible amount of erosion - perhaps even enough to erode mountains faster than tectonic forces could push them up?
Can you explain how that works pleaseFrom wiki on tidal force:
It seems that human DNA (except native African) contains a small percentage of Neanderthal DNAIt is actually only a very small group in an isolated tribe in Africa that has remained free of Neanderthal DNA.
Thank you Halc.Gravity doesn't die. The mass of the burned out star is still there, even if the fuel is expended. Everything gets cold, but the orbital mechanics is little changed. If the one star was really big, it might die in sufficient splendor that some of the planets might not survive, or sufficient mass is expelled in the supernova that the planets might be thrown elsewhere. Probably they'll just move to higher orbits.
This brings up another question I have regarding Binary Solar Systems:
If one star within a binary solar system should die and ( if both stars had their own planets revolving), would it be possible for the remaining planets of the dead star to be incorporated into the system of the remaining star, should that star be close enough to attract these planets into it's gravitational pull? Therefore adding new planets into the now singular System?
The topic is "is lifting force possible?"The topic is "What is centrifugal force?". There never was a mention of 'is lifting force possible", including on the diagram. Of course lifting force is possible. I lift things every day.
The mass spends twice the time at the bottom going around the circumference of the larger wheel, so half the force for double the time makes for zero net difference.Quote from: HalcAs for using a bigger wheel at one end and constant belt speed, that indeed makes no changes except that the weight isn't going to slow at one end or the other. There will be no acceleration/deceleration since you specified constant belt speed.I wanted to say that centrifugal force will be bigger on a top of conveyor and less at the bottom of it. After sum of two forces you have force in direction against gravity.