Observations indicate that the universe's expansion is accelerating, which is consistent with the models that predict heat death.

\nHe never said it was a good diet.

\nIt depends on how you define your system and whether it is open and closed. If you consider just the flywheel as the system and you isolate it after giving it a certain amount of energy (and ignoring friction), then the conservation comes from the fact that the underlying laws of physics are rotationally invariant, meaning they don't change depending on its orientation, so there is no reason for it to gain or lose angular momentum by itself just because it is rotating. This result is from Noether's theorem and is the underlying cause of Newton's 3rd law.

\n\nIf you consider the flywheel as an open system, then you can allow energy to come in via the throttle, so angular momentum is not necessarily conserved in this system because you can add energy into it.

\n\nYou can go further and analyse the direct interactions and energy exchanges by broadening the scope of your system under consideration if you want to work out where certain quantities went, so you can include the engine and the workbench, the entire building it is in and even the whole Earth.

\nYou can't see the objects going through the event horizon initially, but the objects themselves do go through it and contributes to its mass, which also causes the event horizon to grow and if it grows enough, it swallows the "frozen image" at the horizon.

\nIt comes from the energy of combustion, which causes the pistons to move up and down, and that linear motion is converted into rotational motion via the crankshaft, which the flywheel is connected to.

\n\n\n\nIf I understand correctly physical things can not be infinitely small due to the Plank length

\n

Planck length is just the scale where the effects of quantum gravity are expected to dominate, based on dimensional analysis, and not a minimum length scale as commonly thought. There are in fact length scales that are at least 13 orders of magnitude smaller than Planck length with the possibility that spacetime is fully continuous, with no minimum length scale.

\n\n\n\nI'm not entirely sure what you mean by "gravity related objects".

\n

I think they mean "gravitationally bound."

\nThe CMB is the furthest thing you can see *back in time*. The CMB is the remnant of the recombination process that took place everywhere at once, so by itself, it doesn't say anything about whether the universe is finite or infinite.

If you also take into account inflation that caused regions to become causally disconnected, then it allows for even a finite universe to be bigger than the observable universe.

\nYou are thinking of the extrinsic curvature. GR deals with intrinsic curvature, which for the 3-torus is zero everywhere.

\nAn infinite universe can be falsified in principle if it is determined that the universe has a finite topology. Unfortunately, it seems most likely that the whole universe is bigger than the observable universe (although there are some possible topologies that can still be detectable at the sub-horizon scale with more precise data) so determining the exact topology would be extremely difficult.

\n\n\n\nIf it did curve back on itself, giving it finite volume, then it would have a detectable positive curvature.

\n

Not necessarily, for example, the 3-torus has zero curvature and is also periodic.

\n\n\n\nBut from what we can see, the curvature of the universe is 0 (or very close to 0). So this means that either: the universe is infinite or it’s so so large we struggle to detect any curvature.

\n

Even if the universe has exactly zero curvature, it is not possible to jump to the conclusion it is infinite as it might have a finite non-trivial topology.

\nHomogeneity was indeed, at first, an assumption, but it managed to explain the features of our universe extremely well, but also it was unexplained, which is why the horizon problem was pointed out in the first place and why inflation was proposed.

\n\nAs previously explained, if the universe is infinite, then inflation can't guarantee homogeneity throughout all of space, so to argue for an infinite universe, one would need to either abandon the Copernican principle and come up with a new metric that describes the whole infinite universe, or believe in a highly improbable coincidence. On that basis, I would argue that the idea of an infinite universe should at least be less preferable to a finite one.

\nIf there are inhomogeneous regions beyond the observable universe, I don't see how that can be reconciled with the Copernican principle from which the FLRW metric is based on. If all of an infinite universe is homogeneous, then it can only be through an unimaginably extraordinary coincidence.

\nI think an infinite universe has an issue with the horizon problem, even taking inflation into account. The horizon problem is solved by requiring that whole universe was causally connected (which implies a finite universe given the finite speed of light) when it reached thermal equilibrium and then the exponential inflation caused regions to be causally disconnected whilst maintaining thermal equilibrium, which explains the homogeneity observed everywhere.

\n\nBut if the universe is infinite, then it always has been infinite, which means it has always had causally disconnected regions. There couldn't have been thermalization everywhere if there were regions that were never in contact with each other, and the observed homogeneity would remain unexplained, and the horizon problem remains.

\n\n\n\nThe universe was always infinite in size.

\n

How is the horizon problem (even with inflation) dealt with in an infinite universe if there would have always been causally disconnected regions that would prevent thermalization and therefore homogeneity?

\n\n\n\nif the Big Bang had been luminous, we would expect to be able to look far enough to see distant parts of the universe “activate” and be exactly where they were the moment the Big Bang occurred. This would mean that those distant areas existed at the moment of creation, and the universe could never have been the size of a proton.

\n

It sounds like you mean to say that there already existed distant parts in space at the moment of the big bang and the light from big bang would travel from some origin to then reach those distant parts that would then "light up" in a way?

\n\nIf I understood you correctly, then you are imagining the big bang incorrectly. If there was a singularity or something singularity-like, then space itself was created at the moment of the big bang and expanded isotropically from zero or a extremely small size to what it is today. There wouldn't have been any distant parts of space that received the initial light after the big bang as the whole universe would have always been filled with matter and energy as it grew.

\nThere are finite topologies that have no boundaries.

\nIf it increases in mass just a little bit to become heavier than the neutron, then protons in atoms would start turning into neutrons via electron capture, and things would spontaneously turn into other elements.

\nIf true singularities are possible in nature, and if the universe itself was any non-zero volume at the big bang, then every single point in space would need to have infinite mass to make sense of the FLRW metric having infinite curvature at t = 0. But it is impossible to dilute infinite mass through expansion, let alone at every point in space, and needless to say, the universe as we know it couldn't have formed. Therefore, the universe having a finite mass compressed into a point in accordance with the FLRW metric is the more probable scenario.

\n\nOne might object to the assumption of the existence of singularities because quantum gravity might reveal that singularities aren't possible in any circumstance, which indeed is a possibility, so if we assume for a minute that is the case, then the only way there could be infinite mass and have a universe that looks like ours is for space to be infinite as well, which leads to another objection to the possibility of infinite mass, which is that an infinite size universe, and therefore infinite mass, causes the horizon problem to persist, even with inflation.

\n\nIf the universe is infinite, then it has always been infinite, so there would have always been regions that are causally disconnected from each other. The horizon problem is the fact that causally disconnected regions have the same temperature despite the fact it is not possible that there could have ever been any interaction between those regions so that they could have achieved thermal equilibrium with each other. Inflation solves this problem because it only happened after the entire universe came into thermal equilibrium whilst all of it was causally connected (which already implies it is finite given the finite speed of light), and inflation then caused regions to be causally disconnected. However, inflation can not solve this problem in an infinite universe because if it has been always infinite, then there have always been causally disconnected regions and therefore the infinite universe should not be isotropic and homogeneous except through extremely improbable initial conditions.

\nIt is implied by the Copernican principle. If there isn't infinite matter, then space becomes empty after a certain point, violating homogeneity. The only way you can save homogeneity in this case is if all matter is separated by infinite distances, which is obviously what isn't observed.

\nThe Friedmann equations of the standard big bang model predict infinite density, but it is true that it doesn't incorporate quantum mechanics, so we don't know whether there might be some unknown repulsive effect that can win over gravity at certain scales, but at the same time it could also be the case that gravity still overcomes any quantum mechanical effects anyway, like how it overcomes the Pauli exclusion principle in the formation of neutron stars and black holes.

\n\nThe discussion of the initial singularity as currently described by theory is a bit speculative, but quantum gravity is an even deeper layer of speculation, so that's why I am talking in terms of the physics as currently understood, but of course, it all should be taken with a grain of salt until a unified theory is discovered.

\n\n\n\nI'm using 'infinite' in a hand wavy way to mean 'we are unable to even describe how dense it was'.

\n

Ah, I see, but there's still the issue that current theory says the metric tensor was infinite at the big bang, so if there was any non-zero volume of space at the big bang, then every point would need to have infinite mass to ensure there is infinite density to cause the metric to be infinite. This issue can be resolved by having a finite mass in zero volume, as you mentioned.

\nThe discussion is within the context of the contemporary big bang theory, which does predict infinite density. You might be confusing it with the hot big bang theory, which just says "hot and very dense," which is another thing that happened after the expansion of the initial big bang.

\n\nYes, it is possible quantum gravity *might* say something different about the initial singularity, but we are just working with what we have so far.

\n\n\nan infinite amount of space was contained in a singularity

\n\nnow its an infinite amount of space that is not contained in a singularity. its an infinite amount of space that is expanding in all directions

\n

That's not compatible with the behaviour predicted by the Friedmann equations. It says the universe was initially singular with a scale factor of zero. This is incompatible with the usual assmption that the universe's topology is Euclidean space, but with your scrunched-up-space model, it can make sense for an infinite universe to have a zero scale factor at one point, but the solutions of the Friedmann equations demand a smooth and finite evolution of the scale factor, so the infinitely scrunched-up-space would need to "unravel" at a finite rate, so at any time, the universe would be finite whilst it is unravelling. The behaviour of the evolution of the scale factor does not allow the universe to suddenly become infinite from a scale factor of zero.

\nThe quantity of matter each space can hold is not the problem, it's the dynamics of the expansion of space from finite to infinite.

\n\n\n\nAn infinite amount of space was super compact into a singularity.

\n\nThen the big bang happened, and that same infinite amount of space expanded rapidly and is still expanding.

\n

Unless the derivative of the scale factor was infinite at some point, then this scrunched up infinite space is still spreading out, which means the universe is finite.

\nThere is no perspective at all for any observer travelling at the speed of light, so it is not possible to judge your speed from that frame of reference.

\nBut if space is infinite and it is infinitely dense at every point, then it has infinite mass at every point and no amount of expansion can dilute infinite mass.

\nYou can calculate the half-life from the tunnelling probability through a potential barrier equal to the Coulomb potential. Here is an example of a calculation that demonstrates the procedure with a discussion of its applicability.

\nMathematical Methods of Classical Mechanics by V. Arnold.

\n\n\n\nWhy the hell does a lone neutron decay in 15 minutes, but last forever inside a stable isotope?

\n

Neutrons decay in isolation because it is more energetically favourable for one of its down quarks to transform into an up quark that has lower mass.

\n\nInside nuclei, because of electrostatic repulsion, protons have bigger energy levels than neutrons. For a neutron to decay, the nucleus needs to end up in a lower energy state than before the decay, but a newly-transformed proton would have to occupy a higher energy state than it did as a neutron, and it can't do that spontaneously.

\nSenna may not have exactly reached Prost's wins, but Prost was in F1 for 3 more seasons than Senna was and only had 10 more wins. Prost himself was sure Senna would have exceeded his win tally had he not died.

\n\n\n\n\nIt did feel young when he died at 34, but that is very much close to age of retirement and new talent outperforming the old one.

\n

There were no signs of Senna slowing down. He was even the favourite to win the 1994 season. Prost himself managed to retire at the top when he was 38, so age would unlikely have been an issue.

\n\n\n\n\nAnd scoring system was pretty bad back then.

\n

It made perfect sense to reduce the influence of bad luck due to the bad reliability of those days and to allow drivers to push more.

\nI made her marriageable with the Proteus mod, and we lived happily ever after.

\n\n\n\n\nIt seems like she would be pissed off at the db.

\n

My err, high speech woo'd her, and she fell for me, yeah.

\nWhen people say "Big Bang" they mean one of two things; the initial singularity and the "hot" big bang.

\n\nWhether there was an actual initial singularity is still an open question that will only be answered when a theory of quantum gravity is discovered, but as of now, general relativity says there was a singularity, and it wasn't an explosion, but rather an isotropic expansion.

\n\nThe hot big bang refers to the reheating period after inflation where the inflaton field decayed and all its energy was transferred into matter and energy and indeed the universe was still very hot and dense at this point. This is the earliest time that current physics can very confidently describe the processes that happened in the early universe, so it is of the most interest in Big Bang discussions.

\nBut if the plane itself is moving, then it is not replicating the hypothetical situation. If the conveyor exactly matches the wheel speed in the opposite direction, then the plane would not move relative to still air, and there would be no lift.

\nHere is the video. You clearly see the plane moving relative to the ground and through the air and the "conveyor" didn't work as the hypothesis is described.

\nIt was a flawed experiment. The plane still moved through the air.

\n\n\n\nTo the best of all our measurements and theory the universe is, will always be, and has always been infinite in spatial extent.

\n

It is not possible to conclude that. There are also finite topologies consistent with measurements.

\n\n\n\nonly that all of our measurements and theoretical descriptions are consistent with the curvature constant of the FLRW metric being equal to zero.

\n

That is different from saying that measurements suggest the universe is infinite, like you initially said, because there are other possibilities with zero curvature. There is nothing to suggest one way or the other.

\nThat also applies to other things. For example, measurements can't prove photons are massless, only set an upper bound on their mass due to measurement limitations, but physicists still assume it is massless. If a theory makes a claim and it is within measurement uncertainty, then you just roll with it until proven otherwise.

\nThe cosmological models that best describe our universe assume isotropy and measurements have not detected any net angular momentum outside of measurement uncertainty.

\n\n\n\nBut I’d say that there is no particular reason to think that they do exist. And if they do, what is it?

\n

There are no known forces in nature strong enough to resist gravitational collapse after a certain point. Unless quantum gravity reveals a new force or mechanism strong enough to repel gravity, then matter would have no choice but to collapse to a zero size point.

\nFor all we know, they could be. It would be nice mathematically to not have to deal with them, but nature doesn't have to conform to certain behaviours for our convenience. It is unknown exactly how physics behaves in extremely high energy densities. It could be the case matter and energy phase transitions into a state that allows collapse to a point, or there could be quantum effects that cause repulsion at a small enough scale.

\n\n\n\nCertain solutions to GR have singularities in them but you can rewrite those solutions to not have them as well.

\n

Not always. Some singularities are true singularities and can't be removed by a coordinate transformation.

\nWe don't know how physics behaves above a certain energy density, so we are not sure whether matter turns into some unknown state at high enough densities that allows it to collapse to an infinitely dense point or whether there are quantum effects that can repel gravitational collapse.

\n\n\n\n\nSecondary question. After crossing the event horizon, could there be a layer of intensly bright light from what is essentially photons that happen to be in a stable orbit?

\n

Photons can only form stable orbits at a radius 1.5 times the Schwarzchild radius, so it would be outside the event horizon.

\n\n\n\nit is built on top of general relativity. the notion that space is a fabric. that particles cannot move through this fabric because it is a solid.

\n

General relativity does not claim space is equivalent to a solid fabric. The use of fabric is just an analogy that helps laypeople understand the geometric nature of gravity.

\n\n\n\n\nthat e=mc

\n^{2}and particles can readily convert to waves and waves to particles.

Neither side of the equation makes a claim as to whether something is a wave or a particle since both forms can possess energy.

\n\n\n\n\nit interferes with itself as a wave. it stops at the final destination. as it stops is converts back into a particle again by e=mc2.

\n

How does this explain the photons changing its behaviour from a wave to a particle when a detector is placed at the slits? The photon travelling from the slit to the detector as a particle contradicts the claim that particles can't travel through space.

\nThe Hawking-Hartle state predicts that there was space before time emerged. It requires time to have an imaginary component, and it isn't known how to physically interpret imaginary time, so this model is speculative.

\n\n\n\n\nWhat implications would this have for the Big Bang?

\n

In the Hawking-Hartle model, the universe would have started a finite time ago in a non-singular state.

\nIt sounds like the model you came across is the Einstein-de Sitter universe, which assumes flat space and a zero cosmological constant. In this model, the rate of expansion tends towards zero as time tends to infinity. What this means is that as time goes by, the expansion rate will keep going down towards zero, but it will never reach zero as time can't actually reach infinity.

\n\nSince this model was proposed, it has been discovered that the cosmological constant is actually non-zero and positive, meaning the universe's expansion rate will keep increasing indefinitely.

\nThe equations of general relativity say the universe is expanding intrinsically, meaning it is not expanding into anything because there is no reference outside of our universe because there is no spacetime there.

\n\nIt is possible that the universe could be embedded into some sort of space, but it is not necessary for the equations to work.

\nIt is ChatGPT garbage. One of the tells is the use of the word "interplay," which ChatGPT likes to use way more frequently than people do, and as a result, it appears quite commonly in these types of posts.

\nSIX whole points!!!

\nThe 3-torus is isometric to Euclidean space and thus flat.

\nThere is not enough evidence yet to determine the overall topology of the universe, but there are indeed many non-trivial topologies that are consistent with measurements. See this paper for details.

\n\n\n\nisometry requires preserving not only the distances, but also the global geometric properties, such as being infinite or finite.

\n

Isometries do not necessarily have to be global. There is such thing as local isometries.

\nActually, I want to see what shenanigans look like on cosmic scales.

\nBlack holes are formed from the matter with those properties and retains them.

\nThey probably make terrible GPS then. The Hafele–Keating experiment proved the need to correct for relativistic effects as well before the GPS was first deployed.

\nOkay let's say I'm buying it. What is a 3D surface?

\n\nA 3D surface would be the result of a sweep of a 3D shape across a 4th dimension, which would then enclose a 4D volume, just like you get a 2D surface that encloses a 3D volume when you sweep a 2D shape across a 3rd dimension.

\n\nIt might be confusing because the terms "surface" and "volume" get recycled, but it would be inconvenient to make terms for the analogue of surfaces and volumes in higher dimensions, so the sweep of the lower-dimensional object is called the "hypersurface" and the enclosed volume as "hypervolume". But for every combination of n-1 and n dimensions, there's the analogue of 2D surfaces and 3D volumes.

\n\n\n\n\nDid somebody suggest some 2D hyperedge? Or a 1D hyperpoint?

\n

The concept of volumes, surfaces, lines and points already had unique names for convenience because of the dimensionality of our world, but if we were lower-dimensional beings, there's no reason we couldn't use those terms you mention if we never came up with words for surface and volume. It is the same concept.

\nYour conclusion that there can be no more than 3 dimensions is circular because your example of constructing shapes assumes a 3D space. If you lived in a 4D space, you would have an extra degree of freedom to be able to construct 4D objects. This is all well-defined mathematically with no contradictions.

\nThe extra dimensions physicists talk of come from string theory, which is purely hypothetical at this stage, but these extra dimensions are compactified, meaning that they would only be noticeable at very, very small scales. At everyday scales, you would only notice the 3 spatial dimensions you are familiar with.

\n\nThere is no evidence for compactified dimensions currently, but if string theory is true, those extra dimensions are required for it to be a consistent theory given its assumption of matter being 1D strings.

\nYou are implicitly assuming a 3D space because of your use of 2D surfaces. If you want to construct a 4D shape, for example, you construct it by sweeping the volume of its hypersurface, which would be the 3D shape. You can't jump from 2D to 4D like that, which is where you think the contradiction comes from.

\n\nI have seen you comment elsewhere that you don't believe a 4D object would have a 3D surface, so it is probably futile trying to explain this concept further, but if you believe you can create a 2D plane from sweeping a 1D line perpendicular to itself, and a 3D volume from sweeping 2D plane, then you can do the same process by sweeping a 3D object along an extra dimension to get a 4D object. It is the same process as the previous dimensions. There's nothing special about a fourth or higher dimension that would prevent you from continuing this pattern. You just sweep the shape of the immediately lower dimension into the new higher one.

\nIt means that when you measure angles, it doesn't deviate from what you expect in an Euclidean plane. For example, if you measure the total angle in a triangle in a flat geometry, the angles add up to 180 degrees, but in closed and open geometries, the total angle will be more and less than 180 degrees respectively.

\nDue to the way time progresses, you can't reach "eternity", let alone have something after it.

\n\nWhen people say the universe is future eternal, it means time elapsed will just get bigger and bigger, but it will never actually reach eternity because that's like trying to count to infinity.

\nWhy? He has been earning millions while failing at his job.

\n\n\n\nat the expense of apparently no extra drag

\n

How is not having more drag a bad thing?

\nThis website has books on special and general relativity plus other physics topics, and they are freely available.

\nOP is the bottom Winnie for not understanding the reference.

\n\n\n\nLike if space was a floating 2d grid, I can simply distort the grid and then modify the shape of the space and it wouldn't be visible from the 2d perspective but would have real effects.

\n

What you describe is extrinsic curvature, which requires the space to be embedded in a higher dimension. Gravity is described by intrinsic curvature, which does not require higher dimensions.

\nIt depends on the context. If you are talking about the actual beginning of the universe, then it's t=0. If you are talking about reheating after inflation when the inflaton field decayed, then that's the "hot" big bang at t=10^{-33.}

\n\n\nI genuinely don't understand why it had to start from a 0 dimensional point that became an infinite plane suddenly.

\n

It doesn't necessarily have to become infinite all of a sudden. Using the observations that say the universe is geometrically flat, people usually jump to the conclusion that the universe has the topology of Euclidean space, which is infinite, but there are other topologies that are also geometrically flat but are finite in extent, like the 3-torus for example, which makes the dynamics of the universe's expansion predicted by the Friedmann equations make sense. No-one knows the overall topology of the universe for certain, but if general relativity predicts a smooth expansion from a 0-dimensional point, then it would make sense to discard topologies that are necessarily infinite.

\n\n\n\n\nWhy can't it just be that the universe was always infinite in scale, and the big bang simply began as a state of uniformally high energy that rapidly expanded.

\n

The Friedmann equations say that the space of our universe was created at the Big Bang. It does not say that there was pre-existing space that our universe started expanding in. I have never seen a configuration of an infinite universe with uniform high energy density discussed in literature.

\n\n\n\n\nThe universe expands into itself but has always been and is still always infinite despite that, so rewinding time wouldn't show us the universe gradually shrinking to a point, so why is there a need for a point at all at t=0?

\n

If you assume the universe is infinite, then it is true that it doesn't make sense for the universe to have been a point at some time in the past. But the Friedmann equations say it was a point, so as mentioned before, it would make more sense in this case to not assume a topology that's necessarily infinite.

\n\nIt is worth noting that general relativity does not incorporate quantum mechanics, so it is still an open issue of whether the initial singularity was a true 0-dimensional point or something close to it. I think it is highly unlikely quantum gravity will reveal that the universe is infinite after all, because there needs to be correspondence between quantum and classical theories, and general relativity works too well to be overturned that radically.

\n\n\n\nMultiple sources state a key assumption for ΛCDM is that the universe is flat

\n

The fact that the universe is flat is not in question, but as I have already mentioned, a flat geometry does not necessarily imply an infinite universe. Here is an excerpt from the paper I linked: "In 1924, Friedmann pointed out that Einstein's equations are not sufficient for deciding if space is finite or infinite: Euclidean and hyperbolic spaces, which in their trivial (i.e., simply-connected) topology are infinite in extent, can become finite (although without an edge) if one identifies different points -- an operation which renders the space multi-connected."

\n\n\n\n\nI did research on this afterwards in the past which led me to sources that include NASA

\n

The author of the NASA article is also mistaken in thinking flat geometry automatically implies infinite space.

\n\n\n\n\nMore importantly the cosmological principle necessarily assumes the universe is flat

\n

It doesn't. The cosmological principle only assumes the universe is homogeneous and isotropic. From then, you can deduce the FLRW metric, which allows for the 3 types of geometries; closed, flat, and open.

\n\n\n\nInfinite size is not necessary to explain the big bang, but not only is it compatible with it, but the universe being infinite, though always acknowledged to be potentially not the case, is consensus according to my research.

\n

Which sources did you use for your research? If it is forums such as Reddit, there are common misconceptions that are spread around about cosmology because it seems most people are not aware of the topological subtleties. I have searched through several books on gravitation and cosmology, and I am yet to find one that entertains the possibility of the universe being infinite at the Big Bang.

\n\n\n\n\nCurrently, we have a number of measurements that, to the best of our limited ability, indicate the universe is an infinite Euclidean plane.

\n

Those measurements only relate to local geometry and sheds no light on global topology. General relativity is a metric theory, meaning it only describes space point-to-point and not overall. The measurements do say the universe has a flat geometry, but there is no reason to conclude that the universe is therefore an infinite Euclidean plane. As mentioned before, there are other topologies that are equally as compatible with the flat measurements and avoid the issue you pointed out in your original post. See this paper that explains the possibilities of non-trivial topologies.

\n\n\n\n\nAlso, the universe being infinite is actually required by some models, like ΛCDM.

\n

ΛCDM makes no claim about global topology either, only local geometry, so it doesn't require an infinite universe.

\nYour "paper" being something ChatGPT came up with, made obvious by the fact that it uses end-of-line hyphenation that you left in the middle of the lines when you pasted it here.

\n\n\n\nI know as far as we know the speed of light is constant, but what proves that?

\n

Originally, the Michelson-Morley experiment failed to detect any change to the speed of light predicted by aether theory and since then, there have been much more accurate variations of the experiment. Here is one of the most accurate experiments to date that failed to detect any variation down to a few parts in 10^{-16} .

\n\n\nMy question is: why can't we just flip around our time convention, and say that rather than the big bang being t=0, as t trends towards infinity for moments in time distant from the big bang, why cant we denote the big bang as t=infinity, and say that time tends to 0 as you move away from the moment of the big bang.

\n

How would this work for making calculations? Say for example you want to know how something in the universe has evolved since the Big Bang until today. You know it has been 14 billion years since the Big Bang, so you need to integrate the equation of the thing you are interested in with respect to time. One of the integration limits has to be the big bang and the other has to be the time since the big bang, so the first limit is infinity by your convention and the other has to be infinity - 14 billion years = infinity??? So you integrate from infinity to infinity? If you want to choose any other interval to integrate your equations in between, you will have to integrate from infinity to infinity no matter what.

\n\nYou simply can't run a clock backwards from infinity. When is the crossover into a finite number? Never. You just get nonsense from treating infinity as an actual quantity.

\nTime itself is defined at the big bang because the solutions of the Friedmann equations include t = 0 in its domain. Only when you apply the solutions to other quantities such as density and temperature do you get divergences. Only quantum gravity can say what truly happened at t = 0.

\nIf you use the reciprocal as a transform, you still run into issues because at the big bang, t = 1/0 = undefined.

\n\n\n\nflat curvature + isotropy naturally implies that the universe be spatially infinite.

\n

Not necessarily, there are various topologies that are isometric to infinite Euclidean spaces but are finite in extent.

\nYou can look into biophysics and see if that suitably combines your interests.

\n\n\n\ncan anyone tell me what was there before the beggining and how we came from nothing

\n

No-one knows for certain. Current theory says that space and time was created at the big bang, and it doesn't predict that there was anything before it. It also doesn't say what triggered the big bang. Only when a theory of quantum gravity is discovered we might know for certain if there was anything before the universe or not and what caused the universe to begin to exist.

\nNo, they are keeping him because he has prodigious pace very few drivers have.

\n\n\n\nNowadays in cosmology there is no such thing as the "big bang theory". You won't find scientific publications in cosmology about the big bang theory, instead you find publications about the "standard cosmological model" aka "cold dark matter model"

\n

Cosmologists now are mainly focused on trying to resolve some discrepancies between current observation and the predictions of the ΛCDM model, and the initial big bang itself is not pertinent to that, and the maths predicting it is well established, so it does not need further research at this point as it will not help explain anything about the current structure of the universe and physics currently is not adequate to fully conclude whether or not there was a initial singularity in the first place.

\n\n\n\n\nThat's a bit different than it being "explicit" about a singularity

\n

It is explicit in the sense that a singularity is predicted directly from both the FLRW metric and the Friedmann equations, which are the basis of the big bang model, as well as singularity theorems. I am aware some sources like Wikipedia use the word "extrapolation," which makes it sound like an educated guess, but it is a bit misleading as a singularity is predicted as part of the solutions which include t = 0 in their domain. When "extrapolation" is used, the author really means "retrodiction."

\nThat's correct, but the person above is saying that the big bang theory doesn't say the universe came from a singularity, when the theory does explicitly say it.

\n\n\n\nThe singularity is not a real thing. Many people think that the Big Bang says the universe came from one, but it doesn’t.

\n

The big bang theory does say the universe came from a singularity. Here is an excerpt from my GR book by Wald:

\n\n\n\n\nGeneral relativity makes the striking prediction that at a time less than H

\n^{-¹}ago, the universe was in a singular state: The distance between all points of space was zero; the density of matter and the curvature of spacetime was infinite. This singular state of the universe is referred to as the big bang.

Whether or not the universe was actually singular at t= 0 is an open question that only quantum gravity will answer, but it is wrong to assert with confidence \nthat there definitely was no singularity.

\n\n\n\n\nWhat the Big Bang Theory does say is that the universe was much more hot and dense in the distant past.

\n

You seem to have got the big bang confused with the *hot* big bang, which is what describes the universe after reheating when the inflationary period ended, when the universe was indeed still extremely hot and dense, but the known physics of today can describe the universe at this point with confidence.

\n\n\nThey just tick and we call the number of ticks time.

\n

That's how you measure time. Clocks don't tick unless a certain amount of time has passed.

\nReal time is what you can measure with a clock.

\nI use companions so I don't get lonely 👉👈

\nThat's what made me reach Q3!

\nWhy do you think he is suppressing his true beliefs just to work at those institutions? He works at those institutions because they share the same beliefs.

\nThere is evidence that the universe is finite in time. Its cosmological age is 13.8 billion years. There is no evidence of anything existing before that.

\nWe don't even know if space has a minimum non-zero length scale. If it does, its granularity has to be smaller than 10^{-48} m or 13 orders of magnitude smaller than Planck length, according to measurements. So if you just automatically choose Planck length as the minimum length scale, your hypothesis is already at odds with observations.

"Ooh, I have a really good recipe of pancakes..."

\nHe was told that rain was going to immediately come down when it didn't.

\nMost drivers, including his teammate, got told that rain is predicted soon, and they weren't told that it was going to rain heavily immediately. Leclerc, for some reason, was told it was going to rain heavily in the next lap. It would have made perfect sense to pit under that information, but his engineer seems to have misinterpreted the weather radar.

\nWhat is he supposed to do when his team are the ones with the weather radar feeding him inaccurate information? Is he supposed to assume they are lying to him every time?

\nWhat has that got to do with being fed wrong information at that moment?

\nThe team gave him inaccurate information.

\n