Other Worlds And Our Laws Of Physics

Do the laws of physics apply on other worlds? This question has been asked by physicists and philosophers alike, and the answer is not straightforward. Some argue that the laws of physics are universal and hold true everywhere, while others suggest that they may vary depending on the environment or even change over time. For example, gravity has different strengths on Earth and the Moon, but this is simply an environmental difference. The laws of physics, as we understand them, are expected to be the same throughout space. However, some cosmological theories, particularly those involving the concept of a multiverse, allow for the possibility that the laws may differ in different regions of space.

The Standard Model of particle physics, with its handful of ingredients, seems to suggest that our universe is one of many possible worlds. This raises questions about why this particular combination of particles and forces underlies the structure of our universe. Additionally, the model includes numerical constants, such as the mass and charge of an electron, that seem to lack any deeper meaning. While physicists generally agree that the laws of physics have remained constant since the Big Bang, there is room for speculation about whether they could change in the future or vary in distant corners of the cosmos.

The idea of mutable laws of physics leads to intriguing possibilities, such as the existence of multiple recipes for the same physical system in quantum physics. This has sparked a shift in perspective, with modern physicists embracing the vast space of possibilities and aiming to understand its overarching logic. While string theory, a candidate for a theory of nature, has no free parameters, its space of solutions is incredibly vast and complex. This complexity presents challenges in exploring the landscape of physical models and understanding the underlying rules that govern our universe and potentially others.

Laws of physics are statements that hold true everywhere and everywhen

The laws of physics are often defined as statements that hold true everywhere and everywhen. This is a philosophical stance, and one that is not universally agreed upon.

The laws of physics are expected to be the same throughout space, and if they were found not to be, it would indicate that the laws as we know them are not fundamental. Physicists do try to test this experimentally, and so far, all observations have been consistent with the idea that the laws of physics are the same everywhere.

However, some cosmological theories, particularly those that fall under the "multiverse" theory, allow for the possibility that the laws are different in different regions of space, although generally only on scales much larger than what we can observe. In these theories, the fundamental laws are the same everywhere, but the way the universe evolved in different regions is so different that the laws appear to be quite different.

For example, when the universe was very young and hot, it probably underwent various transitions, similar to phase transitions, in which an initially symmetric state became less symmetric. There may have been different ways that the final state could have turned out, and they may have been quite different—for instance, with completely different sorts of particles existing. There could be different regions of the universe in which the symmetry breaking went different ways, in which case the "apparent" laws would be different in those regions, but probably only on scales much larger than what we can observe.

Another example is the mass of an electron, which was zero until the Higgs field turned on a tiny sliver of a second after the Big Bang. This is an example of a constant that has changed over time.

The laws of physics are also dependent on our human perception. If our perception were different, the rules—and even the laws of physics—would be different. For example, the laws of thermodynamics are based on our sense of time. If our sense of time were different, the order of events would be different, and the laws of thermodynamics would not hold true.

The laws of physics are expected to be the same throughout space

However, it is important to note that the laws of physics, as we understand them today, may not be the fundamental laws that govern the universe. For instance, the laws of classical mechanics only apply to small velocities and macroscopic objects, while the laws of general relativity and quantum mechanics are expected to be limited by quantum gravity. As our understanding of the universe evolves, we may discover new laws that supersede or modify our current understanding of physics.

Furthermore, while the fundamental laws of physics are expected to be universal, the specific values of physical constants may vary in different regions of the universe. For example, the mass of an electron was zero until a tiny sliver of a second after the Big Bang when the Higgs field turned on. This suggests that physical constants can evolve over time.

Scientists have conducted experiments to test whether the fundamental constants of physics change over time or space. For instance, studies of natural nuclear reactors in the Oklo region of Gabon, which provide a "radioactive fossil" of what the rules of nature looked like two billion years ago, have been used to examine whether the fine structure constant, a dimensionless constant that bundles several other constants, has changed over time. While some studies suggested a change in the constant, more recent analyses found results consistent with no shift, indicating that if there is a change, it is extremely subtle.

In summary, while the fundamental laws of physics are expected to be the same throughout space, the specific values of physical constants may vary, and our understanding of physics may evolve as we discover new laws or modify existing ones.

The laws of physics are not expected to change over time

For example, the laws of conservation are like book-keeping rules that are used to keep track of what's entering, exiting, and accumulating inside a system. The fundamental rule is that you can't remove more than what was there to start with. If this rule were to change, it would mean that there is a cheat that allows the rules to be avoided. However, this would cause the system to collapse.

Another example is the idea that the brightness of an incoherent light source scales as 1/(distance to the light)^2. For this law to be different in another location, it would mean that the area of a sphere is not equal to 4 x (pi) x r^2, which would mean that space in that region was not three-dimensional, a result that is unphysical.

Additionally, if the laws of physics were to change, it would mean that effects could be observed before their causes, and concepts like energy conservation, time measurement, and arithmetic would become meaningless.

While it is possible that the laws of physics could be different in other regions of the universe, this would generally only be on scales much larger than what we can observe. In such cases, the truly fundamental laws would still be the same, but the way the universe evolved in different regions would be so different that the apparent laws would seem completely different.

Furthermore, while the mass of an electron was zero until the Higgs field turned on a tiny sliver of a second after the Big Bang, this is not considered a change in the laws of physics themselves, but rather a change in a numerical constant. Physicists can make solid, testable predictions about how variations in numerical constants should affect the results of their experiments, and some theories can accommodate changing constants.

In conclusion, while it is possible that the laws of physics could change in some distant corner of the cosmos, this would be extremely bizarre and there is currently no framework from which to investigate this question. As far as we can tell, the laws of physics are not expected to change over time.

The laws of physics are not expected to change from place to place

Furthermore, Noether's theorem states that if there is a symmetry in a system, there is also a conserved quantity, and vice versa. For example, rotational symmetry implies the conservation of angular momentum, and translational symmetry implies the conservation of linear momentum. As conservation of linear momentum has been measured, this means that the laws of physics do not depend on position and are therefore expected to be the same everywhere in the universe.

While it is true that the mass of an electron was zero until a tiny sliver of a second after the Big Bang, and that the laws of physics may be different in other universes, as far as physicists can tell, the laws have been the same since the Big Bang, and every observation has been consistent with the laws being the same everywhere.

The laws of physics are not expected to change from time to time

For example, gravity has different strengths on Earth and the Moon, but this is merely an environmental difference. The laws of physics are also not expected to change over time. The cosmos has been playing by the same rulebook since the time of the Big Bang.

However, some physicists argue that the laws of physics could be different in other parts of the universe or in the distant past or future. For instance, the mass of an electron was zero until a tiny sliver of a second after the Big Bang when the Higgs field turned on. Some constants may also change over time, such as the gravitational constant, which some theories suggest gets weaker as the universe ages.

Nevertheless, the current consensus is that the laws of physics are universal and do not change over time or space. Any changes in physical constants or laws would be extremely subtle and unlikely, and all observations so far have been consistent with the laws of physics being the same everywhere.

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