# 100% certain physical laws are same in other galaxies?
**URL:** https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230
**Category:** Factual Questions
**Created:** [October 13, 2014, 7:12pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230 "2014-10-13T19:12:23Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Robert163](https://boards.straightdope.com/u/Robert163)
#### Post date: [October 13, 2014, 7:12pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/1 "2014-10-13T19:12:23Z")
Are we 100% certain that physical laws function exactly are same in other galaxies as they do in our own?
---
### Author:  [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)
#### Post date: [October 13, 2014, 7:18pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/2 "2014-10-13T19:18:18Z")
Science is not really into the “100%” thing. Science is about the “So far, what we have seen fits with this model” thing.
The parsimonious expectation is “Yes” and if observational evidence require the laws to be modified, then they will be.
Remember, a “Law” is just a description, not an explanation. The Laws of Gravity describes how two masses attract each other, it does not address why that attraction exists.
---
### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [October 13, 2014, 7:19pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/3 "2014-10-13T19:19:07Z")
> [@Robert163](#):
>
> Are we 100% certain that physical laws function exactly are same in other galaxies as they do in our own?
We’re not 100% certain of anything. But things like emission lines being the same no matter what distance the light has travelled is very strong evidence physical laws are genuinely universal.
---
### Author:  [@Ornery\_Bob](https://boards.straightdope.com/u/Ornery_Bob)
#### Post date: [October 13, 2014, 8:18pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/4 "2014-10-13T20:18:57Z")
The reason that natural laws are called “laws” is that they cannot be broken.
For example, the harder you throw a ball, the faster it goes. This isn’t a scientific theory, it’s something built into how the universe works. We can write this mathematically as f=ma, and we call it a law of motion, but that’s all just window dressing, at it’s core, it’s just a description of how things work.
So do balls go faster when you throw them harder in another galaxy? It seems reasonable to assume so and to date we’ve never observed anything going on in distant galaxies that would cause us to disbelieve the assumption.
---
### Author:  [@Smeghead](https://boards.straightdope.com/u/Smeghead)
#### Post date: [October 13, 2014, 8:21pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/5 "2014-10-13T20:21:30Z")
“100% certain”, in science, just means “until we make an observation that proves it wrong.” In that sense, yes, we’re 100% certain.
---
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [October 13, 2014, 8:31pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/6 "2014-10-13T20:31:09Z")
Well, we’re not really sure what physical laws apply at the singularity in a black hole.
---
### Author:  [@Lumpy](https://boards.straightdope.com/u/Lumpy)
#### Post date: [October 14, 2014, 12:14am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/7 "2014-10-14T00:14:43Z")
I’ve repeatedly read that Relativity implies that the laws of physics have to be the same throughout the observable universe- though I don’t know why. Anyone?
---
### Author:  [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)
#### Post date: [October 14, 2014, 2:04am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/8 "2014-10-14T02:04:00Z")
Lumpy, you may be thinking about applications of Noether’s theorem. The fact that physical laws are invariant with respect to spatial translation (which is equivalent to the laws of physics being identical at all places in the universe) implies the conservation of linear momentum. Similarly the invariance with respect to rotation of physical laws means that angular momentum is conserved and the invariance with respect to time of such laws implies the conservation of energy:
> **[Noether's theorem | Applications](https://en.wikipedia.org/wiki/Noether's_theorem#Applications)**
>
> Application of Noether's theorem allows physicists to gain powerful insights into any general theory in physics, by just analyzing the various transformations that would make the form of the laws involved invariant. For example:
> 1.Invariance of an isolated system with respect to spatial translation (in other words, that the laws of physics are the same at all locations in space) gives the law of conservation of linear momentum (which states that the total linear momentum of an isolated system is...
What happens in science is not really a 100% certainty of anything. Laws of physics are postulated and then checked for how well they fit the observations we make of the universe. A complete set of physical laws for the universe is considered good if it fits our observations as accurately as possible, explains as many phenomena as possible, and is as simple as possible. Of course, at any point, we may find a new set of physical laws which are more accurate or which explain more phenomena or which can be expressed more simply.
Is it possible that in the future we could find a better set of physical laws in which the laws apply slightly differently at different places? Yes, it’s possible, but that would change many things in current physical theory, so it would really take some considerable evidence to convince scientists that such a physical theory would really be the best one. There have been, for instance, occasional proposed theories in the past few decades which claimed that physical laws change slightly over time. Other scientists have looked at those proposed theories and decided that they don’t offer any improvement in accuracy, completeness, and simplicity, so they have rejected them.
---
### Author:  [@Isilder](https://boards.straightdope.com/u/Isilder)
#### Post date: [October 14, 2014, 2:10am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/9 "2014-10-14T02:10:56Z")
> [@Ornery\_Bob](#):
>
> The reason that natural laws are called “laws” is that they cannot be broken.
>
> For example, the harder you throw a ball, the faster it goes. This isn’t a scientific theory, it’s something built into how the universe works. .
Unless it melts, turns into droplets, and hence stops.
The whole question was ontologically self defeating.
F=mA. but not at particle sizes where quantum effects show.
To answer the OP …
There is evidence for problems with gravity laws, the dark matter is just a fudge factor… its unknown what the dark matter actually is… the mass might not exist, the calculations may be wrong due to a change in the gravity law at large distances, or something. OR the dark matter may be literally dust… what can be done is to survey volumes and work off volumes… but its hard work as the structure of galaxies are hard to estimate … they recently re-evaluated the structure of our own wing of our own galaxy !
---
### Author:  [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)
#### Post date: [October 14, 2014, 2:50am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/10 "2014-10-14T02:50:31Z")
I’ve heard this idea offered as a hypothesis for explaining some observational data. The existence of dark matter and dark energy are the generally used hypotheses for the discrepancy between the observed mass and observed luminosity of other galaxies and the rate of universal expansion. But I read one scientist who said that if some constants like the speed of light could vary by a few percentages over extremely long distances and time periods, this would also account for the observed data. So he suggested that maybe the speed of light was only a “local” constant (for a very large definition of local).
---
### Author:  [@Kimstu](https://boards.straightdope.com/u/Kimstu)
#### Post date: [October 14, 2014, 3:34am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/11 "2014-10-14T03:34:26Z")
Very timely [discussion of scientific “provisionality” by Priyamvada Natarajan](http://www.nybooks.com/articles/archives/2014/oct/23/what-scientists-really-do/?insrc=hpss).
> [@](#):
>
> In a word, the general public has trouble understanding the provisionality of science. Provisionality refers to the state of knowledge at a given time. Newton’s laws of gravity, which we all learn in school, were once thought to be complete and comprehensive. Now we know that while those laws offer an accurate understanding of how fast an apple falls from a tree or how friction helps us take a curve in the road, they are inadequate to describe the motion of subatomic particles or the flight of satellites in space. For these we needed Einstein’s new conceptions.
---
### Author:  [@njtt](https://boards.straightdope.com/u/njtt)
#### Post date: [October 14, 2014, 5:24am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/12 "2014-10-14T05:24:36Z")
There is nothing that special about galaxies that would lead us to expect that physical laws would be different in different ones, any more than you would expect physical laws to be different in different solar systems, or on different planets, or, come to that, in different towns, or in the house next door.
---
### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [October 14, 2014, 11:27am UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/13 "2014-10-14T11:27:33Z")
> [@Isilder](#):
>
> To answer the OP …
> There is evidence for problems with gravity laws, the dark matter is just a fudge factor… its unknown what the dark matter actually is… the mass might not exist, the calculations may be wrong due to a change in the gravity law at large distances, or something. OR the dark matter may be literally dust… what can be done is to survey volumes and work off volumes… but its hard work as the structure of galaxies are hard to estimate … they recently re-evaluated the structure of our own wing of our own galaxy !
Dark matter if a fudge factor for galaxies in general, not for galaxies other than our own, which is what the OP asks. And even if, in some sense it is, as some things are easier to observe in our galaxy and assumptions has to be made for others, the scientific conclusion would still be that our galaxy most likely is like every other, unless there was some pattern to the required fudge factor for different galaxies that couldn’t be explained by the limits of the observational data.
---
### Author:  [@Grrr](https://boards.straightdope.com/u/Grrr)
#### Post date: [October 14, 2014, 12:06pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/14 "2014-10-14T12:06:02Z")
I heard that the Big Bang was able to expand faster than the speed of light because the things that make light travel at the speed it does didn’t exist yet.
It kind of makes me wonder if you could go to the very edge of the universe, would the laws start to fall apart?
---
### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [October 14, 2014, 12:16pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/15 "2014-10-14T12:16:43Z")
> [@Shakes](#):
>
> I heard that the Big Bang was able to expand faster than the speed of light because the things that make light travel at the speed it does didn’t exist yet.
>
> It kind of makes me wonder if you could go to the very edge of the universe, would the laws start to fall apart?
That’s false. The expansion of space isn’t limited by c at all, even now.
---
### Author:  [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)
#### Post date: [October 14, 2014, 12:24pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/16 "2014-10-14T12:24:27Z")
> [@Shakes](#):
>
> I heard that the Big Bang was able to expand faster than the speed of light because the things that make light travel at the speed it does didn’t exist yet.
>
> It kind of makes me wonder if you could go to the very edge of the universe, would the laws start to fall apart?
Um, no. C limits how quickly things can travel in space, it is not a limit on the expansion of space itself.
---
### Author:  [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)
#### Post date: [October 14, 2014, 12:59pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/17 "2014-10-14T12:59:50Z")
Robert163, does what we’re saying make any sense at all to you? I’m afraid that this thread is going to turn into another one where we get into endless details that are incomprehensible to the person who asked the question. Let’s get back to finding out if what we’re saying here makes sense to you.
---
### Author:  [@Grrr](https://boards.straightdope.com/u/Grrr)
#### Post date: [October 14, 2014, 1:40pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/18 "2014-10-14T13:40:40Z")
> [@naita](#):
>
> That’s false. The expansion of space isn’t limited by c at all, even now.
So when the BB happened, were the four basic forces immediate? Or did they first exist as one “super force” and then break down into the four basic forces?
---
### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [October 14, 2014, 2:38pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/19 "2014-10-14T14:38:07Z")
> [@Shakes](#):
>
> So when the BB happened, were the four basic forces immediate? Or did they first exist as one “super force” and then break down into the four basic forces?
How is that relevant to the OP or what you posted earlier?
---
### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [October 14, 2014, 2:40pm UTC](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230/20 "2014-10-14T14:40:17Z")
The expansion of the Universe is neither faster than nor slower than c. It cannot be compared to c, because the units are different. The units for the expansion rate of the Universe are frequency units, not speed units.
[Next page](https://boards.straightdope.com/t/100-certain-physical-laws-are-same-in-other-galaxies/701230.md?page=2)