# What would happen if the speed of light was fundamentally faster?

Now maybe this belongs in physics, but I want it here because I'm interested in the impacts on our society if the speed of light (c) were to be 2x faster since the big bang.

My first thoughts were about how this would impact our energy and e=mc^2, which would mean the entire universe would be in a higher state of energy, but what would this actually mean for us in terms of consequences?

# TO CLARIFY:

In this new universe: c is twice as big as c in our universe. Other than that, everything stays the same, in terms of universal constants. I don't want a response as to why this would not work or why I have got some semantics wrong, this is a "what if" style question, I want crazy and wonderful answers!

• You should clarify wether the universe was "born" this way or if it suddenly doubled (or if it gradually increased over the course of a day/year/millennium/...). Also, to avoid misunderstandings it's best to refer to the speed of light as c. Jul 15, 2016 at 14:48
• @Cursed1701 I believe there is a scientific theory that talks about the speed of light being much faster at the beginning of the Jul 15, 2016 at 14:57
• @BryanMcClure so, you're saying there is a theory that at the big bang, the speed of light was faster.. but slowed down? Jul 15, 2016 at 15:05
• @Cursed1701 yes slowed down over time and is continuing to do so look up "is the speed of light slowing down?" and you will get the theory. Jul 15, 2016 at 15:13
• Jul 16, 2016 at 5:18

Nuclear reactions would be much more energetic. Top of mind I can think of nukes delivering many more megatons for the same payload.

But what really boggles my mind is the nuclear fusion in the core of stars. Stars would output much more energy in that universe than in our own. This would change interstellar dynamics. Supernovas would be much more dramatic events. I don't have the math in me to calculate how bad that would be for life but I think this would prevent life from ever forming as we know it, since the killing range of novas would go up by orders of magnitude. For any star you may think of, the goldilocks zones around them would be way farther from them than they would be in our world.

The mass threshold that determines whether a supernova will leave behind a neutron star or a black hole would also change. It would take much more mass to form a black hole. The universe might evolve in a much different way due to that.

Also the observable universe would be much bigger for the same perceived amount of time since the Big Bang. That might be interesting.

• thank you! for being someone who is not arguing with the question, and also for some awesome side effects!! Jul 15, 2016 at 14:58
• I'm not sure that stable stars are possible under these conditions. As a star forms, it won't ignite until it has built up the same internal pressure and temperature as would be required in our universe. But four times as much heat is generated. The star may not hold together under the increased pressure from heat and radiation. Jul 15, 2016 at 19:33
• Hold on, why would stars have more energy? Or any lightspeed particle for that matter? The math concerning lightspeed would have moved its endspeed but otherwise it wouldnt change. Going 150.000.000m/s in our universe would equate to (close to) 300.000.000m/s in the new universe as time dilation and relativistic mass sets in later. Apr 8, 2019 at 11:09
• @Demigan E=MC^2. Doubling the speed of light means nuclear fusion releases 4 times as much energy. Apr 8, 2019 at 14:46

As a physicist with no rep on this site, I have been lured over by this interesting question.

I think the real answer is that the physical consequences of doubling the speed of light would be so far reaching it would be very difficult to accurately describe such a universe without making huge errors and introducing ridiculous inconsistencies. It's not as simple as your GPS being twice as fast, or nukes being twice as powerful. The entire universe would be radically different; one should really be questioning whether human life or life at all would even be possible.

You might want to read about the fine-tuned universe theory over on Wikipedia. Because even a minute change in the value of physical constants (such as c) would eliminate the possibility of life as we know it, some physicists reckon that physical constants are somehow 'fine-tuned' for life.

Just an extract:

If, for example, the strong nuclear force were 2% stronger than it is... diprotons would be stable... hydrogen would fuse into them instead of deuterium and helium. This would drastically alter the physics of stars, and presumably preclude the existence of life similar to what we observe on Earth.

There are criticisms of this theory, particularly that it is 'anthropocentric'. My personal view is that life is so ridiculously improbable anyway that we could never predict what other kinds of life might exist or could exist in alternate universes, such as the one you are proposing. After all, the laws of physics don't predict the existence of humanity in our universe.

I would just think of a doubled speed of light as basically a get-out-of-jail card to come up with whatever universe you like, rather than thinking how it might alter this one. Alternatively, just hope that no chemist, physicist, or mathematician ever comes across your universe!

Oh and... my 1 rep means I can't leave comments or downvotes. I don't mean to offend but the answer by @EveryBitHelps is absolute codswallop.

• Welcome to the site Owen, I heartilly agree, nice first post. (From review) Jun 27, 2020 at 20:39

The fine structure constant becomes twice as small as we know it, resulting in twice as large periodic table. I can't do the math, but the gut feeling is that unstable elements in such a universe would be a rarity (at the non-relativistic limit $c \rightarrow \infty$ there are no unstable elements whatsoever), so no A-bomb, good. On the other hand, fusion is still there, and ignites at lower energies, so the whole stellar dynamics becomes quite different. Again, I don't have any math to support the claim.

• You need to differentiate between the different coupling constants to make this argument. The EM fine structure constant isn't going to be affecting the stability of atomic nuclei all by itself; you have to show whether the changed strong and weak constants reinforce stability or counteract it. Apr 8, 2019 at 12:39

Well, OR you could have the same amount of energy but AU-Einstein discovered the formula e=m*(c/2)^2... ;)

"c" isn't defined by the speed of light, it just so happens that since c is the highest speed possible and light has no mass (and thus can achieve the highest speed possible) the two are equal. C is the speed of causality - no consequences of any event can propagate faster than c. This means that information cannot be transmmitted faster than that either - I don't think it would actually change a lot in a practical sense though, unless you include additional requirements like "AND e=mc^2 is still the same" ;)

• Speed of causality! Causality is an abstract notion. The idea that an abstract notion move is incredible. Relativity assumes c is invariant. As a consequence of lightspeed invariance information and mass cannot attain FTL velocities. Pure & simple special relativity. Jul 16, 2016 at 11:47
• Congratulations. Your mass-energy was correct for the OP's AU, while I managed to go quite wrong. My sluggish brain cells need a good overhaul. Jul 16, 2016 at 11:49

One problem about your concept is that the lightspeed appears in some other physical laws that they would all have to be rejigged to remain constant. So we assume that is so, then that means everything else in the universe is the same as in our universe. That means no increased energy outcome from nuclear reactions because E = m(c/2)^2.

Of course, if you left all the other physical constants at the same values as in our universe things start becoming funny fast. (No pun intended.) Electromagnetism would be rewritten because its equations define lightspeed. Every equation with a value for lightspeed will be changed and its consequences thought through. For example, electric and magnetic fields will be stronger. Cosmic rays will be faster, roughly twice as fast.

What about fast interstellar travel? Not really. The energetics of propelling a spacecraft to close to the new lightspeed are, at least, just as formidable as for our value of c.

On a planetary scale. Just spitballing, no maths. (assuming some sort of life as we know it could exist)

The difference in the speed of light and sound would increase. So Eg you would see the lightning alot earlier than hear the thunder. That lightning would also be brighter and possibly longer lasting...so no watching lightning storms without protective eyewear!

Also, in talking. The person you listening too, would appear to finish talking before you heard what they said. It would be like watching a badly dubbed Chinese movie!!! Or like talking on a bad international phone call.

You won't be able to see further, as the curvature of the planet would remain the same but you would be able to see clearer for the same distance. So no hiding in the distance hoping no-one sees you on the battlefields. Think elf-like vision.

The sound barrier was broken and now we can travel at mach speeds. If you double the speed of light, you have just increased the chances of NEVER creating faster than light travel. There goes FTL, and galactic and intergalactic space travel... and time travel for the time being.

No visitation by alien's, unless they are on multi-generational sublight ships. Which makes friendly encounters less likely as they will be desperate for refueling/restocking. So yeah, think Independence Day/Battle Los Angeles rather than E.T.

Although you would be able to see them coming a lot sooner so you would have time to prepare and grab your towel! It would be possible that you could set up a communication network with other planets. You would never meet them, but you could chat and share ideas via a light beam (as long as you take care not to burn out the receivers with too focused a beam. Whoops! There goes your friendy communication attempt and now they are coming to get you).

Light could possibly travel further into the oceans (assuming the light didn't just burn off all the water) this would increase the 100-200 meter zone where most (not all) life exists in the sea. If the light is too harsh on land, it could result in those fishy ancestors of ours never having left the ocean and an underwater civilisation may have evolved instead.

• "The difference in the speed of light and sound would increase. So Eg you would see the lightning alot earlier than hear the thunder." You might want to check your math. Currently, if lightning strikes 3km away, you will see it after 0.00001 seconds and hear it after 8.81600987 seconds. If you double speed of light, you will see it after 0.000005 seconds. This means that delay increases from 8.81599987 to 8.81600487. I would hardly call it 'a lot earlier' compared to current situation... Jul 18, 2016 at 9:40
• You are correct. The times are minuscule and WE would hardly notice something like that. But in a universe like that, maybe the lifeform that evolves is sensitive to this increased speed of light. Maybe they could see the difference. Like I said, no maths, just spitballing :) all of these differences could be quite slight but they would be there :) Jul 18, 2016 at 11:08
• @EveryBitHelps , I was searching for this question, could you or anyone explain if plants would grow faster? There some evidence that light has slowed down on a curve. Looking at it from a Biblical view, would trees and plants and such have grown faster, more instantly? Apr 8, 2021 at 1:35

No impact.

Speed of light is a dimensioned physical constant. Speed of light is 2x faster, only means that the definition of metre in your world is 0.5x shorter (0.5m in the real world is 1m in your world), or the definition of second is 2x longer time interval (1s in the real world is 0.5s in your world).

You need to change some Dimensionless physical constant.

• to clarify: in this new universe where c is 2x bigger, I meant that you would effectively carry over the metre(which would stay the same) but instead of being about 300million m/s, c would be 600 million m/s Jul 15, 2016 at 14:50
• @Cursed1701 that is a contradiction. A meter is the distance that light travels in (299 792 458)^(-1) seconds. If the speed of light changes the meter must change as well Jul 15, 2016 at 14:56
• @Annonymus this is MY fictional universe, and in MY fictional universe I have my own rules, and I define C to be twice as big in MY universe as opposed to this universe, stop arguing with the question Jul 15, 2016 at 14:57
• @a4android yes, if any eventual humans (or similar) in this alternate universe were allowed to make their own meter, that would be true, but the OP explicitly stated they wanted the same meter, which is not a statement that makes sense, the OP either has to use our universe's definition of meter, which means the meter will change, or supply an alternative one, in which case they may give any definition they want that may or may not have the length of a meter in our universe be equal to that of a meter in their universe. Jul 16, 2016 at 5:58
• "that is a contradiction. A meter is the distance that light travels in (299 792 458)^(-1) seconds." That's a quite modern definition of metre. The original definition, in place when the metric system was created, was "one ten-millionth of the distance from Equator to North Pole". Evidently, the question is about what would happen if light's speed was 60 times the distance between the Equator and the North Pole per second, instead of just 30 times. Jul 16, 2016 at 15:14