Background

Parallel universes where the cosmological constants are different to ours have been hypothesised. Most of these would presumably lead to a chaotic mess.

The observed values of the dimensionless parameters (such as the fine-structure constant) that govern the four forces of nature are finely balanced. A slight increase in the strong nuclear force would bind the dineutron and the diproton and all the Hydrogen in the early universe would have been converted to helium. There would be no water or the long-lived stable stars that are essential for the development of life. Similar relationships are evident in each of the four force strengths. If they are modified sufficiently the universe's structure and capacity for life is greatly affected.

http://www.universe-galaxies-stars.com/Anthropic_principle_print.html

Our universe seems to be an arbitrary balance between constants that happen to "work".

It Takes 26 Fundamental Constants To Give Us Our Universe, But They Still Don't Give Everything

https://www.forbes.com/sites/ethansiegel/2015/08/22/it-takes-26-fundamental-constants-to-give-us-our-universe-but-they-still-dont-give-everything/#32b8b7794b86

Worldbuilding

A number of explorers have developed a way of jumping between such universes. I'm interested in their exploits under the various conditions, however, starting at zero ...

Question

What would it be like if our explorers landed in an alternative universe containing absolutely nothing?

This universe has nothing in it except an infinite amount of empty space.

Would the explorers impose their own constants (such as gravitation)? Or would they explode or turn to nothing? Must we assume that there is any kind of energy in the space or could it be literally empty of all matter and energy?

• "Heat death" assumes that cosmological constants remain the same. – Alexander Aug 7 '20 at 17:08
• I do not see anyway to answer this if you require hard-science. We barely understand this universe let alone "other" universes (if they even exist). – StephenG Aug 7 '20 at 17:31
• It’s not clear that space can even exist in the absence of matter — it may simply be defined by matter’s interactions with itself rather than having any independent existence. – Mike Scott Aug 7 '20 at 17:34
• You do understand that own universe is a very very good approximation of an universe containing absolutely nothing? Places where our universe contains something instead of nothing are few and very far between. – AlexP Aug 7 '20 at 18:10
• If you put your matter into a new universe it would have to conform to the new constants unless you could protect yourself somehow from the very nature of the universe. If you could hop over to a new universe though, maybe you've already figured that out. Some kind of energy shield that prevents interaction between...anything. imagine trying to dodge gravity or being invisible to the full electromagnetic spectrum or just being chemically nonreactive. You have to keep the new universe off of you. – Leviathann Aug 7 '20 at 18:12

They turn to nothing.

If you travel to another universe, we must assume that all that you are will have to obey the new laws of that universe. So if gravity is a bit higher for a similar mass planet, they will experience a bit higher gravity. If the weak nuclear force is a bit stronger, then the travelers will have all their internal water converted to helium and die. If you travel to a universe where the laws allow nothing, then your very existance would turn into nothing upon arrival.

There are only two other options:

1: everything you bring into another universe will keep acting according to its own universe's laws, which would make no sense.

2: everything you bring into that other universe rewrites all the laws of that universe to coincide with the universe it came from.

Both of these options make no sense at all. Mind you the laws of physics as far as we have them are paradoxes by nature (heh), such as light traveling the same speed for everything yet for some reason other paradoxes aren't supposed to be able to exist for... reasons...?

I know you've put in hard-science tags but that really doesnt make a lot of sense considering the question you seem to be asking. We can create hypotheticals using our knowledge of "basic" forces to determine how our universe could have looked like, but to say how a particle from a universe with constant physics/force A would react if it was brought in universe with constant physics/force B?

• The OP hasn't mandated any differences in the physical laws of his empty universe he only states that there is nothing in it, no mass & no energy, the ultimate vacuum, unless he states otherwise the rest of his blurb about different forces would appear to be entirely irrelevant fluff, so, in such a situation they'd simply appear in their spaceship, for practical purposes it would be nothing different to being teleported into deep space. – Pelinore Aug 7 '20 at 19:07
• There's a third option (as posited by Isaac Asimov in The Gods Themselves): objects brought into another universe initially retain the laws of their home universe, but gradually take on the laws of the new universe over time. – The Daleks Aug 7 '20 at 20:15
• @Pelinore as far as I'm aware that "blurb" was to illustrate his starting position: a universe empty of all laws. Things like the weak nuclear force would either be zero or non-existant. What would be the point otherwise? "Lets go to a universe the exact same as ours but nothing in it, ignore the universal constants we just talked about". – Demigan Aug 7 '20 at 23:53
• "a universe empty of all laws" not what he said & doesn't make sense if that's what he meant, changing the parameters of a universal constant doesn't mean it doesn't exist, even changing your example one as suggested by you, as for the point, as the question has been written there wouldn't be any point & that's part of what's wrong with his question. – Pelinore Aug 8 '20 at 0:17
• @Pelinore what do you think these words in his question mean: "starting at zero". "A universe with absolutely nothing in it except an infinite amount of empty space" and "would the explorers impose their own constants"? – Demigan Aug 8 '20 at 7:26

Is it truly empty space?

Without a Higgs field and it's non zero vacuum potential, your particles would lose their mass. Gravity would cease to exist.

Without mass, balance of attractive forces, repulsive forces, and mass would all change. Without mass to anchor heavy atomic nuclei for electrons to orbit around, a massless atomic core would be able to move too fast for electrons to catch up (much like conditions in the early universe when atomic nuclei were too fast due to heat energy).

The result would be that everything would begin to vaporize without heating, much like water boils without heating in a vacuum. The "boiled" material is charged plasma.

Did you bring some of your Higgs field with you? How long would it take to dissipate: I don't think we know enough to even guess.

We don't know what gives our constants their values. Some theories are that this is energy trapped during the cooling of our universe, as the fundamental forces began to differentiate. Assuming that's true and you bring some of your compactified space with you, let's see what might happen:

Inflation happened for a stupendously short amount of time between $$10^{-35}$$ to $$10^{-33}$$ seconds. During that moment space seemed to grow at a rate of the speed of light, raised to the 7th power ($$c^7$$). Inside that expanding sphere, and after, the speed of light seemed to govern everything else. But why inflation happened, and why it happened so fast, is unknown. The rate entering an empty universe may be variable. It might even compress on you.

So let's say some initial amount of your universe flash expands, much like drops of water on a super hot skillet. Inside, you might be safe temporarily. At some rate your universe is either expanding into the new one, or the new universe is pressing in on what you brought with you. It may be different every time you do that.

This is completely a guess, but I'd think that like a comet facing hard vacuum or the water on skillet, a sacrificial outer layer of stuff exposed to the foreign universe will begin to boil away at some rate, temporarily protecting what's inside.

• Nope! Gravity exists without the Higgs Field. Higgs gives leptons and quarks more mass then they should have. But most of the mass of an atom comes from it's binding energy and not the Higgs field. – Daron Aug 8 '20 at 22:47

THERE ARE (at least) TWO CASES. SEE!

Case 1: The universe has the same universal constants et cetera as ours. It just happens to have no matter in it. In this case jumping into the new universe would be similar to jumping into outer space. Darker sure. But with no additional hazards or risks of sudden existence failure.

Case 2: The universe has a different arrangement of constants than ours, and this is what prevented matter forming. But the universe has the same number of quantum fields so has the potential to support the same set of particles. In this case for example protons that move into the new universe change their behaviour to become heavier/lighter/more charged depending on the constants.

After all a proton is just an excitation in the proton field. Think of it like a wave in the ocean. Passing from one universe to the other is like passing into an area of shallower water for example. The wave continues to exist, but it might become more jagged or start to crash.

Probably all complicated structures (for example atoms and people) will fall apart entirely when they jump into the new universe, because of the fine balancing you mentioned.

Case 3: The universe has some of the fields missing. There is no medium to support protons for example. I guess that means protons just bounce off the universe, like how a water wave splashes off the pier, rather than somehow traveling through it.

Case 4: The new universe has no fields at all. Hence it is not capable of supporting matter in any form. The physical meaning of this is unclear. Perhaps this forbids the universe from taking up any space at all.

It depends on your definition of empty space

A couple answers touch on this pretty well but I think they don't exactly answer what happenes.

1. The universe is Empty Space - in this case, space is not really empty. The Higgs field exerts an energy in every region of space, even if there is no matter, photons, neutrinos, or anything at all. If it is empty space, you would simply arrive and see nothing but yourselves (with whatever light source you brought). Your body mass, every particle in you, is an excitation of the Higgs field. Nothing would be different about you.

2. The space in the universe has nothing - in this case, if there are no fields, not even a Higgs field, you won't arrive in that universe. You will simply not exist after you leave the current one. Your form cannot be contained in a place which can't even manifest the particles of your body.

If such a universe existed and you travelled to it, you would quickly die.

1. In such a universe there would be no heat sources and the equilibrium of your heat vs. your surroundings would quickly try and bring your body temp from 98F to absolute zero (technically whatever the median heat is) assuming you could radiate leading us to

2. You would be the only heat source and have no way to radiate it out to the surrounding air so you would eventually overheat and die.

3. you are wrong and it isn't empty, its anti-matter in which case you do blow up.

4. this question is too broad if you try to impose physics outside of our universal equivalent.

Most scenarios of an "empty" universe have extremely abundant ways to passively die. presumably, because a dead universe really tries to stay dead.

EDIT:

Our current spacecraft relies on solar radiation as part of its heating cycle such as 275 F on the solar side and -275 F on the dark side of the spacecraft. Intense insulation and redistribution of heat keeps the craft from essentially boiling on one side.

"Without thermal controls, the temperature of the orbiting Space Station's Sun-facing side would soar to 250 degrees F (121 C), while thermometers on the dark side would plunge to minus 250 degrees F (-157 C). There might be a comfortable spot somewhere in the middle of the Station, but searching for it wouldn't be much fun!" -https://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1

This is mitigated by redistributing the heat. now imagine both sides being 0K with how compact and lightweight our spacecraft have to be, Internal heating won't last long and would be working overtime.

• (1) "There would be no heat sources and the equilibrium of your heat vs. your surroundings would quickly try and bring your body temp from 98F to absolute zero": unless of course you bring some heat source with you. Many of our spacecraft did. (2) "You would be the only heat source and have no way to radiate it out to the surrounding air so you would eventually overheat and die": unless, of course, you have a way of radiating it. All our spacecraft have such a way. – AlexP Aug 7 '20 at 18:13
• @AlexP while everything you said is true, that is only if you consider it ahead of time. If you didn't engineer for 0k heat death universe it is incredibly likely your systems will not keep up with excessive differences in heat. – IT Alex Aug 8 '20 at 23:37
• @IT Alex to a spacecraft warm enough to support humans, 0K isn't noticeably different to the 3K of our universe's vacuum. – Starsong67 Aug 9 '20 at 16:13
• @Starsong67 sure but our universe still has a sun providing radiation warming to half of the craft. – IT Alex Aug 10 '20 at 12:32