# What would the universe be like with less mass and energy?

• B
• Ethan Deibert
In summary, the conversation revolves around a hypothetical universe with the same laws of physics as ours but with a significantly smaller amount of energy-mass. The question is raised about what it would be like to live in this universe and if known laws of physics can provide answers. The conversation ends with the acknowledgement that the conversation cannot continue within forum rules due to the hypothetical nature of the discussion.
Ethan Deibert
So I have sort of a conceptual question about the big bang and gravity.

Imagine yourself in a universe, in which existed about the number of particles/energy in a 3X3 metre room at any given moment. This universe has the same laws of physics, constants and is identical in every way to our universe except that the amount of energy-mass is astronomically smaller.
Also in this imagined universe, the current time is a tiny fraction of seconds after the big bang, such that the universe has expanded to have the same pressure and mass -and by extension, volume- as that 3X3 metre room.
Now imagine that I suddenly appeared with a spacesuit on in that universe.
I've heard before that the universe is curved in some way. I'm not sure if it's 4-dimensionally curved and I'm not sure how it works, but the analogy of the universe as an expanding bubble is what I'm picturing here.
What would it feel and look like to live in that universe, would we be able to survive in it or would we be crushed/warped by the spherical shape of space or even ripped apart by the expansion of the mini-universe and are these questions that can't be answered using known laws of physics or do we not know enough about what's past the observable universe to say?

I've studied up to first year undergraduate physics but I do know a little bit about gravity and relativity however I'm not that great at math. If anyone could help me get a better grasp of the ideas needed to visualize this problem in their answer that would be great! I'm really just curious and want to try to understand how the universe works.

I appreciate any insight you can give!
Thanks.

Ethan Deibert said:
... the analogy of the universe as an expanding bubble is what I'm picturing here.
then you are not imagining anything that resembles the universe we live in.

I'm really just curious and want to try to understand how the universe works.
I assume you believe that when you say it, but it doesn't really sound like it. You are asking about a universe that is nothing like ours so how does that help you understand the universe we live in?

Ethan Deibert said:
are these questions that can't be answered using known laws of physics or do we not know enough about what's past the observable universe to say?
These questions cannot be answered using the known laws of physics because those laws apply to the universe we live in, and you're talking about a completely different universe.

This thread is closed because there's no way of continuing the discussion within the Physics Forums rules.

## What would the universe be like with less mass and energy?

There are several questions that come to mind when considering the possibility of a universe with less mass and energy. Here are five of the most frequently asked questions and their answers:

## 1. Would the universe still exist with less mass and energy?

It is possible that the universe could still exist with less mass and energy, but it would likely look very different than it does now. With less mass and energy, there would be fewer stars and galaxies, and the universe would likely be much colder and darker.

## 2. How would the laws of physics be affected?

The laws of physics are based on the fundamental properties of mass and energy, so if there were less of both, the laws of physics would likely be different as well. This could have a significant impact on how the universe functions and evolves.

## 3. Would life still be possible?

It is difficult to say for certain, but with less mass and energy, the conditions necessary for life as we know it may not exist. The universe would likely be less hospitable to complex life forms, if they were able to exist at all.

## 4. How would the expansion of the universe be affected?

The expansion of the universe is driven by dark energy, which is a form of energy that is thought to make up about 70% of the universe. With less energy, the expansion of the universe could potentially slow down or even stop entirely.

## 5. Would the universe eventually collapse?

It is possible that with less mass and energy, the gravitational forces in the universe would not be strong enough to overcome the expansion and hold everything together. This could lead to a potential collapse of the universe, but it is difficult to predict without more information about the specific conditions.

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