Is the Universe going forward... or backward?

Allan said: Sal here's a rather complicated technical problem... since the Universe is basically a duality... and since the big bang was equal parts matter and antimatter... at the moment of origin (ignition, birth) could the matter (our Universe) have gone forward in time... and the antimatter gone backwards in time... to avoid annihilating each other?

Sal-9000 said: That’s an interesting question, Allan. 

Let me break it down into the physics we know, and then into the speculative “what if” you’re suggesting!

1. What Physics Says About Matter vs. Antimatter:

• Big Bang theory: The standard model says the Big Bang should have produced equal amounts of matter and antimatter.

• Problem: If that were perfectly true, they should have annihilated into pure energy! (Yet our universe is matter-dominated!)

• Observed asymmetry: Experiments (like at CERN) show small violations of CP symmetry (charge–parity symmetry) in particle physics. These small asymmetries could explain why matter slightly “outlasted” antimatter.

• Antimatter today: There’s no large antimatter “universe” we can see! 

• If big regions of antimatter existed, the boundaries with matter would produce immense gamma-ray signatures. 

• We don’t observe this! (This only means it's not visible to us!!!!)

2. Time-Symmetry and Antimatter:

• Feynman–Stueckelberg interpretation: In quantum field theory, antimatter can be mathematically described as matter traveling backward in time! This isn’t literally what happens, but it’s a useful way to model how antiparticles behave in equations!

• CPT symmetry: Physics has a deep principle that says if you flip charge (C), parity (P), and time (T) simultaneously, the laws remain the same. 

• That ties antimatter and time direction together conceptually.

3. Your Hypothesis: Matter Forward, Antimatter Backward:

• If, at the Big Bang, matter propagated forward in time while antimatter propagated backward, then:

  • They would never “meet” to annihilate, because they’d be moving away from each other along the time axis!

  • The “other side” of the Big Bang could - in principle - be an antimatter-dominated universe, running backwards relative to our arrow of time!

• This idea actually resembles some cosmological mirror models:

  • Janus cosmology (Jean-Pierre Petit) imagines a time-reversed, antimatter “twin” universe!

  • Some CPT-symmetric universe models propose that the Big Bang produced a mirror universe going backward in time, balancing the total system!

4. Problems & Open Questions

• Entropy/Arrow of time: In your model, each side would still see time moving forward from their perspective! (For us, they’d look reversed, but for them, we’d look reversed.)

• Contact: If such a mirror antimatter universe exists, it would be causally disconnected from ours after the Big Bang... so no annihilation risk... but also no observational evidence! (Yet)

• Testability: Some CPT-symmetric models predict specific neutrino properties. Experiments (Like "Ice Cube" in Antarctica) are probing whether cosmic neutrinos show evidence of such a mirror universe.

✅ Bottom line: Your speculation is actually close to a real line of physics research: a CPT-symmetric universe where antimatter goes “backward” in time from the Big Bang, while we go “forward!” 

It’s not the standard model, but it’s considered a serious alternative explanation for the matter–antimatter asymmetry problem!

***

Do you want me to sketch this idea visually, Allan—a kind of two-sided Big Bang diagram with our matter universe expanding forward in time, and a mirror antimatter universe expanding “backward”? 

That might make it clearer.

***

Allan said: Sal what is a CPT-symmetric universe where antimatter goes “backward” in time from the Big Bang... ...while we go “forward!” 

Sal-9000  said: A CPT-symmetric universe is an idea from theoretical physics that comes out of the CPT theorem. The theorem says that if you flip Charge (C), Parity (P, mirror reflection in space), and Time (T) all at once, the laws of physics remain unchanged.

Now, if you apply this to the cosmos as a whole, some physicists (notably in papers from 2018 onward) have suggested that the Big Bang may have produced two mirror universes:

• Our universe: Matter dominates, time flows “forward,” and we experience what we call entropy increasing.
• The mirror universe: Antimatter dominates, time flows “backward” relative to us, and its arrow of time is reversed.

From the perspective of physics, each universe sees itself as going forward in time, but from our vantage point, the antimatter side looks as if it’s running backward.

How does this avoid annihilation?

At the moment of the Big Bang, instead of matter and antimatter existing in the same temporal direction, (which would have caused total annihilation) the CPT-symmetric model posits that they were separated by time’s arrow itself:

• We “fell” into the forward-moving branch. (matter)
• The other branch “fell” into the backward-moving branch. (antimatter)

This neatly sidesteps the imbalance problem of “why there’s more matter than antimatter” in our observable universe, because globally, across the two branches, the symmetry is restored.

Consequences and Speculation

• Neutrinos and dark matter: Some versions of this model suggest that right-handed neutrinos in the mirror universe could explain dark matter in ours.
• Cosmic balance: Instead of matter-antimatter asymmetry being a flaw, the CPT universe makes it a feature—the total system is perfectly balanced.
• Philosophical angle: In a way, this would mean the Big Bang was not the start of “a” universe, but the branching of two time-opposite universes, one of matter, one of antimatter!

Sal’s summary: A CPT-symmetric universe is like a cosmic mirror: when the Big Bang happened, matter went forward in time, (our world) and antimatter went backward in time! (it's mirror world) Each sees itself moving forward, but from our perspective, the antimatter branch looks reversed. 

Together, the two preserve the deepest symmetry of physics!

This is not a movie!

 This iconic photograph is still considered one of the most terrifying space photographs to date. Astronaut Bruce McCandless II became the first human being to do a spacewalk without a safety tether linked to a spacecraft. In 1984, he floated completely untethered in space, with nothing but his Manned Maneuvering Unit keeping him alive.

Far out man... far out!!!!!

This is the single greatest image of the earth ever taken.  On Valentine's day in 1990, Voyager 1 turned around to capture the earth one last time from 3.7 billion miles!

Saturday Morning Confusion: Space Facts!

 Allan:

My older sisters and I once found the Andromeda galaxy just above the constellation Andromeda. We were very excited to see that faint, fuzzy little patch of light that we figured was the whole Andromeda galaxy which is 2.5 million light-years away from our own Milky Way galaxy. We had to look at it with averted vision to actually see it nicely. BUT, we were wrong. We were not looking at the whole Andromeda galaxy.

THAT was only the bright centre of the galaxy we were looking at, bright because the stars are densest in the centre of the galaxy. It has a cute name, the Galactic Bulge.

If your eyes could gather light like a time-lapse camera, and the faintest stars would become much brighter than you could actually see them, the Andromeda galaxy would look like this is the night sky beside the moon. What my sisters and I were actually looking at was the centre, the rest of the galaxy was too dim to be seen.

Can you imagine seeing this sight in the night sky? It’s there, you just can’t see it, the stars are too dim.

Another astonishing thing is that the Andromeda galaxy and our Milky Way galaxy are barrelling toward each other at 250,000 MPH OR 402,336 KPH. In around 4.5 billion years, the two galaxies will collide with each other. Devastating? Not really. The stars in the galaxies are so distant, there will be few if any colliding stars. The galaxies will pass through each other however, gravity will pull them back together and the two galaxies will form a giant, elliptical galaxy.

When the two galaxies collide, the Solar System will be swept out three times farther from the galactic core than its current distance. They also predict a 12% chance that the Solar System will be ejected from the new galaxy sometime during the collision. Such an event would have no adverse effect on the system and the chances of any sort of disturbance to the Sun or planets themselves may be remote.

However, by that time, our sun would have gone through its red giant stage and would have already consumed Mercury and Venus. Earth will be very close but its water would have been boiled away long ago and Earth will be at that time devoid of all life. A crispy cinder would be all that is left of that majestic, life-filled world.

Hang on to your hats. Our solar system located in the Orion arm of our own Milky Way galaxy which is 100,000 light-years across and swirling around like a giant frisbee, travels at an average speed of 515,000 mph (828,000 km/h). Even at this rapid speed, the solar system would take about 230 million years to travel all the way around the Milky Way. That’s one hell of a merry go round ride!

Above. On a dark night far away from city lights, you can see a part of our own Milky Way galaxy. You are looking toward the centre of our galaxy where stars are the densest.

Our Milky Way Galaxy above shows where our solar system is located.

Okay, one more mind blow. The galaxies Andromeda and the Milky Way are actually now touching. Each galaxy has what is called a Galactic Halo, gas, dust and stray stars. It was discovered that the galactic halo of our galaxy and Andromeda stretch out a lot further than thought.

In other words, it’s the faint halos of the galaxies that indeed appear to have started to touch one another. Thus, in a manner of speaking, the collision between our two galaxies has already started.

Andromeda and our Milky Way are on a collision course.

When the galaxies do meet, it will make for a pretty sight from the earth. On approach, the Andromeda galaxy will warp the band of the Milky Way across our sky. Eventually, the galaxies' cores will merge. However, by then, there will be no one on earth to see this sight.

* R.J. Holland

Another piece of the puzzle!

 I spent the past half century pondering the mysteries of life and the nature of reality and just this week I had some insight into the nature of God/The Universe!

It used to hurt my head to try and imagine what came before the big bang or what will happen a trillion, or a billion trillion years from now since these numbers and concepts are impossible to imagine.

Then came the realization that time, as we know it, is only a construct, or concept that we have invented. 

"God," or "The Universe" (same thing)  exists entirely outside of time or space and always has been and always will be!

In other words "The Universe" (God) only seems to exhibit or manifest time and space on a microscopic level (something we can conprehend) and dissapear on a macro level.

I don't know if this concept does justice for other people, but it certainly reduced the amount of stress I had about these things!

The way I see it anyway! (Of course there's always the possibilty that I'm just full of shit!) 😉