UNRESOLVED QUESTIONS IN COSMOLOGY these are all galaxies -->

What happened at the Big Bang?

It is clear (from telescope observations and relativity theory) that the Universe is expanding outwards. If you run it backwards in time everything comes together in a single point around 15 billion years ago.

The background heat from the bang is very uniform. This is evidence for “inflation”: in the first few moments the Universe expanded much faster than the speed of light! This means there’s more Universe out there that’s too far away to see.

Time and space themselves began then. There was no “before”. (I don't get it either, but the people who do agree on this point.)

Quantum Genesis means “nothing” blipped into “something” because of quantum mechanics. But if the creation of the Universe happened outside of time, then it must happen all the time. It means there’s LOTS of Big Bangs.

Quantum Mechanics means that:
o Everything is BOTH a particle and a wave
o Object’s energies can only have certain values.
o The Heisenberg Uncertainty Principle doesn’t allow a region of empty space to be completely empty. There’s a “zero point energy”: pairs of particles constantly appear out of nothing and then annihilate each other! It happens so quickly they’re mostly not detected.

Where is the Universe headed?

The expansion of the Universe is actually speeding up! Some “dark energy” is pushing galaxies apart faster and faster despite gravity. We observe this with telescopes. .

It appears that ordinary matter is only 5% of the mass of the Universe. Dark matter” makes up 25%. Some sort of small particles? Neutrinos? Dark energy” makes up 70%. You can’t see “dark matter” or “dark energy” but we know they’re there because of their gravitational effect on the galaxies & stars.

Black holes have quantum fluctuations right at the event horizon – pairs are formed – one particle goes into black hole, one goes out! So all black holes are slowly evaporating away.

“Dark Energy” is probably the repulsion caused by the zero point quantum mechanical energy in empty space.
However, when you try to calculate how much “dark energy” there is you get ten to the 60th power times more than we detect out there! A problem!

In any case, it appears that the Universe will continue to expand.

Why does our Universe exist at all?

The physical constants in the Universe like the charge on an electron, the strength of gravity, and the speed of light are finely tuned to allow atoms, molecules, planets and stars to exist. If the constants were even slightly different, we wouldn’t be here at all.

Maybe many Universes (with different constants) were made, but thinking beings can only exist in one like ours?
“Universe” then doesn’t mean “everything that is” but “everything that is for us”.

What is Gravity, really?

The total energy of Universe = zero because mass & motion is (+), gravity is (-). They balance each other.
There are four fundamental forces in nature: the strong nuclear force, the weak nuclear force, electromagnetism and gravity. These four become the same at 10 to the 27th power degrees because of quantum mechanical effects.

Einstein’s Relativity describes gravity as “bending” of space-time geometry by heavy objects. Gravity (as described by Einstein) is not compatible with quantum mechanics, which we know to be true for small things like electrons.

We need a theory of quantum gravity to describe the beginning of the big bang when the Universe was small.

The Earth is 4.5 billion years old. Earth had life on it by about 3.5 billion years ago. It’s obvious that today’s simplest life forms (based on DNA, RNA and proteins) are way too complex to be the first life forms.

In 1953 Stanley Miller made amino acids by electric discharge. But amino acids aren’t life.

Amino acids and adenine (a base in DNA) have been found in meteorites. But these simple molecules aren’t life.

It’s apparent that before DNA-based organisms there probably were RNA-based organisms. But RNA is way too complicated to make itself.

Perhaps the first life was chemical reactions on the surfaces of minerals (pyrite? Clay minerals?) But nobody has made this happen in the lab.

If we knew the answer, we would be able to re-create it in the lab in a few weeks!

Is there life elsewhere? Is there intelligent life elsewhere?

There are no signs of any life (not even fossil bacteria from Mars) yet in our own solar system. All other planets are too cold or too hot. Humans have the technology to visit/colonize Mars today. We just haven’t done it yet because it’s too expensive/complicated/risky.

Our galaxy (The Milky Way) has 200 billion stars. There are billions of other galaxies. Many nearby stars have planets around them – probably most stars do. We have listened for radio signals from distant stars & galaxies for decades, and have never detected one.

Maybe they’re so advanced we can’t recognize their signal.
Maybe they’re deliberately hiding their existence from us.
Maybe intelligent life is so rare and fleeting that the in the vastness of space & time we miss meeting each other.
Maybe we’re alone among all those stars.

 

The more the Universe seems comprehensible, the more it also seems pointless.
– Steven Weinberg, Theoretical Physicist and Nobel Prize winner

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