expanding universe

del88

Why is the expanding universe considered so unusual....when a bullet is fired from a gun it accelerates for the first few seconds before it reaches it's maximum velocity and then begins to slow due to air resistance...so why can't the universe still be expanding/accelerating due to the the energy from the big bang just as the bullet accelerates due to the energy released when the gun is fired????
Am i missing something here?

Sykk

del88 wrote: »

Why is the expanding universe considered so unusual....when a bullet is fired from a gun it accelerates for the first few seconds before it reaches it's maximum velocity and then begins to slow due to air resistance...so why can't the universe still be expanding/accelerating due to the the energy from the big bang just as the bullet accelerates due to the energy released when the gun is fired????
Am i missing something here?

I think the "gun" explaination is slightly different than the universe expanding. As the theory of universal expansion supports the idea that dark matter is expanding at a more rapid rate as time goes on.

Also - Where did you see it's considered unusual? I'm led to believe it's the belief of most scientists.

del88

Sykk wrote: »

I think the "gun" explaination is slightly different than the universe expanding. As the theory of universal expansion supports the idea that dark matter is expanding at a more rapid rate as time goes on.

Also - Where did you see it's considered unusual? I'm led to believe it's the belief of most scientists.

Why does it need the presents of dark matter to explain the acceleration of the expansion??

r3nu4l

I don't know the answer but maybe gravitational forces within the early universe should have slowed the acceleration but when it was observed to be accelerating then perhaps 'dark' matter was the answer that explained it?

I really don't know

WalterMitty

del88 wrote: »

Why does it need the presents of dark matter to explain the acceleration of the expansion??

Observations indicate that the expansion couldnt have been constant since the big bang. Its dark energy not matter that is beleived to fuel the increasingly fast expansion. There was a rapid growth inintially after big bang but an even bigger one further on . Wat5ch bbc's recent horizon on big bang/inflation/dark energy.

WalterMitty

Dark energy was just proposed to explain the observation that the expansion now is speeding up but this rate of change has not been constant since the big bang. Somthing changed a few hundred thousand years after big bang , mayeb the force known as "dark energy" was able to overpower the gravitaional forces of dark and normal matter.

calabi yau

Is it true that scientists believe that with the universe expanding at ever increasing rates that the cosmos would be pulled apart to the point that planets will be pulled out of their gravitational orbits and we would be left with vast expanses of space with no planetary systems, were it not for the presence of unseen gravitational forces, I.e. Dark Matter

djhaxman

calabi yau wrote: »

Is it true that scientists believe that with the universe expanding at ever increasing rates that the cosmos would be pulled apart to the point that planets will be pulled out of their gravitational orbits and we would be left with vast expanses of space with no planetary systems, were it not for the presence of unseen gravitational forces, I.e. Dark Matter

The "big rip" they call it. It hasn't been proved that it will happen; scientists speculate that it might.

https://www.youtube.com/watch?v=JaImVFRpOR8

Podge_irl

del88 wrote: »

Why is the expanding universe considered so unusual....when a bullet is fired from a gun it accelerates for the first few seconds before it reaches it's maximum velocity and then begins to slow due to air resistance...so why can't the universe still be expanding/accelerating due to the the energy from the big bang just as the bullet accelerates due to the energy released when the gun is fired????
Am i missing something here?

The bullet only continues to accelerate when it has a force acting on it (namely the expansion of gases that arise from the cordite explosion in the barrel). Considering the expansion of the universe is still accelerating there must be something causing it, and this is where dark energy comes in. Dark matter is a different thing again which is needed to explain some gravitational effects.