What is the Universe expanding into..

Do you think there was anything before the big bang?

  • I don't think there was anything before the Big Bang

    Votes: 56 12.5%
  • I think something existed before the Big Bang

    Votes: 200 44.7%
  • I don't think the big bang happened

    Votes: 54 12.1%
  • I think the universe is part of a mutiverse

    Votes: 201 45.0%

  • Total voters
    447
Status
Not open for further replies.
From Astronomy to Architecture!
 

Attachments

  • Federation Square Melbourne Architecture.jpg
    Federation Square Melbourne Architecture.jpg
    296.7 KB · Views: 107
I am reminded of something Dave Kimber (RIP) said on this site a few years ago. He pointed out that on more than one occasion physicists had been proven right about how things worked in reality and mathematicians wrong.

Einstein, and before him Newton, but really a host of famous people started out thinking about a problem, went through thought experiments, and then turned to math in order to encode their ideas in a form that could be tested through the power of prediction as for example in The case of light bending around a massive body like the sun for example.

Currently, the physics world is battling to unite QM and Relativity and it’s not going well. String Theory seems to offer a solution, however it’s not testable in anyway - it remains pure mathematical conjecture despite the best efforts of theorists like Ed Witten and Juan Maldacena.

See Sabina Hossenfelder’s blog for a discussion and why physics is in crises Sabine Hossenfelder: Backreaction

Note this only applies to unification theory - there is good research with predictable, practical, measurable outcomes in most other ranches of physics- one of the areas closer to home of course being solid state physics.

One last thought on this stuff. We have a reasonably good theory for the very big, the very small and EMR. It works otherwise we’d not be having this discussion right now via our devices. We do not have a cure for cancer, Alzheimer’s, Parkinson’s, HIV and a host of other ailments and the people working in these fields are no less smart than the string theorists.
 
Last edited:
perhaps the speed of light is lowing down so all observable length scales are shrinking because we perceive the speed as constant and hence, the universe is not expanding and the dark stuff is what causes c to decrease
Light does slow down when it enters water or other transparent material. In a vacuum it doesn't slow down, color shifts towards the red side of the spectrum.
 
What logic can cope with the beauty of 24-dimensional space? Linearity is a one dimensional relationship. Algebra cannot even handle dimensionless quantities.

benb,
"theorem" still denotes a proven logical relation, the unpleasant discoveries made in the twentieth century have not changed anything. Life goes on in the mathematical fictional fantasy world as if nothing ever happened.
 
I'm not quite sure what you are asking, TNT.

There are three causes of redshift. The movement of a galaxies relative to each other, the universe's expansion and gravitational redshift.

If we are considering the former, the redshift is not a 'problem' of the observer or of the light, but is a consequence of their relative motion.
 
Derivation of the Mass-Energy Equivalence:

Momentum = mv .... (where m: mass, v: velocity)
We will consider both v and m as functions as both of them can change with time.
d[mv]/dt = m.dv/dt + v.dm/dt ..... (i) (where t: time, dt: an infinitesimal increase in time)

Relativistic Mass:
m = M/sqrt[1 - (v/c)^2] ..... (ii) (where M: stable mass, sqrt: square root function)

Squaring and rearranging:
m.sqrt[1 - (v/c)^2] = M
m^2.[1 - (v/c)^2] = M^2

Removing c^2 from the denominator:
c^2.m^2 - m^2.v^2 = c^2.M^2

Differentiating with respect to time:
c^2.2m.dm/dt - (m^2.2v.dv/dt + v^2.2m.dm/dt) = 0

Removing redundant terms:
c^2.dm/dt - (mv.dv/dt + v^2.dm/dt) = 0 .... (iii)

Rewriting and inspecting (i):
d[mv]/dt = m.dv/dt + v.dm/dt

The rate of change of momentum is equal to the force producing such a rate of change. The increment of energy is: F.dr, where F is the acting force and dr an increment in displacement.

Therefore:
dE = F.dr

Substituting (i) in the above:
dE = m.(dv/dt).dr + v.(dm/dt).dr

But, dr/dt = v, by definition of velocity:
dE = mv.dv + v^2.dm ..... (iv)

Comparing (iv) with (iii):
dE = c^2.dm

The above, mathematically states, the increment in energy is equal to the square of the velocity of light, multiplied by the increment in mass. In other words, it is telling us, mass and energy are equivalent.
 
Light does slow down when it enters water or other transparent material. In a vacuum it doesn't slow down, color shifts towards the red side of the spectrum.
Perhaps it is the conflation of refraction (in the first sentence) with redshift (in the second sentence) which is problematical.

When a ray of monochromatic light slows down on entering an optically denser medium it's wavelength decreases, but its frequency does not change.

Since colour is determined by frequency, the colour of the light does not change on slowing down.

This is refraction and is not comparable with redshift.
 
Status
Not open for further replies.