Two Final Ideas: Relativity and Causality
Einstein Rescues Us:
- Sets the speed of light to be independent of the motion of
the source
provides absolute frame and finite communication
time.
- Thus, Einstein gives us causality - a very important thing
- Suggests that mass causes curvature of space and which is what
we call gravity. This means that time can act strangely in a strong
gravitational field:
An Orbit in Curved Space
This is a prediction made by General Relativity and confirmed
by direct observation of Mercury. This observation showed that Newtonian
Mechanics was an imcomplete description of nature
Its a great manifestation of Newton's 4th dictum.
- Gravity: Curvature of SpaceTime: Mass causes this curvature;
space is deformed around this mass; this deformation is gravity.
The more mass there is, the more deformation (curvature) there is
and gravitational field becomes stronger
- Since the universe is a SURFACE (in spacetime) then it has no
CENTER! (Cusa was correct).
-
and you:
Photons have an energy related mass. Photons are therefore effected
by gravity. Light is bent in a strong gravitational field as the
surface of the universe goes from being flat (light travels in
a straight line) to curved (light follow the curved trajectory).
This principle is shown in this
animation .
The distribution of mass on in the universe determines the detailed
shape of the surface light is constrained to follow this surface
and this allows the universe to be observed!
Ants with Flashlights in curved space time
- The ants can only communicate by flashlight
the photons in the flashlight must follow the curvature of the
universe because of the rule and so the
photons must follow the blue trajectory and not the red one
And now we are here:
