3 ms·

Gravity causes or is (depending on how you look at it) curvature of space so the light goes "straight" but doesnt leave. Sorry if that means it "curves away" bu

Gravity causes or is (depending on how you look at it) curvature of space so the light goes "straight" but doesnt leave. Sorry if that means it "curves away" but that's what having an escape velocity greater than the speed of light means. And what does that have to do with conservaton of momentum? If i throw a rock upwards it curves away rather than leaving the solar system — momentum is still conserved and the rock has much more than a photon.

ars 14y ago
The object can not suddenly switch from moving straight to a curve. That's what I mean. In order to curve something must cause it to do so, but there are no lateral forces on it (or more accurately the forces in all directions are exactly balanced).
- jbri 14y ago
  It is still moving in a straight line. Large amounts of gravity tend to distort spacetime, such that a "straight line" appears bent to a distant observer. It's the same phenomenon as what causes gravitational lensing.
  - ars 14y ago
    Gravity curvature works fine at ordinary masses too. Take a rock, throw it directly away from the earth. It's not moving in a curved line, it's moving straight - from the POV of a distant observer as well. In order to curve it must have some lateral motion relative to "down".
    - gruturo 14y ago
      Different effect. A rock is actually following a curved trajectory through ordinary space. Light always goes straight - but in these extreme circumstances space itself is curved. You can easily verify this by looking at said curving rock: the fact that you can see it without distortions (or at all) implies that its region of space has insignificant curvature and the light from the event is reaching your eyes is an easy indication of it. Ordinary masses bend space nowhere nearly enough. The Sun bends space just barely enough for the effect to be observable in a solar eclipse (it was used as a verification of Einstein's theories) by causing stars behind it to appear ever so slightly out of place when its disc is just about to overlap them. The light from these stars is NOT being bent - it keeps going in a straight line, but the Sun's gravity slightly alters the very idea of straight in its immediate vicinity. The effect is a tiny distorsion, about 0.00048 degrees. And the Sun is not exactly small.... but it's not dense enough to have a strong effect. Nothing in our everyday experience is. If you could stuff all of its mass into a tiny volume then in its immediate vicinity you could experience this.

ars 14y ago

The object can not suddenly switch from moving straight to a curve. That's what I mean. In order to curve something must cause it to do so, but there are no lateral forces on it (or more accurately the forces in all directions are exactly balanced).

jbri 14y ago
It is still moving in a straight line. Large amounts of gravity tend to distort spacetime, such that a "straight line" appears bent to a distant observer. It's the same phenomenon as what causes gravitational lensing.
- ars 14y ago
  Gravity curvature works fine at ordinary masses too. Take a rock, throw it directly away from the earth. It's not moving in a curved line, it's moving straight - from the POV of a distant observer as well. In order to curve it must have some lateral motion relative to "down".
  - gruturo 14y ago
    Different effect. A rock is actually following a curved trajectory through ordinary space. Light always goes straight - but in these extreme circumstances space itself is curved. You can easily verify this by looking at said curving rock: the fact that you can see it without distortions (or at all) implies that its region of space has insignificant curvature and the light from the event is reaching your eyes is an easy indication of it. Ordinary masses bend space nowhere nearly enough. The Sun bends space just barely enough for the effect to be observable in a solar eclipse (it was used as a verification of Einstein's theories) by causing stars behind it to appear ever so slightly out of place when its disc is just about to overlap them. The light from these stars is NOT being bent - it keeps going in a straight line, but the Sun's gravity slightly alters the very idea of straight in its immediate vicinity. The effect is a tiny distorsion, about 0.00048 degrees. And the Sun is not exactly small.... but it's not dense enough to have a strong effect. Nothing in our everyday experience is. If you could stuff all of its mass into a tiny volume then in its immediate vicinity you could experience this.