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How do you distinguish direct as opposed to indirect? I mean, to me it directly observes something which is matter and non-luminous - and satisfies the technica
by ailideex 7y ago
How do you distinguish direct as opposed to indirect? I mean, to me it directly observes something which is matter and non-luminous - and satisfies the technical definition of dark matter.
- rpedela 7y agoRotation and velocity hint that something is amiss but doesn't directly measure dark matter. Gravitational lensing is a direct measurement of matter but doesn't tell us much about its composition. If using the most general definition of "dark matter", lensing would be a direct measurement. But if "dark matter" implies non-baryonic matter, the leading hypothesis, then gravitational lensing is indirect because it is hinting something is amiss just like the rotation and velocity evidence. Now if there was a predictive theory of non-baryonic matter and that predicted gravitational lensing with specific characteristics, that would be direct evidence. Just like GR predicted black holes and we searched and found them.