1)I know that DE Broglie Hypothesis is based on the symmetry of nature. If the light has dual behaviour, then matter also has dual behaviour(wave and particle both). So, I used this symmetry to hypothesise that when it comes to fundamental forces of nature, they boil down to weak and strong pairs.
For example: 1)Electricity(strong) and Magnetism(Weak)
2)Weak Nuclear Force and Strong Nuclear force
Hence, it should imply that gravity also must be of two types: Weak gravity and strong gravity.
2)We know that charges are of two types, positive and negative. So mass should also be both positive and negative by symmetry. Positive mass would be Ordinary mass having an Attractive gravitational force. And Negative mass would be Dark matter( which is very little understood ) and its Corresponding energy be the dark energy(also negative By E=mc^2 as m is negative). This dark matter will have opposite gravitational force, that is, repulsive forces. And this explains why the universe is expanding with increasing acceleration observed by the redshift of light. And the same quantity of Positive ordinary mass and negative dark matter will add to zero as two equal and opposite charges add up to zero.