I think there is negative mass in the universe. Like negative charge. The difference between charges and mass being that Like charges repel but like masses attract. Unlike masses(opposite signs ) repel. Positive mass and negative mass annihilate when they collide, just like charges.
When the Universe was created, Positive and negative mases repelled and got seperated. negative mass in a cluster of Positive mass got annihilated. thats the reason why we dont observe any negative mass around us
What do you think about this theory? Any comment for/against it are welcome.