The animation below illustrates how gravitational waves are emitted by two neutron stars as they first orbit each other and then coalesce. Though gravitational waves were predicted to exist in 1916, actual proof of their existence wouldn't arrive until 1974, 20 years after Einstein's death.
Uroabdomen can result from various causes, but the most common is related to trauma. Damage to the kidney, ureter, bladder, or urethra may cause urine to leak into the abdomen. Some common forms of trauma that can result in a disruption of the urinary tract in cats include:
Ureters carry urine from the kidneys to the bladder, and the bladder empties through the urethra. In the female, the bladder lies against the uterus and vagina; and in the male, against the rectum. The bladder has a moist mucosal inner lining that resists absorption, so the bladder doesn't leak urine.