"Antigravity is impossible" I'm sorry but that is a very narrowminded statement. I can't go into all that scientific equation crap to prove you wrong, but.
We have and understand this technology and use it, and many other advanced energy and propulsion technologies. However it is being kept secret from the public to protect the oil, gas, coal, public utility and nuclear power industries, in which is VERY profitable.
http://www.seaspower.com/EnergyDisclosureDec122003.htm
http://www.disclosureproject.com/
Anti-gravity propulsion is the main technology to achieve instellar travel used by 'ET's'. Thousands of times faster than the speed of light. I have no idea how it works, becuase, well, it's being kept secret.
Now I can already tell some people are gonna post with another narrowminded statement, "ET's are not real you gullible half-wit" pfft prove it. Being too conservative won't get you anywhere, even if you are an Einstein.
Flame away...