Well, he was as comprehensive as one can be in 140-character tweets—the dude obviously has more important science-ey shit to do.
First, he took a look at wingspans. They were deemed "sensibly large" based on the load they'd have to carry, unlike the "aerodynamically useless" wings of Renaissance-era Cherubs.
After giving them a pass in physics depatment, he looked at the magnificent reptilian creatures from the standpoint of evolutionary biology.
He also weighed in on the ice dragon's blue-hued breath, which he estimated to be "at least a factor of 3X hotter than RedDragon breath."
In deGrasse's expert opinion, much of GoT's dragon depictions are scientifically sound. He did, however, take issue with manner in which wights' pulled a dragon out of a lake.
"Chains need to be straight, and not curve over hill and dale," he tweeted. Nerd alert!
Some people just have to ruin everything.