Du kan teoretiskt ... men elden är fortfarande varm.
Från Mrs Weasley ger Herr Diggory lite rostat bröd (citerade i ett annat svar men upprepade här för att läsa avläsning) kan vi se att huvudet i eldstaden har en fysisk närvaro.
"Never mind, Amos,” said Mrs Weasley. “Sure you won’t have a bit of toast or anything before you go?”
“Oh go on, then,” said Mr Diggory.
Mrs Weasley took a piece of buttered toast from a stack on the kitchen table, put it into the fire tongs, and transferred it into Mr Diggory’s mouth.
“Fanks,” he said in a muffled voice, and then, with a small pop, vanished.
– Harry Potter and the Goblet of Fire, Chapter 11 (Aboard the Hogwarts Express)
Men elden runt huvudet i eldstaden var fortfarande varm. Crookshanks försökte komma nära Sirius men kunde inte på grund av värmen från elden.
“Sirius!’ he said. Harry whipped round. Sirius’s untidy dark head was sitting in the fire again.
‘Hi,’ he said, grinning.
‘Hi,’ chorused Harry, Ron and Hermione, all three kneeling down on the hearthrug. Crookshanks purred loudly and approached the fire, trying, despite the heat, to put his face close to Sirius’s.” - Harry Potter and the Order of the Phoenix, Chapter 17 (Educational Decree Number Twenty-four)
Så huvudet har en fysisk närvaro, men människor kan inte bara nå ut och röra på det - de kommer att brinna.
Umbridge troligtvis transporterade bara hennes hand med Floo Powder.
När Umbridges hand kom genom eldstaden, verkar det mest logiskt att hon gjorde det genom att nå in i en Floo Powder-eld och transporterade bara sin hand över Floo Network, liknande hur människor kan stanna där de är och bara transporterar sina huvuden .‘Number twelve, Grimmauld Place!’ Harry said loudly and clearly. It was one of the most curious sensations he had ever experienced. He had travelled by Floo powder before, of course, but then it had been his entire body that had spun around and around in the flames through the network of wizarding fireplaces that stretched over the country. This time, his knees remained firm upon the cold floor of Umbridge's office, and only his head hurtled through the emerald fire …
- Harry Potter and the Order of the Phoenix, Chapter 29 (Careers Advice)
Från vad vi ser hur Floo-transport fungerar, verkar det troligt att Umbridge fastnade sin hand i eldstaden och transporterade den ensam.
“Hermione gave a horrified gasp and leapt to her feet, still staring at the fire.
A hand had appeared amongst the flames, groping as though to catch hold of something; a stubby, short-fingered hand covered in ugly old-fashioned rings.
The three of them ran for it. At the door of the boys’ dormitory Harry looked back. Umbridge’s hand was still making snatching movements amongst the flames, as though she knew exactly where Sirius’s hair had been moments before and was determined to seize it.”
- Harry Potter and the Order of the Phoenix, Chapter 17 (Educational Decree Number Twenty-four)
Hon kunde förmodligen ha dragit Sirius genom Floo Network.
Det verkar troligt att om hon hade kunnat ta tag i Sirius (hennes hand var i en Floo-eld och inte en het) skulle hon kunna dra resten av honom genom Floo Network genom att hans huvud.