1
vote
1answer
97 views

Vacuum to hold an object

How can i check and calculate if a certain vacuum pump can hold an object that weights X kg? By "hold" I mean not let that object fall to the floor due to gravity
0
votes
1answer
205 views

How could vacuum energy cause the expansion of the universe? [duplicate]

Is it by gravity? How could gravity produce a repulsive force?
2
votes
2answers
335 views

Speed of light in a vacuum

I see many references to the speed of light in a vacuum implying that it is only truly a constant measurement in a vacuum. I can live with that, but what kind of vacuum? Are we still talking about ...
4
votes
3answers
580 views

Vacuum and repulsive gravity

How can one show from General Relativity that gravity is attractive force, and under which conditions it becomes repulsive, also why positive energy vacuum drives repulsive gravity?