Magnetic levitation experiment set up. A) Photo of the water-cooled duplex-Bitter magnet located at HFML with our samples placed inside (not visible). The samples are positioned inside the magnet bore. The temperature is controlled by a double-walled metal tube connected to a 22°C water bath. A PVC spacer is used to place the stack of samples in the correct position. B) The samples are contained in 40.8 mm high tubes placed on top of each other at five effective g* levels. The spacing between the samples was 40.8 mm and all samples were in the dark before and during the experiment (no light reached the magnet bore). C) Closer view of a sample tube. Callus cell culture is grown in a 1-2 mm layer to ensure a similar force throughout the whole biological sample. D) Profile of the magnetic field strength (B) and the effective gravity (g*) as a function of position inside the magnet. The samples were placed symmetrically in relation to the centre of the bore (195 mm above the top) indicated in the graph by vertical lines (straight lines for μg*, 1 g* and 2 g* and dotted lines for intermediate 0.1 g* and 1.9 g*). The red curve shows the magnetic field strength as a function of the vertical position (z) in the magnet. The blue curve indicates the product of the field strength B(z) and the field gradient (B' (z) = dB/dz), which is the derivative of the field strength with respect to the vertical position. The corresponding value of the effective gravity is equal to g(1 + B(z) B' (z)/1360), so a magnetic force of -1360 T2/m is able to levitate water.