Sizes of things

Cells

• 10¹⁴ (100 trillion) cells in the Human body
• A typical cell size is 10μm, (0.01mm) some pollen is a bit smaller than that but is made of several cells. The cell membrane (wall) is about 10nm thick for animals cells.
• The cell nucleus is 11-22μm and is typically about 10% of the total volume, so the cell would have to be about 50-100μm. Typical mammalian cell nucleaus has 3000-4000 pores of 100nm diameter.
• Animal cells are on the borderline of visibility, they can be seen but only as a spec of dust.

E-coli single-cell organisms

Human cell with nucleus, about 30,000 atoms in diameter, the pores are about 200 atoms diameter, the ribosomes about twice that

Planets and stars

Atoms

• The Angstrom is 0.1nm and is roughly the size of a typical atom (0.5A for Hydrogen to 3.8A for Uranium).
• The distance between carbon atoms in β sheets in enzymes etc is roughly 5A (0.5nm).
• This would make the cell nucleus in the region of 30,000 atoms diameter, and the animal cell 150,000 atoms.
• The pores on the nucleus would have about 600 atoms around their opening.

Astronomy learning resources

• Astronomy Lesson Plans
• Educational and Fun Astronomy Games
• Planets for Kids: Solar System Facts and Astronomy
• Space Exploration Insights & Resources
• Exploratorium - Eclipse Links and Resources
• Astronomy Resource Bank

See also

• Physics
• http://learn.genetics.utah.edu/content/begin/cells/scale - excellent simulation with sliding scale
• http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10
• http://www.mpibpc.mpg.de/groups/de_groot/presentations/Madrid2003/aqp1_system_movie.html - this is an unbelievable simulation of how water molecules are transmitted thru a membrane. this clip actually happens in 10 ns!
• Scale of the universe with pictures and words
• The Scale of the Universe 2