Problema da principiante importando librerie

Ciao a tutti, sono novello di Python e stavo cercando di inserire un po' di librerie esterne per fare le prime prove. Purtroppo, dopo aver installato scipy e matplotlib quando importo ottengo la seguente sequenza di errori:

>>> import matplotlib

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    import matplotlib
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 156, in <module>
    from matplotlib.cbook import is_string_like
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/cbook.py", line 28, in <module>
    import numpy as np
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/__init__.py", line 137, in <module>
    import add_newdocs
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/add_newdocs.py", line 9, in <module>
    from numpy.lib import add_newdoc
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/lib/__init__.py", line 4, in <module>
    from type_check import *
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/lib/type_check.py", line 8, in <module>
    import numpy.core.numeric as _nx
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/core/__init__.py", line 5, in <module>
    import multiarray
ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/core/multiarray.so, 2): no suitable image found.  Did find:
	/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/core/multiarray.so: no matching architecture in universal wrapper
>>> 

per entrambe le librerie.
Qualcuno sa darmi una spiegazione sul significato di tutto quello e un aiuto?