how many times is the observable universe larger than the local group
Observable universe
Caution is required in describing structures on a cosmic scale because things are often different from how they appear . Gravitational lensing ( bending of light by gravitation ) can make an image appear to originate in a different direction from its real source . This is caused when foreground objects ( such as galaxies ) curve surrounding spacetime ( as predicted by general relativity ) , and deflect passing light rays . Rather usefully , strong gravitational lensing can sometimes magnify distant galaxies , making them easier to detect . Weak lensing ( gravitational shear ) by the intervening universe in general also subtly changes the observed large - scale structure . As of 2004 , measurements of this subtle shear showed considerable promise as a test of cosmological models .
Caution is required in describing structures on a cosmic scale because things are often different from how they appear . Gravitational lensing ( bending of light by gravitation ) can make an image appear to originate in a different direction from its real source . This is caused when foreground objects ( such as galaxies ) curve surrounding spacetime ( as predicted by general relativity ) , and deflect passing light rays . Rather usefully , strong gravitational lensing can sometimes magnify distant galaxies , making them easier to detect . Weak lensing ( gravitational shear ) by the intervening universe in general also subtly changes the observed large - scale structure . As of 2004 , measurements of this subtle shear showed considerable promise as a test of cosmological models .