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Good layman question!

The JWST will be less sensitive to more bluish wavelengths than the HST, however, it will be much more sensitive to reddish and infrared wavelengths. Now, the light of the most distant objects is significantly redshifted. So, while all galaxies are the brightest in or near the band of visible light, the light of the furthest-away galaxies was released so long ago and redshifted so much until it gets into our telescopes that these galaxies can be best detected in the near infrared.

As for redshift: this is usually explained for laymen in terms of the Doppler effect (e.g. the lower pitch of the noise of receding trains), but for cosmological redshift, that is less helpful. That the Universe expands should be understood as space itself expanding -- thus, a wave of light travelling across it is stretched, too. That means that the wavelength of the wave of light is increased. Red light has longer wavelength than blue light, hence it's called redshift.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jan 24th, 2010 at 06:15:01 AM EST
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Thanks DoDo, makes sense to me. :-)
by Fran on Sun Jan 24th, 2010 at 11:55:02 AM EST
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