How were the three planets orbiting the millisecond pulsar found?
What will be an ideal response?
Slight variations in the period of the rapidly-spinning pulsar over a long span of time showed the Doppler effect of each of the planets as they orbited their pulsar.
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Which one of the following lists is a correct representation of electromagnetic waves from longer wavelength to shorter wavelength?
A) radio waves, microwaves, infrared, visible, UV, X-rays, gamma rays B) radio waves, UV, X-rays, microwaves, infrared, visible, gamma rays C) radio waves, infrared, microwaves, UV, visible, X-rays, gamma rays D) radio waves, microwaves, visible, X-rays, infrared, UV, gamma rays E) radio waves, infrared, X-rays, microwaves, UV, visible, gamma rays
The following four forces act on a 4.00 kg object: 1 = 300 N east 2 = 700 N north 3 = 500 N west 4 = 600 N south What is the acceleration of the object?
A) 224 N in a direction 63.4° north of west B) 300 N in a direction 63.4° north of west C) 300 N in a direction 26.6° north of west D) 224 N in a direction 26.6° north of west E) 2100 N in a direction 26.6° north of west
Why do stars have dark lines in their spectra?
A. They simply don't emit light at certain wavelengths. B. The cooler atoms in their surface layers absorb the radiation at some wavelengths. C. Magnetic fields in Earth's atmosphere absorb the radiation at some wavelengths. D. The statement is false. Stars have bright emission lines in their spectra, but no absorption lines.
Why is the cosmic microwave background (CMB) so cold if the early Universe was so hot?
a. Enough time has passed for matter in the universe to release enough heat to cool down. b. The CMB constantly interacts with atoms, which effectively cool down the photons. c. The expansion of the Universe has redshifted those photons to an effectively cooler temperature. d. Misleading; The big bang was initially hot but the CMB was released from cold material much later on.